Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

Country：Japan

Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

Country：Japan

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electrical Engineers of Japan  

<p>This paper introduces a practical approach for transformer design optimization using a novel hybrid Dowell artificial neural network (HDANN) model. This model is a highly efficient and accurate method to estimate leakage inductance, which is an important parameter that affects the performance of transformers and power converters. The model combines the conventional hybrid Dowell’s model, which uses analytical equations, and an artificial neural network, which uses machine learning techniques. It is integrated into an optimization program to optimize the design of a transformer in terms of its size and loss. We investigated the HDANN design scope by testing various transformer conditions. The results provided an in depth understanding of the capabilities and limitations of the HDANN model for transformer design. By understanding the HDANN design scope, the optimization program was implemented in a multidomain circuit simulation, which includes electric and magnetic circuits. This allows a high-speed co-simulation using the optimized transformer design that considers the geometry and material characteristics for the desired circuit specification. It showed that the HDANN offers significant advantages over existing design optimization methods, including improved ease of application, accuracy, and efficiency. The effectiveness of the optimization using the HDANN with the defined geometric parameters was demonstrated by the circuit analysis results of a phase-shift full-bridge converter. Summarizing, the proposed method can potentially revolutionize how transformers are designed and implemented for various applications, leading to increased design reliability as well as reduced power loss and size.</p>

DOI： 10.1541/ieejjia.23009691

CiNii Research

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electrical Engineers of Japan  

<p>By applying an unregulated LLC resonant converter to a multi-input modular DC-DC converter (MIMC), the LLC converter can be operated at an optimal frequency while achieving power source flexibility. However, the output characteristics of an LLC converter are easily affected by the resonance parameter, and when connected in parallel, the output current is unbalanced. In this paper, we propose a current sharing control method to solve the current imbalance problem, and automatically balance the output current of each module. The effectiveness of the proposed current sharing control method is verified by simulations and experiments.</p>

DOI： 10.1541/ieejias.143.337

Scopus

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electrical Engineers of Japan  

<p>A multiphase DC-DC converter consisting of a coupled inductor and fast switching devices enables power electronics equipment to achieve a high power density. However, with such devices, the fast voltage transition generates substantial common mode (CM) noise. However, there are very few studies on CM noise reduction for multiphase converters using a coupled inductor. Therefore, in this paper, a CM noise reduction method is proposed for a multiphase DC-DC converter that hardly lowers the power density.</p>

DOI： 10.1541/ieejias.143.263

Scopus

CiNii Research

Authorship：Corresponding author   Language：Japanese  

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：電気学会論文誌D  

Authorship：Corresponding author   Language：English  

Authorship：Corresponding author   Language：English  

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electrical Engineers of Japan  

<p>This paper proposes a novel method for measuring the characteristics of a wireless power receiver of an electric field wireless power transfer (eWPT) system. The proposed measurement method allows us to obtain the frequency response of the eWPT receiver's power-receiving characteristics with respect to the spatial electric field frequency. Conventionally, it was not possible to measure the reception characteristics of a single independent receiver. This is because a resonant eWPT transmitter has pronounced frequency dependent characteristics. As a result, frequency-dependent electric fields are emitted into space and act on the receiver. The proposed measurement method overcomes this obstacle by using the proposed device that generates a high-frequency electric field almost independently of the frequency. The proposed device generates high-frequency electric fields in space by using a terminating resistor instead of resonator circuits. Therefore, unlike resonant transmitters, the strength of the electric field generated by the proposed device does not exhibit a large frequency dependence. The proposed measurement method will also be useful for the prototyping, evaluation, and optimization of new advanced eWPT systems whose characteristics are not yet fully understood. Here, 85kHz series resonant eWPT receivers are evaluated using the proposed measurement method, and the details of this experimental device are also described.</p>

DOI： 10.1541/ieejjia.22004096

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CiNii Research

Authorship：Last author   Language：English   Publisher：The Institute of Electrical Engineers of Japan  

<p>This study proposes strategies for improving the accuracy and usefulness of leakage inductance modeling using the Dowell model (DM). As the analytical method of modeling the leakage inductance model considers geometrical factors, it is vital for front-loading transformer design. DM is one such widely used one-dimensional magnetic field-based approach for analytically modeling both AC resistance and leakage inductance. It is more accurate and requires less computational work than other analytical approaches proposed in previous studies. However, some approximations may cause errors and eventually lead to inaccurate results. Therefore, this study aims to ascertain the conditions that result in inaccurate leakage inductance modeling. Additionally, a simple exponential-based model and an artificial neural network are developed to increase the accuracy of inaccurate modeling. The results clarify the conditions that result in a frequency-dependent and bias error. Moreover, the intended findings indicate that the proposed strategies effectively improve modeling accuracy while simultaneously providing some extra advantages for transformer design.</p>

DOI： 10.1541/ieejjia.22007452

CiNii Research

Authorship：Corresponding author   Language：English   Publisher：The Institute of Electrical Engineers of Japan  

<p>This paper presents an interleaved boost converter with integrated magnetics for common-mode (CM) noise reduction without introducing electromagnetic interference (EMI) filters. The noise reduction is realized using the balanced technique, which is an effective CM noise reduction technique from a circuit topology perspective. The application of this technique addresses the issue of the CM noise, while avoiding an increase in circuit volume due to EMI filters. Additionally, an interleaved circuit topology and integrated magnetics contribute to realizing the high-power density converter. The effectiveness of the proposed converter is discussed through theoretical analyses, simulations, and experiments.</p>

DOI： 10.1541/ieejjia.22007783

CiNii Research

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：2023 IEEE Energy Conversion Congress and Exposition, ECCE 2023  

This study introduces a novel voltage-controlled variable inductor (VI) that effectively fixes the switching frequency of DC-DC converters operating in the critical conduction mode (CRM). The proposed VI addresses the limitations encountered with conventional current-controlled VIs, such as complex winding structures, control challenges, and reliance on magnetic saturation. In the proposed voltage-controlled VI, the primary-side inductance of a coupled inductor is regulated by an auxiliary voltage source on the secondary side. The validity of the proposed VI is experimentally verified using a prototype CRM boost converter with an output voltage of 400 V. Experimental results demonstrate that the switching frequency remains fixed at 100 kHz, and the main converter maintains soft switching characteristics regardless of variations in output power.

DOI： 10.1109/ECCE53617.2023.10362859

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ICPE 2023-ECCE Asia - 11th International Conference on Power Electronics - ECCE Asia: Green World with Power Electronics  

An equivalent circuit model of lithium-ion batteries which has a nonlinear resistor governed by Butler-Volmer's equation and a constant phase element was investigated. The current dependence of the real battery could be reproduced well by the contribution of the nonlinear resistor, and the transient response of voltage could be reproduced well by the contribution of the constant phase element.

DOI： 10.23919/ICPE2023-ECCEAsia54778.2023.10213775

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electrical Engineers of Japan  

<p>This study investigates the influence of parasitic capacitance on the common mode (CM) noise in a converter. A thermal pad on a switching device is necessary for sufficient heat dissipation. In addition, the thermal pad increases the CM capacitance between the printed circuit board and the ground plane. The parasitic capacitances form CM noise propagation paths. However, which node in the circuit and the corresponding parasitic capacitance influences the CM noise the most and the degree of the parasitic capacitance influence on the CM noise are unclear. In this study, the parasitic capacitance that influences the CM noise in a converter is identified, and the extent to which the parasitic capacitance affects the CM noise is investigated through simulations and experiments.</p>

DOI： 10.1541/ieejjia.22008018

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CiNii Research

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ICPE 2023-ECCE Asia - 11th International Conference on Power Electronics - ECCE Asia: Green World with Power Electronics  

This paper presents a transformer-less inverter topology that brings out the high-performance for grid connected inverters. The main advantages of this inverter eliminate the dead-time requirement, and allows both top and bottom switch from being on at same time, and thus shorting the DC bus supply to ground. This avoids the freewheeling diodes connected across the switches for loads other than purely resistive. Low output voltage distortion and low fundamental and common voltages losses result in high efficiency and high output power density. The input dc source and the output ac voltage share the same ground in proposed inverter, which effectively eliminates the leakage current caused by the DC source (PV panel, battery bank etc.). Analysis and simulation results are presented to demonstrate the effectiveness of the proposed inverter. Compared to the prior literature mentioned in this paper, 75- 86% reduction of semiconductor components is achieved with proposed inverter topology.

DOI： 10.23919/ICPE2023-ECCEAsia54778.2023.10213921

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Access  

A GaN gate injection transistor (GIT) has great potential as a power semiconductor device. However, a GaN GIT has a diode characteristic at the gate-source, and a corresponding gate drive circuit is thus required. Several studies in the literature have proposed the gate drive circuits with the speed-up capacitors, but adding these capacitors complicates the gate drive circuit, and increases both the drive and reverse conduction losses. Moreover, driving a GaN GIT with such gate drive circuits becomes more susceptible to the false turn-on. In this paper, a gate drive circuit suitable for a GaN GIT without a speed-up capacitor is proposed. This type can provide the high-speed switching, and exhibit the low gate drive loss and reverse conduction loss. The proposed circuit also has high immunity against the false turn-on and stable gate-source voltage before and after startup. The drive loss of the proposed type is calculated and its validity is confirmed experimentally. Furthermore, the drive loss of the proposed type is compared with the conventional circuits. The result shows that the drive loss of the proposed type is improved by up to 50 %, compared with the conventional type. Finally, the proposed type is experimentally tested to drive a buck converter at the switching frequency of 150 kHz. The entire loss of the converter can be reduced by up to 9.2% at 250 W, compared with the conventional type.

DOI： 10.1109/ACCESS.2023.3270261

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

Other Link： https://www.jstage.jst.go.jp/article/elex/20/21/20_20.20230351/_article/-char/en

Authorship：Last author   Language：English   Publishing type：Research paper (other academic)  

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (other academic)   Publisher：THE INSTITUTE OF SYSTEMS, CONTROL AND INFORMATION ENGINEERS  

DOI： 10.11509/isciesci.66.12_457

CiNii Research

Authorship：Corresponding author   Language：Japanese   Publisher：The Japan Institute of Electronics Packaging  

DOI： 10.5104/jiep.25.527

Scopus

CiNii Research

Authorship：Last author   Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

<p>This paper proposes a topology of high power, MHz-frequency, half-bridge resonant inverter ideal for low-loss Gallium Nitride high electron mobility transistor (GaN-HEMT). General GaN-HEMTs have drawback of low drain-source breakdown voltage. This property has prevented conventional high-frequency series resonant inverters from delivering high power to high resistance loads such as 50Ω, which is typically used in radio frequency (RF) systems. High resistance load causes hard-switching also and reduction of power efficiency. The proposed topology overcomes these difficulties by utilizing a proposed ‘L-S network’. This network is effective combination of a simple impedance converter and a series resonator. The proposed topology provides not only high power for high resistance load but also arbitrary design of output wattage depending on impedance conversion design. In addition, the current through the series resonator is low in the L-S network. Hence, this series resonator can be designed specifically for harmonic suppression with relatively high quality-factor and zero reactance. Low-distortion sinusoidal 3kW output is verified in the proposed inverter at 13.56MHz by computer simulations. Further, 99.4% high efficiency is achieved in the power circuit in 471W experimental prototype.</p>

DOI： 10.1587/transele.2021ECP5048

Web of Science

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CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electrical Engineers of Japan  

<p>This study provides a circuit analysis model of a DC brush motor to predict spike surges at mechanical contacts and conducted EMI by considering the behavior of steady arc discharge. The mechanical contacts model comprises multiple variable resistors, constant voltage sources, ideal diodes, and stray capacitances. In the proposed model, spike surges with steady arc could be predicted with 90% accuracy. Moreover, simulated conducted EMI according to CISPR 25 standard is deviated from the measured value at a maximum of 25dB. Therefore, it is demonstrated that the quantitative prediction of conducted EMI requires consideration of a showering arc model at mechanical contacts.</p>

DOI： 10.1541/ieejias.142.490

Scopus

CiNii Research

Authorship：Corresponding author   Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

<p>In response to fast charging systems, Silicon Carbide (SiC) power semiconductor devices are of great interest of the automotive power electronics applications as the next generation of fast charging systems require high voltage batteries. For high voltage battery EVs (Electric Vehicles) over 800V, SiC power semiconductor devices are suitable for 3-phase inverters, battery chargers, and isolated DC-DC converters due to their high voltage rating and high efficiency performance. However, SiC-MOSFETs have two characteristics that interfere with high-speed switching and high efficiency performance operations for SiC MOS-FET applications in automotive power electronics systems. One characteristic is the low voltage rating of the gate-source terminal, and the other is the large internal gate-resistance of SiC MOS-FET. The purpose of this work was to evaluate a proposed hybrid gate drive circuit that could ignore the internal gate-resistance and maintain the gate-source terminal stability of the SiC-MOSFET applications. It has been found that the proposed hybrid gate drive circuit can achieve faster and lower loss switching performance than conventional gate drive circuits by using the current source gate drive characteristics. In addition, the proposed gate drive circuit can use the voltage source gate drive characteristics to protect the gate-source terminals despite the low voltage rating of the SiC MOS-FET gate-source terminals.</p>

DOI： 10.1587/transfun.2021GCI0001

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electrical Engineers of Japan  

<p>This paper presents a circuit analysis model to predict spike surges at mechanical contacts of a DC brush motor. Measured spike surge waveforms are classified into four types depending on the existence of a steady arc and a showering arc. The directly open without arcs condition is clarified to be the maximum spike surge voltage condition. Additionally, an equivalent circuit model is developed to simulate spike surges. This model considers complex high-frequency characteristics and rotation angle dependence of impedances. A full-slot equivalent circuit model is represented by a combination of single-slot models. The spike surge simulation model considers induced voltage and variable resistors representing mechanical contact switching in addition to impedance characteristics. The simulated spike surges show good quantitative agreement with the measured values.</p>

DOI： 10.1541/ieejias.142.167

Scopus

CiNii Research

Authorship：Corresponding author   Language：English   Publisher：IET Power Electronics  

In applications where DC current is superimposed, such as inductors for non-isolated DC-DC converters, powder core can be considered as an attractive solution owing to its superior features such as: high saturation flux density, high Curie temperature, and soft-saturation property. However, in powder cores, a drop of inductance appears prominently due to DC superimposition characteristics. This feature is not a desirable characteristic because it leads to an increase in the inductor ripple current under heavy load, which complicates the thermal design of power semiconductors and capacitors. This paper verifies the improvement of DC superimposition characteristics of powder cores by applying coupled inductors. First, the effect of coupled inductors on the improvement of DC superimposition characteristics is experimentally verified. Second, a measurement method for the DC superimposition characteristics of coupled inductor is proposed. Then, a magnetic circuit model is built using the measurement results. Finally, a coupled analysis of magnetic and electric circuits is performed, and it is confirmed that lower magnetic field operation can be realized by coupled inductors even under heavy load conditions. It has been proven that coupled inductors are effective in improving the DC superposition characteristics of the powder cores.

DOI： 10.1049/pel2.12226

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Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Journal of Emerging and Selected Topics in Power Electronics  

In megahertz (MHz) power converters, the gate drive loss becomes one of the main issues that should be addressed. In the relevant literature, several gate drive circuits had been proposed to reduce the gate drive losses. A literature survey is provided in the introduction section to summarize the merits and demerits of each circuit. These studies proposed innovative methods to reduce gate drive loss. Nonetheless, they did not propose any solution to reduce the loss of the buffer stage inside the drive IC. In this article, we present a frequency doubler gate drive circuit. The proposed gate drive circuit can double the frequency of the input PWM signal at the driver output stage, using the second harmonic of the input signal. Therefore, the loss of the buffer stage inside the drive IC can be significantly reduced, compared with the hard-switching, the inductive resonant, and multiresonant gate drive circuits. This article focuses on designing, simulating, and experimentally validating the frequency doubler gate drive circuit with a 6.78-MHz input frequency and 13.56-MHz driving frequency. The concept of a frequency tripler gate drive circuit is also introduced and discussed. For instance, the frequency tripler gate drive circuit can triple the frequency of the input PWM signal at the driver output stage using the third harmonic; in this scenario, a 20.34-MHz driving frequency can be obtained. The proposed frequency doubler gate drive circuit is experimentally tested in a 13.56-MHz class E inverter.

DOI： 10.1109/JESTPE.2021.3089506

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Scopus

Authorship：Corresponding author   Language：Japanese  

Authorship：Corresponding author   Language：English  

Authorship：Last author   Language：English  

Authorship：Last author   Language：English   Publisher：The Institute of Electrical Engineers of Japan  

<p>A novel magnetic structure for use in LLC resonant converters is proposed in this paper. It is known as a Path-core type Resonant Inductance Adjustable (PRIA) transformer, which is a type of transformer with adjustable resonant inductance. In the proposed transformer, the resonant inductance and magnetizing inductance can be designed separately; therefore, it becomes less challenging to realize the required resonant frequency. Moreover, the magnetizing inductance is not affected by any variation in the resonant inductance. The proposed PRIA transformer is found to improve the efficiency of the LLC converters. In this paper, the design of a resonant inductance of a PRIA transformer is presented. In addition, the application of PRIA transformers to a 1-MHz LLC resonant converter and 1kW 1.4-MHz LLC resonant converter is presented.</p>

DOI： 10.1541/ieejjia.21002488

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CiNii Research

Authorship：Last author   Language：English   Publisher：2022 International Power Electronics Conference, IPEC-Himeji 2022-ECCE Asia  

The aim of this research is to build a highly applicable, accurate, and fast leakage inductance modeling method based on Dowell model. Which is a widely used analytical modeling method to estimate AC resistance and leakage inductance. Since most of the literatures use Dowell model basically with the limited condition achieving ac-curate modeling of leakage inductance, in this research, an accuracy investigation is conducted with the samples of EE-core transformers by finite element method (FEM) simulation and practical transformers to find the inaccurate modeling related to the geometrical characteristic. After that, a proposed hybrid modeling using artificial neural network (ANN) is conducted to create a black box error correction model of conventional Dowell model with FEM results. As the result, the modeling shows high accuracy by Dowell with ANN error correction model. It carries out the future to develop a modified Dowell model by analyzing the ANN error correction model. Which can describe the geometrical characteristic of transformer accurately.

DOI： 10.23919/IPEC-Himeji2022-ECCE53331.2022.9807009

Scopus

Authorship：Corresponding author   Language：Japanese   Publisher：2022 International Power Electronics Conference, IPEC-Himeji 2022-ECCE Asia  

High-power density and high efficiency in boost converters are required in several applications such as motor drive systems in eco-friendly vehicles and power conditioning systems used in renewable energy systems. To realize these requirements, applying compound semiconductor devices such as GaN and SiC are attractive options because they can drive at high-switching frequency with low power losses, and it is known to contribute to the miniaturization of passive devices. However, when driving power devices with high switching speed at high-switching frequency, EMI (Electro-Magnetic Interference) noise with a wide spectrum is produced. To attenuate EMI noise, large EMI filters have to be equipped. When using large EMI filters, the downsizing effect of power converters is reduced. To countermeasure the above problem, this paper proposes interleaved boost converter with integrated magnetics capable of Common-Mode (CM) noise reduction without adding EMI filters. The noise reduction is realized by the balanced technique, which is known as an effective noise reduction technique from a circuit topology perspective. In addition, interleaved circuit topology and integrated magnetics are contributed to realizing high-power density converters. The effectiveness of the proposed converters is discussed from simulation and experimental viewpoints.

DOI： 10.23919/IPEC-Himeji2022-ECCE53331.2022.9806834

Scopus

Authorship：Last author   Language：English  

Web of Science

Authorship：Last author   Language：English  

Web of Science

Authorship：Corresponding author   Language：English   Publisher：IECON Proceedings (Industrial Electronics Conference)  

This paper proposed an approach to transferring nonlinear parasitic drain-source capacitance of MOSFET to a linear model by charge-related equivalent conversion. It is applied to a previously researched analytical model of the class-D inverter to add its feasibility in high frequency. Based on the proposed approach, the relationship between maximum operation frequency, the nonlinear capacitance, and the input voltage are inferred and verified by spice simulation, resulting in good consistency.

DOI： 10.1109/IECON49645.2022.9968760

Scopus

Authorship：Corresponding author   Language：English  

Web of Science

Authorship：Corresponding author   Language：English  

Web of Science

Authorship：Last author   Language：English   Publisher：2022 International Power Electronics Conference, IPEC-Himeji 2022-ECCE Asia  

Many soft switching techniques utilize the resonance between an inductor and parasitic output capacitor of switching device. However, output capacitance has nonlinear characteristics depending on drain-source voltage which obscure the resonant period. The proposed method estimates the resonant period by linearizing output capacitance. The method can be applied to the bridge-type converter which utilizes resonance for soft switching. Simulation and experiment with a 3-kVA prototype half bridge auxiliary resonant commutated pole inverter were implemented to verify the proposed method.

DOI： 10.23919/IPEC-Himeji2022-ECCE53331.2022.9806865

Scopus

Authorship：Last author   Language：English   Publisher：The Institute of Electrical Engineers of Japan  

<p>Many soft switching techniques utilize a resonance between an inductor and parasitic output capacitors of switching devices. However, output capacitance has nonlinear characteristics, which obscures the resonant period for soft switching. In this paper, a new method is proposed to derive the resonant period by considering nonlinear characteristics of the output capacitance. The method can be applied to a bridge-type converter which utilizes resonance for soft switching. Other parasitic capacitances which affect the resonant period, are also considered. To verify the proposed method, simulations and experiments were performed with a 3-kVA prototype half bridge auxiliary resonant commutated pole inverter.</p>

DOI： 10.1541/ieejjia.22006987

CiNii Research

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：2022 IEEE Energy Conversion Congress and Exposition, ECCE 2022  

It is well-known that wide-bandgap power semiconductor devices such as GaN and SiC have attractive features such as low on-resistance and capability of high switching speed, which results in realizing high power density converters. Therefore, power converters using GaN (Gallium Nitride) or SiC (Silicon Carbide) power devices have usually high efficiency, smaller passive components can be adopted than Si-based power converters by driving the converter at high switching frequency. However, driving at high switching frequency may result in a temperature rise of magnetic components, which can be one of the critical issues due to a downsized small surface area of magnetic cores and increasing power loss density per unit volume. Therefore, this paper proposes and evaluates a low-profile magnetic structure based on split-magnetic cores and meander winding capable of high cooling performance. The effectiveness of the proposed magnetic structure used in power converters is confirmed by experimental tests.

DOI： 10.1109/ECCE50734.2022.9947805

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Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE International Symposium on Industrial Electronics  

Electric vehicles and electric aircraft are being developed for decarbonization, and their power converters need to be miniaturized. High-frequency switching of semiconductors using GaN or SiC materials is an attracting attention as one of the options to reduce the size of the inductor core. On the other hand, reducing the core size leads to an increase in core temperature. Therefore, Design methods that take heat into consideration are desired, and the use of simulation is expected. Although FEM is an accurate simulation method, it takes a lot of calculation time when used as a thermal simulation during the circuit operation for several hours. Thus, accurate core loss modeling is necessary. In this study, we used accurate FEM-based modeling to perform thermal simulation of inductors in high-frequency switching.

DOI： 10.1109/ISIE51582.2022.9831609

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Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：2022 IEEE Energy Conversion Congress and Exposition, ECCE 2022  

Concentrated air gap is utilized to suppress soft saturation characteristics of powder cores by increasing effective magnetic reluctance. This paper proposes a high-precision magnetic circuit model for powder core in coupled inductors. The proposed model, considering soft saturation and flux cancellation, can be utilized even with large air gap, and simplifies the magnetic design. The model features good accuracy of inductance variation in a wide range of winding current. Five prototype coupled inductors were built using the proposed model and applied to a 1-kW interleaved boost converter to prove the precision of the proposed magnetic circuit.

DOI： 10.1109/ECCE50734.2022.9947578

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Scopus

Authorship：Corresponding author   Language：English   Publisher：The Institute of Electrical Engineers of Japan  

<p>Path-core type resonant inductance adjustable (PRIA) transformer usage in high-frequency LLC resonant converters is proposed herein to reduce transformer losses. The proposed magnetic structure is a type of transformer with adjustable resonant inductance combined with a path core for LLC resonant converters. In the proposed transformer, the flux density of the magnetizing inductance can be reduced with a path core. Therefore, fewer core losses are generated when using the proposed transformer. Moreover, the flux of leakage inductance that can be set with the path core has been previously proven by researchers at the Nagoya University laboratory. Consequently, the coil losses, which are one of the largest components of transformer losses, can be reduced effectively by controlling the path of the leakage flux. The proposed PRIA transformer has been reported to improve the efficiency of LLC converters. In this study, a conventional transformer with a magnetic structure is compared with a PRIA transformer through experiments. The core losses were obtained through finite-element simulations, and the coil losses not generated by the magnetic structures were estimated via calculations. The advantage of reducing transformer losses in high-frequency LLC resonant converters with PRIA-structure transformers is presented in this work.</p>

DOI： 10.1541/ieejjia.21012384

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CiNii Research

Authorship：Corresponding author   Language：English   Publisher：2021 23rd European Conference on Power Electronics and Applications, EPE 2021 ECCE Europe  

Powder cores are attractive magnetic cores for high current applications such as bidirectional dc/dc converters used in power trains of eco-friendly automotive because of their high saturation flux density, high Curie temperature, and soft saturation characteristics. However, powder cores have nonlinear relative permeability characteristics dependent on the magnetic field intensity which results in a drop in the inductance value at high current values. There are two key solutions to keep constant inductance value at maximum power rating of circuit specifications: (1) inserting a concentrated airgap (2) reducing the number of turns to tackle the drop of relative permeability due to dc-bias. Therefore, this paper proposes a novel magnetic design method for powder core inductors with concentrated airgap which to keep the desired inductance constant under dc-bias conditions. The feature of the proposed design methodology is based on considering non-linear relative permeability directly based on the magnetic characteristics modeling. The validity of the proposed method is confirmed by experimental tests using EE core.

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electrical Engineers of Japan  

<p>A cooperative control scheme for a power conversion system having several energy sources and modular dc/dc converters is proposed in this paper. The proposed cooperative control approach has the advantage of realizing constant dynamic characteristics even when the different input voltages fluctuate or when the output power of each input voltage source is limited. The effectiveness of the proposed cooperative control method is verified via simulation and experiment.</p>

DOI： 10.1541/ieejias.141.304

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CiNii Research

Authorship：Last author   Language：Japanese  

The efficiency of electric field resonance wireless power transmission (WPT) is low in long distances. However, the proposed system realizes high efficiency in long distances by utilizing high-Q helical resonators. The transmission efficiency of the proposed system is increased by at most 69.4% compared with the conventional system at 27.12MHz.

DOI： 10.14923/transcomj.2020gwl0001

CiNii Research

Authorship：Last author   Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

<p>This paper reports a power loss calculation method for magnetic components in power converters. The differences in B-H loop areas are analyzed and discussed in case of sinusoidal waveform and square wave voltage excitation. Relying on the output results, iron loss calculation method based on square wave excitation is proposed. Experimental results show that the proposed iron loss calculation method is accurate compared with the traditional method using Steinmetz's equation. In addition, the proposed method reduces the calculation procedure compared with the method using Steinmetz's equation. The proposed iron loss calculation method is very practical and beneficial for converter designers.</p>

DOI： 10.1541/ieejfms.141.69

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CiNii Research

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electronics, Information and Communication Engineers  

<p>Aluminum Electrolytic Capacitors are widely used as the smoothing capacitors in power converter circuits. Recently, there are a lot of studies to detect the residual life of the smoothing Aluminum Electrolytic Capacitors from the information of the operational circuit, such as the ripple voltage and the ripple current of the smoothing capacitor. To develop this kind of technology, more precise impedance models of Aluminum Electrolytic Capacitors become desired. In the case of the low-temperature operation of the power converters, e.g., photovoltaic inverters, the impedance of the smoothing Aluminum Electrolytic Capacitor is the key to avoid the switching element failure due to the switching surge. In this paper, we introduce the impedance calculation model of Aluminum Electrolytic Capacitors, which provides accurate impedance values in wide temperature and frequency ranges.</p>

DOI： 10.1587/transele.2020ECP5009

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Scopus

CiNii Research

Authorship：Corresponding author   Language：English   Publisher：Japanese Journal of Applied Physics  

In power electronics, the impedance of reactance components increases proportionally with frequency; therefore, the sizes of reactance components can be reduced by increasing the switching frequency. Gallium nitride (GaN)-based devices have received significant attention in high-frequency applications because the figure-of-merit of GaN is superior to that of silicon (Si). However, for high-frequency operation, a trade-off relationship between the surge voltage induced by parasitic inductances, and the switching loss becomes significant. Therefore, in this study, we propose a gate driver that improves the trade-off relationship. This gate driver was obtained via the addition of simple logic circuits and capacitors to a conventional gate driver. The effectiveness of our proposed circuit was verified via SPICE simulations with Cadence Spectre using 180 nm CMOS technology. The simulation results show that by operating at 1 MHz, this circuit can help reduce the surge voltage by 12.2% and the switching loss by 14.3%.

DOI： 10.35848/1347-4065/abbdc7

Scopus

Authorship：Corresponding author   Language：English   Publisher：The Institute of Electrical Engineers of Japan  

<p>This paper presents a bidirectional converter with multi-stage FETs featuring voltage balance control function using variable capacitors. The proposed converter is constructed using low-voltage Si-FETs in a series connection, and it improves the voltage balance between the drain-source voltages of the series connected FETs in the OFF period. Using the converter figure of merit (FOM), which can estimate the converter losses from the specifications of the FETs, the effectiveness of the proposed converter is compared to that of a converter using SiC-FETs. The factors of the voltage unbalance are analytically clarified using the equivalent circuit. The principle of voltage balance control function using the variable capacitor is discussed. The experimental results show that the proposed converter can achieve a maximum power conversion efficiency of 99.2%.</p>

DOI： 10.1541/ieejjia.19003873

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CiNii Research

Authorship：Last author   Language：English   Publisher：2021 IEEE International Future Energy Electronics Conference, IFEEC 2021  

More and more wide band gap power devices are used in switching converters to achieve high power density and high efficiency. However,those devices increase electromagnetic interference (EMI),especially common mode (CM) noise propagates through parasitic capacitance. A noise filter is a popular way to decrease EMI. But a filter decreases the power density of the converter because of the bulk components. Therefore,a noise reduction method with small increase in volume and weight is necessary. In this paper,a novel but simple circuit configuration for high power application to reduce CM noise is investigated in simulation and experiment.

DOI： 10.1109/IFEEC53238.2021.9662002

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Scopus

Language：Japanese   Publisher：IEEE International Symposium on Industrial Electronics  

Recently wireless power transfer systems via resonant magnetic coupling (MRC-WPT) is the promising wireless power supply method to mobile applications. 13.56MHz highly resonant wireless power receivers experience high rectifier losses when using Schottky diodes and can fail to meet the thermal limit requirements for many products such as laptops. Therefore, the synchronous rectification is one of the effective solutions. However, the increased occupancy of the control signal propagation delay in switching cycle, tend to make the introduction of the synchronous rectification difficult. This novel synchronous rectifier can operate under any propagation delay of gate drivers. The analysis successfully verified the operating principle and clarified the usefulness of the proposed control for MHz WPT systems.

DOI： 10.1109/ISIE45552.2021.9576180

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Language：Japanese  

Web of Science

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：2021 IEEE International Future Energy Electronics Conference, IFEEC 2021  

To operate the LLC converter at high switching frequency,the excitation current flowing through the transformer is increased,which generates a large conducted noise. The peaks in the noise spectrum are caused by the ringing of the switching node voltage and the resonance of the CM equivalent circuit. In this paper,a method using ferrite beads and additional resistors in combination with the input filter is proposed to suppress the ringing. Its effectiveness in reducing the high-frequency noise while maintaining the fast-switching speed is confirmed by simulation and experiment.

DOI： 10.1109/IFEEC53238.2021.9661804

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Scopus

Language：Japanese   Publisher：2021 IEEE Energy Conversion Congress and Exposition, ECCE 2021 - Proceedings  

Driving power devices such as GaN HEMTs at high-frequency is one of the successful solutions to miniaturize the magnetic components of circuits. On the other hand, GaN HEMTs have drawbacks in high-speed switching. For example, in a full-bridge inverter configuration, a fast turn-on of one power device can cause a false turn-on of the complementary power device. Therefore, the GaN HEMT might be destroyed by the overcurrent and transient heat caused by the short circuit. The most important factor for the false turn-on of GaN HEMTs is its reverse transfer capacitance (Crss), but other parasitic components such as inductances in PCB should be considered to analyze the false turn-on phenomena. In this paper the theoretical analysis of the capacitance components that may cause the false turn-on is conducted. Based on the theoretical analysis, we propose the conditions of the parasitic component of the gate drive circuit to prevent false turn-on.

DOI： 10.1109/ECCE47101.2021.9595846

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Language：Japanese   Publisher：2021 IEEE Energy Conversion Congress and Exposition, ECCE 2021 - Proceedings  

the objective of this research is to build the measurement method of DC superimposition of multiphase coupled inductors with powder cores. From a perspective of magnetic material, powder cores are usually applied to inductor core in high current applications such as E-mobility due to their attractive features. In addition, multiphase DC/DC converters with coupled inductors can effectively downsize passive components that occupy significant space in power converters. However, when applying coupled inductor with powder cores under the dc current superimposed condition, self-inductance and mutual inductance values of coupled inductors are varied depending on dc current values. Furthermore, measurement methods of the dc superimposition characteristics of multiphase coupled inductor have not been discussed in the relevant literature. Therefore, this paper proposes two measurement methods for DC superimposition characteristics of three-phase coupled inductors with powder cores used in three-phase DC-DC converters. The first method is for three-phase coupled inductors with an asymmetric magnetic core structure, and the values of each self-inductance and mutual inductance can be measured separately. The second method is a simplified measurement method limited to multiphase coupled inductors with symmetric magnetic core structures. DC superimposition characteristics of coupled inductors can be measured with a smaller number of measurements than the first method, and it can be extended to N phase coupled inductors. The verification of the two methods has been evaluated through simulation and experiment.

DOI： 10.1109/ECCE47101.2021.9595692

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Proceedings of the Energy Conversion Congress and Exposition - Asia, ECCE Asia 2021  

Compound semiconductor devices such as Gallium Nitride (GaN) and Silicon Carbide (SiC) are actively adopted in power converters to improve power conversion efficiency, downsize passive components and miniaturize cooling systems. However, in the power converters, magnetic components often become bottlenecks in power converters from size, power losses, and temperature rise perspective. Therefore, in some cases, the attractive performance of GaN and SiC cannot be fully utilized due to the limits imposed by magnetic components. To indicate this matter from an experimental perspective, this paper conducts a fundamental investigation of the downsizing effect of magnetic components and temperature rise when varying switching frequency (85 kHz, 150 kHz, 350 kHz, 1 MHz) of a 1 kW boost converter as a case study. As results of experiments, although high-switching frequency operation contributes to downsizing magnetic component effectively, the thermal runaway of the magnetic core while driving at high frequency is confirmed due to downsized small surface area and increasing iron loss due to temperature dependency of Mn-Zn ferrite magnetic cores. For a fair comparison, the area product approach is used in the design procedure for selecting core size. The effect of the high-frequency drive is discussed from theoretical and experimental viewpoints.

DOI： 10.1109/ECCE-Asia49820.2021.9479365

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Language：Japanese   Publisher：9th IEEE International Conference on Power Electronics, Drives and Energy Systems, PEDES 2020  

High-power inverters with high frequency have been required for progressing technologies such as wireless power transfer (WPT) and plasma processing. Recently, gallium nitride high electron mobility transistor (GaN-HEMT) is getting lots of attention from the viewpoint of fast switching ability and low power consumption. However, GaN-HEMT inverters are difficult to be operated in over several kW because of its low drain-source breakdown voltage. In other words, the conventional half-bridge GaN-HEMT inverter can output high power only for the small load resistance less than several-O. This paper overcomes this difficulty by implementing an impedance conversion network in the prior stage of the series resonator. The proposed topology realizes not only high-power from low drain-source voltage but also the sine wave output with very low harmonics. 3kW output to 50O load at 13.56MHz is theoretically designed, and verified by computer simulations. And also, the experimental prototype using GaN-HEMTs achieves the high efficiency of 99.43% at 13.56MHz and 471W.

DOI： 10.1109/PEDES49360.2020.9379451

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Authorship：Last author   Language：English  

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TMAG.2020.3014592

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Language：Japanese   Publisher：12th AEIT International Annual Conference, AEIT 2020  

An Activity Smoothen Circuit with bidirectional Buck-Boost Converter (AS-BBC) was approached to smoothen the output power of a power factor correction (PFC) converter, which is an AC/DC converter, without using any electrolytic capacitors in this paper. In order to smoothen the output pulsation current of the PFC converter, electrolytic capacitors have been used generally, since electrolytic capacitors have a large magnitude capacity. However, there is a lifespan to electrolytic capacitors. On the other hand, film capacitors have a semi-permanent lifespan with so much less magnitude capacity than electrolytic capacitors. A way of using the AS-BBC to make a small capacitor work like a large capacitor as a smoothing capacitor to handle the output power is presented in this paper. Approximately 47% of the pulsation output is suppressed with a 4.4μ F film capacitor with the AS-BBC. Since there is no electrolytic capacitor adapted, a semi-permanent lifespan PFC converter is achieved successfully.

DOI： 10.23919/AEIT50178.2020.9241166

Scopus

Language：Japanese   Publisher：IEEE International Symposium on Industrial Electronics  

To realize the early development of power converters, research on the front-loading design in which the efficiency, control characteristics, converter size, thermal management, and Electromagnetic Compatibility (EMC) are carefully considered before making a prototype, has been attracting. To carefully design and predict these design factors before prototyping, making accurate models of active/passive components operated on simulation of the multi-physical domain such as thermal, magnetic, and electrical is indispensable. This is because these characteristics of active/passive components on power converters are affected by each other. In this background, this paper proposes a nonlinear relative permeability modeling method with a temperature dependency of gapped-ferrite cores. The temperature dependency of the effective relative permeability of the gapped-ferrite core is investigated under core temperature within-50°C-+ 150°C. As features of the proposed modeling method and simulation model, a simple mathematical equation and lookup tables are utilized for simple implementation to the simulator. The validity of the proposed modeling method is confirmed by both simulation and experimental tests under operating conditions including the magnetic saturation regions.

DOI： 10.1109/ISIE45063.2020.9152521

Scopus

Language：Japanese   Publisher：IEEE International Symposium on Industrial Electronics  

To achieve high power density, a power converter circuit is often operated at high frequency, and fast switching devices are also combined to reduce switching loss. On the other hand, both high frequency and fast switching greatly increases conductive noise amplitude at frequency over several megahertz. Therefore, electromagnetic compatibility (EMC) is necessary for a high power density converter. However, an additional filter, which consists of large and heavy passive elements, greatly degrades power density. Thus, in this paper, a noise reduction method for noise at frequency band over 10 MHz with small volume increase is presented and investigated. Consequently, the simulation and experimental result verifies that the proposed method decreases MHz-band noise with small volume increase.

DOI： 10.1109/ISIE45063.2020.9152408

Scopus

Language：Japanese   Publisher：IEEE International Symposium on Industrial Electronics  

Both silicon-carbide (SiC) and gallium-nitride (GaN) are wide bandgap power transistor which are developing rapidly. They are able to be used as the main switches in the high-frequency power conversion systems successfully. These high-frequency switches just meet the high demand of low-size power electronics device in recent years. As the high-frequency system always relies on the switches, we designed and made evaluation boards for both SiC and GaN switches by 13. 56MHz half-bridge inverter. Both simulation and experimental results show that GaN achieved more successfully switching, which made good output waveform with very short dead-time. And in simulation, lower switching loss of GaN is also confirmed. As all above, it is obvious that GaN device is more suitable for high-frequency application.

DOI： 10.1109/ISIE45063.2020.9152253

Scopus

Authorship：Lead author   Language：English  

Authorship：Last author   Language：Japanese  

Language：Japanese  

DOI： 10.35848/1347-4065/ab75b9

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Scopus

Language：Japanese  

This paper presents a bidirectional converter using by multi-stage FET driving technique. The proposed converter is constructed by implementing series connected low voltage Si-FETs in multi-stage. A driving circuit using multi-stage driving technique can drive series connected FETs from the one power supply without any isolated power supplies and high voltage process ICs. In addition, the balancing capacitors which constructed the converter have voltage averaging function in drain-source voltage to tackle the voltage unbalance between the series connected FETs. Using the figure of merit which can estimate converter losses from the specification of power devices, the usefulness of the circuit configuration which using low voltage Si-FETs instead of SiC-FETs is shown. The effect of the voltage averaging function by the balancing capacitors, the operating principle of the driving circuit and the power conversion mechanism are clarified and presented using the circuit simulator and a converter equivalent circuit. The experimental results show that the proposed driving technique allows the bidirectional converter to achieve a maximum power conversion efficiency of 99.2%.

DOI： 10.14923/transcomj.2019jbp3022

CiNii Research

Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

<p>This paper presents a bidirectional converter with multi-stage FETs featuring voltage balance control function using variable capacitors. The proposed converter is constructed using low-voltage Si-FETs in a series connection, and it improves the voltage balance between the drain-source voltages of the series connected FETs in the OFF period. Using the converter figure of merit (FOM), which can estimate the converter losses from the specifications of the FETs, the effectiveness of the proposed converter is compared to that of a converter using SiC-FETs. The factors of the voltage unbalance are analytically clarified using the equivalent circuit. The principle of voltage balance control function using the variable capacitor is discussed. The experimental results show that the proposed converter can achieve a maximum power conversion efficiency of 99.2%.</p>

DOI： 10.1541/ieejias.140.168

Scopus

CiNii Research

Language：Japanese   Publisher：Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC  

This paper proposes a voltage balancing control method using variable capacitors with simple turn-on adjusting function for multi-stage FET bidirectional converter. The proposed voltage balancing control circuit is composed of a feedback circuit using photocouplers and a delay circuit using variable capacitors with turn-on adjusting diodes. The proposed voltage balancing circuit can reduce the drain-source voltage unbalance which occur during the turn-on and turn-off period of series-connected FETs. The theoretical discussion includes analyzing the unbalanced drain-source voltage in seriesconnected FETs using a simplified converter. Also, the principal of the proposed voltage balancing control method is clarified. The experimental results show that the proposed voltage balancing control method can reduce the drain-source voltage difference Δvds of series-connected FETs from 36 V to 11 V (69% reduction in Δvds) during the turn-off and from 22 V to 11 V (50% reduction in Δvds) during the turn-on period. The multistage FET bidirectional converter can achieve a maximum power conversion efficiency of 99.2%.

DOI： 10.1109/APEC39645.2020.9124221

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TPEL.2019.2911093

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Language：English   Publisher：Journal of Hand Surgery Global Online  

Purpose: To investigate multidimensional pain intensity and quality after collagenase Clostridium histolyticum (CCH) injection in patients with Dupuytren contracture using a pain visual analog scale (VAS) and the revised version of the Short-Form McGill Pain Questionnaire (SF-MPQ-2). Methods: This prospective observational study was carried out from 2015 to 2017. As a primary end point, patients completed the pain VAS (range, 0 [no pain] to 100) and SF-MPQ-2 before and after CCH injection; 3, 9, and 24 hours after CCH injection; after the extension procedure; and 3 and 7 days after CCH injection. In addition, they reported the dose and duration of supplementary analgesic use during this period. Results: A total of 41 patients were enrolled in this study (51 joints). Mean pain VAS score (mean ± SD, 34 ± 21) was maximal 9 hours after CCH injection and decreased within the following 7 days. The total score of the SF-MPQ-2 significantly increased after CCH treatment and decreased in the 7 days after the injection. Among the SF-MPQ-2 subscales, the highest and lowest scores after CCH injection were recorded for continuous pain and affected descriptors, respectively. Nonsteroidal anti-inflammatory drugs were most frequently self-administered during 7 days after the extension procedure compared with any other study period. Conclusions: The pain VAS and SF-MPQ-2 revealed acute pain after CCH injection. However, all examined pain aspects dramatically improved within 7 days after injection. Pain after CCH injection is characterized by low scores in the Affective Descriptors subscale of the SF-MPQ-2. Type of study/level of evidence: Prognostic Ⅳ.

DOI： 10.1016/j.jhsg.2019.10.004

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PubMed

Language：English  

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Authorship：Last author   Language：English  

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Language：English  

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Authorship：Last author   Language：English  

Web of Science

Language：Japanese   Publisher：The Japan Institute of Power Electronics  

This paper presents an energy management storage system with a multi-stage FET bidirectional converter. The
proposed system is constructed by a bidirectional converter using series connected FETs, and it realizes highly energy management that maximizes battery performance. By calculating the power loss using the converter performance index FOM (Figure of merit), it is shown that the proposed configuration can be possible to reduce the power loss 70% compared to the conventional configuration. In the proposed system, using a power control method that reduces the charging current, the battery charging losses can be reduced 60%. The analysis results show that the proposed system can achieve a charging energy efficiency of 96.9%, and reduce the yearly CO2 emission of 33%.

DOI： 10.5416/jipe.46.44

CiNii Research

Language：Japanese  

DOI： 10.1149/2.0551916jes

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TPEL.2018.2886044

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Scopus

Language：Japanese   Publisher：Proceedings of the International Conference on Power Electronics and Drive Systems  

One of the best techniques for downsizing power converters is to use coupled inductors in multiphase circuits. Meanwhile, from a magnetic material perspective, powder core material is well known as an attractive magnetic material with superior features such as high saturation flux density. However, since the relative permeability of power cores depends on the magnetic field intensity, designing coupled inductors is difficult, and the modeling method is not well discussed in the relevant literature. The purpose of this research is to model coupled inductors with powder cores and present a simple magnetic design method. A model of coupled inductors is created by a novel measurement method of the dc superimposition characteristic unique to the coupled inductor of two-phase interleaved circuits. Furthermore, a design method based on a theoretical analysis using a magnetic circuit model had been established. The validity and effectiveness of the proposed methods are confirmed from simulation and experimental tests. This research is helpful in the field of the model-based development of coupled inductors.

DOI： 10.1109/PEDS44367.2019.8998883

Scopus

Publisher：Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC  

Resonant converters rely on a precise knowledge of leakage inductance of the equipped transformers. Resonant circuit topologies such as LLC usually utilize the transformer leakage as an inductive component in the resonant tank, allowing for a drastic reduction in the converter weight, size and volume. The existence of the secondary leakage inductance affects the whole operation of the LLC resonant converter. This paper reveals that placing the secondary winding near the air gap would increase the resonant tank input impedance, vertically shrink the voltage-gain curve of the converter, and consequently minimize the frequency range (i.e frequency bandwidth with respect to load variation). On contrary, placing the secondary winding in a close contact with the magnetic core would decrease the resonant tank input impedance, vertically stretches the voltage-gain curve of the converter, and widen the frequency variation range. It has been reported that the winding location with respect to the air gap has an impact on the leakage inductance value. In other words, placing the secondary winding in a close contact with the magnetic core (zero mmf position) would maximize the leakage energy storage originated from the secondary winding, and hence maximize the secondary leakage inductance and vice versa. The theoretical discussion is presented which is merely based on Ampere's law and Dowell's model. Furthermore, transformer prototypes had been constructed and tested in a 390V/12V-220W LLC converter prototype to evaluate the proposed analysis.

DOI： 10.1109/APEC.2019.8722190

Scopus

Publisher：Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC  

Minimizing the transformer magnetizing inductance is essential for the soft switching operation of the LLC resonant converter, despite the fact that it results in higher values of magnetizing current, which deteriorates the converter efficiency. Furthermore, it is a well-known practice to utilize the transformer leakage as an inductive component in the resonant tank to improve the power destiny. This paper reveals that the transformer voltage gain can be improved when the transformer leakage inductance in concentrated on the secondary side to avoid the voltage drop inflicted by the relatively large value of the magnetizing current (im), especially at light load condition. The theoretical discussion relies on the asymmetry of the EI core by placing the secondary winding in a close contact with the magnetic core and placing the primary winding in the vicinity of the air gap. Moreover, noise absorber had been utilized to control the leakage inductance value. The proposed transformer design maximizes the value of the secondary leakage inductance and minimizes the primary leakage inductance. Alongside with the theoretical discussion, experimental tests had been conducted to evaluate the proposed method using a 390V-12V, 220W LLC resonant converter.

DOI： 10.1109/APEC.2019.8721980

Scopus

Language：Japanese   Publisher：2019 IEEE 3rd International Conference on DC Microgrids, ICDCM 2019  

This paper proposes a bidirectional converter with balancing capacitor using multi-stage FET driving technique. The proposed converter is constructed by implementing series-connected low voltage Si-FETs in multi-stages. The balancing capacitor can average the applied voltage on FETs in the transient state of the switching operation and tackle the voltage unbalance between the series-connected FETs. The proposed driving circuit is using multi-stage FET driving technique and can drive all the series-connected FETs using only one power supply. The effect of the balancing capacitor and the proposed driving technique are clarified and presented using the circuit simulator and the converter equivalent circuit. The proposed topology improves the converter power conversion efficiency. The experimental results show that the proposed driving technique allows the bidirectional converter to achieve a maximum power conversion efficiency of 99.2%.

DOI： 10.1109/ICDCM45535.2019.9232896

Scopus

Language：Japanese   Publisher：2019 IEEE 3rd International Conference on DC Microgrids, ICDCM 2019  

This paper proposes a cooperative control used in a power conversion system consists of several energy sources and modular DC/DC converters. The proposed cooperative control method has attractive features of realizing constant dynamic characteristics even when each input voltage fluctuates or in case of the output power of each input voltage source is limited. The proposed cooperative control method has dual control loops with current control as an inner loop and voltage control as the outer loop. In addition, feed-forward control of the input voltage and the compensators for each control loop are implemented to suppress the influence of input voltage fluctuation or power capacity limit on dynamic characteristics. The effectiveness of the proposed control is validated by simulation test.

DOI： 10.1109/ICDCM45535.2019.9232868

Scopus

Publisher：ICPE 2019 - ECCE Asia - 10th International Conference on Power Electronics - ECCE Asia  

Utilizing powder cores in many power electronics applications have been gaining much attention due to their attractive magnetic properties. However, it is quite challenging for the circuit designer to choose the proper core, as there are many kinds of magnetic powder cores available in the market. Therefore, due to the limitation of a single magnetic material property, it is often difficult to realize high power conversion efficiency within wide load ranges, including light and heavy load conditions. This paper proposes a novel design method of the multi-material inductor which combines multiple powder cores having different material properties. The aim of this work is to provide improved efficiency over the entire load range of power converters. The experimental results have proven that the inductor with multi-material powder cores can improve the efficiency over wide load range. The validity and effectiveness of the proposed magnetic design method are confirmed from theoretical analysis, simulation and experimental tests.

Scopus

Language：Japanese   Publisher：一般社団法人 電気学会  

<p>はじめに</p><p>電気学会東海支部としては，学術講演会，講習会，見学会，サイエンスセミナーなどの諸行事を開催し，学会活動の一層のオープン化を目指している。今回はそういった地域貢</p>

DOI： 10.1541/ieejjournal.139.244

CiNii Research

Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：The Institute of Electrical Engineers of Japan  

DOI： 10.1541/ieejjournal.139.76

CiNii Research

Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

<p>The utilization of powder cores for many power electronic applications has drawn a significant amount of attention owing to their attractive magnetic properties. However, because of their low relative permeability characteristics, a precise measurement of the core loss is very difficult to obtain. Imprecise estimation of the core loss may lead to an inaccurate thermal design of power converters. Measuring and calculating the accurate value of the core loss allows the circuit designer to design a more efficient system. This paper discusses the revalidation of electrical measurement by comparing the electrical method with the calorimetric method in powder cores. The calorimetric method is one of the most promising methods to accurately measure the core loss; however, it is time consuming. A difference less than 10% has been reported for the core loss measurement error while comparing the electrical method and the calorimetric method in various conditions. These results indicate that the electrical method using the B-H analyzer is effective for measuring the core losses in some conditions for powder cores. Along with the theoretical discussion, simulation and experimental tests are also conducted.</p>

DOI： 10.1541/ieejjia.8.386

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CiNii Research

Authorship：Last author   Language：English  

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.23919/icpe2019-ecceasia42246.2019.8797162

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：English  

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Language：Japanese  

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Language：Japanese  

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Language：Japanese  

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Publisher：Proceedings - 2018 IEEE International Power Electronics and Application Conference and Exposition, PEAC 2018  

A novel integrated magnetic structure suitable for a high-frequency switching current resonant converter (LLC) with GaNFETs is proposed in this paper. Creating a leakage inductance to resonate with a capacitor, and the mutual inductance in an LLC resonant converter is the most common solution. However, the volume of leakage inductance is very difficult to be controlled or adjusted. Furthermore, the losses may increase when the leakage fluxes cross the patterns on the PCB board or the primary and secondary coils. In order to tackle this problem, a new magnetic structure core is proposed in this paper. The proposed magnetic structure can decrease the losses of the core, which means the magnetic structure proposed in this paper can improve the efficiency of the converter. A power density of approximately 2.6 W/cm 3 has been realized for the 1.4-MHz LLC resonant converter with the proposed magnetic structure with a maximum efficiency of 96.4%. Along with the theoretical discussion, finite element analysis (FEA) electromagnetic simulation and experimental results are also presented.

DOI： 10.1109/PEAC.2018.8590446

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：7th International IEEE Conference on Renewable Energy Research and Applications, ICRERA 2018  

Lots of researches of electric coupling is performed for wireless power transfer system. For achieving high power transfer, electric resonant coupling is used. A 3-phase electric resonant coupling is one option for higher power wireless transfer. However, as far as the author knows, much less work has been done for a 3-phase electric resonant coupling. In this paper, fundamental experiment of a 3-phase electric resonant coupling wireless power transfer is performed. From experiment results, the possibility that 3-phase electric resonant coupling can be used for wireless power transfer has been found.

DOI： 10.1109/ICRERA.2018.8566938

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIA.2018.2856631

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Scopus

Language：Japanese   Publisher：2018 International Power Electronics Conference, IPEC-Niigata - ECCE Asia 2018  

Utilizing powder cores in many power electronics applications have gained interest due to the attractive magnetic properties of powder core materials. For instance, powder cores have soft saturation characteristics and high saturation flux density compared to gapped ferrites. However, due to their low relative-permeability and the low loss characteristics, a precise measurement of the core losses is very difficult to be obtained. One of the common approaches to measure core losses is by measuring the electrical signals of the winding terminals, we hereafter refer it as electrical methods. Another alternative approach is calorimetric methods, which rely on measuring the core temperature rise. Nonetheless, these methods may have huge measurement error in case of powder cores. This paper evaluates the accuracy of measuring core losses in powder cores, and a comparison between the electrical and calorimetrical methods is presented. Along with the theoretical discussion, simulation and experimental tests are conducted.

DOI： 10.23919/IPEC.2018.8508012

Scopus

Publisher：2018 International Power Electronics Conference, IPEC-Niigata - ECCE Asia 2018  

Recently multi-hop wireless power transfer (WPT) systems for the area extension of a wireless battery charging have been addressed by several research groups. This paper describes a discrete exciting voltage control technique for the multi-hop WPT system via magnetic resonant coupling which can maximize the power transfer efficiency in response to the change of coupling status. The theory allows the equations of the wireless power transfer efficiency of the system to be determined at all the ratio of the mutual inductance. The calculated results are included to confirm the advantage to single transmitting multi-hop WPT systems.

DOI： 10.23919/IPEC.2018.8508026

Scopus

Publisher：2018 International Power Electronics Conference, IPEC-Niigata - ECCE Asia 2018  

Powder cores have been gained much attention as one of the attractive magnetic cores used in power converters due to their superior features such as high saturation flux density or distributed air gaps. However, powder cores have a unique feature that the relative permeability of the magnetic core varies depending on the magnetic field intensity. However, modeling the variable relative permeability, the design method for powder cores, and computer simulation methods of non-linear inductance are well not discussed in the related literature. Therefore, this paper proposes a novel modeling, magnetic design methods, and simulation technique considering dc superimposition characteristics of powder cores. The modeling method uses a novel model equation representing the behavior of relative permeability under the dc current superimposition condition, which is helpful to evaluate the performance of powder cores and to properly design various magnetic components. Theoretical analysis has been presented and the effectiveness and the validity of the proposed methods are evaluated through simulation and experimental tests.

DOI： 10.23919/IPEC.2018.8507874

Scopus

Language：Japanese   Publisher：一般社団法人 電気学会  

<p>2014年の赤﨑勇終身教授（名城大学），天野浩教授（名古屋大学），中村修二教授（カリフォルニア大学）の3名へのノーベル物理学賞受賞のインパクトからも分かるとお</p>

DOI： 10.1541/ieejjournal.138.695

CiNii Research

Language：Japanese  

DOI： 10.1049/iet-pel.2017.0361

Web of Science

Scopus

Language：Japanese   Publisher：IEEE International Symposium on Industrial Electronics  

In multi-phase power conversion circuits, achieving an equalized current sharing between the paralleled modules is a challenge. Especially, in the LLC resonant converter topology, where the voltage gain is very sensitive to a minor change in the resonant tank parameters. In practical applications, the resonant tank parameters are never exactly identical among the phases, leading to unbalanced current sharing between the paralleled modules. This paper reviews the state of the art of current balance mechanisms proposed previously in the literature and revisits a newly proposed method to improve the current balance, which relies on a single balancing transformer connected in series with the paralleled resonant tanks. A comparison between the proposed method and connecting the three transformers in star is conducted. While evaluating the current balancing methods, the following sources of unbalance have been considered: a) resonant and magnetizing inductances b) resonant capacitors. c) on-resistances of the switching devices. d) propagation delay of the gate drivers.

DOI： 10.1109/ISIE.2018.8433827

Scopus

Authorship：Last author   Language：English  

DOI： 10.1049/iet-cds.2017.0255

Web of Science

Language：Japanese   Publisher：Heart and Vessels  

Peripheral artery disease plays a pivotal role for access site selection in transcatheter aortic valve replacement (TAVR). Abnormal ankle–brachial index (ABI) is a generalized mortality marker in many cardiovascular scenarios. However, the long-term outcomes in high-risk TAVR populations remain unclear. We investigated the association between low ABI and 2-year outcome after TAVR. Of 1613 patients enrolled in the OCEAN-TAVI registry, 1458 (90.4%) who underwent ABI before TAVR were divided into groups: patients with (1) ABI ≥ 0.9 in both legs and (2) ABI < 0.9 in either leg. Primary endpoint was all-cause death within 2 years. ABI < 0.9 was noted in 304 patients (20.8%). ABI < 0.9-group had more frequent and severe comorbidities. Primary endpoint in ABI < 0.9-group was significantly higher than that in ABI ≥ 0.9-group (15.8 vs. 8.7%, p < 0.001). This trend continued in the transfemoral (TF)-approach (14.9 vs. 7.5%, p < 0.001), but not in the alternative approach (17.2 vs. 15.8%, p = 0.815). Within 30 days, ABI < 0.9-group had a higher cardiac death rate (3.1 vs. 1.0%, p = 0.033), whereas between 31 days and 2 years, non-cardiovascular death was more frequently observed (9.2 vs. 5.1%, p = 0.003). In ABI < 0.9-group, in-hospital vascular complications (11.9 vs. 4.9%, p < 0.001) and acute kidney injury (10.8 vs, 5.7%, p = 0.009) were more frequently found when using the transfemoral-approach. In multivariate analysis, ABI < 0.9 was an independent predictor of 2-year mortality (adjusted hazard ratio 1.495, 95% CI 1.007–2.220, p = 0.046). Pre-procedure ABI < 0.9 is a useful prognostic marker for all-cause mortality, even in high-risk TAVR populations.

DOI： 10.1007/s00380-017-1096-y

Scopus

Language：Japanese   Publisher：IEEE Journal of Emerging and Selected Topics in Power Electronics  

Integrated magnetics is applied to replace the three-discrete transformers by a single core transformer in a three-phase LLC resonant converter. The magnetic circuit of the integrated transformer is analyzed to derive coupling factors between the phases; these coupling factors are intentionally minimized to realize the magnetic behavior of the three-discrete transformers, with the benefit of eliminating the dead space between them. However, in a practical design, the transformer parameters in a multiphase LLC resonant converter are never exactly identical among the phases, leading to unbalanced current sharing between the paralleled modules. In this regard, a current balancing method is proposed in this paper. The proposed method can improve the current sharing between the paralleled phases relying on a single balancing transformer, and its theory is based on Ampere's law, by forcing the sum of the three resonant currents to zero. Theoretically, if an ideal balancing transformer has been utilized, it would impose the same effect of connecting the integrated transformer in a solid star connection. However, as the core permeability of the balancing transformer is finite, the unbalanced current cannot be completely suppressed. Nonetheless, utilizing a single balancing transformer has an advantage over the star connection, as it keeps the interleaving structure simple which allows for traditional phase-shedding techniques, and it can be a solution for the other multiphase topologies where realizing a star connection is not feasible. Along with the theoretical discussion, simulation and experimental results are also presented to evaluate the proposed method considering various sources of the unbalance such as a mismatch in: 1) resonant and magnetizing inductances; 2) resonant capacitors; 3) transistor on-resistances of the MOSFETS; and 4) propagation delay of the gate drivers.

DOI： 10.1109/JESTPE.2017.2777508

Web of Science

Scopus

Language：Japanese   Publisher：IEEE Transactions on Power Electronics  

High power density and high efficiency in dc/dc converters are required in various applications such as the automotive application. Interleaved multiphase circuits with integrated magnetic components can fulfill these requirements because passive components occupying significant space in power converters can be downsized without high-switching frequency driving of power devices. However, dc-biased magnetization is a drawback of integrated magnetic components because of unbalanced inductor average currents. This imbalance arises from the tolerance among the phase components. To overcome this problem, inductor average current control is implemented in interleaved multiphase dc/dc converters. Nevertheless, the imbalance cannot be completely eliminated because the current sensors inserted into each phase have gain errors. The purpose of this paper is to present a magnetic design method to improve the immunity to unbalanced currents. A comprehensive analysis is carried out with two main objectives: to prevent magnetic saturation, which may arise due to the current unbalance and to downsize the magnetic components by selecting the optimal coupling coefficient taking into consideration the maximum permissible percentage of unbalanced currents. Simulation case studies are presented to support the analysis. Finally, a 1-kW prototype of the interleaved boost converter is built to validate the accuracy of the design method.

DOI： 10.1109/TPEL.2017.2707385

Web of Science

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1049/iet-pel.2017.0485

Web of Science

Scopus

Language：Japanese  

DOI： 10.1049/el.2017.4013

Web of Science

Scopus

Language：English  

Web of Science

Language：English  

Web of Science

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

Web of Science

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

Web of Science

Authorship：Last author   Language：English  

Web of Science

Authorship：Last author   Language：English  

Web of Science

Language：Japanese  

Web of Science

Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：The Institute of Electrical Engineers of Japan  

<p>This paper proposes a novel control method to improve the responsiveness and the robustness of the boost DC-DC converter. The proposed control method is a feedback control incorporating a minor control that works to balance the input and output power. Experiment was carried out to verify the responsiveness and the robustness of the proposed control in comparison with the conventional voltage-mode and current-mode control. As a result, the proposed method revealed both of the fast response and the robust output voltage regulation against the load change.</p>

DOI： 10.1541/ieejeiss.138.395

Scopus

CiNii Research

Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (other academic)   Publisher：The Japan Institute of Power Electronics  

This paper presents a bidirectional convert using by multistage FET driving technique with voltage balance function. The voltage balance function can reduce influence of the voltage unbalance phenomenon which drain voltage fluctuation depending on output current. The voltage unbalance phenomenon is clarified by using an equivalent circuit of FETs connected in series. The necessity of voltage balance function is discussed, and verified in experiment. The experimental results have proven that the bidirectional converter by using the driving technique can achieve 98% or more power conversion efficiency from 170 W to 1000 W of power range, and a maximum power conversion efficiency of 99.2%.

DOI： 10.5416/jipe.44.128

CiNii Research

Language：Japanese   Publisher：2017 IEEE CPMT Symposium Japan, ICSJ 2017  

GaN-HEMT achieves the reduction in size and weight of power conversion circuits, thanks to its high frequency switching characteristics. However, the switching speed and low threshold voltage may cause a false turn-on phenomenon, which is a fatal effect for the applications. It is urgent issue to tackle and avoid this problem by modifying the circuit conditions. In this letter, the theoretical analysis of a full bridge inverter is developed to figure out the behavior of the gate voltage, which is the keyfactor parameter of false turn-on. Based on the analysis, the circuit conditions which minimize the gate voltage spike are derived.

DOI： 10.1109/ICSJ.2017.8240113

Scopus

Language：Japanese   Publisher：INTELEC, International Telecommunications Energy Conference (Proceedings)  

Wide band gap power semiconductor devices are now replacing the Si-MOSFET or IGBT. GaN-HEMT achieves the reduction in size and weight, thanks to its high frequency switching behavior. However, its high-speed switching characteristics and low threshold voltage may cause a false turn-on phenomenon, which is a fatal effect for the applications. It is urgent issue to tackle and avoid this problem by modifying the circuit conditions. We described differential equations from simplified equivalent circuit of inverter, and algebraically solved with some assumptions. At the same time, drain voltage equation is also developed. As a result, the gate voltage fluctuation was described as a composite waveform including two LC resonance phenomenon, which occur on gate drive circuit and main power flow.

DOI： 10.1109/INTLEC.2017.8214160

Scopus

Language：Japanese   Publisher：INTELEC, International Telecommunications Energy Conference (Proceedings)  

Interleaved techniques and magnetic integration in a boost converter have gained attention in electric powertrains system for electric, hybrid and fuel cell vehicles in order to achieve high power density or to improve power conversion efficiency. Furthermore, the proposed multi-phase boost converter is equipped with a phase drive control to improve the efficiency at all load ranges. Furthermore, a design method of a coupled-inductor for an interleaved boost converter with phase drive control is also proposed. However, the interleaved DC-DC converter using coupled method with phase drive control has many problems. In this paper, this problem of interleaved DC-DC converter using coupled inductor with phase drive control (PDC) is analyzed. In addition, defensive method of this method.

DOI： 10.1109/INTLEC.2017.8214190

Scopus

Publisher：INTELEC, International Telecommunications Energy Conference (Proceedings)  

DC-DC converters in electric vehicle (EVs) and hybrid electric vehicles (HEVs) have required higher power density and high efficiency. This paper proposes a novel LLC resonant DC-DC converter with integrated transformer. This circuit is composed of three LLC converter cells which are connected in series on the primary side and in parallel on the secondary side with interleaved control scheme. The Series Input Parallel Output (SIPO) structure enables the converter cells to share the input voltage and output current. The interleaved operation diminishes the ripple current of the output capacitor, and can reduce the size of the output capacitor. Also a reduction effect of the transformers is obtained by using the integrated transformer which independent transformers are combined into a single core. All these features make the proposed converter suitable for especially high input voltage and high output current applications to realize higher power and higher efficiency. The steady state operating principle of the converter was demonstrated. The theoretical analysis, the equivalent model and voltage gain of the converter are presented based on fundamental harmonic analysis of the converter. A prototype with 330V input and 500W output was built-up to validate the theoretical analysis.

DOI： 10.1109/INTLEC.2017.8214186

Scopus

Publisher：2017 6th International Conference on Renewable Energy Research and Applications, ICRERA 2017  

An interleaved multi-phase converter with coupled inductor can achieve high power density and high efficiency, and is an effective approach for high power applications. However, a number of phases also results in the fact that component counts are increased. In this paper, the downsizing performances when the number of phase change in a multi-phase DC-DC converter with 2-phase coupled inductor cell are investigated to make the full performance. The volume and the loss modeling of each component at n-phases are provided. Also some comparison results are derived and discussed.

DOI： 10.1109/ICRERA.2017.8191096

Scopus

Language：Japanese   Publisher：IET Power Electronics  

One of the main problems in electric vehicles is the volume of their electrical systems because their bulky components carry additional mass and high cost to the total system. On this topic, interleaving-phases and magnetic coupling techniques have been reported as effective methods for increasing the power density of the DC-DC converters that work between the storage unit and the motor inverter. In that sense, a volume assessment of these topologies would provide a better understanding of the problems to be faced when an electric power train is designed. In this paper, a volume modelling methodology is introduced with the purpose of comparing four different DC-DC converters: Single-Phase Boost, Two-Phase Interleaved with non-coupled inductors, Loosely Coupled Inductor (LCI), and Integrated Winding Coupled Inductor (IWCI). The analysis considers the volume of magnetic components, power devices (conventional and next-generation), cooling devices and capacitors. The methodology can be used as a part of an optimization procedure to minimize the volume of DC-DC converters. Conclusively, LCI and IWCI were found effective to miniaturize power converters with a power density of 8.4 W/cc and 9.66 W/cc, respectively. Moreover, a maximum efficiency of 98.04% and 97.61% was obtained for a 1kW LCI and IWCI prototypes, respectively.

DOI： 10.1049/iet-pel.2017.0157

Web of Science

Scopus

Language：Japanese   Publisher：2017 19th European Conference on Power Electronics and Applications, EPE 2017 ECCE Europe  

In the LLC resonant converter,the transformer core is usually gapped to realize the designed value of magnetizing inductance that allows for soft switching. The air gap length which is in a scale of millimeters may be affected by the humidity and long working hours of the ferrite material, resulting into a variation of the core permeability. Moreover, a slight variation of the transformer core permeability may be encountered with any possible change in the core temperature. In a proper transformer design, the transformer shall operate with an optimum value of effective permeability where the sum of both copper and core losses is minimal. In this paper, the transformer optimal design is presented. Moreover, the influence of the permeability on the transformer's copper and core losses is revealed. Furthermore, with the help of newly derived equations, the effect of the transformer's effective permeability on the LLC converter conduction turn-on and turn-off losses is reported. Along with the theoretical discussion,the analysis is supported with simulation and experimental results utilizing a 250W 200kHz prototype.

DOI： 10.23919/EPE17ECCEEurope.2017.8099301

Scopus

Language：Japanese   Publisher：2017 IEEE Energy Conversion Congress and Exposition, ECCE 2017  

In conventional arrangements of three-phase LLC converters, there are at least three magnetic components that occupy a considerable volume and mass of the power converter. Although, the three-phase LLC topology has many advantages over the single-phase one, circuit designers tend to select the singlephase topology because it has a minimal number of magnetic components. In this paper, with the purpose of promoting the industrial applications of the three-phase topology, Lagrangian dynamics is applied to theoretically prove that it is possible to replace the three-discrete transformers by a single integrated transformer. The Lagrangian dynamics theory allowed us to derive a physically motivated model for the integrated transformer, in which each component of the integrated transformer has its own Lagrangian parameter. The remarkable result to emerge from the Lagrangian model is that in a symmetrical design, there is no interphase coupling; this is regardless of the value of the coupling coefficient between the phases. This means that there is no return path for the three ac fluxes, and as a result the magnetic components can be downsized. Therefore, the major advantages of using integrated magnetics in the LLC converter can be concluded as: cost-reduction, reduced weight, and realizing higher power density. Along with the theoretical discussion, experimental validation is provided utilizing a 500W - 390V/12V - 200kHz prototype.

DOI： 10.1109/ECCE.2017.8096668

Scopus

Language：Japanese   Publisher：2017 IEEE Energy Conversion Congress and Exposition, ECCE 2017  

SiC-MOSFETs have attracting increasing attention because of their outstanding characteristics that contributes to high efficiency and high power density of power converters. However, compared to conventional Si-IGBTs, SiC-MOSFETs are susceptible to false triggering, because they tend to generate large switching noise due to ultrafast switching capability and have a lower threshold voltage in high temperature operation. Particularly, disastrous oscillation of repetitive false triggering can occur after a fast turn-off, which is the severe issue for practical application of SiC-MOSFETs. The purpose of this paper is to give an instruction to avoid this phenomenon. This paper hypothesized that the repetitive false triggering is the parasitic oscillation caused by parasitic capacitance of SiC-MOSFET, and parasitic inductance of wiring. Based on this hypothesis, this paper analyzed the oscillatory condition of the parasitic oscillator to propose a design instruction to avoid the oscillatory false triggering. The result revealed that the parasitic inductance of the gate, drain, and source wiring should be designed so that the resonance frequency of the parasitic LC resonator in the gating circuit is far apart from that of the power circuit. This paper also presents experimental results that support appropriateness of the proposed design instruction.

DOI： 10.1109/ECCE.2017.8096861

Scopus

Language：Japanese   Publisher：2017 IEEE Energy Conversion Congress and Exposition, ECCE 2017  

GaN HEMT is generally characterized as fast switching and expected to achieve a power converter with high efficiency and high power density as a next-generation power semiconductor. However, the fast switching generates large switching noise, causing gate voltage fluctuation. Therefore, GaN HEMT can suffer from false triggering such as a false turn-on phenomenon due to its own low threshold voltage. The phenomenon is problematic especially for practical applications such as a half-bridge circuit. In order to elucidate this phenomenon, we derived the equation expressing gate voltage fluctuation. As a result, the gate voltage fluctuation was described as a composite waveform including two resonance frequencies. Additionally, the appropriateness of the analysis result was supported by comparing theoretical peak gate voltage of the simulation and experimental results. On the other hand analytical results indicated likelihood that balancing factors included in an analytical expression suppress false turn-on phenomenon. Although analytical treatment elucidated gate voltage fluctuation comprehensively, theoretical equation is complicated as design guideline to avoid the false turnon phenomenon. Therefore, this paper analyzed the gate voltage fluctuation mathematically based on L'Hopital's Rule and derived the minimum condition of the peak gate voltage. As a result, mathematical treatment proposes a design method focusing on a peak gate voltage that can achieve the safe operation of a halfbridge circuit.

DOI： 10.1109/ECCE.2017.8095953

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：2017 IEEE Energy Conversion Congress and Exposition, ECCE 2017  

Interleaved DC-DC converter employing closecoupled inductors is a popular topology among other power converters topologies. Close-coupled inductors allow the power converter to achieve high power density and high efficiency. This paper proposes a novel magnetic structure of close-coupled inductors suitable for increasing the thermal handling capability. The proposed magnetic structure is combined of different magnetic materials, namely, ferrite and powder cores. The design method of the integrated close-coupled inductors are presented. Furthermore, this design method is considering the DC bias superposition characteristics, and the iron and copper losses as well. A 300W prototype is built to validate the proposed analysis. Finally, excellent heat dissipation of the proposed magnetic structure of the integrated close-coupled inductors is also reported.

DOI： 10.1109/ECCE.2017.8095782

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1049/el.2017.2225

Web of Science

Scopus

Language：English  

Web of Science

Authorship：Last author   Language：English  

Web of Science

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

Web of Science

Authorship：Last author   Language：English  

Web of Science

Authorship：Last author   Language：English  

Web of Science

Authorship：Last author   Language：English  

Web of Science

Authorship：Last author   Language：English  

Web of Science

Language：English  

Web of Science

Authorship：Last author   Language：English  

Web of Science

Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

<p>Interleaved dc-dc converters with integrated magnetic components are popular as converters capable to achieve high efficiency with less of volume and mass. There are three methods for integrated magnetic components: loosely-coupled inductors, closed-coupled inductors and integrated-winding-coupled inductors. This paper presents a method to calculate the allowable power in various circuit topologies. It is useful for measuring the allowable power without magnetic saturation of an inductor based on its size. Following the analysis of allowable power for each coupled inductor, the allowable power of the integrated magnetic components is compared to that of the conventional interleaved converter. This comparison is realized under the same conditions. As a result, the interleaved converter with loosely-coupled and integrated winding coupled inductors were found to be effective for the downsizing of the magnetic components under continuous conduction mode operation. On the other hand, the interleaved converter with close-coupled inductors is effective for the downsizing of the magnetic components under critical conduction mode operation. This comparative data is discussed from both theoretical and experimental points of view.</p>

DOI： 10.1541/ieejjia.6.463

Web of Science

Scopus

CiNii Research

Authorship：Last author   Language：English  

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

Web of Science

Language：Japanese   Publisher：The Japan Institute of Electronics Packaging  

DOI： 10.11486/mes.27.0_15

CiNii Research

Language：Japanese   Publisher：Conference Proceedings - 23rd ISSAT International Conference on Reliability and Quality in Design  

In recent years, so-called "big data" have been attracting the attention of companies and researchers. This study aims to identify the number of visitors of each period and their characteristics based on the location data of mobile phone users collected by the mobile phone company. The study sites of this survey are tourist destinations in Ishikawa Prefecture and Toyama city, including Kanazawa city, which became nationally popular after the Hokuriku Shinkansen opened in 2015. The opening of the Hokuriku Shinkansen brought more visitors to many areas. However, it also led to fewer visitors in some areas. The positive effect was remarkable in Kanazawa.

Scopus

Language：Japanese Book type：Textbook, survey, introduction

Language：Japanese Book type：Textbook, survey, introduction

Language：Japanese Book type：Textbook, survey, introduction

Language：Japanese Book type：Textbook, survey, introduction

Total pages：130   Responsible for pages：9   Language：Japanese Book type：Textbook, survey, introduction

Total pages：138   Responsible for pages：14   Language：Japanese Book type：General book, introductory book for general audience

Total pages：98   Responsible for pages：7   Language：Japanese Book type：General book, introductory book for general audience

Language：Japanese Book type：Textbook, survey, introduction

Total pages：242   Responsible for pages：14   Language：Japanese Book type：Textbook, survey, introduction

Language：Japanese Book type：Textbook, survey, introduction

Total pages：12   Language：Japanese Book type：General book, introductory book for general audience

Language：Japanese Book type：Textbook, survey, introduction

Language：Japanese Book type：Textbook, survey, introduction

Language：Japanese

Total pages：6   Responsible for pages：1   Language：Japanese

Total pages：28   Responsible for pages：1   Language：Japanese

Total pages：36   Responsible for pages：1   Language：Japanese

Total pages：350   Responsible for pages：20   Language：Japanese

Total pages：500   Responsible for pages：6   Language：Japanese Book type：Textbook, survey, introduction

Total pages：450   Responsible for pages：7   Language：Japanese Book type：Textbook, survey, introduction

Total pages：450   Responsible for pages：7   Book type：Textbook, survey, introduction

Event date： 2024.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：徳島大学   Country：Japan  

Event date： 2024.3 - 3034.3

Language：English   Presentation type：Oral presentation (general)  

Venue：東京理科大学   Country：Japan  

Event date： 2024.3

Language：English   Presentation type：Oral presentation (general)  

Venue：徳島大学   Country：Japan  

Event date： 2024.3

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2024.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：機械振興会館   Country：Japan  

Event date： 2024.2

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Country：Japan  

Event date： 2024.2

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Event date： 2024.2

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Venue：Long Beach, CA   Country：United States  

Event date： 2024.2

Language：English   Presentation type：Poster presentation  

Venue：Long Beach, CA  

Event date： 2024.2

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Venue：喜山倶楽部   Country：Japan  

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Venue：三洋貿易（株）瑞浪展示場   Country：Japan  

Event date： 2024.1

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Country：Japan  

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Venue：名鉄グランドホテル   Country：Japan  

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Venue：大手町センタービル４階   Country：Japan  

Event date： 2024.1

Language：English   Presentation type：Oral presentation (general)  

Venue：Fraunhofer IZM, Berlin   Country：Germany  

Event date： 2023.12

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：東京ビックサイト   Country：Japan  

Event date： 2023.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：機械振興会館   Country：Japan  

Event date： 2023.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya University   Country：Japan  

Event date： 2023.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya University   Country：Japan  

Event date： 2023.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：Nagoya University   Country：Japan  

Event date： 2023.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya University   Country：Japan  

Event date： 2023.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya University   Country：Japan  

Event date： 2023.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya University   Country：Japan  

Event date： 2023.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya University   Country：Japan  

Event date： 2023.12

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：ANAクラウンプラザホテル金沢   Country：Japan  

Event date： 2023.11

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2023.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Kyoto, Japan   Country：Japan  

DOI： 10.1109/ICSJ59341.2023.10339571

Event date： 2023.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Kyoto, Japan   Country：Japan  

DOI： 10.1109/ICSJ59341.2023.10339574

Event date： 2023.11

Language：English   Presentation type：Oral presentation (general)  

Venue：IEEE   Country：Japan  

DOI： 10.1109/ICSJ59341.2023.10339578

Event date： 2023.11

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：梅田サウスホール・名古屋コンベンションホール・大手町三井ホール   Country：Japan  

Event date： 2023.11

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：中央電気倶楽部   Country：Japan  

Event date： 2023.11

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：ポートポートメッセ   Country：Japan  

Event date： 2023.11

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2023.11

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：日本教育会館　喜山倶楽部   Country：Japan  

Event date： 2023.11

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：名古屋大学 東山キャンパス 野依記念学術交流館   Country：Japan  

Event date： 2023.10 - 2023.11

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：軽井沢プリンスホテル   Country：Japan  

Event date： 2023.10

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：公益社団法人 自動車技術会   Country：Japan  

Event date： 2023.10 - 2023.11

Language：English   Presentation type：Oral presentation (general)  

Venue：IEEE  

DOI： 10.1109/ECCE53617.2023.10362859

Event date： 2023.10 - 2023.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Nashville, TN, USA   Country：United States  

Event date： 2023.10

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：ポートメッセなごや   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：山口県産業技術センター　多目的ホール   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：回路会館   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2023.8

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：富士ソフトアキバプラザ   Country：Japan  

Event date： 2023.8

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2023.8

Language：English   Presentation type：Oral presentation (general)  

Venue：名古屋工業大学   Country：Japan  

Event date： 2023.8

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：山口県産業技術センター　多目的ホール   Country：Japan  

Event date： 2023.7

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：東京ビッグサイト   Country：Japan  

Event date： 2023.7

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2023.7

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：豊田中央研究所　厚生施設アクタス   Country：Japan  

Event date： 2023.6

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Country：Japan  

Event date： 2023.6

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：回路会館   Country：Japan  

Event date： 2023.6

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：ミッドランドホールA   Country：Japan  

Event date： 2023.6

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：名古屋市工業研究所   Country：Japan  

Event date： 2023.5

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：アルカディア市ヶ谷私学会館   Country：Japan  

Event date： 2023.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Jeju Island,Republic of Koria   Country：Korea, Republic of  

Event date： 2023.5

Language：English   Presentation type：Oral presentation (general)  

Country：Korea, Republic of  

Event date： 2023.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Jeju Island,Republic of Koria   Country：Korea, Republic of  

Event date： 2023.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Jeju Island,Republic of Koria   Country：Korea, Republic of  

Event date： 2023.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Jeju Island,Republic of Koria   Country：Korea, Republic of  

Event date： 2023.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Jeju Island,Republic of Koria   Country：Korea, Republic of  

Event date： 2023.5

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：東京理科大学野田キャンパス7号館６階講堂   Country：Japan  

Event date： 2023.4

Language：Japanese   Presentation type：Symposium, workshop panel (nominated)  

Venue：TKP品川港南口会議室　ホール4A   Country：Japan  

Event date： 2023.4

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2023.4

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2023.3

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：名古屋市　名古屋商工会議所   Country：Japan  

Event date： 2023.3

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：オンライン   Country：Japan  

Event date： 2023.3

Language：Japanese   Presentation type：Oral presentation (keynote)  

Venue：オンライン   Country：Japan  

Event date： 2023.2

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：東京　如水会館   Country：Japan  

Event date： 2023.2

Language：Japanese   Presentation type：Oral presentation (keynote)  

Venue：名古屋市　名古屋国際センター別棟ホール   Country：Japan  

Event date： 2023.2

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：オンライン   Country：Japan  

Event date： 2023.2

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：東京　品川インターシティホール   Country：Japan  

Event date： 2023.2

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：東京　東京ビッグサイト   Country：Japan  

Event date： 2023.1

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：名古屋　名古屋観光ホテル   Country：Japan  

Event date： 2023.1

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：東京　東京ビッグサイト   Country：Japan  

Event date： 2023.1

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：東京　大手町ファーストスクエア   Country：Japan  

Event date： 2023.1

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：オンライン   Country：Japan  

Event date： 2023.1

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：名古屋　ナディアパークデザインホール   Country：Japan  

Event date： 2022.12

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：名古屋市　ウインク愛知   Country：Japan  

Event date： 2022.12

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：東京　東京ビッグサイト   Country：Japan  

Event date： 2022.12

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：東京　日本教育会館   Country：Japan  

Event date： 2022.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2022.11

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2022.11

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2022.11

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2022.10

Language：English   Presentation type：Symposium, workshop panel (nominated)  

Country：Japan  

Event date： 2022.10

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2022.10

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：東京　ダイトロン株式会社本社   Country：Japan  

Event date： 2022.10

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2022.10

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：東京　ビジョンセンター東京八重洲南口   Country：Japan  

Event date： 2022.10

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：愛知県　刈谷市産業振興センター   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：山口県　産業技術センター   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：名古屋　栄ガスビル   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：東京　コモレ四谷タワーコンファレンス   Country：Japan  

Event date： 2022.8 - 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：上智大学   Country：Japan  

Event date： 2022.8 - 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：上智大学   Country：Japan  

Event date： 2022.8 - 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：上智大学   Country：Japan  

Event date： 2022.8 - 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：上智大学   Country：Japan  

Event date： 2022.8 - 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：上智大学   Country：Japan  

Event date： 2022.8 - 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：上智大学   Country：Japan  

Event date： 2022.8

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：愛知県名古屋市   Country：Japan  

Event date： 2022.8

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2022.8

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2022.8

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2022.8

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2022.7

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2022.7

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2022.7

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2022.7

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2022.7

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：東京　東京ビッグサイト   Country：Japan  

Event date： 2022.7

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2022.7

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：東京　東京ビッグサイト   Country：Japan  

Event date： 2022.7

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2022.7

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：岡山県　ホテルメルパルク岡山   Country：Japan  

Event date： 2022.6

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：東京　東京ビッグサイト   Country：Japan  

Event date： 2022.6

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：東京 学士会館   Country：Japan  

Event date： 2022.6

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2022.6

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：東京　東京理科大学   Country：Japan