2022/03/17 更新

写真a

イシハラ マサタカ
石原 將貴
Ishihara Masataka
所属
自然科学学域 助教
職名
助教

学位

  • 博士(工学) ( 2021年3月   岡山大学 )

  • 修士(工学) ( 2017年3月   島根大学 )

 

論文

  • Sinusoidal-Flux Reluctance Machine Driven with Three-Phase Inverter for Improving Power Density with Reduced Torque and Input Current Ripples

    Masaki Iida, Kazuhiro Umetani, Takayuki Kusumi, Masataka Ishihara, Eiji Hiraki

    2021 23rd European Conference on Power Electronics and Applications, EPE 2021 ECCE Europe   2021年9月

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    掲載種別:研究論文(国際会議プロシーディングス)  

    Reluctance machines such as the switched reluctance machines (SRMs) and the synchronous reluctance machines (SynRMs) are recently investigated for propulsion motors of the electrified vehicles owing to their robust mechanical construction, high thermal tolerance, and cost-competitiveness. However, practical application of the reluctance machines to the vehicle propulsion has been hindered by the fact that the conventional SRMs and SynRMs are difficult to meet all the three preferable features for the vehicular application: 1. High power density, 2. Low torque and input-current ripples, 3. Being drivable by the normal three-phase inverter. This paper addresses this issue by proposing a novel reluctance machine. The prominent features of the proposed reluctance machine are the sinusoidal reluctance profile and the delta-connected phase windings, both of which differ from conventional reluctance machines. Along with the theoretical discussion of the basic operating principles of the proposed reluctance machines, this paper presents a simple performance estimation of the proposed machine, the SRM, and the SynRM, which supported that the proposed machine can meet the three preferable features. Furthermore, the experiment successfully supported the operating principles of the proposed machine, suggesting the feasibility of the proposed machine for vehicle applications.

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  • Autonomous System Concept of Multiple-Receiver Inductive Coupling Wireless Power Transfer for Output Power Stabilization Against Cross-Interference Among Receivers and Resonance Frequency Tolerance

    Masataka Ishihara, Keita Fujiki, Kazuhiro Umetani, Eiiji Hiraki

    IEEE Transactions on Industry Applications   57 ( 4 )   3898 - 3910   2021年7月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Institute of Electrical and Electronics Engineers ({IEEE})  

    Multiple-receiver resonant inductive coupling wireless power transfer (RIC-WPT) technique is emerging as a promising charging method for multiple household appliances, mobile devices, and wearable devices. However, this technique often suffers from output power fluctuation owing to the cross-interference among receivers as well as the manufacturing and aging tolerance of the resonant frequency (i.e., resonant frequency tolerance). This article proposes an autonomous RIC-WPT system concept to solve this difficulty. The proposed concept addresses the cross-interference and resonant frequency tolerance by incorporating the following two functions. First, the amplitude of the transmitter current is controlled to have a constant amplitude. Second, the phase of each receiver current is controlled to be orthogonal to that of the transmitter current by using an active reactance compensator installed in each receiver. The experiment of a two-receiver RIC-WPT system successfully verified that the two functions of the proposed system concept can stabilize the output voltage against the cross-interference and resonant frequency tolerance.

    DOI: 10.1109/TIA.2021.3081071

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  • Parasitic Inductance Design for Preventing Oscillatory False Triggering of Parallel-Connected GaN-FETs.

    Yusuke Hatakenaka, Kazuhiro Umetani, Masataka Ishihara, Eiji Hiraki, Hiroshi Tadano

    IECON Proceedings (Industrial Electronics Conference)   2021-October   1 - 8   2021年

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    掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    GaN-FETs are recently spreading in high-power switching converters, where GaN-FETs are commonly parallel connected to switch the large current. However, the parallel-connected GaN-FETs often suffer from false triggering because the parallel connection incorporates multiple LC resonators of the parasitic capacitance of GaN-FETs and the parasitic inductance of the printed circuit board, which can be easily excited by the switching noise and fluctuate the gate voltage. Particularly, GaN-FETs are susceptible to the self-sustaining repetition of the false triggering, i.e. the oscillatory false triggering, which must be prevented in industrial products. For prevention of this phenomenon in the case of a single GaN-FET, the preceding studies have proposed the design instruction of the parasitic inductance. However, few insights are available for the parallel-connected GaN-FETs. The purpose of this paper is to elucidate the design instruction to prevent the oscillatory false triggering for parallel-connected GaN-FETs through analyzing the equivalent circuit model of this phenomenon. The result revealed that parallel-connected GaN-FETs need the design instruction slightly modified from that for a single GaN-FET. The appropriateness of this modified instruction was verified by the simulation, suggesting the feasibility of this instruction for applying the parallel-connected GaN-FETs in high-power switching converters.

    DOI: 10.1109/IECON48115.2021.9589541

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    その他リンク: https://dblp.uni-trier.de/db/conf/iecon/iecon2021.html#HatakenakaUIHT21

  • Tiny Approaches to the Interactive Online Lectures Under the COVID-19 Pandemic.

    Eiji Hiraki, Masataka Ishihara, Kazuhiro Umetani

    IECON Proceedings (Industrial Electronics Conference)   2021-October   1 - 4   2021年

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    掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Due to COVID-19, Okayama University, one of the national universities in Japan, has been unable to enter the campus since March 2020. Therefore, all classes, meetings, and even graduation ceremonies were held online. Even now that large-scale vaccination is in progress, most of the lectures are stil online except for some small-scale classes that can secure the social distance. This paper introduces small attempts to effectively conduct the interactive online lectures of undergraduate and graduate schools.

    DOI: 10.1109/IECON48115.2021.9589676

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    その他リンク: https://dblp.uni-trier.de/db/conf/iecon/iecon2021.html#HirakiIU21

  • Feasibility of Parasitic Drain Inductance Design for Minimizing Switching Loss in Bridge Circuits Using GaN-FETs.

    Koki Abe, Masataka Ishihara, Yusuke Hatakenaka, Kazuhiro Umetani, Eiji Hiraki

    IEEE International Symposium on Industrial Electronics   2021-June   1 - 5   2021年

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    掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Gallium-nitride-field-effect transistors (GaN-FETs) are expected as a key component to the power density improvement of switching power converter for electric vehicles (EVs) because of their low on-resistance and fast switching capability. It is well known that the switching loss is influenced by the drain inductance, which is the parasitic inductance of the power loop, and can be minimized in principle by an appropriate design of the drain inductance. However, in switching power converters using Si-based power devices such as the Si-MOSFET and the Si-IGBT, it is usually difficult to design the drain inductance so that the switching loss minimizes because an appropriate drain inductance becomes too large, thus resulting in large surge voltages of the switching device. On the other hand, this may not be the case when using the GaN-FETs because the inductance that can minimize the switching loss may become small due to the high-di/dt switching. Therefore, the purpose of this study is to show the feasibility of the parasitic drain inductance design that the switching loss of the GaN-FET in the bridge circuit can be minimized while keeping the surge voltage of the GaN-FET within acceptable limits. The appropriateness of this insight is verified by simulation.

    DOI: 10.1109/ISIE45552.2021.9576373

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    その他リンク: https://dblp.uni-trier.de/db/conf/isie/isie2021.html#AbeIHUH21

  • Autonomous Resonant Frequency Tuning Controller for Repeater Resonator in Resonant Inductive Coupling Wireless Power Transfer System.

    Akihiro Konishi, Kazuhiro Umetani, Masataka Ishihara, Eiii Hiraki

    IEEE International Symposium on Industrial Electronics   2021-June   1 - 8   2021年

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    掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    The resonant inductive coupling wireless power transfer technique (RIC-WPT) is emerging as a promising wireless power transfer method for small mobile devices with comparatively high-power transfer capability and good efficiency. However, the performance of the RIC-WPT system is severely deteriorated by the resonant frequency detuning of the transmitter, repeater, and receiver resonators, which can be naturally caused by the manufacturing tolerance and the aging effect of these resonators. Particularly, the detuning of the repeater resonator tends to severely affect the performance due to its high-quality factor, which should be solved for practical application of RIC-WPT technology. This paper addresses this difficulty by proposing an autonomous resonant frequency tuning controller circuit for the repeater resonator. The controller tunes the resonant frequency of the repeater resonator to the operating frequency of the inverter, driving the transmitter, without an external power supply and wireless communication with the inverter controller, which restricts the freedom of the installation location and therefore preferably be avoided in the wireless power transfer system. The operating principles of the proposed controller were confirmed by the circuit simulator, supporting the feasibility of the proposed controller.

    DOI: 10.1109/ISIE45552.2021.9576268

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    その他リンク: https://dblp.uni-trier.de/db/conf/isie/isie2021.html#KonishiUIH21

  • Strategy of Topology Selection Based on Quasi-Duality Between Series–Series and Series–Parallel Topologies of Resonant Inductive Coupling Wireless Power Transfer Systems

    Masataka Ishihara, Kazuhiro Umetani, Eiji Hiraki

    IEEE Transactions on Power Electronics   35 ( 7 )   6785 - 6798   2020年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Institute of Electrical and Electronics Engineers ({IEEE})  

    Series-series (SS) and series-parallel (SP) topologies are widely used in resonant inductive coupling wireless power transfer systems for various applications. However, the selection of an appropriate topology to achieve higher output power or higher efficiency is typically difficult because design optimization of the circuit parameters (e.g., characteristic impedance, load resistance, and mutual inductance) for each topology is generally separately discussed using different equivalent circuits with multiple resonance modes. Therefore, the purpose of this study involves proposing a simple strategy to select an appropriate topology. The proposed strategy is based on quasi-duality between the SS and SP topologies that are elucidated from the novel equivalent circuits derived using Lagrangian dynamics. Based on the quasi-duality, the output power and efficiency of the SP topology are calculated via the equivalent circuit of SS topology. Thus, the quasi-duality offers a simple comparison between the SS and SP topologies. The proposed strategy selects an appropriate topology by comparing only the equivalent ac load resistance, which is the ac resistance including the rectifying circuit and the load resistance, the characteristic impedance, and the ac load resistance that achieves the maximum efficiency ormaximum output power of the SS topology. Experiments verify the appropriateness and effectiveness of the proposed strategy.

    DOI: 10.1109/TPEL.2019.2956732

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  • Optimization of Common Source Inductance and Gate-Drain Capacitance for Reducing Gate Voltage Fluctuation after Turn-off Transition

    Yusuke Hatakenaka, Kazuhiro Umetani, Masataka Ishihara, Eiji Hiraki

    2020 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)   3155 - 3162   2020年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Next-generation switching devices as GaN-FETs are recently emerging as promising switching devices capable of extremely high-speed switching. High-speed switching enables the high-frequency operation of the power converters, which can reduce the size of the passive components. However, highspeed switching can induce the resonance between the parasitic capacitance of the switching device and the parasitic inductance of the circuit board wiring, which appears as the gate voltage fluctuation at the switching. Particularly, GaN-FETs tend to have comparatively low gate threshold voltage and therefore are susceptible to the false turn-on, which is caused by the gate voltage fluctuation in the switching device just after the turn-off transition. For preventing this phenomenon, this paper analytically investigates the design requirement of these parasitic parameters to reduce the gate voltage fluctuation after the turn-off transition. As a result, the optimal ratio of the gate-drain capacitance and the common source inductance is elucidated to be the key to minimize the gate voltage fluctuation. The simulation and the experiment supported that the optimal design of this ratio can reduce the gate voltage fluctuation, supporting the usefulness of this novel insight for preventing the false turn-on.

    DOI: 10.1109/ECCE44975.2020.9236428

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  • Multiple-Transmitter Achieving Load-Independent Transmitter Current and Compensation of Cross-Interference Among Transmitters for Wide Charging Area Wireless Power Transfer Systems

    Kodai Matsuura, Masataka Ishihara, Akihiro Konishi, Kazuhiro Umetani, Eiji Hiraki

    2020 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)   5474 - 5481   2020年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Recently, a resonant inductive coupling wireless power transfer (RIC-WPT) system with multiple transmitters is emerging as a promising power supply method for household appliances, mobile devices, and wearable devices dispersedly placed in a wide area. However, the multiple-transmitter often suffers from an unstable operation of an inverter, feeding AC current to the transmitter coil, due to the cross-interference (i.e., cross-coupling) among the transmitters. When the cross-interference occurs, the inverter may not achieve high power factor and soft switching, which damages the power density and reliability of the multiple-transmitter. Therefore, this paper proposes a multiple-transmitter, including its controller, that can compensate for the effect of the cross-interference. In the proposed multiple-transmitter, each transmitter has a simple switching circuit that can automatically cancel the induced voltage due to the cross-interference with only simple control. Furthermore, the proposed multiple-transmitter also achieves a load-independent transmitter current by the control of the input voltage of the inverter, which results in a stable magnetic field regardless of load variation. Experiments verify the effectiveness and appropriateness of the proposed multiple-transmitter.

    DOI: 10.1109/ECCE44975.2020.9235430

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  • Receiving-coil structure reducing stray AC resistance for resonant coupling wireless power transfer

    Kazuhiro Umetani, Toru Honjo, Takahiro Koyama, Masataka Ishihara, Eiji Hiraki

    IET POWER ELECTRONICS   12 ( 9 )   2338 - 2344   2019年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:INST ENGINEERING TECHNOLOGY-IET  

    Resonant inductive coupling wireless power transfer is widely known to be a possible convenient power supply method for the small mobile apparatus. However, the limited receiving-coil size tends to lower the efficiency and limit the output power owing to the small mutual inductance and comparatively large stray alternating current (AC) resistance of the receiving-coil. This study mitigates this issue by proposing a novel receiving-coil structure. This proposed structure comprises a coil and a drum core with a thin axis. The coil is wound on the axis to form a single winding layer. The proposed structure can reduce stray AC resistance by suppressing the proximity effect and reducing the wire length without deteriorating the mutual inductance significantly. Therefore, better efficiency and larger output power can be achieved. Simulations and experiments were performed to verify the proposed structure. Consequently, both simulations and experiments supported the reduction in AC resistance compared to the conventional structure. Furthermore, the experiment revealed improvements by the proposed structure in both efficiency and output power. These results support the effectiveness of the proposed structure for wireless power transfer to small mobile apparatus.

    DOI: 10.1049/iet-pel.2018.5358

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  • Automatic Active Compensation Method of Cross-Coupling in Multiple-receiver Resonant Inductive Coupling Wireless Power Transfer Systems

    Masataka Ishihara, Keita Fujiki, Kazuhiro Umetani, Eiji Hiraki

    2019 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)   4584 - 4591   2019年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    The ability to charge to multiple receivers simultaneously with a single transmitter is one of the advantages of resonant inductive coupling wireless power transfer (RICWPT) technologies. However, in multiple-receiver RIC-WPT systems, each receiver often suffers from the magnetic coupling among receivers, i.e., cross-coupling. The cross-coupling not only complicates the control of the receivers but also significantly decreases the output power of each receiver. Hence, the purpose of this paper is to propose a compensation method of the influence due to the cross-coupling. To achieve this purpose, we first analyze the requirement to compensate for the influence of the cross-coupling. As a result, we reveal that it is necessary to control the phase of the current in all the receiver to be orthogonal to the phase of the transmitter current. Then, we propose the method to adjust the current phase of each receiver automatically to the desired phase by using only the phase information of the transmitter current, which results in the full compensation of the influence due to the cross-coupling. Furthermore, the proposed method also compensates for the influence of a detuning of the resonant frequency of each receiver due to the natural tolerance. Experiments of a two-receiver RIC-WPT system successfully verify the effectiveness of the proposed method.

    DOI: 10.1109/ECCE.2019.8913279

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  • Experimental Verification of Impedance Matching Method for Repeater to Improve Spatial Freedom of 6.78 MHz Resonant Inductive Coupling Wireless Power Transfer Systems

    Keita Fujiki, Masataka Ishihara, Kazuhiro Umetani, Eiji Hiraki

    2019 21ST EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE '19 ECCE EUROPE)   2019年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Placing a repeater, which relays the magnetic field from the transmitter to the receiver, is promising as a method to increase the spatial freedom of resonant inductive coupling wireless power transfer systems (RTC-WPT) working at 6.78MHz. However, the capability of the repeater is often affected by a frequency splitting phenomenon. When this phenomenon occurs, the resonance in the repeater becomes sufficiently small at a fixed operating frequency and make it difficult to improve the spatial freedom. To solve this problem, we apply an impedance matching method using simple switching circuits to the 6.78 RTC-WPT system with the repeater. Then we carry out experiments to verify the effectiveness of the impedance matching method. The experimental results show that the repeater improves the spatial freedom of the 6.78 MHz RTC-WPT regardless of the frequency splitting phenomenon.

    DOI: 10.23919/EPE.2019.8915171

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  • Automatic Resonance Frequency Tuning Method for Repeater in Resonant Inductive Coupling Wireless Power Transfer Systems

    Masataka Ishihara, Kazuhiro Umetani, Eiji Hiraki

    2018 INTERNATIONAL POWER ELECTRONICS CONFERENCE (IPEC-NIIGATA 2018 -ECCE ASIA)   1610 - 1616   2018年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Intermediate resonator (repeater) in resonant inductive coupling wireless power transfer (RIC-WPT) systems can increase the transmission distance between the transmitting and receiving coils. The induced current in the repeater is easily affected by the frequency splitting phenomenon because the quality factor (Q-factor) of the repeater is generally as high as several hundreds. If this phenomenon occurs, induction of large current is often difficult in the repeater because the one peak characteristic of the induced current is no longer expected and the single peak of resonance splits into multiple peaks which shift the resonant frequency corresponding to the circuit parameters. In this paper, we approach this difficulty by applying an auxiliary circuit to the RIC-WPT system with the repeater. As a result, under the fixed operating frequency, the induced current in the repeater can be kept large even if the frequency splitting phenomenon occurs. The effectiveness of proposed system was supported by the simulation and experiment.

    DOI: 10.23919/IPEC.2018.8507768

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  • Impedance Matching to Maximize Induced Current in Repeater of Resonant Inductive Coupling Wireless Power Transfer Systems

    Masataka Ishihara, Kazuhiro Umetani, Eiji Hiraki

    2018 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)   6194 - 6201   2018年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Intermediate resonators (repeaters) of resonant inductive coupling wireless power transfer systems can improve the transmission distance as well as the output power. However, frequency bandwidths in which the repeater can operate effectively are very narrow because the repeater usually has a high quality-factor. Furthermore, these frequency bandwidths shift for the following two factors. The first factor is the intensity of the magnetic coupling between the repeater and the other resonator. The second factor is the variation in the natural resonance frequency of the resonators due to a production error, temperature characteristic, and aging degradation. Therefore, the repeater is not practical because the repeater requires accurate adjusting of the circuit parameters every time according to the various conditions. To address this problem, we propose an impedance matching method for the repeater. The proposed method can maximize the induced current in the repeater in wide frequency bandwidth regardless of the variations in the intensity of the magnetic coupling and the natural resonance frequency. Therefore, the proposed method can realize the repeater which can stably improve the performance of the wireless power transfer. Experiment and simulation successfully verified the effectiveness of the proposed method as well as the appropriateness of the theoretical analysis.

    DOI: 10.1109/ECCE.2018.8557827

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  • Improving Robustness Against Variation in Resonance Frequency for Repeater of Resonant Inductive Coupling Wireless Power Transfer Systems

    Masataka Ishihara, Shoma Ohata, Keita Fujiki, Kazuhiro Umetani, Eiji Hiraki

    2018 20TH EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE'18 ECCE EUROPE)   2018年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Intermediate resonators (repeaters) for resonant inductive coupling wireless power transfer have been widely studied as a method of improving not only the transmission distance but also the output power. For the repeater to operate effectively, it is needed to induce a large current in the repeater to enhance the magnetic field far from a transmitting resonator. However, it is often difficult to induce a large current in the repeater due to frequency splitting phenomenon. This phenomenon easily occurs when the resonator having high quality factor such as the repeater is used. The frequency characteristic of the induced current in the repeater has multiple peaks when the frequency splitting phenomenon occurs. In addition, these multiple peaks shift according to slight variation in the parameters of the coil and the capacitor that constitute the resonator. This slight variation is easily caused by production error, temperature characteristic, and aging degradation of the coil and the capacitor. The induced current in the repeater is significantly decreased by the slight variation in the parameters, namely, the slight variation in the resonance frequency. Therefore, the repeater has low robustness against variation in the resonance frequency. To address these difficulties, we apply an auxiliary circuit to the repeater. The auxiliary circuit can dynamically adjust a phase of the induced current in the repeater, namely, the resonance frequency without complicated control. As a result, a large induced current can be maintained even if the frequencies corresponding to the peaks shift. Consequently, we can provide the repeater having a stable characteristic against the variation in the resonance frequency. The effectiveness of the repeater applied the auxiliary circuit and the appropriateness of analysis results are supported with simulation and experimental results.

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  • Magnetic Structure of Close-Coupled Inductors to Improve the Thermal Handling Capability in Interleaved DC-DC Converter

    Thai Hoang Chuong, Shota Kimura, Daigoro Ebisumoto, Mostafa Noah, Masataka Ishihara, Masayoshi Yamamoto, Jun Imaoka, Wilmar Martinez

    2017 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)   2017-January   205 - 210   2017年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Interleaved DC-DC converter employing close-coupled 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

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  • Elucidation of Quasi-Duality between Series-Series and Series-Parallel Topologies of Resonant Inductive Coupling Wireless Power Transfer Systems

    Masataka Ishihara, Kazuhiro Umetani, Eiji Hiraki

    2017 IEEE 12TH INTERNATIONAL CONFERENCE ON POWER ELECTRONICS AND DRIVE SYSTEMS (PEDS)   2017-December   674 - 679   2017年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Series-Series (SS) and Series-Parallel (SP) topologies are widely utilized in practical resonant inductive coupling wireless power transfer (RIC-WPT) systems owing to their simple circuit configurations. Conventionally, design optimization of the circuit parameters of these topologies were investigated separately, because these topologies are expressed by different equivalent circuits. However, analysis of these equivalent circuits is generally complicated due to the multiple resonant modes contained in the operation, which may cause difficulty in comparing the performance between the SS and SP topologies after design optimization of these topologies. This difficulty may prevent elucidating the methodology to select an appropriate topology that offers better output power or efficiency after design optimization. The purpose of this paper is to suggest a selection methodology of the SS and SP topologies by elucidating a novel insight that these topologies have the quasi-duality relation, in which the SP topology works approximately as the dual of the SS topology. This insight enables to share the analysis results between the topologies. As a result, both of these topologies were found to be expressed by a same novel equivalent circuit. Furthermore, the only difference between the SS and SP topologies were found to be the equivalent load resistance of this equivalent circuit, thus reducing the topology selection into selection of preferable load resistance. The appropriateness of the quasi-duality relation and the resultant equivalent circuit was successfully confirmed by the simulation and the experiment.

    DOI: 10.1109/PEDS.2017.8289248

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  • Simple Self-Driven Synchronous Rectifier for Resonant Inductive Coupling Wireless Power Transfer

    Takahiro Koyama, Toru Honjo, Masataka Ishihara, Kazuhiro Umetani, Eiji Hiraki

    2017 IEEE INTERNATIONAL TELECOMMUNICATIONS ENERGY CONFERENCE (INTELEC)   2017-October   363 - 368   2017年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Resonant inductive coupling wireless power transfer (RIC-WPT) is attracting attention as a convenient power supply method to small mobile apparatus. The efficiency and the power transfer capability of RIC-WPT has been known to be profoundly dependent on the quality factor of the receiving resonator. However, the quality factor of the receiving resonator tends to be deteriorated because of the conduction loss at the diode rectifier, particularly for low output voltage applications. In order to improve the efficiency and the power transfer capability, this paper propose a novel simple synchronous rectifier, which can reduce the conduction loss. The proposed rectifier has simple circuit configuration, which contributes to straightforward application to the wireless power transfer to small mobile apparatus with limited installation space. Experiment was carried out to verify the operation principle of the proposed rectifier. As a result, the proposed rectifier revealed successful suppression of the conduction loss. In addition, the experimental wireless power transfer system verified successful improvement in the rectification efficiency, supporting usefulness of the proposed rectifier for practical applications of the RIC-WPT for small mobile apparatus.

    DOI: 10.1109/INTLEC.2017.8214163

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  • Analytical Investigation of Interleaved DC-DC Converter using Closed-Coupled Inductor with Phase Drive Control

    Daigoro Ebisumoto, Shota Kimura, Kimihiro Nanamori, Mostafa Noah, Masataka Ishihara, Jun Imaoka, Masayoshi Yamamoto

    2017 IEEE INTERNATIONAL TELECOMMUNICATIONS ENERGY CONFERENCE (INTELEC)   2017-October   526 - 529   2017年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    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 DCDC converter using coupled inductor with phase drive control (PDC) is analyzed. In addition, defensive method of this method.

    DOI: 10.1109/INTLEC.2017.8214190

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  • Quasi-duality between SS and SP topologies of basic electric-field coupling wireless power transfer system

    M. Ishihara, K. Umetani, H. Umegami, E. Hiraki, M. Yamamoto

    Electronics Letters   52 ( 25 )   2057 - 2059   2016年12月

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    掲載種別:研究論文(学術雑誌)  

    Series-series (SS) topology and series-parallel (SP) topology of the electric-field coupling wireless power transfer system are widely utilised for practical applications. However, selecting the appropriate circuit topology, which maximise the output power by design optimisation, is often difficult, because these circuit topologies are generally analysed using different circuit models. This difficulty by analysing novel equivalent circuits for SS and SP topologies is addressed. As a result, the output power of SP topology is found to be approximated by that in SS topology with transformed load impedance. This result can offer a simple strategy for topology selection as well as design optimisation.

    DOI: 10.1049/el.2016.1253

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  • Design of a Four-Phase Interleaved Boost Circuit with Closed-Coupled Inductors

    Daigoro Ebisumoto, Masataka Ishihara, Shota Kimura, Wilmar Martinez, Mostafa Noah, Masayoshi Yamamoto, Jun Imaoka

    2016 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)   2016年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    In this paper, a novel magnetic structure suitable for boost converters is proposed. Multi-phase interleaved method using coupled-inductor has gained attention in electric powertrains for electric, hybrid and fuel cell vehicles in order to achieve high power density. In fact, a four-phase boost converter using coupled inductor is used in the drive system of the Honda CLARITY. In particular, magnetic coupling method is used in coupled inductors, Loosely-Coupled Inductors (LCI) and Closed-Coupled Inductors (CCI). This study is focused on these methods, especially using the CCI. This paper presents a design method of a closed-coupled inductors using generic cores for a four-phase interleaved boost converter. In addition a comparison between the proposed topology with other conventional non-coupled methods is carried out. Furthermore, the evaluation of miniaturization is studied. As a result, the proposed method can achieve a huge reduction in the core volume and mass.

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  • Basic Experiment Study on Misalignment Characteristic of Electrical Resonance Coupling Wireless Power Transfer

    Hirokatsu Umegami, Masataka Ishihara, Fumiya Hattori, Mitsuru Masuda, Masayoshi Yamamoto

    2015 IEEE INTERNATIONAL TELECOMMUNICATIONS ENERGY CONFERENCE (INTELEC)   2015年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    This paper describes lateral misalignment characteristics of electrical resonance coupling wireless power transfer (ERC-WPT) from experimental points of view. A dead zone is an important factor for ERC-WPT because ERC-WPT cannot transfer electric power in the zone. Electrical coupling units that are composed of 2 electrodes lined up laterally have a dead zone. The dead zone exists near outer edge areas of the electrodes and certain distant areas.

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  • Analysis and Design of Passive Components for Interleaved Flyback Converter with Integrated Transformer

    Masataka Ishihara, Shota Kimura, Wilmar Martinez, Masayoshi Yamamoto

    2015 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)   5902 - 5909   2015年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Flyback switch mode power supplies have been widely used in low-power applications, such as DC/DC converters, solar micro-inverters and LED drivers. However, flyback converters have several problems related to the volume of the output capacitor as well as high output voltage noise; this is produced by the discontinuous output current. Consequently, interleaved operation with parallel connection on the secondary side can reduce the output current ripple compared with the single-phase flyback converter. Nevertheless, besides the output capacitor, the interleaved operation is unsuitable for transformers if it is desired to obtain light weight and compact performance. To address this problem, the interleaved flyback converter with integrated transformer has been proposed for achieving miniaturization of the output capacitor and transformers. There are mainly two types of the proposed flyback converter with integrated transformer: Parallel and Series types. These two types are categorized based on the connection on the primary side. Nevertheless, quantitative comparison of the volume and power loss has not been analyzed yet. Moreover, the design method of the integrated transformer also has not been conducted with clarity. Hence, in this paper, in order to provide a guide for the design of an interleaved flyback converter for achieving high power density, we analyze the quantitative volume and power losses of the integrated transformer and the input capacitor. Finally, this paper shows some experimental results that validate the appropriateness of the design method for the integrated transformer.

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  • Interleaved Active Clump Forward Converter with Novel Integrated Magnetic Components

    Shota Kimura, Shogo Aoto, Masataka Ishihara, Jun Imaoka, Masayoshi Yamamoto

    2015 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)   6029 - 6036   2015年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    This paper proposes Series Input Parallel Output (SIPO) interleaved Active Clump Forward (ACF) converter with novel integrated magnetic components that may achieve high power density. The proposed converter consists of two ACF converters in SIPO connection to share the input voltage and output current. The natural magnetizing reset can be realized by the active clump circuit. The SIPO connection distributes the voltage stress of the primary side switches and the thermal stress of the output rectifiers and filters. The interleaved PWM operation also diminishes the current ripple in the output capacitor to reduce the size the output filter. In addition, the integrated magnetic components are used for inductors and transformers in the proposed converter to realize size-reduction of the magnetic components. Therefore, this converter is suitable for high input voltage and high output current applications such as dc-dc converters EVs and HEVs. In this paper, the operation principle and the theoretical analysis for the proposed integrated magnetic components are presented. Following we use core models for the integrated magnetic components, and the superiority of them in term of reducing the size and losses in the magnetic components is demonstrated clearly through comparison with a conventional single ACF converter and an conventional SIPO interleaved ACF converter. As a result, it is cleared that the proposed converter is effective for size-reduction and low-losses of the magnetic components under the same conditions. To verify the theoretical results, the experiments using a 500 W output prototype are conducted.

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  • Mid-range kHz Electric Resonance Coupling Wireless Power Tranfser

    Hirokatsu Umegami, Masataka Ishihara, Fumiya Hattori, Mitsuru Masuda, Masayoshi Yamamoto, Kazuhiro Umetani

    2015 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)   3197 - 3202   2015年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    This paper describes mid-range electrical resonance wireless power transfer in kHz range. Wireless power transfer using electrical field is minor since this method is understood only for close-range applications. However, our experimental units, the resonance frequency of which is 85 kHz, achieved 180 mm distance power transmission by vector network analyzer (VNA) measurement while keeping peak efficiency 68 %. In case of frequency response analyzer (FRA) measurement, the units can transfer power the most to the load at 300 mm but the efficiency is low. The closer the distance between the units, the better the efficiency is.

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  • A Capacitor-less Gate Drive Circuit Using Two Parasitic Capacitors Suitable for Non-Insulating-Gate GaN FETs

    Masataka Ishihara, Fumiya Hattori, Hirokatsu Umegami, Masayoshi Yamamoto

    2014 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)   3212 - 3218   2014年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    New semiconductor devices such as Silicon Carbide (SiC) and Gallium Nitride (GaN) are very attractive for improving converter efficiency and power density in power electronics. Especially, GaN FETs are promising devices for the high speed switching and good cost performance due to being able to use silicon wafer, so that we focus on GaN FETs. There are two types of GaN FETs, and one, non-isolated GaN FETs, has a diode structure on the gate-to-source, and another, isolated GAN FETs, doesn't have this feature. Non-isolated GaN FETs show better performance than isolated GaN FETs in terms of withstand voltage, allowable current, and other parameters. However, simple gate circuits used for MOS FET cannot be applied. Hence, many gate drive circuits for non-isolated GaN FETs are proposed. In this paper, we proposed a novel gate drive circuit for a non-isolated GaN FET, which uses two parasitic capacitors of the switches in the gate drive circuit. The experiment for the proposed gate drive circuit is executed with a simple test circuit. Furthermore, drive loss is analyzed and compared with a previous proposed gate drive circuits. Furthermore, we develop the theoretical equations for the gate drive loss and verify them experimentally. The drive and reverse conduction losses of the proposed capacitor-less gate drive circuit are compared with dividing capacitor gate drive circuit and previous capacitor-less gate drive circuits.

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