2024/12/24 更新

写真a

イシハラ マサタカ
石原 將貴
Ishihara Masataka
所属
環境生命自然科学学域 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 )

研究分野

  • ものづくり技術(機械・電気電子・化学工学) / 電力工学  / パワーエレクトロニクス

 

論文

  • Effectiveness Study of Streamlined Fin with Low-Pressure Loss to Improve Heat Dissipation Performance of Heat Sink

    Hiroki Seto, Kazuhiro Umetani, Masataka Ishihara, Eiji Hiraki

    INTELEC, International Telecommunications Energy Conference (Proceedings)   2024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)  

    In recent years, with the advent of next-generation semiconductors, circuit boards have been miniaturized to accommodate higher frequencies. Miniaturization also means increased heat density. Further miniaturization of switching converters and inverters requires heat sinks that provide excellent heat dissipation performance in a limited volume, and the cylindrical fin type has been commonly used as a heat sink structure. However, cylindrical fin type heat sinks have the problem of large pressure loss when refrigerant passes through them. To solve this problem, streamlined fins and elliptical fin have been proposed to replace cylindrical fin type heat sinks. Although many studies have compared the heat dissipation performance of elliptical and cylindrical fin, few studies have compared it with that of streamlined fins. Therefore, in this paper, a heat sink structure with multiple streamlined fins is constructed. The change in pressure loss due to the change in fin shape and the resulting heat dissipation performance were verified by thermo-fluid analysis and actual device verification, and compared with the conventional cylindrical fin type. As a result, it was confirmed that the streamlined fin structure slightly increases thermal resistance and significantly reduces pressure loss. Comparison of the thermal resistance-pressure loss characteristics showed that the streamlined fins can sufficiently reduce the pressure loss for the same thermal resistance value. In the case of forced air cooling, the heat dissipation performance of the streamlined fins could be expected to improve with fan selection.

    DOI: 10.1109/INTELEC60315.2024.10679005

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  • GaN-HEMT Power Module of Aluminum-Clad Printed Circuit Boards for Small Power Loop Inductance and High Cooling Performance

    Kazuhiro Umetani, Yu Takehara, Masataka Ishihara, Eiji Hiraki

    IEEE Transactions on Power Electronics   39 ( 10 )   12047 - 12052   2024年

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    掲載種別:研究論文(学術雑誌)  

    Gallium nitride high-electron-mobility transistors (GaN-HEMTs) are promising for high-speed switching capability and small on-resistance. However, large turn-off surge and limited cooling capability due to their small chip size are hindering their application to high power conversion. To solve these problems, this letter proposes a novel power module structure with small power loop inductance and small thermal resistance based on recently proposed power module structures. The proposed structure comprises two aluminum-clad printed circuit boards (PCBs) that sandwich the GaN-HEMT devices. These PCBs generate eddy current inside the aluminum base to reduce power loop inductance and provide an additional thermal path to improve the cooling performance. These features were tested by an experiment that compared 3-kW half-bridge prototype power modules of the proposed and conventional structures. As a result, the proposed structure revealed power loop inductance of 1.4 nH and thermal resistance of 0.72 K/W, which corresponded to a reduction by 53% and 20%, respectively, compared to the conventional structure.

    DOI: 10.1109/TPEL.2024.3431615

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  • Non-Isolated Interleaved High Step-Down DC-DC Converter with Reduced Switched Capacitor Stages and Automatic Current Sharing

    Kazuhiro Umetani, Fumie Ishitani, Taira Shirahase, Masataka Ishihara, Eiji Hiraki

    INTELEC, International Telecommunications Energy Conference (Proceedings)   2024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)  

    A high-voltage dc power supply system is an attractive solution for reducing the system cost and improving efficiency. This system needs compact but high-efficiency high-step-down converters to exploit the benefits. This paper proposes a novel converter for a better candidate than traditional converters. The proposed converter is a non-isolated high step-down converter utilizing the switched capacitor technology. Compared to conventional similar topologies, the number of switched capacitor stages can be reduced, enabling the compact converter design. Furthermore, this converter has interleaved output, which can downsize the magnetic devices. The current of the interleaved output is automatically balanced without special control, enabling simple controller implementation. These features were successfully verified by the experiment.

    DOI: 10.1109/INTELEC60315.2024.10678985

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  • Compact Hardware Implementation of Power Factor Control for LLC converter with Event-Driven-Timer Based Digital Controller

    Toshiyuki Zaitsu, Yuto Yoshimura, Kazuhiro Umetani, Masataka Ishihara, Eiji Hiraki, Kazuhiro Horii

    Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC   2015 - 2020   2024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)  

    LLC converter is well known as an attractive topology however, it suffers from system stability degradation depending on load conditions, which has limited use for many applications. The previous study addressed this problem by proposing a novel control, called the 'power factor (cosθ) control', which adjusts the phase difference θ between the inverter voltage and primary current of the LLC half-bridge instead of adjusting the operating frequency. However, the previous prototype required a complicated analog circuit for the control, which appeared difficult for practical application. This paper aims at achieving a compact implementation of the control circuit. A special "Event-Driven-Timer Based"digital control is adopted which can automatically track the timing and frequency by detecting the resonant trigger point and turning on the main switch. The prototype board exhibited great size reduction of the control circuit as well as excellent controllability, supporting promising features for practical application.

    DOI: 10.1109/APEC48139.2024.10509360

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  • Feasibility of Active Reactance Compensator for Autonomously Maximizing Repeater Coil Current of Wireless Power Transfer System Against Variations in Resonant Frequency and Magnetic Coupling Intensity

    Masataka Ishihara, Kazuhiro Umetani, Akihiro Konishi, Eiji Hiraki

    IEEE Access   12   98175 - 98188   2024年

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    掲載種別:研究論文(学術雑誌)  

    In resonant inductive coupling wireless power transfer systems, a repeater resonator is crucial in expanding the charging area, enabling efficient power supply to receivers, such as small Internet of Things (IoT) devices sparsely distributed in a wide area. However, the repeater current is highly susceptible to deviations in resonance frequency due to manufacturing tolerance and aging, as well as to the magnetic coupling between the transmitter and repeater coils, potentially leading to insufficient amplitude. Consequently, the magnetic field generated by the repeater decreases and the receiver may be difficult to obtain sufficient power from the transmitter via the repeater. To address this problem, this paper proposes a wireless power transfer system with active reactance compensators incorporated in the repeater and the transmitter. The proposed system can equivalently adjust the resonant frequencies of the transmitter and repeater to stably maximize the repeater coil current regardless of the variations in the resonant frequency and the magnetic coupling intensity. Experiments successfully verify that the proposed system can provide a more stable and larger repeater current and output power than the conventional system against the variations in the magnetic field intensity and the resonant frequency of the repeater, validating the feasibility of the proposed system for practical utilization of the repeater in expanding the charging area.

    DOI: 10.1109/ACCESS.2024.3428864

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MISC

  • 6.78MHzワイヤレス給電システム用自動リアクタンス調整回路における制御信号伝搬遅延の固定時間補償の課題抽出

    西尾颯真, 石原將貴, 梅谷和弘, 平木英治

    電気学会研究会資料(Web)   ( SPC-24-001-017/MD-24-001-017 )   2024年

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  • イベントドリブン型デジタルコントローラによるLLCコンバータの力率制御回路の小型化

    吉村勇人, 財津俊行, 梅谷和弘, 石原將貴, 平木英治, 堀井一宏

    電気学会研究会資料(Web)   ( HCA-24-010-017 )   2024年

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  • 自動電流分割機能を持つ二相インターリーブ非絶縁型高降圧コンバータ

    石谷文絵, 石原將貴, 梅谷和弘, 平木英治

    電気学会研究会資料(Web)   ( SPC-24-044-050.052-054/MD-24-044-050.052-054 )   2024年

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  • ケルビンソース端子を備えたパワーデバイスのコモンソースインダクタンスの測定

    小橋孝太郎, 小西晃央, 石原將貴, 梅谷和弘, 平木英治

    パワーエレクトロニクス学会誌   48   2023年

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  • 熱抵抗と圧力損失を抑えた強制空冷型ヒートシンクにおける板状フィンの探索

    高力斗亜, 平木英治, 梅谷和弘, 石原將貴

    電気学会全国大会講演論文集(CD-ROM)   2023   2023年

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受賞

  • 部門奨励賞 若手奨励賞(高橋勲賞)

    2023年8月   電気学会産業応用部門  

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  • 優秀論文発表賞A

    2023年8月   電気学会産業応用部門  

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共同研究・競争的資金等の研究

  • 小型・高効率な次世代大容量電力変換器を実現する基板レイアウトの設計理論の確立

    研究課題/領域番号:22K14242  2022年04月 - 2025年03月

    日本学術振興会  科学研究費助成事業  若手研究

    石原 將貴

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    配分額:4550000円 ( 直接経費:3500000円 、 間接経費:1050000円 )

    次世代パワーデバイスであるSiC-MOSFETの誤動作の無い並列駆動の実現を目指し,本年度は,2並列接続した場合における基板レイアウトの設計理論の確立を目標に研究を進めてきた。まず,誤動作の2種類の発生パターンに着目して導出した簡単な等価回路を用いて,2並列した場合の誤動作が発生しないための条件を定式化した。その結果,2つのSiC-MOSFETが並列に接続されている場合の誤動作は,並列接続していない場合の誤動作と同様に,SiC-MOSFETの寄生容量値に応じて回路基板に潜在する寄生インダクタンスを適切に調整すれば回避できることを明らかに出来た。また,回路シミュレータPSpiceを用いて誤動作発生の有無と寄生インダクタンス値の関係を調べることで,導出した理論の妥当性を確認することに成功した。
    現在,この理論の有効性を検証するために,実際のインバータ回路を製作し,寄生インダクタンスを調整して2並列接続した場合における誤動作を回避できるかを試験中である。具体的には,ダブルパルス試験で50A程度のスイッチング試験を行い,幾つかの回路条件で誤動作の有無を検証している。その結果,おおよそ理論通りのインダクタンス値で誤動作を抑制できていることを確認できたが,まだ試験は完了しておらず,更なる回路条件下での評価が必要になっている。
    このまま2並列接続した際の誤動作を抑制する基板レイアウトの設計指針が確立できれば,より大電力アプリケーションにおいても,SiC-MOSFETの高速スイッチング動作を犠牲にすることなく,電力変換器を飛躍的に小型・高効率化できる可能性がある。

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担当授業科目

  • エネルギー・エレクトロニクス実験B (2024年度) 3・4学期  - 火3~7

  • ネットワーク工学実験B (2024年度) 3・4学期  - 火3~7

  • 専門英語B1 (2024年度) 第3学期  - 水7~8

  • 専門英語Ⅱ (2024年度) 第3学期  - 水7~8

  • 特別研究 (2024年度) その他  - その他

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