成果報告書詳細
管理番号20160000000775
タイトル*平成27年度中間年報 低炭素社会を実現する次世代パワーエレクトロニクスプロジェクト 次世代パワーエレクトロニクス応用システム開発の先導研究 SiC/GaNパワーデバイスMHz帯スイッチングDCーDCコンバータの先導研究
公開日2016/9/10
報告書年度2015 - 2015
委託先名国立大学法人信州大学 国立大学法人大阪大学
プロジェクト番号P10022
部署名IoT推進部
和文要約
英文要約Title: Research and development of SiC/GaN power device MHz switching DC-DC converter (FY2015-2016) FY2015 Annual Report
The results obtained in the fiscal year 2015 are summarized as follows.
(1)Development of carbonyl-iron powder(CIP)/epoxy composite magnetic core
A novel scheme to increase the volume resistivity of carbonyl-iron powder (CIP)/epoxy composite magnetic core was established by introducing surface oxidation of the CIP annealed in dry air. The closely packed 89 wt.%-CIP/epoxy composite magnetic core with CIP annealed at 200℃ for 6 hours exhibited the volume resistivity of 100 ohm m, which was 1500 times higher than that of composite magnetic core using as-made CIP. Though the CIP/epoxy composite magnetic core had a low relative permeability of 6 owing to the distributed air-gap (epoxy resin matrix), high frequency magnetic loss was very small due to its high volume resistivity.
(2) Development of CIP/epoxy composite magnetic core reactor/transformer for MHz power conversion
A toroidal core reactor, with a core size of 30 mm diameter×10 mm height and 14 turn winding, was fabricated using surface oxidized CIP annealed at 200℃ for 6 hours, which exhibited an inductance of 2.8 micro H and Q-factor over 200 at MHz frequency band. When the composite magnetic core was applied to a toroidal core transformer, there was an important issue on low coupling coefficient k between primary and secondary windings, typically k was about 0.97. This was owing to the leakage magnetic flux from low permeability composite core. From the magnetic field analysis, it was found that an embedded winding structure into the composite magnetic core with optimal winding layout was very effective to obtain coupling coefficient k over 0.99.
(3) Development of SiC/GaN power device MHz switching DC-DC converters
5V-1V synchronous rectifying chopper DC-DC VRM (Voltage Regulator Module) was developed using a half-bridge circuit of GaN-FET (EPC2023)/Si-SBD (V8PAN50-M3) and an embedded 3.5 turn wingding composite magnetic core reactor. The embedded winding reactor had a size of 14 mm×14 mm×7 mm, inductance of 406 nH, dc winding-resistance of 2.3 m ohm and Q-factor of 100 at 1 MHz. The developed VRM with a switching frequency of 1 MHz had a 2 cm3 volume including GaN-FET/Si-SBD half bridge, embedded winding reactor, and input/output capacitor. When 5V-1V×10A (output power;10 W), the volumetric power density was 5 W/cm3 and the power conversion efficiency was 90.6 %.
An embedded winding transformer with a size of 40 mm×40 mm×10 mm, turn ratio of 16:8, primary inductance of 17 micro H and coupling coefficient k of 0.99, was applied to 48V-12V, 500 kHz switching flyback DC-DC converter with a SiC-FET main switch (ROHM; SCT2120-AFC-ND). When 48V-12V×1A (12 W) condition, 83.5 % efficiency was obtained. By increasing permeability of magnetic core and increasing operating frequency, 90 % over efficiency will be achieved by lowering copper loss and small iron loss in the embedded winding transformer. 48V-24V LLC resonant MHz switching DC-DC converter was developed, where GaN-HEMT half bridge (GaN Systems; GS61004) was used in the primary circuit, SiC-SBD (ROHM; SCS220AJ) was used as a rectifier in the secondary circuit. A toroidal magnetic core with a size of 25 mm diameter×7 mm height was used for resonant transformer, where the fabricated transformer had a primary inductance of 300 nH, turn ratio of 6:5:5 and coupling coefficient k of 0.822 . The total volume of power conversion circuit was 22.8 cm3. When 48V-24V×5A (120 W) condition, the volumetric power density was 5.3 W/cm3 and the efficiency was 91%.
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