氮化鎵功率晶體為寬能隙半導體元件中切換速度最快之元件，可降低功率元件的切換損失，使轉換器操作在更高的頻率，因此其相關應用已成未來趨勢。本論文使用增強型氮化鎵功率元件於1 MHz LLC半橋諧振轉換器之研製，提高操作頻率以增加功率密度。本論文先探討LLC半橋諧振轉換器柔切之動作原理，研究寬能隙元件特性，並瞭解增強型氮化鎵功率元件的特點與驅動電路設計需求。最後，以數位訊號處理器TMS320F28035作為控制核心，研製一切換頻率操作在1MHz，輸入電壓為400 V、輸出電壓為12 V，額定輸出功率為240W之直流對直流LLC諧振轉換器，二次側並使用同步整流技術以降低導通損失提高系統效率，實驗結果驗證本轉換器在半載時最高效率可達94.1%，滿載時效率可達92.1%。

Gallium Nitride Power Transistor has the fastest switching characteristics among the wide band-gap semiconductor power devices. This feature allows the converters to reduce switching losses for operating at higher frequency. Therefore, its applications have become a recent trend. In this thesis, an 1 MHz LLC half bridge resonant converter with GaN Enhancement mode HEMT (GaN E-HEMT) is implemented. The power density of the power converter is improved with higher switching frequency, and also achieve higher efficiency with soft switching technique. The operating principle of half bridge LLC resonant converter is discussed and the characteristics and gate driver circuit requirements of the wide bandgap devices are studied. Finally, the digital signal processor, TMS320F28035, is used to realize the laboratory prototype with the input voltage 400 V, the output voltage 12 V, and rated output power 240W. The synchronous rectifier is used on the secondary side to reduce conduction loss to improve efficiency. The experimental results show that efficiency can be as high as 94.1% at 50% load and 92.1% at full load.

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