近年來因應商品需求，電源設計的功率密度要求越來越高，高頻化演變成一種趨勢，而氮化鎵半導體的出現，為高頻應用帶來新的突破。隨著氮化鎵技術穩定發展，元件可靠度也較以往高，對於不同需求的規格提供了更多選擇，在應用上也更為廣泛。本論文將氮化鎵高電子遷移率電晶體使用在串聯諧振轉換器中，以期提高操作頻率，降低切換損耗，並在二次側增加降壓式轉換器達成穩壓輸出目的。使用平板變壓器取代一般繞線架繞製的變壓器，達成薄型化設計要求。本文實作一台 1 MHz / 500 W 轉換器，實驗結果證明與理論設計相符合。

The requirement for power density becomes higher and higher to fit the market demand of power supplies. The current trend is towards high-frequency design and operation because Gallium-nitride (GaN) transistors bring a new breakthrough in high-frequency applications. Due to the steady development of GaN technology, the device reliability is highly increasing. More device specifications are also available for various applications. This thesis aims to study the GaN transistors applied to a series resonant converter for switching loss reduction under high-frequency operation. A buck converter is added as the post-stage circuit to regulate output voltage. A planar transformer is designed to replace the conventional transformer for realizing low-profile converter. A 1 MHz/ 500 W half-bridge series resonant converter is implemented and tested. The experimental results are shown to verify theoretical analysis.

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