提升切換頻率來降低磁性元件以及濾波元件的大小，藉此提升產品的功率密度已是產業的趨勢。但是以往受限於矽元件的特性，大幅限制了電路的切換頻率，近來氮化鎵元件的興起使得電路可以操作於更高的切換頻率。
以高降壓比LLC型串聯諧振式轉換器的整體損耗來說，磁性元件佔了大多數，且傳統的變壓器做工複雜，不易自動化。所以本文採用矩陣式變壓器，一二次側繞組只需4層的PCB即可達成。且採用磁通抵銷的概念來有效降低鐵心的磁滯損耗，並探討不同方式的繞線配置方式對電路的影響，最後採取整流元件以及輸出電容可以直接整合在二次側繞組上的方式。最後實作出一台切換頻率1 MHz，380 V輸入轉12 V 輸出的700 W，LLC型串聯諧振轉換器，且電路體積只有39.2 cm3。

Pushing switching frequency higher to reduce magnetic components size and output rectifiers is the trend. Gallium nitride power devices are set to take over as silicon power devices reach their limits. This new material allow circuit operating in higher frequency.
For high-step-down LLC-type series resonant converters, the transformer loss dominates the whole converter loss, thus, the transformer design is very important. The traditional transformer structure is difficultly adapted to an automatic manufacturing process. This thesis use matrix transformer and flux cancellation. Therefore, one magnetic core with four-layer PCB windings is adopted. Different secondary and primary windings structure is investigated in this thesis. Finally, synchronous rectifiers and output capacitors are integrated into secondary windings. A 1MHz 380 V/12 V 700 W LLC-type series resonant converter with volume 39.2 cm3 is built to verify the proposed structure.

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