本論文主要研製一具體積優化與效率平衡之串聯諧振轉換器，電路前級為操作於連續導通模式(Continuous Conduction Mode, CCM)的降壓型轉換器，將後級串聯諧振轉換器輸出電壓回授至此降壓型轉換器，利用降壓型轉換器改變工作週期的工作方式，使串聯諧振轉換器電路於各負載下，輸出電壓皆能穩壓。後級串聯諧振轉換器操作於第一諧振頻率附近，以縮小磁性元件體積，且利用零電壓切換與同步整流技術，以達到高功率密度及高轉換效率。另外，本論文提出修改半橋串聯諧振轉換器之回授控制電路，使電路達到輕載時操作在低頻，重載時操作在高頻。
本論文製作一台DC-DC電源，輸入電壓380 V、輸出電壓12 V、輸出電流25 A，能於輕載時減少切換損失，電路從輕載至滿載穩壓率在1%範圍內，並提供實驗數據和理論相互印證。

This thesis presents a series resonant converter (SRC) with volume optimization and efficiency balance. The front stage is a CCM buck converter. The output voltage of the post-stage SRC is sensed and can be regulated under full-range load conditions by adjusting the duty cycle of the buck converter. The SRC is operated around the first resonant frequency to reduce the volume of the magnetic components. Zero-voltage switching and synchronous rectification are adopted to improve the efficiency and increase the power density. In addition, a novel feedback controller is proposed in this thesis to lower the switching frequency at light loads, while raise the switching frequency at heavy loads.
A DC-DC power converter with an input voltage of 380 V, an output voltage of 12 V, and rated output current of 25 A is implemented. The switching loss at light load can be reduced with the presented control scheme. The load regulation is within 1%. Also the experimental results are provided to confirm the theoretical analysis.

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