傳統的硬切式切換電源供應器，對電磁干擾及效率上皆產生不良影響；採用具零電壓切換特性的非對稱半橋返馳式轉換器，可降低切換開關所帶來的切換雜訊與損失，以提高電路操作頻率及效率。
非對稱半橋返馳式電路的優勢在於簡單的架構、低開關耐壓與零電壓切換的特性，適合運用在低功率的電源供應系統。本論文為設計一種具有同步整流輸出的非對稱半橋返馳式轉換器，再加入一主動功因修正轉換器做前級功因修正單元。次級側則利用同步整流的功率開關元件來取代以往的蕭特基二極體，做為改善低電壓高電流輸出應用時的轉換效率。
本論文中針對非對稱半橋返馳式轉換器的動作原理及各項技術做詳細分析與討論，並以SIMetrix進行模擬分析，並實作出一台200W雛型電路來驗證此轉換器理論分析的正確性。

Conventional hard-switching power supply presents serious electromagnetic interference (EMI) issue and a poor efficiency. By using the Zero-Voltage-Switching (ZVS) asymmetrical half-bridge (AHB) Pulse-Width-Modulation (PWM) converter, switching losses and EMI noises can be reduced. Thus, operating frequency and circuit efficiency can be effectively raised. An asymmetrical half-bridge has the following advantages: simple structure, lower switch voltage rating and soft-switching features for low power applications. This thesis focuses on the design and implementation of an asymmetrical half-bridge converter with synchronous rectification and its front-end power factor corrector (PFC). The power MOSFETs are adopted instead of Schotky diodes for the secondary rectification. The efficiency of the studied DC/DC converter with low-voltage high-current output can be increased. The operation principles of the asymmetrical half-bridge converter are analyzed and discussed in details. SIMETRIX simulations and experimental verifications for a 200W laboratory prototype are shown to verify the theoretical analysus of the studied converter.

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