傳統的硬切式切換電源供應器，對電磁效應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脈波調變轉換器，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1KW以下的電源供應系統。本論文為設計一種具有同步整流倍流輸出的非對稱半橋轉換器，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倍流的功率開關元件來取代已往的蕭特基二極體，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進行簡易模擬分析，之後說明電路設計考量，並實作出一台200W樣品加以實測比較，為迎合市場產品對體積縮小的需求，並證明該電路的小型化可能性，故針對整機體積大小有所規範在12.8cm(L) x 7.6cm(W) x 4.7cm(H)的大小內，零件大小的選用亦受其影響，並將電路以SMD零件製作出來。

Existing hard-switching power supply produces electromagnetic interference and inadequate efficiency. By using the Zero-Voltage-Switching (ZVS) asymmetrical half-bridge (AHB) Pulse-Width-Modulation (PWM) converter, switching losses and noises can be reduced, thus increasing the operating frequency and circuit efficiency.
An asymmetrical half-bridge has the following advantages: simple structure, lower switches’ voltage rating, ZVS, and its appropriateness for application in higher than 1kW power supply systems. This thesis focuses on the design of an asymmetrical half-bridge converter with synchronous current-doubler rectification, and with its front-end part added with a power factor corrector (PFC). The power MOSFETs are utilized instead of Schotky diodes for the secondary-side current-doubler rectification. Therefore, the efficiency of the low-voltage high-current converter can be increased.
The basic principle of the asymmetrical half-bridge converter is analyzed, several circuit techniques are discussed, and circuit simulations using SIMETRIX are implemented. Then a prototype of the 200W converter is realized and the experimental results verify the theoretical and simulation analysis. In order to meet the size-minimization requirement, the size of this converter is optimized down to 12.8cm (L)、7.6cm (W) and 4.7cm (H), with Surface Mounted Devices (SMD) adopted.

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