現今許多電源轉換器產品採用功率因數修正級與直流-直流轉換器兩級串接，此兩級式架構能達到高功因，且輸入電流諧波滿足規範，但電路複雜度與元件數量較多的問題能仍需改善。
本論文使用一具功率因數修正之單級昇降壓-順向式轉換器，前級由昇降壓式轉換器修正功率因數以達到高功因，且透過其降壓功能減少兩級間的儲能電容電壓應力。後級由順向式轉換器作穩壓，所使用之變壓器不需第三繞組，以減小體積。本論文所用單級式轉換器使用模糊控制達到穩定輸出電壓功能且將電路操作於不連續導通模式，使部份二極體達到零電流截止之效果，減少反向回復電流造成之損失。本論文詳述轉換器動作原理分析、穩態分析與參數設計。
為驗證本論文所用單級式轉換器，實際製作一輸入電壓110 Vrms，輸出電壓48 V，額定功率100 W。其實作結果驗證本論文所用單級式轉換器理論與性能。

Generally, an AC-DC power converter is composed of a power factor correction stage and a DC-DC converter stage. It can achieve high input power factor with input current harmonic meeting the standards. However, it increases the circuit design complexity and component number.
A single-stage buck-boost-forward converter with power factor correction is presented. The front stage is a buck-boost type power factor correction to have high input power factor. With configuration of buck-boost type, the voltage stress on the storage capacitor between two stages can be reduced. The second stage is a forward converter to regulate output voltage, and the power density can be increased without the third winding of transformer. By using fuzzy control, the performance of the converter can be enhanced. The converter operates in discontinuous conduction mode can achieve zero current switching on diodes to alleviate the reverse recovery problem. The operation principles, steady-state analysis, design guidelines of the converter are presented in the thesis.
In order to verify the effectiveness of the converter, a 100 W prototype with 110 Vrms line input and output voltage of DC 48 V has been implemented. The simulation and experimental results verify the theory and performance of the single-stage converter.

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