本論文提出一整合順向與降昇壓轉換之無橋式功率因數修正器，在架構上可視為單一開關控制兩組子轉換器，共同分擔與傳遞功率。其中，透過降昇壓式子轉換器高功因特性及順向式子轉換的變壓器適當設計，能夠有效改善輸入電流總諧波失真；在功率分配比例上，大部分的功率係透過順向式子轉換器直接傳輸至負載，以降低變壓器鐵芯的體積及損失，且在功率傳輸過程中，不需如Cúk、SEPIC及Zeta轉換器，使用全橋二極體整流器及耦合電容，因此可減少電流路徑上之功率元件，進而降低導通損失和元件熱損，提高轉換效率。本文架構操作於不連續導通模式，無需電流控制迴路，功率開關亦能共用控制訊號，因此可減低控制系統複雜性。
本論文詳述所提之轉換器操作原理、穩態分析及參數設計流程，為了驗證轉換器效能及可行性，本文模擬與實作一額定功率135W，輸入電壓90Vrms到130Vrms(60Hz)，輸出電壓48V的雛型電路。由實驗結果可知，在不同輸入電壓及負載下，所實現電路之輸入電流總諧波失真因數皆可低於13.4%，且轉換效率最高達90.7%。

This thesis proposes a bridgeless power factor correction with integration of forward and buck-boost converters. The rectifier can be considered equivalent to a single switch that controls two subconverters (buck-boost and forward subconverters) that share and deliver the total output power synchronously. By using a high power factor for the buck-boost subconverter and an appropriate transformer design for the forward subconverter, the total harmonic distortion (THD) of the input current can be effectively reduced. To reduce the volume and core loss of the transformers, the forward subconverter directly delivers a major part of the output power to the load. Since no full-bridge rectifier or coupling capacitor is used in the current flowing path in the power conversion process (similar to the Cúk converter, single-ended primary inductor converter, and Zeta converter), conduction losses are reduced and the efficiency and thermal performance of the proposed rectifier are enhanced. Moreover, because the proposed rectifier is designed to operate in the discontinuous inductor current mode, the current loop is not required. Furthermore, the two switches in the circuit can be controlled using a single control signal, which simplifies the design of the control system considerably.
The operating principles, steady-state analysis, and design guidelines of the proposed rectifier are detailed in this thesis. To verify the effectiveness and feasibility of the proposed rectifier, simulations and experiments are conducted using a 135 W prototype circuit with an input voltage in the range of 90–130 Vrms (60 Hz) and an output voltage of 48 Vdc. The experimental results show that the THD of the input current is less than 13.4% under different input voltages and output powers. Moreover, the prototype circuit shows a maximal efficiency of 90.7%.

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