本論文之研究範疇為一室內照明50瓦發光二極體驅動電路設計，前級係採用返馳式功率因數修正電路，藉以透過簡單電路架構而達到高轉換效率跟高功率因數、且穩定輸出電壓之目的，並減少輸入電流的總諧波失真率。後級選用雙輸入降壓式轉換器，其用來改進效率、降低電感值，且同時提高LED電流調光轉換速率。雙輸入降壓式轉換器採用浮動接地設計，其功率二極體、電感、輸出電容在開關截止時與第二輸入電壓源相接，而非接地。控制電路方面利用一電流取樣電阻，易於了解所採取電感電流訊息。因為這些好處，此電路架構為LED照明設備應用提供了高效率、低成本的解決方案。
本論文詳細分析討論電路之動作原理與設計考量，並實現一雛型電路驗證此架構的與控制策略之可行性。

關鍵字：返馳式功率因數修正電路、雙輸入降壓式轉換器、LED驅動電路、PWM調光

In this thesis, a 50-watt dimmable LED driver is presented for general indoor lighting applications. The front stage is a flyback power factor corrector (PFC). It features a simple topology to achieve a high conversion efficiency, a high power factor (PF), and a slightly regulated output voltage. Also the total harmonic distortion (THD) of the input current harmonics can be reduced. The post-stage circuit is a two-input (twin-bus) buck converter, which has been designed to raise the efficiency, to decrease the size of the inductor, and to speed up the changing rate of the LED current. The twin-bus buck converter is of floating ground configuration. The power diode, the inductor and the output capacitor are connected to a second DC input voltage, instead of the ground, when the main switch is turned off. The information of the inductor current can be easily obtained by a current sensing resistor. These benefits contribute to provide a high-efficiency, low-cost, and reliable solution for LED lighting applications.
The operation principles and design considerations of the studied LED driver are analyzed and discussed. A laboratory prototype is also designed and tested to verify the feasibility.

Keyword: Flyback power factor corrector (PFC), two-input (twin-bus) buck converter, LED driver, PWM dimming

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