本論文主旨為研製47吋液晶顯示器白光LED背光模組之驅動電源。主架構採用單級返馳式功率因數修正器，提供白光LED低電壓漣波，及改善功率因數與高轉換效率之電源。並針對LED順向電壓VF的差異，造成LED電流不均流的問題，運用電壓控制電流方式控制，達到每路白光LED燈條均流的目標。
本研究由轉換器架構，分析返馳式變壓器初級側主繞組NP1、NP2的匝比，達到改善功率因數與轉換效率。利用二極體共陽極低電壓偵測的回授方式，自動調整白光LED的電壓源。降低電壓控制電流的功率開關損失，最後設計實例電路，以實驗量測數據，驗證電源架構及控制方法的可行性。
實驗結果輸入電壓90 V ~ 264 V輸出功率88 W(50 V/1.76 A)，白光LED驅動電路平均效率為88.3 ％，當輸入功率大於75 W時，功率因數為0.9與設定規格相同，並且符合EN6100-3-2 D類諧波限制與能源之星2.0平均效率的規範；而LED電流平衡方面，LED燈條電流差異為2.7 ％。

The objective of this thesis is to design a power driver for a 47" LCD monitor with white LED backlight. The main structure, uses flyback topology with single-stage power factor correction, provides power to white LEDs’ with low-voltage ripple and high conversion efficiency. The voltage-controlled current method is used to effectively minimize the unbalanced current distribution in every LED light bars due to difference of LEDs’ forward voltage.
This study analyzes the turn ratio of transformer primary winding, NP1 and NP2, of flyback converter. In order to improve the power factor and conversion efficiency further, is used to a positive feedback low voltage detection method on diodes adjust automatically the power supplying for white LEDs, which in turn reduces the power loss on power switch used for voltage-controlled current. According to experimental result, the circuit is verified the possibility of proposed topology and the control method.
The experimental result shows a prototype circuit, 88 W (50 V/1.76 A) with universal input voltage (90 V to 264 V), with the power factor achieve 0.9 when input power is over 75 W, and 88.3 % in efficiency, the current difference among LED light bars’ is 2.7 %. The electrical characteristics meet harmonic limits of EN6100-3-2 Class D and Energy Star 2.0 specification.

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