現今發光二極體(Light-emitting diode, LED)驅動器多採用脈波寬度調變(Pulse Width Modulation, PWM)調光法，此方法透過變動PWM導通時間的長短來改變平均電流大小，可以在保持色彩品質的同時改變LED的亮度。但是，此調光方式將調光電流操作於較高的驅動電流下，因此LED的發光效率(Luminous Efficency)較低；此外，於各LED通道加入電流調節元件等也會降低效率。
本文研製一高效率雙匯流排調光電路，透過雙匯流排特性降低開關元件的電壓應力，以達到提高LED驅動器效率的效果。本文提出之LED驅動器包含功率因數修正器及雙輸出半橋LLC諧振轉換器，並藉由數位控制器實現本文所提出之調光方法。由實驗結果顯示，調光電路各通道皆可達均流效果，電路最高效率達99.9 %；功率因數修正器之最高效率達96.8 %，功率因數可達0.998；雙輸出半橋LLC諧振轉換器之最高效率達96.1 %，輸出電壓調節率小於±5%。

Nowadays, the pulse width modulation (PWM) dimming technique is mostly adopted in light-emitting diode (LED) drivers. This method changes the average current by varying the conduction time of the PWM signal, and it can change the LED luminosity while maintaining the color quality simultaneously. However, this dimming technique operates the dimming current under a high driving current. Therefore, the luminous efficiency of LED is low; furthermore, the efficiency will further be reduced when current regulation elements are added to each LED channel.
This study designs and implements a high-efficiency twin-bus dimming circuit. With the adaption of the twin-bus technique, the voltage stresses of the power switches can be reduced so as to improve the LED driver efficiency. The LED driver proposed in this study consists of a power factor corrector, a dual-output half-bridge LLC resonant converter as well as a dimming circuit, and the dimming technique proposed in this study is realized by digital controllers. As the experimental results suggest, each channel of the dimming circuit can achieve the current balancing. The highest efficiency of the twin-bus circuit, power factor corrector, and dual-output half-bridge LLC resonant converter can reach 99.9%, 96.8%, and 96.1%, respectively; also, the power factor can reach 0.998, and the output voltage regulation is less than ±5%.

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