- 學位論文
利用光平衡控制技術之新型白光二極體驅動器設計
The Design of A New WLED Driver using Light-Balanced Control Techniques
摘要
白光二極體具有優點為其體積小、壽命較傳統光源長之特性，因此被廣泛應用於顯示器的發光源，相當符合現今全球關注的節能和環保問題。 本論文所提之直流-直流降壓轉換器具有較高效率，及電流偵測電路能有效降低輸出電流相互匹配誤差，使每一串(列)白光LED亮度可趨近一致。整個系統架構是由兩大部份組成，為(一)降壓直流-直流轉換器，主要是將電源端降到手機應用的適當電壓，電路包含導通元件、補償器、脈波寬度調變電路、非重疊電路與驅動電路。(二)白光LED驅動電路為轉阻放大器與運算放大器組成，採用分時多工的方式，此方式可以延長白光LED使用壽命，另一方面能降低輸出白光LED電流相互匹配的誤差，在此情況下，可使白光LED相互亮度更均勻。且採用光平衡控制的方式，可以達到輸出負載改變，輸出電壓瞬間變化幾乎為零，因此光平衡控制方式可保有乾淨的電源供其他電路使用。 整個白光LED驅動器晶片面積為1.97725*2.19472mm2包含pads，採用TSMC 0.35um混合訊號2P4M 3.3V/5V的CMOS製程來實現。工作電壓範圍在3.5V~4.8V，輸出電壓為4.2V，最大總輸出電流在60mA，晶片最大效率為87.8%，白光LED電流最大誤差為1.33%。
並列摘要
The white LED (WLED) has superiority of characteristics, such as smaller volume and longer life than traditional light sources. Therefore, the white LED is applied to the monitor luminescent source. In nowadays, it is quite fit in energy conservation and environmental protection issue in the whole world. The thesis introduced a dc-dc buck converter, which has high efficiency, and the current sensing circuit can reduce the matching error of the output current effectively. The brightness of the white LED in each string can approach coherence. The overall system is composed of two parts, (a) the step-down dc-dc converter, the mainly function is scaling down the power supply to suitable voltage for cell phone applications, the converter includes the pass element, the compensator, the pulse width modulation circuit, the non-overlapping circuit and the driving circuit; (b) the white LED driving circuit is composed of the trans-resistance amplifier and the operational amplifier. By using time-sharing techniques, the life of white LED can be prolonged. On the other hand, the technique can reduce the current difference of the white LED each other. In this situation, the brightness of white LED becomes more uniform. The light-balanced control can achieve that the instantaneous change of the output voltage is almost zero and insensitive to the load current variation, therefore, it can maintain a clean supply voltage for other circuits. The chip area of the white LED driver, which is fabricated with TSMC 0.35um mixed signal 2P4M 3.3V/5V CMOS process, is 1977.25μm x 2194.72μm including pads. The range of operating voltage is 3.5V~4.8V, the output voltage is 4.2V, the maximum total output current is 60mA, the maximum efficiency equals to 87.8%, and the maximum current difference between the white LEDs is 1.33%.