具有電荷儲存器和定電流機制的升壓電路用來改善RGB發光二極體背光模組效率

Abstract

目前色序法在液晶面版沒有濾光片的控制理論中可有效地減低色分離與運動模糊效應。由於RGB LEDs並非都是一直被開啟的，而是依序開啟紅、綠、藍LED，再藉由混光的效果去實現LCD面版之影像色彩，可使電源消耗量降低，也因為其高色域和低電源消耗的特性，此項創新成為今日LCD顯示市場的潮流。因為藍光和綠光LEDs和紅光LEDs擁有不一樣的材料特性，所以紅光LEDs的順向電壓就有別於藍光和綠光LED，因此在傳統紅綠藍三原色的背光模組會需要不同的直流對直流升壓轉換器去驅動不同顏色的LED， 本篇論文提出只利用一個升壓轉換器以減少成本以及PCB佈局面積，具有快速轉換電壓技術，利用降壓-儲能與升壓-放能(Buck-store and Boost-Restore (BSBR))技術以及電荷回收(Charge Recycling(CR))技術，可快速的轉換輸出電壓以提供不同供給電壓來依序驅動串聯紅,綠,藍(RGB)發光二極體(LED)，來減低在定電流產生器上的電源損耗，在暫態的參考值追蹤時間之內，這一項創新的控制技術快速轉換電壓技術以及電荷回收技術，就被提出來增強追蹤參考電壓反應，當輸出電壓位準由低轉換至高供給電壓時，儲存在回收電容上的能量可以被用來對輸出電容充電，以將輸出電壓提升回高供給電壓位準。因此多餘的能量可被回收。實驗結果顯示出此技術的確可以有效的縮短追蹤參考電壓的時間。此外，本項技術也另可提供一個調節電壓來驅動設立在液晶顯示器(LCD)系統上的副區塊。能源回收(CR)和降壓儲能升壓降能(BSBR)的最大效率分別可高達90%和94%，而本升壓LED驅動器的最大效率則為94.5%。實驗結果證明了本篇提出的降壓-儲能與升壓-放能技術(BSBR)可達到快速且有效率的追蹤參考電壓效能。

A Red, Green, and Blue (RGB) LED driver with the fast reference tracking (FRT) and charge-recycling (CR) techniques is proposed to implement a high efficiency and low cost RGB backlight module in color sequential notebook computers’ display. The FRT technique can speed up the reference tracking performance and effectively improves the up-tracking performance. However, the down-reference tracking depends on the load current and output capacitor. Therefore, the charge-recycling and buck-store/boost-restore techniques are proposed to store extra energy on the re-cycling capacitor when the output voltage is switched from high- to low-voltage level and releases the reserved energy back to the output node at next period. Furthermore, the output voltage can be rapidly switched between two different voltage levels by FRT technique without consuming much power owing to the restored energy by the CR technique. The proposed BSBR technique not only stores and restores extra energy during the transient time of the reference tracking response to improve the efficiency but also enhances the reference tracking response to greatly reduce load transition time. Experimental results show that the period of reference-tracking response can be improved. Furthermore, this BSBR technique also can provide a regulated voltage to drive the sub-block implemented in the LCD system. The maximum efficiency of energy recycling with CR and BSBR technique is up to 90% and 94%, respectively. The total power consumption of a notebook computer’s 15.4’ LCD panel can be reduced from 5W in cold cathode fluorescent lamp (CCFL) backlight module to about 2-3W in RGB LED backlight module with the field color sequential (FCS) algorithm. Furthermore, after the implementation of the LED driver with the FRT and CR techniques, the power loss can be reduced to about 24% of that without the FRT and CR techniques,.