本文針對大型戶外液晶顯示器之發光二極體背光源，提出雙脈寬調變(Double Pulse Width Modulation, DPWM)調光方式，彌補各發光二極體模組個別差異，達到整體均勻光輸出的目的。此調光方式是利用光感測器偵測發光二極體輸出光之強弱，回饋給控制端作為調光依據，配合雙脈寬調變作為調光方式，除了可保留原系統整體調光功能外，還能針對發光二極體亮度不均部分做區域調整。本研究以含四組發光二極體光條之46吋液晶顯示器進行實驗，證實雙脈寬調變之調光方式，在整體亮度變化下，可獲得到較均勻之亮度與較一致之色座標，最大亮度可達到 2000 cd/m2以上

This thesis proposes a dimming approach with Double Pulse Width Modulation for equalizing the light output of the back light with light emitted diodes (LEDs) for large scale outdoor liquid crystal displays (LCDs). The approach compensates the difference among the LED light bars by adjusting the power outputs of converters according to the feedback of light strength from light sensors. With the proposed Double Pulse Width Modulation method, local brightness adjustment on the light bars can be made to provide a uniform light output and the dimming function for LCD can be retained. Experiments results made on a 46” LCD with four LED light bars demonstrate that the double pulse-width- modulation can provide uniformly in the light bar output. The experimental results show the proposed Double Pulse Width Modulation (DPWM) method can alleviate the problem from divergence of the light bars and thus can generate more uniform light output on LCDs.

中文摘要I
英文摘要II
目錄III
圖次V
表次VII
第一章緒論1
1-1研究背景與目的1
1-2戶外顯示器現行問題2
1-3論文大綱3
第二章LED驅動電路與調光基本原理5
2-1降壓型轉換器5
2-1-1模式一：S1 ON、S2 / S3 OFF (0 < t < DTs)6
2-1-2模式二：S1 / S3 OFF、S2 ON (DTs < t < Ts)7
2-1-3模式三：S3 ON、S1 /S2 OFF7
2-1-4降壓型轉換器波形8
2-2降壓型輸入與輸出電壓轉換比9
2-3降壓型輸出電流穩壓原理10
2-4 LED基礎調光方式11
2-5色座標系統11
2-6線性調光與脈寬調光實驗13
第三章LED模組光學模擬16
3-1 LED量測系統16
3-2 LED單體量測17
3-3不同位置光感測器模擬20
3-4光感測器之需求24
第四章設計實例與實驗量測26
4-1設計單一LED驅動電路26
4-2 LED驅動電路波形28
4-3雙脈寬調光架構29
4-4雙脈寬調光波形32
4-5電路效率34
4-6光條均勻度測試36
4-7 LCD整機測試系統37
第五章結論與未來研究方向41
參考文獻43

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