可調變電流畫素電路應用在非晶矽薄膜電晶體主動式矩陣有機發光二極體顯示器

Abstract

主動式矩陣有機發光二極體電流源畫素電路之瓶頸，在於顯示低灰階畫面時充電時間過長導致驅動資料的錯誤。本論文提出一種創新可調變電流畫素電路設計，利用儲存電容串接結構，來達到電流可調變的功效以縮短充電時間，同時不減少畫素的開口率。 根據數值分析與實驗的結果，若與傳統的電流源驅動畫素電路做比較，當顯示亮度為100 和 20 cd/m2時，充電時間可分別縮短10.7 和13.7倍。此外，當輸入電流範圍為0.2 和10 μ情況之下，此一可調變電流畫素電路設計可達最大驅動電流範圍2 nA 和 5 μA。另一方面，此畫素電路設計中，當驅動電晶體的截止電壓變化為4.5 V時，輸出電流變化可壓縮至3.8 %。這些實驗結果，皆證實此一可調變電流畫素電路設計可縮短充電時間及補償元件特性變化，以達到主動式有機發光二極體顯示器高解析、大尺寸之需求。

The difficulty that current-driven pixel circuit of active matrix organic light emitting diode devices encounters lies in long charging time resulted in data programming error while displaying low gray level images. This thesis proposes an adaptive current scaling pixel circuit design, which utilizes the cascade structure of storage capacitors to achieve current scaling function without sacrificing aperture ratio so as to shorten the charging time. By the analytical and experimental results, at display luminance of 100 and 20 cd/m2, the charging time can be shortened by a factor of 10.7 and 13.7, respectively; moreover, the driving current ranging from 2 nA to 5 μA can be obtained at programming current ranging from 0.2 to 10 μA. Besides, the variation of driving current can be suppressed to 3.8% while the threshold voltage variation of driving TFT is 4.5 V which evidently demonstrated shortening charging time and compensating the characteristic variations to fulfill the requirement of high resolution and large size AMOLED displays.