主動矩陣式有機發光二極體驅動電路使用時間比例灰階技術之研究

Abstract

本論文提出一個改善發光效率之設計應用於主動有機發光二極體驅動電 路。而這個被驅動的畫素是以兩個電晶體及一個電容所組成的架構。藉由 增加發光時間及減少定址時間來提升傳統的時間比例灰階驅動方式之發光 效率。兩種可行方案被提出。取樣的移位暫存器採用倍速串列輸入將減少 定址時間。振輻調變編碼的使用將減少子圖框的數目進而增加發光時間。 結合上述兩種方案的驅動方式能夠提升24%的發光。較高的發光特性，將 使得每個畫素面積減少，較小的畫素使得較高解析度的顯示器能夠被製 造。此外將驅動電路整合在面板上是最終目標，面板上常使用的多晶矽薄 膜電晶體有臨界電壓及遷移率變異的問題，而這些變異使得類比線路設計 不易實現於面板上。而這個改良的時間比例灰階驅動方式也是使用數位驅 動方式，在驅動電路部分它不需類比電路，他使得驅動電路完全整合於面 板上將成為可能。為了正確影像顯示，另外提出掃描訊號阻絕，以防止兩 個相鄰的掃描線切換時所造成的顯示資訊錯誤寫入。 這個主動矩陣式有機發光二極體驅動電路是用0.6 微米18V CMOS 製程 來模擬。由於點亮時間的限制，此一驅動電路適合應用於QVGA 或低於此 解析度。

Using improved luminance efficiency for the driving circuit of Active Matrix Organic Light Emitting Diodes (AMOLED) is presented in this thesis. The driven pixel is based on the structure with two transistors and one capacitor. We propose to enhance the luminance efficiency of conventional time ratio grayscale by increased lighting time and decreased addressing time. Two practical approaches to enhance luminance will be proposed. For decreased addressing time, shift register of sampling adopt double rate serial-in. For increased lighting time, amplitude modulation coding will reduce the number of sub-frame, and increase the lighting time. The combined method could enhance 24%. luminance. The higher luminance allows a small pixel. Small pixel will allow high resolution displays to be created. Moreover, the final goal is that driver circuits are integrated on the display panel. TFT by poly-silicon is always adopted. For poly-silicon thin film transistor (TFT), both mobility and threshold-voltage vary randomly across the plate. The former two variables would lead to analog circuit is hard to implement on panel. The improved time ratio grayscale also adopts the digital driving. There is no analog design in driver by this method. It is possible that the driving circuit is fully implemented to System on Panel (SOP). Another proposed scan signal gating for correct image display prevent from error-programming when adjacent scan line are toggling. A prototype of this AMOLED driver is simulated by 0.6 um 18V CMOS technology. Because lighting time is limited, it is suitable for the Quarter Video Graphic Array (QVGA) or below the resolution. error-programming when adjacent scan line are toggling.