開發一主動矩陣有機發光二極體顯示器之電流讀取電路

Abstract

本論文針對電壓驅動所導致之主動矩陣有機發光二極體顯示器的有機發光二極體元件劣化，製程漂移等因素，在顯示器面板外部設計一款互補式金屬氧化半導體電流讀取電路，讀取顯示器面板中以六個薄膜氧化電晶體和一個電容組成的畫素電路之電流大小。首先使用一推拉式暫態電流加速電路對面板的電流感測線做預充電，其目的是加速面板畫素電路電流進入外部電路同時並放大畫素電流。然後設計一電流讀取電路，其架構包含電流式數位類比轉換器，電流比較器，雜散電流相減器以及其數位控制電路，經由雜散電流相減器減去因使用推拉式暫態電流加速電路所造成的背景電流，並對輸入電流與電流式數位類比轉換器的電流送進電流比較器進行比較，將期比較結果送進數位控制電路，其中數位電路中包含了循序漸進式邏輯(Successive approximation registers)以及暫存器，最後由數位電路輸出對應輸入電流的數位值，並完成電流感測的功能。感測電流的大小範圍在0.5nA至500nA，感測時間小於7us。

This thesis presents a CMOS current readout circuit in external active matrix organic light emitting diodes (AMOLED) for sensing thin-film transistor (TFT) current of AMOLED 6T1C pixel circuit, due to TFT current is extremely sensitive to the process drift by voltage-mode driving and OLED degradation. First of all, a Push-Pull Transient Current Feedforward (PPTCF) Circuit is used to pre-charge the AMOLED current sensing line, for enhancing the TFT current speed and amplifying current flowing into the current readout circuit. Then, a current readout circuit is designed to sense the current from pixel circuit. First, a baseline current subtracter is designed to subtract the baseline current from the PPTCF. Second, a current mode Digital Analog Converter is designed to generate current source for comparing with the pixel current in current comparator. At last, a digital circuit which used Successive approximation registers and register generate the digital output and complete the sensing current function. The sensing current value between 0.5nA to 500nA, sensing time less than 7us.