近年來主動式有機發光二極體顯示器之市場成長快速並廣受人們所重視，然而由薄膜電晶體所組成的畫素電路將因為製程上的差異與經長時間操作後，產生臨界電壓漂移之問題，且有機發光二極體亦會隨著材料老化而使其臨界電壓升高，造成畫素電流衰減，這些缺陷皆會導致面板顯示品質降低。
為了解決上述問題，本論文實現一外部補償系統，可補償電晶體臨界電壓漂移和有機發光二極體材料老化對畫素電路之影響。外部補償系統的畫素電路採用傳統2T1C架構，因此具有高開口率與節能之優點，系統可區分為場域可程式邏輯陣列與外部電路兩部分。場域可程式邏輯陣列內，建構控制與記憶體兩單元，控制單元負責畫素電路進行補償時的演算流程和控制訊號的處理，並決定資料電壓於資料寫入階段時的補償值，而系統各參數與資料電壓的補償值則儲存於記憶體單元。外部電路由定電流源電路與電流比較器所組成，定電流源電路產生定電流Iref而電流比較器將輸出畫素電路之驅動電流與Iref的比較結果，此時控制單元偵測電流比較器之狀態並不斷提升畫素電路驅動電晶體的閘極端電壓，使驅動電流提升，待驅動電流提升至相等於Iref後，系統將偵測到電晶體與有機發光二極體的臨界電壓漂移量，並藉此改善畫素電流衰減問題。
實驗結果顯示，經本系統補償後的畫素電流誤差率低於15%，相較於傳統2T1C電路的65%誤差率已明顯改善，驗證了本系統能確切補償畫素電路受電晶體臨界電壓與有機發光二極體材料老化之影響，改善面板顯示亮度不均勻之現象。

In recent years, active-matrix organic light-emitting diode (AMOLED) displays have developed rapidly and attracted much attention. However, the pixel circuits are composed of thin-film transistors (TFTs) whose electrical characteristics may vary or shift because of either fabrication process variation or long-term operation. Additionally, the threshold voltage of OLED increases due to the degradation of organic materials, resulting in the decay of the pixel circuit current. Consequently, these problems reduce the image quality of AMOLED displays.
In order to resolve the issues mentioned above, an external compensating system for the AMOLED pixel circuit is proposed in this work which can compensate for the threshold voltage shifts of driving TFTs and OLEDs. The proposed compensating system has the advantages of high aperture ratio and low energy consumption because it adopts the conventional 2T1C pixel circuit structure. The compensating system can be divided into two parts, including the field-programmable gate array (FPGA) and the external circuit. The control unit which is built for FPGA is utilized to handle control signals and decide the calibration of data voltage during the programming stage of the pixel circuit operation. In addition, the memory unit built for FPGA stores the system parameters and the calibration of data voltage. Conversely the external circuit is composed of a constant current source and comparator. The constant current source generates a constant current (Iref), and the current comparator than senses the difference between the Iref and the OLED current of the pixel circuit. Meanwhile, the control unit increases the gate voltage of the driving TFT until the OLED current is equal to the Iref. The proposed system therefore can detect the threshold voltage shifts of TFTs and OLEDs so as to ameliorate the decay of the pixel circuit current.
The experimental results show that the current error rates of the proposed system are all below 15%, which shows an apparent improvement compared to conventional 2T1C circuits whose error rates are as high as 65%. Therefore, the proposed system can indeed compensate for TFT threshold voltage variations and OLED material degradation to improve the current uniformity of AMOLED displays.

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