薄膜電晶體液晶顯示器驅動電路之設計

Abstract

此篇論文著重於液晶顯示器的驅動電路設計，其驅動電路分為閘級驅動電路以及源級驅動電路，其中閘級驅動電路是由移位暫存器、電位轉換器和輸出緩衝器組成，而源級驅動電路是由移位暫存器、閂鎖器、電位轉換器、數位對類比轉換器和輸出緩衝器組成。 因為液晶之穿透率和偏壓電壓的關係，呈現一個非線性的關係，所以我們設計了一個擁有珈瑪修正功能的數位對類比轉換器去補償這效應，並且利用一0.5µm CMOS製程實現晶片。而在輸出緩衝級方面，我們設計了兩種不同架構的電路以達到驅動高負載的功能，分別是摺疊式以及加強slew-rate的放大器。另外，在降低功率消耗方面，我們設計了兩種擁有電荷共享的電路，half recycling可節省約二分之一動態功率耗損而triple charge recycling可以節省約三分之二的動態功率耗損。而以上四種電路則是在一0.25µm CMOS製程中之試製晶片。 最後，我們利用電晶體特性較好的低溫多晶矽薄膜電晶體將驅動電路直接整合在面板上，並且將它和傳統高壓CMOS製程做了些比較，並且設計了兩個新的圖素擁有數位記憶體的電路，如此在靜止畫面下可以利用數位記憶體來更新圖素的電壓並且中斷週邊電路的運作，以達到節省功率消耗的目的，並且以低溫多晶矽之model利用Smartspice的模擬驗證其功能的正確以及決定電晶體的尺寸。

In this thesis, we focus on the driver circuits for TFT-LCD display. The driver circuits are divided into two parts, gate driver and data driver. Gate driver is composed of shift register, level shifter, and output buffer. Data driver is composed of shift register, level shifter, latch, digital to analog converter, and output buffer. Because the relationship of transparency versus voltage of liquid crystal is nonlinear, we design a digital to analog converter with gamma correction to compensate this effect. The circuit has been designed and fabricated in a 0.5µm CMOS process. In output buffer, we design two kinds of output buffer which can drive high loading. They are folded opamp and slew rate enhancement opamp. In addition, we design two circuits with charge recycling in order to reduce more power consumption. The circuit with half recycling can reduce about 1/2 dynamic power, and the circuits with triple charge recycling can reduce about 2/3 dynamic power. All of four circuits have been designed and fabricated in a 0.25µm CMOS process. Finally, we discuss the concept of using high performance low temperature poly silicon thin film transistor (LTPS-TFT) to directly fabricate the driver circuits on the display panel. The comparison on device characteristics between LTPS-TFT and high-voltage CMOS is investigated. In addition, we proposed two new circuits for pixels with digital memory. In the case of still images, the voltage of pixel electrode is refreshed by digital memory and it can shut down the peripheral driver circuits in the same time. So, it can save more power. The device dimensions and circuit operation of these two new circuits have been designed and verified by Smartspice simulation.