具有溫度補償功能之非晶矽薄膜電晶體閘極驅動陣列電路技術研究

Abstract

薄膜電晶體液晶顯示器(thin-film transistor liquid-crystal display，簡稱TFT-LCD)為現代顯示科技產品的主流，尤其應用於手機上，有輕巧、方便攜帶等特點。傳統的液晶顯示器顯示正確影像的方式是利用外部的驅動晶片來提供面板所需要的驅動電壓，近年來為了要達到輕巧、薄型化與降低生產成本的目標，系統整合式玻璃面板(SOG, System-on-glass)的概念陸續被提出，許多產品將面板周邊的電路直接製作在玻璃基板上，如閘極掃描驅動電路整合於液晶面板(gate driver on array, GOA)之技術。然而，TFT-LCD之畫素利用非晶矽薄膜電晶體(amorphous Silicon TFTs, 簡稱a-Si TFTs)作為開關，來控制顯示的畫面，而非晶矽薄膜電晶體之特性容易受溫度影響，其閘極在相同電壓下，溫度愈高，流經汲極與源極的電流愈大；相反的，溫度愈低，流經汲極與源極的電流愈小，所以溫度容易影響到顯示畫面的特性如對比度、Gamma曲線等。因此，如何使液晶顯示面板在不同的環境溫度下仍能具有良好的畫面品質，是很重要的課題。 在本篇論文中，提出一個玻璃基板上的溫度補償電路設計，此電路包含溫度感測器、多工器、電位移轉器電路並與GOA技術整合，藉由非晶矽薄膜電晶體之溫度特性設計出的溫度感測器能偵測環境溫度變化，進而推動GOA，使GOA輸出之閘極訊號可根據溫度變化而改變電位，即可以調整後的閘極訊號控制畫素之電晶體。此電路均以非晶矽薄膜電晶體作為電路的驅動元件，可實現顯示器周邊電路整合的應用。

Thin-film transistor liquid-crystal display (TFT-LCD) becomes a main stream for display technology in this generation. It features light weight, fine portability, especially for cellular phones. Traditional LCDs display the correct images by using external IC chips which provide the required driving voltage of panels. In recent years, the concept of system-on-glass panels is proposed progressively in order to achieve the goals of compact, thin and low cost displays. Many products integrate the peripheral circuits on the glass substrate such as the gate driver on array (GOA) technology. However, the pixels of TFT-LCD use amorphous Silicon TFTs (a-Si TFTs) as switch devices to control the images. The ambient temperature influences the electrical characteristics of a-Si TFTs. As the temperature increases, the TFTs turn on at a lower gate-source bias and the corresponding drain-source current level increases. On the contrary, as the temperature decreases, the TFTs turn on at a higher gate-source bias and the corresponding drain-source current level decreases. Therefore, the temperature influences the characteristics of the LCD panel, including the contrast ratio and gamma curve. The important subject is how to make the LCD panels with good image quality under various ambient temperatures. In this thesis, the integration of on-glass temperature compensation circuit and GOA technology is proposed. The temperature compensation circuit comprises the temperature sensor, multiplexer and level shifter circuits. It detects the ambient temperature changes by the temperature sensor circuit which is designed based on the temperature characteristics of the a-Si TFTs and drives GOA. Then, GOA generates the gate pulse signals with the modulated levels associated with the temperature. In this way, the pixels can be controlled by the modulated gate pulse signals. The circuits directly use a-Si TFTs as the driving devices; and further, SOG application can be implemented.