A Thermal Compensation Circuit for Ultra Slim Notebook Applications

Abstract

As the thin and light notebook market expands demand for ultra thin notebook displays have significantly increased. In addition, thinner and lighter products need to have small integration area, high resolution low power consumption and satisfaction with strict temperature conditions. As a result, the net-book has become immensely popular in a short time and the demand for ultra slim and light net-book has rapidly increased, the need for high speed technology for slim notebook has expanded. To reduce the cost and integration area, many companies already are mass-producing the TFT-LCD module with the circuit of gate signal driver on a-Si substrates. Although the cost is lower and uniformity of device characteristics, there are problems such as electrical instability and variation of the threshold voltage with temperature. Therefore, it is difficult to optimize the size of the a-Si gate driver circuit and panel architecture, and the guarantee of driving margin at extreme high and low temperature is not sufficient so that image defects are issued repeatedly. Therefore, the proposed thermal compensation circuit controls the gate turn on and turn off voltage over a wide temperature range by feedback of temperature variation. In this thesis, the method for compensating the difference of output voltage level according to the external temperature condition and a-Si gate driver for low power consumption are given. This work is investigates two ways of thermal compensation circuits. One uses the voltage drop of diode arrays, the other is controlled by the reference voltage by thermal resistor. The changed voltage by the ambient temperature is used as the reference voltage which is applied to a differential amplifier to compensate the turn-on and turn-off voltage of a-Si:H gate driver through a charge pump. Also, these proposed circuits reduce power consumption by 20% and stabilize the operation range at the high and low temperature by applying the a-Si gate driver. This is a core technology of ultra slim notebook panel. In driving 10.1” net-book TFT-LCD module with the proposed thermal compensation method, line shaped noises resulting from leakage current of a-Si are removed by the proposed circuit with diode array and with thermal resistor at -10 °C ~ 10 °C. The temperature compensation circuit in this thesis is a viable and effective solution for the a-Si:H gate driver of the ultra slim and light notebook TFT-LCD display to extend the operating temperature range.