Abstract
Hydrogenated amorphous silicon technology is widely used in active-matrix LCD (AMLCD) panels due to its mature manufacturing capabilities and reduced overhead costs in recent years. Efforts to improve the display quality have led to increasing market demand for transflective liquid crystal displays (LCDs) for portable products due to their excellent merits of thinness, lightweight and low power consumption. Additionally, further reducing overhead costs has led to the popularity of active matrix liquid crystal displays (AM-LCDs) that utilize thin film transistors (TFTs) as a switching component for the gate driver circuit. However, the threshold voltage shift of hydrogenated amorphous silicon (a-Si:H) TFTs due to long-term operation or high-bias stress deteriorates the stability of a gate driver circuit, ultimately lowering the image quality of the AM-LCDs.This dissertation proposes a novel single-cell-gap transflective liquid crystal display with two thin-film-transistors, two capacitors, and only one data line. The proposed circuit can increase the aperture ratio and reduce the fabrication costs. Simulation results indicate that the stored voltages closely correspond to the required data voltages in the T region and close to the low and middle gray levels in the R region. Moreover, the estimated maximum deviation of the stored voltage is less than 3 % in the T-mode and R-mode, while △VTH of TFTs is 0.3 V and the mobility variation of TFTs is ± 5 %, respectively. Two novel gate driver circuits are then developed, with experimental and simulation results verifying their feasibility. The first gate driver circuit, composed of 13 a-Si:H TFTs, two capacitors and 4 clock signals, utilizes an AC-driving structure in the proposed circuit to suppress the VTH shift of TFTs and prevent the row line from floating. Experimental results indicate that this circuit can operate stably for more than 240 hours at 100 ℃. The rising time (TRISE) and falling time (TFALL) of the output voltage in the first circuit are 6.5 μs and 5.5 μs, respectively. The second gate driver circuit, consisting of 12 a-Si:H TFTs, 1 capacitor and 6 clock signals, uses two low frequency alternative pull-down circuits to stabilize the output waveform and reduce the power consumption. Experimental results indicate that this circuit can operate stably for more than 240 hours at 100 ℃. The rising time (TRISE) and falling time (TFALL) of the output voltage are 7.8 μs and 5 μs, respectively. Additionally, according to the measurement results, the second gate driver circuit achieves a 52.6 % low power consumption than that of previous circuits.
| Date of Award | 2011 |
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| Original language | Chinese (Traditional) |
| Supervisor | Chih-Lung Lin (Supervisor) |