Abstract— A voltage‐programming method with transimpedance‐feedback control technique is proposed for compensating threshold voltage and mobility variations of driving thin‐film transistors (TFTs) in large‐area high‐resolution polycrystalline‐silicon (poly‐Si) active‐matrix organic light‐emitting‐diode (AMOLED) displays. Those electrical characteristic variations of TFTs throughout a large‐area high‐resolution panel result in picture‐quality non‐uniformity of AMOLED displays. The simulation and experimental results of the proposed method show that the maximum emission‐current error for 30‐in. full‐high‐definition television (HDTV) applications is less than 1.9% when the mobility variation and the threshold‐voltage variation are ±12.5% and ±0.3 V, respectively. The proposed method is the best programming method for large‐area high‐resolution AMOLEDs among the published methods.
In this paper, light-emitting-diode (LED) backlight driving circuits and dimming method for medium-sized and large liquid crystal displays (LCDs) are proposed. The double loop control method, the intelligent-phase-shifted PWM dimming method, the fast-switching current regulator, and the current matching techniques are proposed to improve not only the current regulation characteristics and the power efficiency but also the current matching characteristics and the transient response of the LED current. The brightness of the backlight using the proposed local dimming method was determined from the histogram of the local block to reduce the power consumption of the backlight without image distortion. The measured maximum power efficiency of the LED backlight driving circuit for medium-sized LCDs was 90%, and the simulation results showed an 88% maximum power efficiency of the LED backlight driving circuit for large LCDs. The maximum backlight power-saving ratio of the proposed dimming method was 41.7% in the simulation with a high-contrast image. The experiment and simulation results showed that the performance of LEDs as LCD backlight units (BLUs) improved with the proposed circuits and method.
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