Flicker modeling scheme of liquid crystal displays based on current leakage without information about TFT parameters

Abstract

It is well known that the current leakage at a switching thin film transistor (TFT) of a pixel circuit is one of key factors for the luminance fluctuation of liquid crystal displays (LCDs) perceived as a flicker artifact. This paper proposes a flicker estimation scheme based on the current leakage model of an amorphous silicon (a-Si) TFT. The proposed scheme consists of four blocks such as gray-to-voltage conversion, pixel voltage update, voltage-to-transmittance conversion, and flicker estimation. Gray-to-voltage and voltage-to-transmittance conversion blocks are built from measured data at a source driver and a panel for gray levels. Flicker estimation is established by applying fast Fourier transform (FFT) to simulated transmittance waveforms. The pixel voltage update block is made up by the voltage leakage model which parameters are estimated by matching simulation results to measurement results at a band gray pattern regarding several gray levels. Any given information of TFTs is not required for parameter extraction. The proposed method is applied to a WSXGA+ in-plane switching (IPS) LCD of a 1-dot inversion and flicker levels are estimated within an error range of ±0.6 dB at full gray patterns of gray levels from 32 to 224, compared to measurement results.