A Pixel Circuit with Improved Luminance Uniformity and Flicker for AMOLED Displays with a Wide VRR Range of 15 Hz to 360 Hz

Abstract

This letter proposes a 6T2C pixel circuit designed for LTPS-based AMOLED displays to improve luminance uniformity and reduce flicker across a wide range of variable refresh rates (VRRs). The proposed circuit employs a two-step compensation method to address variations in the threshold voltage and subthreshold slope of driving thin-film transistors (TFTs), improving luminance uniformity. Additionally, it minimizes the hysteresis effect of TFTs using an inducing hole-trapping technique, resulting in lower flicker. The proposed pixel circuit was verified with 48 samples for a 5.8-inch QHD AMOLED display, achieving notable reductions in emission current errors (ECEs) within a VRR range of 15 Hz to 360 Hz. The luminance uniformity performance was improved compared to a previous 7T2C circuit, with measured spatial ECEs of +3.4/−3.4 LSB versus +4.1/−4.2 LSB at the 256th gray level. The flicker performance was also improved, with measured temporal ECEs of +0.4 LSB and −1.1 LSB versus −0.8 LSB and −3.2 LSB at the 16th and 256th gray levels, respectively.