Simultaneous Emission AC-OLED Pixel Circuit for Extended Lifetime of OLED Display

Abstract

This paper demonstrates a pixel circuit of seven thin film transistors (TFTs) and two capacitors that drives an AC driven OLED (AC-OLED) at a simultaneous emission scheme. Because the AC-OLED is composed of two OLED units connected in opposite directions, the proposed circuit drives the current programmed once during a frame time in both ways. Since one OLED unit emits the light for about half frame time, the lifetime of OLEDs is ameliorated substantially. In addition, the proposed pixel circuit allows threshold voltage and supply voltage variations to be compensated. SPICE simulation results with a p-channel low temperature poly-silicon TFT model show that the average current non-uniformities are improved to 1.19% and 3.37% for threshold voltage and supply voltage variations of ±0.5 V, respectively.

Keywords

• AC-OLED
• image-sticking
• lifetime
• TFT
• simultaneous emission
• compensation