New 2-D/3-D Switchable Pixel Circuit to Achieve Uniform OLED Luminance for High-Speed AMOLED Displays

Abstract

This paper presents a new 2-D/3-D switchable pixel circuit based on low-temperature polycrystalline-silicon thin-film transistors (TFTs) at a frame rate of 240 Hz for active-matrix organic light-emitting diode (OLED) displays. The proposed circuit compensates for threshold voltage (VTH) variations of TFTs, VDD IR drops, and degradation of OLED luminance. To achieve highly uniform displays during high-speed operation, the circuit uses simultaneous emission in 3-D mode and parallel addressing in 2-D mode to ensure that the period of compensation is sufficiently long to detect each variation of normalized luminance. Simulation results verify that variations in the normalized luminance of the proposed circuit are all less than 4% when the VTH of the driving TFT varies by ±0.5 V, VDD drops by 1 V, and the VTH shift of the OLED increases from 0 to 0.9 V, simultaneously.

Keywords

• Active-matrix organic light-emitting diode (AMOLED)
• low-temperature polycrystalline silicon (LTPS)
• thin-film transistor (TFT)