一种抑制关态漏电流和提高亮度稳定性的OLED微显示像素电路研究

Research on an OLED Microdisplay Pixel Circuit with Reduced Off-state Leakage Current and Improved Stability of Luminance

摘要:

OLED微显示像素驱动电路中，由于较小的存储电容和开关MOS管关态漏电流的影响，导致其存储电压和亮度不稳定。通过分析影响关态漏电流的主要因素，提出了一种多开关管串联和存储电容拆分相结合的办法以减小关态漏电流，并设计了一种含有两个开关管和两个存储电容的像素电路，该电路将关态漏电流由大于3pA减小为0.4pA，存储电压和亮度稳定性得到了很大的改善，小亮度时一帧的亮度变化仅为0.18cd/m2。电路可实现的最小OLED驱动电流为25pA，像素亮度范围为1.82~217.37cd/m2。

Abstract:

Due to the small storage capacitor and the influence of the off-state leakage current through the MOS transistor in the OLED microdisplay pixel circuit, the voltage on the storage capacity and the pixel luminance are unstable during a frame period. In this paper, the factors affecting the leakage current were analyzed and a combined method for reducing the leakage current was introduced, in which MOS switches were added in series-connection and the storage capacitor was split. Then an optimized pixel circuit composed of two transistors and two capacitors was designed, in which the leakage current was decreased from more than 3pA to 0.4pA. The holding effect of the storage voltage and the stability of the pixel luminance were also improved greatly and the change of the minimum pixel luminance was only 0.18cd/m2. In this proposed pixel circuit, a minimum OLED current of 25pA and a pixel luminance range of 1.82～217.37cd/m2 were realized.