Design Considerations for External Compensation Approaches to OLED Display Degradation

Abstract

This paper presents design considerations for compensation circuitry that addresses OLED display degradation. It focuses on an external compensation method that utilizes an analog-to-digital converter (ADC) in the column driver IC. External compensation has the advantage of addressing both threshold voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</sub> ) and mobility (μ) shifts in the driving thin-film transistor (TFT). By maintaining pixel-to-pixel luminance uniformity, it addresses not only image sticking issues but also leads to a lifetime extension of the OLED pixels. Especially for large-sized OLED panels, it is important to understand the noise contributions from the analog front-end of the compensation circuitry. Noise contributions for each component are thus analyzed for maximizing the overall compensation performance. The analysis results show that the noise from the driving TFT and the display panel's parasitics dominate the total noise and that reducing the noise bandwidth can be an effective noise mitigation strategy. Furthermore, the presented results provide guidance on the required ADC specifications.