Fast Progressive Compensation Method for Externally Compensated AMOLED Displays

Congwei Liao,Wenlong Bai,Shengdong Zhang,Hezi Qiu,Jinyuan Wen,Min Zhang,Chenglin Li,Hailong Jiao,Hing-Mo Lam

doi:10.1109/jeds.2021.3057195

Congwei Liao, Wenlong Bai + Show 7 more

Open Access

https://doi.org/10.1109/jeds.2021.3057195

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Abstract

The externally compensated display system has been proved to have greater potential to completely solve aging and uniformity issues of the AMOLED display system than the internally compensated display system. However, the traditional compensation method is time consuming and responses slowly to the mobility change of TFT. The traditional compensation method performs calibration during the inter-frame blanking period, the length of which is limited. Only a few rows of pixel circuits can be calibrated per frame. Furthermore, each pixel circuit needs multiple times of calibration to reach compensated state. In this article, a fast progressive compensation method is proposed. The calibration of a row of pixel circuits is performed K rows ahead of the display line during the display data updating period. By doing so, the proposed fast progressive compensation method can approach compensated state faster than the traditional method because display data updating period is significantly longer than the inter-frame blanking period. For the case of 10% inter-frame blanking period and 20 μs waiting delay for feedback data line to be stable, the proposed method reduces the compensation time by ~14x than the traditional method.

Highlights

After decades of development, Active-Matrix Organic LightEmitting Diode (AMOLED) display technology shows better performance than Active-Matrix Liquid Crystal Display (AMLCD) display technology in color gamut, contract ratio, response time, viewing angle, and working temperature
If the length of the calibration operation is longer than the inter-frame blanking period, no calibration operation can be performed by the traditional compensation method
The pixel circuits are built with a-IGZO Thin Film Transistor (TFT) and OLED process, while the other circuitry is built in CMOS process

Summary

INTRODUCTION

Active-Matrix Organic LightEmitting Diode (AMOLED) display technology shows better performance than Active-Matrix Liquid Crystal Display (AMLCD) display technology in color gamut, contract ratio, response time, viewing angle, and working temperature. The real-time external compensation is a design in which the feedback sensing and pixel circuit programming are performed in the same time period. The non-real-time external compensation is a design in which the feedback sensing and pixel circuit programming are performed in the different time periods. Since the 1-bit output comparator only senses whether the feedback data is larger or smaller than the reference data, multiple iterations of calibration are needed to approach the final compensation value which is able to feedback the data close to the reference data This compensation method is named as progressive compensation. With the traditional non-real-time external compensation scheme, the feedback sensing of pixel circuits is carried out during inter-frame blanking period. A fast compensation method is proposed, which allows the design to carry out calibration during the display data updating period instead of inter-frame blanking period.

REVIEW OF THE EXTERNALLY COMPENSATED DISPLAY SYSTEM

PERFORMANCE COMPARISON

CONCLUSION