Study on the RC Delay Issues for the External Compensation AMOLED Circuit

• Main Authors: Zhang, Zi-Yang, 張梓洋
• Other Authors: Tai, Ya-Hsiang
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/why4xa

碩士 === 國立交通大學 === 光電工程研究所 === 106 === In this paper, we study on the RC delay issues for the external compensation method of Sentinel Voltage Control for AMOLED circuit with real-time feedback. This circuit has ramping bus and sensing bus to connect the pixel and the driver IC. Ramping bus is used to pass input signal, and sensing bus is used to pass sensing current. Since there are parasitic resistors and capacitors on the ramping bus and the sensing bus, the input signal and the sensing current can be affected by the RC delay. Because the proposed external compensation circuit is a real-time feedback, the delayed signal and wrong sensing current may cause serious problems in the circuit. In order to solve the problem of input signal delay, we propose two methods. The main concept of the first method is capacitive coupling, and the driving voltage is pulled back the expected value by capacitive coupling. The concept of the second method is to add a delay block to make the delay input signal of near end and far end be the same. We also propose a method to solve the effect of RC delay on the sensing bus. The concept of the method is to add an analog computer to correct the wrong sensing current to the right value. Finally, we propose two methods that deal with the effects of RC delay on the both buses. The first method uses the look-up table and delay time adjustment. The concept is to form a table with the near end data and use it for and far end. According to the required driving current, we select the best available sensing voltage in the table and make minor adjustment in the ramp stop time with a delay block. The second method is to adjust the near-end and far-end I-V converting factor with different component. For the same driving current, the sensing currents of the near and far ends translate to the same sensing voltage through different I-V converting component. Therefore, we make the external compensation AMOLED circuit useful even with the RC delay on buses.