Design of current driving column driver ICs for AMOLED displays

Abstract

This thesis focuses on the high speed and high accuracy current feedback driving methods, which compensate the spatial and temporal variations of thin film transistor and hybrid data driving method with real-time OLED compensation for active matrix OLED displays. In Chapter 1, a direct fast feedback current (DFFC) driver is proposed for high quality AMOLED displays and can be applicable to a-Si or other backplane technologies which have spatial and temporal variations of devices. The use of current feedback loop with directly current comparing has been employed to overcome the limitations of the driving performance in the conventional drivers. The impedance lowering and frequency compensation techniques are used to enhance the speed and guarantee the stability of the feedback loop. And an optimal selection rule of compensation capacitors is proposed. With the pre-discharge function, the driving speed of 11us is achieved at the data current of as low as 10nA. The data current from 10nA to 2.55uA, when it is driven by the presented driver, is successfully delivered to the pixel array with 1.5kΩ/100pF line conditions.

In Chapter 2, a DFFC driver is designed for high quality AMOLED displays with inverted type pixels. For the inverted type pixel, the proposed driver is implemented with an integrator with a loop compensator and an inverting amplifier with a switched-capacitor gain circuit. The proposed driver has a settling time of 7us for a panel load of 1.5kΩ/100pF. De-multiplexing operation is realized with the DFFC driver to drive two channels using one driver. The area of the driver at the implemented chip is 120 x 131um2 per two chan-nels.

In Chapter 3, a DFFC driver with double zeros compensation is proposed for medium to large AMOLED displays. The zeros for lead compensation are implemented with switched-capacitor circuits to reduce chip area. The selection rules for compensation capacitors and zero capacitors are described to ob-tain wide bandwidth and ...