Kyung-hoon Chung

High-speed pixel circuits for large-sized 3-D AMOLED displays

— Large-sized active-matrix organic light-emitting diode (AMOLED) displays require high-frame-rate driving technology to achieve high-quality 3-D images. However, higher-frame-rate driving decreases the time available for compensating Vth in the pixel circuit. Therefore, a new method needs to be developed to compensate the pixel circuit in a shorter time interval. In this work, image quality of a 14-in. quarter full-high-definition (qFHD) AMOLED driven at a frame rate of over 240 Hz was investigated. It was found that image degradation is related to the time available for compensation of the driving TFT threshold voltage. To solve this problem, novel AMOLED pixel circuits for high-speed operation are proposed to compensate threshold-voltage variation at frame rates above 240 Hz. When Vth is varied over ±1.0 V, conventional pixel circuits showed current deviations of 22.8 and 39.8% at 240 and 480 Hz, respectively, while the new pixel circuits showed deviations of only 2.6 and 5.4%.

53.5: High-Speed AMOLED Pixel Circuit and Driving Scheme

An active matrix organic light emitting diode pixel circuit and its driving scheme for high frame frequency are proposed for implementation of a 3D display. The proposed pixel circuit can compensate the threshold voltage distribution of low temperature poly silicon-thin film transistors at high-speed operation of 240Hz or more. According to the simulation, current deviation of 1.73% and 3.94% are obtained at frame rates of 240Hz and 480Hz when Vth distribution is ±0.5 V.

Advanced four‐mask a‐Si TFT array fabrication process using improved materials

In order to achieve higher-performance and lower-cost a-Si TFT array manufacturing, an advanced four-mask fabrication process using low-resistant metals, a new pixel electrode material, and improved unit processes was developed. Slit (or gray-tone) photolithography, in combination with a continuous all-in-one dry-etching process, solved the chronic problems of the current four-mask process. Additionally, a new combination of materials and a new wet etchant for the gate-line patterning made it possible to achieve stabilized wet-etching results and reduced the number of process steps. Our advanced a-Si TFT-array fabrication process is applicable to both notebook and monitor displays, and will further improve the market position of TFT-LCDs by improved performance and manufacturing process simplification.

27.1: Integrated pMOS Gate Driver for a 3D AMOLED Display

Simultaneous Emission with Active Voltage control (SEAV) is a strong candidate for crosstalk-free driving of 3D Active Matrix Organic Light Emitting Diode (AMOLED) displays. A gate driver for a SEAV 3D AMOLED panel needs two operating modes: the simultaneous switching mode and the progressive scanning mode. However, conventional gate drivers can operate in only progressive scanning mode. In this paper, a new integrated gate driver to support both of these modes is proposed and applied to a prototype 3D AMOLED display panel.