A new current‐mirror pixel circuit employing poly‐Si TFTs for active‐matrix organic light‐emitting‐diode displays

Abstract

A novel active-matrix organic light-emitting-diode (AMOLED) display employing a new current-mirror pixel circuit, which requires four-poly-Si TFTs and one-capacitor and no additional signal lines, has been proposed and sucessfully fabricated. The experimental results show that a new current mirror can considerably compensate luminance non-uniformity and scale down a data current more than a conventional current-mirror circuit in order to reduce the pixel charging time and increase the minimum data current. Compared with a conventional two-TFT pixel, the luminance non-uniformity induced by the grain boundaries of poly-Si TFTs can be decreased considerably from 41% to 9.1%. FIGURE 1 -The serial-current-mirror pixel circuit and timing diagram, T3 and T4, are paired by a serial-mirror type.

Source Driver Channel Reduction Schemes Employing Corresponding Pixel Alignments for Current Programming Active-Matrix Organic Light-Emitting Diode Displays

“…Particularly, a relatively poor charging problem in low gray level can give rise to inaccurate compensation in terms of ELA mura elimination. Figure 3(a) shows an adopted current programming compensation pixel circuit 5,6) for two types of proposed scheme, and the simulated result for obtaining optimum scaling ratio between driving transistor (D-Tr) and sampling transistor (S-Tr) is shown in Fig. 3(b).…”

“…1) Until now, to overcome this problem, various compensation techniques have been proposed in the area of voltage driving scheme as well as the current one. [2][3][4][5][6] Compared with the voltage driving scheme, the current driving scheme would be an alternative that can remove well the variations of threshold voltage and mobility among adjacent LTPS TFTs. However, the size of D-ICs for current driving is bigger than that of voltage driving because current D-ICs require highly accurate current control ability with current-steering digital-to-analog converter (DAC) and zerodata processing block.…”

“…We implemented the highly efficient current-scaling pixel circuit employing a mirror structure that was proposed previously. 5,6) In Fig. 1, CH1, CH2, and CH3 represent output channels of D-IC, and MK1 and MK2 correspond to control clocks for data multiplexing, which coincide with GK11, GK12, GK21, and GK22.…”

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

“…AMOLED panels use circuits to compensate for variation of threshold voltage (V th ) in low-temperature polysilicon thinfilm transistors (LTPS TFTs). Although many pixel circuits using various V th compensation methods have been developed, [1][2][3][4][5] there has to date been inadequate research on pixel circuits for large-sized three-dimensional (3-D) AMOLED displays. Recently, increasing attention has been given to the development of large-sized 3-D AMOLED panels.…”

An averaging pixel structure using microcrystalline‐silicon films prepared at high temperature for AMOLED displays

“…Among the different driving schemes and pixel designs that have been suggested to relieve image degradations, two approaches are mainly used for pixel addressing: voltage-or current-driven circuits. [1][2][3][4] Programming in current seems to be the most-effective method thanks to its capability to take into account fluctuations of V T and µ SAT . However, the voltage-inputting approach is generally preferred due to a better immunity to parasitic capacitances and data-driver accessibility from LCDs.…”