P‐11: An Improved Voltage Programmed Pixel Structure for Large Size and High Resolution AM‐OLED Displays

Abstract

We propose an improved pixel structure for large size and high resolution AM‐OLED(Active matrix‐Organic Light Emitting Diode) displays. The proposed structure is composed of 5 TFT and 1 capacitor. It can compensate not only the threshold voltage variation of LTPS(Low Temperature Poly Silicon) TFTs but also the voltage drop of supply voltage on panel. Moreover, it operates with simple structure and control signals. In this paper, we describe the operating principle and the characteristics of the proposed pixel structure and verify the performance by HSPICE simulation comparing with those of previously reported structures.

A Luminance Compensation Method Using Optical Sensors with Optimized Memory Size for High Image Quality AMOLED Displays

“…To overcome the aforementioned problems, several studies on various driving methods have been reported [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Internal compensation methods [1][2][3][4][5][6][7] perform compensation in pixel structures by storing a threshold voltage (V th ) variation of TFTs to a capacitor in the pixel and then compensate for the emission current using a stored V th variation.…”

“…Internal compensation methods [1][2][3][4][5][6][7] perform compensation in pixel structures by storing a threshold voltage (V th ) variation of TFTs to a capacitor in the pixel and then compensate for the emission current using a stored V th variation. However, as the display resolution increases, the row line time decreases; thereby, the luminance uniformity becomes degraded because the compensation is performed during a row line time.…”

A novel current-biased voltage-programmed pixel circuit with low temperature polycrystalline silicon thin film transistors for AMOLED

“…For voltage programming, in order to take all of the non-idealities (i.e., threshold, mobility, parasitic resistors etc.) into account, a number of additional TFTs and capacitors are indispensable [10,11,12,13], which would lead to low aperture ratio (AR) problem. Moreover, for the reason that the TFTs usually work close to subthreshold region during compensation period, threshold voltage sampling may consume most of the row time, which limits the display resolution [14].…”

New voltage programming LTPS‐TFT pixel scaling down VTH variation for AMOLED display

“…However, the inevitable current non-uniformity of poly-Si TFT arrays due to the threshold voltage (V TH ) and the mobility (µ eff ) variations, which are caused mainly by crystallization such as excimer laser annealing (ELA), need to be improved for high-quality images [2]. Many pixel circuits have been reported in order to compensate the nonuniform OLED current (I OLED ) variation by the voltage or current programming methods [2][3][4][5].…”

“…However, each pixel circuit requires various considerations for compensating the V TH and mobility non-uniformities of poly-Si TFTs as well as the supply voltage drop in the V DD line [3][4]. The compensation pixel circuits use typically 4~6 poly-Si TFTs, 1~2 capacitors, 1~3 scan signals, 1~2 supply voltages.…”