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.

No abstract

An ambient light sensing function, which is one of several value-added functions in system-on-panel (SoP), can contribute to low power consumption and improve visibility by auto brightness control. However, it is very challenging to read the photoleakage current of p-intrinsic-n (PIN) diode directly, which is generally used as a photodetector in SoP. Therefore, we propose an ambient light sensing circuit using low-temperature polycrystalline silicon (LTPS) thin-film transistors (TFTs) and the PIN diode, which can output analog voltage converted from the photo-leakage current of the PIN diode. Through the measurement of the proposed circuits under ambient light variations from 0 to 2000 lx, we confirmed that the proposed ambient light sensing circuits can perform sensing and readout operations accurately. The dynamic range of the proposed circuit is 35 dB and the maximum variation of the output voltage among eight samples is AE45 mV.

There is the problem of picture quality nonuniformity due to thin film transistor (TFT) characteristic variations throughout a panel of large-area high-resolution active matrix organic light emitting diodes. The current programming method could solve this issue, but it also requires very long charging time of a data line at low gray shades. Therefore, we propose a new driving method and a pixel circuit with emission-current sensing and feedback operation in order to resolve these problems. The proposed driving method and pixel circuit successfully compensate threshold voltage and mobility variations of TFTs and overcome the data line charging problem. Simulation results show that emission current deviations of the proposed driving method are less than 1.7% with AE10:0% mobility and AE0:3 V threshold voltage variations of pixel-driving TFTs, which means the proposed driving method is applicable to large-area high-resolution applications.

We have developed Shared Column-Line Driving (SCLD) method, by which the number of data driver LSIs is reduced to a half of conventional ones without doubling the number of gate lines. This paper shows the concept and system configuration of the SCLD method which can be applied for high pixel density and low cost TFT-LCDs. . IntroductionThese days active matrix liquid crystal displays(AMLCDs) have been widely used for many applications. And its resolution is becoming higher. In other words, pixel pitch is becoming smaller. However, tape carrier package(TCP) and tape automated bonding(TAP) techniques do not satisfy the small and fine pitch characteristics for the small size and high resolution applications such as cellular phones and personal digital equipments. Therefore, there are lots of researches about package of AMLCD such as chip on glass(COG) to overcome the pitch limitation of TCP and TAP. And also, there was a research to increase the resolution of AMLCD without change of package types and bonding technologies. It was the half-column-line driving method which was proposed for reducing the power consumption and module cost, originally[1].This driving method can reduce the number of column driver LSIs by which each column line drives both pixels on its right and left sides and reduce the power consumption of column drivers in the module to a half but its panel has twice as many gate lines as those of a conventional one. These doubled gate lines decrease the aperture ratio and the rearranged of video data as zig-zag sequence increase the complexity of controller and digital data rate between frame memory and controller and also slightly increase the module cost because of double numbered gate driver.And two pixel are driven in one horizontal line time, it has not enough line time to drive the high resolution TFT-LCDs. To eliminate this problem, we propose a Shared Column-Line Driving(SCLD) method. In this paper, we describe the concept, and operation principle of the proposed pixel structure, and architectures and configurations of scan driver and data driver for implementation of the proposed SCLD method. Pixel Structure of SCLD MethodThe pixel array for the proposed SCLD method is shown in Fig. 1. The proposed SCLD method can reduce the number of column lines by half of the conventional LCD panel without increasing the number of gate lines. One column line is connected to the both side pixels on its right and left sides. Two pixel TFTs in the right side of the column line connected to N-th gate line. In the left side of the column line, one pixel TFT is connected to the N-th gate line and the other is connected to (N+1)-th gate line. And two series connected TFTs of right pixel, those gate are connected N-G1 G2 G3 G4 D1 D2 Figure 1. The pixel structure of the proposed shared columnline driving method. G2 G3 G1 1st H 2nd H a b Vdd gnd positive video range negative video range D1 Vcom Figure 2. The waveform of the scan pulse and driving sequence of the proposed SCLD method.th gate line, are reduced to one T...