Pixel circuit and display device and driving method of pixel circuit

Abstract

The invention discloses a pixel circuit and a display device and a driving method of the pixel circuit, relates to the field of display, and can effectively compensate heterogeneity and drifting of depletion type or enhancement type thin film transistor (TFT) threshold voltage, and current difference caused by heterogeneity of an organic light emitting diode (OLED). The pixel circuit comprises a luminous element, a drive TFT, a first TFT, a second TFT, a third TFT, a fourth TFT and a capacitor. A supply voltage signal is inputted to a drain electrode of the drive TFT, a drain electrode of the first TFT is connected with a source electrode of the drive TFT, a source electrode of the first TFT is connected with the luminous element, and a grid electrode of the first TFT receives a first control signal. A source electrode of the second TFT receives a data signal, a drain electrode of the second TFT is connected with a grid electrode of the drive TFT, and a grid electrode of the second TFT receives a scanning signal. A source electrode of the third TFT receives a referential voltage signal, and a grid electrode of the third TFT receives the scanning signal. A source electrode of the fourth TFT is connected with a drain electrode of the third TFT, a drain electrode of the fourth TFT is connected with the grid electrode of the drive TFT and the drain electrode of the second TFT, and a grid electrode of the fourth TFT receives a second control signal.

Description

technical field [0001] The present invention relates to the display field, in particular to a pixel circuit, a display device and a driving method for the pixel circuit. Background technique [0002] Organic Light Emitting Diode (OLED) is a current-driven active light-emitting device, because of its unique characteristics such as self-illumination, fast response, wide viewing angle and can be fabricated on a flexible substrate, OLED-based organic light-emitting display It is expected to become the mainstream in the display field in the next few years. [0003] Each display unit of an organic light-emitting display is composed of OLEDs. According to the driving method, organic light-emitting displays can be divided into active organic light-emitting displays and passive organic light-emitting displays. Active organic light-emitting displays mean that each OLED is composed of A thin film transistor (Thin Film Transistor, TFT) circuit is used to control the current flowing thr...

AI Technical Summary

Problems solved by technology

[0006] Among them, Vgs is the potential difference between the gate and source of the drive transistor T1, μ n is the carrier mobility, Cox is the capacitance of the gate insulating layer, W / L is the width-to-length ratio of the transistor, Vdata is the data voltage, Voled is the operating voltage of the OLED, and Vth is the threshold voltage of the driving tube T1. From the above formula, it can be known that if If the Vth between different pixel units is different or the Vth drifts with time, the current flowing through the OLED will be different, which will affect the display effect. In addition, the non-uniformity of the OLED device will cause the different operating voltage of the OLED, which will also cause the current difference.

[0007] At present, there are many kinds of pixel circuits used to compensate the current difference caused by Vth non-uniformity, drift and OLED non-uniformity, but usually the driving TFT is set as figure 2 The diode connection shown above is realized, and this structure is only applicable to the enhancement type TFT, but for the depletion type TFT, since it can still be turned on when Vgs=0, the voltage stored by the TFT does not include the threshold voltage Vth information, so for the depletion TFT, the existing pixel circuit cannot compensate the current difference caused by the non-uniformity of the threshold voltage

Images