Amoled pixel driver circuit and pixel driving method

Abstract

The invention provides an AMOLED pixel driver circuit and pixel driving method. The AMOLED pixel driver circuit has a 6T1C structure, comprising a first thin film transistor (TFT) (T1), a second TFT (T2) forming mirror relation with the first TFT (T1), a third TFT (T3), a fourth TFT (T4), a fifth TFT (T5), a sixth TFT (T6), a capacitor (c1), and an organic light-emitting diode (OLED) (D1), and receiving a first scan signal (Scan1), a second scan signal (Scan2), a third scan signal (Scan3), a data signal (Data), and a predefined voltage (Vpre). The circuit can effectively compensate the threshold voltage of the driving TFT to solve the problem of unstable current flowing through the OLED caused by the threshold voltage drift. Moreover, the use of double-gate TFT as driving TFT allows designating the threshold voltage of the driving TFT through inputting predefined voltage.

Description

BACKGROUND OF THE INVENTION1. Field of the Invention[0001]The present invention relates to the field of display techniques, and in particular to an AMOLED pixel driver and pixel driving method.2. The Related Arts[0002]The organic light emitting diode (OLED) display provides the advantages of active light-emitting, low driving voltage, high emission efficiency, quick response time, high resolution and contrast, near 180° viewing angle, wide operation temperature range, and capability to realize flexible display and large-area full-color display, and is regarded as the most promising display technology.[0003]The driving types of OLED can be divided, according to the driving method, into the passive matrix OLED (PMOLED) and active matrix OLED (AMOLED), i.e., the direct addressable type and thin film transistor (TFT) addressable type, wherein the AMOLED provides the advantages of pixels arranged in an array, self-luminous, and high luminous efficiency and is commonly used for high defin...

AI Technical Summary

Benefits of technology

[0007]The object of the present invention is to provide an AMOLED pixel driver circuit, able to effectively compensate the threshold voltage drift of the driving TFT, without adjusting the data signal to alleviate the threshold voltage drift of the driving TFT, to stabilize the current flowing through the OLED and to ensure even light-emitting of the OLED to improve display result.

[0008]Another object of the present invention is to provide an AMOLED pixel driving method, able to effectively compensate the threshold voltage change of the driving TFT to solve the problem of unstable current flowing through the OLED caused by the threshold voltage drift so as to ensure uniform light-emitting of the OLED to improve display result.

[0019]Compared to the known techniques, the present invention provides the following advantages. The present invention provides an AMOLED pixel driver circuit and pixel driving method, using double-gate TFT as the driving TFT. In the pre-charging phase, the first scan signal turns on the third TFT to write the power supply voltage into the top gate of the first TFT (i.e., the driving TFT) and the top gate of the second TFT. In the threshold voltage programming design phase, the second scan signal turns on the fourth TFT and the sixth TFT to lower the voltages of the top gates of the first TFT and the second TFT and raise the threshold voltages until the threshold voltages reaching Vth=Vpre−Vdata. In the driving light-emitting phase, the top gate voltage of the first TFT remains unchanged and the threshold voltage remains Vth=Vpre−Vdata, the predefined voltage turns on the first TFT to make the OLED emit light and the current flowing through the OLED is independent of the threshold voltage of the first TFT so as to ensure uniform luminance of the OLED and improve display result. Furthermore, the effect of stress of voltage and light on the threshold voltage of the double-gate TFT is smaller, and the threshold voltage of double-gate TFT has a negative correlation with the top gate voltage. The use of double-gate TFT as driving TFT allows designating the threshold voltage of the driving TFT through inputting predefined voltage, and can alleviate the threshold voltage drift of the driving TFT without adjusting the data signal. The present invention provides an AMOLED pixel driving method able to effectively compensate the threshold voltage change of the driving TFT to solve the problem of unstable current flowing through the OLED caused by the threshold voltage drift so as to ensure uniform light-emitting of the OLED to improve display result.

Problems solved by technology

However, the known TFTs made of low-temperature polysilicon (LTPS) or oxide semiconductors are subject to threshold voltage drift due to light, source-drain voltage stress and other factors.

As the increase in the data signal further enhances the voltage stress on the driving TFT, which accelerates the threshold voltage drift, a vicious cycle is formed as a result.

Images