Design Of Voltage-programmed Pixel Compensation Circuit Based On All P-type LTPS-TFT

Organic light-emitting diodes have the advantages of colorful,ultra-thin,self-luminous,etc.,and are widely used in the field of high-performance display technology.The pixel unit in display technology is realized by driving OLED by thin film transistors.However,under long-term voltage stress,the threshold voltage and mobility of the drive transistor will drift,causing changes in the OLED drive current;in addition,the parasitic resistance generated by the address electrode will cause IR drop,resulting in the power supply voltage of each pixel unit Different,will also cause changes in OLED drive current.This article designs voltage-programmed pixel circuits to compensate for the changes caused by the above factors to stabilize the drive current of the OLED.This article introduces the AMOLED display technology and the basic principles of the pixel compensation circuit.Based on the in-depth investigation of the research progress of the pixel compensation circuit,the full P-type low-temperature polysilicon Silicon TFT is used to design the pixel compensation circuit.The specific work is summarized as follows:(1)Improved a full P-type voltage programming 6T2 C pixel compensation circuit.Compared with the original circuit which can only compensate the threshold voltage drift,the improved circuit can also compensate the I-R drop and reduce one transistor.The simulation results show that when the threshold voltage of the drive tube changes by ± 0.5 V,the current error rate is less than 2.2%.When I-R drops by 0.5V,the gate-source voltage difference changes by 0.004 V,which does not affect the drive current.(2)A full P-type voltage programming 5T1 C pixel compensation circuit is designed.The circuit adopts the structure of a mirror transistor,and the threshold voltage is extracted and the data voltage is input in the programming stage at the same stage.The circuit can compensate the threshold voltage drift and I-R drop of the driving tube,and stabilize the driving current of the OLED.Simulation results show that when the threshold voltage of the drive tube changes by ± 0.5 V,the current error rate is less than 5.8%,and when the I-R drops by 10%,the current error rate is less than 7.9%.(3)Continue to improve the driving timing of the above 5T1 C pixel compensation circuit.During the programming phase,the timing of the switch tube is adjusted to reduce the source potential of the driving transistor to compensate for the drift of the TFT mobility and stabilize the driving current of the OLED.Simulation results show that the mobility of the driving transistor changes by ± 30%,and the current error rate is less than 5.4%.