Pixel Driving Circuit Threshold Voltage Drift Compensation
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Solution Overview
Problem
Low temperature polysilicon thin film transistors used in pixel driving circuits exhibit non-uniformity in electrical parameters, leading to color non-uniformity and brightness differences in organic light emitting diode displays, while oxide thin film transistors suffer from threshold voltage drift under long-term biasing and high temperature, affecting display quality.
Innovation Solution
A pixel driving circuit comprising a driving transistor, reset module, writing module, and control modules that compensate for threshold voltage drift, improving luminous uniformity and image quality by resetting and stabilizing node voltages, and controlling data signal output to maintain consistent threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low temperature polysilicon thin film transistors are used in pixel driving circuits, then mobility and stability are improved, but non-uniformity in electrical parameters occurs due to crystallization process limitations
Solution Approach 1:
The patent applies preliminary action by performing threshold voltage compensation before the display panel operates. The compensation circuit pre-adjusts the threshold voltage of the driving transistor during the manufacturing or initialization stage, so that even if parameter drift occurs during long-term use, the display quality remains consistent. This is achieved through a compensation circuit that adjusts the threshold voltage of the driving transistor before the panel is put into service, thereby preventing color non-uniformity and brightness differences that would otherwise develop over time.
2Manufacturing precision
If oxide thin film transistors are used, then process uniformity is improved, but threshold voltage drift occurs under long-term biasing and high temperature
Solution Approach 1:
The patent implements feedback by using a compensation circuit that continuously monitors and adjusts the threshold voltage of the driving transistor. The compensation circuit detects threshold voltage drift that occurs during long-term operation under bias and high temperature conditions, and automatically compensates for this drift by adjusting the gate voltage or other circuit parameters. This feedback mechanism ensures that despite the inherent threshold voltage instability of oxide thin film transistors under stress conditions, the actual display performance remains stable and uniform over time.
3Device complexity
If threshold voltage drift is not compensated, then device complexity is reduced, but color non-uniformity and brightness differences occur in OLED displays
Solution Approach 1:
The patent introduces an intermediary compensation circuit that mediates between the driving transistor and the OLED display elements. This compensation circuit acts as a buffer that absorbs the effects of threshold voltage drift in the driving transistor, preventing these variations from being transmitted to the OLED pixels. The compensation circuit includes additional transistors and capacitors that form a feedback loop, adjusting the drive signal to compensate for threshold voltage changes, thereby maintaining uniform display quality without requiring fundamental changes to the OLED structure itself.
Data Source
AI summary
A pixel driving circuit, a display panel and a driving method of the pixel driving circuit are provided by the present disclosure. The pixel driving circuit includes a driving transistor, a reset module, a writing module, a first control module, and a light emitting device. The pixel driving circuit with the 5T2C structure can compensate the threshold voltage drift of the driving transistor, improve the luminous uniformity of the light emitting device, and further improve the image quality.