OLED Driving Circuit Threshold Voltage Drift Compensation
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Solution Overview
Problem
The drift of the threshold voltage of the driving thin film transistor (TFT) in OLED display panels causes unstable driving current, leading to disorders in luminous brightness and reduced image quality in AMOLED displays.
Innovation Solution
The OLED driving circuit incorporates a third TFT, a sixth TFT, and an elimination module, which cooperatively eliminate the change in driving current caused by the threshold voltage drift by reconfiguring and compensating voltages during specific periods, ensuring the threshold voltage is not calculated in the driving current formula.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional 2T1C driving circuit is used, then the device complexity is low, but the driving current becomes unstable due to threshold voltage drift
Solution Approach 1:
The driving circuit is segmented into multiple functional modules: a first compensation module with first and second compensation capacitors connected in parallel, and a second compensation module with third and fourth compensation capacitors connected in parallel. This segmentation allows independent optimization of each compensation function, improving overall reliability while maintaining manageable complexity through modular design
Solution Approach 2:
The patent changes the electrical parameters of the driving circuit by introducing additional capacitors with specific capacitance values (first compensation capacitor Ccomp1, second compensation capacitor Ccomp2, third compensation capacitor Ccomp3, fourth compensation capacitor Ccomp4) to compensate for threshold voltage drift. The capacitance values are carefully selected to maintain the balance between compensation effectiveness and circuit complexity
2Illumination intensity
If threshold voltage drift is not compensated, then the circuit structure remains simple, but luminous brightness becomes disordered
Solution Approach 1:
The patent implements feedback compensation by using compensation capacitors that store charge during one period and release it during another period. The first compensation capacitor Ccomp1 and second compensation capacitor Ccomp2 provide feedback to compensate for threshold voltage drift, while the third compensation capacitor Ccomp3 and fourth compensation capacitor Ccomp4 provide additional feedback compensation, ensuring uniform luminous brightness across different pixels
Solution Approach 2:
The compensation capacitors are charged in advance during the storage period before the emission period. The first compensation capacitor Ccomp1 and second compensation capacitor Ccomp2 are charged during the storage period, and then discharged during the emission period to provide compensation. This preliminary action ensures that compensation is available when needed, maintaining luminous brightness uniformity without requiring complex real-time adjustment circuits
3Reliability
If additional compensation components are added, then driving current stability improves, but the circuit complexity increases
Solution Approach 1:
The compensation capacitors serve multiple functions: they compensate for threshold voltage drift, maintain driving current stability, and ensure uniform luminous brightness. The first compensation capacitor Ccomp1, second compensation capacitor Ccomp2, third compensation capacitor Ccomp3, and fourth compensation capacitor Ccomp4 all contribute to the same overall goal of improving reliability, making the added complexity justified by the multi-functional compensation capability
Data Source
AI summary
The present disclosure relates to an organic light-emitting diode (OLED) driving circuit, including: a switch thin film transistor (TFT), a driving TFT, a storage capacitor, a third TFT, a sixth TFT, an OLED, and an elimination module. A gate of the third TFT is configured to receive reset signals, a first end of the third TFT is configured to receive a reset voltage, and a second end of the third TFT is electrically connected to the first node. A gate of the sixth TFT is configured to receive enabling signals, and a first end of the sixth TFT is electrically connected the second node. An elimination module is electrically connected to the first electrode of the storage capacitor and the first end of the driving TFT. The elimination module is configured to receive the data voltage and the power supply voltage.