OLED Pixel Circuit Bias Adjustment for Threshold Voltage Drift
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Solution Overview
Problem
The driving transistor in OLED pixel circuits experiences threshold voltage drift due to hysteresis effects, leading to unstable display brightness and flicker, which conventional threshold compensation circuits cannot effectively address.
Innovation Solution
Incorporating a bias adjustment circuit and threshold compensation circuit in the pixel circuit to detect and self-compensate threshold voltage deviations, with a bias adjustment stage prior to data writing and light-emitting stages to adjust the bias state of the driving transistor, reducing the hysteresis effect and stabilizing the threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional threshold compensation circuit is used, then the circuit structure is simple, but the threshold voltage drift caused by hysteresis effects cannot be effectively compensated
Solution Approach 1:
The bias adjustment circuit performs preliminary bias state adjustment of the driving transistor before the data writing stage. By establishing the appropriate bias state in advance, the circuit prepares the transistor to minimize hysteresis effects during subsequent operation, thereby compensating for threshold voltage drift without requiring complex real-time adjustment mechanisms
Solution Approach 2:
The threshold compensation circuit detects the threshold voltage deviation of the driving transistor and provides compensation signals to correct the drift. This feedback mechanism continuously monitors and adjusts the threshold voltage, effectively stabilizing the display brightness while maintaining a relatively simple circuit structure through automated compensation
2Reliability
If the driving transistor operates without bias adjustment, then the circuit operation is simple, but hysteresis effects cause threshold voltage drift and display flicker
Solution Approach 1:
The bias adjustment circuit performs preliminary bias state adjustment of the driving transistor before the data writing stage. By establishing the appropriate bias state in advance, the circuit prepares the transistor to minimize hysteresis effects during subsequent operation, thereby compensating for threshold voltage drift without requiring complex real-time adjustment mechanisms
Solution Approach 2:
The bias adjustment circuit maintains continuous bias state adjustment during the driving period, ensuring the transistor operates in an optimal state throughout. This continuous action prevents the accumulation of hysteresis effects and maintains stable display brightness, transforming a potentially problematic continuous operation into a beneficial sustained adjustment process
Data Source
AI summary
A display panel and a display device are provided. The display panel includes pixel circuits. Each pixel circuit includes a driving transistor, a data writing circuit, a light-emitting control circuit, a threshold compensation circuit and a bias adjustment circuit. The driving transistor includes a gate electrically connected to a first node, a first terminal electrically connected to a second node, and a second terminal electrically connected to the third node, and is configured to generate a driving current. The third node is connected to a light-emitting element through the light-emitting control circuit. The bias adjustment circuit is configured to provide a signal of a bias adjustment signal terminal to the second node under control of a signal of a first scanning signal terminal in such a manner that a bias state of the driving transistor is adjusted.