OLED Pixel Circuit Bias Adjustment for Threshold Drift
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Solution Overview
Problem
The driving transistor in OLED display panels experiences threshold voltage drift due to hysteresis effects, leading to unstable display brightness and flicker, which conventional pixel circuits cannot effectively compensate.
Innovation Solution
Incorporating a bias adjustment circuit and threshold compensation circuit in the pixel circuit to detect and self-compensate threshold voltage deviations, and adjusting the bias state of the driving transistor through a series of bias adjustment stages to mitigate hysteresis-induced threshold voltage drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel circuit without bias adjustment is used, then the device complexity is low, but the driving current becomes unstable due to threshold voltage drift
Solution Approach 1:
The pixel circuit is segmented into multiple functional modules: a driving transistor for current generation, a threshold compensation circuit for detecting and compensating threshold voltage deviations, and a bias adjustment circuit for adjusting the bias state of the driving transistor. This segmentation allows each module to perform its specific function independently, improving the stability of the driving current while keeping the overall circuit design manageable through modular organization.
Solution Approach 2:
The threshold compensation circuit implements a feedback mechanism by detecting the threshold voltage of the driving transistor and generating a compensation signal that is fed back to adjust the gate voltage of the driving transistor. This feedback loop continuously compensates for threshold voltage drift, ensuring stable driving current output despite long-term operation and hysteresis effects.
2Manufacturing precision
If threshold compensation circuit is added to detect and compensate threshold voltage deviation, then the display effect is improved, but the device complexity increases
Solution Approach 1:
The threshold compensation circuit is merged with the existing pixel circuit structure by sharing common elements such as the driving transistor and utilizing existing node connections. The compensation circuit uses the same gate, source, and drain nodes of the driving transistor, integrating the compensation function into the existing circuit topology rather than adding completely separate components, thereby reducing overall complexity.
Solution Approach 2:
The pixel circuit is designed with multi-functionality where certain components serve multiple purposes. For example, the driving transistor serves both as the main current source and as part of the compensation mechanism. The bias adjustment circuit also serves dual functions by adjusting the bias state and working in conjunction with the threshold compensation circuit, reducing the need for dedicated separate components and simplifying the overall circuit structure.
3Stability of the object's composition
If bias adjustment circuit is added to adjust bias state of driving transistor, then hysteresis effect is reduced, but the device complexity increases
Solution Approach 1:
The bias adjustment circuit performs preliminary action by adjusting the bias state of the driving transistor before the main operation occurs. By pre-adjusting the bias conditions, the circuit prevents hysteresis effects from developing during normal operation, ensuring stable threshold voltage and driving current from the outset rather than requiring continuous correction during operation.
Solution Approach 2:
The bias adjustment circuit acts as an intermediary between the control signal and the driving transistor. It receives control signals and translates them into appropriate bias adjustments for the driving transistor, mediating the interaction between the control logic and the current generation element. This intermediary function allows for fine-grained control of the bias state while isolating the complexity of the adjustment mechanism from the main driving function.
Data Source
AI summary
A display panel and a driving method thereof, 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.