OLED Pixel Circuit Threshold Voltage Drift Compensation
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Solution Overview
Problem
Existing pixel circuits in OLED panels face issues with uneven brightness due to threshold voltage drifts of driving transistors, which cannot be compensated for simultaneously with increased charging rates.
Innovation Solution
A pixel circuit comprising a light emitting element, first and second voltage control circuits, a driving circuit, an energy storage circuit, and a reset circuit, where the first voltage control circuit sets the potential of a control node relative to the threshold voltage of a control transistor, and the second voltage control circuit sets the potential of another control node relative to this, ensuring the driving current is independent of the driving transistor's threshold voltage, thereby compensating for threshold voltage drifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional pixel circuits are used, then the structure is simple, but the brightness is uneven due to threshold voltage drifts
Solution Approach 1:
The pixel circuit is divided into multiple functional modules: driving circuit, first voltage control circuit, second voltage control circuit, reset circuit, and data writing circuit. Each module has a specific function in controlling the threshold voltage compensation, allowing the complex compensation mechanism to be organized systematically and improving brightness uniformity while maintaining manageable complexity.
Solution Approach 2:
The first voltage control circuit adjusts the potential of the first control node before the driving transistor operates, and the second voltage control circuit adjusts the potential of the second control node based on the first control node's potential. This preliminary voltage adjustment ensures that the driving current is compensated for threshold voltage drifts before affecting the light emitting element, thereby improving brightness uniformity.
2Manufacturing precision
If threshold voltage compensation is implemented, then brightness uniformity improves, but charging rate decreases
Solution Approach 1:
The voltage control circuits dynamically adjust the potentials of control nodes based on the actual threshold voltage of the driving transistor. The first voltage control circuit responds to the driving transistor's threshold voltage, and the second voltage control circuit further adjusts based on the first control node's potential. This dynamic adjustment mechanism provides real-time compensation without significantly slowing down the charging process, thus improving brightness uniformity while maintaining charging rate.
3Manufacturing precision
If multiple voltage control circuits are added, then threshold voltage drift is compensated, but response time increases
Solution Approach 1:
The first and second voltage control circuits are integrated into a unified compensation mechanism that works together to control the driving transistor's threshold voltage. The first voltage control circuit handles the primary compensation by adjusting the first control node's potential, while the second voltage control circuit provides additional adjustment based on the first control node's state. This merged approach achieves effective threshold voltage compensation while minimizing the time penalty that would result from completely separate control mechanisms.
Data Source
AI summary
A pixel circuit, a pixel driving method, and a display device are provided. The pixel circuit includes a light emitting element, a first voltage control circuit, a second voltage control circuit, a driving circuit, a first energy storage circuit, a data writing circuit, and a reset circuit. The first voltage control circuit includes a first control transistor, the driving circuit includes a driving transistor, and a difference between a threshold voltage of the first control transistor and a threshold voltage of the driving transistor is within a first range. The first voltage control circuit controls a potential of a first control node under control of a reset control signal; and the second voltage control circuit controls a potential of a second control node under control of the potential of the first control node.