OLED Pixel Circuit Threshold Compensation for Brightness Uniformity
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Solution Overview
Problem
In OLED displays driven by active matrix, non-uniformity in threshold voltage of driver transistors leads to varying brightness across the display due to manufacturing processes, affecting image uniformity and luminous quality, and internal resistance causes power supply voltage variations.
Innovation Solution
A pixel circuit with a threshold compensation sub-circuit that pre-stores the threshold voltage of the driver transistor in a storage capacitor, and a light-emitting control sub-circuit that decouples the gate-source voltage from the power supply voltage, ensuring consistent light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional pixel circuits are used for AM driving, then the display can be driven with active matrix control, but the non-uniformity of threshold voltage of driver transistors leads to different brightness for the same data signal
Solution Approach 1:
The patent applies preliminary action by introducing a threshold compensation phase before the normal display phase. During this preliminary phase, the storage capacitor is pre-charged to compensate for the threshold voltage of the driver transistor. This advance compensation ensures that subsequent brightness variations due to threshold voltage non-uniformity are eliminated, directly resolving the contradiction between manufacturing precision and display driving capability.
2Use of energy by stationary object
If conventional pixel circuits are used, then the display can operate with standard power supply, but internal resistance causes power supply voltage variations leading to different brightness
Solution Approach 1:
The patent introduces an intermediary mechanism by using the storage capacitor as a local energy reservoir. This capacitor decouples the driver transistor's gate-source voltage from the power supply voltage, preventing voltage drops caused by internal resistance from affecting the driving signal. The storage capacitor acts as a mediator that isolates the sensitive threshold voltage from power supply fluctuations, resolving the contradiction between power supply operation and brightness uniformity.
3Manufacturing precision
If threshold compensation is implemented, then brightness uniformity is improved, but the circuit complexity increases with additional sub-circuits
Solution Approach 1:
The patent applies merging by integrating the threshold compensation function into the existing pixel circuit architecture. The storage capacitor, which is already a standard component in AMOLED displays, is utilized for dual purposes: maintaining the driving signal and compensating for threshold voltage. By combining these functions into a single component rather than adding separate compensation circuits, the patent improves brightness uniformity while minimizing the increase in device complexity.
Data Source
AI summary
A pixel circuit and a driving method thereof, as well as a display device. The pixel circuit includes an initialization signal terminal, a scanning signal terminal, a data signal terminal, a first power supply terminal, a second power supply terminal, a reference voltage terminal a light-emitting signal control terminal, a reset signal terminal, a data writing sub-circuit, a threshold compensation sub-circuit, a light-emitting control sub-circuit, a reset sub-circuit, a storage capacitor, a driver transistor and a light-emitting element. The threshold compensation sub-circuit is configured to pre-store the threshold voltage of the driver transistor in the storage capacitor.