Display Device Back Bias Voltage Compensation for Transistor Degradation
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Solution Overview
Problem
Flat panel display devices face reduced display quality due to degradation of driving transistors, leading to luminance variations between pixels, as the driving current decreases with increased threshold voltage variation.
Innovation Solution
A display device design that includes a driving transistor with a back bias voltage adjustment mechanism, where a controller measures threshold voltages and adjusts both the back bias voltage and data voltage for each pixel to compensate for threshold voltage variations, improving the compensation margin and display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the driving transistor operates for extended periods, then the display device can maintain continuous operation, but the driving transistor degrades leading to threshold voltage variation and luminance reduction
Solution Approach 1:
The patent implements a sensing circuit that measures the threshold voltage of the driving transistor before the degradation significantly impacts display quality. By performing preliminary measurement and compensation, the system can adjust the data voltage in advance to counteract the threshold voltage variation, thereby maintaining display quality during continuous operation
Solution Approach 2:
The patent establishes a feedback loop where the sensing circuit continuously monitors the threshold voltage of the driving transistor, and the controller adjusts the data voltage based on the measured threshold voltage. This closed-loop feedback mechanism enables real-time compensation for transistor degradation, maintaining consistent display quality over extended operation periods
2Reliability
If the driving transistor threshold voltage varies due to degradation, then the driving current to the light emitting element decreases, but this causes luminance reduction and display quality degradation
Solution Approach 1:
The patent changes the data voltage parameter dynamically based on the measured threshold voltage of the driving transistor. By adjusting the data voltage to compensate for threshold voltage variations, the system maintains the driving current at the desired level, thereby preserving luminance and display quality despite transistor degradation
3Device complexity
If no compensation mechanism is implemented, then the device structure remains simple, but luminance deviation between pixels occurs due to transistor degradation
Solution Approach 1:
The patent introduces a sensing circuit and controller as intermediary components that measure the threshold voltage and adjust the data voltage accordingly. These intermediary elements enable compensation for transistor degradation without requiring fundamental changes to the pixel structure, achieving luminance uniformity through voltage adjustment rather than structural modification
Data Source
AI summary
A display device includes a driving transistor on a substrate, a light emitting element disposed on the driving transistor, and a lower electrode disposed between the substrate and the driving transistor. The driving transistor includes an active pattern and a gate electrode. The active pattern includes a first region, a second region, and a channel region between the first region and the second region. The light emitting element is electrically connected to the second region of the active pattern. The lower electrode overlaps the channel region of the active pattern and provides a back bias voltage to the driving transistor.