Pixel Compensation Circuit Double-Gate Transistor Drift
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Solution Overview
Problem
Current 7T1C internal compensation circuits in AMOLED displays have limited threshold voltage compensation range and cannot effectively compensate for positive threshold voltage drifts, leading to non-uniform image display across different gray levels.
Innovation Solution
A 5T2C pixel compensation circuit utilizing a double-gate structure transistor with a diode-connect mode for real-time threshold voltage compensation, allowing for dynamic adjustment and broadened compensation range, including positive and negative drifts, through a combination of initialization, data writing, and light-emitting control units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a 7T1C internal compensation circuit using diode-connect mode TFTs is used, then threshold voltage compensation is achieved, but the compensation range is limited and cannot compensate for positive threshold voltage drifts
Solution Approach 1:
The patent employs a double-gate transistor structure where the first gate and second gate can independently control the threshold voltage. By dynamically adjusting the voltage applied to the first gate and second gate, the transistor's threshold voltage can be modulated to compensate for both negative and positive drifts, thereby expanding the compensation range beyond the fixed diode-connect mode limitation.
Solution Approach 2:
The invention changes the operating parameters of the transistor by applying different voltages to the first gate and second gate. This parameter control allows the threshold voltage to be adjusted across a wider range, enabling compensation for both negative and positive threshold voltage drifts, thus resolving the limitation of the conventional diode-connect mode which only handles negative drifts.
2Ease of manufacture
If all TFTs in the compensation circuit adopt P-type TFTs in diode-connect mode, then circuit implementation is simplified, but compensation effectiveness varies under different gray levels
Solution Approach 1:
The patent applies different voltage conditions to different gates of the same transistor structure depending on the operating phase. During compensation phase, specific voltage combinations are applied to the first and second gates to achieve uniform threshold voltage compensation across all gray levels, while maintaining the overall simplicity of using only P-type TFTs in the circuit implementation.
3Adaptability or versatility
If a double-gate structure transistor is used with dynamic gate control, then compensation range is broadened to include positive drifts, but circuit complexity increases
Solution Approach 1:
The double-gate transistor structure serves multiple functions: it can operate in conventional mode for normal driving, switch to compensation mode for threshold voltage correction, and provide uniform compensation across different gray levels. This multi-functionality justifies the increased structural complexity by eliminating the need for separate compensation circuits and achieving broader compensation range with a single integrated structure.
Data Source
AI summary
The present application discloses a pixel compensation circuit and a display panel. By adopting a double-gate structure transistor as a driving transistor, a top gate and a bottom gate can respectively regulate channels to realize a dynamic adjustment of a threshold voltage of the driving transistor. Detection of the threshold voltage by a diode-connect mode can be realized by controlling the driving transistor. Real-time compensation of the threshold voltage can be realized, and compensation of a positive drift and a negative drift of the threshold voltage can also be realized, which effectively improves uniformity of image display under a same grayscale.