Liquid Crystal Display Protection Circuit Power Potential Control
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Solution Overview
Problem
Liquid crystal display devices face challenges in maintaining stable image display and reducing image unevenness when switching between moving and still images due to changes in transistor characteristics, such as threshold voltage shifts, which can lead to increased leakage current and image quality issues.
Innovation Solution
A liquid crystal display device that switches between still and moving image display modes by adjusting the power supply potential for the protection circuit, using a pixel with a transistor and a liquid crystal element, where the image signal input is controlled through a data line, and the power supply potential is set differently for each mode to stabilize image display and reduce unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the frequency of writing image signal to pixel during still image display is reduced, then power consumption is reduced, but image stability may be affected due to transistor leakage current
Solution Approach 1:
The patent applies preliminary action by setting the protection circuit transistor to a specific off-state before still image display begins. By pre-adjusting the transistor characteristics and establishing appropriate potential differences, the system prepares the circuit to minimize leakage current effects during the extended hold period of still images, thereby maintaining image stability while enabling reduced refresh frequency
Solution Approach 2:
The patent changes the electrical parameters of the protection circuit transistor by controlling its off-state potential relative to the data line potential. By adjusting these potential differences and maintaining specific voltage relationships between circuit elements, the system optimizes the transistor's off-state characteristics to reduce leakage current while preserving image hold capability during low-power still image display
2Duration of action of stationary object
If transistors are degraded by long time use or light exposure, then threshold voltage shifts occur, but leakage current in off state increases causing image unevenness
Solution Approach 1:
The patent applies beforehand cushioning by designing the protection circuit to compensate for anticipated transistor degradation. The circuit configuration with specific potential relationships and the control method that maintains appropriate voltage differences prepare the system in advance to counteract leakage current effects, ensuring that even as transistors age or undergo threshold voltage shifts, image uniformity is maintained through the protective circuit architecture
Data Source
AI summary
Provided is a liquid crystal display device having a pixel including a transistor and a liquid crystal element and a protection circuit electrically connected to one of a source and a drain of the transistor through a data line. The protection circuit includes a first terminal supplied with a first power supply potential and a second terminal supplied with a second power supply potential higher than the first power supply potential. In a moving image display mode, an image signal is input from the data line to the liquid crystal element through the transistor, and the first power supply potential is set at the first potential. In a still image display mode, supply of the image signal is stopped, and the first power supply potential is set at the second potential. The second potential is substantially the same as the minimum value of the image signal.