Liquid Crystal Display Power Management via VCOM Potential Adjustment
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Solution Overview
Problem
Liquid crystal display devices face challenges in significantly reducing power consumption while maintaining display quality, especially for large-sized reflective or slightly transmissive displays used in signage applications, where existing pause driving techniques do not adequately minimize power consumption without degrading image quality.
Innovation Solution
The implementation of a liquid crystal display device that switches between normal and low power consumption modes by managing the potentials of scanning and video signal lines, maintaining video signal lines in a high impedance state during pause periods, and controlling power source voltages to prevent leakage currents, allowing for a significant reduction in both AC and DC power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If pause driving is adopted to reduce power consumption, then power consumption is reduced, but display quality is degraded
Solution Approach 1:
The patent changes the potential level of the common electrode from a standard drive level to a second level that is closer to the off-state potential during pause periods. This parameter change reduces the voltage difference across the pixel transistor, minimizing leakage current while maintaining display quality. The common electrode potential is dynamically adjusted between a first level during active display and a second level during pause periods, achieving both low power consumption and quality preservation.
2Use of energy by moving object
If drive frequency is reduced to lower power consumption, then power consumption is reduced, but refresh capability is compromised
Solution Approach 1:
The patent implements periodic switching between normal drive mode and pause driving mode. During pause periods, the common electrode potential is adjusted to maintain display quality while minimizing power consumption. This periodic action allows the display to refresh at lower frequencies while maintaining image quality during active periods, effectively resolving the contradiction between refresh capability and power consumption.
3Use of energy by moving object
If IGZO-TFT is used to minimize off-state current, then power consumption is reduced, but leakage current during pause period still affects display quality
Solution Approach 1:
The patent further reduces the common electrode potential from the first level to a second level during pause periods. This additional parameter change works synergistically with the IGZO-TFT's low off-state current characteristics to minimize leakage current. The combined effect of using IGZO-TFT and adjusting the common electrode potential to the second level ensures that leakage current is reduced to a level that does not degrade display quality, while maintaining extremely low power consumption during pause periods.
Data Source
AI summary
In a first transition period during which an operation mode transitions from a normal mode to a low power consumption mode, a VCOM generation unit in a power source IC changes a potential of a common electrode drive voltage VCOM from a potential of a first level (for example, 5 V) to a potential of a second level (for example, 12 V) so that a leakage current flowing through a pixel transistor is not generated during a pause period, a gate driver changes a potential of each gate bus line to 0 V, and a source driver changes a potential of each source bus line to 0 V.