Liquid Crystal Display Common Voltage Segmentation
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Solution Overview
Problem
Active matrix liquid crystal displays face issues with common voltage distortion due to resistance deviations in common lines, leading to horizontal crosstalk, luminance differences, and increased power consumption in data driver ICs.
Innovation Solution
The implementation of a liquid crystal display with separate first and second common voltage generation units, using thin film transistors to connect longitudinal common lines to common electrodes, and forming edge common lines to reduce resistance and dispersion of load, allowing the common voltages to swing in opposite directions, thereby stabilizing the common voltage and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of common lines is increased to match the vertical resolution, then the data voltage can be simultaneously applied to all pixels of one horizontal line, but the load of the common lines increases and resistance deviations cause common voltage distortion
Solution Approach 1:
The patent divides the common voltage supply system into multiple independent common lines (first common line, second common line, etc.), each supplied by separate input sources. This segmentation allows each common line to be independently controlled and reduces the load on individual lines, thereby maintaining common voltage stability while supporting high-resolution displays with simultaneous data writing capability.
2Reliability
If the width of common lines is increased to reduce resistance, then the common voltage distortion is reduced, but the non-display area is exceeded and device complexity increases
Solution Approach 1:
Instead of using a single wide common line that would consume excessive non-display area, the patent segments the common voltage supply into multiple narrower common lines. This approach achieves the same current distribution effect without requiring excessive width in any single line, thus fitting within the available non-display area while maintaining voltage stability.
Solution Approach 2:
The patent combines multiple common lines (first common line, second common line, etc.) to collectively supply common voltage to the entire display panel. By merging the functionality of multiple lines, the system achieves the voltage distribution capability of a single wide line while using narrower individual lines that fit within the non-display area constraints.
3Device complexity
If a DC level common voltage is used, then the liquid crystal driving voltage is simplified, but the data driver IC requires higher output voltage and power consumption increases
Solution Approach 1:
The patent employs periodic switching of common voltage levels (first common voltage and second common voltage) synchronized with the data writing operation. This periodic action allows the data driver IC to operate with lower output voltage requirements by utilizing the time-varying nature of the common voltage, thereby reducing power consumption while maintaining simplified voltage level structure.
Data Source
AI summary
A liquid crystal display includes a liquid crystal display panel on which a plurality of first units each including at least one liquid crystal cell and a plurality of second units each including at least one liquid crystal cell are positioned in a display area and data line and gate lines cross one another, a common voltage generation unit generating first and second common voltages, a plurality of first longitudinal common lines that supply the first common voltage input through a plurality of first input units to each of first common electrodes of the first units, and a plurality of second longitudinal common lines that supply the second common voltage input through a plurality of second input units to each of second common electrodes of the second units.