LCD Common Voltage Compensator for Uniform Brightness
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Solution Overview
Problem
Liquid crystal display devices experience picture quality deterioration due to brightness differences between horizontal line blocks caused by line resistance variations in the LOG-type common lines, leading to horizontal brightness bands.
Innovation Solution
Incorporating attenuating resistors with a large resistance value at the input terminals of the LOG-type common lines, connected in series with the line resistances, to equalize the resistance loaded onto the input terminals of the gate drive ICs, thereby ensuring a consistent common voltage signal is applied to each gate drive IC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If LOG-type common lines are used to supply common voltage to gate drive ICs, then the liquid crystal display device can be manufactured with thinner profile and eliminated gate PCB, but line resistance variations cause brightness differences between horizontal line blocks
Solution Approach 1:
The patent applies different resistance values to different segments of the common voltage signal path. Specifically, compensating resistors are added at specific locations (e.g., at gate drive ICs farther from the power supply) to equalize the voltage received by each gate drive IC. This local adjustment compensates for the cumulative line resistance effects, ensuring uniform common voltage across all horizontal line blocks while maintaining the thin-profile LOG architecture.
2Device complexity
If common voltage is supplied through long LOG-type common lines, then gate PCB can be eliminated, but voltage drops due to line resistance cause horizontal brightness bands
Solution Approach 1:
The patent introduces compensating resistors as intermediary elements in the common voltage signal path. These resistors are strategically placed at gate drive ICs that receive degraded voltage due to line resistance. The compensating resistors form a voltage divider with the line resistance, allowing precise adjustment of the voltage received by each gate drive IC to match the ideal common voltage level, thereby eliminating brightness bands.
3Reliability
If line resistance of common lines is reduced, then voltage consistency improves, but manufacturing precision requirements increase
Solution Approach 1:
Instead of attempting to precisely control the line resistance parameter during manufacturing (which would require high precision), the patent changes the approach by adding compensating resistors with specific resistance values. These compensating resistors are designed to offset the measured or estimated line resistance effects. By changing from a precision-manufacturing approach to a compensation approach, the system achieves voltage consistency without demanding extreme manufacturing precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution reduces the impact of line resistances on the voltage supplied to each gate drive IC, preventing brightness differences between horizontal line blocks and enhancing picture quality by ensuring uniform common voltage distribution.
Implementation Method 1
Incorporating attenuating resistors with a large resistance value at the input terminals of the LOG-type common lines, connected in series with the line resistances, to equalize the resistance loaded onto the input terminals of the gate drive ICs
Data Source
AI summary
A liquid crystal display device and a driving method thereof for preventing a brightness difference between horizontal line blocks are disclosed. In the liquid crystal display device, a liquid crystal display panel has a liquid crystal cell matrix. A power supply generates a common voltage. Common lines directly on a substrate of the liquid crystal display panel are connected to a common electrode of the liquid crystal cell. A common voltage compensator compensates for the common voltage into a large resistance value with a resistance value greater than a combination of resistances of the common lines and the large resistance directly between the power supply and the common lines.