Gate Drive Circuit for LCD Flicker Reduction
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Solution Overview
Problem
Liquid crystal display devices experience flicker and residual images due to differences in feed-through voltage when driven in positive and negative polarities, particularly exacerbated by the line inversion method, leading to reduced display quality.
Innovation Solution
The liquid crystal display device employs a gate drive circuit with scan signals of different swing widths for positive and negative data polarities, and an arrangement of switch devices connected to specific gate lines to reduce the feed-through voltage difference, using a shift register and level shifters to adjust the scan signal swing widths based on polarity, and optimizing the gate high voltage levels to minimize voltage offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the line inversion method is used to drive the liquid crystal display, then the liquid crystal cell deterioration is prevented by inverting polarity, but feed-through voltage difference between positive and negative polarities causes flicker and residual images
Solution Approach 1:
The patent changes the voltage parameters of the scan signal by adjusting the gate high voltage level according to the polarity of the data signal. When driving in positive polarity, a first gate high voltage level is applied, and when driving in negative polarity, a second gate high voltage level is applied. This parameter change compensates for the feed-through voltage difference, ensuring that the voltage applied to the liquid crystal cell is consistent regardless of polarity, thereby eliminating flicker and residual images while maintaining the protective polarity inversion effect
Solution Approach 2:
The patent implements a feedback mechanism where the gate drive circuit monitors the polarity of the data signal and adjusts the gate high voltage level accordingly. The controller generates control signals that feedback to the gate driver, enabling it to select the appropriate gate high voltage level based on the current polarity state. This closed-loop feedback ensures that the feed-through voltage difference is continuously compensated, preventing display defects while maintaining reliable liquid crystal cell operation
2Object-affected harmful factors
If different gate high voltage levels are used for positive and negative polarities, then feed-through voltage difference is reduced, but gate driver circuit complexity increases
Solution Approach 1:
The patent introduces dynamic adaptability to the gate driver circuit by enabling it to switch between different gate high voltage levels based on the data signal polarity. The gate driver is designed with dynamic voltage selection capability, where the gate high voltage level is not fixed but varies according to the driving conditions. This dynamic approach allows the circuit to optimize performance for each polarity state without requiring completely separate driver circuits, thereby reducing the overall complexity increase while effectively reducing feed-through voltage difference
Solution Approach 2:
The gate driver circuit is designed with multi-functionality to handle both positive and negative polarity driving modes using a single unified circuit structure. The same gate driver circuit can operate with different gate high voltage levels depending on the polarity requirement, eliminating the need for separate dedicated circuits for each polarity. This universal design approach minimizes the increase in device complexity while achieving the goal of reducing feed-through voltage difference through adaptive voltage control
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 approach significantly reduces the feed-through voltage difference between positive and negative polarities, thereby minimizing flicker and residual images, enhancing display quality by ensuring consistent voltage levels across polarities.
Implementation Method 1
The arrangement of liquid crystal molecules is changed by the electric field formed by the potential difference to control the amount of the transmitted light or to block the light
Data Source
AI summary
A liquid crystal display device and a driving method thereof are provided. The liquid crystal display includes a data driver that is operative to supply data to the data lines. The data have the same polarity for the liquid crystal cells that are adjacent horizontally and opposite polarities for the liquid crystal cells that are adjacent vertically. A gate driver is operative to supply scan signals to the gate lines. The scan signals have different swing widths from each other in accordance with a polarity of the data. The switch devices include a plurality of first switch devices and a plurality of second switch devices. The first switch devices are connected to the (n−1)th (where n is a positive integer of not less than 2) gate line and the second switch devices are connected to the nth gate line.