Gate Drive Compensation for LCD Flickering Elimination

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Solution Overview

Problem

Existing methods for adjusting the common electrode signal in liquid crystal displays to mitigate voltage differences caused by parasitic capacitance are unsatisfactory, leading to flickering and residual images due to incomplete polarity reversal.

Innovation Solution

A gate drive method and device that applies a compensation voltage to each gate line when turned off, maintaining it until the next frame, effectively canceling out voltage differences between pixel and data line voltages by compensating for parasitic capacitance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the common electrode signal Vcom is adjusted by using a feedback loop, then the voltage difference can be compensated, but the adjustment may not be exact due to visual sense dependency, causing insufficient elimination of flickering and residual images

Engineering Contradiction:

Improveaccuracy of Vcom adjustmentVSAvoidcomplexity of feedback loop

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the human visual-sense-based feedback loop with an automatic electrical compensation mechanism. The gate drive circuit automatically generates a compensation voltage Vgc based on the turn-on voltage Vgh and capacitance ratios (Vgc = Vgh × Cgs/Cst), eliminating the need for manual visual adjustment and achieving precise voltage difference compensation without subjective dependency.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The gate drive circuit performs self-compensation by automatically generating and applying the compensation voltage Vgc during the gate line off-period. The circuit uses its own internal capacitances (Cgs and Cst) to calculate and apply the correct compensation amount, making the system self-regulating without external feedback intervention.

Inventive Principle:

Principle #25Self-service

2Measurement precision

If parasitic capacitance is reduced to decrease voltage difference ΔVp, then adjustment effect improves, but ΔVp is reduced only to a limited extent due to charge and discharge requirements

Engineering Contradiction:

Improvevoltage difference compensationVSAvoidmanufacturing constraints on parasitic capacitance

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent converts the harmful effect of parasitic capacitance (which causes voltage difference ΔVp) into a beneficial compensation mechanism. Instead of trying to eliminate parasitic capacitance, the invention uses the known capacitance values (Cgs and Cst) to calculate and apply a compensating voltage Vgc that exactly offsets the voltage difference, turning the problem into a solution.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the approach from modifying physical parameters (reducing parasitic capacitance) to modifying electrical parameters (applying compensation voltage). By changing the gate line voltage characteristics during the off-period, the system achieves precise voltage difference compensation without being constrained by manufacturing limitations on parasitic capacitance values.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If polarity reversion is used to prevent liquid crystal aging, then display reliability improves, but voltage difference ΔVp causes residual direct current and flickering

Engineering Contradiction:

Improveliquid crystal aging preventionVSAvoidflickering and residual images

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary anti-action by compensating for the voltage difference ΔVp before the polarity reversion effect can cause harmful residual direct current. The compensation voltage Vgc is applied during the gate line off-period, proactively eliminating the voltage imbalance that would otherwise lead to flickering and residual images during polarity switching.

Inventive Principle:

Principle #9Preliminary anti-action

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 eliminates flickering and residual images caused by voltage differences, ensuring accurate polarity reversal and improved display quality.

Implementation Method 1

Due to factors such as parasitic capacitance, the actual pixel voltage of the pixel electrode is inconsistent with the data line voltage, and there is a voltage difference ΔVp

Methodology Applied

Scientific EffectParasitic capacitance: Parasitic Capacitance

Data Source

PatentUS9196208B2Gate drive method in which a flickering phenomen is eliminated and gate drive device of liquid crystal display

Publication Date: 2015.11.24 BEIJING BOE OPTOELECTRONCIS TECH CO LTD

AI summary

The embodiments of the present disclosure discloses a gate drive method and a gate drive device of a liquid crystal display, which can avoid the influence by the voltage difference ΔVp between the pixel voltage and the data line voltage, and eliminate the flickering phenomenon and the residual image caused by the residual direct current effectively. The gate drive method of the liquid crystal display comprises: inputting a compensation voltage Vgc to the n-th row of gate line when the n-th row of gate line is turned off completely in the current frame; keep on inputting the compensation voltage Vgc; and stopping inputting the compensation voltage Vgc to the n-th row of gate line when a turn-on voltage Vgh is input to the n-th row of gate line in the next frame; wherein, N≦the total number of the gate lines.