Liquid-Crystal Display Pulldown Voltage Correction Circuit

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Solution Overview

Problem

In large-sized liquid-crystal display apparatuses, the pulldown voltage and optimum counter potential vary significantly across different locations due to bluntness in the scanning signal waveform, leading to issues like flickering, burn-in, and luminance unevenness, which existing technologies struggle to address effectively.

Innovation Solution

A liquid-crystal display apparatus with a pulldown voltage correction circuit that includes adjustment capacitors corresponding to each video signal line, where the potential of the adjustment capacitors is raised before the scanning signal falls, allowing for the cancellation of pulldown voltage variations across the display, ensuring a constant optimum counter potential.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single common electrode potential is applied to the entire display, then the device complexity is reduced, but the display quality deteriorates due to luminance unevenness and flickering in different regions

Engineering Contradiction:

Improvecommon electrode potential controlVSAvoiddisplay quality consistency

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent divides the display into multiple regions (first region and second region) along the gate bus line direction, with each region having its own adjustable common electrode potential. This segmentation allows independent optimization of each region's display quality while maintaining overall system functionality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different common electrode potentials to different regions of the display based on their specific characteristics. The first common electrode potential is applied to the first region and the second common electrode potential is applied to the second region, allowing each region to have optimized display quality according to its local requirements.

Inventive Principle:

Principle #3Local quality

2Reliability

If the common electrode potential is optimized for one region, then the display quality in that region is improved, but the display quality in other regions deteriorates

Engineering Contradiction:

Improvedisplay quality in specific regionVSAvoiddisplay quality across all regions

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The display is segmented into multiple regions with independently controllable common electrode potentials, allowing each region to be optimized without affecting others. This resolves the conflict between regional optimization and overall adaptability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The common electrode potentials for different regions can be dynamically adjusted based on operating conditions such as temperature and drive voltage. This dynamic adjustment capability allows the system to maintain optimal display quality across all regions under varying conditions.

Inventive Principle:

Principle #15Dynamics

3Manufacturing precision

If the scanning signal waveform is maintained sharp across the entire gate bus line, then the writing precision is improved, but the device complexity increases due to signal degradation compensation

Engineering Contradiction:

Improvewriting precisionVSAvoidsignal waveform control

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

Different common electrode potentials are applied to different regions to compensate for local signal degradation. This local compensation approach maintains sharp scanning signal waveforms where needed without requiring complex global signal management.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses the liquid crystal capacitor to store and maintain the video signal voltage after the scanning signal falls. This copying mechanism preserves the writing precision achieved during the high-level scanning signal period without requiring continuous sharp signal maintenance.

Inventive Principle:

Principle #26Copying

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 effectively controls the pulldown voltage variations, preventing flickering, burn-in, and luminance unevenness, thereby improving the overall display quality by maintaining a consistent optimum counter potential across the entire display.

Implementation Method 1

a liquid-crystal capacitor Clc which is created by the pixel electrode 72 and the common electrode 73

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

the presence of parasitic capacitance Cgd between the pixel electrode 72 and the gate bus line GL

Methodology Applied

Scientific EffectParasitic capacitance: Parasitic Capacitance

Data Source

PatentUS11776500B2Liquid-crystal display apparatus and driving method

Publication Date: 2023.10.03 SHARP DISPLAY TECHNOLOGY CORP

AI summary

Multiple adjustment capacitors corresponding to multiple source bus lines on a one-to-one correspondence basis are arranged. Each adjustment capacitor includes a first electrode supplied with an adjustment signal and a second electrode connected to the source bus line. The adjustment capacitors are divided into multiple groups. An adjustment signal having a amplitude different from group to group is supplied to the adjustment capacitor. A potential of the adjustment signal is raised after a liquid-crystal capacitor is charged in a pixel formation region including a thin-film transistor (TFT) that is turned on with a gate driver causing a scanning signal to rise and before the gate driver causes the scanning signal to fall.