Liquid Crystal Display Sleep Mode Flicker Suppression

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Solution Overview

Problem

Liquid crystal display devices using pause drive methods experience flicker issues due to charge storage caused by uneven impurity ion distribution in the liquid crystal layer, which existing solutions fail to fully address, especially when power is turned off and back on.

Innovation Solution

A liquid crystal display device and method that applies an alternating current voltage to the liquid crystal layer when the power is turned off, using a drive unit and display control unit with polarity bias calculation and balance control to reduce polarity bias and eliminate charge storage, ensuring no flicker occurs upon resuming from a stopped state.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If pause drive is used to reduce power consumption, then power consumption is reduced, but flicker and afterimage are generated due to charge storage

Engineering Contradiction:

Improvepower consumptionVSAvoidflicker and afterimage

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent applies periodic alternating current voltage to the liquid crystal layer during pause periods. The voltage polarity is reversed periodically (e.g., positive for a duration, then negative for a duration) to prevent charge storage. This periodic action ensures that even though the display is in pause mode (reducing power consumption), the liquid crystal molecules are continuously stimulated in alternating directions, preventing the formation of afterimages and flicker while maintaining low power consumption.

Inventive Principle:

Principle #19Periodic action

2Stability of the object's composition

If data voltage is held in pixel capacitance to maintain display image, then display image is maintained, but charge storage causes flicker when power is turned off and on

Engineering Contradiction:

Improvedisplay image stabilityVSAvoidflicker

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The patent applies alternating current voltage during pause periods before the power is completely turned off. This preliminary action of reversing voltage polarity prevents charge storage from accumulating in the liquid crystal layer. When power is turned on again, since no significant charge storage has occurred during the pause period, flicker is minimized. The display control unit manages this voltage application to ensure smooth transitions and maintain image stability.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If TFT with small off-leak current is used to improve display quality, then display quality is improved, but charge storage problem is exacerbated

Engineering Contradiction:

Improvedisplay qualityVSAvoidcharge storage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the reliance on TFT leakage characteristics with an external voltage control mechanism. Instead of depending on the TFT's off-leak current properties (which are small and problematic), the display control unit actively applies alternating current voltage during pause periods to manage charge storage. This substitution of control approach allows the use of high-quality TFTs with small off-leak currents while preventing charge storage issues through active voltage management rather than passive material properties.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The solution effectively suppresses flicker and afterimage generation by ensuring even distribution of impurity ions, reducing power consumption, and maintaining display quality during sleep periods.

Implementation Method 1

the display control unit generates an alternating current voltage, and controls the drive unit to apply the alternating current voltage to the liquid crystal layer

Methodology Applied

Scientific EffectAlternating current voltage effect:

Implementation Method 2

applying an alternating current voltage to the liquid crystal layer to reduce a polarity bias due to a voltage applied to the liquid crystal layer

Methodology Applied

Scientific EffectPolarity bias reduction:

Data Source

PatentUS9953594B2Liquid crystal display device and method for driving same

Publication Date: 2018.04.24 SHARP KK

AI summary

When a SLEEPIN Command is inputted to the liquid crystal display device, the liquid crystal display device controls a source driver and a gate driver to generate an alternating current voltage and apply the generated alternating current voltage to a liquid crystal layer, in order to eliminate charge storage due to impurity ions distributed unevenly due to a polarity bias caused by a voltage applied to the liquid crystal layer until a point of time when the Command is inputted. In this manner, the liquid crystal display device shifts to a sleep period in a state where the charge storage due to the unevenly distributed impurity ions is eliminated. Therefore, when the liquid crystal display device resumes from the sleep period, generation of an afterimage due to burn-in of liquid crystal and generation of a flicker due to deviation of an optimum common voltage do not occur.