LCD Polarity Inversion Pattern Reduces Power

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Solution Overview

Problem

Liquid crystal display devices with four sub-pixels per pixel face increased power consumption due to high inversion frequency of image signal polarity, which also leads to flicker and potential differences in common electrode potential from the base potential.

Innovation Solution

A liquid crystal display device with a matrix of scan lines and image signal lines, where each pixel includes four sub-pixels of different colors, and the drive circuit outputs image signals in a frame reversal mode, alternating polarities across specific image signal lines to reduce inversion frequency and maintain common electrode potential at a base level.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If dot inversion driving is used to prevent flicker and maintain common electrode potential, then image quality is improved, but power consumption increases due to high inversion frequency

Engineering Contradiction:

Improveimage qualityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The image signal lines are divided into even-numbered lines and odd-numbered lines, with each group inverted independently. This segmentation reduces the overall inversion frequency while maintaining local polarity balance, thereby reducing power consumption while preventing flicker and maintaining common electrode potential stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements periodic polarity inversion at a reduced frequency by inverting only even-numbered image signal lines in alternating frames, rather than inverting all lines every frame. This periodic action maintains the necessary polarity balance to prevent flicker while significantly reducing the inversion frequency and associated power consumption.

Inventive Principle:

Principle #19Periodic action

2Illumination intensity

If the number of sub-pixels per pixel is increased to four colors, then brightness and color quality are improved, but power consumption increases due to higher inversion frequency

Engineering Contradiction:

ImprovebrightnessVSAvoidpower consumption

Core Design Contradiction:

Illumination intensityVSUse of energy by moving object

Solution Approach 1:

By segmenting the inversion operation to apply only to even-numbered image signal lines rather than all lines, the patent reduces the total number of inversions required. This allows the display to maintain high brightness through four sub-pixels per pixel while reducing the power consumption associated with frequent polarity inversion.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS9082357B2LCD display with pixels having RGBW sub-pixels and where power consumption is reduced by using a polarity inversion pattern in which all red sub-pixels in a column have the same polarity

Publication Date: 2015.07.14 PANASONIC INTELLECTUAL PROPERTY CORP OF AMERICA

AI summary

Each image signal line S is connected alternately to a plurality of sub-pixels P positioned on one side of the image signal line S and a plurality of sub-pixels P positioned on the other side. During one frame period, image signals having either one of the positive and negative polarities are input to the first, third, fourth, and sixth image signal lines S1, S3, S4, and S6 of the eight image signal lines S1 to S8 that constitute a unit array of the image signal lines during one frame period, while image signals having the other polarity are input to the remaining image signal lines S2, S5, S7, and S8. According to this liquid crystal display device, it is possible to prevent flicker in image and to prevent the common electrode position from becoming different from the base potential, while preventing increase of power consumption.