Liquid Crystal Display Driver Offset Voltage Control
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Solution Overview
Problem
Liquid crystal displays experience afterimages due to residual direct current (DC) voltage and luminance differences caused by kickback voltage variations with grayscale levels, leading to flicker and visibility issues.
Innovation Solution
A liquid crystal display system that adjusts pixel voltages by controlling offset values for black, white, and intermediate grayscales, ensuring the difference between offset values for black and white grayscales is less than 50 mV and greater than 20 mV for intermediate grayscales, using a signal controller and data driver to generate data voltages with positive and negative components, and incorporating a polymer alignment layer formed from cyclobutane dianhydride (CBDA) or its derivatives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data voltage is applied to the pixel, then the pixel voltage is generated to control liquid crystal molecules, but the kickback voltage reduces the data voltage and causes afterimage and flicker
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the common voltage based on the data voltage polarity and grayscale level. The common voltage is set to different values (first common voltage for positive data voltage, second common voltage for negative data voltage) to compensate for kickback voltage effects. This voltage parameter adjustment eliminates the harmful afterimage and flicker while maintaining stable display performance.
2Illumination intensity
If common voltage is applied to the common electrode, then the electric field is generated in the liquid crystal layer, but the kickback voltage causes luminance difference and afterimage
Solution Approach 1:
The patent implements feedback by continuously monitoring the data voltage polarity and grayscale level, then adjusting the common voltage accordingly. The system uses the kickback voltage information to feed back and modify the common voltage application, ensuring luminance uniformity and eliminating afterimage effects through adaptive voltage compensation.
3Adaptability or versatility
If data voltage with different polarities is applied for each frame, then the kickback voltage changes with grayscale level, but this causes visible flicker and afterimage
Solution Approach 1:
The patent applies dynamics by making the common voltage adaptive rather than static. The common voltage changes dynamically based on the data voltage polarity and grayscale level in real-time. This dynamic adjustment allows the system to maintain display stability across different grayscale levels and frame sequences, eliminating flicker and afterimage while preserving grayscale control versatility.
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 reduces afterimage visibility by managing offset differences and kickback voltage effects, improving display stability and reducing DC charge variations across grayscale transitions.
Implementation Method 1
The liquid crystal display applies a voltage to the field generating electrodes to generate an electric field in the liquid crystal layer, determine alignment of liquid crystal molecules of the liquid crystal layer by the electric field
Implementation Method 2
the first alignment layer may include a polymer formed using at least one of a cyclobutane dianhydride ('CBDA') and a CBDA derivative
Data Source
AI summary
A device for driving a liquid crystal display, in which a pixel voltage is reduced by a kickback voltage variable according to grayscales, includes: a signal controller which receives an input image signal corresponding to a grayscale; an image signal corrector which corrects the input image signal and generates a data input signal; and a data driver which supplies a data voltage corresponding to the grayscale based on the data input signal, where the grayscale includes black, white grayscale and intermediate grayscales, the data voltage includes positive and negative voltages, and when a difference between a sum of the positive and negative voltages and a common voltage is defined an offset value, a first offset value corresponding to the black grayscale, a second offset value corresponding to the white grayscale and a third offset value corresponding to the intermediate grayscale satisfy the inequation: |first offset value−second offset value|≦50 mV.