Liquid Crystal Display Charge Difference Compensation Circuit
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Solution Overview
Problem
Conventional liquid crystal displays using the double rate driving method suffer from reduced picture quality due to differences in charge characteristics between liquid crystal cells, resulting in vertical lines (DIM) of specific colors, which affect the overall image quality.
Innovation Solution
A liquid crystal display that employs a charge difference compensation circuit to generate analog gamma voltages with specific reference and compensation levels, synchronized with scan times, to equalize the charge characteristics across liquid crystal cells, thereby improving picture quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the double rate driving method is used to reduce the number of data drive ICs, then the device complexity is reduced, but picture quality deteriorates due to charge difference between liquid crystal cells
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the gamma voltage levels based on the scan time. Specifically, when scanning odd-numbered gate lines, a first gamma voltage is applied, while when scanning even-numbered gate lines, a second gamma voltage is applied. This parameter variation compensates for the charge difference between liquid crystal cells, resolving the contradiction between reducing device complexity and maintaining charge uniformity.
2Device complexity
If the double rate driving method is used to halve the number of data lines, then the device complexity is reduced, but vertical lines (DIM) appear in the display
Solution Approach 1:
The patent converts the harmful charge difference effect into a beneficial compensation mechanism. By intentionally applying different gamma voltages for odd and even gate line scans, the patent transforms the charge difference problem into a controlled compensation strategy that eliminates vertical lines while maintaining the reduced data line configuration.
3Manufacturing precision
If gamma voltage is adjusted to compensate for charge difference, then picture quality is improved, but the control complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the gate lines into odd-numbered and even-numbered groups, and applying different gamma voltages to each group. This segmentation approach simplifies the control logic compared to a fully dynamic adjustment system, as it only requires distinguishing between odd and even scan times rather than continuously monitoring and adjusting for each individual cell.
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 compensates for charge differences between liquid crystal cells, reducing the occurrence of vertical lines and enhancing overall picture quality by selectively adjusting gamma voltages in specific gray level ranges.
Implementation Method 1
a charge difference compensation circuit configured to generate, in a specific gray level range, analog positive gamma voltages having a first reference level and analog negative gamma voltages having a second reference level in synchronization with a first scan time at which the first gate line is driven, and generate the analog positive gamma voltages having a first compensation level that is lower than the first reference level and the analog negative gamma voltages having a second compensation level that is higher than the second reference level in synchronization with a second scan time at which the second gate line is driven
Implementation Method 2
A liquid crystal display is configured to display images by controlling the light transmissivity of a liquid crystal layer using an electric field supplied to the liquid crystal layer in response to a video signal
Implementation Method 3
When the scan pulse is supplied to the gate line GL, the TFT is turned on and a channel is formed between the source electrode and the drain electrode, so the voltage of the data line DL is supplied to the pixel electrode of the liquid crystal cell Clc
Implementation Method 4
the storage capacitor Ct is charged with the data voltage supplied from the data line DL, thus functioning to constantly maintain the voltage of the liquid crystal cell Clc
Data Source
AI summary
This document relates to a liquid crystal display capable of improving picture quality by compensating for difference in charge between liquid crystal cells. The liquid crystal display comprises a liquid crystal display panel; a gate driving circuit; a charge difference compensation circuit configured to generate, in a specific gray level range, analog positive gamma voltages having a first reference level and analog negative gamma voltages having a second reference level in synchronization with a first scan time at which a first gate line is driven, and generate the analog positive gamma voltages having a first compensation level that is lower than the first reference level and the analog negative gamma voltages having a second compensation level that is higher than the second reference level in synchronization with a second scan time at which a second gate line is driven; and a data driving circuit.