Liquid Crystal Display Driving Method for Flicker and DC Image Sticking
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Solution Overview
Problem
Liquid crystal displays suffer from flickers and DC image sticking, which degrade display quality by causing residual images and brightness differences, particularly in interlace methods where one polarity of data voltage dominates for extended periods.
Innovation Solution
The implementation of a liquid crystal display driving method that involves a data voltage polarity control system, where the first liquid crystal cell group maintains a polarity for two frame periods to prevent DC image sticking, and the second group inverts polarity every two frame periods to increase spatial frequency and reduce flickers, along with a modulation of the scanning pulse to optimize the common voltage and minimize shimmering noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If data voltage polarity is inverted every frame period to reduce DC offset, then DC image sticking is reduced, but flicker increases due to insufficient spatial frequency
Solution Approach 1:
The liquid crystal display panel is divided into first and second liquid crystal cell groups that are driven at different frequencies. The first group operates at a lower frequency with polarity maintained for two frame periods, while the second group operates at a higher frequency with polarity inverted every frame period. This segmentation allows different regions to address different aspects of the problem, with the first group reducing DC image sticking and the second group reducing flicker.
Solution Approach 2:
Different driving schemes are applied to different spatial regions of the display panel. The first liquid crystal cell group uses a polarity maintenance scheme for DC offset reduction, while the second liquid crystal cell group uses a polarity inversion scheme for flicker reduction. This local differentiation allows each region to optimize for its specific requirement.
2Object-generated harmful factors
If polarity is maintained for two frame periods to prevent DC image sticking, then DC image sticking is reduced, but flicker increases due to reduced spatial frequency
Solution Approach 1:
The display panel is segmented into two groups of liquid crystal cells with different driving frequencies. The first group maintains polarity for two frame periods to prevent DC image sticking, while the second group inverts polarity every frame period to maintain high spatial frequency and reduce flicker. This segmentation enables simultaneous optimization for both objectives.
Solution Approach 2:
The patent combines two different driving schemes in a single display system. The first and second logic circuits generate different polarity control signals that are merged into a unified driving system. The common voltage is also modulated to work in conjunction with both groups, creating a combined solution that addresses both DC image sticking and flicker.
3Speed
If scanning pulse voltage is increased to improve switching speed, then response time is reduced, but shimmering noise increases
Solution Approach 1:
The common voltage is modulated periodically at specific timing within the frame period. The modulation occurs at a frequency that is synchronized with the scanning pulse, creating a periodic action that counteracts the shimmering noise effect. This periodic modulation allows the system to maintain high switching speed while reducing noise through timed voltage adjustments.
Solution Approach 2:
The common voltage parameter is dynamically changed through modulation to compensate for the effects of high scanning pulse voltage. By adjusting the common voltage in a periodic manner, the system maintains optimal switching speed while reducing the shimmering noise that would otherwise result from high voltage pulses.
Data Source
AI summary
A liquid crystal display includes a liquid crystal display panel including a plurality of data lines, a plurality of gate lines crossing the plurality of data lines, and a plurality of liquid crystal cells defined as a first and second liquid crystal cell groups, a data driving circuit to supply a data voltage to the data lines in response to a polarity control signal, a gate driving circuit to supply a scanning pulse that swings between a gate high voltage and a gate low voltage to the gate lines, a first logic circuit to generate the polarity control signal differently for each frame period to maintain a polarity of the data voltage charged in the first liquid crystal cell group, and to invert one time a polarity of the data voltage charged in the second liquid crystal cell group for two frame periods, and a second logic circuit to control the gate driving circuit to decrease the gate high voltage of the scanning pulse to a modulated voltage between the gate high voltage and the gate low voltage for a predetermined modulation time.