Quad-Pixel LCD Driving Circuit Prevents DC Image Sticking
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Solution Overview
Problem
Active matrix liquid crystal displays suffer from DC image sticking due to prolonged exposure to data voltages of the same polarity, leading to image degradation and distortion, especially in interlaced and scrolling image scenarios.
Innovation Solution
A liquid crystal display with a quad-type pixel structure and a method of driving that involves inverting the polarity of data voltages every three horizontal periods, using a logic circuit to generate polarity control signals with different phases, and a data drive circuit to supply inverted polarities to data lines, along with a gate drive circuit for sequential gate pulses, effectively preventing DC image sticking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data voltage with the same polarity is supplied dominantly to liquid crystal cells for a long time, then image sticking occurs, but continuous polarity inversion may cause flicker
Solution Approach 1:
The patent applies periodic polarity inversion to the data voltage supplied to liquid crystal cells. By inverting the polarity at regular intervals (every frame period or every other line), the system prevents DC image sticking while maintaining stable display. The periodic action ensures that no single polarity dominates for extended periods, eliminating the accumulation effect that causes image sticking.
Solution Approach 2:
The patent dynamically adjusts the polarity of data voltage based on the scanning line and frame period. Different lines or frames receive opposite polarities, creating a dynamic polarity distribution pattern. This dynamic approach prevents static charge accumulation in any particular region, thereby preventing DC image sticking while maintaining overall display stability.
2Productivity
If interlaced data transmission is used, then bandwidth is reduced, but DC image sticking occurs due to dominant polarity supply
Solution Approach 1:
The patent implements periodic polarity inversion specifically tailored for interlaced data transmission. During interlaced scanning, odd lines are displayed in odd frame periods and even lines in even frame periods. The patent applies polarity inversion between these alternating line groups, ensuring that even though data transmission is efficient, the liquid crystal cells do not receive dominant polarity for extended periods, thus preventing DC image sticking.
Solution Approach 2:
The patent applies different polarity patterns to different regions of the display based on the interlaced scanning pattern. Odd lines receive one polarity pattern while even lines receive the opposite pattern, creating localized quality control. This ensures that each region of the display maintains balanced polarity exposure, preventing DC image sticking in specific areas while maintaining overall transmission efficiency.
3Reliability
If polarity inversion frequency is increased, then DC image sticking is prevented, but flicker increases
Solution Approach 1:
The patent uses periodic polarity inversion at the frame rate or half-frame rate, which is synchronized with the display refresh cycle. This periodic inversion prevents DC image sticking by ensuring polarity alternation, but the frequency is kept low enough (matching the refresh rate) to avoid perceptible flicker. The key is that the inversion period matches the natural refresh cycle of the display system.
Solution Approach 2:
The patent maintains continuous display operation by integrating polarity inversion into the normal refresh cycle. The polarity inversion occurs seamlessly as part of the frame-by-frame or line-by-line scanning process, ensuring that the display action continues without interruption or visible flicker. The useful action of displaying images remains continuous while the polarity inversion provides protective alternation.
Data Source
AI summary
A liquid crystal display and a method of driving the same are provided. The liquid crystal display includes a liquid crystal display panel including data lines, gate lines crossing the data lines, and liquid crystal cells and having a quad type pixel structure in which red, green, blue, and white subpixels constitute one pixel, a logic circuit sequentially outputting polarity control signals, a data drive circuit that inverts a polarity of a data voltage in response to the polarity control signals to supply the data voltage with the inverted polarity to the data lines, and a gate drive circuit sequentially supplying gate pulses to the gate lines. A logic level of each of the polarity control signals is inverted every three horizontal periods, and phases of the polarity control signals are different from one another.