LCD Driving Method for Brightness Uniformity via Polarity Inversion
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Solution Overview
Problem
The issue of brightness unevenness in liquid crystal display panels arises due to increased leakage current in thin film transistors, caused by polarity inversions and the application of negative voltages to uncharged scan lines, leading to non-uniform image brightness across the panel.
Innovation Solution
A driving method for liquid crystal display panels that involves alternating polarity inversion directions in successive frames, coupled with specific voltage application sequences to the scan and data lines, thereby minimizing leakage currents and maintaining uniform brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polarity inversion is applied to prevent liquid crystal polarization, then liquid crystal polarization is prevented, but leakage current increases and brightness uniformity deteriorates
Solution Approach 1:
The patent inverts the conventional scan direction relative to the polarity inversion pattern. Instead of scanning top-to-bottom with fixed polarity inversion timing, the scan direction is reversed (bottom-to-top) while maintaining the same polarity inversion sequence, causing the polarity inversion to occur at different temporal positions relative to the scan progress. This misalignment prevents systematic leakage accumulation at specific panel regions.
Solution Approach 2:
The patent implements periodic alternation of scan directions between frames. Odd frames scan from top to bottom while even frames scan from bottom to top, creating a periodic pattern that distributes leakage effects uniformly across the panel over time. This periodic reversal ensures no single region consistently experiences prolonged leakage conditions.
2Ease of operation
If scan lines apply negative voltage to deactivate transistors, then transistor deactivation is improved, but leakage current increases due to polarity mismatch with uncharged pixel capacitors
Solution Approach 1:
The patent applies preliminary action by pre-charging pixel capacitors with the same polarity as the upcoming scan line voltage before the actual scanning occurs. This ensures that when the scan line activates, the pixel capacitor is already in a voltage state that minimizes leakage current, preventing the harmful effect of polarity mismatch before it can occur.
Solution Approach 2:
The patent dynamically adjusts the timing and polarity of voltage application based on the current scan line position and frame number. The voltage waveform applied to data lines changes dynamically throughout the scanning process, with different polarity sequences applied to different scan lines depending on their position and the current frame's scan direction, optimizing leakage prevention at each moment.
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 proposed method effectively reduces brightness unevenness by compensating for leakage variations across the panel, ensuring more uniform image brightness and improved display performance.
Implementation Method 1
the liquid crystal layer between the pixel electrode and the common electrode... the pixel electrode is constantly to have positive polarity... the liquid crystals cannot be normally twisted in the electric field
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A method for driving a liquid crystal display panel, comprising: inputting, in a first time period and from a first direction, a turn-on voltage to scanning lines (SLI-SLn) in a line-by-line manner, and inputting a pixel voltage of a first polarity to data lines (DLI-DLm) so as to charge a pixel capacitor (Clc) (S 110); inputting, in a second time period and from the first direction, the turn-on voltage to the scanning lines (SLI-SLn) in a line-by-line manner, and inputting a pixel voltage of a second polarity to the data lines (DLI-DLm) so as to charge the pixel capacitor (Clc) (S 120); inputting, in a third time period and from a second direction, the turn-on voltage to the scanning lines (SLI-SLn) in a line-by-line manner, and inputting the pixel voltage of the first polarity to the data lines (DL 1-DLm) so as to charge the pixel capacitor (Clc) (S 130); and inputting, in a fourth time period and : from the second direction, the turn-on voltage to the scanning lines (SLI-Sln) in a line-by-line manner, and inputting the pixel voltage of the second polarity to the data lines (DL 1-DLm) so as to charge the pixel capacitor (Clc) (S 140). The present invention has the advantage of reducing the non-uniformity of the brightness of a picture on a liquid crystal display panel.