Liquid Crystal Display Driving Circuit for Power-Off Artifact Prevention
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Solution Overview
Problem
Existing liquid crystal display devices using line inversion driving methods in IPS or FFS modes face issues with incidental images due to uneven electric discharge times after power-off, leading to lateral line artifacts, and struggle to respond quickly to sudden power failures during black data writing.
Innovation Solution
A liquid crystal display device and driving method that includes a substrate with first and second electrodes, a pixel switch, scan line driving circuit, and control circuits to manage voltage supply lines, allowing simultaneous connection of all signal lines to a first voltage supply line during power-off, ensuring equal potential difference and preventing incidental images by synchronizing the state of liquid crystal molecules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If line inversion driving method is used in IPS or FFS mode, then flicker phenomenon is prevented, but incidental images such as lateral lines are generated due to uneven electric discharge times after power-off
Solution Approach 1:
The patent applies equipotentiality by connecting all second electrodes to a reference potential through resistors during power-off state. This ensures that all pixels discharge electricity at the same rate, preventing potential differences that cause lateral line artifacts while maintaining the line inversion driving method for flicker prevention.
2Reliability
If black data is written sequentially by scan operation, then black display is achieved, but it takes at least one field period which is too slow for sudden power-off
Solution Approach 1:
The patent implements preliminary action by pre-connecting all second electrodes to the reference potential through resistors before power-off occurs. This preliminary configuration allows instantaneous black display response when power is suddenly cut, eliminating the sequential scanning delay of at least one field period.
Solution Approach 2:
The patent merges the black data writing process across all scan lines simultaneously by connecting all second electrodes to the same reference potential. This combines what was previously a sequential operation into a parallel process, achieving black display instantaneously across the entire screen.
3Reliability
If two kinds of voltages with positive and negative are supplied to the second electrode, then polarity inversion for flicker prevention is achieved, but electric discharge time differs between high and low level potentials
Solution Approach 1:
The patent uses equipotentiality by providing a common reference potential path for all second electrodes during power-off. This equalizes the discharge time for both high and low level potentials, ensuring uniform black display across all pixels regardless of their last voltage state.
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 enables rapid black display without incidental images, even during sudden power failures, by ensuring equal potential discharge and reducing the time required for black data writing, thus providing a high-quality display without artifacts.
Implementation Method 1
An alignment state of the liquid crystal molecule contained in the liquid crystal layer is controlled by an electrical field impressed to the liquid crystal layer
Implementation Method 2
the state of an alignment of the liquid crystal molecule contained in the liquid crystal layer is controlled by the lateral electrical field generated between the first and second electrodes
Implementation Method 3
a pixel switch arranged in an intersection portion of the scan line and the column line to switch a connection between the signal line and the first electrode
Data Source
AI summary
A liquid crystal display device includes a plurality of common electrodes arranged so as to counter pixel electrodes extending in the row direction on a substrate. First and second voltage supply lines to supply first and second voltages to the common electrodes are connected with the common electrodes through a first switch circuit. A second switch circuit is arranged between the first voltage supply line and signal lines to switch a connection between the first voltage supply line and the signal lines. A gate open circuit is connected to scan lines to simultaneously supply a signal to switch on the pixel electrodes to all the scan lines. In case the power supply of the liquid crystal display device is turned off, a control circuit starts the power OFF driving operation to set the potential of the pixel electrode and the common electrode to substantially same by switching the first and second switch circuits.