LCD Driving Circuit Segmentation for Flicker Reduction
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Solution Overview
Problem
Liquid crystal display (LCD) devices experience picture quality issues such as flickering and residual images due to an imbalance in electric charge caused by differing potential differences between gate and data voltages, leading to inefficient operation of thin film transistors.
Innovation Solution
A liquid crystal display device with first and second switching devices that manage gate and data signals to maintain a consistent turn-on state, using a bootstrapping method to equalize potential differences between positive and negative video signals, ensuring balanced electric charge across the liquid crystal cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional LCD driving circuit uses a single thin film transistor to apply data voltage to the liquid crystal cell, then the device structure remains simple, but picture quality deteriorates due to flickering and residual images caused by electric charge imbalance
Solution Approach 1:
The patent divides the single switching device into two separate thin film transistors: a first switching device for applying data voltage and a second switching device for applying gate signal. This segmentation allows independent optimization of each transistor's function, enabling balanced electric charge control while maintaining manageable device complexity through modular architecture.
Solution Approach 2:
The patent implements dynamic control of the two switching devices with different on-times adapted to the polarity of video signals. The first switching device remains on during the entire horizontal period, while the second switching device's on-time varies based on signal polarity to compensate for electric charge imbalance, thereby eliminating flickering and residual images.
2Reliability
If the gate signal and data voltage are applied with different potential differences, then the thin film transistor operates efficiently, but electric charge imbalance occurs causing flickering and residual images
Solution Approach 1:
The patent employs dynamic driving waveforms where the on-time of the second switching device varies according to the polarity of the video signal. During positive video signal periods, the second switching device is turned on longer; during negative periods, it is turned on shorter, thereby dynamically compensating for electric charge imbalance and eliminating display defects.
Solution Approach 2:
The patent changes the operating parameters of the switching devices by adjusting their on-times based on video signal polarity. This parameter modulation allows the system to maintain balanced electric charge in the liquid crystal cell while managing the complexity of driving waveforms through systematic temporal control.
3Reliability
If the thin film transistor is turned on and off sequentially to charge and maintain data voltage, then the liquid crystal cell updates efficiently, but picture quality deteriorates due to potential difference variation between positive and negative data voltages
Solution Approach 1:
The patent implements asymmetric on-times for the two switching devices that adapt dynamically to the video signal polarity. The first switching device operates throughout the entire horizontal period while the second switching device's on-time is extended during positive signal periods and reduced during negative signal periods, maintaining efficient data voltage charging while ensuring balanced electric charge for high picture quality.
Data Source
AI summary
A liquid crystal display device and a driving method thereof for improving a picture quality are disclosed. In the liquid crystal display device, a plurality of liquid crystal cells is provided at crossings of a plurality of data lines and a plurality of gate lines. A first switching device supplies a voltage from the data line to the liquid crystal cell in response to a voltage at a control terminal. A second switching device applies a gate signal at the ith gate line (wherein i is an integer) to the control terminal in response to a voltage at the (i−1)th gate line, thereby charging said voltage of the control terminal.