LCD Common Electrode Circuit for Polarity Inversion Switching
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Solution Overview
Problem
Liquid crystal display devices experience display abnormalities such as crosstalk and vertical stripes when switching between normal and low-frequency driving modes, particularly when using two-column and one-column inversion driving methods, leading to potential deterioration in display quality.
Innovation Solution
A liquid crystal display device with a common electrode drive circuit that includes an operational amplifier, resistors, and an adjustment circuit to adjust the combined resistance value based on the polarity inversion driving method, allowing seamless switching between one-column and N-column inversion driving methods without causing display quality deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If switching between polarity inversion driving methods is performed during operation, then adaptability to different display requirements is improved, but display quality deteriorates due to vertical stripes and crosstalk
Solution Approach 1:
The patent changes the resistance value parameter of the feedback resistor based on the polarity inversion driving method being used. When switching from one-column inversion to N-column inversion driving, the resistor value is adjusted to maintain appropriate feedback strength, preventing display abnormalities while enabling flexible driving mode switching.
Solution Approach 2:
The feedback circuit is made dynamic by allowing the resistor value to change according to the driving mode. This dynamic adjustment ensures the feedback mechanism adapts to different operating conditions, maintaining display quality across various polarity inversion driving methods.
2Use of energy by moving object
If low-frequency driving is adopted to reduce power consumption, then energy efficiency is improved, but effective voltage balance deteriorates causing flicker
Solution Approach 1:
The patent employs a feedback circuit that monitors the common electrode voltage and adjusts the output common voltage accordingly. This feedback mechanism compensates for voltage imbalances caused by leakage current differences between normal and low-frequency driving modes, preventing flicker while maintaining low power consumption.
Solution Approach 2:
The output common voltage level is dynamically changed based on the driving mode. During low-frequency driving, the offset voltage setting circuit adjusts the common voltage level to account for different leakage current characteristics, maintaining effective voltage balance across refresh cycles of different lengths.
3Ease of operation
If output common voltage is generated using voltage follower circuit and offset voltage setting circuit, then common voltage control is improved, but in-panel common voltage fluctuates causing crosstalk
Solution Approach 1:
The patent introduces a feedback circuit that feeds back the in-panel common voltage to the operational amplifier. This feedback mechanism detects voltage fluctuations caused by parasitic capacitance and compensates for them in real-time, preventing crosstalk while maintaining ease of common voltage control.
Solution Approach 2:
The feedback resistor value is adjusted based on the polarity inversion driving method to optimize the feedback strength. This parameter change ensures that the feedback mechanism effectively counteracts voltage fluctuations without causing instability, maintaining reliable in-panel common voltage.
Data Source
AI summary
A common electrode driver includes an operational amplifier, a resistor, one end of which is connected to an inverting input terminal of the operational amplifier and the other end of which is connected to an output terminal of the operational amplifier, and an adjustment circuit that is configured to be able to adjust an internal combined resistance value in accordance with an applied polarity inversion driving method. The combined resistance value obtained when a one-column inversion driving method is applied is caused to be smaller than the combined resistance value obtained when a two-column inversion driving method is applied.