Array Substrate Control Circuit for LCD Voltage Symmetry
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Solution Overview
Problem
Wide viewing angle color shift and image sticking issues in Vertical Alignment (VA) large-scale LCDs due to asymmetric voltage ratios between positive and negative half cycles in conventional TFT-LCDs.
Innovation Solution
Incorporating a control circuit with capacitors structured similarly to existing capacitors, where the second capacitor has a larger capacitance during the positive half cycle and a smaller capacitance during the negative half cycle, ensuring the effective capacitance remains the same for both polarities, thus maintaining equal voltage ratios between pixel electrodes and the common electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-capacitor control circuit is used, then the circuit structure is simple, but the voltage ratios between positive and negative half cycles are asymmetric causing color shift and image sticking
Solution Approach 1:
The patent divides the single capacitor into two separate capacitors (first capacitor and second capacitor) with different capacitance values. The first capacitor has larger capacitance during the positive half cycle, while the second capacitor has larger capacitance during the negative half cycle. This segmentation allows independent optimization of voltage ratios for each half cycle, resolving the asymmetry problem while maintaining reasonable circuit complexity.
Solution Approach 2:
The patent implements dynamic capacitance switching where the effective capacitance changes based on the polarity of the driving voltage. During the positive half cycle, the first capacitor is activated; during the negative half cycle, the second capacitor is activated. This dynamic adaptation ensures optimal voltage ratios are maintained for both polarities, eliminating color shift and image sticking issues.
2Reliability
If different capacitance values are used for positive and negative half cycles, then symmetric voltage ratios are achieved, but the capacitor structure becomes more complex
Solution Approach 1:
The patent merges the functionality of two different capacitors into a single integrated control circuit structure. Both the first and second capacitors are connected to the same pixel electrode through switching transistors, allowing the circuit to achieve symmetric voltage ratios without requiring physically separate capacitor structures for each half cycle.
Solution Approach 2:
The patent changes the capacitance parameter dynamically based on the driving voltage polarity. By selecting different capacitance values (first capacitance for positive half cycle, second capacitance for negative half cycle) through electronic switching, the system achieves optimal voltage ratios without permanent structural complexity.
3Ease of manufacture
If asymmetric voltage ratios are used in pixel electrodes, then color shift occurs in wide viewing angles, but maintaining equal voltage ratios reduces color shift performance
Solution Approach 1:
The patent implements a feedback mechanism where the capacitance values are specifically designed to compensate for the voltage division ratios. By calculating the required capacitance values based on the desired voltage ratios (first voltage ratio for positive half cycle, second voltage ratio for negative half cycle), the system achieves precise voltage control that maintains equal effective voltage ratios across both polarities, eliminating color shift while preserving manufacturing simplicity.
Data Source
AI summary
An array substrate including a plurality of pixel cells, at least one common electrode line, at least one data line, and at least one first scanning line and second scanning line parallel to the first scanning line is disclosed. The first scanning line and the second scanning line intersect with the data line. The pixel cell includes a first pixel electrode, a second pixel electrode, a first transistor, a second transistor, a third transistor, and a control circuit. In addition, a liquid crystal display is also disclosed. By adding one control circuit, the color shift effect in wide viewing angle is enhanced and the image sticking is eliminated.