Power Supply Circuit for LCD Common Electrode Voltage Stabilization
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Solution Overview
Problem
Active matrix type LCD panels face challenges in reducing power consumption while maintaining high display quality, particularly due to flickering phenomena caused by changes in common electrode voltage when the number of scan lines in each frame differs, leading to deteriorated image quality.
Innovation Solution
A power supply circuit that generates a boost voltage through a charge-pump operation in synchronization with a charge clock signal, outputting high-potential-side or low-potential-side voltages to the common electrode, with the charge clock signal having rising and falling edges aligned with voltage polarity changes between pixel and common electrodes, ensuring constant voltage levels across frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the charge-pump operation cycle is set to two lines (two horizontal scan periods) to generate high power supply voltage for gate line, then power consumption is reduced, but the common electrode voltage changes every two lines causing flickering and display quality deterioration
Solution Approach 1:
The patent applies dynamics by making the common electrode voltage generation adaptable to different frame structures. The system dynamically adjusts the charge-pump operation timing and common electrode voltage switching to match the actual frame structure (odd or even number of scan lines), rather than using a fixed two-line cycle. This dynamic adaptation eliminates flickering while maintaining power efficiency.
Solution Approach 2:
The patent changes the timing parameters of the charge-pump operation and common electrode voltage switching to resolve the contradiction. By adjusting when the charge-pump operates and when the common electrode voltage switches, the system synchronizes these operations with the actual frame structure, preventing voltage changes that cause flickering while maintaining the power-saving two-line cycle operation.
2Adaptability or versatility
If the number of scan lines in each frame alternates between even and odd (as in NTSC video signal) to accommodate television signal requirements, then adaptability to television signal is improved, but the voltage applied to liquid crystal changes depending on frame causing flickering
Solution Approach 1:
The patent makes the display driver circuit dynamic by detecting the actual frame structure (whether it has an odd or even number of scan lines) and adjusting the common electrode voltage switching timing accordingly. This dynamic adjustment ensures that voltage changes occur at appropriate times regardless of frame type, eliminating flickering while maintaining full compatibility with NTSC television signals that use alternating odd/even frame structures.
Solution Approach 2:
The patent implements feedback by monitoring the frame structure and using this information to control the timing of common electrode voltage changes. The system receives feedback about whether the current frame has an odd or even number of scan lines, and based on this feedback, adjusts the voltage switching timing to prevent flickering, thus maintaining display quality across different television signal formats.
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 solution stabilizes display quality by suppressing flickering and maintaining consistent voltage levels, preventing image quality deterioration even when the number of scan lines in each frame varies.
Implementation Method 1
a voltage booster circuit that generates a boost voltage boosted by a charge-pump operation in synchronization with a charge clock signal
Data Source
AI summary
A power supply circuit which outputs a common electrode voltage to a common electrode of an electro-optical device provided opposite to pixel electrodes through an electro-optical material includes a voltage booster circuit which generates a boost voltage boosted by a charge-pump operation in synchronization with a charge clock signal, and a common electrode voltage generation circuit which outputs a high-potential-side voltage or a low-potential-side voltage generated based on the boost voltage to the common electrode as the common electrode voltage. The charge clock signal has a rising edge and a falling edge in a period in which a sign of voltages between the pixel electrode and the common electrode are either positive or negative.