Liquid Crystal Display Pixel Driving Bias Signal Compensation
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Solution Overview
Problem
In liquid crystal displays, significant parasitic capacitances lead to inconsistent gray levels due to voltage changes, particularly in high-end applications like In-Cell Touch panels and high aperture ratio designs, where traditional storage capacitors fail to maintain balanced charge distribution.
Innovation Solution
A pixel driving method that involves providing a synchronized bias signal with an amplitude larger than the common voltage signal to the storage capacitor, ensuring consistent charge distribution and gray levels, independent of the liquid crystal capacitor's capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a storage capacitor Cst is configured on common structure to balance charge distribution, then gray level consistency is improved, but the problem is not completely solved when significant parasitic capacitances exist
Solution Approach 1:
The patent changes the voltage parameter by introducing a bias signal with amplitude larger than the common voltage signal. This parameter change allows the storage capacitor to compensate for parasitic capacitances and maintain proper charge distribution, resolving the issue where traditional common structure modulation failed to achieve gray level consistency.
2Ease of manufacture
If Vcom modulation is applied to reduce output voltage range and save source driver cost, then device cost is reduced, but gray level inconsistency and flick occur when TFT turns off and common voltage changes
Solution Approach 1:
The patent introduces a bias signal as an intermediary to the storage capacitor, which mediates between the common voltage signal and the parasitic capacitances. This intermediary mechanism allows Vcom modulation to maintain its cost-saving benefits while the bias signal compensates for the gray level inconsistency and flick issues.
3Area of stationary object
If pixel electrode partially covers adjacent data lines and gate lines to increase aperture ratio, then aperture ratio is improved, but parasitic capacitance increases causing gray level inconsistency
Solution Approach 1:
The patent converts the harmful parasitic capacitance caused by the high aperture ratio design into a manageable parameter. By introducing the bias signal with amplitude larger than the common voltage signal, the storage capacitor can compensate for the parasitic capacitance effects, allowing the high aperture ratio design to maintain gray level consistency.
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 effectively compensates for parasitic capacitances, maintaining consistent gray levels and reducing transmittance loss by ensuring the voltage difference between the node P and common voltage source is fixed, regardless of the liquid crystal capacitor's capacitance variations.
Implementation Method 1
a storage capacitor CST, whose one end is electrically connected to a bias voltage source and the other end is electrically connected to the pixel electrode
Implementation Method 2
a liquid crystal capacitor CLC, whose one end is electrically connected to the pixel electrode and the other end is electrically connected to a common voltage source
Data Source
AI summary
The present invention provides a pixel driving method for a liquid crystal display. The pixel includes a storage capacitor and a liquid crystal capacitor. The pixel driving method includes steps of: providing a common voltage signal to a liquid crystal capacitor, and providing a bias signal to a storage capacitor wherein the bias signal is synchronized with the common voltage signal and the amplitude of the bias signal is larger than that of the common voltage signal.