LCD Voltage Timing Control for Flicker and Residual Image Elimination
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Solution Overview
Problem
Liquid crystal displays (LCDs) suffer from flicker effects when switched on and residual image effects when switched off due to voltage differences between the common and pixel electrodes, which are not adequately addressed by existing technologies.
Innovation Solution
The implementation of a liquid crystal display with a timing control circuit, common voltage generating circuit, and gamma circuit that ensures the common voltage reaches a predetermined value before gray-scale voltages are applied when powered on, and all voltages drop to 0V simultaneously when powered off, with thin film transistors being switched on to release stored charges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the gray-scale voltage is applied before the common voltage reaches a predetermined value when powered on, then the display can start working faster, but the voltage difference between common and pixel electrodes varies during the preliminary period causing flicker
Solution Approach 1:
The common voltage is applied to the common electrode before the gray-scale voltage is applied to the pixel electrode. This preliminary action ensures that the common voltage reaches a predetermined value before the pixel electrode voltage is applied, preventing voltage difference variation during the preliminary period and eliminating flicker while maintaining fast response speed.
2Loss of energy
If the common voltage slowly drops to 0V when powered off, then the display can be turned off, but the voltage difference still exists between common and pixel electrodes causing residual image
Solution Approach 1:
The thin film transistor is switched on before the common voltage and gray-scale voltage drop to 0V. This preliminary action creates a conductive path that allows both voltages to drop to 0V simultaneously, ensuring complete discharge of the liquid crystal capacitor and eliminating residual image while maintaining low power consumption.
3Reliability
If the thin film transistor is switched on before voltages drop to 0V when powered off, then the stored charges can be released quickly eliminating residual image, but the transistor switching control becomes more complex
Solution Approach 1:
The transistor switching control signal is merged with the power-off timing control. The transistor is switched on automatically when the power-off signal is applied, combining the voltage discharge control with the power-off function. This integration eliminates residual image by ensuring simultaneous drop of common and gray-scale voltages to 0V while avoiding additional complex control circuits.
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 eliminates flicker and residual image issues by maintaining consistent voltage differences and ensuring quick discharge of electric fields, resulting in improved display performance and reduced image retention.
Implementation Method 1
The common voltage Vcom of the common electrode 55 and the gray-scale voltage Vd of the pixel electrode 54 generate an electric field. The strength of the electrical field controls an amount of light beams transmitting through the liquid crystal capacitor 50.
Implementation Method 2
The thin film transistor 53 includes a gate electrode 531 coupled to the gate line 51, a source electrode 532 coupled to the data line 52, and a drain electrode 533 coupled to the pixel electrode 54.
Data Source
AI summary
A liquid crystal display (1) includes a liquid crystal panel (12) including a number of thin film transistors (123), a timing control circuit (16), a common voltage generating circuit (14) and a gamma circuit (13). The timing control circuit is configured for generating timing signals. The common voltage generating circuit is configured for generating a common voltage. The gamma circuit is configured for generating gray-scale voltages. When the liquid crystal panel is powered on, the common voltage is applied to the liquid crystal panel and reaches a predetermined value before the gray-scale voltages are applied to the liquid crystal panel and comes to predetermined values. And when liquid crystal panel is powered off the common voltage and the gray-scale voltages drops to 0V simultaneously by control of the common voltage generating circuit and the gamma circuit with the thin film transistors switched on.