LCD Driving Device White Image Power-Down After-Image Removal
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Liquid crystal displays (LCDs) suffer from after-image issues due to accumulated electric charges, which degrade image display quality, especially when pixels are turned OFF and the charges are not fully discharged.
Innovation Solution
A driving device with a signal controller, voltage selector, gray-scale voltage generator, and data driver that dynamically adjusts voltage levels during normal and power-down modes, generating different gray-scale voltages to ensure complete discharge of electric charges by displaying a white image during power-down, thereby preventing after-images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If data voltages with the same polarity and voltage level are applied to pixels during consecutive frames, then power consumption is reduced, but electric charges accumulate in the liquid crystal layer causing after-image
Solution Approach 1:
The patent applies preliminary action by displaying a white image (all pixels at maximum brightness) during the power-down period before the user actually turns off the display. This pre-discharge of accumulated electric charges through maximum voltage application eliminates after-images that would otherwise appear when the user subsequently turns off the display, while still maintaining power-saving benefits during the power-down mode.
2Use of energy by moving object
If the LCD is turned OFF to save power, then power consumption is reduced, but accumulated electric charges are not discharged causing after-image to remain
Solution Approach 1:
The patent converts the harmful effect of accumulated electric charges into a beneficial outcome by using the power-down period to display a white image that actively discharges these charges. What would normally be a problem (charge accumulation during power-saving mode) is transformed into an opportunity to eliminate after-images, thereby converting a harmful factor into a beneficial function.
3Adaptability or versatility
If normal gray-scale voltages are used during power-down mode, then display flexibility is maintained, but electric charges are not completely discharged leading to after-image
Solution Approach 1:
The patent applies dynamics by dynamically switching between two distinct voltage modes: during active display, normal varying gray-scale voltages are applied to maintain display flexibility and image quality; during power-down mode, a special white image mode is activated where all pixels receive maximum voltage to ensure complete charge discharge. This dynamic adaptation of voltage strategy based on operational state resolves the contradiction between display flexibility and after-image prevention.
Data Source
AI summary
In a driving device, a liquid crystal display having the driving device, and a method of driving the liquid crystal display, the driving device includes a signal controller, a voltage selector, a gray-scale voltage generator, and a data driver. The signal controller outputs a power-down signal indicating an imminent power-off. The voltage selector outputs a common voltage in response to the signal. The gray-scale voltage generator receives the common voltage to generate common gray-scale voltages having a same voltage level as that of the common voltage. The data driver generates common data voltages based on the common gray-scale voltages. The driving device controls a display panel so that the display panel displays a white image in response to the signal. Thus, an after-image after the power-off is removed, therefore improving the display quality of the display panel.