Zero-Bias Display Turn-Off Circuitry for LCD Kickback Voltage
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Solution Overview
Problem
Conventional methods for turning off liquid crystal displays (LCDs) result in residual voltage on pixels, leading to image artifacts such as flickering when the display is turned back on due to kickback voltage.
Innovation Solution
Implementing zero-bias display turn-off circuitry that supplies a Vcom output of ground to the common electrode, activates the pixel with a data signal of ground, and then disconnects the common electrode from the Vcom voltage supply to prevent kickback voltage, thereby maintaining a low residual voltage on the pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional turn-off method is used where pixel electrodes are supplied with minimal voltage, then the display can be turned off, but kickback voltage alters the stored voltage causing residual voltage and image artifacts
Solution Approach 1:
The patent applies preliminary action by switching the common electrode to a second voltage level (e.g., ground) before the pixel electrode voltage is reduced during turn-off. This preemptive voltage level change on the common electrode prevents the kickback voltage from occurring when the TFT gate is deactivated, thereby eliminating the harmful effect on stored pixel data while maintaining reliable display state transition
2Ease of operation
If pixel electrodes are supplied with minimal voltage during turn-off, then the display turns off, but residual voltage remains on pixels causing flickering artifacts
Solution Approach 1:
The common electrode voltage is changed to a second level before the pixel electrode voltage is reduced, preemptively preventing the formation of residual voltage through kickback effects. This maintains ease of operation while eliminating the harmful residual voltage that causes flickering artifacts
Solution Approach 2:
The patent changes the voltage parameter of the common electrode from a first voltage level to a second voltage level (e.g., ground) during the turn-off sequence. This parameter change on the common electrode prevents the kickback voltage from altering the pixel electrode voltage, thereby eliminating residual voltage while maintaining simple turn-off operation
Data Source
AI summary
Methods and devices employing zero-bias display turn-off circuitry, including turn-off logic and switching devices, are provided. In one example, a method may include supplying a common voltage output of ground to a common electrode of a pixel of an electronic display, supplying an activation signal to the pixel to activate the pixel, supplying a data signal of ground to a pixel electrode of the pixel, and removing the activation signal from the pixel while the data signal is being supplied to the pixel to store the data signal in the pixel. When the activation signal is removed, the method may include causing the common voltage output being supplied to the common electrode of the pixel to change to a floating value to prevent a kickback voltage from affecting the data signal stored in the pixel.