LCD Control Board Compensation Unit Eliminates Power-Off Residual Images
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Solution Overview
Problem
Conventional liquid crystal displays (LCDs) experience power-off residual images due to rapid discharge of gate driver turn-on voltage, which prevents successful neutralization of electric charges in pixels when the LCD is powered off.
Innovation Solution
A control board with a compensation unit, using a common voltage (VCOM) to slow down the gate driver turn-on voltage (VGH), and a low voltage detection unit to ensure all scan lines are turned on, neutralizing residual charges effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the gate driver turn-on voltage (VGH) is discharged rapidly when the LCD is in power-off, then the power supply unit can quickly reset the system, but the gate driver becomes incapable of turning on all scan lines to neutralize residual charges
Solution Approach 1:
The patent applies preliminary action by providing a compensation voltage before the rapid discharge of VGH occurs. The compensation voltage is supplied to the gate driver in advance to ensure that the scan lines can be properly turned on and neutralize residual charges even when the subsequent VGH discharge is too fast to accomplish this function.
Solution Approach 2:
The compensation voltage acts as an intermediary element between the power supply unit and the gate driver. It mediates the interaction by providing the necessary voltage level to the gate driver independently of the rapid VGH discharge, enabling the gate driver to perform its function of turning on scan lines and eliminating residual charges.
2Loss of time
If the gate driver turn-on voltage (VGH) is discharged too fast, then the system response time is reduced, but the scan lines cannot be successfully turned on to eliminate power-off residual images
Solution Approach 1:
The compensation voltage is provided in advance to the gate driver before the rapid VGH discharge occurs. This preliminary action ensures that the gate driver has sufficient voltage to turn on all scan lines and eliminate residual charges, preventing power-off residual images even though the VGH discharge remains fast.
Solution Approach 2:
The patent changes the voltage parameter by introducing a compensation voltage that is superimposed on or replaces the VGH signal during the power-off period. This parameter change enables the gate driver to maintain adequate drive capability despite the fast discharge characteristics of VGH, thereby eliminating residual charges and preventing residual images.
Data Source
AI summary
A method and a control board for eliminating power-off residual images in a display and a display using the same are provided. The method includes the following steps of providing a first voltage to compensate a second voltage which is used for sequentially turning on all scan lines within a display panel when the display is in power-off, and then forming a third voltage to turn on all scan lines within the display panel according to the compensated second voltage.