LCD Erasing Unit for Residual Image Elimination
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Solution Overview
Problem
Liquid crystal display (LCD) devices experience image sticking and shutdown afterimages due to charge storage on pixel electrodes, which is not effectively released when the device is turned off, leading to residual charge phenomena.
Innovation Solution
An erasing unit with a charging and discharging circuit that maintains a stable high-level voltage to the TFTs during power-off, ensuring complete charge release by extending the turning-on time of TFTs and preventing rapid voltage drops at the DC power supply terminal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the LCD is turned off, then power consumption is reduced, but residual charge remains on pixel electrodes causing image sticking
Solution Approach 1:
The patent applies preliminary action by detecting the power-off state in advance and activating the discharge circuit before the LCD completely shuts down. The control circuit detects when the power supply voltage drops below a threshold and immediately responds by turning on the discharge transistors to release residual charges from pixel electrodes, preventing image sticking before it occurs.
2Reliability
If charges are stored on pixel electrodes, then image display is maintained, but image sticking occurs when LCD is turned off
Solution Approach 1:
The patent converts the harmful residual charge effect into a beneficial discharge mechanism. By detecting power-off conditions and actively controlling the discharge of charges through dedicated transistors and circuits, the system transforms the problematic charge retention into a controlled discharge process that eliminates image sticking while maintaining normal display operation.
3Speed
If voltage drops rapidly at DC power supply terminal, then power-off is achieved, but TFTs cannot be turned on for complete charge release
Solution Approach 1:
The patent uses preliminary action by detecting the power-off state through voltage threshold monitoring and immediately activating the discharge circuit before the voltage drops too low. This timing ensures that TFTs receive sufficient gate voltage to turn on and complete charge discharge from pixel electrodes, even as the power supply voltage is declining.
Solution Approach 2:
The patent introduces intermediary elements including a voltage detection circuit that monitors power supply voltage and control transistors that mediate between the power supply and pixel electrodes. These intermediaries ensure that charge discharge is activated at the appropriate moment and that TFTs receive adequate gate voltage to turn on completely, even during rapid power-off transitions.
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
The solution effectively mitigates residual charge phenomena and improves the erasing effect for image sticking by ensuring complete charge release and maintaining the operational integrity of the LCD device.
Implementation Method 1
An erasing unit with a charging and discharging circuit that maintains a stable high-level voltage to the TFTs during power-off, ensuring complete charge release by extending the turning-on time of TFTs and preventing rapid voltage drops at the DC power supply terminal
Implementation Method 2
If the charges stored in the LCD cannot be effectively released, it will result in image sticking when the LCD is turned off, i.e. an afterimage may appear
Data Source
Figure 1
Figure 2A~2B
Figure 3~4
AI summary
Embodiments of the present disclosure provide an erasing unit for image sticking in a liquid crystal display device, a control method thereof and a liquid crystal display device. A first controlling signal may be generated by dividing a voltage at a DC power supply terminal. A controlling circuit may output a second controlling signal and a third controlling signal in responding to the voltage of the first controlling signal being not greater than a reference voltage. A charging and discharging circuit may discharge under the control of the second controlling signal and output a high-level voltage signal to an outputting circuit. The outputting circuit may supply the high-level voltage signal outputted by the charging and discharging circuit to TFTs in the liquid crystal display device, controlling the TFTs to be turned on.