LCD Panel Drive Circuit for Pre-Shutdown Charge Bleed-Off
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Solution Overview
Problem
Liquid crystal display (LCD) panels suffer from image sticking due to residual charges in pixel capacitors after the panel is turned off, and existing charge bleed-off methods, such as XON, are inadequate in duration and require additional capacitors, which are costly and impractical for certain display products.
Innovation Solution
A panel drive circuit with a panel control circuit and display drive circuit that sequentially transmits display and charge bleed-off signals before the power supply signal drops below a threshold, allowing for advanced charge bleed-off operations like turn-off frame insertion and XON, minimizing residual charges without adding capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If additional capacitors are added to extend charge bleed-off duration, then charge bleed-off duration is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies preliminary action by performing charge bleed-off operations before the power supply signal drops below the threshold. The panel control circuit detects the power supply signal level and initiates charge bleed-off sequences (such as displaying monochrome pictures or applying specific voltages to pixel electrodes) while power is still available, ensuring charges are discharged before power loss occurs. This eliminates the need for additional capacitors to extend bleed-off duration, as the bleed-off is proactively completed during the available power window.
Solution Approach 2:
The system uses self-service by leveraging the existing power supply signal and pixel structure to perform charge bleed-off without requiring external additional components. The pixel capacitors and transistors that already exist in the display panel are utilized to conduct the bleed-off operation. The control circuit monitors the power supply signal and automatically triggers the bleed-off sequence, making the system self-sufficient without needing extra capacitors or complex external circuitry.
2Duration of action of moving object
If additional capacitors are added to extend charge bleed-off duration, then charge bleed-off duration is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies preliminary action by performing charge bleed-off operations before the power supply signal drops below the threshold. The panel control circuit detects the power supply signal level and initiates charge bleed-off sequences (such as displaying monochrome pictures or applying specific voltages to pixel electrodes) while power is still available, ensuring charges are discharged before power loss occurs. This eliminates the need for additional capacitors to extend bleed-off duration, as the bleed-off is proactively completed during the available power window.
Solution Approach 2:
The system replaces expensive additional capacitors with software-controlled display sequences that use existing panel components. Instead of adding physical hardware components (capacitors) that increase bill of materials cost, the patent uses temporary display of monochrome pictures or voltage sequences that leverage the existing pixel structure. These are essentially virtual or electrical solutions rather than physical component additions, significantly reducing manufacturing cost while achieving the same charge bleed-off duration extension.
3Reliability
If XON process is used to bleed off charges after power supply drops, then charge bleed-off is achieved, but residual charges remain causing image sticking and flicker
Solution Approach 1:
The patent applies preliminary action by performing charge bleed-off operations before the power supply signal drops below the threshold. The panel control circuit detects the power supply signal level and initiates charge bleed-off sequences (such as displaying monochrome pictures or applying specific voltages to pixel electrodes) while power is still available, ensuring charges are discharged before power loss occurs. This eliminates the need for additional capacitors to extend bleed-off duration, as the bleed-off is proactively completed during the available power window.
Solution Approach 2:
The patent applies preliminary anti-action by preemptively discharging residual charges before they can cause image sticking and flicker problems. By detecting the power supply signal level and triggering charge bleed-off sequences in advance, the system prevents the accumulation of harmful residual charges that would otherwise remain after power loss. This proactive approach counteracts the potential harmful effect (image sticking) before it occurs, ensuring cleaner charge discharge and better display reliability.
Data Source
AI summary
A display device and a panel drive circuit thereof, and a method for charge bleed-off are disclosed, relating to the field of display technologies. The panel drive circuit includes a panel control circuit and a display drive circuit. In the case that a display panel is turned off, the panel control circuit transmits at least one of a display drive signal and a charge bleed-off signal sequentially to the display drive circuit before a potential of a power supply signal drops to less than a potential threshold, such that the display drive circuit sequentially performs at least one of controlling the display panel to display a second picture that is monochrome and bleeding off charges in advance.