Source Voltage Removal Detection Circuit for LCD Afterimage Control
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Solution Overview
Problem
Active matrix liquid crystal display (LCD) panels experience aesthetically undesirable 'after images' due to the slow dissipation of electronic charges when power is removed, leading to a gradual fading of the displayed image.
Innovation Solution
A circuit is developed that includes a detector circuit to identify when either of two source voltages drops to a given level, triggering a control signal to rapidly discharge capacitive elements through the source, gate, and common voltage terminals, thereby accelerating the removal of afterimages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If power is removed from the active matrix display device, then energy consumption is reduced, but after images persist due to slow charge dissipation
Solution Approach 1:
The detector circuit monitors voltage levels from voltage sources before complete power removal occurs. When voltage drops to a threshold level indicating power removal is imminent or has occurred, the circuit automatically activates discharge paths for capacitive elements, preventing afterimage formation without requiring manual intervention or continuous high energy consumption
Solution Approach 2:
The invention introduces a detector circuit and control logic as intermediary components between the voltage sources and capacitive elements. This intermediary system detects voltage drop conditions and mediates the discharge process by controlling switch elements, enabling automatic afterimage removal while managing energy consumption during power removal transitions
2Object-generated harmful factors
If a detector circuit is added to detect voltage drops and trigger discharge, then afterimage removal is improved, but device complexity increases
Solution Approach 1:
The detector circuit serves multiple functions: it monitors voltage levels from multiple voltage sources, determines when power removal has occurred, and triggers the discharge mechanism. By combining detection and control functions in a single integrated circuit block, the invention improves afterimage removal without proportionally increasing overall device complexity
Solution Approach 2:
The circuit system is designed to automatically detect voltage drop conditions and initiate capacitor discharge without external control signals. The detector circuit self-activates when voltage thresholds are met, and the discharge paths are automatically engaged, eliminating the need for additional control circuitry or manual intervention
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 removes afterimages immediately upon power removal by rapidly discharging capacitive elements, improving the aesthetic quality of active matrix LCD panels.
Implementation Method 1
a detector circuit which receives a first voltage from a first voltage source and a second voltage from a second voltage source, and which outputs a detection signal when either one of the first and second voltages drops to a given voltage level
Implementation Method 2
it takes time for the electronic charges stored in capacitive cells of active matrix type devices to dissipate when power is removed
Implementation Method 3
controlling the active matrix panel display device to accelerate the removal the afterimage from the display device
Data Source
AI summary
A control signal for removal of an afterimage from an active matrix display device is generated after the removal or disconnect of power from the device. A detector circuit receives a first voltage from a first voltage source and a second voltage from a second voltage source, and outputs a detection signal when either one of the first and second voltages drops to a given voltage level. An output circuit which receives the detection signal and outputs the control signal for removal of the afterimage from the active matrix display device.