Gate Discharge Control Circuit for LCD Flickering
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Solution Overview
Problem
Existing liquid crystal displays (LCDs) face issues with residual charge accumulation, leading to flickering and image blur when repeatedly turned on and off, due to the reliance on leakage currents for discharging pixel capacitors.
Innovation Solution
A gate discharge control circuit is introduced, featuring a first and second DC voltage input, voltage division circuits, and discharge switches, which control the voltage levels of gate lines to efficiently discharge pixel capacitors during shutdown and initialization, ensuring rapid voltage changes to prevent charge accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the LCD relies on leakage currents of thin-film transistors to discharge pixel capacitors, then the device structure remains simple, but residual charge accumulates causing flickering and image blur during repeated power cycles
Solution Approach 1:
The gate discharge control circuit proactively discharges pixel capacitors before the LCD is fully shut down by detecting the XOFF signal and activating discharge switches. This preliminary discharge action prevents residual charge accumulation that would otherwise cause flickering during repeated power cycles, addressing the reliability issue before it manifests.
Solution Approach 2:
The patent introduces a gate discharge control circuit as an intermediary component between the power control signal and the pixel capacitors. This circuit includes voltage division circuits, control circuits, and discharge switches that mediate the discharge process, enabling controlled charge release without requiring complex modifications to the existing LCD structure.
2Speed
If the voltage level of gate lines is pulled up immediately during shutdown using a power IC, then charge discharge speed improves, but residual charge accumulates during repeated short-time power cycles causing flickering
Solution Approach 1:
The gate discharge control circuit operates periodically based on the XOFF signal, activating discharge switches at appropriate intervals during shutdown. This periodic operation ensures that charge is discharged at the right moment without causing accumulation during repeated power cycles, resolving the flickering issue while maintaining fast discharge speed.
Solution Approach 2:
The patent uses dynamic control of discharge switches based on real-time detection of power control signals (XON/XOFF). The control circuit adjusts the discharge operation dynamically, turning discharge switches on during shutdown (XOFF) and off during operation (XON), enabling adaptive charge management that prevents flickering during repeated power cycles.
3Reliability
If the falling speed of the second DC voltage is made slower than the first DC voltage, then the discharge switch control becomes more stable, but the discharge time is extended
Solution Approach 1:
The patent employs voltage division circuits to transform the first DC voltage into a second DC voltage with a controlled, slower falling speed. This parameter change in voltage characteristics provides stable control signals for the discharge switches while the control circuit compensates for the extended discharge time by coordinating switch activation with the XOFF signal timing.
Data Source
AI summary
A liquid crystal display (LCD) and a gate discharge control circuit thereof are provided. The gate discharge control circuit has a first voltage division circuit, a control circuit, a second voltage division circuit and at least a discharge switch. A switch of the control circuit operates according to a first DC voltage so as to be turned on when the LCD is powered on and to be turned off during shutting down the LCD. The first voltage division circuit divides a second DC voltage to output a divided voltage. A falling speed of the second DC voltage is less than that of the first DC voltage. During shutting down the LCD, voltage levels of a first end and a control end of the discharge switch are pulled up because of operations of the first and second voltage division circuits, such that discharge operations of pixels of the LCD are performed.