LCD Driving Circuit Backlight Detection Rapid Afterimage Elimination
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Solution Overview
Problem
Large-sized liquid crystal displays (LCDs) experience afterimage phenomena due to increased resistance and capacitance in data and gate lines, which existing methods fail to rapidly eliminate, especially within 200 ms after the backlight source is turned off, as they rely on detecting input signal decreases and threshold voltage states for reset signals, leading to slow discharge of pixel and storage capacitance.
Innovation Solution
A driving circuit with a light sensitive element and a non-inverting amplifier connected to a PMOS transistor, which detects the backlight source's operation state and outputs a reset signal to the gate driver to turn on all gate lines when the backlight is off, ensuring rapid elimination of afterimages by controlling the PMOS transistor's ON and OFF states based on the backlight's status.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reset signal is outputted only when the input signal is detected to be decreased to a certain value, then the power supply module and the driving IC can operate in threshold state, but the pixel capacitance and the storage capacitance of the TFT-LCD can not be discharged rapidly, which fails to rapidly eliminate the afterimage
Solution Approach 1:
The patent applies preliminary action by detecting the backlight source's OFF state and outputting the reset signal before the input signal voltage naturally decays to the threshold level. This proactive timing allows capacitance discharge to begin earlier, eliminating the afterimage phenomenon within the critical 200ms window while the power supply and driving IC are still in threshold state, thus resolving the contradiction between operational stability and afterimage elimination speed
2Area of stationary object
If large-sized LCD is used, then the display size is increased, but the resistance and capacitance of data lines and gate lines increase, causing delay and afterimage phenomenon
Solution Approach 1:
The patent applies preliminary anti-action by implementing a reset mechanism that counteracts the afterimage effect caused by RC delay in large-sized displays. The light sensitive element detects when the backlight turns off and triggers a reset signal that actively discharges the pixel and storage capacitances, preventing the afterimage phenomenon that would otherwise occur due to the inherent resistance and capacitance of the enlarged data and gate lines
3Reliability
If the reset signal is outputted when the input voltage is less than a reference voltage, then the gates of the TFTs are turned on to remove afterimage, but this occurs only after 200 ms has elapsed after the backlight source is turned off
Solution Approach 1:
The patent implements preliminary action by detecting the backlight source's OFF state and immediately outputting the reset signal, rather than waiting for the input voltage to decay to the reference threshold. This timing advancement ensures that the gate capacitances are discharged during the critical 200ms period after backlight turn-off, effectively removing afterimages while maintaining power savings, thus resolving the timing contradiction
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
This solution effectively eliminates afterimages when the backlight is turned off, improving display performance by ensuring rapid discharge of capacitance and reducing the time required for image recovery, thus enhancing the overall display quality.
Implementation Method 1
a light sensitive element configured to be arranged on a liquid crystal panel of the liquid crystal display, and detect an operation state of a backlight source of the liquid crystal display
Data Source
AI summary
A driving circuit for a liquid crystal display comprises a light sensitive element configured to be arranged on a liquid crystal panel of the liquid crystal display, and detect an operation state of a backlight source of the liquid crystal display; and a reset signal output device configured to receive an input signal from the light sensitive element in accordance with the operation state of the backlight source, and output a reset signal to a gate line driver of the liquid crystal display so as to turn on all of gate lines on the liquid crystal panel.