Common-Voltage Compensation Circuit for LCD Crosstalk Suppression
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Solution Overview
Problem
Liquid crystal displays experience crosstalk interference due to voltage variations caused by parasitic capacitors, leading to image brightness distortion and degraded display quality during inversion driving operations.
Innovation Solution
A common-voltage compensation circuit comprising a buffer, current/voltage converter, high-pass filter, and ripple-voltage inverter generates liquid-crystal and storage capacitor common voltages with opposite ripple voltages, compensating for voltage variations and suppressing crosstalk interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inversion driving operations are used to protect the liquid crystal layer and reduce image sticking, then the liquid crystal display reliability is improved, but crosstalk interference occurs causing image brightness distortion
Solution Approach 1:
The compensation circuit proactively generates a counter-voltage signal that opposes the crosstalk voltage before it can affect the display. The circuit detects the voltage variation caused by parasitic capacitors during inversion driving and produces an equal and opposite compensation voltage to neutralize the harmful effect, thereby maintaining image brightness uniformity while preserving the benefits of inversion driving.
Solution Approach 2:
The compensation circuit utilizes the voltage variation signal generated by parasitic capacitors during inversion driving - which is normally harmful - and converts it into a useful compensation signal. By detecting and inverting this voltage variation, the circuit transforms the harmful crosstalk effect into a beneficial counter-action that eliminates the brightness distortion while maintaining the protective inversion driving operation.
2Stability of the object's composition
If an external capacitor is installed to stabilize the common voltage, then the voltage variation is suppressed, but the device complexity increases
Solution Approach 1:
The invention extracts and compensates only the harmful AC ripple voltage component from the common voltage while preserving the necessary DC level and functional variations. By using the high-pass filter to separate and invert only the problematic voltage variation component, the circuit achieves voltage stabilization without requiring additional external capacitors, thereby reducing device complexity while maintaining common voltage stability.
Solution Approach 2:
The compensation circuit acts as an intermediary between the common voltage generator and the pixel units. It processes the common voltage signal by detecting voltage variations, inverting them, and adding the compensation signal back to the common voltage line, thereby stabilizing the voltage without requiring direct connection of large external capacitors to the common electrode.
3Ease of manufacture
If parasitic capacitors are present between data/gate lines and common electrode, then the circuit layout is simplified, but voltage variations cause crosstalk interference
Solution Approach 1:
The compensation circuit implements a feedback mechanism that continuously monitors the common voltage for variations caused by parasitic capacitors during inversion driving operations. The detected voltage variation is inverted and fed back to the common voltage line to cancel out the harmful effect, thereby maintaining image quality without requiring changes to the circuit layout that would eliminate the parasitic capacitors.
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 suppresses crosstalk interference by generating voltages with opposite phases, enhancing image display quality and eliminating the need for external capacitors, thereby reducing costs.
Implementation Method 1
The high-pass filter, electrically connected to the current/voltage converter, is employed to perform a high-pass filtering operation on the liquid-crystal capacitor common voltage for extracting a first ripple voltage
Implementation Method 2
The buffer is utilized for receiving a preliminary common voltage. The buffer drives an output current according to the preliminary common voltage
Implementation Method 3
The current/voltage converter, electrically connected to the buffer, is utilized for generating a liquid-crystal capacitor common voltage furnished to the liquid-crystal capacitor according to the output current
Implementation Method 4
The ripple-voltage inverter, electrically connected to the high-pass filter, is employed to perform an inverting operation on the first ripple voltage based on the preliminary common voltage for generating a storage capacitor common voltage having a second ripple voltage with a phase opposite to the first ripple voltage
Implementation Method 5
parasitic capacitor Cd exists between the data line DLi and the common electrode COM and, further, parasitic capacitor Cg exists between the gate line GLj and the common electrode COM
Data Source
AI summary
A common-voltage compensation circuit functions to provide a crosstalk interference suppressing mechanism for use in a liquid crystal display having a liquid-crystal capacitor and a storage capacitor. The compensation circuit includes a buffer for receiving a preliminary common voltage, a current/voltage converter, a high-pass filter and a ripple-voltage inverter. The current/voltage converter is utilized for generating a liquid-crystal capacitor common voltage furnished to the liquid-crystal capacitor according to an output current of the buffer. The high-pass filter performs a high-pass filtering operation on the liquid-crystal capacitor common voltage for extracting a ripple voltage. The ripple-voltage inverter is employed to generate a storage capacitor common voltage furnished to the storage capacitor through performing an inverting operation on the ripple voltage based on the preliminary common voltage. The ripple voltage of the storage capacitor common voltage has a phase opposite to that of the liquid-crystal capacitor common voltage for suppressing crosstalk interference.