Liquid Crystal Common Voltage Compensation Circuit
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Solution Overview
Problem
Existing common voltage compensating circuits for liquid crystal display devices do not accurately reflect the state of the liquid crystal panel, leading to incomplete compensation and reduced display quality, particularly due to kickback voltage and capacitance coupling issues, which require manual adjustment and limit the improvement in display quality.
Innovation Solution
A common voltage compensating circuit that includes a voltage distributing unit, a deviation sensing unit, and a compensating unit, utilizing a dummy common line or dummy gate line to detect deviations in the common voltage and automatically adjust the voltage to reflect the state of the liquid crystal panel, ensuring precise compensation and improved display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a common voltage compensating circuit using feedback of common voltage applied to the liquid crystal panel is used, then display quality is improved, but the first common voltage input to the compensating unit is not a resultant value used in the liquid crystal panel, leading to incomplete compensation
Solution Approach 1:
The patent introduces a dummy common line as an intermediary element that electrically connects to the liquid crystal panel and mirrors its voltage conditions. This dummy line serves as a mediator between the compensating circuit and the panel, allowing the circuit to measure the actual resultant common voltage (including kickback voltage effects) without directly interfering with the panel operation. The voltage detected through this intermediary provides accurate feedback for compensation.
Solution Approach 2:
The patent creates a copy of the liquid crystal panel's electrical characteristics by using the dummy common line to replicate the panel's voltage conditions. The dummy line copies the kickback voltage and other electrical effects present in the actual panel, enabling the compensating circuit to measure and compensate based on an accurate replica rather than an imperfect direct measurement.
2Adaptability or versatility
If the state of the liquid crystal panel changes during operation, then adaptation to new conditions is needed, but manual amendment of the first common voltage is required
Solution Approach 1:
The patent implements a continuous feedback mechanism where the common voltage compensating circuit constantly monitors the common voltage through the dummy common line and automatically adjusts the compensation voltage in response to any changes in the liquid crystal panel state. This closed-loop feedback system eliminates the need for manual intervention, as the circuit autonomously adapts to kickback voltage changes, temperature variations, and other panel state changes during operation.
Solution Approach 2:
The compensating circuit performs self-adjustment by automatically detecting voltage deviations through the dummy common line and generating appropriate compensation signals without requiring external manual intervention. The system serves itself by continuously monitoring and correcting its own operating conditions, adapting to panel state changes autonomously.
3Reliability
If kickback voltage is generated due to parasitic capacitance in the TFT, then pixel voltage deviates from required value, but existing compensating circuits cannot accurately compensate
Solution Approach 1:
The dummy common line acts as an intermediary that captures and transmits the kickback voltage generated by the TFT's parasitic capacitance to the compensating circuit. By connecting to the common electrode structure, the dummy line mediates the transmission of kickback effects from the pixel level to the common voltage control level, enabling accurate detection and compensation of these voltage deviations.
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 compensates for common voltage deviations in real-time, enhancing display quality by automatically adjusting to changes in the liquid crystal panel state, thereby improving image fidelity and reducing manual intervention.
Implementation Method 1
an electric field is generated that changes the orientation of liquid crystal molecules of the liquid crystal layer due to optical anisotropy within the liquid crystal layer. Consequently, light transmittance characteristics of the liquid crystal layer is modulated
Implementation Method 2
a kickback voltage is generated due to a parasitic capacitance in the TFT. Accordingly, the pixel voltage deviates from the required value by the kickback voltage
Implementation Method 3
when a data signal is changed from a first value corresponding to a black image to a second value corresponding to a white image, the common voltage deviates by a capacitance coupling due to the great difference between the first and second values of a data signal
Data Source
AI summary
A common voltage compensating circuit for a liquid crystal display device includes: a voltage distributing unit outputting a reference voltage; a deviation sensing unit detecting a deviation of a common voltage in a liquid crystal panel and outputting a deviation signal corresponding to the deviation of the common voltage; and a first compensating unit compensating the common voltage and outputting a first compensated common voltage by using the reference voltage, the deviation signal and an output thereof.