Source Driver Offset Cancel Circuit for LCD Polarity Inversion
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Solution Overview
Problem
Conventional liquid crystal display drivers face challenges in maintaining image quality due to fixed spatial cycles of offset voltage polarity inversion, which are not adaptable to varying data signal polarity inversion cycles, particularly between 1H and 2H inversion drive methods, leading to quality deterioration.
Innovation Solution
A liquid crystal display apparatus with an offset cancel control circuit that generates an offset cancel control signal based on the polarity signal, allowing the polarity of the offset voltage to be automatically and optimally controlled in sync with the data signal polarity inversion cycle, ensuring consistent image quality across different inversion drive methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the spatial cycle of offset voltage polarity inversion is fixed, then the circuit design is simple, but the image quality deteriorates when switching between 1H and 2H inversion drive methods
Solution Approach 1:
The patent makes the spatial cycle of offset voltage polarity inversion variable rather than fixed. The inversion cycle is dynamically adjusted based on the data signal polarity inversion cycle, allowing the system to adapt between 1H and 2H inversion drive methods. This is achieved by configuring the offset voltage polarity inversion to occur at spatial cycles that are multiples of the data signal polarity inversion cycle, ensuring compatibility with different drive methods while maintaining simple circuit design.
2Ease of operation
If the offset voltage polarity inversion cycle does not match the data signal polarity inversion cycle, then the circuit operation is simple, but uniform supply of four types of data signals is compromised
Solution Approach 1:
The patent changes the parameter of offset voltage polarity inversion cycle to be synchronized with the data signal polarity inversion cycle. By setting the offset voltage inversion spatial cycle as a multiple of the data signal inversion cycle, the system ensures that four types of data signals (positive/negative polarity combinations) are uniformly supplied to adjacent pixels. This parameter synchronization maintains simple circuit operation while achieving uniform signal distribution.
3Device complexity
If the polarity of offset voltage is not inverted at appropriate cycles, then the amplifier operation is simple, but display image quality deteriorates due to offset voltage accumulation
Solution Approach 1:
The patent implements periodic inversion of the offset voltage polarity at appropriate spatial cycles. The offset voltage is inverted at regular intervals that are synchronized with the data signal polarity inversion pattern. This periodic action prevents offset voltage accumulation and maintains display image quality while keeping the amplifier operation relatively simple through automated periodic control.
Data Source
AI summary
A liquid crystal display apparatus includes a liquid crystal display panel having a data line and a source driver for supplying a data signal to the data line based on a polarity signal. A polarity of the data signal is determined based on the polarity signal. The source driver includes an offset cancel control circuit for generating an offset cancel control signal and an output amplifier used to generate the data signal. The output amplifier is constructed so as to invert a polarity of an offset voltage based on the offset cancel control signal. The offset cancel control signal is generated based on the polarity signal.