LCD Data Driver Bias Feedback for Output Buffer Slew Rate Matching
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Solution Overview
Problem
In Liquid Crystal Display (LCD) apparatuses, slew rate differences among output buffers can lead to vertical lines at the boundary between output buffers and chips, deteriorating display quality.
Innovation Solution
A data driver with an input circuit, converter, output buffer circuit, and bias voltage control circuit that adjusts the bias voltage based on the slew rate of the analog data voltage, using a feedback path to maintain consistent slew rates across output buffers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple output buffers are used to drive data lines, then the data driver can handle higher resolution displays, but slew rate differences among the output buffers cause vertical lines at boundaries, deteriorating display quality
Solution Approach 1:
The patent implements a feedback mechanism where the bias voltage control circuit receives feedback signals from each output buffer, measures their slew rates, and adjusts bias voltages accordingly. This closed-loop feedback system dynamically compensates for slew rate differences among multiple output buffers, allowing high-resolution displays to maintain uniform display quality without visible boundary lines.
Solution Approach 2:
The patent changes the bias voltage parameter of each output buffer based on measured slew rate characteristics. By dynamically adjusting the bias voltage, the system optimizes the slew rate of each output buffer to match a target value, thereby eliminating display quality deterioration while maintaining the ability to drive high-resolution displays with multiple buffers.
2Speed
If the slew rate of output buffers is increased to improve response speed, then data transmission performance improves, but slew rate differences among buffers become more pronounced, causing more visible vertical lines
Solution Approach 1:
The patent makes the bias voltage dynamic rather than fixed. The bias voltage control circuit continuously monitors the slew rate of each output buffer and adjusts the bias voltage in real-time to maintain optimal slew rate performance. This dynamic adjustment ensures that all output buffers operate at matched speeds, preventing visible boundary lines while maintaining high data transmission performance.
Solution Approach 2:
The patent adjusts the bias voltage parameter to optimize and equalize the slew rates of all output buffers. By changing the bias voltage based on measured performance, the system achieves uniform response speeds across all buffers, eliminating the trade-off between speed and display uniformity.
3Manufacturing precision
If individual bias voltage control is implemented for each output buffer, then slew rate uniformity improves, but device complexity increases due to additional control circuits
Solution Approach 1:
The patent segments the bias voltage control function into individual control units, with each output buffer having its own bias voltage control circuit. This segmentation allows independent measurement and adjustment of each buffer's slew rate, achieving uniformity across all buffers. The modular structure manages complexity by localizing control functions to where they are needed most.
Data Source
AI summary
A display apparatus including a display driver. The data driver includes a converter to receive and convert image data in digital form into data voltages in analog form, and to provide the data voltages to output buffers. The output buffers receive and buffer the data voltages based on bias voltages generated as part of a feedback path between a bias voltage control circuit and the output buffers. The data voltages are provided to a display part. Before the data voltages output from the output buffers are provided to the display part, the bias voltage control part receives data voltage from the output buffers to count a slew rate of the data voltage, and varies the voltage level of the bias voltage based on the counted result of the slew rate, thereby providing feedback to the output buffers. Accordingly, differences of the slew rate between the data voltages output from the output buffers may be decreased.