LCD Source Driver Bias Circuit for Uniform Output Slew Rates
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Solution Overview
Problem
As active matrix LCDs increase in size, the number of data lines driven by the source driver also increases, leading to non-uniform slew rates in output buffers, which can degrade image quality if not properly controlled.
Innovation Solution
A source driver with a bias circuit that adjusts the bias voltage by varying the resistance of a fusing resistor part using fuses, allowing for precise control of slew rates through the bias current and capacitance, ensuring the slew rate falls within a predetermined range to maintain image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the number of data lines is increased to support larger LCD panels, then the display area is improved, but the uniformity of slew rate across output buffers deteriorates
Solution Approach 1:
The patent applies local quality by providing different bias voltages to different output buffers based on their specific position and characteristics. The bias circuit generates multiple bias voltages with different voltage levels, and each output buffer receives a tailored bias voltage to compensate for variations caused by large panel sizes, thereby achieving uniform slew rates across all output buffers despite the increased display area.
2Speed
If the slew rate is increased to improve response speed, then the response time is improved, but the image quality deteriorates due to excessive slew rate variation
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the bias voltage parameter for each output buffer to achieve optimal slew rate performance. By changing the bias voltage parameter, the slew rate of each output buffer is precisely controlled to fall within a predetermined range, ensuring both fast response speed and high image quality without excessive variation.
3Manufacturing precision
If the bias voltage is adjusted to control slew rate, then the slew rate uniformity is improved, but the circuit complexity increases
Solution Approach 1:
The patent applies universality by designing a bias circuit that serves multiple functions: it generates multiple bias voltages, selects appropriate bias voltages for different output buffers, and controls slew rates for all output buffers through a unified structure. This multi-functional bias circuit achieves slew rate uniformity across all output buffers while minimizing circuit complexity through efficient resource sharing and integration.
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 ensures that the slew rates of output buffers are consistently within a stable range, preventing image quality degradation in active matrix LCDs, even as panel sizes grow.
Implementation Method 1
The bias voltage is controlled by a resistance of the fusing resistor part. The resistance of the fusing resistor part is adjusted by cutting the at least one fuse by using a laser or an overcurrent supply.
Implementation Method 2
a capacitor for stabilizing a frequency characteristic of the data line driving signal
Implementation Method 3
The resistance of the fusing resistor part is adjusted by cutting the at least one fuse by using a laser or an overcurrent supply.
Data Source
AI summary
A source driver for controlling a slew rate of a liquid crystal display (LCD) and a method for controlling the slew rate is provided. The source driver includes a plurality of output buffers for driving data lines, and a bias circuit for varying a bias voltage inputted to the output buffers to control a slew rate of the output buffers.