DAC Data Driver Voltage Averaging for Uniform Gradation Speed
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Solution Overview
Problem
Current digital-to-analog converter circuits for display devices face challenges in reducing chip size and ensuring high-speed voltage changes, particularly with increased load capacitance and shorter driving periods, leading to image degradation due to uneven luminance and decreased charging percentages.
Innovation Solution
A digital-to-analog converter circuit with a reference voltage generation circuit, first and second decoders, and an amplifier circuit that generates output voltages by averaging and amplifying selection voltages, allowing for reduced reference voltages and improved change speed of output voltages across gradation levels by controlling the selection of reference voltages based on bit groups and control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of reference voltages generated in the reference voltage generation circuit is increased to increase the number of gradations (colors) of luminance level, then the display quality is improved, but the chip size (manufacturing cost) of the data driver increases
Solution Approach 1:
The patent divides the reference voltage generation into two separate circuits: a first reference voltage generation circuit that generates reference voltages in a first gradation level range, and a second reference voltage generation circuit that generates reference voltages in a second gradation level range. This segmentation allows the system to achieve a high number of gradations without requiring a single large-scale reference voltage generation circuit, thereby reducing the overall chip size while maintaining high display quality.
Solution Approach 2:
The patent introduces a new dimension by adding a range selection circuit that selects between two different reference voltage groups based on the input signal. Instead of simply increasing the number of reference voltages in a single dimension, the system now operates in two dimensions: (1) the number of reference voltages within each range, and (2) the selection between different ranges. This dimensional approach allows efficient use of chip area while providing high gradation capability.
2Measurement precision
If the number of reference voltages is increased to improve display quality, then the number of colors is increased, but the circuit complexity increases
Solution Approach 1:
The patent segments the reference voltage generation function into two independent circuits, each handling a specific gradation level range. This segmentation reduces the complexity of each individual circuit compared to a single comprehensive circuit, as each circuit only needs to generate reference voltages for a portion of the total gradation range, making the overall system more manageable and less complex.
Solution Approach 2:
The first and second reference voltage generation circuits are designed with similar structures, allowing for standardized design and implementation. Both circuits perform the same function (generating reference voltages) but for different ranges, which reduces design complexity through reuse of proven circuit architectures and simplifies manufacturing and testing processes.
3Productivity
If the driving period is shortened to increase the scanning speed, then the productivity is improved, but the charging percentage decreases leading to image degradation
Solution Approach 1:
The patent generates all necessary reference voltages in advance during the preceding data period, so that when the current data period begins, the amplifier circuit immediately has access to the required reference voltages. This preliminary generation of reference voltages eliminates delays during the active driving period, allowing the system to maintain high scanning speeds while ensuring complete charging of the data lines within the shortened driving period.
Solution Approach 2:
The patent ensures continuous availability of reference voltages by generating them in the preceding data period and maintaining them ready for use. This continuous preparation of voltage signals allows the amplifier circuit to operate without interruption during the current data period, maximizing the charging percentage within the available driving time and preventing image degradation even at high scanning speeds.
Data Source
AI summary
The present invention includes: a first decoder that outputs mutually different two voltages as first and second selection voltages based on a first bit group of a digital data signal in a first selection state, and outputs one or both of the two voltages as the first and the second selection voltages in a second selection state; a second decoder that outputs mutually different two voltages as third and fourth selection voltages based on a second bit group of the digital data signal in the first selection state and outputs one voltage based on the second bit group as the third and the fourth selection voltages in the second selection state; and an amplifier circuit that averages a combination of the first and the second selection voltages or the third and the fourth selection voltages with predetermined weighting ratios and outputs the averaged voltage.