Cascade DAC Gamma Voltage Circuit for Flat Panel Display
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Solution Overview
Problem
Existing flat panel displays face challenges in gamma correction, particularly with independent DACs generating fixed gamma reference voltages, leading to difficulties in adjusting output luminance and color coordinates, and struggles in representing low gray levels effectively.
Innovation Solution
A gamma reference voltage generation circuit with cascade-connected DACs for each color channel (R, G, B), where high potential bias voltage is connected to a high potential source and low potential bias voltage to ground, allowing for precise control of gamma reference voltages and temperature compensation to maintain display quality across varying temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If independent DACs are used to generate gamma reference voltages, then each DAC can independently control its output voltage, but all gamma reference voltages must be individually controlled to achieve desired gamma curve, making gamma correction complex
Solution Approach 1:
The patent merges the control of multiple gamma reference voltages into a single control mechanism. By connecting the high potential bias voltage input terminal of each DAC to the output terminal of the upper DAC in a cascade configuration, a single control signal can simultaneously adjust all gamma reference voltages, eliminating the need to individually control each voltage while maintaining independent voltage generation capability.
2Ease of manufacture
If gamma reference voltages are fixed by independent DACs, then voltage generation is simple, but output luminance and color coordinate correction becomes difficult
Solution Approach 1:
The patent introduces dynamic adjustability to the gamma reference voltage system. The cascade-connected DACs allow the high potential bias voltage to be dynamically changed based on temperature and luminance requirements. This enables the system to adapt to different operating conditions while maintaining simple voltage generation architecture, allowing correction of output luminance and color coordinates without complicating the voltage generation process.
3Device complexity
If standard gamma curve (1.8 to 2.2) is used, then gamma correction is straightforward, but difference between low gray levels becomes unclear
Solution Approach 1:
The patent applies local quality enhancement to the gamma correction system. By using cascade-connected DACs with controllable high potential bias voltage, the system can locally adjust the voltage distribution characteristics at different gray levels. This allows optimization of the low gray level region specifically, improving the distinguishability and precision of low gray levels while maintaining overall gamma correction effectiveness.
4Adaptability or versatility
If temperature changes occur, then display environment becomes variable, but display quality deteriorates
Solution Approach 1:
The patent incorporates temperature compensation feedback into the gamma reference voltage generation system. The high potential bias voltage input terminal of the uppermost DAC is connected to a temperature compensator that detects temperature changes and adjusts the bias voltage accordingly. This feedback mechanism maintains display quality stability across varying temperatures by dynamically compensating for temperature-induced drift in the gamma reference voltages.
Data Source
AI summary
A gamma reference voltage generation circuit and a flat panel display using the same are provided. The gamma reference voltage generation circuit includes R, G and B gamma reference voltage generators each having a plurality of digital-to-analog converters (DACs) that generate a plurality of R, G and B gamma reference voltages. In the DACs of each of the R, G and B gamma reference voltage generators, a high potential bias voltage input terminal of an uppermost DAC used to generate a gamma reference voltage of a maximum gray level is connected to a high potential voltage source. A high potential bias voltage input terminal of each of remaining DACs except the uppermost DAC is cascade-connected to an output terminal of an upper DAC next to each of the remaining DACs.