Gamma Op-Amp Switching to Eliminate Source Driver Offset Mura
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Solution Overview
Problem
Gamma operational amplifiers in source drivers for liquid displays exhibit inherent output voltage offsets, leading to distinct luminance or color differences and the formation of 'band mura' due to different voltage offsets in driving voltages.
Innovation Solution
A gamma operational amplifier circuit with a first and second switch circuit, and operational amplifiers, where the switch circuits are configured to ensure that positive and negative polarity signals pass through the same operational amplifier before and after data polarity inversion, respectively, eliminating voltage offsets by maintaining consistent voltage offsets across all signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate operational amplifiers are used for positive and negative polarity reference voltages, then the reference voltages can be buffered independently, but different voltage offsets occur leading to band mura
Solution Approach 1:
The patent merges the buffering paths for positive and negative polarity reference voltages by routing both through a single operational amplifier. This ensures that both polarities experience the same voltage offset, eliminating the band mura effect caused by offset differences between separate amplifiers.
Solution Approach 2:
The operational amplifier is designed to perform multiple functions: buffering positive polarity reference voltages, buffering negative polarity reference voltages, and maintaining consistent offset characteristics across both polarities. This multi-functionality resolves the contradiction by using a universal buffering component rather than separate dedicated amplifiers.
2Adaptability or versatility
If multiple operational amplifiers are used to buffer different reference voltages, then buffering capacity is increased, but device complexity increases
Solution Approach 1:
A single operational amplifier is designed to handle multiple reference voltage buffering tasks by switching between different input/output configurations. This reduces device complexity while maintaining the versatility needed to buffer both positive and negative polarity reference voltages.
Solution Approach 2:
The circuit employs dynamic switching mechanisms that allow one operational amplifier to adaptively serve multiple buffering functions. The amplifier dynamically reconfigures its connections based on whether it needs to buffer positive or negative polarity voltages, reducing the need for multiple static amplifier circuits.
3Ease of operation
If different operational amplifiers buffer positive and negative reference voltages, then independent voltage control is achieved, but voltage offset differences cause luminance or color differences
Solution Approach 1:
The patent combines the voltage control paths for positive and negative polarities under a single operational amplifier. This ensures that both voltages share the same offset characteristics, achieving uniformity while still allowing independent control through switching mechanisms that select which voltage is actively buffered.
Data Source
AI summary
A gamma operational amplifier circuit, a source driver, and a method for eliminating voltage offset are disclosed. The gamma operational amplifier circuit includes a first switch circuit, a second switch circuit, a first operational amplifier and a second operational amplifier. The source driver includes the gamma operational amplifier circuit, a resistor string and a digital-to-analog converter. The method for eliminating voltage offset includes a positive polarity control stage and a negative polarity control stage. In the method for eliminating voltage offset, the positive polarity control stage and the negative polarity control stage control the first switch circuit and the second switch circuit to change paths at which a first reference voltage and a second reference voltage pass through to enable the first reference voltage and a second reference voltage to pass different operational amplifiers in different polarity control stage.