Display Driver Chopping Control for Offset-Induced Flicker
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Solution Overview
Problem
High-resolution display driver ICs face challenges in maintaining uniformity among source amplifiers due to input offsets, leading to display flaws like flickering and vertical waves, especially when multiple ICs are cascaded to drive a single panel.
Innovation Solution
A system and method that analyzes image data to determine a chopping pattern for source amplifiers, dividing them into groups to apply a single chopping control signal, and optionally applies a fixed gamma chopping pattern to gamma amplifiers, adapting to image characteristics to minimize flickering and vertical waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If device sizes and static bias current are increased to reduce input offset, then amplifier uniformity is improved, but the number of source amplifiers that can be integrated is reduced
Solution Approach 1:
The patent changes the operational parameters of the amplifiers by implementing chopping technique, which periodically switches the amplifier configuration between two states. This allows the use of smaller devices with lower bias current while maintaining uniformity through dynamic parameter adjustment rather than static design optimization.
Solution Approach 2:
The patent applies periodic chopping signals to alternately switch amplifier configurations, creating a time-averaged effect that cancels input offset. This periodic action enables smaller amplifier devices to achieve the same uniformity performance as larger devices would provide in static configuration.
2Productivity
If multiple display driver ICs are cascaded to drive high resolution panels, then the number of source amplifiers is increased, but display uniformity deteriorates due to offset variation among ICs
Solution Approach 1:
The patent applies chopping technique to gamma amplifiers in cascaded driver ICs, dynamically changing their operational parameters to cancel input offsets. This allows multiple ICs to be cascaded while maintaining uniformity across all source amplifiers by compensating for offset variations through periodic parameter switching.
Solution Approach 2:
The chopping circuit acts as an intermediary mechanism between the gamma amplifiers and source amplifiers, mediating the offset variations that arise from cascading multiple ICs. By introducing this intermediate chopping stage, the system can accommodate multiple ICs while maintaining overall display uniformity.
3Manufacturing precision
If conventional chopping pattern with column inversion is used, then offset cancellation is achieved, but flickering occurs for killer pattern images
Solution Approach 1:
The patent introduces dynamic adaptability to the chopping pattern by analyzing image characteristics and selecting appropriate chopping modes. Instead of using a fixed chopping pattern, the system dynamically adjusts the chopping configuration based on the displayed image content, preventing flickering for killer pattern images while maintaining offset cancellation for other images.
Solution Approach 2:
The patent implements a feedback mechanism where the displayed image is analyzed to detect killer pattern characteristics, and this information feeds back to adjust the chopping pattern selection. This closed-loop control allows the system to adapt the chopping strategy in real-time, eliminating flickering while preserving offset cancellation benefits.
Data Source
AI summary
A system for offset cancellation for driving a display panel includes: a plurality of source amplifiers driving the display panel; an image analyzer configured to receive a data input of an image frame and analyze the data input; and a chopping pattern controller connected with the image analyzer and configured to determine a chopping pattern that fits the data input based on analysis results of the image analyzer, and apply the determined chopping pattern to the source amplifiers. The source amplifiers are divided into N groups while the chopping pattern controller is configured to drive source amplifiers in each group by a single chopping control signal. The image analyzer is configured to generate an indicator that indicates whether image data being analyzed corresponds to a general image or one of pre-registered killer pattern images. A method for offset cancellation for driving a display panel is also provided.