Display Column Driver Gamma Amplifiers Using Auto-Zeroing and Chopping
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Solution Overview
Problem
Designing gamma amplifiers in column driver integrated circuits for displays is challenging due to offset voltages and process variations, leading to noticeable artifacts on the display.
Innovation Solution
Implement a hybrid auto-zeroing and chopping scheme using redundant gamma amplifiers to alternately drive gamma references, combining spatial and temporal polarity changes to cancel out offset voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If gamma amplifiers are used to generate reference voltages for driving data signals, then the display can be driven with proper gamma correction, but offset voltages and process variations cause noticeable artifacts on the display
Solution Approach 1:
The display panel is divided into multiple rows, and different gamma amplifiers are assigned to different row groups. This segmentation allows offset cancellation to be applied independently to each row group, reducing the impact of process variations and offset voltages on the overall display quality.
Solution Approach 2:
The gamma amplifiers alternate between driving odd rows and even rows in a periodic manner. During one period, the first gamma amplifier drives odd rows while the second drives even rows; in the next period, their roles are swapped. This periodic switching enables offset cancellation by ensuring each amplifier drives both odd and even rows over time, averaging out the offset effects.
2Object-affected harmful factors
If redundant gamma amplifiers are used with auto-zeroing and chopping schemes, then offset voltages are canceled and display quality improves, but the device complexity increases
Solution Approach 1:
Each gamma amplifier is designed to be multi-functional, capable of driving both odd and even rows depending on the time period. This universality allows the system to use fewer gamma amplifiers than the total number of rows, reducing hardware complexity while still achieving offset cancellation through the periodic switching between different row assignments.
Solution Approach 2:
The system pre-establishes multiple gamma amplifier configurations and row assignment patterns before operation. The controller is pre-programmed with the switching schedule that determines which amplifier drives which row group at different time periods. This preliminary setup simplifies the real-time operation by eliminating the need for complex dynamic decision-making during display driving.
Data Source
AI summary
An electronic device may include a display having an array of pixels that receive data signals from multiple column driver integrated circuits. Each column driver integrated circuit may include gamma amplifiers that are used to set gamma references for driving the data signals. Each gamma reference can be set using first and second (redundant) gamma amplifiers in an alternating fashion to perform auto-zeroing. The auto-zeroing operation can be combined with a chopping operation to minimize amplifier offset across the different column driver integrated circuits. The auto-zeroing and/or the chopping function can be spatially alternated across the different rows in the array and temporally alternated across the different display frames.