Display Pixel Compensation with Color-Specific Sensing Voltages
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Solution Overview
Problem
Display devices face challenges due to process variations and degradation of pixels, leading to inconsistencies in transistor and light-emitting diode characteristics across different locations, which affect image quality and longevity.
Innovation Solution
A display device design that includes a sensing mechanism to compensate for pixel variations by using separate reference voltages for different colors, integrating a sensing circuit with the data driver, and employing a sensing controller to determine and apply appropriate reference voltages based on threshold voltage sensing and mobility sensing, thereby accounting for both process variations and degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If process variations and degradation are not compensated, then device complexity remains low, but manufacturing precision and reliability deteriorate due to inconsistencies in transistor and LED characteristics across different locations
Solution Approach 1:
The display device is divided into multiple sensing channels, with each channel dedicated to sensing specific pixels (e.g., red, green, blue sub-pixels). This segmentation allows for location-specific compensation of process variations and degradation, improving manufacturing precision by addressing inconsistencies in different pixel regions independently.
Solution Approach 2:
The sensing operation is performed before the display operation in each frame period. By sensing transistor threshold voltages and LED characteristics in advance, the system prepares compensation data that is then applied during display, preventing image quality degradation due to process variations and aging effects.
2Measurement precision
If sensing operation is performed frequently to improve measurement precision of pixel characteristics, then reliability improves, but productivity decreases due to time consumption in sensing multiple pixels
Solution Approach 1:
The pixel array is divided into multiple groups, with each group sensed by a dedicated sensing channel. This allows parallel sensing operations across different pixel groups within the same frame period, achieving comprehensive measurement precision without sacrificing productivity, as multiple pixels are sensed simultaneously rather than sequentially.
Solution Approach 2:
The sensing and display operations are performed in periodic cycles within each frame period. The sensing operation occupies a specific time window, followed by display operation, creating a rhythmic pattern that ensures adequate sensing precision while maintaining high productivity through efficient time utilization.
3Manufacturing precision
If separate reference voltages are used for different colors to compensate for variations, then manufacturing precision improves, but device complexity increases due to multiple reference voltage lines
Solution Approach 1:
Different reference voltages are applied to different color sub-pixels (red, green, blue) based on their specific characteristics and degradation patterns. This local quality approach allows each color channel to be compensated according to its unique process variations, improving manufacturing precision without requiring a completely separate voltage system for each pixel.
Solution Approach 2:
The reference voltage lines are designed to serve multiple functions: they provide bias voltages for sensing operations and reference levels for display operations. This multi-functionality reduces the overall number of voltage lines needed, mitigating the increase in device complexity while still enabling color-specific compensation.
4Ease of manufacture
If sensing circuits are integrated with data drivers to reduce device complexity, then ease of manufacture improves, but measurement precision may deteriorate due to shared circuit resources
Solution Approach 1:
The data driver is divided into multiple independent sensing channels, with each channel containing dedicated sensing circuits for specific pixel groups. This segmentation maintains measurement precision by providing dedicated sensing resources while achieving ease of manufacture through integration, as the sensing and display functions share the same physical substrate and control logic.
Solution Approach 2:
The sensing circuits and display driver circuits are merged into a single integrated data driver unit. This combining reduces device complexity and improves ease of manufacture by eliminating separate packaging and interconnections, while the internal segmentation of sensing channels preserves measurement precision through dedicated circuit paths.
Data Source
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AI summary
A display device includes data lines, sensing lines, first pixels emitting light in a first color, second pixels emitting light in a second other color, a data driver, a sensing circuit, and a timing controller (11). The data driver supplies data voltages to the data lines during a display period, first reference voltages (Vref1r) to the data lines coupled to the first pixels during a sensing period, and second other reference voltages (Vref1g) to the data lines coupled to the second pixels during the sensing period. The sensing circuit receives first sensing voltages from the sensing lines coupled to the first pixels and second sensing voltages from the sensing lines coupled to the second pixels, during the sensing period. The timing controller compensates image data based on the first and second sensing voltages and the data driver generates the data voltages based on the compensated image data.