Display Device ADC Sensing Circuit Luminance Compensation
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Solution Overview
Problem
Self-luminescent display devices face luminance variations due to differences in threshold voltages and mobilities of driving transistors, which affect image uniformity, as these characteristics degrade over time.
Innovation Solution
A display device and method that utilize an analog-digital converter (ADC) for external compensation, involving a sensing circuit to extract and correct current codes based on grayscale conversion characteristics, allowing for simultaneous calculation of mobility and threshold voltage characteristics of driving transistors, thereby compensating for image data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external compensation is applied using ADC, then luminance variation is reduced, but device complexity increases due to additional sensing circuits and correction mechanisms
Solution Approach 1:
The sensing process is divided into multiple sensing periods (first sensing period for first grayscale, second sensing period for second grayscale) to separately measure different characteristics. This segmentation allows the system to collect comprehensive transistor parameter data without requiring all sensing operations to occur simultaneously, thereby managing complexity while improving luminance uniformity through comprehensive compensation.
Solution Approach 2:
The system performs sensing operations during dedicated sensing periods before the actual display period. By preliminarily measuring the driving transistor characteristics and calculating compensation values in advance, the system prepares correction data that is then applied during image display, ensuring luminance uniformity without interfering with normal display operations.
2Measurement precision
If multiple sensing periods are used to extract sensing values at different grayscales, then measurement precision improves, but loss of time increases due to extended sensing duration
Solution Approach 1:
The system uses periodic sensing operations where sensing periods are interleaved with display periods. During sensing periods, multiple grayscale measurements are taken sequentially (first sensing period for first grayscale, second sensing period for second grayscale). This periodic approach allows comprehensive measurements to be made without continuously interrupting display, balancing measurement precision with time efficiency.
Solution Approach 2:
The system performs sensing at multiple different grayscale levels (excessive action) to obtain comprehensive transistor characteristics including both mobility and threshold voltage. By measuring at more grayscale points than the minimum single point, the system achieves higher measurement precision for calculating compensation values, accepting the trade-off of extended sensing time.
3Manufacturing precision
If ADC conversion characteristic is corrected based on grayscale, then manufacturing precision improves, but ease of operation decreases due to additional correction steps
Solution Approach 1:
The system implements feedback by measuring actual transistor characteristics through sensing circuits, comparing them against ideal values, calculating compensation values based on the differences, and applying these corrections to subsequent display operations. This closed-loop feedback mechanism automatically adjusts for manufacturing variations and transistor degradation, improving compensation accuracy while the automated nature of the process minimizes manual intervention requirements.
Solution Approach 2:
The display device performs self-diagnosis and self-correction by using its own sensing circuits to measure driving transistor characteristics and automatically calculating compensation values. The system serves itself by internally managing the sensing, calculation, and compensation application processes without requiring external calibration equipment or manual adjustment, thereby improving precision while maintaining operational simplicity.
Data Source
AI summary
A display device includes pixels coupled to scan lines, control lines, data lines, and sensing lines, a scan driver for supplying a scan signal to the scan lines and supplying a control signal to the control lines, a data driver for supplying one of an image data signal and a sensing data signal to the data lines, and a sensing circuit including an analog-digital converter (“ADC”) which converts a sensing value supplied through the sensing lines into a current code in a digital form, the sensing circuit correcting the current code by reflecting a conversion characteristic of the ADC, the sensing circuit sensing characteristics of the driving transistor based on the corrected current code.