OLED Driving Circuit Compensation for Transistor Variations
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Solution Overview
Problem
Existing organic light emitting displays face challenges in maintaining display quality due to variations in threshold voltage and mobility of driving transistors, which affect image luminance and gray scale representation.
Innovation Solution
The proposed solution involves an organic light emitting display with a scan driver, data driver, and compensation unit that extract threshold voltage and mobility information of driving transistors during specific periods, allowing for synchronization of data signals and control signals to optimize transistor operation and image display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If threshold voltage and mobility information is extracted during specific periods with synchronized scan and data signals, then display quality is improved, but device complexity increases due to multiple control periods and signal synchronization requirements
Solution Approach 1:
The frame period is divided into multiple distinct periods (first, second, third, fourth, fifth, sixth periods) with specific functions. The sensing frame is segmented into measurement periods and display periods, allowing threshold voltage extraction to occur during dedicated time slots without interfering with normal display operations. This segmentation enables precise control of when compensation occurs while maintaining overall system functionality.
Solution Approach 2:
Threshold voltage and mobility information are extracted in advance during the sensing frame before the actual display frame begins. By performing the compensation measurement during the first and third periods of the sensing frame, the system prepares correction data beforehand, which is then applied during subsequent display periods. This preliminary action ensures display quality improvement without adding complexity to the real-time display process.
2Measurement precision
If multiple control signals are supplied at different periods to extract transistor information, then measurement precision is improved, but loss of time increases due to extended sensing frame periods
Solution Approach 1:
The system operates using periodic sensing frames that are interleaved with display frames. Within each sensing frame, multiple measurement periods (first, third, fifth periods) are arranged periodically to extract threshold voltage and mobility information. This periodic structure allows the system to dedicate specific time slots to measurement while maintaining a regular rhythm between sensing and display operations, minimizing overall time loss.
Solution Approach 2:
While threshold voltage extraction occurs during the sensing frame, the system maintains continuity by immediately transitioning to the display frame where the extracted information is applied for compensation. The measurement and compensation processes are continuous and seamlessly connected, ensuring that the time spent on measurement directly translates to improved display quality in the subsequent frame without idle periods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables improved display quality by accurately extracting and compensating for transistor variations, ensuring consistent image luminance and gray scale representation, even when current is not supplied to the organic light emitting diode.
Implementation Method 1
the OLED displays images using organic light emitting diodes that emit light through recombination of electrons and holes
Data Source
AI summary
An organic light emitting display includes pixels, a scan driver configured to supply a scan signal to a specific scan line during a third period of the sensing frame, and configured to sequentially supply scan signals to the scan lines during a sixth period of the sensing frame, a data driver configured to supply, to the data lines, a previous data signal corresponding to a gray scale according to the scan signal supplied to the specific scan line during the third period, and configured to supply a current data signal to the data lines to be synchronized with the scan signals supplied during the sixth period, and a compensation unit configured to extract the threshold voltage and mobility information of the driving transistor from pixels at a specific horizontal line and coupled to the specific scan line before the scan signal is supplied during the third period.