OLED Pixel Degradation Compensation via Threshold Voltage Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Organic light emitting display devices experience degradation over time, leading to variations in threshold voltages across pixels, resulting in uneven luminance and potential afterimages, with existing compensation methods limited in range and effectiveness.
Innovation Solution
A display device with a sensing unit to measure threshold voltages and a timing controller that calculates grayscale compensation values based on these measurements, using linear slope values to adjust input image data and compensate for pixel degradation, ensuring stable compensation even when threshold voltages move negatively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a data voltage is compensated from the outside corresponding to the movement of the threshold voltage, then the threshold voltage can be compensated within a limited range, but the compensation range is restricted and cannot handle continuous negative direction movement
Solution Approach 1:
The patent changes the compensation parameter from simple data voltage adjustment to a dual-parameter system involving both data voltage and emission duration. By modifying the emission duration parameter in addition to data voltage, the system expands the compensation range to handle continuous threshold voltage movement in the negative direction, thereby improving both reliability and adaptability.
2Illumination intensity
If the threshold voltage is continuously moved in the negative direction, then luminance increases, but the reliability of the display device is lowered
Solution Approach 1:
The patent implements a feedback mechanism where the sensing unit continuously measures the threshold voltage of each pixel, and the timing controller adjusts the emission duration based on these measurements. This closed-loop feedback system dynamically compensates for threshold voltage changes, preventing uncontrolled luminance increases and maintaining display reliability over time.
Solution Approach 2:
The patent performs preliminary sensing of threshold voltages during a sensing period before the actual display period. By measuring and compensating for threshold voltage variations in advance, the system prevents luminance non-uniformity and reliability issues from developing during normal operation.
3Ease of operation
If the same driving voltage is applied to the driving transistors of the respective pixels, then the driving voltage is uniform, but a difference between currents flowing through the organic light emitting diodes is caused due to threshold voltage variation
Solution Approach 1:
The patent applies local quality compensation by individually adjusting the emission duration for each pixel based on its specific threshold voltage characteristics. Instead of uniform adjustment across all pixels, the timing controller tailors the emission duration parameter to each pixel's local needs, thereby achieving current uniformity while maintaining simple driving voltage application.
Data Source
AI summary
There are provided a display device and a method of compensating for degradation thereof. The display device includes a display panel including pixels, a sensing unit configured to measure threshold voltages of the pixels, respectively, and a timing controller configured to determine grayscale compensation values with respect to the pixels corresponding to the threshold voltages, respectively, and to compensate input image data with respect to the pixels based on the grayscale compensation values, respectively, wherein the grayscale compensation values have a linear relationship with a grayscale of the input image data by using a linear slope value determined based on the threshold voltages.