Active-Matrix OLED Driving Circuit Transistor Aging Compensation
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Solution Overview
Problem
The quality of OLED-based matrix displays is affected by the aging properties of drive transistors and temperature, making it challenging to maintain image quality and achieve desired luminance levels, especially in AMOLED displays used in small electronic devices.
Innovation Solution
A system that differentiates between high and low ranges of raw grayscale image data, converting low-range data to higher grayscale values and driving pixels with corresponding currents for shorter time periods, while using a gamma correction curve to adjust these values, allowing for higher luminance compensation without exceeding image data parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If higher programming voltage is applied to compensate for transistor aging and maintain image quality, then luminance level is improved, but power consumption increases and image data parameters are exceeded
Solution Approach 1:
The patent applies periodic action by dividing the frame period into multiple sub-frame periods and applying programming voltages at different times within these periods. Pixels are programmed during specific sub-frames rather than continuously, allowing higher voltage application for compensation while limiting total energy consumption through time-based control. This temporal segmentation enables effective compensation without sustained high power consumption.
2Reliability
If higher programming voltage is applied to compensate for transistor aging, then image quality is improved, but image data parameters are exceeded
Solution Approach 1:
The patent implements dynamics by making the programming voltage level and timing adaptive based on the grayscale value of each pixel. Different voltage levels are applied depending on whether the pixel requires low or high luminance compensation. This dynamic adjustment allows the system to optimize compensation effectiveness while keeping all programming values within the acceptable image data parameter range, avoiding the need to exceed standard data limits.
3Reliability
If compensation for transistor parameter changes is implemented, then image quality is maintained, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the pixel array into different groups based on their grayscale requirements and applying different programming strategies to each group. Pixels are segmented into those requiring low-range and high-range programming voltages, with each group processed during different sub-frame periods. This segmentation approach enables effective compensation for transistor aging while managing system complexity through organized, modular processing of different pixel subsets.
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 enhances luminance levels and maintains image quality by compensating for transistor parameter changes, achieving higher luminance during part of the frame period and reducing power consumption, thus improving display performance and efficiency.
Implementation Method 1
an organic light emitting device that emits light in response to application of a driving current
Data Source
AI summary
A system is provided for using raw grayscale image data, representing images to be displayed in successive frames, to drive a display having pixels that include a drive transistor and an organic light emitting device. The system determines whether the raw grayscale image data for each pixel falls within a high range or a low range. Raw grayscale image data that falls within the low range is converted to higher grayscale values, and the pixels are driven with currents corresponding to the higher grayscale values during time periods that are shorter than complete frame time periods. Raw grayscale image data that falls within the high range is converted to higher grayscale values, and the pixels are driven with currents corresponding to the higher grayscale values during time periods that are shorter than complete frame time periods and different from the time periods of the low range image data.