OLED Display TFT Compensation via Dynamic Gain Adjustment
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Solution Overview
Problem
In OLED display devices, characteristic differences in driving TFTs across pixels lead to luminance deviations, display spots, reduced lifespan, and afterimages due to process deviations and degradation, making it difficult for existing compensation methods to ensure a voltage margin within the data driver's capabilities.
Innovation Solution
The OLED display device incorporates a data driver that senses the threshold voltage and mobility of each driving TFT, using a timing controller to add and multiply offset and gain values to image data, varying the gain value's weight based on image luminance to compensate for characteristic deviations, ensuring a voltage margin and improving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a compensation data voltage is calculated using the existing method, then threshold voltage and mobility compensation is achieved, but if the calculated compensation data voltage exceeds the maximum voltage that can be driven by the data driver, then it becomes difficult to compensate data
Solution Approach 1:
The patent applies dynamics by making the gain value adjustable based on data luminance levels. The timing controller dynamically changes the gain value applied to compensation data voltages: using a first gain value when data luminance exceeds a reference level, and a second gain value (lower than the first) when data luminance is at or below the reference level. This dynamic adjustment ensures that compensation voltages remain within the data driver's maximum voltage capability while effectively compensating for TFT characteristic deviations across different brightness conditions.
2Device complexity
If characteristic differences of driving TFTs are not compensated, then device complexity is reduced, but luminance deviation between pixels and display spots occur
Solution Approach 1:
The patent implements feedback by using the data driver to sense the threshold voltage and mobility of each driving TFT, then feeding this information back to the timing controller. The timing controller uses this feedback data to calculate and apply appropriate compensation values to each pixel's data voltage, thereby correcting luminance deviations and preventing display spots caused by TFT characteristic variations.
Solution Approach 2:
The patent applies parameter changes by adjusting the gain value parameter based on data luminance levels. When data luminance exceeds a reference level, a first gain value is applied; when it is at or below the reference level, a second gain value is applied. This parameter adjustment ensures that compensation remains effective across different brightness conditions while keeping compensation voltages within the data driver's operational range.
3Ease of manufacture
If driving TFT characteristic differences are not compensated, then manufacturing process is simpler, but afterimages and reduced lifespan occur due to degradation
Solution Approach 1:
The patent applies preliminary action by performing threshold voltage and mobility sensing and compensation before the OLED display panel is delivered to users. The data driver senses TFT characteristics and the timing controller applies compensation during the manufacturing or initialization phase, ensuring that the panel is optimized for uniform performance before deployment. This preliminary compensation prevents future display issues and extends panel lifespan.
Data Source
AI summary
An organic light emitting diode (OLED) display device and a method of driving the same are discussed. The method includes sensing a threshold voltage and mobility of a driving thin film transistor (TFT) included in each pixel using a sensing line connected per pixel and supplying the threshold voltage and the mobility to a timing controller in a measurement mode, by a data driver, and supplying image data input from an external source to the data driver by a timing controller, the timing controller adding and multiplying an offset value and gain value corresponding to the threshold voltage and mobility of the driving TFT, sensed by the data driver in the measurement mode, with the image data to compensate the image data, wherein the compensation of the image data includes varying a weight of the gain value according to luminance of the image data.