Real-Time Driving Characteristic Sensing in OLED Pixels
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Solution Overview
Problem
Existing display devices, such as OLEDs, face challenges in performing real-time sensing of driving characteristics of pixels due to process variations and degradation over time, which affects luminance uniformity and requires non-real-time sensing operations.
Innovation Solution
A display device with a scan driver, data driver, sensing circuit, and controller that measures source voltages of driving transistors at specific time points within a frame period, calculates threshold and mobility parameters, and predicts saturated source voltages to accurately sense driving characteristics in real time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sufficient sensing time is used to saturate source voltages of driving transistors, then measurement precision of driving characteristics is improved, but productivity is worsened because sensing cannot be performed in real time
Solution Approach 1:
The patent applies preliminary action by measuring source voltages at multiple time points during the sensing period and using these preliminary measurements to calculate driving characteristics before the sensing operation is complete. The controller measures source voltages at first and second time points, calculates threshold and mobility parameters, and predicts saturated source voltages, enabling real-time sensing without requiring the full saturation time to elapse naturally.
Solution Approach 2:
The patent implements feedback by continuously monitoring source voltages at different time points and using these measurements to dynamically calculate and update driving characteristics. The controller uses the measured source voltages to compute threshold voltage parameters and mobility parameters, then feeds back these calculations to predict saturated voltages and determine final driving characteristics, enabling iterative real-time sensing.
2Productivity
If sensing operation is performed in real time during image display, then productivity is improved, but measurement precision is worsened due to insufficient sensing time
Solution Approach 1:
The patent performs preliminary measurements of source voltages at multiple time points during the sensing period, then uses these preliminary data to calculate driving characteristics before the sensing operation completes. This allows the system to obtain accurate measurements within the constrained real-time window by proactively gathering and processing data at strategic moments rather than waiting for natural saturation.
Solution Approach 2:
The patent introduces dynamics by adapting the sensing methodology to the real-time constraint environment. Instead of using a static, fixed-duration sensing period that guarantees saturation, the system dynamically measures voltages at multiple time points and uses mathematical models to extrapolate saturated values, making the sensing process adaptable to the limited time available during image display.
3Measurement precision
If multiple source voltage measurements are taken at different time points, then measurement precision of driving characteristics is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by using the same sensing circuit infrastructure to perform multiple functions: measuring source voltages at different time points, calculating threshold and mobility parameters, predicting saturated voltages, and determining final driving characteristics. This multi-functional approach allows high-precision measurement without requiring separate dedicated circuits for each measurement function, thereby limiting the increase in device complexity.
Data Source
AI summary
A display device includes a sensing circuit and a controller which selects a pixel row in a frame period. A vertical blank period of the frame period includes a sensing time in which the sensing circuit performs a sensing operation for the selected pixel row. The sensing circuit measures a first source voltage of a driving transistor of a pixel in the selected pixel row at a first time point of the sensing time, and measures a second source voltage of the driving transistor at a second time point of the sensing time. The controller calculates a threshold voltage parameter and a mobility parameter based on the first and second source voltages, predicts a saturated source voltage of the driving transistor based on the threshold voltage parameter and the mobility parameter, and calculates a threshold voltage of the driving transistor based on the saturated source voltage.