Display Pixel Sensing via Segmented Data Line Voltage Control
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Solution Overview
Problem
Existing display devices face challenges in accurately sensing the electrical characteristics of pixels due to variations in threshold voltage and mobility of driving transistors, which can lead to inaccurate luminance and reliability issues.
Innovation Solution
A display device design that includes a scan driver, data driver, and a sensing mode where a test voltage is applied to one data line and an off voltage to another, allowing for accurate sensing of electrical characteristics by blocking leakage currents and preventing transistor deterioration through controlled voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external compensation technology is used to sense electrical characteristics of pixels, then the electrical characteristics can be sensed and compensated, but the sensing accuracy is insufficient due to leakage currents and transistor variations
Solution Approach 1:
The pixel array is divided into a sensing region and a non-sensing region. The sensing region includes pixels that are actively sensed during the sensing period, while the non-sensing region includes pixels that are turned off to prevent leakage currents. This spatial segmentation allows accurate sensing of electrical characteristics without interference from leakage currents of other pixels.
Solution Approach 2:
Before sensing the electrical characteristics of a target pixel, the other pixels in the same column are turned off in advance by applying an off voltage to their data lines. This preliminary action prevents leakage currents from non-target pixels during the sensing process, ensuring accurate measurement of the target pixel's electrical characteristics.
2Measurement precision
If a single off voltage is applied to data lines during sensing, then leakage currents are blocked, but transistor reliability deteriorates due to prolonged exposure to negative gate-source voltage
Solution Approach 1:
The sensing operation is performed in periodic sensing periods, and the reset operation is performed in periodic reset periods. During the sensing period, an off voltage is applied to block leakage currents. During the reset period, a reset voltage is applied to restore the transistor's electrical characteristics. This periodic alternation ensures both accurate sensing and transistor reliability.
Solution Approach 2:
The voltage applied to data lines is dynamically changed between two states: an off voltage during the sensing period to block leakage currents, and a reset voltage during the reset period to restore transistor characteristics. This parameter change allows the system to switch between leakage blocking and transistor recovery modes, addressing both sensing accuracy and transistor durability requirements.
3Measurement precision
If sensing is performed continuously to maintain accurate luminance, then electrical characteristics are constantly monitored, but transistor deterioration accelerates due to repeated sensing operations
Solution Approach 1:
The sensing operation is performed periodically in sensing periods, followed by reset operations in reset periods. This periodic sensing allows the system to monitor electrical characteristics at intervals rather than continuously, maintaining luminance accuracy while providing recovery time for transistors to prevent cumulative deterioration.
Solution Approach 2:
The system maintains continuous operation by alternating between sensing periods and reset periods. During sensing periods, electrical characteristics are monitored to ensure luminance accuracy. During reset periods, transistors are restored to prevent deterioration. This continuous alternation ensures both accurate luminance control and transistor reliability over time.
Data Source
AI summary
A display panel includes pixels connected to first and second data lines and a readout line. The data driver supplies data signals to the first and second data lines and supplies an initialization voltage to the readout line. Each of the pixels includes at least one light emitting element and a driving transistor. The driving transistor controls an amount of current based on a difference between a corresponding data signal among the data signals and an initialization voltage. In a sensing mode, the data driver supplies a test voltage to the first data line and a first off voltage to the second data line in a first period and supplies a second off voltage to the second data line in a second period after the first period. The second off voltage is different from the test voltage and the first off voltage.