Scan Driver Timing for OLED Afterimage Prevention
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Solution Overview
Problem
Organic light emitting display devices face issues with undesirable instantaneous afterimages due to changes in the characteristic curve of driving transistors, leading to inconsistent image luminance and display quality.
Innovation Solution
The proposed solution involves an organic light emitting display device with a scan driver that supplies scan signals to second scan lines earlier than first scan lines by at least two horizontal periods, initializing the gate electrode of the driving transistor to a lower initialization power source voltage, and then storing the data signal voltage, ensuring the transistor is set to an on-bias state for a sufficient duration to stabilize the characteristic curve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the scan driver supplies scan signals to first scan lines and second scan lines at the same timing, then the device complexity is reduced, but the driving transistor characteristic curve changes cause undesirable instantaneous afterimages and inconsistent luminance
Solution Approach 1:
The scan driver supplies scan signals to second scan lines earlier than to first scan lines by at least two horizontal periods. This preliminary action initializes the gate electrode of the driving transistor to the voltage of an initialization power source before the data signal is supplied, ensuring the transistor is in a consistent on-bias state and preventing characteristic curve changes that would cause afterimages
Solution Approach 2:
The patent divides the scan lines into two separate groups: first scan lines and second scan lines. These groups are driven at different timings by the scan driver, allowing independent control of initialization and data signal supply timing to each group, thereby resolving the afterimage issue without requiring complete redesign of the scan driver architecture
2Stability of the object's composition
If the gate electrode is initialized to a lower voltage earlier, then the transistor characteristic curve is stabilized and afterimages are prevented, but the horizontal period timing requirements become more stringent
Solution Approach 1:
The initialization of the gate electrode to the lower voltage of the initialization power source is performed at least two horizontal periods before the data signal is supplied to the pixel. This ensures sufficient time for the transistor characteristic curve to stabilize and prevents instantaneous afterimages while maintaining proper timing margins
Data Source
AI summary
An organic light emitting display device includes a pixel, a data line, a first scan line, a second scan line, and a scan driver. The pixel includes a first transistor, a second transistor, and a third transistor. A source of the first transistor is electrically connected to a drain of the third transistor. A source of the second transistor is configured to receive an initialization voltage. The data line is electrically connected to a source of the third transistor and may transmit a data voltage higher than the initialization voltage. The first scan line is electrically connected to a gate of the third transistor. The second scan line is electrically connected to a gate of the second transistor. The scan driver may provide an initializing scan signal to the second scan line at least two horizontal periods before providing an initial scan signal to the first scan line.