Display Device Scan Drivers for Threshold Voltage Compensation
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Solution Overview
Problem
As the resolution of display devices increases, the threshold voltage compensation time for driving transistors in organic light emitting display devices decreases due to fast data signal switching, leading to insufficient compensation operations and display defects like stains in the image.
Innovation Solution
A display device configuration that includes a first pixel and adjacent second and third pixels, with separate scan drivers and data dividers to manage scan signals and data voltages, ensuring sufficient threshold voltage compensation time by overlapping enabling periods of scan and selection signals, allowing for controlled data voltage application to each pixel type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the resolution of the display device increases and fast switching of data signal is used, then the number of lines in display panel is reduced, but the threshold voltage compensation time of driving transistor is remarkably decreased
Solution Approach 1:
The scan driving method is segmented into multiple phases: a first scan signal phase for applying data voltage to all pixels, followed by a second scan signal phase specifically for compensating threshold voltage in alternating pixels. This segmentation allows the compensation operation to be performed in a dedicated time window without extending the overall scanning period, thus maintaining high productivity while ensuring sufficient compensation time.
Solution Approach 2:
The data voltage is applied to all pixels during the first scan signal phase before the threshold voltage compensation is performed in the second scan signal phase. This preliminary action ensures that data writing is completed first, and then compensation is carried out in a subsequent dedicated period, preventing time conflict between data writing and compensation operations.
2Reliability
If the threshold voltage compensation time is increased, then sufficient compensation operation is achieved, but the data signal switching speed is reduced
Solution Approach 1:
The scan driving operates in periodic cycles where each cycle includes a first scan signal period for data writing and a second scan signal period for threshold voltage compensation in alternating pixels. This periodic structure ensures that compensation is performed regularly at appropriate intervals without continuously slowing down the data signal switching, thus maintaining both reliability and speed.
Solution Approach 2:
The scanning method dynamically adjusts the timing and target pixels for compensation based on the current scanning phase. During the first scan signal phase, all pixels receive data voltage; during the second scan signal phase, only alternating pixels undergo compensation. This dynamic approach optimizes the use of scanning time, ensuring sufficient compensation without uniformly reducing the data signal switching speed across all pixels.
3Duration of action of moving object
If separate scan drivers and data dividers are used to manage scan signals and data voltages, then sufficient compensation time is ensured, but the device complexity increases
Solution Approach 1:
The first and second scan drivers are designed with multi-functionality to perform both data writing and threshold voltage compensation operations. The same scan drivers that write data to pixels also provide the second scan signal for compensation, eliminating the need for completely separate dedicated compensation hardware. This universality ensures sufficient compensation time while minimizing the increase in device complexity.
Solution Approach 2:
The data writing function and threshold voltage compensation function are merged into a unified scanning process controlled by the scan drivers and data dividers. The first scan signal handles data writing, while the second scan signal handles compensation, both managed by the same hardware infrastructure. This merging approach ensures adequate compensation time without requiring entirely separate hardware systems, thus controlling device complexity.
Data Source
AI summary
A display device includes: a display panel including a first pixel, a second pixel adjacent to one side of the first pixel, and a third pixel adjacent to the other side of the first pixel; a first scan driver supplying a first signal to the first to third pixels through a first scan line; a second scan driver supplying a second scan signal to the second and third pixels through a second scan line when a first time elapses after the supply of the first scan signal is started; a data driver supplying a data voltage to a plurality of output lines; and a data divider selectively supplying the data voltage to data lines respectively coupled to the first to third pixels. Each of the second and third pixels includes a switching transistor controlled by the second scan signal.