OLED Scan Driver Hysteresis Compensation via Multi-Period ON Voltage
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Solution Overview
Problem
Display devices, particularly OLEDs, face issues with display quality due to transient characteristics of transistors when switching between black and white grayscale, leading to display defects like text ghosting, which are not adequately addressed by existing technologies.
Innovation Solution
The implementation of a scan signal with a scan ON voltage in multiple horizontal periods, including the current and previous periods, in conjunction with a grayscale data processor that corrects current grayscale data based on previous data from the same pixel column, effectively eliminating display defects by compensating for hysteresis characteristics of transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional scan signal with ON voltage only in the current horizontal period is used, then the device complexity is low, but display defects such as text ghosting occur due to transistor hysteresis characteristics
Solution Approach 1:
The scan signal applies ON voltage in previous horizontal periods (n-2, n-4, etc.) before the current horizontal period n, preparing the transistor in advance to compensate for hysteresis effects. This preliminary action ensures the transistor is properly conditioned before the actual data writing occurs, eliminating text ghosting without requiring complex additional hardware.
2Reliability
If grayscale data correction based on previous pixel data is implemented, then display defects are eliminated, but the device complexity increases due to additional processing requirements
Solution Approach 1:
The grayscale data processor retrieves previous grayscale data from memory, compares it with current grayscale data, and generates correction values based on the difference. This feedback mechanism compensates for transistor hysteresis by adjusting current pixel values based on historical data, ensuring accurate grayscale representation without complex hardware modifications.
Solution Approach 2:
The system performs grayscale data correction in advance before the actual display output by processing current grayscale data with correction values derived from previous pixel data. This preliminary correction ensures that the final displayed grayscale values are accurate, preventing display defects before they occur.
3Illumination intensity
If scan ON voltage is applied in multiple previous horizontal periods, then luminance characteristics are improved, but energy consumption increases
Solution Approach 1:
The scan signal applies ON voltage in specific previous horizontal periods (n-2, n-4, etc.) rather than continuously, providing just enough conditioning to compensate for hysteresis effects. This partial action approach improves luminance characteristics by ensuring proper transistor conditioning while avoiding excessive energy consumption that would result from continuous ON voltage application.
Data Source
AI summary
A display device includes a scan driver configured to provide a scan signal to the scan line, the scan signal having an ON voltage for turning on a transistor in a plurality of horizontal periods including a current horizontal period and at least one previous horizontal period corresponding to the scan signal, and a grayscale data processor configured to correct current grayscale data of a current pixel corresponding to the current horizontal period to generate correction grayscale data based on previous grayscale data of a previous pixel corresponding to the previous horizontal period, the current pixel included in a same pixel column as the previous pixel.