OLED Scan Signal Waveform Segmentation for Compensation Stability
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Solution Overview
Problem
High-resolution and high-frame-rate OLED displays face challenges in ensuring stable luminance and color due to insufficient scan duration for compensation procedures, which can be exacerbated by the need for shorter scan and compensation durations.
Innovation Solution
Implementing a method where scan signals with a compensation duration longer than the scan duration are used, allowing for charging of pixel circuits during the compensation phase and data signal writing during the scan phase, with waveforms featuring alternating voltage levels to optimize the timing for both processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the scan duration is reduced to achieve high resolution and high frame rate, then the display refresh rate and resolution are improved, but the compensation procedure cannot be completed sufficiently
Solution Approach 1:
The scan signal is divided into two distinct time segments: a compensation duration segment where the scan signal alternates between first and second voltage levels to enable compensation charging, and a scan duration segment where the scan signal maintains the first voltage level for data writing. This segmentation allows both compensation and data writing to occur within the same scan period without interference.
Solution Approach 2:
During the compensation duration, the scan signal employs periodic alternating voltage levels (first voltage level and second voltage level) with a period that is a fraction of the scan duration. This periodic action enables multiple compensation charging cycles within the compensation duration, ensuring sufficient compensation time even at high frame rates.
2Reliability
If the compensation duration is extended to ensure stable compensation charging, then the compensation stability is improved, but the scan duration must be increased which reduces frame rate
Solution Approach 1:
The patent merges the compensation process and data writing process into the same scan period. The compensation duration and scan duration are both contained within one scan signal cycle, allowing compensation charging to occur during the alternating voltage period while data writing occurs during the constant voltage period. This merging eliminates the need to extend scan duration for compensation.
Solution Approach 2:
The compensation charging is performed preliminarily during the compensation duration segment before the data writing segment. By completing the compensation charging in advance during the alternating voltage period, the system ensures that the pixel circuit is ready for data writing without delaying the overall scan process, thus maintaining high frame rate.
3Ease of manufacture
If the scan signal uses constant voltage level during scan duration, then data writing is simplified, but compensation charging cannot be effectively performed
Solution Approach 1:
The scan signal transitions from a static constant voltage level to a dynamic alternating voltage level during the compensation duration. The voltage switches between first and second voltage levels with a period that is a fraction of the scan duration, creating dynamic conditions that enable effective compensation charging while maintaining simplicity during the subsequent data writing phase.
Data Source
AI summary
In one aspect of the invention, a method of driving an OLED display includes providing scan signals and data signals and applying the scan signals to scan lines and the data signals to the data lines, respectively. Each scan signal is characterized with a waveform having a compensation duration and a scan duration immediately following the compensation duration. The waveform has a first voltage and a second voltage periodically and alternately varied from one another defining a period in the compensation duration, and has the first voltage in the scan duration. The period is equal to the scan duration but shorter than the compensation duration. As such, during the compensation duration of a scan signal, pixels of a corresponding pixel row are charged for compensation, and during the scan duration, the data signals are written into the pixels of the corresponding pixel row for driving the OLEDs thereof.