OLED Display Panel Dual Pixel Driving Circuit Brightness Uniformity
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Solution Overview
Problem
Existing OLED display panels face challenges in maintaining uniform brightness between bending and non-bending areas due to threshold voltage drifts, which current internal compensation methods struggle to address effectively, especially in foldable displays where the bending area requires larger voltage compensation ranges.
Innovation Solution
The implementation of a dual pixel driving circuit system, where a first pixel driving circuit compensates threshold voltage in the bending area during startup or shutdown periods and a second circuit compensates in the non-bending area during blank time frames, with extended compensation times to ensure uniform brightness across the display panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If internal compensation is used during blank time period between display frames, then the compensation time is short (about plus/minus 0.5V range), but the compensation range required for bending area is larger due to significant threshold voltage changes
Solution Approach 1:
The display panel is divided into two distinct regions: bending area and non-bending area. Each region has its own dedicated pixel driving circuit with different compensation strategies. The bending area uses a first pixel driving circuit with extended compensation time periods, while the non-bending area uses a second pixel driving circuit with standard blank time period compensation.
Solution Approach 2:
The first pixel driving circuit performs threshold voltage compensation during extended time periods before display frames are rendered (first time period before starting up or second time period after shutting down). This preliminary compensation action ensures that transistors in the bending area are pre-adjusted for threshold voltage drift before actual display operation begins.
2Device complexity
If the same pixel driving circuit is used for both bending and non-bending areas, then the device complexity is reduced, but the brightness uniformity between bending and non-bending areas deteriorates
Solution Approach 1:
Different compensation strategies are applied to different regions of the display panel. The bending area receives extended compensation time and different compensation timing compared to the non-bending area. This localized differentiation ensures that each region's specific requirements are met, achieving overall brightness uniformity across the entire display panel.
3Loss of time
If compensation is performed during blank time period only, then the compensation time is limited, but the threshold voltage drift in bending area during extended periods cannot be fully compensated
Solution Approach 1:
The first pixel driving circuit performs threshold voltage compensation during extended time periods before display frames are rendered (first time period before starting up or second time period after shutting down). This preliminary compensation action ensures that transistors in the bending area are pre-adjusted for threshold voltage drift before actual display operation begins.
Solution Approach 2:
The compensation process is performed periodically at specific time periods (before startup, after shutdown, or during blank time periods) rather than continuously. The first pixel driving circuit uses extended periodic compensation windows, while the second pixel driving circuit uses standard blank time period compensation, allowing both to effectively manage threshold voltage drift in their respective regions.
Data Source
AI summary
An organic light emitting diode (OLED) display panel and a display device are provided. A first pixel driving circuit of the is configured to compensate a threshold voltage of a drive transistor in the bending area during a first time period before starting up or a second time period after shutting down. A second pixel driving circuit is configured to compensate a threshold voltage of a drive transistor in the non-bending area during a blank time period between adjacent display frames. A duration of the first time period and a duration of the second time period are both greater than a duration of the blank time period. A brightness of the display panel is uniform.