OLED Data Line Voltage Sensing and Compensation Circuit
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Solution Overview
Problem
Organic light-emitting displays face issues with display quality due to differences in driving transistor characteristics across pixels, leading to imbalances in gray level expression caused by variations in processing conditions and degradation, resulting in inconsistent image representation.
Innovation Solution
The implementation of a system that includes a display panel with a scan driver, data driver, voltage analog-to-digital converter, data switch, and controller, which performs initialization and sensing periods to identify and correct voltage differences across data lines, using transistors and storage capacitors to adjust and compensate for characteristic differences in driving transistors, thereby ensuring uniform gray level representation across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If driving transistors are used in all pixels, then the display can operate with high response speed and low power consumption, but differences in transistor characteristics cause imbalances in gray level expression
Solution Approach 1:
The patent implements a sensing circuit that measures the actual voltage on data lines after they are charged by pixels, and feeds this information back to the data driver. The data driver then adjusts subsequent data voltages based on this feedback to compensate for voltage drops caused by transistor characteristic differences, thereby achieving uniform gray level expression across all pixels.
Solution Approach 2:
The patent dynamically adjusts the data voltage parameters based on measured voltage drops. By changing the data voltage compensation amount according to the sensed voltage differences, the system compensates for transistor characteristic variations and maintains consistent gray level expression across the display panel.
2Manufacturing precision
If sensing circuits are added to measure voltage differences, then gray level uniformity can be improved, but device complexity increases
Solution Approach 1:
The sensing circuit is designed to be shared across multiple pixels along each data line. Instead of providing separate sensing circuits for each pixel, the patent uses a common sensing structure that can measure voltage drops for multiple pixels sequentially, thereby reducing overall circuit complexity while still achieving gray level uniformity compensation.
Solution Approach 2:
The sensing function is merged with the existing data line structure. The data line serves dual purposes: transmitting data voltages to pixels and carrying sensing signals back to the data driver for measurement. This merging eliminates the need for completely separate sensing pathways and reduces circuit complexity.
3Manufacturing precision
If voltage sensing and compensation is performed, then luminance uniformity improves, but the time required for data processing increases
Solution Approach 1:
The patent implements sensing and compensation operations periodically, such as during vertical blanking intervals or at specific timing points within the display refresh cycle. By performing voltage sensing and compensation periodically rather than continuously, the system maintains luminance uniformity while minimizing the time impact on normal data processing operations.
Data Source
AI summary
A display includes: a display panel, scan and data drivers, an ADC, a controller, and a data switch. In a first initialization period, the data switch connects data lines to the data driver, which applies an initialization voltage thereto. In a first sensing period, the data switch connects the data lines to the ADC. The ADC receives analog sensing signals corresponding to first voltages of the data lines, and converts the analog sensing signals into digital sensing signals output to the controller. In a second initialization period, the data switch connects the data lines to the data driver, which applies the initialization voltage thereto. In a second sensing period, voltages at the data lines change to second voltages, the data switch connects the ADC to the data lines, and the ADC converts analog sensing signals corresponding to the second voltages into digital sensing signals output to the controller.