OLED Data Driver Feedback Loop for Luminance Uniformity
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Solution Overview
Problem
Organic light emitting display devices face challenges in achieving uniform luminance due to differences in threshold voltages of transistors and deviations in electron mobility, which affect the display of images with consistent brightness.
Innovation Solution
A data driver with a ramp pulse generating part, current digital-to-analog converting part, and current control part, including comparators, is used to generate and control data signals in organic light emitting display devices. This system compares pixel currents with data currents and adjusts the data signal supply based on the comparison, ensuring that the pixel current matches the data current to maintain uniform luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional data driving methods are used, then the display device structure is simple, but luminance uniformity deteriorates due to transistor threshold voltage differences and electron mobility deviations
Solution Approach 1:
The patent implements a feedback mechanism where the pixel current is fed back to the data driver, which then compares it with the data current and adjusts the data signal accordingly. This closed-loop feedback system compensates for transistor threshold voltage differences and electron mobility deviations, achieving uniform luminance despite device variations.
Solution Approach 2:
The patent replaces conventional mechanical or simple electrical control with an electronic feedback and comparison system. By using comparators and electronic control circuits, the system achieves precise control of current flow to ensure uniform luminance output, substituting simpler control methods with more sophisticated electronic regulation.
2Manufacturing precision
If feedback control is implemented to achieve uniform luminance, then luminance uniformity improves, but device complexity and control difficulty increase
Solution Approach 1:
The feedback control mechanism compares pixel current with data current and adjusts data signal accordingly, achieving uniform luminance by compensating for transistor variations and electron mobility deviations through continuous monitoring and adjustment.
Solution Approach 2:
The patent introduces an intermediary comparison mechanism using comparators that mediate between the data current and pixel current. This intermediary system processes the comparison results and generates appropriate control signals, simplifying the overall control architecture while achieving precise luminance uniformity.
3Manufacturing precision
If data signal is continuously provided to maintain uniform luminance, then luminance uniformity is maintained, but energy consumption increases
Solution Approach 1:
The patent implements periodic action by providing data signals in controlled intervals rather than continuously. The feedback mechanism adjusts the timing and duration of data signal provision, maintaining luminance uniformity while minimizing energy consumption by avoiding unnecessary continuous signaling.
Solution Approach 2:
The feedback control system is self-regulating, automatically adjusting data signal provision based on real-time comparison of currents. When luminance uniformity is achieved, the system automatically reduces or stops data signal transmission, eliminating the need for continuous external control and reducing energy consumption.
Data Source
AI summary
An organic light emitting display device and a driving method for the same is provided. The device includes a data driver that can cause a display of an image having a uniform luminance. The data driver includes a ramp pulse generating part for generating a ramp pulse. The data driver also includes a current digital-to-analog converting part for generating a data current using data provided to the data driver. The data driver also includes a current control part for providing the ramp pulse to data lines coupled to a pixel and comparing a pixel current from the pixel with the data current to control providing of the ramp pulse to the data lines. The pixel current corresponds to the ramp pulse.