Organic Light Emitting Display Pixel Power Line IR Drop
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Solution Overview
Problem
Conventional organic light emitting displays face issues with non-uniform brightness due to IR drops in pixel power lines, which become more pronounced as the display size increases, causing variations in current delivery to pixels and resulting in uneven emission brightness.
Innovation Solution
The implementation of first and second pixel power lines, each receiving voltages from separate power supplies, with adjacent pixels of the same color coupled to different power lines to minimize IR drop effects, and the use of auxiliary power lines with low resistivity materials in different layers to further reduce line resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single pixel power line supplies voltage to all pixels, then the device complexity is reduced, but the voltage uniformity deteriorates due to IR drop
Solution Approach 1:
The single pixel power line is segmented into multiple pixel power lines (first pixel power lines and second pixel power lines) that extend in opposite directions. Each segment is supplied by a separate power supply, dividing the original power delivery path into smaller segments with reduced IR drop, thereby improving voltage uniformity across the display.
Solution Approach 2:
The pixel power lines are arranged in opposite directions (first pixel power lines extending one way, second pixel power lines extending the opposite way), adding a directional dimension to the power distribution. This bidirectional arrangement ensures that pixels at opposite edges of the display are equidistant from their respective power supplies, balancing the voltage distribution.
2Area of stationary object
If pixels are positioned farther from the power supply, then the display area is increased, but the voltage delivery deteriorates due to increased IR drop
Solution Approach 1:
The display area is segmented into regions served by different pixel power lines extending in opposite directions. This allows pixels at the far edges of the enlarged display to be connected via shorter power line segments to dedicated power supplies, maintaining voltage stability despite the increased overall display area.
Solution Approach 2:
By introducing bidirectional pixel power lines extending from opposite sides, the patent creates a multi-dimensional power distribution network. This allows pixels at any position in the expanded display area to access power through the optimal path, minimizing the maximum distance any pixel must be from a power supply.
3Area of stationary object
If pixel power lines are made thinner to reduce area, then the area is reduced, but the line resistance increases causing greater IR drop
Solution Approach 1:
The total power delivery function is segmented across multiple pixel power lines rather than relying on a single thick line. Each thinner line carries less current over shorter distances, and the combined effect of multiple lines provides sufficient total power delivery while maintaining lower individual line resistances and reduced IR drop.
Solution Approach 2:
The patent transitions from a unidirectional power distribution to a bidirectional network with pixel power lines extending in opposite directions. This multi-dimensional arrangement provides multiple parallel current paths, effectively reducing the total resistance and improving power delivery reliability without requiring thicker individual lines.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures uniform voltage distribution across the display, preventing non-uniform brightness issues by balancing the IR drop across the display unit, thereby maintaining consistent emission across all pixels.
Implementation Method 1
due to an IR drop (e.g., a voltage drop) generated by the pixel power lines
Implementation Method 2
use of auxiliary power lines with low resistivity materials in different layers to further reduce line resistance
Data Source
Figure 1
Figure 2~3
Figure 4A~4B
AI summary
An organic light emitting display includes an image display unit having a plurality of pixels, and first and second pixel power lines that receive pixel-driving voltages from first and second power supplies, respectively. The second pixel power lines are interleaved with the first pixel power lines. Adjacent pixels of the same colour from among the plurality of pixels provided in the image display unit are coupled to pixel power lines corresponding to different power supplies. This is to solve or mitigate the problem of non-uniform brightness of the entire image display unit due to voltage drops in the pixel power lines.