IR Drop Compensation in Display Devices Using Weighted Pixel Data
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Solution Overview
Problem
Electronic display devices, particularly those using OLEDs or micro-LEDs, face inconsistencies in color and luminance due to current-resistance (IR) drops across power rails, leading to variations in gray levels and color depiction across pixels, especially as the size of power rails decreases and frame loading or image location changes.
Innovation Solution
A weighted average pixel level (APL) system models expected IR drops across the display, adjusting pixel values or gamma voltages to compensate for voltage decreases, ensuring consistent color and luminance through a voltage adjustment system that applies weight values based on pixel location and frame load, using a lookup table for real-time compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the power rail size is reduced to make the display more compact, then the display area increases and bezel becomes smaller, but the IR drop across the power rail increases causing voltage decrease and color/luminance inconsistency
Solution Approach 1:
The system performs preliminary calculation of IR drop values for different pixel locations based on power rail configuration and electrical properties before actual display operation. Compensation values are pre-computed and stored in lookup tables, enabling real-time correction without adding computational overhead during frame rendering.
Solution Approach 2:
The patent applies location-specific compensation values to different regions of the display based on their distance from power rail connections. Each pixel or pixel group receives tailored compensation based on its local electrical characteristics, with greater compensation applied to pixels farther from power connections where IR drop is more severe.
2Device complexity
If the same voltage is applied to all pixels, then the electrical input is simplified, but pixels at different locations experience different actual voltages due to IR drop causing visual artifacts
Solution Approach 1:
The system modifies the voltage parameter dynamically based on pixel location by applying compensation values from lookup tables. The base voltage signal remains simple, but location-specific offsets are added to counteract IR drop effects, transforming the uniform voltage into a spatially-varied compensation signal that eliminates visual artifacts.
3Manufacturing precision
If real-time IR drop compensation is implemented for each pixel, then color and luminance uniformity is improved, but computational complexity and processing time increase
Solution Approach 1:
The system pre-calculates IR drop compensation values for all possible pixel locations and average picture levels, storing results in lookup tables. During operation, the appropriate compensation value is retrieved through simple table lookup based on the current pixel location and APL, avoiding complex real-time calculations while maintaining high precision compensation.
Solution Approach 2:
The patent uses lookup tables that store pre-computed compensation patterns for different display conditions. These tables act as copied solutions from previous calculations, allowing the system to apply proven compensation values without re-performing complex electrical simulations for each frame.
4Reliability
If the power rail resistance is reduced to minimize IR drop, then voltage consistency is improved, but the power rail becomes larger reducing the display area
Solution Approach 1:
The patent converts the harmful IR drop effect into a useful compensation mechanism. By calculating and applying opposite-signed voltage offsets based on predicted IR drop values, the system transforms the physical limitation of resistive power rails into a correctable parameter, allowing compact power rail design without sacrificing display uniformity.
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
The solution effectively compensates for IR drops, maintaining consistent color and luminance values across the display, regardless of frame load or image location, thereby reducing visual artifacts and improving display uniformity.
Implementation Method 1
a current-resistance (IR) drop may be experienced by the pixel circuits powered by the power rails, thereby affecting the accuracy of the color and luminance depicted by the corresponding pixel
Data Source
AI summary
A display device may include rows of pixels that display image data on a display and a circuit. The circuit may receive pixel data value of image data for a pixel in a first row of the rows of pixels, determine a weight factor to apply to the pixel data value based on a position of the first row with respect to the other rows, such that each row is associated with a current-resistance (IR) drop across the display. The weight factor is determined based on a respective IR drop associated with the first row. The circuit may also generate a weighted pixel data value based on the weight factor and the pixel data value and send the weighted pixel data value to a display driver circuit that renders the image data via the display.