Compensating Voltage Drop in Active Matrix OLED Power Lines
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Solution Overview
Problem
In active organic EL display devices, voltage drops across power supply lines due to resistance components lead to non-uniform display brightness, particularly when displaying white images on a grey background, causing darker edges and conspicuous boundaries, as current flowing through these lines affects the source voltage of each pixel.
Innovation Solution
A display device with power supply lines arranged in a matrix form, where each horizontal power supply line is connected to vertical power supply lines at both ends, and correction data is calculated to account for voltage drops, allowing for input pixel data correction to compensate for the influence of resistance on pixel current, ensuring uniform brightness across the display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power supply lines are used to supply voltage to each pixel, then power supply is provided to all pixels, but voltage drop occurs due to resistance causing non-uniform brightness
Solution Approach 1:
The patent calculates voltage drop values in advance for each pixel based on its position and the resistance characteristics of power supply lines. Correction data is prepared beforehand and stored in memory, so that when display data is written to pixels, the appropriate correction value is already available to compensate for the voltage drop, ensuring uniform brightness without requiring real-time calculation during display operation.
Solution Approach 2:
The patent modifies the display data parameters by adding correction values that compensate for voltage drop. Each pixel's input data is adjusted by a specific amount based on its position in the display panel, effectively changing the voltage parameter to counteract the resistance-induced voltage drop and achieve uniform brightness across all pixels.
2Productivity
If current flows through power supply lines to drive pixels, then pixels are activated, but voltage drop due to resistance affects source voltage and reduces display quality
Solution Approach 1:
The patent implements a feedback mechanism where voltage drop characteristics are measured or calculated based on the actual current flow through power supply lines. This feedback information is used to determine correction values that are applied to the display data, creating a closed-loop system that continuously compensates for voltage drop effects and maintains high display quality during pixel activation.
Solution Approach 2:
The patent dynamically adjusts the display data parameters by adding position-dependent correction values that compensate for voltage drop. This parameter modification ensures that pixels receiving less voltage due to resistance actually display at the intended brightness level, maintaining manufacturing precision and display quality throughout the entire display panel.
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 effectively compensates for voltage drops across power supply lines, maintaining uniform pixel current and brightness, even when displaying complex images, by calculating and applying correction data to the input pixel data, thereby enhancing display quality.
Implementation Method 1
voltage drops across power supply lines due to resistance components
Data Source
AI summary
To compensate for voltage drop on a power supply line. In a display device, pixel data is supplied to each of a plurality of pixels arranged in a matrix form and display is performed. Each pixel has a self-emissive element. A horizontal direction power supply line (horizontal direction PVDD) which supplies a power supply to each pixel is provided, and one end of the horizontal PVDD line is connected to a vertical power supply line (vertical PVDD line) that is connected to an external power supply terminal. Correction data corresponding to a voltage drop to the horizontal PVDD line due to a resistance in the vertical PVDD line is then obtained through a calculation based on pixel data, and the input pixel data is corrected using the correction data so as to reduce the influence of the voltage drop on the pixel current.