PVDD Power Supply Segmentation for Pixel Current Measurement Noise Reduction
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Solution Overview
Problem
In large-sized active matrix organic electroluminescence display devices, measuring pixel current is challenging due to high noise levels from leakage currents and capacitive components, which affect accuracy and speed, especially when trying to separate the PVDD line for data writing and emission, and existing methods struggle to effectively remove common-mode noise.
Innovation Solution
The implementation of a configuration with two vertical PVDD power supply lines (PVDDa and PVDDb) and switches to isolate the measurement group, allowing for differential noise cancellation by connecting PVDDa to one group and PVDDb to another, and using operational amplifiers to subtract noise currents, thereby reducing external and internal noise influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If PVDD lines are separated for data writing and emission in large panels, then voltage drop during data writing is reduced, but measurement accuracy deteriorates due to high noise levels from leakage currents and capacitive components
Solution Approach 1:
The PVDD power supply system is segmented into multiple independent groups (PVDD1, PVDD2, etc.), each serving specific functional purposes. During measurement mode, only the PVDD group connected to the measurement pixel remains active while other groups are disconnected, isolating the measurement circuit from noise generated by other pixels' leakage currents and capacitive effects.
Solution Approach 2:
The measurement pixel is extracted and isolated from the general pixel array by connecting it to a dedicated PVDD group that can be independently controlled. Switches disconnect all other pixels from their PVDD lines during measurement, removing the harmful leakage currents and capacitive noise from other pixels that would otherwise interfere with the measurement.
2Object-affected harmful factors
If all pixels remain connected to PVDD during measurement, then common-mode noise from external sources can be canceled by measuring PVDD and CV currents simultaneously, but internal noise from leakage currents of other pixels increases measurement difficulty
Solution Approach 1:
The measurement pixel is extracted and isolated from the general pixel array by connecting it to a dedicated PVDD group that can be independently controlled. Switches disconnect all other pixels from their PVDD lines during measurement, removing the harmful leakage currents and capacitive noise from other pixels that would otherwise interfere with the measurement.
Solution Approach 2:
Switches act as intermediaries to selectively connect or disconnect PVDD lines to specific pixel groups. During measurement, switches connect only the measurement pixel's PVDD line to the power source while disconnecting all other PVDD lines, thereby mediating between the need to power the measurement pixel and the need to eliminate noise from other pixels.
3Quantity of substance
If measurement is performed in large panels with many pixels, then more pixels can be covered, but noise from capacitive components and leakage currents increases, affecting speed and accuracy
Solution Approach 1:
The PVDD power supply system is segmented into multiple independent groups (PVDD1, PVDD2, etc.), each serving specific functional purposes. During measurement mode, only the PVDD group connected to the measurement pixel remains active while other groups are disconnected, isolating the measurement circuit from noise generated by other pixels' leakage currents and capacitive effects.
Solution Approach 2:
The measurement pixel is extracted and isolated from the general pixel array by connecting it to a dedicated PVDD group that can be independently controlled. Switches disconnect all other pixels from their PVDD lines during measurement, removing the harmful leakage currents and capacitive noise from other pixels that would otherwise interfere with the measurement.
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 approach significantly reduces noise interference, enhancing measurement accuracy and speed by isolating the measurement group and canceling out common-mode noise, allowing for precise pixel current determination even in large panels with many pixels.
Implementation Method 1
using operational amplifiers to subtract noise currents, thereby reducing external and internal noise influences
Data Source
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AI summary
Noise on a current to be measured is removed. Horizontal power supply lines (PVDD) are arranged in a horizontal direction and supply a current to pixels in respective corresponding horizontal lines. A switch (8) connects a group of the horizontal power supply lines (PVDD) to a first power supply line (PVDDa) or a second power supply line (PVDDb) disposed outside a pixel region in a switchable manner. Only the horizontal power supply lines (PVDD) in a group to which a pixel to be measured belongs are supplied with power from the second power supply line (PVDDb) so as to measure a current of each pixel in the group, and a current flowing into a power source (PVDDa) connected to a group to which other pixels than the pixel to be measured belong is measured, to thereby calculate a pixel current based on a difference between the two measured currents.