EMI Sensing Circuit Isolation for Differential-Mode Noise Cancellation
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Solution Overview
Problem
Existing electromagnetic interference suppression circuits face challenges in effectively canceling conducted differential mode electromagnetic interference signals due to the detection of interference signals from both the power source and electronic circuit, which degrades suppression performance.
Innovation Solution
A sensing circuit is designed to isolate the input and output nodes, utilizing a resonator circuit and transformer configurations to detect and suppress electromagnetic interference signals, with a regulator circuit and controlled signal source generating a suppression signal that can reduce interference by at least 90%, minimizing the influence of power source interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensing circuit is connected across the power lines to detect electromagnetic interference signals, then the suppression performance can be improved, but the sensing circuit will pick up interference signals from both the power source and the electronic circuit, degrading the suppression performance
Solution Approach 1:
The sensing circuit is segmented into two separate sensing circuits: one connected to detect interference signals from the power source, and another connected to detect interference signals from the electronic circuit. This segmentation allows independent detection and processing of each interference source, enabling selective suppression of only the electronic circuit's interference signals while ignoring power source interference.
Solution Approach 2:
A differential amplifier serves as an intermediary element that processes the signals from both sensing circuits. By configuring the differential amplifier to subtract the power source interference signal from the total interference signal, it isolates and extracts only the electronic circuit's interference component for suppression, effectively filtering out the harmful power source interference.
2Object-affected harmful factors
If a shunt capacitor is connected across the power lines to suppress differential mode electromagnetic interference signals, then the suppression of interference signals can be improved, but the sensing circuit cannot distinguish between interference signals from the power source and those from the electronic circuit
Solution Approach 1:
The single sensing circuit is divided into two separate sensing circuits with distinct connection points: one sensing circuit detects the interference signal at the power source side, while the other detects the interference signal at the electronic circuit side. This segmentation enables spatial separation of interference source detection.
Solution Approach 2:
The system implements feedback by using the detected power source interference signal to compensate for its effect in the suppression path. The differential amplifier uses the power source interference measurement to subtract its contribution from the total interference, providing accurate feedback control that targets only the electronic circuit's interference while maintaining stability against power source variations.
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 proposed solution significantly improves electromagnetic interference suppression performance by isolating the sensing circuit from power source interference, allowing for effective cancellation of differential mode electromagnetic interference signals, enhancing suppression efficiency compared to existing circuits.
Implementation Method 1
The resonator circuit may be configured with a resonance frequency arranged below a frequency of the electromagnetic interference signal (Vn) to be suppressed and above a frequency of the power source
Implementation Method 2
The sensing circuit includes a transformer connected in parallel with the resonator circuit
Data Source
AI summary
An electromagnetic interference suppression circuit and a related sensing circuit. The sensing circuit includes an input and an output operatively coupled with the input. The input is adapted to be connected on a power line and in series between a load and a shunt circuit connected across power lines between a power source and the load. The output is adapted to provide a signal (Vs) associated with an electromagnetic interference signal (Vn) generated by or at the load and arranged to be experienced by the shunt circuit. The signal (Vs) can be used for determining a suppression signal (Vn′) for reducing, or substantially eliminating, the electromagnetic interference signal (Vn). The electromagnetic interference suppression circuit includes the sensing circuit, a regulator circuit, and a controlled signal source.