Coil-Capacitor Isolation Circuit for Common-Mode Noise Suppression
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Solution Overview
Problem
Existing isolation devices face challenges in enhancing common-mode transient suppression capability while minimizing circuit complexity and power consumption.
Innovation Solution
The isolation device employs equal-sized series-connected coils and a flat capacitor structure to sense differential signals, utilizing noise and magnetic field sensing circuits to determine the common-mode noise level, allowing the device to suppress transient interference without affecting the output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If circuit approaches (signal filtering, interference filtering, or interference detection and compensation) are used to improve CMTI, then common-mode interference suppression capability is enhanced, but circuit area increases and power consumption increases
Solution Approach 1:
The patent combines magnetic field sensing and noise sensing circuits into a unified isolation device architecture. The magnetic field sensing circuit detects differential signals through coils, while the noise sensing circuit detects common-mode interference through capacitor voltage changes. Both sensing functions are integrated into the same device structure, allowing simultaneous signal transmission and interference detection without requiring separate independent circuits, thus improving CMTI while controlling circuit area.
Solution Approach 2:
The patent introduces an intermediary processing mechanism where the noise sensing circuit detects common-mode interference and generates a control signal that mediates the output. When common-mode interference exceeds a threshold, the control signal blocks the output to prevent interference propagation. This intermediary approach enables effective interference suppression without requiring complex real-time filtering circuits, maintaining relatively simple circuit architecture while achieving high CMTI.
2Reliability
If encoding methods (pulse encoding, Frequency-shift keying, or On-off keying) are used to improve CMTI, then signal anti-interference capability is enhanced, but the width of pulse signals that can be transmitted is limited
Solution Approach 1:
The patent replaces encoding-based signal processing with a direct magnetic field sensing approach. Instead of modifying the signal through encoding schemes that limit pulse width, the system uses coils to directly sense the magnetic field generated by differential signals. This substitution of the sensing mechanism allows the transmission of various signal formats including wide pulse signals without the constraints imposed by encoding methods, while still achieving high anti-interference capability through differential signaling and common-mode rejection.
3Reliability
If response speed of detection and compensation is increased, then common-mode interference suppression is improved, but power consumption increases
Solution Approach 1:
The patent employs a threshold-based periodic sampling approach where the noise sensing circuit continuously monitors capacitor voltage changes but only activates the output blocking function when common-mode interference exceeds a predetermined threshold. This periodic/threshold-based action allows the system to maintain low power consumption during normal operation while achieving rapid response when interference occurs, avoiding the need for continuous high-power active suppression circuits.
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 suppresses common-mode noise, maintaining signal integrity by discarding or maintaining the output signal based on noise thresholds, thus enhancing common-mode transient immunity with simpler circuit designs.
Implementation Method 1
a plurality of coils generating magnetic fields responsive to the received differential signal
Implementation Method 2
a first metal layer of the metal layers is located at a junction of the coils, and a second metal layer of the metal layers is positioned below the first metal layer, the first and the second metal layers forming a capacitor to sense a total voltage change of the differential signal
Data Source
AI summary
An isolation circuit comprises: a plurality of coils generating magnetic fields in response to a received differential signal; a plurality of metal layers, with a first metal layer and a second metal layer forming a capacitor to sense a voltage change of the differential signal; a noise sensing circuit sensing a capacitor current generated by the second metal layer and converting into a first electrical signal; and a magnetic field sensing circuit sensing the magnetic fields generated by the coils and converting into a second electrical signal.