Differential Transformer Digital Isolator for Common-Mode Noise Rejection
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Solution Overview
Problem
Current digital isolators face challenges in effectively eliminating common-mode interference during signal transmission, which affects the quality and reliability of isolated digital signals.
Innovation Solution
The implementation of a digital isolator design that utilizes a transformer-based isolation element with two secondary windings arranged in opposite phases, coupled with a differential circuit to generate differential signals, effectively eliminating common-mode noise and enhancing anti-interference performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional digital isolator uses a single secondary winding, then the device complexity is low, but common-mode interference cannot be effectively eliminated
Solution Approach 1:
The patent divides the secondary side of the isolation element into two separate windings (first secondary winding and second secondary winding) instead of using a single winding. Each winding generates a differential signal that is processed separately by differential circuits, enabling effective rejection of common-mode interference through differential signaling while maintaining manageable structural complexity
Solution Approach 2:
The patent transitions from a single-ended signal structure to a differential signal structure by introducing two secondary windings with opposite phase relationships. This dimensional change from one signal path to two complementary signal paths enables common-mode noise rejection while preserving signal integrity
2Reliability
If optical coupling is used for isolation, then electrical isolation is achieved, but signal transmission quality deteriorates due to limited bandwidth and non-linearity
Solution Approach 1:
The patent replaces optical coupling mechanisms with magnetic coupling through transformers. This substitution eliminates the bandwidth limitations and non-linear characteristics of optical couplers, enabling high-speed digital signal transmission with superior fidelity while maintaining galvanic isolation through magnetic field coupling
3Reliability
If capacitive isolation is used, then high-frequency signals can be transmitted, but common-mode noise rejection is insufficient
Solution Approach 1:
The patent extracts and separately processes the differential signal component from the common-mode noise by using two secondary windings connected in opposite phases. The differential circuits extract the useful signal while rejecting common-mode interference, effectively separating desired information from noise
Solution Approach 2:
The patent employs asymmetric winding configurations where the first and second secondary windings are wound in opposite directions or with opposite polarity connections. This asymmetry creates opposite-phase induced voltages that naturally cancel common-mode noise while preserving differential signal integrity
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 improves signal transmission quality and anti-interference capabilities by removing common-mode noise, ensuring the accuracy and reliability of digital signals across isolated systems.
Implementation Method 1
a primary winding L1 connect to the encoding circuit for receiving an encoded signal, and a secondary winding L21 generates a first differential signal in phase with the encoded signal through induction, and a secondary winding L22 generates a second differential signal in opposite phase with the encoded signal through induction
Data Source
AI summary
A digital isolator can include: an encoding circuit configured to receive an input digital signal, and to generate an encoded signal according to the input digital signal; an isolation element having a primary winding, a first secondary winding, and a second secondary winding; a differential circuit configured to receive first and second differential signals, and to generate a difference signal according to the first and second differential signals; and a decoding circuit coupled with the differential circuit, and being configured to receive the difference signal, and to generate a target digital signal after decoding.