Digital Isolator Receiver Notch Filtering for Common-Mode Transients
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Solution Overview
Problem
Communication across isolation channels is susceptible to common mode transients, which can interfere with the accuracy of the information transmitted, and existing solutions introduce substantial propagation delay or have gaps in transient suppression.
Innovation Solution
A differential receiver circuit incorporating a band-stop filter and high-pass filter configuration, with a notch filter and buffer circuit, attenuates common mode transient energy independently of pulse width, reducing interference and propagation delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional isolation techniques are used to prevent damaging currents, then safety and isolation are improved, but common mode transients can still interfere with signal accuracy
Solution Approach 1:
The receiver circuit is segmented into multiple functional blocks: a first high-pass filter for initial transient attenuation, a band-stop filter with notch filter for targeted frequency rejection, and a demodulator for signal recovery. Each segment handles specific aspects of transient suppression, allowing the system to maintain isolation safety while preserving signal accuracy through specialized processing at each stage.
Solution Approach 2:
The band-stop filter with notch filter acts as an intermediary between the high-pass filter and the demodulator. It specifically targets and attenuates common mode transient frequencies without affecting the carrier signal, serving as a mediator that protects the signal path from transient interference while maintaining signal integrity for accurate demodulation.
2Reliability
If existing transient suppression solutions are implemented, then common mode transient immunity is improved, but substantial propagation delay is introduced
Solution Approach 1:
The notch filter is designed with a specific quality factor (Q) and center frequency tuned to match the carrier frequency, creating a narrow stopband that precisely targets transient frequencies. By optimizing the filter parameters (Q-factor, cutoff frequencies, and notch depth), the circuit achieves effective transient suppression with minimal impact on the carrier signal propagation, thereby reducing overall propagation delay compared to broader frequency suppression methods.
3Reliability
If broader frequency suppression is used to attenuate transients, then transient immunity is improved, but signal distortion and propagation delay increase
Solution Approach 1:
The band-stop filter applies suppression selectively only in the narrow frequency range of the stopband centered at the notch frequency, while leaving other frequency components including the carrier signal unaffected. This localized filtering approach ensures that transient energies at specific frequencies are attenuated without causing broad signal distortion, preserving the integrity of the transmitted information.
Solution Approach 2:
The filter design dynamically adapts to the carrier frequency by positioning the notch frequency and stopband accordingly. The quality factor and bandwidth of the notch filter are optimized to track the carrier signal characteristics, ensuring that the suppression action is dynamically aligned with the signal of interest and does not inadvertently distort the transmitted data.
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 attenuates common mode transient energy, improving immunity to interference and reducing propagation delay, thereby enhancing the accuracy and reliability of signal transmission across isolation channels.
Implementation Method 1
a band-stop filter having a stopband fSB around a notch frequency fn of a received signal
Implementation Method 2
a first high-pass filter coupled in series with the band-stop filter
Data Source
AI summary
A technique for attenuating common mode transient events uses a differential receiver circuit including a band-stop filter having a stopband fSB around a notch frequency fn of a received signal. The differential receiver circuit includes a first high-pass filter coupled in series with the band-stop filter. The notch frequency fn is less than a carrier frequency fc of a signal received by the differential receiver circuit. The band-stop filter may include a buffer circuit and a notch filter coupled in series with the buffer circuit. The notch filter may have a second stopband around the notch frequency fn. The differential receiver circuit may have a propagation delay that is independent of a pulse width of common mode transient energy attenuated by the differential receiver circuit.