Active common-mode filter for capacitive-coupled isolated signalling

Angerer M, März M, Schwanninger R (2020)

Publication Type: Journal article

Publication year: 2020


Book Volume: 56

Pages Range: 73-76

Journal Issue: 2

DOI: 10.1049/el.2019.2994


Capacitive coupling is a well-established principle in isolated signalling. A major challenge esp. in power electronics is common-mode transient immunity caused by the displacement currents at the coupling capacitors. Digital isolator integrated circuits (ICs) employ modulated signalling, the authors propose an active filter circuit to remove common-mode components from baseband signals. This allows for reliable data transmission during transients in power semiconductor control, AC-coupled RS-485 or transformer-less Ethernet. The filter structure is simple and consists of two current mirrors, one for positive transients, and one for the negative. A current on one differential signal line is 'mirrored' onto the other, common-mode currents are conducted to ground. Differential signals are minimally affected. The proposed filter is verified in simulation and experiment: Baseband signalling with 50 Mbps in presence of 30 kV/ ms burst transients is achieved using discrete semiconductors. Even better results are expected when monolithically embedding the filter in an integrated circuit.

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How to cite


Angerer, M., März, M., & Schwanninger, R. (2020). Active common-mode filter for capacitive-coupled isolated signalling. Electronics Letters, 56(2), 73-76.


Angerer, Martin, Martin März, and Raffael Schwanninger. "Active common-mode filter for capacitive-coupled isolated signalling." Electronics Letters 56.2 (2020): 73-76.

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