Open AccessActive common‐mode filter for capacitive‐coupled isolated signalling
Author(s) -
Angerer M.,
Schwanninger R.,
März M.
Publication year - 2020
Publication title -
electronics letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.375
H-Index - 146
ISSN - 1350-911X
DOI - 10.1049/el.2019.2994
Subject(s) - capacitive coupling , common mode signal , electronic engineering , active filter , capacitor , engineering , electrical engineering , filter (signal processing) , voltage , digital signal processing , analog signal
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/μ s burst transients is achieved using discrete semiconductors. Even better results are expected when monolithically embedding the filter in an integrated circuit.