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| Compliance with the EN55022 standard |
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Giving sufficient consideration to EMC regulations when designing power supplies is an often underestimated task. Thus the following article is intended to provide some assistance in this regard. Using Vicor components as an example, it shows how it is possible to comply with the threshold values of the EN55022 Class B standard using standard industrial components. | |
In Europe, the permissible grid-bound interference is stipulated by the threshold values of the EN55022 Class B standard. The objective of this regulation is to protect the power supply grid against interference that may be caused by devices connected to it. The EN55022 Class B standard and its sister standard, the FCC Class B standard, are also the basis for the respective national EMC regulations in many non-European countries. |
Grid-bound interference results from interference currents that are caused by clocked components in devices that are connected to the power-supply grid by a line. In this connection, it is necessary to differentiate between common-mode interference and symmetrical interference. |
Common-mode interference
Common-mode interference is reduced by connecting each input and output line to ground via a Y-capacitor. In Vicor DC-DC modules, the grounded baseplate is usually used as a ground connection. Moreover, the input line is usually configured to incorporate a choke with two windings so that it attenuates common-mode currents while allowing reverse currents (load current) to pass. |
Symmetrical interference
To reduce symmetrical interference, a Pi-filter is included in the input line, where the leakage inductance of the current-compensated choke described above can used as an inductance. A film capacitor is positioned in front of this choke and an electrolytic capacitor behind it (converter input). Fig. 1 shows an example of a circuit for reducing common-mode and symmetrical interference: |
Fig. 1: VI-230-CU DC-DC converter with circuitry for reduction of common-mode and symmetrical interference
Common-mode interference suppression:
• L1=3 mH (common mode choke, ordering number VI-PN02133 7A/18mΩ/3mH)
• C3=10 nF (Y2 capacitor 1500V, ordering number VI-01501)
• C4=4.7 nF (Y capacitor 500V, ordering number VI-01000 / SMD: VI-25283)
Symmetrical interference suppression:
• * = 35µH leakage inductance of choke L1
• C1=2.5 µF foil capacitor
• C2=100 µF electrolytic capacitor
• L2,C5: internal LC low pass of the DC-DC converter
Please contact the “Power Solutions” product management team to obtain additional information about reducing interference due to DC-DC converters. |
Go to VICOR products on SE website
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| ©2010 SE Spezial-Electronic AG |
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