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If there is CM EMI on DC power supply lines, can a CM choke be used at the output of SMPS supply? Im asking because all CM examples I saw are for AC power lines.

floppy380
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  • It certainly can be used on an output like that. Make sure that it is used with output capacitors to ground though because, on its own it is only 50% of a solution. – Andy aka Dec 07 '18 at 19:46
  • Thank you you could write this as an answer, do you mind if I open a more specific question about that? About Smps caps and using ferrite core at particular EMI freq – floppy380 Dec 07 '18 at 22:45
  • I’ll wait in case anyone else contributes because I’m unable to make a proper detailed answer at the moment. – Andy aka Dec 07 '18 at 22:48
  • I see; my other question here anyway: https://electronics.stackexchange.com/questions/411067/what-value-and-type-of-capacitors-must-be-used-after-cm-chokes-for-a-known-emi-f Im sure will not get much attetion as well. – floppy380 Dec 07 '18 at 23:41

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Can a CM choke be used at the output of SMPS supply?

Common mode chokes (in conjunction with the appropriate filter capacitors to ground) can certainly be used on the output of a SMPS: -

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Picture taken from Maxim Tutorial 716 - see section entitled "Common-Mode Noise". Although not always needed (if one rail of the output is grounded), for low output noise applications they tend to be used along with a regular LC filter.

Andy aka
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