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I am designing a flyback smps power supply circuit and having trouble deciding the exact common mode choke that I should use. My power supply specs are as follows:

Input - 80-270 VAC 50/60 Hz Output - 5 VDC 1 A

I found a similar circuit but different output voltage/current:

schematic

This schematic uses 2x27 mH cmc.

On digikey these are the parameters -

inductance @ frequency

current rating - Is 100 mA enough?

DC resistance -

voltage rating -

What values should I choose? Smaller component is preferred.

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Whiskeyjack
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  • Like you calculated all other components (C2, C7, etc)? Designing a SMPS isn't just copy-pasting an example circuit... Do you have a reference to this circuit? – Huisman Feb 28 '19 at 07:24
  • @huisman - I felt that power output should be enough to decide the component. Can you please point me in right direction - what should I be considering to calculate the value of cmc to be used? Thanks – Whiskeyjack Feb 28 '19 at 07:44
  • https://www.onsemi.com/pub/Collateral/AND8038-D.PDF used the RN1140-08/2 made by Schaffner. If you want to copy-paste, make sure to do it exactly as shown in this datasheet (assuming you used that) using the same components and using the same board layout. – Huisman Feb 28 '19 at 07:51
  • The CM choke is usually present to reduce EMI. What specification of EMI are you aiming for? – Andy aka Feb 28 '19 at 08:48

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