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Clearance/Creepage in Offline isolated flyback SMPS?

cupoftea

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Hi,
Would you agree, if doing an offline isolated flyback of 90-265vac, then the minimum number of net class's that you can get away with , when laying out the PCB, is ten?
The net class's are necessary, ayk, so that you can get the correct clearancing between the various nets. Some nets will obviously be in 2 or more of the net class's.

I am sure all would agree that at least these (attached in LTspice and PDF) net class's (12 shown here) are absolutely needed in order to properly get the right clearancing/creepaging between the various nets.
Without the shown class's, the job just can't be done properly!.....your layout will either be too big, or you will violate clearance rules.

Though good luck in finding what EN62368 or IPC2221 says about these clearances, because none of the regulations define all the spacing between all the shown nets here.
So we are on our own.....no guidance.
The only guidance you have is that clearance/creepage from Line to Neutral, upstream of the fuse, should be at least 2.5mm.
Anything else...take a guess.....though if its not the right guess, then some lawyer could call in a total product recall for you, since its open to interpretation.
 

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