Non isolated offline SMPS and common mode emissions?

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cupoftea

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Hi,
We have a BLDC at 17W.
It runs from non isolated 24V from Hi voltge Buck.
Mains is 100-265VAC

We need to also switch triacs which are in the neutral....so neutral is ground for all circuitry, and Neutral can contain no filter inductors or resistors etc...since we need a contiguous ground.

So that means we cant have a common mode choke.
Now, we could use a non isolated flyback instead of Buck, and then we could use a common mode choke in the incoming L and N going to the flyback. (because it wouldnt be in the flow of the Triac load current)
But flybacks give more common mode noise than bucks.........so which is best?....non isolated flyback with common mode choke, or non isolated buck without common mode choke.?
 

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