Y caps do nothing to prevent SMPS malfunction due to noise?

[cupoftea]

If you are doing an offline 1+ kw isolated SMPS that is purely a prototype, and will never go for approvals, you still damp the fet switching transitions, because if you don’t, the noise may mean it not working.

However, would you agree, you would not bother adding Y caps across the transformer isolation barriers, or from Line/Neutral to earth?…because loads of common mode noise will not interfere with the operation?......it may offend the local radio frequency allocation agencies....but wont stop the SMPS from working?

 

[betwixt]

I would agree but for the tiny cost of adding them is it worth not doing it.

Brian.