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High power SMPS's must have separate PCBs for the small signal stuff? (eg control)

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treez

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Hi
I once worked in a place where they didn’t want to do high power SMPS’s with a separate control PCB like in the following on page 11……(they said it should all go on the same PCB to save money)

Page 11...
https://www.infineon.com/dgdl/Infin...N.pdf?fileId=5546d4625f96303e015fdaa8ad107208

However, bulky power components should not go on the same PCB as lightweight signal ICs and components, especially SMD ceramic capacitors and even resistors , since the signal components are liable to fracture since the heavy power components will likely bend the PCB that they sit on..

Would you agree with this?

(Though I have to confess that having the separate PCB like on page 11, does make for awkwardness in transporting sensitive signals from eg the current sense transformer or current sense resistor to the signal PCB.)
 

I once worked in a place where they didn’t want to do high power SMPS’s with a separate control PCB like in the following on page 11……(they said it should all go on the same PCB to save money)

this is local culture
products get built to meet form, fit, function and the local culture

However, bulky power components should not go on the same PCB as lightweight signal ICs and components, especially SMD ceramic capacitors and even resistors , since the signal components are liable to fracture since the heavy power components will likely bend the PCB that they sit on..

Would you agree with this?
only a bad mechanical design allowed the "heavy power components" to bend the board enough to damage the
small signal components

this is easily(?) checked with a vibration test
mount the product as it will be mounted in its intended use and vibrate in x, y and z
one direction at a time is usual, some places can do 2 directions at a time

does it meet the spec? is it at a price the seller and buyer are satisfied with?
in the end, that's what matters
 

A clever power electronics engineer will realise its all about RFI interference - if the control is too close to tracks with high dv/dt or di/dt - then things will not work out well - plug in control cards can be tested separately and filtered and kept away from magnetics and switching nodes - to quote a tech " it's not rocket surgery " ( sic )
 
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A lot of engineers prefer modular design to keep development time low.

Also keep in mind the power and control circuitry may have very different requirements of the PCB. For example your controller may be a 0.5mm BGA requiring ten layers for routing, but the power devices might require >2oz copper weight and only four layers. Two separate boards would be much cheaper than one in such a case.
 

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