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Remote sensing for high current power supply

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T

treez

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We have just done a 1V5, 65A output (vin=48v) power supply using a Vicor PRM48__VTM48 module cascade.
We are using remote sensing because of the volt drop through the high current trace to the load (processors). As you know, the presence of this stray trace resistance , and the output capacitors means that there is an RC filter in the power stage, and thus there is a pole in the small signal power stage transfer function because of this. This pole is of course at frequency of 1/(2.pi.R.C)

Where:
R = stray trace resistance
C = output capacitance downstream of the stray trace resistance.

We have used an extra zero in the feedback compensation to compensate for this, however, do you think we should add extra ESR with the capacitors at the output of the PRM48 in order to give compensation in the power stage itself. We aren’t used to adding ESR to capacitors , but if it cancels out the “stray” pole then it must be a good thing? We may need a decent transient response. (we don’t really know yet, not having run the processors in their prime task)
in short , we'll be more easily able to get a higher crossover if we do add the ESR to the caps. Do you have experience of doing this? It seems counter-intuitive and you just dont hear about people doing it.

- - - Updated - - -

VTM48 module
https://www.vicorpower.com/products?productType=cfg&productKey=VTM48EF020T080A00

PRM48 module
https://www.vicorpower.com/products?productType=cfg&productKey=PRM48JH480T250A00
 

Having calculated it, it is obvious that the "ESR step" from the transient load step means its not worth adding ESR to the intermediate capacitors.
 

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