power supply in series; output transite capacitor voltage requirements

Thread Starter


Joined Jun 10, 2015
This is a question about the output caps on either a switcher or a linear power supply...
Say I want to connect two supplies in series, to increase voltage. Do those output
caps need to be of a higher voltage rating, or not?

I've tested this on the bench, and no smoke, but at least not immediately...
(don't try this without isolating the ground plane on switchers.)

What I have in mind is to series several laptop supplies... or, maybe I want
to series my LM317, or my newer LM723 supplies. Both of those are limited
to 40v, but I want more! (about 90v, for driving 1/4hp pump motors or other
"work" related projects, plus other nefarious experiments just for the hell of it.)

And yes, I work with isolation transformers when working with mains.


Joined Oct 3, 2015
Hello Hamlet,

The answer is no, for the output caps on individual power supply's you don't need to change the caps.
Since the voltage over the caps will stay the same.

If you want to put output caps over the power supplies combined(in series) you need caps of a higher rating that the total voltage.