If I need more power than one of the lab PSUs can supply, I connect them
in parallel. This works well because both do not only limit their
individual output voltages, but they also individually limit the current
they supply to the load (and, as lab supplies, they don't get confused
by being fed backwards, so I don't need the diodes). Some twiddling with
the knobs allows perfect balancing of load between the supplies, running
only one in "voltage source" mode, the other(s) in "current source" mode
effectively.
So, I think if you use PSUs that have a current limiting circuit that is
not only for short-circuit protection, but engages smoothly as current
approaches the continuous rating of the PSU, you should be able to
connect them in parallel with said diodes. Of course, these PSUs will
not be the cheapest devices...
However, this setup may get difficult if loading varies widely.
Another problem might be shutting down the entire system if one or more
of the supplies fail: you wouldn't want the remaining ones to supply as
much current as they can, keeping the voltage only half-way up and
running your circuitry in brown-out mode.
Andreas
"Davison, Lee" wrote:
>
> but it won't help with the current distribution problem. The PSU
> who's output after the diode drop is the highest voltage will end
> up sourcing all the current. Not what you really want.
>
> -tony
>
> Not quite, the forward volt drop of the diodes will even
> out the current between the individual units. Even
> shottky barrier diodes have a vf of >0.4v at the curents
> that would be involved.
>
> Lee.
--
Andreas Freiherr
Vishay Semiconductor GmbH, Heilbronn, Germany
http://www.vishay.com
Received on Tue Apr 16 2002 - 04:34:33 BST