Hi Jimme,


Yes you can, you'll need to add a second output filter too
of course. I'd make the second filter for the negative
output a duplicate of the existing filter except for the
polarity of the capacitors. A coupled inductor would be
better but might effect the control loop compensation.

For a 15V output I'd most likely use schottky diodes for their
low forward voltage and no reverse recovery (at the expense of
higher capacitance.) Maybe have to add a small series RC
snubber across the schottkys if there's a lot of ringing.

Any benefit to using faster recovery diodes would depend on
how fast the diodes now in use are switching. I've seen
crappy old 1N4004 diodes with 35nS recovery times when operating
at several amperes of forward current. That's ultra-fast!
But they're specified as standard recovery... this really
screwed up a base drive clamp where they were expected to be
slow.

If they are 1uS parts, changing to something faster should
reduce switching losses. Might make the supply quieter...
or more noisey! Ultra-fast parts with soft recovery would be
my second choice after schottkys. They tend to produce the
least EMI and what noise they do produce is easier to snub
and filter in addition to low switching losses.


73
Grumpy



JIMMIE wrote in news:e8aa2cc3-52af-40c4-9eed-
:

I have a 15volt 25 amp SMPS that I would like to convert to a +/- 15
volt power supply. I was wonder if I could do this by adding two
diodes to the present two diode full wave rectifier circuit to turn it
into a bridge. Also the power supply seems to be operating at about
25Khz, but the diodes are standard recovery. Would there be any
benifit to switching to fast recovery diodes.

Jimmie