John Popelish wrote:
Netgeek wrote:

This may be slight overkill (they claim it's good for 100W) but it's
inexpensive:

www.oatleyelectronics.com/kits/k168.html

Alternatively, you could put together something quite simple using
an MC34063A (try Google) - easy to use, readily available.


That unit could run cooler or produce more output if the rectified
secondary were stacked on the +12 input, so it had to produce only the
additional voltage. Just cut the secondary turns almost in half.

Or better yet, just add a few turns past the point where the drains
connect (which go up to almost twice the input supply voltage), and
connect those points to the output through one diode, each. Eliminate
the secondary, all together and raise the efficiency a bit more. But
there should be a filter choke between the rectifiers and the output
filter capacitor to average the slightly over voltage pulses with the
zero volt spaces between them.