I was curious, so I scribbled it out, it looks like the full-wave doubler shown here:zaphod_phil wrote: FYI, here's another relay supply circuit someone sent to me. I've never tried it, and I'm not quite sure how it works...
http://www.play-hookey.com/ac_theory/ps ... liers.html
with some added decoupling/filtering,
Naturally, it has the same problem that all the other schemes have, It is only suitable if the rectifier winding (the one normally used for directly heated diodes) is unused.
At a wild guess (i.e without trying to remember how to apply the maths again ) it should supply 12V or so at a few 10's of mA from a 5V winding.