"John Larkin" wrote in message
...
A switching regulator can approach 100%, but is probably not worth the
hassle here.

Pffbt ;-)
http://webpages.charter.net/dawill/Images/CC_Buck.gif
With a regulated 5V rail, you can replace the two diodes with a resistor.
You can also drop the capacitor, at some expense to switching performance.

The feedback winding is so small, you can probably use an ordinary solenoid
choke and run a few loops of track around it on the PCB.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms