[Milsurplus] 12 to 24 volt conversion, the issue of cost

[Robert Nickels]

Here's another approach that does about the same thing as the 555 using 
a couple of op-amps in a simple boost converter designed to make 24 
volts out of 12:

http://www.aaroncake.net/circuits/12VDC_To_24VDC_Converter_Circuit.asp

I can't recall how much current Michael was looking for, but the basic 
design is there.  There's also a link on this page to a 6-to-12v DC 
converter that uses discrete transistors that could also be scaled-up.  
I haven't tried but I'll bet a trashed PC power supply could be 
scrounged for a toroid and most of the parts.

73, Bob W9RAN