In Reply to: dc voltage converter posted by ummmohd on 12/23/00 at 1:38 AM:
I was re-thinking your query on obtaining +5v from a -48v source.
To what is the +5v being referred ? Does the "0v" side of the 5 v supply have anything in common with either of the power "poles" of the -48 volts, or is it that you require complete isolation of both "poles" of the 5v supply from anything to do with -48v ?
If one side of the required 5v can be in common with one side of the -48 v then perhaps a simple series regulator, such as a 7812 with an additional 42v zener diode in the regulator "common" lead may serve your purpose. If you think of your 48v supply with an added series 43v regulator connected across it, then the regulator output will be +5v referred to the 48v negative pole. Maybe this will serve your requirement. However, you need to determine what can be "common" in both supplies before assuming that the above is a true solution.
Brian Snell (email@example.com)