2009/5/5 Forrest W Christian : > Ok... an interesting question (at least to me)... > > I have a device (product) which is typically powered from a lead-acid > battery array.. =A0Usually either +12 or +24VDC. =A0 As part of this devi= ce, > it meters the input voltage to provide battery voltage status. > > I occasionally run into someone who needs to run off of a +48VDC (or > worse -48VDC) array. =A0 I could just regulate it down to +12 or +24V but > that would basically eliminate the ability to measure the input voltage. > > The currents are high enough (an amp or two) that I'd really prefer not > to use a linear regulator in this application. > > What I would really like to do is to create a switching supply which > will take the +48VDC in, and step it down to +24VDC... but instead of it > being regulated to 24VDC, have it be regulated to half of the input > voltage. =A0 =A0That way, the voltage monitoring remains intact, but reads > exactly half of the actual input voltage. > > To add insult to injury, it would be really nice if this was an isolated > switcher - so that I could take -48VDC and produce +24VDC out of it. > > I'm planning on digging into some of the Microchip app notes as far as > using a PIC in the SMPS applications (seems like a logical way to > proceed)... =A0but really would rather use a more 'traditional' approach. > > Ideas? > > -forrest > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > Forrest There is a configuration for a current doubler. I can't remember the exact layout but it's similar to the bridge style voltage doubler - except it uses inductors instead of capacitors. I think it requires a transformer feed which may suit your isolation requirements also. Otherwise a simple push-pull converter with a 2:1 transformer ratio ?? RP -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist