At 04:33 PM 10/30/02 -0500, Olin Lathrop wrote: > > Since this is a single supply with no reference common to anything else, > > put the current sense resistor in the ground lead. No problem! > >That just moves the problem of having a floating differential voltage for >voltage feedback instead of for current feedback. I'd rather use a diff >amp to sense the current and keep all the grounds common. Huh? I guess that I am missing something. Assume that the shunt is sized such that you drop 0.5V or 0.1V at full rated output current. Also assume that the current consumed by the regulator circuit is small compared to the output current. Consider the power supply to be built up from 2 functional blocks. The block on the left hand side is the power transformer / rectifiers / bulk reservoir. The block on the right is the regulator. Connect the current sense shunt in the negative leg between the 2 blocks. Note that the voltage feedback is still from the output terminals of the supply and that any voltage dropped across the shunt has no effect on the output voltage. It is then a pretty simple matter to re-arrange the regulator block such that those nodes that supply significant ground current are moved to the input side of the shunt, leaving the reference and voltage error amp referenced to the negative output terminal. Like I said - no problem! dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 18 years of Engineering Innovation (1984 - 2002) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu