Dual Supply/returns OR'd/12V out

Discussion in 'The Projects Forum' started by mcgyvr, May 3, 2012.

  1. mcgyvr

    Thread Starter AAC Fanatic!

    Oct 15, 2009
    Can someone take a look at this and let me know if it should work as I think it should?
    1-I have 2 power supplies that could be either +24VDC or -48VDC.
    2-I have a requirement to "diode OR" BOTH the - and + legs to create "return path" isolation between the supplies.
    3-I need 12V out (250mA max) and need to ensure it stays operation if one of the supplies turn off.

    Will the attached schematic meet the OR'd requirement as well as allowing the dual polarity operation? 99.999% of the time the polarity on both supplies will be identical but I'm hoping to ensure proper operation even if one or both of the supplies is hooked up backwards.. Or maybe they need a +24V supply and a -48V supply for other components.

    If the dual polarity was out of the question a simple schottky diode OR'ing on both the + and - leads should suffice.
  2. #12


    Nov 30, 2010
    Looks good to me. The FWB trick is commonly used where accidental polarity reversal is an option.