small power supply

Discussion in 'Power Electronics' started by Rupert Kenna, Jan 3, 2017.

  1. Rupert Kenna

    Thread Starter New Member

    Jan 3, 2017
    1
    0
    I want to replace a power supply to a gadget, The gadget requires these inputs:
    32 VDC 100mA
    7.5 VDC 150mA
    4.25 VAC 350mA
    Please could you suggest best way to build such a supply both using
    ... mains 240 VAC input
    and/or
    ... using 5VDC USB ideally with a pass thru battery
     
  2. Bernard

    Expert

    Aug 7, 2008
    5,227
    600
    For me, the first 2 parts are easy, pull out 240 V AC to 32 V DC @ 1.5 A from box of PS's. Connect Buck converter, another box, & adjust to 7.5 V. The 4.25 AC is a problem. How is it used, is it sensitive to waveform ? Dig out 240 V to 120 V transformer & 120 V to 5 V @ 1.5 A filament transformer. Use resistive divider to drop 5 V to 4.25 V. Not having an adequate junk box, I would search the net for useable parts.
     
  3. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    9,647
    1,111
    Welcome to AAC

    Does the three outputs need to be isolated or not ?
     
  4. Marley

    Member

    Apr 4, 2016
    267
    64
    Mains supply easy. Not possible from USB as it normally only supplies 5V at 500mA maximum. Equals 2.5W maximum.
    Your outputs are a total of 5.94W and you would need additional power to account for losses in conversion.
     
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