small power supply

Thread Starter

Rupert Kenna

Joined Jan 3, 2017
1
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
 

Bernard

Joined Aug 7, 2008
5,784
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.
 

Marley

Joined Apr 4, 2016
502
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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