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
From mains a small transformer for the 4.25Vac, but finding the right voltage exactly might be tricky, perhaps a transformer kit with a wind-your-own secondary?
32 and 7.5V aren't the most common voltages either, you might find a reasonable 5W 7.5V main SMPS, and then run a DC-DC boost converter from that?
From USB it can't really be done as the usual limit is 0.5A at 5V, or 2.5W.
Thanks. I measured the existing supply and the levels were all 1 to 2V higher than the supply spec. I'll try a buck or boost converter to get the 32VDC and 7.5VDC but I havent used one before. Pity circa 5VAC is hard. Had hoped a small inverter would be available rather than dwinding a transformer,
What you need is the following:
32 VDC 100mA 7.5 VDC 150mA 4.25 VAC 350mA
To be on the save side when converting voltages you should allow for a loss or extra need of at least 25%.
32V x 100ma = 2,2W (3W) 7,5V x 150ma = 10,25W (15W) 4,25V x 350ma = 1,5W (2W)
So you need 20 Watts if you do not want to overheat your components.
At 5V this is 4A.
A 10V AC transformer and linear regulators could supply your 7,5V and 4,25V. The 4,25V will give you a loss of more than 50% of power. The 7,5V requires a low drop voltage regulator (maybe).
The 32V - sorry ......
There are lots of people who might help you.
My ideas were just quick&dirty late-evening ideas.