power supply low v dc&ac

[RDSK]

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

[BrianHG]

Do you know if the 4.25vac needs to be isolated from the other supplies?
Are you allowed a common ground for the 32v and 7.5v?
What is you price budget?

[RDSK]

Thanks.  I am unsure if the 4.25VAC needs to be isolated or why if it does?  The measured Voltage was higher and perhaps a 5VAC is OK.
I think its common ground since old adapter is earthed.
Could I get 5VAC from 5VDC cheaply? Have small budget of $20.  Perhaps square wave would work?

[jeroen79]

It would be useful to know what this gadget is.

When powered from mains a simple transformer plus regulator will do fine.
Just get a separate transformer for each line.

When powered from USB you can use DC-DC boost converters to get the higher DC lines.
Without knowing what the VAC line is for it is hard to tell what get for it.
Possibly it will work fine on DC as well, possibly not.
If a square wave will do then an H bridge from the USB can make that.
An inverter could be modified by changing it's transformer or adding another transformer.

Or simply generate mains AC with an inverter and then follow the second paragraph.

[Zero999]

Could I get 5VAC from 5VDC cheaply? Have small budget of $20.  Perhaps square wave would work?

This simplest circuit I could think of. It's basically an astable multivibrator (Q1 & Q2, R1 & R2, C1 & C2) but with two additional transistors (Q3 & Q4) to act as a pull-up, forming an h-bridge. Q5, D1 & D2 and RS form a crude current limiter (maximum current = 0.6×RS = 0.6×1 = 600mA) which guards against temporary overloads and limits the current drawn when both the PNP and NPN turn on at the same time. If you need it to be able to withstand a continuous short circuit Q3 & Q4 will need to be able to dissipate 1.5W. If current limiting isn't required (not recommended, since this circuit does short circuit the power supply when all transistors are on simulataniosly) replace Rs with a short and omit Q5, D1 & D2.
https://en.wikipedia.org/wiki/Multivibrator