Variable Power Supply controlled by microcontroller

Hello all,

I am trying to deisgn a 0-12 and 0- -12v adjustable power supply.
I am using LM2574 to generate adjustable +12v and LM337 to generate -12v.
Please see the schematic attached.
View attachment 63399

I recently found out i cannot use the digital pot mcp4462 in here because the tolerable
voltage is only 5.5v with these pots.
Can someone tell me alternate ways to control the output voltages through a microcontroller in
these cases?

Here's how I'd try to do it, assuming (a) +15V and -15V fixed supplies are available, (b) the digital pots have a maximum resistance of 100k each, and (c) independent control of the + and - adjustable supplies is required.
R1 and R4 are selected to prevent the digital pot voltage rising above ~ 3V, for compatibility with the micro controller .
U1 and U3 are unity-gain buffers. One can be omitted if a single pot is required to control both variable supplies so that they track each other.
U2 and U4 are respectively non-inverting and inverting amplifiers, each with a gain of ~ 4. The opamps need to be rail-to-rail I/O types if a wide control range is required.
M1 and M2 provide power gain. Feedback is taken from across the loads to stabilise the output voltages.

Thanks for the suggestion.
I also need to make sure a maximum current output of 500 mA for both the supplies.
Can you tell me the current can be sourced by this circuit in worst case?
Also, do i need to add a short circuit protection?
Thanks in advance?

Can you tell me the current can be sourced by this circuit in worst case?

Click to expand...

Many Amps, depending on the 15V supply and the FET ratings.

I also need to make sure a maximum current output of 500 mA for both the supplies.

Click to expand...

I'll have a think about that and get back to you.

Also, do i need to add a short circuit protection?

Click to expand...

That's for you to decide. But won't current limiting to 500mA provide that?

Here's the circuit with current-limiting. Even with a max 0.5A limit the FETs will get hot and will need substantial heat-sinks.

thanks a lot for your help.
This design seems really cool fro my purpose.

Actually i m designing a Power supply board for general lab purpose.
It will have +15v fixed(500mA), -15v fixed(500 mA), 5v fixed(1.5A) and +- 12 adjustable.
I was stuck on the adjustable ones. After lot of searching i found these ICs LM337 and LM2574.
The problem is i have already bought the compenets (all the ICs). I will see the prices of the ICs you
suggested and take a decision based on budget.

Thanks again for your help. God bless

I will see the prices of the ICs you suggested

Click to expand...

The ICs and FETs in the circuits I posted are just selections from the LTSpice simulation collection, chosen to suit the simulation. I'm not recommending any particular manufacturer. I haven't checked their package type, price etc. Many alternatives are available. Feel free to substitute other types.