For a project of mine, I'm trying to make a dual-sided SMPS that has independently variable positive and negative supply rails, current limiting, short circuit protection, etc etc...
My current plan of attack would to use a center-tapped transformer to convert wall power to about +/- 40VAC. I can easily rectify both and get about +/-28VDC. For the positive side supply I can easily use a voltage-controlled buck regulator.
My issue is that i don't know how to step down negative voltage for the minus side! i feel like a topology similar to a buck should work, but I'm not sure how to keep the transistors operating in the right modes.
I am considering using a buck-boost to get the negative output, but the controls for it are a lot higher :(
My question is basically, how could i create the variable, regulated negative voltage supply?