/diy/ - Do It Yourself

Powersupplyfaggotry person again

EEfag(s) pls halp

So about that tracking preregulator (switching)
I think this circuit will work, but I don't know for certain if it might not work(nor cases where it might not).

The right side resistor network is buffered by an op amp. Then its output goes to the inverting input of the difference amplifier. Rg and Rf provides gain so that the left op amp gives the difference in voltage between those two points (without having to be exposed to 30V+, since the op amps will be powered by 12 or 15V)

The circuit should give a difference of 3.5 to 5V (depending on what i want the difference to be) all the way from zero volts output to max 30V output. (so the voltage at the top of the left side resistor network should go between 3.5V - 33.5V) Is this indeed the case?
What issues might i run into with oscillation?

The idea is for that 3.5V to be fed into the inverting input of another (third) op amp with 3.5V - 5V on the non-inverting input. The output of this third op amp would be fed to the feedback pin of the buck regulator such that it keeps a constant 3.5V - 5V DC overhead

Would this indeed work? esp. down near zero volts? With all the op amps, what instances would i experience oscillation if any? What issues would there be with first turning applying power? Also, is using this many op amps a bit excessive?