I had posted this problem earlier, but without detailing much how the power supply is to be used.
I have written a perhaps more detailed web page that explains how it is to be used.
I put this question to a professor of electrical engineering who is an expert in circuit design, but he could not give much time to it and wrote a schematic that was short of what I needed, such as which parts to buy (name and/or part number) so that I can build something to test. I put his explanation and drawn schematic on this web page. If someone can actually name the part numbers, I can buy and put them together for testing (if you can suggest where I buy them too, that would be helpful).
I was looking for a low cost (say no more than a couple of hundred dollars), easily implementable solution.
That solution could be buying an already assembled set of components in the box from a maker, or building something on a circuit (prototype?) board with components piece-by-piece...opamp, MOSFET, resistor, capacitor, etc.
It must be a solution that requires that the person has only a fundamental understanding of the physics of electricity, and who may know how to use a soldering iron.