some years pass, I have the same problem to solve, I am building a 100v-> 36-5volts DC DC buck converter, everything is sorted out except the control circuit, given that this stuff will operate at 100 volts, an analog approach would be an insane work, a digital approach could simplify everything, except, how do I power that arduino reliably ?? well, doing some math I figured that a zener diode regulator would dissipate way too much heat to be practical.
I came up with an idea, basically use the zener regulator approach as a "kickstarter" for the system, it'll only have to work for less than a second until the arduino switches the 100 volts down into a safer range for a commercial buck converter to handle, then the arduino will switch the zener circuitry off (via mosfets), and switch the buck converter supply on (use a dead time + capacitors to keep the arduino on during that time), this will get rid of the heat dissipation issue, issue is, when I simulated a circuit for that, I couldn't get rid of a ground loop that was interfering with the mosfets, an isolated power supply is simply necessary, I am still experimenting on this project. . .
I came up with an idea, basically use the zener regulator approach as a "kickstarter" for the system, it'll only have to work for less than a second until the arduino switches the 100 volts down into a safer range for a commercial buck converter to handle, then the arduino will switch the zener circuitry off (via mosfets), and switch the buck converter supply on (use a dead time + capacitors to keep the arduino on during that time), this will get rid of the heat dissipation issue, issue is, when I simulated a circuit for that, I couldn't get rid of a ground loop that was interfering with the mosfets, an isolated power supply is simply necessary, I am still experimenting on this project. . .