Lately, I needed to extend the upper voltage rating of an SMPS (24V, 1A) from 250 to 380Vrms. So I added to it a circuit in series to act as an active high-voltage zener.
I tested the circuit on LTspice. But since I am not sure how to model the input of the AC-DC supply, I replaced it, on the schematic, with a resistive load. The simulation result shows, above a certain instantaneous mains voltage, a drop of about 200V and, below it, the drop reduces to a few volts. Both the voltage drop and the level at which the active zener is activated could be adjusted by varying 3 resistance values.
Then, I built the circuit and tested it with the SMPS in question (loaded from 0mA to 1A).
The overvoltage protection acted differently when the SMPS is used instead of the resistive load (in the simulation). I mean; although the protective circuit is added in series, the voltage on the SMPS input looks as if there were a high-voltage zener in parallel with it which lets its top voltage be rather constant/flat (say at 300V) while the input mains voltage is increased up to 400Vrms.
Do you think it will be a good idea to upload this small project in the project forum?
I asked this because the circuit has no AVR MCU (or alike; no programming). On the other hand, just a few engineers in the world may be interested in such sort of protection. And perhaps it is done already by someone.