I'm looking at a very simple method for overvoltage protection of a load connected to a standard external switching power supply. The load is powered by a 12V power supply, but this could be mistaken and exchanged with a higher voltage power supply instead, i.e. a 15V power supply. I was planning to simply connect a diode in parallel with the load. Is this a bad idea? My point is that the diode should have an activation voltage bigger than 12V (we can say 13V for safety reasons) and, since the power supply itself has overcurrent protection, it will automatically shut down once the diode is ON. Here it comes the circuit:
How should the diode be rated? The load is a 150W resistive/inductive type. Should I use a zener diode instead? What are the differences between the two types of diodes?