Reverse current blocking on switching regulator
Whoops, my mistake.  Should be a P-FET, not an N-FET, otherwise the concept is the same.  You still need to be able to set the resistor divider ratio properly based on your Vin, Vout, and the FET threshold voltage.  The 10k and 20k I show is just an educated guess for something like a 12V input at Vin and assuming the FET has a threshold voltage range of approximately 1.7V-4V.

Also, the zener may not be totally necessary, it's just there to stop the FET from having too much gate-to-source voltage if Vin is too large.







simulate this circuit &ndash; Schematic created using CircuitLab

It would still be better to use a DC-DC converter with built in reverse current output short-circuit protection though.