Reverse current protection for power supply

[hlavac]

I want to use a cheap 12V/20A LED power supply to power my 3D printer.
I suspect it has no protection for reverse current (back EMI from motors) as it is made for LEDs that will never force reverse current back into power supply.

I need a protection circuit that will stop the voltage/current that gets induced when someone moves the motors by hand quickly from destorying the power supply...

I was thinking about putting a 13V zener across the output but that looks a bit flimsy... biggest power zener I can find atm is 5W rated. Higher power zeners are ridiculously expensive...

Anyone got a good circuit that will
- short out at 13V thru something beefy that can take ~50W of power
- release once the voltage drops back to 12V so that the power supply is not shorted out
- will not oscillate (much)
?

[hlavac]

Maybe something like this?

[george graves]

I use one of those on my 3d printer.  So do lots of people, without issue.   Just FYI.