power supply - Over-voltage protection system for a 7 - 20 A Load with 4 - 5.5 V output from PSU

The power supply used on the product, is a DC-DC buck controller 24 V in (3 - 5.5 V out).

I need some suggestions to help protect a load (LED Display) which draws roughly 5 - 15 A the power supply on the product outputs 5.5 V and is capable of delivering 18 A - 25 A, the IC on our PSU can fail from time to time and cause over-voltages that destroy the LED drivers and LED displays.

I've looked into Zener clamping circuits, SCR crowbar circuits and Varistors,

But I don't know how well and how to calculate whether they would survive with the high current flow on the output of the PSU.

Any ideas?