Before overloading power supplies we always test first if the over current protection (OCP) circuit is active and at what level it is configured.

In order to do that we increased current on the +12 V rail until the power supply shut down. This happened when we tried to pull more than 47 A from it.

Manufacturers always leave a margin between what is written on the label (42 A in this case) and the level the OCP circuit is really configured (47 A in this case). We always like to see this margin as tight as possible.

Then starting from test five we increased currents to the maximum we could with the power supply still running inside ATX specs. The results are below. When we tried to increase one more amp at any output ripple and noise at +12 V would increase above the maximum allowed (120 mV).

The idea behind of overload tests is to see if the power supply will burn/explode and see if the protections from the power supply are working correctly. This power supply didn’t burn or explode during our overload tests.