Before overloading power supplies we always test first if the over current protection (OCP) circuit is active and at what level it is configured. For this test we configured our load tester to pull 1 A from each output (0.5 A for -12 V) and increased current at +12V2 until the power supply shut down. This happened when we tried to pull more than 20 A from it. The label says this output has a maximum capacity of 18 A so the OCP from this power supply is configured the way we like: close to what is printed on the power supply label.

Below you can see the maximum values we could pull from this power supply. Far more than that the unit wouldn’t even turn on and if we tried to pull a little bit more current than that (19 A from each +12 V rail) the unit would shut down after one minute. It is always nice to see the power supply protections kicking in. During this overloading noise level was still inside specs and in fact increased just a little bit, to 24 mV at +12V1, +5 V and +3.3 V, with +12V2 at 72.8 mV.

As you can see under this scenario efficiency dropped below the 80% level.