Before overloading the power supply we always test to see if the over current protection (OCP) circuit is active and at what level it is configured.
To test this we configured our load tester to pull only 1 A from its +12V1 input and 33 A from its +12V2 input, which this time was connected to the power supply ATX12V connector (we used the ATX12V connector because it was the only cable connected to the power supply +12V1 rail; the EPS12V connector is connected to the +12V1 and +12V2 rails at the same time). Under this scenario (i.e., pulling a lot of current from one of the power supply’s +12V rails) the power supply have to shut down, what happened, so OCP was present and active. We started lowering the current until we could turn on the power supply to determine at what level OCP was configured. This was accomplished at 29 A. We think that OCP was configured at a level that is too high, in our opinion it should be configured at a lower value like 20 A.
Connecting the EPS12V connector back on our load tester and starting from test number five shown in the previous page, we started increasing currents to see the maximum amount of power we could pull from this power supply with it still working inside ATX specs.
The maximum we could pull from this unit is summarized in the table below.
Input | Maximum |
+12V1 | 33 A (396 W) |
+12V2 | 33 A (396 W) |
+5V | 14 A (70 W) |
+3.3 V | 14 A (46.2 W) |
+5VSB | 3 A (15 W) |
-12 V | 0.8 A (9.6 W) |
Total | 940 W |
% Max Load | 125.3% |
Room Temp. | 45º C |
AC Power | 1,170 W |
Efficiency | 80.3% |
We were impressed by these results. This power supply could not only deliver 25% more than labeled (940 W) but also could keep efficiency at 80% under this extreme condition.
On the other hand, this power supply doesn’t seem to have over load protection (OPP or OLP), as usually when a power supply has this protection it shuts down if you try to pull more than 20% of its labeled power.
Ripple and noise increased a lot, to 90 mV at +12V1 input from our load tester and to 97 mV at +12V2 input from our load tester. Even though these numbers are high, they are still under the maximum allowed (120 mV).
Short circuit protection (SCP) worked fine for both +5 V and +12 V lines.
