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 installed only the main motherboard cable and the two ATX12V connectors to the +12V1 input from our load tester, so the load tester was connected only to the +12V1 rail from the power supply.
We started increasing the current at +12 V up to the limit of our load tester – 33 A – but the power supply didn’t shut down. Since the power supply label says that each rail has a 25 A limit, we wanted to see the power supply shutting down if we pulled more than 25 A from any +12 V rail, what didn’t happen.
When we opened the power supply we could clearly see each virtual rail connected to the monitoring integrated circuit, so on this power supply OCP is probably configured at a value that is higher than 33 A. We don’t like this kind of configuration; we think the OCP should be configured at a value close to what is written on the label.
We reinstalled the power supply to our load tester like it was installed before and starting from test number five (see previous page) we started increasing current being pulled from the 12 V inputs from our load tester.
The maximum we could pull from this unit with it still working inside ATX specs is summarized in the table below.
Input | Maximum |
+12V1 | 22 A (264 W) |
+12V2 | 20 A (240 W) |
+5V | 8 A (40 W) |
+3.3 V | 8 A (26.4 W) |
+5VSB | 2.5 A (12.5 W) |
-12 V | 0.5 A (6 W) |
Total | 596.8 W |
% Max Load | 113.7% |
Room Temp. | 49.3º C |
PSU Temp. | 51.1º C |
AC Power | 703 W |
Efficiency | 84.9% |
See how efficiency was still around 85%, which is fantastic.
The only problem is that above this configuration the power supply would turn on with ripple on the moon. When we pulled even more power voltages were far below their expected values (for example, +12 V output at 10.79 V), so under voltage protection (UVP) would have to enter in action shutting the power supply down, which didn’t happen (probably UVP was configured to shut down the power supply only if voltages reached a lower value – which doesn’t make sense, in our opinion). According to Enermax UVP is set at 9.5 V.
In summary, the power supply didn’t shut down in the case of an overloading situation as it should; the unit kept running providing voltages with extreme high ripple and wrong values. On the other hand, the unit didn’t burn.
With the power supply delivering practically 600 W ripple level at +12V1 was 75.4 mV, at +12V2 was 75.8 mV, at +5 V was 13.6 mV and at +3.3 V was 10 mV.
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Figure 19: Noise level at +12V1 with this power supply delivering 596.8 W.
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Figure 20: Noise level at +12V2 with this power supply delivering 596.8 W.
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Figure 21: Noise level at +5V with this power supply delivering 596.8 W.
Short circuit protection (SCP) worked fine for both +5 V and +12 V lines.
The fan used on this power supply is extremely quiet even when it was running at its full speed. In fact this was the quietest power supply we reviewed to date.
