We made several tests with this power supply as described in the article Hardware Secrets Power Supply Test Methodology. All the tests described below were taken with a room temperature between 47º and 50º C. During our tests the power supply temperature was between 48º and 49º C.
First we tested this power supply with fiv different loads patterns, trying to pull around 20%, 40%, 60%, 80% and 100% of its labeled maximum capacity (under “% Max Load” we list the actual percentage that was used), watching how the reviewed unit behaved under each load. On the table below we list the load patterns we used and the results for each load.
+12V2 is the second +12V input of our load tester and on this test it was connected to the power supply EPS12V connector. Keep in mind that power supply uses a multiple rail design with three virtual rails and these rails were divided between the +12V1 and +12V2 inputs from our load tester.
Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
+12V1 | 4 A (48 W) | 8 A (96 W) | 12 A (144 W) | 16 A (192 W) | 20 A (240 W) |
+12V2 | 4 A (48 W) | 8 A (96 W) | 12 A (144 W) | 16 A (192 W) | 20 A (240 W) |
+5V | 1 A (5 W) | 2 A (10 W) | 4 A (20 W) | 5 A (25 W) | 6 A (30 W) |
+3.3 V | 1 A (3.3 W) | 2 A (6.6 W) | 4 A (13.2 W) | 5 A (16.5 W) | 6 A (19.8 W) |
+5VSB | 1 A (5 W) | 1 A (5 W) | 1.5 A (7.5 W) | 2 A (10 W) | 2.5 A (12.5 W) |
-12 V | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) | 0.8 A (9.6 W) |
Total | 115 W | 220 W | 335 W | 442 W | 552 W |
% Max Load | 21% | 40% | 61% | 80% | 100% |
Result | Pass | Pass | Pass | Pass | Pass |
Voltage Stability | Pass | Pass | Pass | Pass | Pass |
Ripple and Noise | Pass | Pass | Pass | Pass | Pass |
Efficiency | 86.5% | 88% | 87% | 85.5% | 83.3% |
As you can see this power supply could not only deliver its labeled power at 50º C but could keep an efficiency of at least 83%, going as high as 88% when we were pulling around 220 W or 40% of its capacity. As for noise, the maximum level we’ve seen was of 44 mV peak-to-peak on +12V2 input during test number five, which is well below the 120 mV maximum allowed.
After being happy with these results we tried to pull even more power from NeoPower 550 and the good news is that we were able to do so, even with a room temperature of 50º C!
Below you can see the maximum amount of power we could extract from this unit keeping it working with its voltages and noise level within the proper working range. As we can see what we could do was to pull 8 amps more from the +12V1 input of our load tester. We tried other configurations (like trying to pull more from +5 V, +3.3 V and +12V2) but this was the one that provided the maximum load with the power supply working. Above that voltages weren’t within working range and ripple was thru the roof.
Input | Maximum |
+12V1 | 28 A (336 W) |
+12V2 | 20 A (240 W) |
+5V | 6 A (30 W) |
+3.3 V | 6 A (19.8 W) |
+5VSB | 2.5 A (12.5 W) |
-12 V | 0.8 A (9.6 W) |
Total | 647.9 W |
% Max Load | 117.80% |
Efficiency | 81% |
Working at this spec, however, noise level at +12V2 input doubled, jumping to 80 mV. Even though this value is still inside working specs (120 mV) it is clear to us that this power supply wasn’t projected to work above 550 W. But, as we could see, this unit will work up to 650 W at 50º C just fine – which is outstanding.
We couldn’t pull more than that from our power supply, even when we tried to increase currents little-by-little starting from the above values with the power supply already on.
It seems, however, that this power supply doesn’t have over current (OCP) and over power (OPP) protections – at least with us this unit failed on these tests.
On power supplies with OPP when we try to turn it on with a load higher than then it is capable of handling, the power supply simply won’t turn on. Also if we start increasing power with the unit already on, it will shut down whenever it reaches a point it can’t work within its specs anymore.
NeoPower 550, however, didn’t turn off under these two circumstances. It kept turned on, but with voltages below working range (+12 V dropped to +7 V, for example) and ripple thru the roof.
As for OCP we did a simple test. We connected the ATX12V connector from the power supply to the +12V2 input from the load tester. As we explained on last page, this plug is connected to the +12V1 rail and since we left the EPS12 plug unconnected this plug was the only thing connected to the +12V1 rail from the power supply. We turned on the load tester with our test number one and increased the current on ATX12V to 18 A, then to 20 A, then to 22 A, then to 24 A and the power supply didn’t shut down as it should (from the power supply label it should have shut down at 18 A or at a little bit above that).
This isn’t necessarily a bad thing. Probably we could only pull 650 W from this power supply because OCP and OPP weren’t in place.
A feature we could see in action was the fan speed changing depending on the power supply temperature. This feature is great because it reduced the noise produced by your power supply when you are not pulling a lot of power, as the fan will rotate at a lower speed.
