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Additional technical assistance: Peter McFarland and Jeremy Price.
Correctly testing power supplies is a complex procedure and KitGuru have configured a test bench which can deliver up to a 2,000 watt DC load. Over the coming months this configuration is likely to be adjusted further and fine tuned.
We use combinations of the following hardware:
• SunMoon SM-268
• CSI3710A Programmable DC load (+3.3V and +5V outputs)
• CSI3711A Programmable DC load (+12V1, +12V2, +12V3, and +12V4)
• Extech Power Analyzer
• Extech MultiMaster MM570 digital multimeter
• Extech digital sound level meter
• Digital oscilloscope (20M S/s with 12 Bit ADC)
• Variable Autotransformer, 1.4 KVA
We will combine all the 12V rails into one big rail for testing today.
|
DC Output Load Regulation
|
||||||||||
|
Combined DC Load |
+3.3V
|
+5V
|
+12V
|
+5VSB
|
-12V | |||||
|
A
|
V
|
A
|
V
|
A
|
V
|
A
|
V
|
A | V | |
|
174W
|
3.25
|
3.38
|
3.25
|
5.03
|
11.50
|
12.21
|
0.75
|
5.18
|
0.12 | -12.13 |
|
352W
|
7.50
|
3.34
|
7.50
|
5.01
|
23.00
|
12.17
|
1.50
|
5.10
|
0.25 | -12.12 |
|
525W
|
11.25
|
3.27
|
11.25
|
4.97
|
34.50
|
12.09
|
2.25
|
5.05
|
0.37 | -12.17 |
|
700W
|
15.00
|
3.24
|
15.00
|
4.90
|
46.50
|
12.06
|
3.0
|
4.99
|
0.50 | -12.21 |
The Enermax psu is able to deliver solid load regulation on all of the outputs throughout our varied load tests – even when fully loaded, which would be outside normal parameters for the average user. In laymans terms, all the results are excellent and well within ATX specifications.
Next we want to try Cross Loading. This basically means loads which are not balanced. If a PC for instance needs 500W on the +12V outputs but something like 30W via the combined 3.3V and +5V outputs then the voltage regulation can fluctuate badly.
| Combined DC Load | +3.3V | +5V | +12V | -12V | +5VSB | |||||
| A | V | A | V | A | V | A | V | A | V | |
| 590W | 1.0 | 3.36 | 1.0 | 4.99 | 48.0 | 11.91 | 0.2 | -11.95 | 0.5 | 5.02 |
| 190W | 18.1 | 3.30 | 20.0 | 4.95 | 2.0 | 12.02 | 0.2 | -11.99 | 0.5 | 5.01 |
The Enermax unit deals very well with the crossloading tests with very little fluctuation throughout.
We then used an oscilloscope to measure AC ripple and noise present on the DC outputs. We set the oscilloscope time base to check for AC ripple at both high and low ends of the spectrum.
ATX12V V2.2 specification for DC output ripple and noise is defined in the ATX 12V power supply design guide.
|
ATX12V Ver 2.2 Noise/Ripple Tolerance
|
|
|
Output
|
Ripple (mV p-p)
|
|
+3.3V
|
50
|
|
+5V
|
50
|
|
+12V1
|
120
|
|
+12V2
|
120
|
|
-12V
|
120
|
|
+5VSB
|
50
|
Obviously when measuring AC noise and ripple on the DC outputs the cleaner (less recorded) means we have a better end result. We measured this AC signal amplitude to see how closely the Enermax unit complied with the ATX standard.
| AC Ripple (mV p-p) | ||||
| DC Load | +3.3V | +5V | +12V | 5VSB |
| 174W | 15 | 10 | 45 | 10 |
| 352W | 20 | 10 | 50 | 15 |
| 525W | 20 | 15 | 50 | 15 |
| 700W | 25 | 20 | 55 | 20 |
Ripple results are good on the +3.3V and +5V rail, rising to around 20-25mV when loaded. 12V is little higher than we had hoped between 45-50mV but to be fair these results are still well within the guidlines (under half the recommend parameters). A strong set of results when combined overall.
|
Efficiency (%)
|
|
|
174W
|
89.45
|
|
352W
|
92.13
|
|
525W
|
91.12
|
|
700W
|
88.91
|
The efficiency of the Enermax 700W PSU is nothing short of remarkable, we recorded over 90% from 175w to the full load at 700W.
|
Noise (dBA)
|
|
|
174W
|
28.4
|
|
352W
|
29.2
|
|
525W
|
33.5
|
|
700W
|
35.2
|
The noise levels are fantastic throughout and the Enermax Twister fan design clearly has benefits if a quiet running computer is your primary goal. For most of our testing the fan operates under 600rpm, never exceeding 1,000rpm at full load.
|
Exhaust Temperature (c)
|
|
|
174W
|
45.3
|
|
352W
|
46.7
|
|
525W
|
47.9
|
|
700W
|
48.2
|
The power supply delivers a great combination of very low noise with reasonable levels of heat being removed. The preset fan settings throughout the range seem to be well adjusted by Enermax.
|
Maximum load
|
Efficiency
|
|
790w
|
88.98%
|
We tried to load the PSU beyond its rated maximum to see where it would shut off, and we managed to get 790W out of it before it shut down. We measured efficiency at this level and were very pleased to see it was still hovering around the 89% mark.
