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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. Due to public requests we have changed our temperature settings recently – previously we rated with ambient temperatures at 25C, we have increased ambient temperatures by 10c (to 35c) in our environment to greater reflect warmer internal chassis conditions.
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
• SkyTronic DSL 2 Digital Sound Level Meter (6-130dBa)
• Digital oscilloscope (20M S/s with 12 Bit ADC)
• Variable Autotransformer, 1.4 KVA
We will combine both 12V rails into one 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
|
3.36
|
3.25
|
5.00
|
11.50
|
12.11
|
0.75
|
5.18
|
0.12 | -12.09 |
|
352W
|
7.50
|
3.33
|
7.50
|
4.99
|
23.00
|
12.10
|
1.50
|
5.10
|
0.25 | -12.10 |
|
525W
|
11.25
|
3.33
|
11.25
|
4.98
|
34.50
|
12.08
|
2.25
|
5.05
|
0.37 | -12.10 |
|
700W
|
15.00
|
3.31
|
15.00
|
4.97
|
46.50
|
12.06
|
3.0
|
4.99
|
0.50 | -12.11 |
The Xigmatek power supply is able to handle our load tests with relative ease even when delivering the maximum rated power output of 700W.
| XigmaTek NRP-PC702 | Maximum Load |
| 787.4W |
We managed to push the unit to 787.4W before it would shut down, gracefully. Overcircuit protection works fine and we experienced no issues.
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.
| Cross Load Testing | +3.3V | +5V | +12V | -12V | +5VSB | |||||
| A | V | A | V | A | V | A | V | A | V | |
| 590W | 1.0 | 3.34 | 1.0 | 5.05 | 48.0 | 12.05 | 0.2 | -11.99 | 0.5 | 5.02 |
| 190W | 18.1 | 3.28 | 20.0 | 4.98 | 2.0 | 11.96 | 0.2 | -12.05 | 0.5 | 4.99 |
The Xigmatek unit delivers stable results under our intensive cross load testing with not much 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 Xigmatek unit complied with the ATX standard.
| AC Ripple (mV p-p) | ||||
| DC Load | +3.3V | +5V | +12V | 5VSB |
| 174W | 10 | 10 | 25 | 5 |
| 352W | 10 | 10 | 30 | 10 |
| 525W | 15 | 10 | 35 | 10 |
| 700W | 15 | 15 | 40 | 10 |
Ripple results are fantastic throughout and well within the parameters set down in the ATX 12V Ver 2.2 standard. The 12V line registered between 35 and 40 mv as we reached the upper levels of performance. The 3.3V and 5V lines were rock solid.
|
Efficiency (%)
|
|
|
174W
|
86.3
|
|
352W
|
88.2
|
|
525W
|
87.3
|
|
700W
|
85.3
|
The NRP-PC702 exceeds Bronze certification, peaking at 88.2 percent efficiency around 50% load. An excellent set of results for the Xigmatek unit.
|
Noise (dBA)
|
|
|
174W
|
19.2
|
|
352W
|
24.2
|
|
525W
|
27.8
|
|
700W
|
35.3
|
The supply remains quiet until around 75% load when it starts to become audible. At full load the PC702 registers around 35 dBA which is clearly noticeable.
|
Temperature (c)
|
||
|
Intake
|
Exhaust
|
|
|
174W
|
35
|
37
|
|
352W
|
37
|
42
|
|
525W
|
39
|
48
|
|
700W
|
43
|
56
|
As we get nearer to full load the exhaust temperatures increase which is clearly not helped by the rather small heatsinks inside the supply. We feel Xigmatek could have made these 33% larger to really help with cooling efficiency, there is a lot of space in this chassis going to waste.
|
Maximum load
|
Efficiency
|
|
787.4W
|
82.8
|
Pushing the PSU above its rated limits generates an efficiency level of around 82.8%. This is not a viable ‘real world’ situation, but its interesting nonetheless.
