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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
• Extech digital sound level meter
• Digital oscilloscope (20M S/s with 12 Bit ADC)
• Variable Autotransformer, 1.4 KVA
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DC Output Load Regulation
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||||||||||
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Combined DC Load |
+3.3V
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+5V
|
+12V
|
+5VSB
|
-12V | |||||
|
A
|
V
|
A
|
V
|
A
|
V
|
A
|
V
|
A | V | |
|
100W
|
1.55
|
3.30
|
1.78
|
5.07
|
6.67
|
12.07
|
0.5
|
5.05
|
0.20 | -12.04 |
|
200W
|
3.13
|
3.29
|
3.45
|
5.04
|
13.53
|
12.03
|
1.0
|
5.03
|
0.30 | -12.05 |
|
400W
|
6.17
|
3.27
|
7.16
|
5.03
|
27.62
|
11.97
|
1.5
|
4.98
|
0.50 | -12.06 |
| 600W | 9.44 | 3.26 | 10.77 | 4.99 | 41.32 | 11.95 | 2.0 | 4.96 | 0.60 | -12.10 |
|
800W
|
13.24
|
3.23
|
15.09
|
4.97
|
55.45
|
11.92
|
2.5
|
4.93
|
0.80 | -12.10 |
The AeroCool Strike-X 800W has a decent load regulation, and all readings fall within acceptable parameters.
| AeroCool Strike-X 800W | Maximum Load |
| 834W |
We managed to get the PSU to hit 834W before it would shut down. delivering around 34W more than the rated 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.
| Cross Load Testing | +3.3V | +5V | +12V | -12V | +5VSB | |||||
| A | V | A | V | A | V | A | V | A | V | |
| 760W | 1.0 | 3.30 | 1.0 | 5.07 | 60.0 | 11.85 | 0.2 | -12.04 | 0.50 | 5.03 |
| 165W | 15.0 | 3.22 | 18.0 | 4.94 | 2.0 | 12.06 | 0.2 | -12.03 | 0.50 | 5.02 |
Cross loading results are acceptable, however the +12V output dropped to 11.85 when hit with 60A. Not a problem under real world conditions, but we have seen a lot better this year.
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.
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ATX12V Ver 2.2 Noise/Ripple Tolerance
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|
|
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 unit complied with the ATX standard.
| AC Ripple (mV p-p) | ||||
| DC Load | +3.3V | +5V | +12V | 5VSB |
| 100W | 10 | 10 | 20 | 15 |
| 200W | 15 | 20 | 25 | 20 |
| 400W | 20 | 40 | 35 | 25 |
| 600W | 30 | 50 | 50 | 35 |
| 800W | 35 | 65 | 70 | 40 |
Noise suppression is not good, the +3.3V rail peaked at 35 mV, which is still within rated tolerance levels, but higher than most we have tested this year. The +12V output peaks at 70mV which is safe enough, but higher than we would like. The issue is the +5V output which peaks at 65mV. This is classed as a ‘fail' and could potentially prove an issue long term, especially if the power supply is being pushed hard on a regular basis. At a 600W demand it was reading 50mV on the +5V output, which is far from ideal.
We class noise suppression as a fail for this unit.
|
Efficiency (%)
|
|
|
100W
|
81.66
|
|
200W
|
83.44
|
|
400W
|
87.68
|
|
600W
|
86.21
|
| 800W | 84.52 |
Efficiency results are not wonderful, peaking at 87.68% at 50% load. This falls short of the 80 Plus Silver Certification. Efficiency at 200W and less is also poor.
We take the issue of noise very seriously at KitGuru and this is why we have built a special home brew system as a reference point when we test noise levels of various components. Why do this? Well this means we can eliminate secondary noise pollution in the test room and concentrate on components we are testing. It also brings us slightly closer to industry standards, such as DIN 45635.
Today to test the power supply we have taken it into our acoustics room environment and have set our Digital Sound Level Noise Decibel Meter Style 2 one meter away from the unit. We have no other fans running so we can effectively measure just the noise from the unit itself.
As this can be a little confusing for people, here are various dBa ratings in with real world situations to help describe the various levels.
KitGuru noise guide
10dBA – Normal Breathing/Rustling Leaves.
20-25dBA – Whisper.
30dBA – High Quality Computer fan.
40dBA – A Bubbling Brook, or a Refrigerator.
50dBA – Normal Conversation.
60dBA – Laughter.
70dBA – Vacuum Cleaner or Hairdryer.
80dBA – City Traffic or a Garbage Disposal.
90dBA – Motorcycle or Lawnmower.
100dBA – MP3 Player at maximum output.
110dBA – Orchestra.
120dBA – Front row rock concert/Jet Engine.
130dBA – Threshold of Pain.
140dBA – Military Jet takeoff/Gunshot (close range).
160dBA – Instant Perforation of eardrum.
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Noise (dBA)
|
|
|
100W
|
28.0
|
|
200W
|
29.2
|
|
400W
|
31.3
|
|
600W
|
33.6
|
| 800W | 36.8 |
The large fan is quite good until the last 200W of total power output, when it rotates much faster to ensure an adequate thermal curve. At full load it is clearly audible, although never too annoying.
|
Temperature (c)
|
||
|
Intake
|
Exhaust
|
|
|
100W
|
37
|
41
|
|
200W
|
39
|
45
|
|
400W
|
42
|
48
|
|
600W
|
44
|
53
|
|
800W
|
47
|
58
|
The temperatures rise as the fan becomes more active. The overall cooling performance is quite good.
|
Maximum load
|
Efficiency
|
|
834W
|
83.78%
|
For those interested, we measured efficiency when stressing the unit to breaking point. 83.78% at 834 watts. Not realistic at all, but an interesting closing point.
