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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
12V output is combined for our testing
|
DC Output Load Regulation
|
||||||||||
|
Combined DC Load |
+3.3V
|
+5V
|
+12V
|
+5VSB
|
-12V | |||||
|
A
|
V
|
A
|
V
|
A
|
V
|
A
|
V
|
A | V | |
|
75W
|
1.09
|
3.36
|
1.47
|
5.03
|
4.92
|
12.12
|
0.50
|
5.03
|
0.20
|
-12.08
|
|
150W
|
2.09
|
3.35
|
2.97
|
5.01
|
10.02
|
12.11
|
0.50
|
5.02
|
0.30
|
-12.09
|
|
300W
|
4.30
|
3.34
|
6.00
|
5.00
|
20.58
|
12.08
|
1.00
|
5.01
|
0.30
|
-12.10
|
| 450W |
6.57
|
3.34
|
8.48
|
4.99
|
31.79
|
12.06
|
1.50
|
5.00 |
0.30
|
-12.12
|
|
600W
|
9.94
|
3.33
|
12.20
|
4.98
|
41.78
|
12.04
|
2.50
|
4.98
|
0.30
|
-12.13
|
The be quiet! Straight Power 10 CM exhibits good load regulation, holding well across all loads, across all rails.
| be quiet! Straight Power 10 CM 600W | Maximum Load |
| 688W |
We managed to get 688W out of the PSU before it would shut down, gracefully.
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 | 3.35 | 1.0 | 5.03 | 46.0 | 12.02 | 0.2 | -12.09 | 0.50 | 5.02 |
| 145W | 12.0 | 3.34 | 15.0 | 4.97 | 2.0 | 12.14 | 0.2 | -12.07 | 0.50 | 5.03 |
The be quiet! Straight Power 10 CM 600 watt handled the cross loading tests well with only a minor shift on the +12V rail.
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 unit complied with the ATX standard.
| AC Ripple (mV p-p) | ||||
| DC Load | +3.3V | +5V | +12V | 5VSB |
| 75W | 10 | 10 | 15 | 15 |
| 150W | 15 | 15 | 20 | 15 |
| 300W | 15 | 15 | 30 | 15 |
| 450W | 15 | 15 | 35 | 15 |
| 600W | 20 | 15 | 45 | 20 |
Noise suppression is very good, peaking between 15mV and 20mV on the +5V and +3.3V rails respectively. The +12V rail peaked at 45mV when at full load. These are all well within rated industry tolerance levels.
|
Efficiency (%)
|
|
|
75W
|
87.34
|
|
150W
|
88.77
|
|
300W
|
92.12
|
|
450W
|
91.56
|
|
600W
|
89.38
|
Efficiency rates as excellent, peaking at 92.12% when loaded to 50%. At full load the efficiency drops to 89.38%, a good result.
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 SkyTronic DSL 2 Digital Sound Level Meter (6-130dBa) 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 Refridgerator
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
|
Noise (dBA)
|
|
|
75W
|
28.0
|
|
150W
|
28.0
|
|
300W
|
28.0
|
|
450W
|
31.2
|
| 600W | 32.1 |
The Silent Wings 3 BQ SIW3-13525-HF fan is exceptionally quiet, rating below the accurate limits of our sound meter at 28dBa until around 375 watts is demanded. At 450Watts load, the fan spins up a little, although it is likely the minor fan noise would be masked completely with a chassis fan running in tandem. At full load, it rises to 32dBa.
In real world terms you are unlikely to hear any fan noise regardless of the load.
|
Temperature (c)
|
||
|
Intake
|
Exhaust
|
|
|
75W
|
35
|
40
|
|
150W
|
35
|
42
|
|
300W
|
37
|
45
|
|
450W
|
41
|
50
|
|
600W
|
44
|
55
|
The large Silent Wings 3 fan may be almost inaudible, even at full load – but it does produce a decent level of air, holding an excellent thermal curve result.
|
Maximum load
|
Efficiency
|
|
688W
|
88.89
|
At 688W the be quiet! Straight Power 10 CM drops to 88.9% efficiency. This is not a viable ‘real world’ situation, but its interesting nonetheless.
My old BeQuiet Dark Power Pro P10 550w, is still more quiet, than this new line of theirs 😛