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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
|
DC Output Load Regulation
|
||||||||||
|
Combined DC Load |
+3.3V
|
+5V
|
+12V
|
+5VSB
|
-12V | |||||
|
A
|
V
|
A
|
V
|
A
|
V
|
A
|
V
|
A | V | |
|
75W
|
1.08
|
3.37
|
1.45
|
5.06
|
4.90
|
12.21
|
0.50
|
5.06
|
0.20
|
-12.13
|
|
150W
|
2.08
|
3.35
|
2.98
|
5.06
|
10.05
|
12.15
|
0.50
|
5.04
|
0.30
|
-12.12
|
|
300W
|
4.29
|
3.34
|
6.00
|
5.05
|
20.62
|
12.08
|
1.00
|
5.02
|
0.30
|
-12.11
|
| 450W |
6.58
|
3.32
|
8.49
|
5.04
|
31.82
|
12.01
|
1.50
|
4.98 |
0.30
|
-12.10
|
|
600W
|
9.93
|
3.29
|
12.21
|
4.98
|
41.80
|
11.95
|
2.50
|
4.91
|
0.30
|
-12.09
|
The Cooler Master unit has good regulation across all the outputs and handles our load tests at a very capable level. All of the primary rails stayed with 3% of the nominal voltage.
| Cooler Master Silent Pro M 600W | Maximum Load |
| 674.2W |
We managed to get just over 674W out of the PSU before it would shut down, gracefully. We are happy to report that the overcircuit protection works well.
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 | 5.02 | 48.0 | 11.98 | 0.2 | -12.47 | 0.50 | 5.08 |
| 145W | 12.0 | 3.26 | 15.0 | 5.01 | 2.0 | 12.15 | 0.2 | -11.92 | 0.50 | 5.03 |
The Cooler Master PSU handled the Cross loading tests very well and we didn't experience any issues at all. All the voltages remained well within specification.
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 Cooler Master unit complied with the ATX standard.
| AC Ripple (mV p-p) | ||||
| DC Load | +3.3V | +5V | +12V | 5VSB |
| 75W | 5 | 5 | 15 | 10 |
| 150W | 5 | 10 | 20 | 10 |
| 300W | 5 | 10 | 35 | 15 |
| 450W | 10 | 15 | 40 | 15 |
| 600W | 10 | 15 | 55 | 20 |
Ripple results are well within the parameters set down in the ATX12V Ver 2.2 standard. While all the results barely registered on our equipment, the +12V line showed 55mv ripple which while still well within margins, is a little higher than we normally report on KitGuru.
|
Efficiency (%)
|
|
|
75W
|
85.21
|
|
150W
|
86.17
|
|
300W
|
86.78
|
|
450W
|
84.64
|
|
600W
|
82.02
|
These efficiency results are very strong for a unit which is rated only as having standard 80 Plus Certification. While we expected to see figures between 80 and 82 percent across the load testing they were noticeably higher between 82 and 87 percent. As the load passed 400W the efficiency dropped back down to 84 percent, falling to 82 percent at full load.
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
|
16.3
|
|
150W
|
17.8
|
|
300W
|
19.7
|
|
450W
|
22.3
|
| 600W | 24.8 |
Our noise testing proved to be massively impressive and we were pleasantly surprised to note a maximum of 24.8dBa from the unit under full load. This is without question one of the quietest power supplies we have tested and it fully lives up to the Cooler Master ‘Silent Pro M' name. Cooler Master have configured the 135mm to spin very slowly when compared to its maximum 2,000 rpm setting (37 dbA).
|
Temperature (c)
|
||
|
Intake
|
Exhaust
|
|
|
75W
|
35
|
36
|
|
150W
|
35
|
37
|
|
300W
|
37
|
40
|
|
450W
|
41
|
46
|
|
600W
|
44
|
50
|
The large fan design inside the Silent Pro M is very efficient and under 50% load the exhaust temperature doesn't rise that much compared to the intake air. Only around 400-450W does the fan spin up more to help compensate for rising ambient temperatures. A very good balance of low noise levels with reasonable air flow.
|
Maximum load
|
Efficiency
|
|
674.2W
|
78.9
|
Pushing the PSU above its rated limits generates an efficiency level of around 79%. This is not a viable ‘real world' situation, but its interesting nonetheless.
