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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
|
3.33
|
1.45
|
5.04
|
4.90
|
12.15
|
0.50
|
5.03
|
0.20
|
-12.09
|
|
150W
|
2.08
|
3.33
|
2.98
|
5.04
|
10.05
|
12.13
|
0.50
|
5.03
|
0.30
|
-12.09
|
|
300W
|
4.29
|
3.32
|
6.00
|
5.04
|
20.62
|
12.09
|
1.00
|
5.02
|
0.30
|
-12.11
|
| 450W |
6.58
|
3.32
|
8.49
|
5.03
|
31.82
|
12.07
|
1.50
|
5.01 |
0.30
|
-12.11
|
|
600W
|
9.93
|
3.30
|
12.21
|
5.01
|
41.80
|
12.03
|
2.50
|
5.00
|
0.30
|
-12.12
|
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 2% of the nominal voltage.
| Cooler Master Silent Pro Gold 600W | Maximum Load |
| 722.1W |
We managed to get just over 720W 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 | 3.33 | 1.0 | 5.05 | 48.0 | 12.01 | 0.2 | -12.12 | 0.50 | 5.03 |
| 145W | 12.0 | 3.31 | 15.0 | 5.03 | 2.0 | 12.08 | 0.2 | -12.05 | 0.50 | 5.01 |
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 | 15 | 5 | 20 | 15 |
| 150W | 15 | 15 | 30 | 20 |
| 300W | 25 | 25 | 50 | 25 |
| 450W | 30 | 25 | 60 | 25 |
| 600W | 35 | 35 | 85 | 30 |
Ripple results are within the parameters set down in the ATX12V Ver 2.2 standard. We recorded around 85mv of ripple on the 12V output at full load (EDIT we have updated the ripple data, the wrong data was used in this table initially – user error (yes me!)). This now falls in line with the 1200W unit from the same family we already published.
|
Efficiency (%)
|
|
|
75W
|
89.75
|
|
150W
|
90.21
|
|
300W
|
92.03
|
|
450W
|
91.67
|
|
600W
|
90.46
|
Efficiency as we hoped, is fantastic, rating over 92% at 50% load. At full load we recorded over 90% which is an exceptional 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
|
23.8
|
|
150W
|
25.7
|
|
300W
|
27.8
|
|
450W
|
30.2
|
| 600W | 35.9 |
The power supply is quiet right up to 70% load when the fan starts to speed up to compensate for rising temperatures. at 450W it rates around 30 dBa rising to around 36dBa at full load. Under normal operating conditions the unit will be rating below 30 dBA which is basically silent in most living environments.
|
Temperature (c)
|
||
|
Intake
|
Exhaust
|
|
|
75W
|
35
|
38
|
|
150W
|
35
|
38
|
|
300W
|
37
|
41
|
|
450W
|
41
|
48
|
|
600W
|
44
|
52
|
The Adda AD1212MS-A71GL is a great fan which can be verified above with the combination of low noise and fantastic temperatures, rising to a peak of around 8c over ambient at full load.
|
Maximum load
|
Efficiency
|
|
722.1
|
88.12
|
At 722.1W the Cooler Master Gold PSU rated just over 88% efficiency. This is not a viable ‘real world’ situation, but its interesting nonetheless.
