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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
|
DC Output Load Regulation
|
||||||||||
|
Combined DC Load |
+3.3V
|
+5V
|
+12V
|
+5VSB
|
-12V | |||||
|
A
|
V
|
A
|
V
|
A
|
V
|
A
|
V
|
A | V | |
|
75W
|
1.27
|
3.34
|
1.22
|
5.05
|
4.95
|
12.07
|
0.50
|
5.04
|
0.20
|
-12.05
|
|
150W
|
2.17
|
3.33
|
2.87
|
5.04
|
10.07
|
12.07
|
1.00
|
5.04
|
0.30
|
-12.05
|
|
375W
|
6.17
|
3.33
|
6.05
|
5.03
|
26.15
|
12.06
|
1.50
|
5.03
|
0.50
|
-12.06
|
| 565W |
10.36
|
3.33
|
10.87
|
5.02
|
38.32
|
12.05
|
2.00
|
5.03 |
0.60
|
-12.07
|
|
760W
|
10.78
|
3.32
|
13.92
|
5.02
|
54.05
|
12.04
|
3.00
|
5.02
|
0.80
|
-12.08
|
Regulation is as good as we have seen, holding steady across all the rails. The +3.3V and +5V rail hardly moved at all, regardless of the load
| Corsair AX760 | Maximum Load |
| 902W |
We managed to push this supply to 902W before it would shut down safely. It is clearly over specified for the wattage rating.
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 | |
| 734W | 1.0 | 3.33 | 1.0 | 5.05 | 60.0 | 12.03 | 0.2 | -12.05 | 0.50 | 5.03 |
| 154W | 15.0 | 3.32 | 15.0 | 5.02 | 2.0 | 12.07 | 0.2 | -12.05 | 0.50 | 5.03 |
The Corsair AX760 delivered class leading results. We hit the power supply with 60A on the +12V rail and it held at 12.03v. Other rails also exhibited fantastic results.
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 | 10 |
| 150W | 10 | 10 | 20 | 15 |
| 375W | 15 | 15 | 25 | 15 |
| 565W | 15 | 15 | 35 | 15 |
| 760W | 20 | 15 | 35 | 20 |
Ripple suppression is very good, holding the +12V rail at full load @ 35mV, well within industry specifications. Other rails are also held well within industry tolerance guidelines.
|
Efficiency (%)
|
|
|
75W
|
86.95
|
|
150W
|
92.41
|
|
375W
|
93.92
|
|
565W
|
92.45
|
|
760W
|
91.77
|
Efficiency of the power supply peaked close to 94 percent at 50 percent load, dropping to just under 92 percent efficiency at full load. Excellent results.
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
|
Noise (dBA)
|
|
|
75W
|
<28.0
|
|
150W
|
<28.0
|
|
375W
|
<28.0
|
|
565W
|
31.7
|
| 760W | 33.4 |
This power supply is very quiet in Hybrid mode, with the fan only spinning up once we hit around 430W load. Even around 600W load it was barely audible. The high grade 120mm fan really helps maintain a very low acoustic curve.
|
Temperature (c)
|
||
|
Intake
|
Exhaust
|
|
|
75W
|
36
|
41
|
|
150W
|
38
|
44
|
|
375W
|
39
|
47
|
|
565W
|
45
|
54
|
|
760W
|
47
|
58
|
Exhaust temperatures are excellent, reaching a maximum delta of +11c above intake ambient.
|
Maximum load
|
Efficiency
|
|
902W
|
89.44
|
For those interested, we measured efficiency when stressing the unit to breaking point. 89.44 percent efficiency at 902W … hardly practical, but interesting regardless.
