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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 – 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
|
1.09
|
3.35
|
1.47
|
5.00
|
4.92
|
12.05
|
0.50
|
5.00
|
0.20
|
-12.05
|
|
150W
|
2.09
|
3.33
|
2.97
|
4.97
|
10.02
|
12.00
|
0.50
|
5.00
|
0.30
|
-12.06
|
|
300W
|
4.30
|
3.32
|
6.00
|
4.94
|
20.58
|
11.97
|
1.00
|
4.99
|
0.30
|
-12.06
|
| 450W |
6.57
|
3.32
|
8.48
|
4.92
|
31.79
|
11.94
|
1.50
|
4.98 |
0.30
|
-12.08
|
|
600W
|
9.94
|
3.30
|
12.20
|
4.90
|
41.78
|
11.87
|
2.50
|
4.96
|
0.30
|
-12.09
|
The Aerocool Integrator 600 Watt supply delivers decent regulation across all the outputs and handles the load tests very well. All of the primary rails held within 3% of the nominal voltage.
| AeroCool Integrator 600 Watt PSU | Maximum Load |
| 612W |
We managed to get 612W out of the PSU before it would shut down, and the protection circuitry worked well in our testing. This is always important with a low cost power supply.
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 | 5.00 | 45.0 | 11.82 | 0.2 | -12.05 | 0.50 | 5.02 |
| 145W | 12.0 | 3.28 | 15.0 | 4.88 | 2.0 | 12.05 | 0.2 | -12.07 | 0.50 | 5.00 |
The Aerocool Integrator 600 watt power supply coped with the cross loading tests, although there was fluctuation on most of the rails. The +12V rail dropped to 11.82 Volts when hit with 45 Amps.
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 | 30 | 10 |
| 150W | 15 | 10 | 40 | 15 |
| 300W | 20 | 15 | 55 | 15 |
| 450W | 30 | 20 | 70 | 20 |
| 600W | 35 | 25 | 85 | 25 |
Noise suppression falls within rated industry tolerance levels, although the +12V peak at 85mV could certainly be a little better.
|
Efficiency (%)
|
|
|
75W
|
80.23
|
|
150W
|
84.54
|
|
300W
|
85.21
|
|
450W
|
83.44
|
|
600W
|
79.23
|
Efficiency peaks at just over 85% in our tests at 300 watts load. This drops to around 79% at full load. Based on our results the unit wouldn't quite meet 80 Plus Bronze certification standards.
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 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
|
29.4
|
|
300W
|
31.6
|
|
450W
|
33.1
|
| 600W | 35.8 |
The power supply is quiet until around 350 watts when the fan spins up noticeably to deal with rising ambient temperatures. At full load it is clearly audible although not actually too intrusive due to the low pitch of the fan.
|
Temperature (c)
|
||
|
Intake
|
Exhaust
|
|
|
75W
|
35
|
43
|
|
150W
|
35
|
46
|
|
300W
|
37
|
49
|
|
450W
|
41
|
52
|
|
600W
|
44
|
57
|
The fan keeps temperatures under control, peaking at a 13c above ambient threshold when at full load.
|
Maximum load
|
Efficiency
|
|
612W
|
78.48
|
At 612 Watts the efficiency of the power supply drops to around 78.5 percent. It really wouldn't be realistic to be pushing a 600 watt power supply to its rated limit all the time however.
