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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 outputs are combined for testing today.
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DC Output Load Regulation
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||||||||
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Combined DC Load |
+3.3V
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+5V
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+12V
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+5VSB
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||||
|
A
|
V
|
A
|
V
|
A
|
V
|
A
|
V
|
|
|
110W
|
1.02
|
3.35
|
1.03
|
5.05
|
8.02
|
12.12
|
1.00
|
5.07
|
|
220W
|
2.04
|
3.32
|
2.02
|
5.04
|
16.01
|
12.11
|
1.00
|
5.05
|
|
305W
|
3.02
|
3.31
|
3.04
|
5.02
|
22.06
|
12.08
|
1.50
|
5.03
|
| 410W |
4.01
|
3.30
|
4.05
|
5.01
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30.12
|
12.04
|
2.00
|
5.01 |
|
515W
|
5.02
|
3.29
|
5.06
|
4.98
|
38.14
|
12.02
|
2.50
|
5.00
|
Voltage regulation is very good indeed, maintaining close to reference figures right across the testing.
| Chill Innovation CP-520W | Maximum Load |
| 550.3W |
We managed to load the PSU with 550W watts before it shut down gracefully. The overcircuit protection worked fine.
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 | |
| 493W | 1.0 | 3.31 | 1.0 | 5.03 | 40.0 | 11.78 | 0.2 | -12.12 | 0.50 | 5.05 |
| 153W | 15.0 | 3.30 | 15.0 | 4.98 | 2.0 | 12.04 | 0.2 | -11.79 | 0.50 | 4.96 |
The PSU copied well, even when loaded with 40A on the 12V rail, there was some fluctuation, noticeably on the 12v rail, but nothing outside safe parameters.
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.
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ATX12V Ver 2.2 Noise/Ripple Tolerance
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|
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Output
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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 |
| 110W | 15 | 15 | 10 | 10 |
| 220W | 15 | 15 | 10 | 15 |
| 305W | 15 | 15 | 20 | 15 |
| 410W | 15 | 20 | 30 | 15 |
| 515W | 20 | 20 | 35 | 15 |
Ripple suppression is actually very good, hitting 35mv at full load on the 12V rail. Some supplies in this sector can easily fall down with ripple testing.
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Efficiency (%)
|
|
|
110W
|
84.7
|
|
220W
|
86.3
|
|
305W
|
86.8
|
|
410W
|
86.1
|
|
515W
|
82.4
|
Efficiency results are pretty good, peaking at 86.8 at around 50 percent load, and falling to 82.4 percent efficiency 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
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Noise (dBA)
|
|
|
110W
|
27.5
|
|
220W
|
27.9
|
|
305W
|
28.8
|
|
410W
|
30.1
|
| 515W | 31.4 |
This is certainly one of the quieter power supplies we have tested, and at 100% load, the fan spins at 1,400 rpm, peaking at 31.4dBa. Fantastic results and barely audible at all.
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Temperature (c)
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||
|
Intake
|
Exhaust
|
|
|
110W
|
35
|
38
|
|
220W
|
36
|
41
|
|
305W
|
39
|
47
|
|
410W
|
42
|
50
|
|
515W
|
44
|
56
|
The large fan maintains good temperatures throughout, rising to a 12c above ambient intake threshold at full load.
|
Maximum load
|
Efficiency
|
|
550.3W
|
80.4
|
Pushing the PSU above its rated limits generates an efficiency level of around 80.4%. This is not a viable ‘real world’ situation, but its interesting nonetheless.
To test the standby power draw today, we used an ErP supported product – the MSI Big Bang XPower MS7666 Rev. 1.1 Motherboard which complies with EuP 2013 standards. This specific board has been tested and consumes 0W in Standby mode.
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ErP Lot 6 system build
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Standby Power Drain
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MSI & Chill Innovation
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0.8W
|
