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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
12V output is single rail for our testing.
|
DC Output Load Regulation
|
||||||||||
|
Combined |
+3.3V
|
+5V
|
+12V
|
+5VSB
|
-12V | |||||
|
A
|
V
|
A
|
V
|
A
|
V
|
A
|
V
|
A | V | |
|
150W
|
0.90
|
3.33
|
0.84
|
5.03
|
11.65
|
12.03
|
0.5
|
5.01
|
0.20 | -12.02 |
|
300W
|
1.63
|
3.33
|
1.65
|
5.03
|
23.75
|
12.03
|
1.0
|
5.01
|
0.20 | -12.02 |
|
750W
|
3.01
|
3.33
|
3.02
|
5.02
|
59.66
|
12.03
|
1.5
|
5.00
|
0.30 | -12.03 |
| 1125W | 4.05 | 3.33 | 4.05 | 5.01 | 90.00 | 12.02 | 2.0 | 5.00 | 0.30 | -12.02 |
|
1300W
|
8.88
|
3.32
|
8.85
|
5.01
|
98.56
|
11.98
|
2.5
|
5.01
|
0.50 | -12.03 |
Load regulation holds well across the board. Within 2%. This is a very good result for MSI.
| MSI MEG Ai1300P | Maximum Load |
| 1428W |
We managed to get the PSU to achieve 1428W before it would shut down, delivering 128W more than the rated specifications.
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 | |
| 1150W | 3.0 | 3.33 | 2.0 | 5.03 | 92.0 | 12.02 | 0.2 | -12.03 | 0.50 | 5.01 |
| 250W | 20.0 | 3.31 | 24.0 | 5.00 | 5.0 | 12.03 | 0.2 | -12.02 | 0.50 | 5.01 |
The power supply did very well in our Cross Load tests, indicating a very stable design.
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 it is (less ripple 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 |
| 150W | 5 | 5 | 10 | 5 |
| 300W | 5 | 5 | 10 | 5 |
| 750W | 5 | 10 | 15 | 5 |
| 1125W | 5 | 10 | 15 | 10 |
| 1300W | 10 | 10 | 25 | 10 |
Ripple results are very good across the board, with the +3.3V and +5V rails peaking at 10mV with the +12V rail peaking at 25mV. well within industry rated tolerance parameters.
|
Efficiency (%)
|
|
|
150W
|
91.87
|
|
300W
|
92.57
|
| 750W |
94.23
|
|
1125W
|
93.89
|
| 1300W | 91.78 |
The efficiency ratings are excellent, peaking at around 94.3% and dropping to just below 92% 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 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)
|
|
|
150W
|
<28.0
|
| 300W |
<28.0
|
|
750W
|
<28.0
|
|
1125W
|
33.7
|
| 1300W | 37.9 |
The fan in this unit does not spin under most normal load situations. It is only over 1000 watts that the fan makes its presence known, rising in speed at full load to be clearly audible. The pitch of the fan is not annoying, which is beneficial when the load gets in excess of 1,000 watts. At 1,150 watts the noise of the unit ramps up significantly to deal with the demand.
|
Temperature (c)
|
||
|
Intake
|
Exhaust
|
|
|
150W
|
36
|
38
|
|
300W
|
38
|
41 |
|
750W
|
41
|
48
|
|
1125W
|
43
|
53
|
|
1300W
|
44
|
58
|
The fan performs reasonably well, holding temperatures at modest levels throughout the load tests.
|
Maximum load
|
Efficiency
|
|
1428W
|
90.8
|
At 1428W, the efficiency level is around 90.8%.
