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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.
We test ambient temperatures at 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 | |
|
60W
|
0.91
|
3.33
|
0.95
|
4.99
|
3.90
|
12.02
|
0.50
|
5.01
|
0.20
|
-12.04
|
|
120W
|
1.58
|
3.31
|
1.60
|
4.96
|
8.20
|
12.01
|
1.00
|
4.98
|
0.20
|
-12.04
|
|
300W
|
3.02
|
3.28
|
3.10
|
4.95
|
21.90
|
11.99
|
1.50
|
4.95
|
0.20
|
-12.05
|
| 450W |
4.15
|
3.27
|
4.12
|
4.92
|
33.56
|
11.96
|
2.00
|
4.92 |
0.30
|
-12.06
|
|
600W
|
5.15
|
3.25
|
5.33
|
4.88
|
45.29
|
11.94
|
2.50
|
4.88
|
0.30
|
-12.07
|
Load regulation is fair, – the +12V rail is quite good, but 3.3V, 5V and 5VSB are quite loose.
| FSP Dagger 600W SFX | Maximum Load |
| 607W |
We managed to get 607W out of the power supply before it shut down. Not one of the greatest results we have seen.
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 | 4.98 | 46.0 | 11.92 | 0.2 | -11.95 | 0.50 | 4.97 |
| 145W | 12.0 | 3.22 | 15.0 | 4.87 | 2.0 | 12.00 | 0.2 | -12.00 | 0.50 | 4.93 |
The supply passed the cross load test, although the results show quite a variation on the rails.
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 | 25 | 20 | 15 | 10 |
| 150W | 30 | 20 | 20 | 10 |
| 300W | 40 | 30 | 25 | 15 |
| 450W | 55 (fail) | 35 | 30 | 20 |
| 600W | 70 (fail) |
35 | 30 | 20 |
Noise suppression is a bit of problem – mainly the +3.3V rail which falls out of spec around 430 Watts load. At full load it rises to around 70mV – a full 20mV above the maximum tolerance guidelines.
The +12V ripple suppression results are good – peaking at around 30mV under full load conditions. We don't often get power supplies to review that fail these tests, so its quite concerning to see.
|
Efficiency (%) 230V
|
|
|
75W
|
78.86
|
|
150W
|
90.35 |
|
300W
|
91.21
|
|
450W
|
88.67
|
|
600W
|
88.23
|
Efficiency peaks at just over 91 percent at around 300 watt – 310 watt load. This drops down to just over 88% at full load. It falls a little short of 92% Gold certification in our tests.
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
|
<28.0
|
|
300W
|
32.4
|
|
450W
|
33.9
|
| 600W | 35.7 |
The fan is never that intrusive during general operation – spinning relatively slowly … although if you task the power supply with a constant load close to the maximum 600 watt rating, the fan will spin up quickly to compensate for rising temperatures. This is really not a realistic real world situation to be running however.
|
Temperature (c)
|
||
|
Intake
|
Exhaust
|
|
|
75W
|
35
|
41
|
|
150W
|
35
|
46
|
|
300W
|
37
|
53
|
|
450W
|
41
|
61
|
|
600W
|
44
|
68
|
The small fan is equipped with a fairly passive profile – its only in the last 15% of load that it starts to spin up dramatically to compensate for rising temperatures inside the chassis.
|
Maximum load
|
Efficiency
|
|
607W
|
87.9
|
At 607W the FSP power supply drops to 87.9%. This is not a viable ‘real world’ situation, but its interesting nonetheless.
