KitGuru KitGuru.net – Tech News | Hardware News | Hardware Reviews | IOS | Mobile | Gaming | Graphics Cards
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 | |
|
135W
|
1.55
|
3.33
|
1.80
|
5.02
|
9.60
|
12.21
|
0.50
|
5.02
|
0.20
|
-12.02
|
|
275W
|
3.00
|
3.33
|
3.60
|
5.02
|
19.45
|
12.18
|
1.00
|
5.02
|
0.30
|
-12.03
|
|
675W
|
6.55
|
3.32
|
7.10
|
5.02
|
51.72
|
12.16
|
1.50
|
5.01
|
0.30
|
-12.04
|
| 1015W |
9.65
|
3.32
|
10.20
|
5.01
|
77.14
|
12.14
|
2.00
|
5.01
|
0.50
|
-12.04
|
|
1350W
|
13.09
|
3.32
|
12.45
|
5.00
|
104.33
|
12.08
|
3.00
|
5.01
|
0.80
|
-12.05
|
Load regulation is very good, with most of the major rails holding close to reference results. There is some deviation on the +12V rail, however it is a minor issue considering the overall results.
| SilverStone Zeus ZM1350W | Maximum Load |
| 1512W |
We managed to get another 162W from the power supply before the protection circuitry kicked in. The protection circuitry worked well and the unit restarted with a lower demand.
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 | |
| 1230W | 1.0 | 3.33 | 1.0 | 5.02 | 102.0 | 12.09 | 0.2 | -12.02 | 0.50 | 5.01 |
| 180W | 18.0 | 3.31 | 18.0 | 4.98 | 2.0 | 12.22 | 0.2 | -12.01 | 0.50 | 5.00 |
We placed a very heavy load on the +12V and it held well, delivering 102amps without an issue.
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 |
| 135W | 5 | 5 | 10 | 5 |
| 275W | 10 | 10 | 10 | 10 |
| 675W | 15 | 10 | 15 | 15 |
| 1015W | 25 | 15 | 15 | 15 |
| 1350W | 35 | 20 | 20 | 20 |
Ripple suppression is unquestionably superb, holding at 20mV on the +12V at full load – one of the best results you are ever likely to see. Other rails fell well within expected parameters. Excellent results all round.
|
Efficiency (%)
|
|
|
135W
|
78.97
|
|
275W
|
88.24
|
|
675W
|
91.66
|
|
1015W
|
90.98
|
|
1350W
|
89.03
|
The efficiency results are very good, peaking at 91.66 percent at 50 percent load. This drops to around 89 percent 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
|
Noise (dBA)
|
|
|
135W
|
30.2
|
|
275W
|
35.8
|
|
675W
|
38.9
|
|
1015W
|
43.5
|
| 1350W | 48.3 |
This is sadly one of the loudest power supplies we have tested and I found the ‘tone' of the fan was slightly irritating as well. We were initially concerned due to the small size of the fan and sadly our concerns were validated.
The fan is always audible and at 700W load is quite loud. It rises considerably in the last 300W of power output and I am not sure I could live with it in my main system. Pressing the fan button for full speed (4,200rpm) raises noise levels to over 50dBa.
|
Temperature (c)
|
||
|
Intake
|
Exhaust
|
|
|
135W
|
35
|
37
|
|
275W
|
36
|
43
|
|
675W
|
39
|
48
|
|
1015W
|
43
|
53
|
|
1350W
|
47
|
57
|
The fan is always quite active, pushing air through the chassis and out the other side. The internal temperatures are maintained well, but it isn't surprising considering the fan speeds.
|
Maximum load
|
Efficiency
|
|
1512W
|
87.6
|
Pushing the power supply above its rated limits generates an efficiency level of around 87.6%. This is not a viable ‘real world’ situation, but its interesting nonetheless.
