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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
We are combining all +12V rails for testing today.
|
DC Output Load Regulation
|
||||||||||
|
Combined DC Load |
+3.3V
|
+5V
|
+12V
|
+5VSB
|
-12V | |||||
|
A
|
V
|
A
|
V
|
A
|
V
|
A
|
V
|
A | V | |
|
305W
|
3.42
|
3.42
|
3.45
|
5.08
|
19.21
|
12.30
|
2.02
|
5.05
|
0.20 | -12.01 |
|
600W
|
6.75
|
3.40
|
6.72
|
5.06
|
40.01
|
12.22
|
2.05
|
5.04
|
0.40 | -12.05 |
|
902W
|
10.12
|
3.38
|
10.15
|
5.02
|
60.01
|
12.08
|
2.12
|
5.03
|
0.60 | -12.08 |
|
1330W
|
15.28
|
3.29
|
15.31
|
4.95
|
90.11
|
11.83
|
2.43
|
4.97
|
0.80 | -12.11 |
| Enermax MaxRevo 1350W | Maximum Load |
| 1438W |
We managed to get 1438W from the unit before it would switch off. The overcircuit protection system worked fine and it shut down safely. The +12V output we noticed dropped to 11.83 under full load, which while within specifications is a considerable drop from 12.30V at around 300W load.
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 | |
| 1050W | 3.0 | 3.40 | 2.0 | 5.03 | 85.0 | 11.89 | 0.20 | -12.02 | 0.50 | 4.96 |
| 200W | 19.0 | 3.30 | 22.0 | 4.97 | 2.5 | 12.13 | 0.20 | -12.05 | 0.50 | 5.02 |
The Enermax MaxRevo handled the Cross loading tests very well, maintaining steady results across all the rails. All voltages remained within stated tolerances.
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 Enermax unit complied with the ATX standard.
| AC Ripple (mV p-p) | ||||
| DC Load | +3.3V | +5V | +12V | 5VSB |
| 305W | 5 | 10 | 10 | 10 |
| 600W | 10 | 10 | 15 | 15 |
| 902W | 10 | 15 | 25 | 15 |
| 1330W | 20 | 30 | 35 | 20 |
Ripple results are well within the parameters set down in the ATX12V Ver 2.2 standard. +3.3V and +5V peak at 20mV and 25mV respectively and the +12V rail settles at 35 mV at almost full load. Excellent results and well within the industry noise specifications.
|
Efficiency (%)
|
|
|
305W
|
89.02
|
|
600W
|
92.94
|
|
902W
|
91.65
|
|
1330W
|
88.01
|
The Enermax MaxRevo reaches 80 Plus Gold Certification, achieving almost 93% efficiency at around 50% load. It drops to 88 percent at full load, just achieving Gold certification by our results.
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)
|
|
|
305W
|
28.5
|
|
600W
|
29.9
|
|
902W
|
32.6
|
|
1330W
|
34.9
|
The Twister technology is fantastic and it helps ensure that the Enermax MaxRevo 1350W is inaudible most of the time. Only in the last 20% of total load does the fan spin up higher, creating a relatively low noise emission. In most systems this would be drown out by CPU or chassis fans. It reaches a potential maximum noise level of 34.9dBa which is a fantastic result.
|
Temperature (c)
|
||
|
Intake
|
Exhaust
|
|
|
305W
|
35
|
37
|
|
600W
|
38
|
43
|
|
902W
|
43
|
53
|
|
1330W
|
47
|
57
|
The large 140mm Twister fan helps to generate high levels of airflow across the components inside the chassis, with a 10c above ambient intake registered at full load. The fan profile is relatively passive ensuring the noise levels are as low as possible across the load demand.
|
Maximum load
|
Efficiency
|
|
1438W
|
86.1
|
Pushing the PSU above its rated limits generates an efficiency level of around 86.1%. This is not a viable ‘real world’ situation, but its interesting nonetheless.
