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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
• Extech digital sound level meter
• 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 | |
|
120W
|
0.89
|
3.34
|
0.92
|
5.07
|
8.93
|
12.00
|
0.50
|
5.02
|
0.20
|
-12.02
|
|
240W
|
1.62
|
3.34
|
1.64
|
5.07
|
18.43
|
12.00
|
1.00
|
5.02
|
0.20
|
-12.02
|
| 600W |
3.01
|
3.33
|
3.12
|
5.06
|
46.78
|
12.00
|
1.50
|
5.01
|
0.30
|
-12.02
|
| 900W |
4.02
|
3.32
|
4.05
|
5.06
|
70.86
|
12.00
|
2.00
|
5.01
|
0.30
|
-12.03
|
|
1200W
|
5.00
|
3.32
|
5.20
|
5.06
|
94.55
|
12.00
|
2.50
|
5.01
|
0.30
|
-12.03
|
Load regulation is stellar across all the rails, and some of the best results we have seen.
| Cooler Master Masterwatt Maker 1200W MIJ | Maximum Load |
| 1435 Watts |
We managed to get another 235 watts from the power supply before the protection circuitry kicked in. The supply was undamaged and it was ready to fire up again when we dropped the load to a more realistic level. Yes it held steady at 1,400 watts.
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 | |
| 1190W | 4.0 | 3.33 | 3.0 | 5.07 | 88.0 | 11.99 | 0.2 | -12.02 | 0.50 | 5.01 |
| 240W | 19.0 | 3.32 | 22.0 | 5.05 | 2.5 | 12.01 | 0.2 | -12.02 | 0.50 | 5.02 |
The Cooler Master Masterwatt Maker 1200W MIJ delivered great results across the range of input, with little, if any droop across all 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 |
| 100W | 5 | 5 | 5 | 5 |
| 200W | 5 | 5 | 5 | 5 |
| 400W | 5 | 5 | 5 | 5 |
| 600W | 5 | 5 | 5 | 5 |
| 800W | 5 | 5 | 5 | 5 |
| 1000W | 5 | 5 | 10 | 5 |
| 1200W | 5 | 5 | 10 | 5 |
I don't think I have ever seen results quite this good! All minor rails held at 5mV regards of load. The +12V rail peaked at only 10mV at full load. Truly remarkable results
|
Efficiency (%)
|
|
|
100W
|
90.7
|
|
200W
|
94.3
|
|
400W
|
94.9
|
|
600W
|
96.5
|
|
800W
|
95.7
|
| 1000W | 94.8 |
| 1200W | 94.1 |
The overall efficiency results are staggeringly high, peaking at 96.5% at 600W. This drops to 94.1% efficiency at full load, a very impressive result overall.
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)
|
|
|
100W
|
<28.0
|
|
200W
|
<28.0
|
|
400W
|
<28.0
|
|
600W
|
31.5
|
| 800W | 32.7 |
| 1000W | 33.9 |
| 1200W | 35.9 |
The Cooler Master Masterwatt Maker 1200W is a quiet power supply and the fan only really becomes active once it hits around 650 watts load. Under most situations you would be hard pressed to even know it was on, especially as you are likely to be running a single case fan at the same time. The unit does not suffer from any coil whine.
|
Temperature (c)
|
||
|
Intake
|
Exhaust
|
|
|
100W
|
35
|
37
|
|
200W
|
36
|
39
|
|
400W
|
38
|
43
|
|
650W
|
43
|
49
|
|
800W
|
45
|
52
|
| 1000W | 47 | 56 |
| 1200W | 50 | 60 |
The fan doesn't really spin much in the first 500-600 watts load meaning it is basically almost silent. At higher loads the fan spins up although the pitch of the fan is very low so its difficult to pick out against even ambient room noises. Its a very quiet unit, even when powering a 1000 watt load. Remarkable, yet again.
|
Maximum load
|
Efficiency
|
|
1435W
|
93.2
|
Pushing the power supply above its rated limits generates an efficiency level of around 93.2%. Yes just over 93% efficiency when holding a 1400Watt load. Not figures to sneeze at.
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