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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. Over the coming months this configuration is likely to be adjusted further and fine tuned. Ambient room temperatures are kept to a ‘real world’ realistic condition of 23c with air conditioning.
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
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DC Output Load Regulation
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||||||||||
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Combined DC Load |
+3.3V
|
+5V
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+12V
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+5VSB
|
-12V | |||||
|
A
|
V
|
A
|
V
|
A
|
V
|
A
|
V
|
A | V | |
|
100W
|
1.58
|
3.34
|
1.77
|
5.04
|
6.64
|
12.12
|
0.50
|
5.02
|
0.20 | -12.12 |
|
225W
|
3.70
|
3.32
|
3.83
|
5.03
|
15.55
|
12.09
|
1.00
|
5.02
|
0.20 | -12.12 |
|
450W
|
7.51
|
3.31
|
8.37
|
5.02
|
30.68
|
12.08
|
1.50
|
5.01
|
0.30 | -12.13 |
| 675W | 11.31 | 3.30 | 12.39 | 5.01 | 47.46 | 12.05 | 2.00 | 5.00 | 0.50 | -12.15 |
|
850W
|
1.31
|
3.29
|
1.10
|
5.00
|
70.46
|
12.00
|
0.50
|
4.98
|
0.20 | -12.15 |
The TX850 delivered excellent load regulation on all output channels across a wide range of loads. These are exceptional results and the +3.3V and 5V rails remained firmly within +/-2% of the nominal voltage instead of the recommended +/-5% and the +12V rail held within +/- 1%, even when it was forced to deliver over 70 Amps.
| Corsair TX850 | Maximum Load |
| 925W |
We managed to get the PSU to hit 925W before it would shut down. delivering around 75W more than the rated specifications. It would run at 920W for quite a while.
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 | |
| 760W | 1.0 | 3.26 | 1.0 | 5.02 | 65.0 | 11.97 | 0.2 | -12.07 | 0.50 | 5.00 |
| 165W | 15.0 | 3.30 | 18.0 | 4.97 | 2.0 | 11.99 | 0.2 | -12.06 | 0.50 | 4.97 |
Again, these are very good results with fluctuation held safely within the rated parameters, even when loading the unit with 65A on the 12V.
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.
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ATX12V Ver 2.2 Noise/Ripple Tolerance
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|
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Output
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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 Corsair unit complied with the ATX standard.
| AC Ripple (mV p-p) | ||||
| DC Load | +3.3V | +5V | +12V | 5VSB |
| 100W | 5 | 10 | 20 | 10 |
| 225W | 10 | 15 | 20 | 15 |
| 450W | 10 | 15 | 30 | 15 |
| 675W | 15 | 20 | 40 | 15 |
| 850W | 15 | 20 | 45 | 20 |
Ripple results are very impressive, across the board. The 12V rail registered around 45 mV with our equipment, which is well within the Tolerance guidelines.
|
Efficiency (%)
|
|
|
100W
|
86.34
|
|
225W
|
87.34
|
|
450W
|
88.85
|
|
675W
|
87.78
|
| 850W | 86.03 |
For a 80 Plus Bronze specified unit, these results are very strong, showing a maximum efficiency rating, just shy of 89%. At maximum load this drops to around 86%, which is again, a great result.
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 Corsair 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 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
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Noise (dBA)
|
|
|
100W
|
27.7
|
|
225W
|
28.3
|
|
450W
|
30.7
|
|
675W
|
35.8
|
| 850W | 40.3 |
Noise levels are low, with the system only becoming audible in the final 25% of output. Under 500W load it would be hard to know the unit was actually on.
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Temperature (c)
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||
|
Intake
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Exhaust
|
|
|
100W
|
35
|
36
|
|
225W
|
36
|
38
|
|
450W
|
38
|
44
|
|
675W
|
42
|
48
|
|
850W
|
44
|
52
|
Exhaust temperatures are excellent, rising to a 8c above ambient result at full load. This 140mm fan works hard in the last 15% of output, but temperatures are well maintained. Corsair could have actually relaxed the fan profile a little if they wanted.
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Maximum load
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Efficiency
|
|
925W
|
84.34%
|
For those interested, we measured efficiency when stressing the unit to breaking point. Over 84% at 925W … hardly practical, but interesting regardless.
