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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
• 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 | |
|
75W
|
1.23
|
3.33
|
1.19
|
5.07
|
4.95
|
12.22
|
0.50
|
5.06
|
0.20
|
-12.05
|
|
150W
|
2.17
|
3.31
|
2.83
|
5.04
|
10.07
|
12.19
|
1.00
|
5.04
|
0.30
|
-12.05
|
|
375W
|
6.15
|
3.27
|
6.05
|
5.02
|
26.15
|
12.15
|
1.50
|
5.02
|
0.50
|
-12.06
|
| 565W |
10.31
|
3.24
|
10.86
|
4.97
|
38.34
|
12.09
|
2.00
|
5.00 |
0.60
|
-12.07
|
|
750W
|
10.72
|
3.21
|
13.84
|
4.92
|
53.59
|
12.02
|
3.00
|
4.98
|
0.80
|
-12.08
|
Regulation is good, although we noticed the +3.3V output dropped to just 3.21V at full load. The other rails hold well throughout the range of power.
| Thermaltake Smart M Series 750W | Maximum Load |
| 819W |
We managed to reach around 819W before the unit would shut down gracefully, after the protection kicked in.
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 | |
| 734W | 1.0 | 3.34 | 1.0 | 5.03 | 60.0 | 11.96 | 0.2 | -12.05 | 0.50 | 5.03 |
| 154W | 15.0 | 3.28 | 15.0 | 4.95 | 2.0 | 12.11 | 0.2 | -12.05 | 0.50 | 4.99 |
Fluctuation is held safely within the rated parameters, even when we load the 12V line with 60A.
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 | 10 | 10 | 10 | 10 |
| 150W | 10 | 15 | 15 | 10 |
| 375W | 15 | 15 | 20 | 10 |
| 565W | 15 | 20 | 25 | 15 |
| 750W | 20 | 25 | 35 | 15 |
Ripple results are very good on all the rails, holding well within the tolerance guidelines. The 12V+ output is particularly impressive, peaking at 35 mV.
|
Efficiency (%)
|
|
|
75W
|
84.28
|
|
150W
|
87.64
|
|
375W
|
88.89
|
|
565W
|
87.33
|
|
750W
|
86.44
|
The Thermaltake power supply is efficient for an 80 Plus Bronze rated unit, peaking at just under 89 percent efficency at 50 percent 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 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 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
|
30.2
|
|
375W
|
33.3
|
|
565W
|
36.3
|
| 750W | 37.8 |
The power supply is relatively quiet until around 350W of load when the fan starts to spin up steadily. At full load the noise levels are clearly audible, and slightly intrusive. Thermaltake appear to have opted for an aggressive fan profile for this unit.
|
Temperature (c)
|
||
|
Intake
|
Exhaust
|
|
|
75W
|
36
|
40
|
|
150W
|
38
|
43
|
|
375W
|
39
|
47
|
|
565W
|
45
|
52
|
|
750W
|
47
|
56
|
Exhaust temperatures are quite good, reaching a maximum delta of 9c above intake at full load. The fan is very active in the upper half of power delivery however and we feel Thermaltake could have tweaked this a little more. It seems slightly too aggressive for my own personal tastes.
|
Maximum load
|
Efficiency
|
|
819W
|
85.1
|
For those interested, we measured efficiency when stressing the unit to breaking point. 85.1 percent efficiency at 819W … hardly practical, but interesting regardless.
