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Visiontek 800W Modular Power Supply Review

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
100W
1.54
3.38
1.75
5.07
6.66
12.09
0.5
5.02
0.20 -12.07
200W
3.18
3.36
3.41
5.04
13.52
12.02
1.0
5.00
0.30 -12.10
400W
6.13
3.34
7.13
5.02
27.62
11.98
1.5
4.98
0.50 -12.12
600W 9.45 3.32 10.77 5.00 41.33 11.94 2.0 4.96 0.60 -12.15
800W
13.21
3.29
15.05
4.96
55.32
11.91
2.5
4.93
0.80 -12.18

The Visiontek 800W Modular supply delivers good results in the load regulation test across all output. It held within +/-3% of the nominal voltage.

Visiontek 800W Modular Maximum Load
867W

We managed to get the PSU to hit 867W before it would shut down. delivering around 67W more than the rated specifications.

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 3.35 1.0 5.06 60.0 11.90 0.2 -12.09 0.50 5.02
165W 15.0 3.28 18.0 4.97 2.0 12.07 0.2 -12.11 0.50 5.00

Cross loading results fall within parameters, with only a slight dip on the +12V output when loaded with 60A. +3.3V and +5V hold voltage well.

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 15 10 15 15
200W 15 15 15 20
400W 20 20 20 20
600W 25 25 35 25
800W 25 30 50 25

Noise suppression isn’t class leading, although it is well within the rated tolerance levels. +12V peaks at 50 mV under full load.

Efficiency (%)
100W
84.12
200W
86.56
400W
87.88
600W
86.87
800W 84.21

The efficiency results are impressive for an 80 Plus Bronze Certified unit, peaking at just under 88% at 50% load. This drops to around 84% 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 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

Noise (dBA)
100W
29.7
200W
30.8
400W
32.9
600W
34.2
800W 36.6

The power supply is relatively quiet right up until around 600W output when the fan becomes audible, although never that intrusive. At full load the maximum noise level we recorded was 36.6dBa. It isn’t practical to be loading this power supply to 800W on a regular basis however.

Temperature (c)
Intake
Exhaust
100W
36
39
200W
36
41
400W
38
44
600W
39
53
800W
41
55

The temperatures rise to 55c when fully loaded, or 14c above the ambient threshold.

Maximum load
Efficiency
867W
83.4%

For those interested, we measured efficiency when stressing the unit to breaking point. Almost 83.5% at 867W.

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