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Corsair HX1200i ’80 Plus Platinum’ 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 – 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

DC Output Load Regulation

Combined

DC Load

+3.3V
+5V
+12V
+5VSB
-12V
A
V
A
V
A
V
A
V
A V
100W
1.55
3.34
1.75
5.05
6.65
12.22
0.50
5.02
0.20
-12.07
200W
3.13
3.34
3.50
5.05
13.50
12.18
1.00
5.02
0.20
-12.07
400W
6.40
3.33
7.05
5.04
27.50
12.14
1.50
5.02
0.30
-12.07
600W
9.80
3.33
10.77
5.04
41.70
12.12
2.00
5.01
0.30
-12.07
800W
13.25
3.33
14.55
5.04
56.40
12.08
2.50
5.01
0.50
-12.08
1000W 16.55 3.32 15.75 5.03 71.40 12.06 3.00 5.01 0.60 -12.08
1200W 22.01 3.32 22.01 5.00 85.00 12.02 3.60 5.00 0.80 -12.08

Load regulation is very good indeed, holding within 2%.

Corsair HX1200i Maximum Load
1344 Watts

We managed to get another 144 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.

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 3.34 3.0 5.05 88.0 12.00 0.2 -12.04 0.50 5.01
240W 19.0 3.33 22.0 4.99 2.5 12.15 0.2 -12.03 0.50 5.00

The Corsair HX1200i power supply delivered a great set of results in the demanding Cross load test, as shown above.

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 10 10 15 5
200W 15 10 15 10
400W 15 10 15 10
600W 15 10 20 10
800W 15 10 25 15
1000W 15 15 30 15
1200W 15 15 30 20

Fantastic results – all rails hold well within the industry rated tolerance levels.

Efficiency (%)
100W
85.8
200W
88.9
400W
93.0
600W
94.1
800W
93.8
1000W 92.6
1200W 92.2

The overall efficiency results are excellent, peaking at 94.1% at 600W. This drops to 92.4% 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 32.3
1000W 33.7
1200W 35.6

The Corsair HX1200i '80 Plus Platinum' Power Supply is a very quiet power supply and the fan was inactive below 500 watts. When the load rises, the fan starts to rotate, although noise levels are never a concern.

Even when delivering 1000 watts, the fan is not intrusive, although audible. Under 500 watts load, the unit is silent – our test equipment is limited to accurate results at no less than 28dBa.

Temperature (c)
Intake
Exhaust
100W
35
37
200W
35
38
400W
37
43
650W
43
48
800W
45
54
1000W 47 57
1200W 50 63

Temperatures are well controlled as the fan spins actively once load hits 850W load and beyond.

Maximum load
Efficiency
1344W
91.7

Pushing the power supply above its rated limits generates an efficiency level of around 91.7%. This is not a viable ‘real world’ situation, but its interesting nonetheless.

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