Seasonic G Series 550W Power Supply review

1. Introduction2. Seasonic G Series 550W Power Supply (Bundle & Cables)3. Seasonic G Series 550W Power Supply (External)4. Seasonic G Series 550W Power Supply (Internal)5. Seasonic G Series 550W Power Supply (Super High Res Gallery)6. Testing Methodology & Results7. Closing Thoughts8. View All Pages

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
• SkyTronic DSL 2 Digital Sound Level Meter (6-130dBa)
• Digital oscilloscope (20M S/s with 12 Bit ADC)
• Variable Autotransformer, 1.4 KVA

We combine all +12V output for the results below.

DC Output Load Regulation
Combined DC Load	+3.3V		+5V		+12V		+5VSB
	A	V	A	V	A	V	A	V
110W	1.18	3.36	1.18	5.06	8.02	12.11	0.50	5.06
220W	2.07	3.35	2.07	5.05	16.13	12.08	0.50	5.03
340W	3.04	3.35	3.05	5.03	25.12	12.06	1.00	5.02
445W	4.12	3.33	4.06	5.01	33.23	12.05	1.50	5.01
550W	5.13	3.31	5.03	4.99	41.03	12.03	2.50	5.00

Seasonic G Series 550W Power Supply	Maximum Load
	651W

Load regulation is strong across the output range. The power supply delivered 651watts of power before it would shut down, safely. This is an excellent result and follows the Seasonic strategy of over-specifying the unit for the wattage rating.

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
493W	1.0	3.36	1.0	5.06	40.5	11.98	0.2	-12.05	0.50	5.02
153W	15.0	3.29	15.0	4.99	2.0	12.09	0.2	-12.11	0.50	5.03

The power supply is well designed and it coped well with our demanding Cross Load tests. When hit with 40A on the +12V rail it held close to a reference result at 11.98V. Other rails delivered good results.

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
110W	10	10	20	10
220W	10	15	25	10
340W	15	15	30	15
445W	20	20	45	20
550W	25	25	55	20

Noise suppression is good, peaking at 55 mV at full load on the +12V output. All other rails held to 20mV-25mV when loaded.

Efficiency (%)
110W	87.11
220W	89.77
340W	91.45
445W	90.76
550W	88.88

Efficiency is excellent, peaking over 91 percent at around 50 percent load. At full load this drops to just below 89 percent efficiency.

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. That said, measuring lower than 28dBa proves very difficult, unless in strict laboratory conditions.

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)
110W	28.0
220W	29.5
340W	31.7
445W	32.7
550W	33.2

The fan maintains a low level of noise, even when tasked with 450W power. This rises in the last 15% of power output, but the results are still impressive.

Temperature (c)
	Intake	Exhaust
110W	36	38
220W	38	42
340W	41	47
445W	44	52
550W	46	56

The efficiency of the unit allows the large fan to spin very slowly at all times. Temperatures rise to a 10c above ambient intake at full load.

Maximum load	Efficiency
651W	87.1

Pushing the PSU above its rated limits generates an efficiency level of around 87.1%. This is not a viable ‘real world’ situation, but its interesting nonetheless.

Become a Patron!