Seasonic S12 Energy Plus: Efficient Power for Connoisseurs

Power
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October 5, 2006 by Devon Cooke

Product
Seasonic S12 Energy Plus 550 & 650
550W & 650W ATX12V 2.2 Power Supply
Manufacturer
Seasonic Electronics Co., Ltd.
Market Price
550W: US$120~150
650W: US$150~170

Seasonic's power supplies have long held a place of high esteem at SPCR. They have a well deserved reputation for producing some of the quietest, most efficient power supplies on the market. The S12 series needs no introduction to regular readers; it has topped our recommended list since we reviewed the S12-430 in March 2005.

The fundamentals of the S12 series are strong, but that hasn't prevented Seasonic from trying to make them stronger. The S12 Energy Plus is a variant of the S12 that has been tweaked to meet the tough efficiency requirements of the 80 Plus program: 80% efficient at 20%, 50%, and 100% load. While many high end power supplies have peak efficiency above 80%, not many are able to sustain that efficiency across a wide range of loads. To date, we know of only two other retail power supplies that can: The FSP Zen, and the SilverStone Element Plus. Counting both models of the Energy Plus, that makes a total of four retail power supplies approved by 80 Plus. That's a pretty exclusive club, folks.

The Energy Plus models are derived from the 80 Plus certified SS-400HT that we looked at last year — which is a lower power version of the S12 500W and 600W models. This was the first 80 Plus certified power supply we examined, intended for system integrators and not widely available.

There is some question about why a retail power supply should bear the 80 Plus logo. The 80 Plus rebates are available only to system integrators who use approved power supplies in complete PCs. It is one reason why there are so few retail 80 Plus models on the market. This suggests that an 80 Plus mark for a retail power supply is primarily useful for marketing purposes. The 80 Plus mark is becoming the Good Housekeeping Seal of Approval for energy conscious computer consumers. That Seasonic would make and market such a product is no great surprise. They have been pioneers in pushing the efficiency envelope, and after some five years of effort in the retail marketplace, are well-recognized as a top quality brand in the geek community. A mark such as 80 Plus helps to push their hard-earned reputation onto a larger audience. So from a marketing point of view, it makes perfect sense.

Seasonic's marketing literature makes much of the "Dual Forward Converter" design that allows such high efficiency, but the official 80 Plus logo on the box matters more than how they managed to get it. Something similar could be said about the "Dual Magnetic Amplifier" circuit that allows the Energy Plus to regulate the +12V lines to a tight 3%. It's a nice feature to be sure, but it's the tight regulation that counts, not the way it's achieved.

Seasonic has always catered to the high end, but, if it can deliver what it promises, the S12 Energy Plus may create a new product category that is above even the original S12. This is a power supply for connoisseurs. While the extra efficiency and tighter voltage regulation certainly reflect a better underlying design, the practical benefits of these improvements are likely to be pretty insubstantial except for users who push their systems to extremes.


The box displays the 80 Plus logo prominently.


Floppy connectors come on their own adapter since they are rarely needed.

FEATURE HIGHLIGHTS

Feature Highlights of the Seasonic S12 Energy Plus (from Seasonic's web site)
FEATURE & BRIEF COMMENT
Dual Magnetic Amplifiers [Mag-Amp]
Cross regulation tolerance on +12V lines are improved from standard 5% to 3% for optimized stability.
Generally a good thing, especially in high stress systems.
Double Forward Converter Design
Advanced topology for the highest efficiency.
High efficiency translates into more than energy savings. It also cuts the heat output and makes lower noise levels possible.
Multiple +12V Outputs
Enhanced +12V current capability broadens utilization possibilities.
Rumor has it that the four +12V lines are not so independent...
High Reliable Aluminum Electrolytic Capacitors
Top quality components increase product life & reliability.
Reliable components may be the most important feature in a power supply.
Super High Efficiency [up to 88%]
Optimal solution for low energy consumption, noise & heat.
No power supply we've ever tested has managed 88% efficiency in our admittedly tough test rig. Perhaps at 240VAC input and low operating temperature?
Active Power Factor Correction [99% PF]
Reduces line loss & power distortion.
Standard on Seasonics for a long time, and increasingly common on other high end units.
Smart and Silent Fan Control [S2FC]
Smart thermal control to balance noise and cooling.
The same excellent controller that made Seasonic's past models so quiet.
12cm Ball Bearing Cooling Fan
Increase airflow and lifetime, reduce rotation speed and noise.
Most power supplies use 12cm fans these days.
Soft-Mounting Rubber Cushions
Reduces fan rotation & vibration noise.
Soft mounting is generally good for noise quality.
Ultra Ventilation [Honey Comb Structure]
Doubles the airflow & lifespan with half the RPM & noise.
A feature since the Seasonic Super Tornado two generations ago.
All in One DC Cabling Design
Supports PC, IPC, workstation, server, & dual CPU systems.
ATX12V & EPS12V compliant. Dual CPU and/or GPU systems are the only systems that are likely to demand anywhere near the rated capacity.
Universal Video Card Support
Supports all multiple PCI-E video cards technologies.
Longhand for dual PCIe connectors.
Patented Easy Swap Connector
Unplug the connectors easily & quickly.
Useful... but less so now that IDE drives have almost disappeared.
Universal AC Input [Full Range]
Plug & run safely anywhere in the world.
Nice. Normal in retail Seasonic PSUs for several years.
3 Year Warranty
Our Commitments to superior quality.
Hopefully unnecessary, but nice to have.

SPECIFICATIONS

OUTPUT SPECIFICATIONS: Seasonic S12 Energy Plus 550
AC Input
100~240VAC 50/60Hz
AC Input Current
10A
DC Output
+3.3V
+5V
+12V1
+12V2
+12V3
+12V4
-12V
+5VSB
Maximum Output Current
24A
30A
18A
18A
18A
18A
0.8A
3.0A

Maximum Combined

170W
492W (41A)
9.6W
15.0W
550W

OUTPUT SPECIFICATIONS: Seasonic S12 Energy Plus 650
AC Input
100~240VAC 50/60Hz
AC Input Current
12A
DC Output
+3.3V
+5V
+12V1
+12V2
+12V3
+12V4
-12V
+5VSB
Maximum Output Current
24A
30A
18A
18A
18A
18A
0.8A
3.0A

Maximum Combined

170W
624W (52A)
9.6W
15.0W
650W

The specifications for the two Energy Plus models are identical except for the combined load on the +12V rail, just as it should be. In real use, this is really the only number that matters; real world conditions dictate that the vast majority of power is pulled from the +12V lines.

The fact that increased capacity only shows up as combined current on the +12V lines raises an interesting question: Just how separate are the four +12V lines. Some knowledgeable members of the SPCR forums have done some digging, and discovered that in reality there may only be one or two lines. The discussion is specifically about Seasonic's new M12 line and its rebranded twin from Corsair, but given its similarity to the Energy Plus series, many of the points apply equally to both series. Things get quite technical, but the summary is this:

  • Lines are only "separate" insofar as they have separate current limiters on each line. The original source is often (but not always) the same.
  • The purpose of having multiple rails is to limit the total VA from one line to 240VA, which means a limit of 240VA ÷ 12V = 20A on each line.
  • The circuit board does not identify contact points for either +12V3 or +12V4.
  • One user has reportedly been able to draw as much as 30~40A from a single cable set, which should certainly have tripped a current limiter if the rails were actually as specified. We were able to perform a similar test on the Energy Plus.

Only Seasonic knows for sure, but it seems quite likely that the four "separate" +12V lines are not separate at all, but are just there to satisfy the standard-setters at ATX12V and EPS12V. The practical consequences of having a single +12V rail are actually more positive than negative. While a small degree of safety is lost by isolating the rails, the convenience of not having to watch where each peripheral is plugged in outweighs the loss.



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