Seasonic Platinum Series 860W - Platinum without the Fuss
by Martin Kaffei on February 24, 2012 12:00 AM ESTInternals and Electronics
As our research has shown the Platinum 860W is very close to the 80 Plus Gold X-1000 and X-1250. This is not surprising, since the earlier model PSUs already had a considerably higher efficiency than the requirements for 80 Plus Gold certification. Seasonic employs a full-bridge resonant converter that utilizes the transformer in full. You don't need any diodes for commutation during turn-off. As a result this circuit design is predestined for higher power ratings.
The current and voltage pulses of the resonant circuit run nearly sinusoidal and the transistors turn on at zero voltage. Together with the low resistance on the drain-source path the power dissipation is much lower during turn-on, turn-off, and the saturation of those transistors. Accordingly the heatsinks are much smaller now. However, differences between the larger models are the "weaker" MOSFETs and the missing third primary capacitor (which you can see a silkscreened space for in the above image).
There are some minor changes from the previous X-series. One of them is connected with the resonant circuit itself. Two conductions of the IC CM6901 (on a small PCB) lead to a small inductor, which is located between the resonant capacitor, the resonant coil, and the small "auxiliary coil" to relieve the main transformer. With this the current is measured in the resonant circuit to improve regulation. A second winding is connected to the main PCB and the magnetic flux in the core passes through the regulation winding.
We found out that there are two +12V sources at the transformer with two large ground planes. The PS232F offers over current protection for +3.3V, +5V and +12V (up to four outputs). This is the second sign that this PSU has multiple +12V outputs. The pins for the over current measurements are connected to +12V without exception. Seasonic does not officially favor a single output, but many ODM customers such as Corsair do, which might be the reason for the "single rail" rating on their label. Nevertheless it is basically a multiple 12V rail design.
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Exodite - Friday, February 24, 2012 - link
Many thanks for an excellent review, the technical details is what keeps bringing me back to AnandTech.I'm currently using a Seasonic SS460-FL myself, the 460W X-Series fanless model, and it's been all but perfect. The only issue is what I'd consider the high electrical noise, something the unit shared with the M12 2 800W model it replaced, but it's tolerable in a suitably isolated case.
Before I scare anyone off by that comment I should note that I'm extremely picky about noise, to the point that I'm running the two 140m fans on my CPU cooler (a Noctua NH-C14) at 750RPM because anything above that is too loud to my taste.
Like many other posters here I will continue buying Seasonic PSUs for the foreseeable future due to their impeccable quality and performance. Skimping on what's essentially the heart and circulatory system of your computer always struck me as ill-advised.
Martin Kaffei - Saturday, February 25, 2012 - link
Some fanless PSUs had a noisy PFC choke, the source might be magnetostriction. Often a magnetic field is not constant because current changes or other inductivities trouble the choke. This deforms the materials and makes such noises.Since there is no fan noise you can hear the electrical noise much better. In truth the electrical noises are at the same level as always.
dj christian - Thursday, March 1, 2012 - link
So you'r running only the CPU-fans? Are the rest passive?kensiko - Friday, February 24, 2012 - link
Good but did you review the Kingwin (Super flower) ? I saw some reviews and everybody agrees that the components are of high quality.I did buy a Kingwin and I class it as good as Seasonic (I owned a Seasonic before)
kensiko - Friday, February 24, 2012 - link
I'm talking about the Lazer Platinum Series for sure.Beenthere - Friday, February 24, 2012 - link
IME few reviewers consider Super Flower/Kingwin in the same class as Seasonic.palindrome - Friday, February 24, 2012 - link
You must not read PSU reviews then...Breit - Friday, February 24, 2012 - link
You say that this 860W model is the best PSU SeaSonic has to offer, but what about the 1000W unit SS-1000XP released in Q4-2011? I thought it is actually the same PSU with higher ratings?! It even has the 80 PLUS Platinum label and also has exceptionally good efficiency over a wide range of loads well above 90% from 20% load to 100% load. I think it should at least get mentioned in the article. The Gold-units from SeaSonic you are referring to were released in 2010 i think.Besides that thanks for this very good article, its always a pleasure reading anadtech.
Martin Kaffei - Friday, February 24, 2012 - link
It is fair to say Seasonic made the best current series, but I didn't test the (original) 1KW version yet.Conscript - Friday, February 24, 2012 - link
You talk about how great they are, but no pics?