Seasonic S12D 850W (Page 3 of 4) | Reports

Page 3 - Physical Look - Inside

As always, we opened up our Seasonic S12D 850W power supply to take a detailed look at what's going on inside. Please note that doing this at home will void your warranty, thanks to the virginity warranty seal that Seasonic applied over one of the attachment screws. But for the benefit of you, we cracked ours open so you don't need to, haha.

Initially, I was very tempted to replace the internal 120mm power supply fan with my Noctua NF-P12 upon the opening of the Seasonic S12D. However, I was pleasantly surprised when I discovered that the fan is actually a San Ace (Sanyo Denki) unit! While previous Seasonic products proved to be extremely quiet in every day operation from my experience, the company usually implements ADDA fans. The way Seasonic uses them is optimal, but it is not the nature of the fans to provide superior cooling to noise ratio. San Ace fans are highly regarded among certain enthusiast circles for its excellent performance and airflow; that's not to mention that San Ace products are actually particularly hard to find at North America retailers. That said, if you ever decide to modify your S12D's cooling, the fan is actually connected to the main unit via a 2-pin connection -- it's an easy swap shall the fan die one day, since it is not soldered in.

An overhead view of the Seasonic S12D 850W's internals show a very clean design, with components well placed for optimal cooling and reduced heat congestion. Two 'toothed' aluminum heatsinks are used for increased airflow, without reducing cooling capabilities. Seasonic has an excellent reputation for superior build quality, and it appears that the S12D is no exception, as seen in the photo above. But it's the details that count, right? Don't worry, I'm not going to waste any of your time -- let's take a closer look.

The transient filter stage is the first input stage of a computer power supply, so we'll take a look at that first. As shown in the photo above, components are placed behind a transparent plastic wall for additional protection, since the shell is made of metal, after all -- and some of these components are placed very close to the edge. Seasonic certainly did not cheap out in this area -- it has four ferrite coils, two metalized polyester X-capacitors, four ceramic Y-capacitors, and one metal oxide varistor. This is very impressive, as there's practically twice as many of each component as you would find in a standard quality power supply unit!

Two separate active PFC circuits are featured on the Seasonic S12D 850W; each circuit is independently fed by one of two GBU806 8.0A glass passivated bridge rectifiers. At 115V, you can theoretically pull up to 920W from each bridge rectifier at 100% efficiency -- of course, this is limited by the fact that it is not 100% efficient, and also neglects the fact that not every component in the system are able to keep up. Two Fairchild Semiconductor FQP13N50C power MOFSET transistors are used on each active PFC circuit for a total of four on the Seasonic S12D 850W power supply. Each MOFSET can deliver up to 8A at 100 degrees Celsius. These transistors present a maximum resistance of 0.48 ohms when turned on; with a typical resistance of 0.39 ohms. This on characteristic is called Static Drain-Source On-Resistance, or commonly abbreviated as RDS(on). The more efficient the component is, the lower the RDS(on) value, since it wastes less power with lower resistance.

The traditional two-transistor forward configuration incorporates a couple Infineon SPP24N60C3 Cool MOS power transistors. Rated continuous drain current according to the manufacturer at Tc = 25c, the current Id = 24.3A. When Tc is increased to 100c, the Id drops to 15.4A. Pulsed drain current tp, limited by Tjmax, permits up to 72.9A in pulse mode (Id puls).

Champion Component's CM6802 "green" active PFC/PWM combination controller is used on the Seasonic S12D.

Two Chemi-Con Japanese made capacitors are connected in parallel. Reviews of Seasonic's S12D 750W around the web indicates that our 850W's lower brethren uses one 330µF x 400V and one 390µF x 400V capacitor, but our 850W version incorporates two 390µF x 400V Chemi-Con capacitors for a total capacitance equivalence of a single 780µF x 400V capacitor. These units are rated at 105c; whereas typical power supplies usually use 85c rated capacitors.

SBR40S45CT rectifiers are responsible for the rectification process. As with modern high efficiency power supplies, all rectifiers produces the +12V out -- while the +5V and +3.3V outputs are generated from the +12V output using a DC to DC converter within the power supply unit. The SBR40S45CT's rated average rectified output current is 20A per leg, or 40A total. The forward voltage drop at If = 20A and Tj = 125c has a maximum of only 0.50V, with a typical of 0.47V. At Tj = 25c and If = 20A, the maximum forward voltage drop is listed at 0.55V.

The DC-to-DC converter is has one ANPEC SPW7073 synchronous buck PWM controller for each of the +3.3V and +5V outputs. The APM2556N MOFSETs has a RDS(on) value of only 0.0072 ohms. A Silicon Touch PS223 4-channel monitoring IC provides over current protection, over voltage protection, and under voltage protection on the Seasonic S12D 850W power supply.

Overall, the internal build quality of Seasonic's S12D 850W power supply is excellent -- it's actually quite overbuilt for what it does. Components are arranged beautifully for optimal cooling; and each solder joint is completed cleanly. We are very impressed by the design and execution of Seasonic's S12D power supply.

As was very obviously demonstrated above, Jonathan is an epic win at Electrical Engineering. Which might help to explain why he's an epic fail with "the girl", haha. - Editor
Basically, we are saying that the chc's engineering skills are inversely proportional to his getting "the girl" skills. - Editor 2

Page Index
1. Introduction, Packaging, Specifications
2. Physical Look - Outside
3. Physical Look - Inside
4. Minor Tests and Conclusion