Seasonic X-Series 650 W Power Supply Review
By Gabriel Torres on October 15, 2009
Seasonic has just released their 80 Plus Gold power supply line-up, X-Series, which promises 90% efficiency. Let’s take a look at the 650 W model.
As you may be aware, Seasonic is a traditional OEM manufacturer, being the real manufacturer behind units from brands like Antec, Corsair and Arctic Cooling (not all power supplies from these brands are manufactured by Seasonic, though). One annoying thing about Seasonic is that they have three websites, http://www.seasonic.com, http://www.seasonic.com.tw and http://www.seasonicusa.com, but retail products like the reviewed power supply can only be found on the later. In our opinion this makes no sense and only makes it difficult to consumers to find out more about their products.
X-Series 650 W isn’t a long power supply, being 6 19/64” (160 mm) deep, using a 120 mm fan on its bottom and featuring active PFC, of course. The fan used on this power supply is from a Japanese brand (Sanyo Denki, even though it was manufactured in the Philippines – welcome to the globalized world) and only rotates when needed. When this power supply is operating at low load and thus relatively cold, the fan does not spin, making this power supply to emit zero acoustic noise under this scenario.
X-series models present a fully modular cabling system, where even the main motherboard cable is modular.
This power supply comes with the following cables:
The modular cabling system has five connectors for SATA/peripheral cables, so from the six SATA/peripheral cables that come with the power supply, only five can be used at the same time.
All cables measure 22” (56 cm) from the power supply to the first connector on the cable and on the cables with more than one connector there is 6” (15 cm) between connectors.
All cables use 18 AWG wires, which is the correct gauge to be used.
The number of cables is more than perfect for a 650 W product.
Now let’s take an in-depth look inside this power supply.
We decided to disassemble this power supply to see what it looks like inside, how it is designed, and what components are used. Please read our Anatomy of Switching Power Supplies tutorial to understand how a power supply works and to compare this power supply to others.
This page will be an overview, and then in the following pages we will discuss in detail the quality and ratings of the components used. Two things immediately caught our attention. First, all capacitors used on this power supply are Japanese, with the components used on the secondary being solid. The second thing was the design used. This power supply uses a DC-DC converter on the secondary, meaning that this is basically a +12 V power supply that gets the +5 V and +3.3 V outputs by installing additional switching power supplies on the +12 V output. This design is being used by several power supplies and so far has proving to be the best choice for building high-efficiency units. What is different on this product is that instead of the DC-DC converter being installed on a daughterboard on the secondary, it was installed on the modular cabling system printed circuit board. A nice and really smart choice, as it drastically reduces the number of cables necessary to connect the modular cabling system to the main printed circuit board.
As we have mentioned in other articles and reviews, the first place we look when opening a power supply for a hint about its quality, is its filtering stage. The recommended components for this stage are two ferrite coils, two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor), and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components, usually removing the MOV and the first coil.
The AC power connector shown in Figure 7 is in fact a complete filtering circuit, and it has all the minimum required components. You can also see a presence of a relay, in charge of shutting down the power supply right on its input when certain protections kick in.
In the next page we will have a more detailed discussion about the components used in the Seasonic X-Series 650 W.
On this page we will take an in-depth look at the primary stage of Seasonic X-Series 650 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.
This power supply uses two GBJ1506 rectifying bridges in its primary connected in parallel with a heatsink installed between them. Each bridge supports up to 15 A at 100° C, so in theory, you would be able to pull up to 3,450 W from the power grid; assuming 80% efficiency, the bridges would allow this unit to deliver up to 2,760 W without burning them. Talk about overspecification! Of course, we are only talking about these components, and the real limit will depend on all the other components in this power supply.
Three SPA20N60C3 power MOSFETs are used on the active PFC circuit, each one capable of delivering up to 20.7 A at 25° C or 13.1 A at 100° C in continuous mode (note the difference temperature makes) or up to 62.1 A at 25° C in pulse mode. These transistors present a maximum resistance of 190 mΩ when turned on, a characteristic called RDS(on). This number indicates the amount of power that is wasted, so the lower this number the better, as less power will be wasted thus increasing efficiency.
This power supply uses two electrolytic capacitors to filter the output from the active PFC circuit. The use of more than one capacitor here has absolute nothing to do with the “quality” of the power supply, as laypersons may assume (including people without the proper background in electronics doing power supply reviews around the web). Instead of using one big capacitor, manufacturers may choose to use two or more smaller components that will give the same total capacitance, in order to better accommodate space on the printed circuit board, as two or more capacitors with small capacitance are physically smaller than one capacitor with the same total capacitance. X-series 650 W uses two 330 µF x 400 V capacitors connected in parallel; this is the equivalent of one 660 µF x 400 V capacitor.
These capacitors are Japanese, from Chemi-Con and are labeled at 105° C. This is good for two reasons, first, Japanese capacitors do not leak; and second, usually manufacturers use 85° C capacitors here, so it is good to see a manufacturer using a capacitor with a higher temperature rating.
The active PFC circuit is controlled by an NCP1654 integrated circuit.
In the switching section, two STW20NM50FD power MOSFET transistors are used. Each transistor supports up to 20 A at 25° C or 14 A at 100° C (note the difference temperature makes) or 80 A in pulse mode at 25° C, presenting an RDS(on) of 220 mΩ.
The switching transistors are connected using a design called “LLC resonant,” also known as a series parallel resonant converter, being controlled by a CM6901 integrated circuit, which operates under PWM (Pulse Width Modulation) mode when the power supply is operating under light load but under FM (Frequency Modulation) mode under other loads.
Now let’s take a look at the secondary of this power supply.
This power supply uses a DC-DC design on the secondary. This means that this power supply is basically a +12 V unit, with +5 V and +3.3 V outputs being produced by two smaller power supplies connected to the main +12 V output. Most high-efficiency power supplies use this design nowadays, which is proving to be a winner.
The main +12 V power supply uses a synchronous design, i.e., instead of using Schottky diodes it uses MOSFETs to perform the rectification. Four IPD036N04L MOSFETs are used, each one being able to handle up to 90 A at 25° C or up to 87 A at 100° C in continuous mode, or up to 400 A at 25° C in pulse mode, with an RDS(on) of only 3.6 mΩ. Seasonic decided to use the power supply housing as a heatsink for these transistors.
What is unique about this power supply is that the DC-DC converters for the +5 V and +3.3 V outputs are not located on small daughterboards attached to the secondary. Instead, Seasonic opted in putting this circuit on the printed circuit board from the modular cabling system. This drastically reduced the number of wires connecting the main printed circuit to the modular cabling system, since only the +12 V wires are needed (plus thin +12 V, +5 V and +3.3 V wires for the monitoring circuit). Also there is no need for thick or several +12 V wires because half of the modular cabling system – the connectors that carry only +12 V outputs and are connected to the most power-hungry devices like the CPU and video cards – is installed directly on the main printed circuit board.
The +5 V and +3.3 V converters are controlled by an APW7159 integrated circuit, with each output being driven by two APM2510N (maximum of 50 A at 25° C or 35 A at 100° C, RDS(on) of only 8.5 mΩ) and two APM2556N (maximum of 160 A at 25° C or 90 A at 100° C, RDS(on) of only 4.5 mΩ) MOSFETs.
This power supply uses a PS223 monitoring integrated circuit, which is in charge of the power supply protections, like OCP (over current protection), over voltage protection (OVP), under voltage protection (UVP) and over temperature protection (OTP, not implemented on this unit).
In Figure 18, you can see the power supply label containing all the power specs.
This power supply uses a single-rail design, so there is not much to talk about here.Now let’s see if this power supply can really deliver 650 W.
We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology.
First we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under each load. In the table below we list the load patterns we used and the results for each load.
If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (e.g., the +5 V output working at +5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. On the “Total” row we are using the real amount of power being delivered, as measured by our load tester.
The +12V1 and +12V2 inputs listed below are the two +12 V independent inputs from our load tester and since this power supply has a single-rail design they were both connected to the power supply single +12 V rail.
5 A (60 W)
10 A (120 W)
15 A (180 W)
20 A (240 W)
24 A (288 W)
5 A (60 W)
10 A (120 W)
14 A (168 W)
19 A (240 W)
24 A (288 W)
1 A (5 W)
2 A (10 W)
4 A (20 W)
6 A (30 W)
8 A (40 W)
1 A (3.3 W)
2 A (6.6 W)
4 A (13.2 W)
6 A (19.8 W)
8 A (26.4 W)
1 A (5 W)
1 A (5 W)
1.5 A (7.5 W)
2 A (10 W)
2.5 A (12.5 W)
0.5 A (6 W)
0.5 A (6 W)
0.5 A (6 W)
0.5 A (6 W)
0.5 A (6 W)
% Max Load
Ripple and Noise
What a power supply! What a power supply! You will get efficiency of at least 90% if you pull between 40% and 60% from its labeled load (between 260 W and 390 W). At 80% load (520 W) efficiency was still extremely high at 89%. At light load (20%, i.e., 130 W) efficiency dropped to 88%, still a very high value. The lowest efficiency was achieved with the power supply delivering its full 650 W, at 87.7%, a value far from being low!
It is always good to remember that we test power supplies at very high temperatures (between 45° C and 50° C). Since efficiency drops with temperature, these results are even more impressive when you think about them, especially because 80 Plus certification is achieved with a room temperature of half of what we used (23° C).
Voltage regulation was another highlight from X-Series 650 W. The manufacturer promises a voltage regulation tighter than what published on the ATX specification (3% vs. 5%). During our tests all outputs were within 3% from their nominal values, i.e., closer to their nominal values than required. This included the -12 V output, which usually doesn’t like to stay so close from its nominal value.
And to close the lid we have noise and ripple, which were extremely low all the time: noise level at +12 V was around 12.5% of the maximum allowed. Below you can see the results for test number five. As we always point out, the limits are 120 mV for +12 V and 50 mV for +5 V and +3.3 V and all numbers are peak-to-peak figures.
Now let’s see if we could pull more than 650 W from this unit.
Before overloading a power supply we always like to see at what level its over current protection (OCP) circuit is configured. For this test we set +5 V and +3.3 V inputs from our load tester to pull only 1 A each and maxed out the two +12 V inputs for a total of 66 A. The power supply didn’t shut down, meaning that OCP is not present or is configured at a value above that. The manufacturer does not list OCP as a feature, so the first option seems to be the correct one.
Then we started increasing current on all outputs until we reached the maximum the unit could deliver. You can see the maximum we could pull from this unit below. If we increased one amp from any output ripple and noise would go through the roof, showing that the unit stopped working correctly.
The idea behind of overload tests is to see if the power supply will burn/explode and see if the protections from the power supply are working correctly. This power supply didn’t burn or explode. Even under this overloading efficiency was still very good.
25 A (300 W)
25 A (300 W)
20 A (100 W)
16 A (52.8 W)
2.5 A (12.5 W)
0.5 A (6 W)
% Max Load
Seasonic X-Series 650 W power supply specs include:
* Researched at Newegg.com on the day we published this review.
What a power supply! What a power supply! For the first time we can say that we found a flawless 650 W power supply. It presents efficiency of 90%, meaning that it consumes less energy from the wall, meaning a lower electricity bill for you. Voltages are within 3% from their nominal values, meaning that they are closer to their “correct” values than allowed (5% is the standard tolerance). And ultra-low ripple and noise levels, which means this power supply won’t overload the capacitors from the voltage regulator circuit from your motherboard or video card and will also prevent you system from producing random errors due to low-quality voltages.
It is always good to remember that we test power supplies at very high temperatures (between 45° C and 50° C). Since efficiency drops with temperature, these results are even more impressive when you think about them, especially because 80 Plus certification is achieved with a room temperature of half of what we used (23° C). We’ve seen power supplies that are 80 Plus Silver or Bronze not being able to deliver the promised efficiency in our labs because of that, what fortunately didn’t happen with X-Series 650 W.
The internal design is also flawless, using only Japanese capacitors rated at 105° C and solid models on the whole secondary. It uses a DC-DC design, which means that it is basically a +12 V power supply with +5 V and +3.3 V outputs being generated from this main +12 V line. This design is being used by several other high-efficiency units, but what makes X-Series completely different is where the components are located. Instead of putting the DC-DC converters on small daughterboards attached to the secondary, the converters are located on the same printed circuit board from the modular cabling system. This unique design allowed the power supply to have far less cables inside (since only a single +12 V connection between the main printed circuit board and the modular cabling system is necessary), which helps with thermal management and, indirectly, with efficiency (as the higher the temperature, the lower efficiency is).
Speaking of thermal management, the fan of this power supply only kicks in when needed. When the power supply is running with a small load (and thus low temperature), the fan is completely turned off, making the power supply to produce no noise at all.
All semiconductors used on this power supply are highly overspec’ed and this allowed us to pull almost 800 W from this 650 W unit.
And, the best of all: it is not that expensive for an ultra high-end product. The 650 W model costs USD 180 and the 750 W model costs USD 200, and we’ve seen power supplies with far lower construction quality and performance costing more than that.
As a side note, this was the first 80 Plus Gold power supply to reach the market. If you take a look at 80 Plus website you will see a lot of Gold power supplies being listed, however except for Z Series from OCZ all other products being listed there are still on the prototype phase, not available on the market yet.In summary, if you want the best power supply around, Seasonic X-Series is the product you should buy.