Introduction

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We would like to thank Seasonic for supplying the review sample.

Seasonic is one of the most experienced PSU OEMs, which makes every new product they release pretty interesting to a major portion of users and most PSU reviewers. Until recently, their portfolio only included two Platinum efficiency units, the SS-1000XP, which we have reviewed in the past, and the SS-860XP. Their other high-end models only feature Gold efficiency, but that situation is about to change significantly with the introduction of three new Platinum models with 760 W, 660 W, and 520 W capacity, the latter of which is a fanless unit.

Today, we will rigorously evaluate the Seasonic Platinum Series Fanless 520 W PSU. Its model number is SS-520FL, and it packs several improvements over the X-460FL: Seasonic's previous fanless PSU flagship. Capacity has, for starters, increased by 60 W and efficiency has been upgraded to Platinum. The SS-520FL's new platform is significantly different to the one its predecessor used. It allows for better performance and improved efficiency at low loads, which is an area the X-460FL didn't do so well in. The SS-520FL also comes with a fully modular cabling design, which will thrill most users, a well-ventilated enclosure that allows for optimal heat dissipation, a single +12V rail, and a seven-year warranty. The number of PCIe connectors has not changed. The unit only comes with two PCIe connectors. We were really expecting Seasonic to equip this unit with an additional two connectors since the capacity has increased, which would have made the SS-520FL an option with SLI or Crossfire configurations. We are pretty sure that many users out there will be let down by the lack of four PCIe connectors, and Seasonic should look into this issue as soon as possible.

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Specifications

<table class="tputbl">
<thead>
<tr>
<th colspan="2">Seasonic SS-520FL Features & Specs</th>
</tr>
</thead>
<tr>
<th scope="row">Max. DC Output</th>
<td align="center">520W</td>
</tr>
<tr class="alt">
<th scope="row">PFC</th>
<td align="center">Active PFC</td>
</tr>
<tr>
<th scope="row">Efficiency</th>
<td align="center">80 PLUS Platinum</td>
</tr>
<tr class="alt">
<th scope="row">Operating temperature</th>
<td align="center">0°C - 50°C</td>
</tr>
<tr>
<th scope="row">Protections</th>
<td align="center">Over Voltage Protection<br />
Under Voltage Protection<br />
Over Current Protection<br />
Over Power Protection<br />
Over Temperature Protection<br />
Short Circuit Protection</td>
</tr>
<tr class="alt">
<th scope="row">Cooling</th>
<td align="center">Fanless</td>
</tr>
<tr>
<th scope="row">Dimensions</th>
<td align="center">150 mm (W) x 86 mm (H) x 160 mm (D)</td>
</tr>
<tr class="alt">
<th scope="row">Weight</th>
<td align="center">2.0 kg</td>
</tr>
<tr>
<th scope="row">Compliance</th>
<td align="center">ATX12V v2.31, EPS 2.92</td>
</tr>
<tr class="alt">
<th scope="row">Warranty</th>
<td align="center">7 years</td>
</tr>
<tr>
<th scope="row">Price at time of review (exc. VAT)</th>
<td align="center">$149.90 (MSRP) </td>
</tr></table>

Efficiency is Platinum and the maximum operation temperature is 50°C, which is pretty special given that the unit doesn't have a fan to cool it down. It has all available protection features, and that includes OTP (Over Temperature Protection), something that is pretty crucial to a fanless unit. The unit's footprint is pretty compact with a width of 160 mm, and its warranty is really long at seven years. Seasonic seems to be pretty confident about this model's longevity even though the lack of a cooling fan means higher internal temperatures than those found inside a normal PSU. The price looks pretty stiff, but is, actually, fine for a fanless PSU, especially if we consider that other fanless units with less features and a lower performance are much more expensive.

<table class="tputbl">
<thead>
<tr>
<th colspan="8"><strong>Seasonic SS-520FL</strong> Power Specs</th>
</tr>
</thead>
<tr>
<th scope="row">Rail</th>
<td align="center">3.3V</td>
<td align="center">5V</td>
<td align="center">12V</td>
<td align="center">5VSB</td>
<td align="center">-12V</td>
</tr>
<tr class="alt">
<th rowspan="2" scope="row">Max. Power</th>
<td align="center">20A</td>
<td align="center">20A</td>
<td align="center">43A</td>
<td align="center">2.5A</td>
<td align="center">0.5A</td>
</tr>
<tr>
<td colspan="2" align="center">100W</td>
<td align="center">516W</td>
<td align="center">12.5W</td>
<td align="center">6W</td>
</tr>
<tr class="alt">
<th scope="row">Total Max. Power</th>
<td colspan="5" align="center">520W</td>
</tr></table>

The single +12V rail can deliver the unit's full power, which makes it quite strong and easily capable of supporting two mid-level VGAs. Seasonic will hopefully consider equipping each cable with two PCIe connectors instead of one.

The minor rails have enough power to meet the requirements of a modern system and the PSU's overall capacity. The 5VSB rail does feature the minimum power that a modern PSU should deliver on this rail.

Cables & Connectors, Power Distribution

<table class="tputbl">
<thead>
<tr>
<th colspan="2" align="center">Modular Cables</th>
</tr>
</thead>
<tr>
<th scope="row">ATX connector (600mm)</th>
<td align="center">20+4 pin</td>
</tr>
<tr class="alt">
<th scope="row">4+4 pin EPS12V (650mm)</th>
<td align="center">1</td>
</tr>
<tr>
<th scope="row"> 6+2 pin PCIe (600mm)</th>
<td align="center">2</td>
</tr>
<tr class="alt">
<th scope="row">4 pin Molex (410mm+125mm+125mm)</th>
<td align="center">3</td>
</tr>
<tr>
<th scope="row">4 pin Molex (305mm+125mm)</th>
<td align="center">2</td>
</tr>
<tr class="alt">
<th scope="row">SATA (390mm+115mm+115mm)</th>
<td align="center">3</td>
</tr>
<tr>
<th scope="row">SATA (300mm+115mm)</th>
<td align="center">2</td>
</tr>
<tr class="alt">
<th scope="row">FDD (+150mm)</th>
<td align="center">1</td>
</tr></table>

All cables are pretty long, and the distance amongst all connectors will suffice in most cases. The number of SATA and peripheral connectors is adequate for the capacity of the PSU, but the number of PCIe connectors is pretty small, and two additional PCIe connectors would be ideal.

The EPS and PCIe cables are fully sleeved, but the SATA and peripheral connectors use ribbon cables. All gauges are black, which will help modders hide them well. All connectors use 18AWG wires as recommended by the ATX spec.

We do not have anything to comment on about this PSU's power distribution since it features a single +12V rail.

Packaging

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The box is of medium size and features a nice platinum color that probably refers to the efficiency rating of the PSU. A significant portion of the front's real-estate is covered by a photo showcasing the PSU's well-ventilated enclosure. The face of the box also contains the Platinum efficiency badge, Seasonic's logo, the series name, and the capacity description on a black background.

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One of the two sides has the unit's specification table and the output ratings of all rails.

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Seasonic was kind enough to provide a photo of the unit's internal on the rear side of the box; for interested users. A paragraph explaining the differences between 80 Plus certifications, and the advantages of its higher 80 Plus Platinum certification, adorns a corresponding table. We also found references to Seasonic's patented modular panel that integrates the DC-DC converters of the minor rails, the tight voltage regulation, the unit's fanless operation, the use of Japanese polymer caps, the seven-year warranty, and the gold terminals of the modular connectors.

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On top of the box are a multilingual features description, the platinum badge, and the SS-520FL's series name.

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The PSU is well protected inside its box, so it will reach the hands of its buyer in perfect condition. A luxurious velvet bag provides some extra protection. There is also a notification to inform the buyer that this PSU is only meant to be used with cases that have good air-flow.

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A large pouch stores all modular cables and the rest of this rich bundle. The bundle includes the AC power cord, a set of fixing bolts, several Velcro straps, a case badge, and some zip ties.

Exterior

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Everyone with a basic knowledge of physics knows that hot air travels up. For all the rest, Seasonic put a notification on the PSU mentioning that the PSU should be installed with the top cover facing up. This will prevent hot air from being trapped inside the unit, which is important because hot, trapped air would most likely activate/trigger the PSU's Over Temperature Protection (OTP) feature.

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The PSU features a nice, light and matte finish that is fairly scratch resistant, but not fingerprint proof. This case reminds me of Swiss cheese because it is full of holes, which does allow hot air to move out of the case easily. We find the AC receptacle and the useful on/off switch on the front. Ventilation holes on both sides make large decals impossible, which is why we only find a small illustration of the series here. The modular panel can be found at the rear, and even there we find a vent that provides a clear view to two polymer Enesol caps. The specifications label and several vents are installed on the bottom side of the enclosure. Since there is no fan to push the hot air out of the case, Seasonic has, as you can see, made sure to exploit every inch of the case in an attempt to provide the best possible airflow.

A Look Inside & Component Analysis

Before reading this page, we strongly suggest a look at this article, which will help you understand the internal components of a PSU better.

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The unit's platform differs greatly from the one used in the X-460FL. The most noticeable differences are the full-bridge topology on the primary side and the relocation of the +12V regulation mosfets from the solder side of the main PCB to a daughter-board, which allows them to dissipate heat more efficiently. The platform uses modern technology. A full-bridge topology and an LLC resonant controller are utilized for increased efficiency on the primary side. The secondary side utilizes a synchronous design with both DC-DC converters on the modular PCB for reduced energy losses; the DC-DC converters are much closer to the modular connectors, which means that no transfer wires are needed.

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Behind the AC receptacle is a small PCB that is completely surrounded by a metal shield to suppress EMI. Four Y caps, a CM choke, and a single X cap are installed on this PCB. We also find two additional CM chokes, two pairs of X and Y caps, and an MOV on the main PCB. There is also an NTC thermistor for protection against large inrush currents and the corresponding relay that cuts it off the circuit once it finishes its job. Lastly, spade terminals were used on the power wires, which makes their removal from the main PCB a piece of cake.

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The standby Quasi-Resonant PWM Controller is an ICE2QR4765 IC. Exactly the same one is used in the X-400/460FL PSUs.

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The two parallel bridge rectifiers are two GBJ2506. They are too powerful for the needs of this unit. We do wonder why Seasonic failed to use two smaller bridges that cost less.

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Two Infineon IPP60R165CP fets with 0.165 Ohm max RDS(on) and a CREE C3D06060 boost diode are used in the APFC. The hold-up cap is provided by Hitachi (420V, 330μF) and is rated at 105°C. The APFC controller is hiding on a small daughter-board that is located between the APFC and the primary heatsink. It is the usual NPC1654 IC that Seasonic utilizes with their high-end platforms.

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The main switchers, four Infineon IPP50R250CPs, are arranged into a full bridge topology, and an LLC resonant converter is utilized to provide a significant efficiency boost.

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The +12V fets and the LLC resonant controller, a Champion CM6901 IC, are installed on a vertical PCB located on the secondary side. Two heatsinks handle the cooling of the +12V fets, and a thermistor attached to them provides information to the OTP circuit. A series of Enesol polymer caps, several Nippon Chemi-Con electrolytic caps (105°C, KZE series), and a single Rubycon cap filter this rail.

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The DC-DC converters that generate the minor rails are, to reduce energy losses, directly installed on the modular PCB. Both are controlled by an APW7159 PWM controller, and each one uses three RJK0332DPB fets. A heatsink is attached to the rear side of the modular panel, which helps remove the heat from the VRMs. We also find many Korean made Enesol filtering caps at the front of the modular PCB.

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The supervisor IC, a Weltrend WT7527, is installed on this PCB along with an LM339 quad-voltage comparator. The WT7527 supports up to two +12V virtual rails, but only one exists in this PSU.

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Soldering quality on the main PCB is, generally, good, but we spotted several handmade touch-ups, probably because this was an early production model. We are pretty sure that soldering will be impeccable once it goes into production fully, as is the case with every other high-end PSU unit produced by Seasonic.

Test Setup

All measurements were performed using two Chroma 6314A mainframes equipped with the following electronic loads: six 63123A [350 W each], one 63102A [100 W x2], and one 63101A [200 W]. The aforementioned equipment is able to deliver 2500 W of load, and all loads are controlled by a custom-made software. We also used a Picoscope 3424 oscilloscope, a Picotech TC-08 thermocouple data logger, a Fluke 175 multimeter, and a Yokogawa WT210 power meter. We also included a wooden box, which, along with some heating elements, was used as a hot box. We had at our disposal four more oscilloscopes (Rigol 1052E and VS5042, Stingray DS1M12, a second Picoscope 3424) and a CEM DT-8852 sound level meter. In this article, you will find more details about our equipment and the review methodology we follow. Finally, we conduct all of our tests at 40 - 45°C ambient in order to simulate with higher accuracy the environment seen inside a typical system, with 40 - 45°C being derived from a standard ambient assumption of 23°C and 17 - 22°C being added for the typical temperature rise within a system.

Primary Rails Voltage Regulation

The following charts show the voltage values of the main rails, recorded over a range of 60W to the maximum specified load, and the deviation (in percent) for the same load range.

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5VSB Regulation

The following chart shows how the 5VSB rail deals with the load we throw at it.
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Hold-up Time

The hold-up time is a very important characteristic of a PSU and represents the amount of time, usually measured in milliseconds, that a PSU can maintain output regulations without input power as defined by the ATX spec. In other words, it is the amount of time that the system can continue to run without shutting down or rebooting during a power interruption. The ATX spec sets the minimum hold-up time to 16 ms at maximum continuous output load. In the following screenshot, the blue line is the mains signal and the yellow line is the "Power Good" signal. The latter is de-asserted to a low state when any of the +12V, 5V, or 3.3V output voltages fall below the undervoltage threshold, or after the mains power has been removed for a sufficiently long time to guarantee that the PSU cannot operate anymore.

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The hold-up time meets ATX spec requirements, which means that the proper capacity hold-up cap was used.

Inrush Current

Inrush current or switch-on surge refers to the maximum, instantaneous input-current drawn by an electrical device as it is turned on. Because of the charging current of the APFC capacitor(s), PSUs produce large inrush-current right as they are turned on. Large inrush current can cause the tripping of circuit breakers and fuses and may also damage switches or relays; as a result, the lower the inrush current of a PSU right as they are turned on, the better.

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The SS-520FL's inrush current is the lowest we have ever measured with our new equipment. This is a clear indication of a well-designed platform that effectively suppresses high inrush currents during the start-up phase.

Voltage Regulation and Efficiency Measurements

The first set of tests revealed the stability of the voltage rails and the efficiency of the SS-520FL. The applied load was equal to (approximately) 20%, 40%, 50%, 60%, 80%, 100% and 110% of the maximum load that the PSU can handle. We also conducted two more tests. In the first test, we stressed the two minor rails (5V and 3.3V) with a high load while the load at +12V was only 2 A, and, in the second test, we dialed the maximum load that the +12V rail could handle while the load on the minor rails was minimal.

<table border="1" cellpadding="4" cellspacing="0" bordercolor="#aaaaaa" style="border-collapse:collapse">
<tr>
<th colspan="9" class="th1 tac" style="font-size:15pt"> Voltage Regulation & Efficiency Testing Data <br/>
Seasonic SS-520FL</th>
</tr>
<tr bgcolor="#dddddd">
<td width="115" align="center" bgcolor="#DEE2E7"><strong>Test</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>12 V</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>5 V</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>3.3 V</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>5VSB</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>Power<br />
(DC/AC)</strong></td>
<td align="center" bgcolor="#DEE2E7"><strong>Efficiency</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>Temp<br />
(In/Out)</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>PF/AC <br>
Volts</strong></td>
</tr>
<tr>
<td rowspan="2" align="center" bgcolor="#DEE2E7"><strong>20% Load</strong></td>
<td align="center" bgcolor="#f9f9f9">6.807A</td>
<td align="center" bgcolor="#f9f9f9">1.971A</td>
<td align="center" bgcolor="#f9f9f9">1.968A</td>
<td align="center" bgcolor="#f9f9f9">0.980A</td>
<td align="center" bgcolor="#f9f9f9">103.70W</td>
<td rowspan="2" align="center" bgcolor="#f9f9f9">91.32%</td>
<td align="center" bgcolor="#f9f9f9"> 48.56°C</td>
<td align="center" bgcolor="#f9f9f9">0.849</td>
</tr>
<tr>
<td align="center" bgcolor="#f0f0f0">12.071V</td>
<td align="center" bgcolor="#f0f0f0">5.054V</td>
<td align="center" bgcolor="#f0f0f0">3.348V</td>
<td align="center" bgcolor="#f0f0f0">5.088V</td>
<td align="center" bgcolor="#f0f0f0">113.56W</td>
<td align="center" bgcolor="#f0f0f0"> 38.60°C</td>
<td align="center" bgcolor="#f0f0f0">230.0V</td>
</tr>
<tr>
<td rowspan="2" align="center" bgcolor="#DEE2E7"><strong>40% Load</strong></td>
<td align="center" bgcolor="#f9f9f9">13.976A</td>
<td align="center" bgcolor="#f9f9f9">3.952A</td>
<td align="center" bgcolor="#f9f9f9">3.944A</td>
<td align="center" bgcolor="#f9f9f9">1.179A</td>
<td align="center" bgcolor="#f9f9f9">207.64W</td>
<td rowspan="2" align="center" bgcolor="#f9f9f9">93.59%</td>
<td align="center" bgcolor="#f9f9f9"> 50.37°C</td>
<td align="center" bgcolor="#f9f9f9">0.933</td>
</tr>
<tr>
<td align="center" bgcolor="#f0f0f0">12.057V</td>
<td align="center" bgcolor="#f0f0f0">5.052V</td>
<td align="center" bgcolor="#f0f0f0">3.344V</td>
<td align="center" bgcolor="#f0f0f0">5.071V</td>
<td align="center" bgcolor="#f0f0f0">221.87W</td>
<td align="center" bgcolor="#f0f0f0"> 39.32°C</td>
<td align="center" bgcolor="#f0f0f0">230.0V</td>
</tr>
<tr>
<td rowspan="2" align="center" bgcolor="#DEE2E7"><strong>50% Load</strong></td>
<td align="center" bgcolor="#f9f9f9">17.442A</td>
<td align="center" bgcolor="#f9f9f9">4.951A</td>
<td align="center" bgcolor="#f9f9f9">4.933A</td>
<td align="center" bgcolor="#f9f9f9">1.581A</td>
<td align="center" bgcolor="#f9f9f9">259.66W</td>
<td rowspan="2" align="center" bgcolor="#f9f9f9">93.64%</td>
<td align="center" bgcolor="#f9f9f9"> 52.56°C</td>
<td align="center" bgcolor="#f9f9f9">0.947</td>
</tr>
<tr>
<td align="center" bgcolor="#f0f0f0">12.050V</td>
<td align="center" bgcolor="#f0f0f0">5.049V</td>
<td align="center" bgcolor="#f0f0f0">3.343V</td>
<td align="center" bgcolor="#f0f0f0">5.056V</td>
<td align="center" bgcolor="#f0f0f0">277.31W</td>
<td align="center" bgcolor="#f0f0f0"> 40.17°C</td>
<td align="center" bgcolor="#f0f0f0">229.9V</td>
</tr>
<tr>
<td rowspan="2" align="center" bgcolor="#DEE2E7"><strong>60% Load</strong></td>
<td align="center" bgcolor="#f9f9f9">20.918A</td>
<td align="center" bgcolor="#f9f9f9">5.935A</td>
<td align="center" bgcolor="#f9f9f9">5.923A</td>
<td align="center" bgcolor="#f9f9f9">1.980A</td>
<td align="center" bgcolor="#f9f9f9">311.62W</td>
<td rowspan="2" align="center" bgcolor="#f9f9f9">93.63%</td>
<td align="center" bgcolor="#f9f9f9"> 55.49°C</td>
<td align="center" bgcolor="#f9f9f9">0.957</td>
</tr>
<tr>
<td align="center" bgcolor="#f0f0f0">12.042V</td>
<td align="center" bgcolor="#f0f0f0">5.048V</td>
<td align="center" bgcolor="#f0f0f0">3.341V</td>
<td align="center" bgcolor="#f0f0f0">5.040V</td>
<td align="center" bgcolor="#f0f0f0">332.84W</td>
<td align="center" bgcolor="#f0f0f0"> 41.52°C</td>
<td align="center" bgcolor="#f0f0f0">229.9V</td>
</tr>
<tr>
<td rowspan="2" align="center" bgcolor="#DEE2E7"><strong>80% Load</strong></td>
<td align="center" bgcolor="#f9f9f9">28.035A</td>
<td align="center" bgcolor="#f9f9f9">7.918A</td>
<td align="center" bgcolor="#f9f9f9">7.905A</td>
<td align="center" bgcolor="#f9f9f9">2.391A</td>
<td align="center" bgcolor="#f9f9f9">415.57W</td>
<td rowspan="2" align="center" bgcolor="#f9f9f9">93.18%</td>
<td align="center" bgcolor="#f9f9f9"> 57.58°C</td>
<td align="center" bgcolor="#f9f9f9">0.968</td>
</tr>
<tr>
<td align="center" bgcolor="#f0f0f0">12.029V</td>
<td align="center" bgcolor="#f0f0f0">5.045V</td>
<td align="center" bgcolor="#f0f0f0">3.338V</td>
<td align="center" bgcolor="#f0f0f0">5.019V</td>
<td align="center" bgcolor="#f0f0f0">445.97W</td>
<td align="center" bgcolor="#f0f0f0"> 41.98°C</td>
<td align="center" bgcolor="#f0f0f0">230.0V</td>
</tr>
<tr>
<td rowspan="2" align="center" bgcolor="#DEE2E7"><strong>100% Load</strong></td>
<td align="center" bgcolor="#f9f9f9">35.984A</td>
<td align="center" bgcolor="#f9f9f9">8.920A</td>
<td align="center" bgcolor="#f9f9f9">8.899A</td>
<td align="center" bgcolor="#f9f9f9">2.496A</td>
<td align="center" bgcolor="#f9f9f9">519.48W</td>
<td rowspan="2" align="center" bgcolor="#f9f9f9">92.76%</td>
<td align="center" bgcolor="#f9f9f9"> 59.77°C</td>
<td align="center" bgcolor="#f9f9f9">0.974</td>
</tr>
<tr>
<td align="center" bgcolor="#f0f0f0">12.014V</td>
<td align="center" bgcolor="#f0f0f0">5.042V</td>
<td align="center" bgcolor="#f0f0f0">3.337V</td>
<td align="center" bgcolor="#f0f0f0">5.005V</td>
<td align="center" bgcolor="#f0f0f0">560.02W</td>
<td align="center" bgcolor="#f0f0f0"> 42.91°C</td>
<td align="center" bgcolor="#f0f0f0">229.9V</td>
</tr>
<tr>
<td rowspan="2" align="center" bgcolor="#DEE2E7"><strong>110% Load</strong></td>
<td align="center" bgcolor="#f9f9f9">40.321A</td>
<td align="center" bgcolor="#f9f9f9">8.922A</td>
<td align="center" bgcolor="#f9f9f9">8.902A</td>
<td align="center" bgcolor="#f9f9f9">2.498A</td>
<td align="center" bgcolor="#f9f9f9">571.40W</td>
<td rowspan="2" align="center" bgcolor="#f9f9f9">92.59%</td>
<td align="center" bgcolor="#f9f9f9"> 60.41°C</td>
<td align="center" bgcolor="#f9f9f9">0.977</td>
</tr>
<tr>
<td align="center" bgcolor="#f0f0f0">12.010V</td>
<td align="center" bgcolor="#f0f0f0">5.040V</td>
<td align="center" bgcolor="#f0f0f0">3.335V</td>
<td align="center" bgcolor="#f0f0f0">5.000V</td>
<td align="center" bgcolor="#f0f0f0">617.15W</td>
<td align="center" bgcolor="#f0f0f0"> 43.15°C</td>
<td align="center" bgcolor="#f0f0f0">229.8V</td>
</tr>
<tr>
<td rowspan="2" align="center" bgcolor="#DEE2E7"><strong>Crossload 1</strong></td>
<td align="center" bgcolor="#f9f9f9">1.969A</td>
<td align="center" bgcolor="#f9f9f9">11.999A</td>
<td align="center" bgcolor="#f9f9f9">12.004A</td>
<td align="center" bgcolor="#f9f9f9">0.502A</td>
<td align="center" bgcolor="#f9f9f9">126.99W</td>
<td rowspan="2" align="center" bgcolor="#f9f9f9">88.86%</td>
<td align="center" bgcolor="#f9f9f9"> 54.24°C</td>
<td align="center" bgcolor="#f9f9f9">0.885</td>
</tr>
<tr>
<td align="center" bgcolor="#f0f0f0">12.058V</td>
<td align="center" bgcolor="#f0f0f0">5.048V</td>
<td align="center" bgcolor="#f0f0f0">3.343V</td>
<td align="center" bgcolor="#f0f0f0">5.083V</td>
<td align="center" bgcolor="#f0f0f0">142.91W</td>
<td align="center" bgcolor="#f0f0f0"> 40.82°C</td>
<td align="center" bgcolor="#f0f0f0">230.1V</td>
</tr>
<tr>
<td rowspan="2" align="center" bgcolor="#DEE2E7"><strong>Crossload 2</strong></td>
<td align="center" bgcolor="#f9f9f9">42.971A</td>
<td align="center" bgcolor="#f9f9f9">1.000A</td>
<td align="center" bgcolor="#f9f9f9">1.003A</td>
<td align="center" bgcolor="#f9f9f9">1.001A</td>
<td align="center" bgcolor="#f9f9f9">530.14W</td>
<td rowspan="2" align="center" bgcolor="#f9f9f9">93.52%</td>
<td align="center" bgcolor="#f9f9f9"> 57.05°C</td>
<td align="center" bgcolor="#f9f9f9">0.975</td>
</tr>
<tr>
<td align="center" bgcolor="#f0f0f0">12.024V</td>
<td align="center" bgcolor="#f0f0f0">5.046V</td>
<td align="center" bgcolor="#f0f0f0">3.343V</td>
<td align="center" bgcolor="#f0f0f0">5.054V</td>
<td align="center" bgcolor="#f0f0f0">566.89W</td>
<td align="center" bgcolor="#f0f0f0"> 41.28°C</td>
<td align="center" bgcolor="#f0f0f0">229.9V</td>
</tr>
</table>

The unit managed to deliver its full power (and even more) at 43°C ambient. We tried to pull its full power at even higher temperatures, but anything above 44-45°C triggered OTP. Apparently, Seasonic preferred to stay on the safe side by setting the OTP trigger-point to a temperature much lower than 50°C. The good thing here is that the OTP works well by safely shutting the unit down before it overheats significantly, which will garner its components some more longevity. It took a while to raise the ambient temperature of our hot box because the SS-520FL operates at incredibly low temperatures due to its extra-high efficiency. The PSU's efficiency really is pretty amazing and exceeded 93% in five out of the nine tests. This is stellar even for a Platinum PSU. Seasonic is probably paving the ground for a new Titanium efficiency level!

Voltage regulation is also nothing less than great since all three major rails registered very low deviations. SS-520FL's 5V and 3.3V efficiency also managed to take the lead by beating out Corsair's high-end models that use digital control on those rails. As you can see, a top-notch design utilizing conventional components/methods can provide equally great or better performance than a DSP controlled design. The only downside of the SS-520FL's performance is its low PF at 20% load, which should exceed 0.9. However, a high PF is not that important to residential customers since they only pay for Real Power, not Reactive Power. Yet a high PF is still somewhat desirable because it would put less stress on the mains power grid.

Efficiency

Using the efficiency results from the previous page, we plotted a chart showing efficiency of the SS-520FL at low loads and at loads equal to 20-110% of the PSU's maximum rated load.

http://www.techpowerup.com/reviews/S...efficiency.jpg http://www.techpowerup.com/reviews/S..._low_loads.gif http://www.techpowerup.com/reviews/S...rmal_loads.gif

For a discussion of these results, see the text at the end of the previous page.

Efficiency at Low Loads

In the next tests, we measured the efficiency of the SS-520FL at loads much lower than 20% of its maximum rated load (the lowest load that the 80 Plus Standard measures). The loads that we dialed were 40, 60, 80, and 100 W (for PSUs with over 500 W of capacity). This is important for settings where the PC is in idle mode with power saving turned on.

<table border="1" cellpadding="4" cellspacing="0" bordercolor="#aaaaaa" style="border-collapse:collapse">
<tr>
<th colspan="8" class="th1 tac" style="font-size:15pt"> Efficiency at Low Loads <br/>
Seasonic SS-520FL</th>
</tr>
<tr>
<td width="100" align="center" bgcolor="#DEE2E7"><strong>Test #</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>12 V</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>5 V</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>3.3 V</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>5 VSB</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>Power<br />
(DC/AC)</strong></td>
<td align="center" bgcolor="#DEE2E7"><strong>Efficiency</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>PF/AC <br>
Volts</strong></td>
</tr>
<tr>
<td rowspan="2" align="center" bgcolor="#DEE2E7"><strong>1</strong></td>
<td align="center" bgcolor="#f9f9f9">1.833A</td>
<td align="center" bgcolor="#f9f9f9">1.971A</td>
<td align="center" bgcolor="#f9f9f9">1.969A</td>
<td align="center" bgcolor="#f9f9f9">0.195A</td>
<td align="center" bgcolor="#f9f9f9">39.69W</td>
<td rowspan="2" align="center" bgcolor="#f9f9f9">83.28%</td>
<td align="center" bgcolor="#f9f9f9">0.713</td>
</tr>
<tr>
<td align="center" bgcolor="#f0f0f0">12.077V</td>
<td align="center" bgcolor="#f0f0f0">5.055V</td>
<td align="center" bgcolor="#f0f0f0">3.348V</td>
<td align="center" bgcolor="#f0f0f0">5.111V</td>
<td align="center" bgcolor="#f0f0f0">47.66W</td>
<td align="center" bgcolor="#f0f0f0">230.0V</td>
</tr>
<tr>
<td rowspan="2" align="center" bgcolor="#DEE2E7"><strong>2</strong></td>
<td align="center" bgcolor="#f9f9f9">3.407A</td>
<td align="center" bgcolor="#f9f9f9">1.971A</td>
<td align="center" bgcolor="#f9f9f9">1.969A</td>
<td align="center" bgcolor="#f9f9f9">0.389A</td>
<td align="center" bgcolor="#f9f9f9">59.68W</td>
<td rowspan="2" align="center" bgcolor="#f9f9f9">87.47%</td>
<td align="center" bgcolor="#f9f9f9">0.769</td>
</tr>
<tr>
<td align="center" bgcolor="#f0f0f0">12.075V</td>
<td align="center" bgcolor="#f0f0f0">5.055V</td>
<td align="center" bgcolor="#f0f0f0">3.348V</td>
<td align="center" bgcolor="#f0f0f0">5.105V</td>
<td align="center" bgcolor="#f0f0f0">68.23W</td>
<td align="center" bgcolor="#f0f0f0">230.0V</td>
</tr>
<tr>
<td rowspan="2" align="center" bgcolor="#DEE2E7"><strong>3</strong></td>
<td align="center" bgcolor="#f9f9f9">4.982A</td>
<td align="center" bgcolor="#f9f9f9">1.971A</td>
<td align="center" bgcolor="#f9f9f9">1.969A</td>
<td align="center" bgcolor="#f9f9f9">0.584A</td>
<td align="center" bgcolor="#f9f9f9">79.68W</td>
<td rowspan="2" align="center" bgcolor="#f9f9f9">89.75%</td>
<td align="center" bgcolor="#f9f9f9">0.815</td>
</tr>
<tr>
<td align="center" bgcolor="#f0f0f0">12.073V</td>
<td align="center" bgcolor="#f0f0f0">5.055V</td>
<td align="center" bgcolor="#f0f0f0">3.348V</td>
<td align="center" bgcolor="#f0f0f0">5.098V</td>
<td align="center" bgcolor="#f0f0f0">88.78W</td>
<td align="center" bgcolor="#f0f0f0">230.0V</td>
</tr>
<tr>
<td rowspan="2" align="center" bgcolor="#DEE2E7"><strong>4</strong></td>
<td align="center" bgcolor="#f9f9f9">5.726A</td>
<td align="center" bgcolor="#f9f9f9">1.971A</td>
<td align="center" bgcolor="#f9f9f9">1.969A</td>
<td align="center" bgcolor="#f9f9f9">0.785A</td>
<td align="center" bgcolor="#f9f9f9">89.68W</td>
<td rowspan="2" align="center" bgcolor="#f9f9f9">90.40%</td>
<td align="center" bgcolor="#f9f9f9">0.828</td>
</tr>
<tr>
<td align="center" bgcolor="#f0f0f0">12.072V</td>
<td align="center" bgcolor="#f0f0f0">5.055V</td>
<td align="center" bgcolor="#f0f0f0">3.348V</td>
<td align="center" bgcolor="#f0f0f0">5.093V</td>
<td align="center" bgcolor="#f0f0f0">99.20W</td>
<td align="center" bgcolor="#f0f0f0">230.0V</td>
</tr>
</table>

Efficiency at low loads is simply amazing. The PSU registered far above 80% efficiency with a mere 40W load, and even surpasses 90% with a 90 W load! This is definitely the right PSU for drawing low wattage in idle.

5VSB Efficiency

The ATX spec states that the 5VSB standby supply's efficiency should be as high as possible and recommends 50% or higher efficiency with 100 mA of load, 60% or higher with 250 mA of load, and 70% or higher with 1 A or more of load.
We will take four measurements: one at 100, 250, and 1000 mA, and one with the full load that the 5VSB rail can handle.

<table border="1" cellpadding="4" cellspacing="0" bordercolor="#aaaaaa" style="border-collapse:collapse">
<tr>
<th colspan="5" class="th1 tac" style="font-size:15pt"> 5VSB Efficiency<br/>
Seasonic SS-520FL</th>
</tr>
<tr>
<td width="100" align="center" bgcolor="#DEE2E7"><strong>Test #</strong></td>
<td width="100" align="center" bgcolor="#DEE2E7"><strong>5VSB</strong></td>
<td width="100" align="center" bgcolor="#DEE2E7"><strong>Power (DC/AC)</strong></td>
<td width="100" align="center" bgcolor="#DEE2E7"><strong>Efficiency</strong></td>
<td width="100" align="center" bgcolor="#DEE2E7"><strong>PF/AC Volts</strong></td>
</tr>
<tr>
<td rowspan="2" align="center" bgcolor="#DEE2E7"><strong>1</strong></td>
<td align="center" bgcolor="#f9f9f9">0.101A</td>
<td align="center" bgcolor="#f9f9f9">0.52W</td>
<td rowspan="2" align="center" bgcolor="#f9f9f9">68.42%</td>
<td align="center" bgcolor="#f9f9f9">0.043</td>
</tr>
<tr>
<td align="center" bgcolor="#f0f0f0">5.122V</td>
<td align="center" bgcolor="#f0f0f0">0.76W</td>
<td align="center" bgcolor="#f0f0f0">230.4V</td>
</tr>
<tr>
<td rowspan="2" align="center" bgcolor="#DEE2E7"><strong>2</strong></td>
<td align="center" bgcolor="#f9f9f9">0.251A</td>
<td align="center" bgcolor="#f9f9f9">1.28W</td>
<td rowspan="2" align="center" bgcolor="#f9f9f9">72.32%</td>
<td align="center" bgcolor="#f9f9f9">0.097</td>
</tr>
<tr>
<td align="center" bgcolor="#f0f0f0">5.117V</td>
<td align="center" bgcolor="#f0f0f0">1.77W</td>
<td align="center" bgcolor="#f0f0f0">230.4V</td>
</tr>
<tr>
<td rowspan="2" align="center" bgcolor="#DEE2E7"><strong>3</strong></td>
<td align="center" bgcolor="#f9f9f9">1.002A</td>
<td align="center" bgcolor="#f9f9f9">5.11W</td>
<td rowspan="2" align="center" bgcolor="#f9f9f9">79.23%</td>
<td align="center" bgcolor="#f9f9f9">0.260</td>
</tr>
<tr>
<td align="center" bgcolor="#f0f0f0">5.098V</td>
<td align="center" bgcolor="#f0f0f0">6.45W</td>
<td align="center" bgcolor="#f0f0f0">230.2V</td>
</tr>
<tr>
<td rowspan="2" align="center" bgcolor="#DEE2E7"><strong>4</strong></td>
<td align="center" bgcolor="#f9f9f9">2.501A</td>
<td align="center" bgcolor="#f9f9f9">12.67W</td>
<td rowspan="2" align="center" bgcolor="#f9f9f9">82.54%</td>
<td align="center" bgcolor="#f9f9f9">0.364</td>
</tr>
<tr>
<td align="center" bgcolor="#f0f0f0">5.064V</td>
<td align="center" bgcolor="#f0f0f0">15.35W</td>
<td align="center" bgcolor="#f0f0f0">230.2V</td>
</tr>
</table>

The 5VSB managed to achieve noteworthy efficiency in all of our tests by easily surpassing the threshold the ATX spec sets. It even cracked the 80% threshold on our last test, which is not common for this rail.

Power Consumption in Idle & Standby

In the table below, you will find the power consumption and the voltage values of all rails (except -12V) when the PSU is in idle mode (powered on but without any load on its rails) and the power consumption when the PSU is in standby mode (without any load at 5VSB).

<table border="1" cellpadding="4" cellspacing="0" bordercolor="#aaaaaa" style="border-collapse:collapse">
<tr>
<th colspan="7" class="th1 tac" style="font-size:15pt"> Idle / Standby <br/>
Seasonic SS-520FL</th>
</tr>
<tr>
<td width="100" align="center" bgcolor="#DEE2E7"><strong>Mode</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>12 V</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>5 V</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>3.3 V</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>5VSB</strong></td>
<td width="85" align="center" bgcolor="#DEE2E7"><strong>Power (AC)</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>PF/AC Volts</strong></td>
</tr>
<tr>
<td rowspan="2" align="center" bgcolor="#DEE2E7"><strong>Idle</strong></td>
<td rowspan="2" align="center" bgcolor="#f0f0f0">12.085V</td>
<td rowspan="2" align="center" bgcolor="#f0f0f0">5.059V</td>
<td rowspan="2" align="center" bgcolor="#f0f0f0">3.351V</td>
<td rowspan="2" align="center" bgcolor="#f0f0f0">5.123V</td>
<td rowspan="2" align="center" bgcolor="#f0f0f0">6.00W</td>
<td align="center" bgcolor="#f0f0f0">0.268</td>
</tr>
<tr>
<td align="center" bgcolor="#f9f9f9">230.1V</td>
</tr>
<tr>
<td rowspan="2" colspan="5" align="center" bgcolor="#DEE2E7"><strong>Standby</strong></td>
<td rowspan="2" align="center" bgcolor="#f0f0f0">0.17W</td>
<td align="center" bgcolor="#f0f0f0">0.011</td>
</tr>
<tr>
<td align="center" bgcolor="#f9f9f9">230.3V</td>
</tr>
</table>

Phantom power is low and easily meets the ErP Lot 6 requirements for both 2010 and 2013. This means that the carbon footprint of the PSU is low, which will, in the long run, save you some money on your electricity bills.

Delta Temperature

The delta difference between input and output temperature are illustrated in the following chart. The results were obtained at 40°C - 45°C ambient.

http://www.techpowerup.com/reviews/S.../fan_speed.jpg

Cross Load Tests

For the generation of the following charts, we set our loaders to auto mode through our custom-made software before trying over a thousand possible load combinations with the +12V, 5V, and 3.3V rails. The voltage regulation deviations in each of the charts below were calculated by taking the nominal values of the rails (12V, 5V, and 3.3V) as point zero. We should note here that we only run this test with PSUs that have a capacity equal to or lower than 1000 W since it takes a long time to run and because the completion time increases exponentially as a unit's capacity increases.

+12V Voltage Regulation Chart

http://www.techpowerup.com/reviews/S...ges/CL_12V.jpg

5V Voltage Regulation Chart

http://www.techpowerup.com/reviews/S...ages/CL_5V.jpg

3.3V Voltage Regulation Chart

http://www.techpowerup.com/reviews/S...ges/CL_33V.jpg

Efficiency Chart

http://www.techpowerup.com/reviews/S...efficiency.jpg

+12V Ripple Chart

http://www.techpowerup.com/reviews/S...ipple_12V1.jpg

5V Ripple Chart

http://www.techpowerup.com/reviews/S..._ripple_5V.jpg

3.3V Ripple Chart

http://www.techpowerup.com/reviews/S...ripple_33V.jpg

5VSB Ripple Chart

http://www.techpowerup.com/reviews/S...ipple_5VSB.jpg

Advanced Transient Response Tests

In these tests, we monitor the response of the PSU in two different scenarios. First, a transient load (10 A at +12V, 5 A at 5V, 5 A at 3.3V, and 0.5 A at 5VSB) is applied to the PSU for 200 ms while the latter is working at a 20% load state. In the second scenario, the PSU, while working at 50% load, is hit by the same transient load. In both tests, we measure the voltage drops that the transient load causes using our oscilloscope. The voltages should remain within the regulation limits defined by the ATX specification. We must stress here that the above tests are crucial since they simulate transient loads that a PSU is very likely to handle (e.g., booting a RAID array, an instant 100% load of CPU/VGAs, etc.) We call these tests "Advanced Transient Response Tests", and they are designed to be very tough to master, especially for PSUs with capacities lower than 500 W.

<div style="float:left">http://www.techpowerup.com/reviews/S...ansient_20.gif</div><div style="float:left"><table border="1" cellpadding="4" cellspacing="0" bordercolor="#aaaaaa" style="border-collapse:collapse">
<tr>
<th colspan="5" class="th1 tac" style="font-size:15pt"> Advanced Transient Response 20%</th>
</tr>
<tr>
<td align="center" bgcolor="#DEE2E7"><strong>Voltage</strong></td>
<td align="center" bgcolor="#DEE2E7"><strong>Before</strong></td>
<td align="center" bgcolor="#DEE2E7"><strong>After</strong></td>
<td align="center" bgcolor="#DEE2E7"><strong>Change</strong></td>
<td align="center" bgcolor="#DEE2E7"><strong>Pass/Fail</strong></td>
</tr>
<tr>
<td align="center" bgcolor="#DEE2E7"><strong>12 V</strong></td>
<td align="center" bgcolor="#f9f9f9">12.072V</td>
<td align="center" bgcolor="#f9f9f9">11.956V</td>
<td align="center" bgcolor="#f9f9f9">0.96%</td>
<td align="center" bgcolor="#f9f9f9">Pass</td>
</tr>
<tr>
<td align="center" bgcolor="#DEE2E7"><strong>5 V</strong></td>
<td align="center" bgcolor="#f9f9f9">5.053V</td>
<td align="center" bgcolor="#f9f9f9">4.992V</td>
<td align="center" bgcolor="#f9f9f9">1.21%</td>
<td align="center" bgcolor="#f9f9f9">Pass</td>
</tr>
<tr>
<td align="center" bgcolor="#DEE2E7"><strong>3.3 V</strong></td>
<td align="center" bgcolor="#f9f9f9">3.348V</td>
<td align="center" bgcolor="#f9f9f9">3.254V</td>
<td align="center" bgcolor="#f9f9f9">2.81%</td>
<td align="center" bgcolor="#f9f9f9">Pass</td>
</tr>
<tr>
<td align="center" bgcolor="#DEE2E7"><strong>5VSB</strong></td>
<td align="center" bgcolor="#f9f9f9">5.089V</td>
<td align="center" bgcolor="#f9f9f9">5.052V</td>
<td align="center" bgcolor="#f9f9f9">0.73%</td>
<td align="center" bgcolor="#f9f9f9">Pass</td>
</tr>
</table></div><div style="clear:both"></div>

<div style="float:left">http://www.techpowerup.com/reviews/S...ansient_50.gif</div><div style="float:left"></div><table border="1" cellpadding="4" cellspacing="0" bordercolor="#aaaaaa" style="border-collapse:collapse">
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<th colspan="5" class="th1 tac" style="font-size:15pt"> Advanced Transient Response 50%</th>
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<td align="center" bgcolor="#DEE2E7"><strong>Voltage</strong></td>
<td align="center" bgcolor="#DEE2E7"><strong>Before</strong></td>
<td align="center" bgcolor="#DEE2E7"><strong>After</strong></td>
<td align="center" bgcolor="#DEE2E7"><strong>Change</strong></td>
<td align="center" bgcolor="#DEE2E7"><strong>Pass/Fail</strong></td>
</tr>
<tr>
<td align="center" bgcolor="#DEE2E7"><strong>12 V</strong></td>
<td align="center" bgcolor="#f9f9f9">12.049V</td>
<td align="center" bgcolor="#f9f9f9">11.908V</td>
<td align="center" bgcolor="#f9f9f9">1.17%</td>
<td align="center" bgcolor="#f9f9f9">Pass</td>
</tr>
<tr>
<td align="center" bgcolor="#DEE2E7"><strong>5 V</strong></td>
<td align="center" bgcolor="#f9f9f9">5.048V</td>
<td align="center" bgcolor="#f9f9f9">4.969V</td>
<td align="center" bgcolor="#f9f9f9">1.56%</td>
<td align="center" bgcolor="#f9f9f9">Pass</td>
</tr>
<tr>
<td align="center" bgcolor="#DEE2E7"><strong>3.3 V</strong></td>
<td align="center" bgcolor="#f9f9f9">3.344V</td>
<td align="center" bgcolor="#f9f9f9">3.221V</td>
<td align="center" bgcolor="#f9f9f9">3.68%</td>
<td align="center" bgcolor="#f9f9f9">Pass</td>
</tr>
<tr>
<td align="center" bgcolor="#DEE2E7"><strong>5VSB</strong></td>
<td align="center" bgcolor="#f9f9f9">5.057V</td>
<td align="center" bgcolor="#f9f9f9">5.017V</td>
<td align="center" bgcolor="#f9f9f9">0.79%</td>
<td align="center" bgcolor="#f9f9f9">Pass</td>
</tr>
</table><div style="clear:both"></div>

Deviations are low on all rails, so the registered voltage drops are small; that is, except for the 3.3V rail. The 3.3V rail registered deviations close to 4%, but the tight voltage regulation allowed the 3.3V rail to keep its voltage above 3.2V.

Below, you will find the oscilloscope screenshots that we took during Advanced Transient Response Testing.

Transient Response at 20% Load

http://www.techpowerup.com/reviews/S...n_20_small.jpg http://www.techpowerup.com/reviews/S...n_20_small.jpg http://www.techpowerup.com/reviews/S...n_20_small.jpg http://www.techpowerup.com/reviews/S...n_20_small.jpg

Transient Response at 50% Load

http://www.techpowerup.com/reviews/S...n_50_small.jpg http://www.techpowerup.com/reviews/S...n_50_small.jpg http://www.techpowerup.com/reviews/S...n_50_small.jpg http://www.techpowerup.com/reviews/S...n_50_small.jpg

Turn-On Transient Tests

We measure the response of the PSU in simpler scenarios of transient loads - during the power-on phase of the PSU - in the next set of tests. In the first test, we turn the PSU off, dial the maximum current that the 5VSB can output, and then switch on the PSU. In the second test, we dial the maximum load that +12V can handle and we start the PSU, all while the PSU is in standby mode. In the last test, while the PSU is completely switched off (we cut off power or switch off the PSU's on/off switch), we dial the maximum load that the +12V rail can handle before switching the PSU on from the loader and restoring power. The ATX specification states that recorded spikes on all rails should not exceed 10% of their nominal values (e.g., +10% for 12V is 13.2V and for 5V is 5.5V).

http://www.techpowerup.com/reviews/S...5vsb_small.jpg http://www.techpowerup.com/reviews/S..._stb_small.jpg http://www.techpowerup.com/reviews/S..._off_small.jpg
The spike at 5VSB is minimal and under the rail's nominal voltage, and the rise time is within the specified range (0.2 - 20 ms). There are no voltage overshoots on the +12V rail and only during the last test did the +12V rail register a tiny step/dive at around 4 V. All in all, the unit performed very well on these tests.

Ripple Measurements

You will see the ripple levels that we measured on the main rails of the SS-520FL in the following table. The limits are, according to the ATX specifications, 120 mV (+12V) and 50 mV (5V, 3.3V, and 5VSB).

<table border="1" cellpadding="4" cellspacing="0" bordercolor="#aaaaaa" style="border-collapse:collapse">
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<th colspan="6" class="th1 tac" style="font-size:15pt"> Ripple Measurements<br/>
Seasonic SS-520FL</th>
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<td width="100" align="center" bgcolor="#DEE2E7"><strong>Test</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>12 V</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>5 V</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>3.3 V</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>5VSB</strong></td>
<td width="80" align="center" bgcolor="#DEE2E7"><strong>Pass/Fail</strong></td>
</tr>
<tr>
<td align="center" bgcolor="#DEE2E7"><strong>20% Load</strong></td>
<td align="center" bgcolor="#f9f9f9">16.8 mV</td>
<td align="center" bgcolor="#f9f9f9">11.1 mV</td>
<td align="center" bgcolor="#f9f9f9">8.1 mV</td>
<td align="center" bgcolor="#f9f9f9">4.5 mV</td>
<td align="center" bgcolor="#f9f9f9">Pass</td>
</tr>
<tr>
<td align="center" bgcolor="#DEE2E7"><strong>40% Load</strong></td>
<td align="center" bgcolor="#f0f0f0">21.7 mV</td>
<td align="center" bgcolor="#f0f0f0">11.2 mV</td>
<td align="center" bgcolor="#f0f0f0">8.5 mV</td>
<td align="center" bgcolor="#f0f0f0">4.9 mV</td>
<td align="center" bgcolor="#f0f0f0">Pass</td>
</tr>
<tr>
<td align="center" bgcolor="#DEE2E7"><strong>50% Load</strong></td>
<td align="center" bgcolor="#f9f9f9">24.5 mV</td>
<td align="center" bgcolor="#f9f9f9">11.4 mV</td>
<td align="center" bgcolor="#f9f9f9">8.6 mV</td>
<td align="center" bgcolor="#f9f9f9">5.1 mV</td>
<td align="center" bgcolor="#f9f9f9">Pass</td>
</tr>
<tr>
<td align="center" bgcolor="#DEE2E7"><strong>60% Load</strong></td>
<td align="center" bgcolor="#f0f0f0">26.1 mV</td>
<td align="center" bgcolor="#f0f0f0">11.5 mV</td>
<td align="center" bgcolor="#f0f0f0">8.7 mV</td>
<td align="center" bgcolor="#f0f0f0">5.3 mV</td>
<td align="center" bgcolor="#f0f0f0">Pass</td>
</tr>
<tr>
<td align="center" bgcolor="#DEE2E7"><strong>80% Load</strong></td>
<td align="center" bgcolor="#f9f9f9">26.6 mV</td>
<td align="center" bgcolor="#f9f9f9">12.1 mV</td>
<td align="center" bgcolor="#f9f9f9">8.8 mV</td>
<td align="center" bgcolor="#f9f9f9">5.8 mV</td>
<td align="center" bgcolor="#f9f9f9">Pass</td>
</tr>
<tr>
<td align="center" bgcolor="#DEE2E7"><strong>100% Load</strong></td>
<td align="center" bgcolor="#f0f0f0">29.8 mV</td>
<td align="center" bgcolor="#f0f0f0">12.9 mV</td>
<td align="center" bgcolor="#f0f0f0">9.2 mV</td>
<td align="center" bgcolor="#f0f0f0">7.3 mV</td>
<td align="center" bgcolor="#f0f0f0">Pass</td>
</tr>
<tr>
<td align="center" bgcolor="#DEE2E7"><strong>110% Load</strong></td>
<td align="center" bgcolor="#f9f9f9">32.1 mV</td>
<td align="center" bgcolor="#f9f9f9">13.0 mV</td>
<td align="center" bgcolor="#f9f9f9">9.9 mV</td>
<td align="center" bgcolor="#f9f9f9">7.8 mV</td>
<td align="center" bgcolor="#f9f9f9">Pass</td>
</tr>
<tr>
<td align="center" bgcolor="#DEE2E7"><strong>Crossload 1</strong></td>
<td align="center" bgcolor="#f0f0f0">19.3 mV</td>
<td align="center" bgcolor="#f0f0f0">12.6 mV</td>
<td align="center" bgcolor="#f0f0f0">8.9 mV</td>
<td align="center" bgcolor="#f0f0f0">7.2 mV</td>
<td align="center" bgcolor="#f0f0f0">Pass</td>
</tr>
<tr>
<td align="center" bgcolor="#DEE2E7"><strong>Crossload 2</strong></td>
<td align="center" bgcolor="#f9f9f9">30.0 mV</td>
<td align="center" bgcolor="#f9f9f9">11.4 mV</td>
<td align="center" bgcolor="#f9f9f9">9.4 mV</td>
<td align="center" bgcolor="#f9f9f9">7.4 mV</td>
<td align="center" bgcolor="#f9f9f9">Pass</td>
</tr>
</table>

Ripple suppression is superb, even with the stress we applied to the PSU during testing. Seasonic has, once again, done an excellent job of assembling a ripple-proof platform that delivers ultra-clean outputs in every case. This means that your sensitive components will only be stressed minimally, which translates into a far more stable operation, even with heavily overlocked system components.

Ripple at Full Load

In the following oscilloscope screenshots, you can see the AC ripple and noise that the main rails registered (+12V, 5V, 3.3V, and 5VSB). The bigger the fluctuations on the oscilloscope's screen, the bigger the ripple/noise. For all measurements, we set 0.01 V/Div (each vertical division/box equals to 0.01 V) as standard.

http://www.techpowerup.com/reviews/S...load_small.jpg http://www.techpowerup.com/reviews/S...load_small.jpg http://www.techpowerup.com/reviews/S...load_small.jpg http://www.techpowerup.com/reviews/S...load_small.jpg

Ripple at 110% Load

http://www.techpowerup.com/reviews/S...load_small.jpg http://www.techpowerup.com/reviews/S...load_small.jpg http://www.techpowerup.com/reviews/S...load_small.jpg http://www.techpowerup.com/reviews/S...load_small.jpg

Ripple at Crossload 1

http://www.techpowerup.com/reviews/S..._cl1_small.jpg http://www.techpowerup.com/reviews/S..._cl1_small.jpg http://www.techpowerup.com/reviews/S..._cl1_small.jpg http://www.techpowerup.com/reviews/S..._cl1_small.jpg

Ripple at Crossload 2

http://www.techpowerup.com/reviews/S..._cl2_small.jpg http://www.techpowerup.com/reviews/S..._cl2_small.jpg http://www.techpowerup.com/reviews/S..._cl2_small.jpg http://www.techpowerup.com/reviews/S..._cl2_small.jpg

Performance Rating

The following graph shows the total performance rating of the PSU in comparison to other units we have tested before. To be more specific, the tested unit is shown as 100% and all other units' performance is relative to it. If you want to know the exact method that we use to calculate the performance rating of each PSU, read this article.

http://www.techpowerup.com/reviews/S...mages/perf.gif

Performance per Dollar

For most of you, the following graph is the most interesting since it shows the performance per dollar of the PSU that you may consider buying. We looked up the current USD price of each PSU on the popular online shop Newegg and used it, along with the relative performance numbers, to calculate the performance-per-dollar index. If Newegg didn't have a stock of a specific unit, we searched for it at other popular online shops (e.g., TigerDirect, Amazon) and, finally, if the unit was not sold in the USA, we searched the product at popular EU shops (e.g., Caseking) and then, if found, converted its price to USD (w/o VAT). Note that, in the following graph, all numbers are normalized by the rated power of each PSU.

http://www.techpowerup.com/reviews/S...perfdollar.gif

Value and Conclusion

<table width="100%" cellpadding="5" cellspacing="0" id="result">
<tr><th>http://www.techpowerup.com/images/dollar.gif</th>
<td>

The Seasonic Platinum Series Fanless 520 W has an MSRP of $149.90

</td><br>
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<th>http://www.techpowerup.com/images/thumbup.gif</th>
<td>

Delivered 110% load at 43°C with 92.5% efficiency
Superb ripple-suppression
Tight voltage-regulation
Highly efficient
Fanless
Japanese (electrolytic) caps are used everywhere
Fully modular
Seven-year warranty

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<th>http://www.techpowerup.com/images/thumbdown.gif</th>
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Only two PCIe connectors
OTP triggering point could be a little higher

</td>
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<tr>
<th>9.3</th>
<td>This is not the first time that a Seasonic product manages to amaze me and it surely won't be the last! The new fanless Platinum 520 W unit is a great performer with ultra-stable rails that deliver very clean outputs. It is highly efficient under severe conditions, utilizes a fully modular cabling system, and its protection features, especially OTP (Over Temperature Protection), work well, which will save the unit from damage if you surpass its limits. Seasonic also made sure to include an extra-long warranty, which is pretty special because the SS-520FL is a fanless unit that will, compared to normal PSUs, operate at increased internal temperatures. The only downside of this unit is that it only comes with two PCIe connectors, which is a weird choice since it could easily handle two additional connectors to support up to two VGAs with double PCIe sockets each. But its modular design does allow for such a problem to be remedied easily with the use of cables that feature two PCIe connectors. Seasonic should look into this matter soon, and they will hopefully realize that having no more than two PCIe connectors greatly restricts this fine PSU's usability. <br/><br/>Your choices are pretty limited if you are looking for a fanless PSU, especially if you seek a Platinum efficiency one. The Seasonic SS-520FL's platform easily allows this unit to confront and eclipse its competition by providing top performance for a price that beats every other fanless Platinum PSU out there, which makes its purchase a no-brainer. </td></tr>
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