Seasonic Platinum Series Fanless 520 W

Seasonic Platinum Series Fanless 520 W

Voltage Regulation, Hold-up Time & Inrush Current »

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.


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.


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.


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


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.


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.


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.


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.


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.


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.


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.
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