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 much better. Our main tool for the disassembly of the PSU is a Thermaltronics TMT-9000S soldering and rework station. It is of extremely high quality and is equipped with the matching soldering gun. With such equipment in hand, breaking apart every PSU is like a walk in the park!


The new SS-460FL utilizes Seasonic's fresh KM3 platform, so it does, now, amongst other things, offer Platinum instead of Gold efficiency. The last time we took a look at this platform was with our SS-520FL review. The primary side uses a full bridge topology along with an LLC resonant converter for the highest possible efficiency, while synchronous rectification is utilized with two DC-DC converters on the secondary side. The latter generate the minor rails and are installed on the modular PCB for reduced energy dissipation. The most noticeable difference between the KM2 (the platform that the old X-460FL used) and KM3 platform is the relocation of the +12V mosfets from the solder side of the main PCB to a daughter-board, which allows for more efficient cooling. The well-educated PSU user will probably point to the full-bridge topology upgrade on the primary side as the most significant, since it leads to even higher efficiency.


The transient filtering stage starts right at the AC receptacle. Four Y caps, a CM choke, a single X cap, and a fuse are housed on a small PCB. The transient filtering stage continues on the main PCB with two CM chokes, two pairs of X and Y caps, and an MOV. There is also an NTC thermistor for protection against large inrush currents and the corresponding electromagnetic relay that cuts it off the circuit once the startup phase finishes and the APFC cap is fully charged.


The parallel bridge rectifiers are two GBJ 1506 ones. They are quite powerful for the mere 460 W that this PSU can deliver at full load and can, combined, handle up to 30 A of current.


Two Infineon IPP60R199CP fets with 0.199 Ohm max RDS(on) and a SCS106AG boost diode are used in the APFC. The hold-up cap is provided by Nippon Chemi-Con (420 V, 270 μF, KMR series) 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 uses with their high-end platforms.


The main switchers are four Infineon IPP50R399CP fets arranged into a full-bridge topology. They are backed up by an LLC resonant converter, which provides loss-less switching for increased efficiency.


The standby Quasi-Resonant PWM Controller is an ICE2QR4765 IC. The same is used on all high-end Seasonic Gold and Platinum units.


The fets that rectify +12V along with the LLC resonant controller, a Champion CM6901 IC, are installed on this daughter-board. As you can see, two heatsinks handle the cooling of the aforementioned fets, and a thermistor has been attached to the top. The latter provides temperature data to the OTP circuit. Unfortunately, no thermal paste was applied between the heatsinks or to the thermistor, so we added some before reassembling the PSU. Several Enesol polymer caps, some Nippon Chemi-Con electrolytic caps (105°C, KZE series), and a single Rubycon cap filter this rail.


The minor rails are generated by two DC-DC converters, with the latter having been installed directly onto the modular PCB for reduced energy losses. Both are controlled by an APW7159 PWM controller, and each one uses three RJK0332DPB fets. A small heatsink is attached to the rear side of the modular panel for more efficient cooling to the fets. The front side of this board has many Korean-made Enesol filtering caps.


A Weltrend WT7527 handles housekeeping duties and is installed on a small daughter-board located on the secondary side, along with an LM339 quad-voltage comparator. The WT7527 can support up to two +12V virtual rails, but only one exists in this PSU.


Soldering quality on the main PCB is impeccable, with clean and nice solder joints. Seasonic's products enjoy high overall manufacturing quality, so we are used to such high levels of workmanship when we examine the internals of their products, especially their high-end ones. The only thing we don't like so much is the sometimes excessive use of glue on the component side of the PCB. It may be practical but it doesn't look good. Glue was, thankfully, only applied to necessary components this time.