A Look Inside

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 G-550 utilizes a rather modern platform to achieve Gold efficiency and good performance, despite its budget price. As it seems, Seasonic managed to drastically cut the production cost on these units, something that allowed for a lower pricing-scheme compared to the Gold X series units. On the primary side of the G-550, we meet an LLC resonant converter for increased efficiency. The secondary side uses DC-DC converters with a semi-synchronous design for the rectification of the main rails. Also, lots of polymer filtering caps are used.


Behind the AC receptacle is a small PCB holding four Y caps, one X cap, and a CM choke. On the main PCB, we find two additional CM chokes, two Y caps, a single X cap, and an MOV.


A leaning dedicated heatsink passively cools the single bridge rectifier, a GBU10JL that can handle up to 10 A of current.


In the APFC, two Infineon SPP20N60C3 fets and a CREE C3D06060A boost diode are used. The hold-up cap is provided by Nippon Chemi-Con (390μF, 420V, 105°C, KMR series). Right in front of it is the thermistor responsible for protection against large inrush currents.


This vertical daughter-board houses an ICE2HS01G resonant controller (large IC on the left) and an ICE3PCS01 PFC controller (small IC on the right)


As primary switchers two MagnaChip MDF18N50 fets are used.


On the secondary side, a semi-synchronous rectification scheme is utilized since two PSMN2R6-40YS fets and two SBR10U45 Schottky diodes rectifying the +12V rail are installed on the solder side of the main PCB. A heatsink on the component side helps in lowering their operational temperature. Finally, the minor rails are generated by two DC-DC converters.


On the secondary side, we find many filtering polymer caps provided by Enesol and several electrolytic Chemi-Cons (105°C, KZH series).


The standby PWM controller is an Infineon ICE2QR4765 IC. The Schottky diode responsible for the rectification of the 5VSB rail is an SBR10U45 and is located on the solder side of the main PCB.


Housekeeping is done by a SITI PS223 which is among the very few monitoring ICs that support OTP (Over Temperature Protection) out of the box.


On the front of the modular PCB, we meet four Chemi-Con caps that provide some extra ripple filtering to the outputs.


Soldering quality on the main PCB is not up to the levels of the X series PSUs, but it is, especially for a mid-range unit, still quite good. We didn't spot any long component leads.


The cooling fan is provided by ADDA and its model number is AD1212MB-A70GL (120mm, 12V, 0.33 A, 2050 RPM max). It uses ball bearings and can be expected to have a longer lifespan than a sleeved-bearing fan.