Component Analysis

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



The small PCB is packed with parts on the primary side, but there is enough space between parts on the secondary side. It is always impressive to see such compact power factories. In SFX PSUs, engineers have to increase power output without sacrificing efficiency, reliability, and output noise. The build quality looks good, and as per usual, Seasonic used topnotch parts.


The transient/EMI filter stages have all the necessary parts.


The MOV should be covered in heat shrink to be kept in place if it blows up.


An NTC thermistor provides inrush current protection by lowering start-up currents.


The bridge rectifier is bolted to the primary heatsink, and it is powerful, able to handle up to 25 A.


The APFC converter uses one Infineon FET and a boost diode by the same manufacturer. The bulk cap is by Rubycon and doesn't have enough capacity to provide a hold-up time of over 17 ms.


The APFC controller is a Champion CM6500UNX.


The two main switching FETs are installed in a half-bridge topology, and an LLC resonant converter is used for higher efficiency. The LLC resonant controller is a Champion CU6901VPA, which uses the burst-mode (Champion calls it kick mode) operation for increased efficiency at super-light loads.


The driver IC for the primary switching FETs is a Silicon Labs Si8230BD.


The unit's main transformer isolates the primary and secondary sides, among others.


The FETs regulating the +12 V rail are installed on the solder side of the main PCB.


The few electrolytic caps are of high quality. Seasonic mostly used polymer caps to filter ripple.


Two DC-DC converters generate the minor rails. They are installed on a daughter board that also hosts the fan's header.


The controller handling both DC-DC converters, generating the minor rails, is an ANPEC APW7159C.


The 5VSB circuit uses an EM8671A PWM controller, and the rectifier on the primary side is an Infineon FET.


There are two supervisor ICs, a Weltrend WT7527RA, which handles the usual duties, and a Weltrend WT51F104 microcontroller responsible for the firmware OPP and OTP. The typical hardware OPP is designed to trip at high power spikes lasting for nanoseconds, while firmware OPP handles lower power spikes that last longer, in the millisecond range. Seasonic doesn't advertise this feature, which is odd as it is a notable advantage over competing offerings.


Several polymer caps are installed on the face of the modular PCB.


Soldering quality is good.


The cooling fan is by Hong Hua. It measures 92 mm across and uses a fluid dynamic bearing.