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.


Like the older AX850 and AX750 PSUs, the fresh AX860 and AX760 are made by Seasonic. A ton of experience in this field, given that they have been around since 1976, makes them one of the best OEMs around. The new platform is significantly different to the older Golden efficiency one. The first time we came across this new platform was with the Seasonic SS-520FL PSU, which we reviewed a while ago. The primary side uses a full-bridge topology with an LLC converter for increased efficiency through loss-less switching, while synchronous rectification and two DC-DC converters, located on the modular PCB for decreased energy loses, are utilized on the secondary side.


The first part of the transient filtering stage is housed on a small PCB right behind the AC receptacle. It is completely covered up by a metal shield for EMI suppression. Four Y caps, a CM choke, and a single X cap are there as well, and the main PCB holds two more CM chokes, two pairs of X and Y caps, and an MOV. An NTC thermistor has also been installed on this PCB; it protects against large inrush currents with the help of an electromagnetic relay. The standby Quasi-Resonant PWM Controller is located on the right of the relay and is an ICE2QR4765 IC.


The two parallel bridge rectifiers are two GBJ1506. They are quite powerful for this unit since each one can handle up to 15 A of current for a combined maximum of 30 A.


Two Infineon IPP60R199CP fets and a Cree C3D06060 boost diode are used in the APFC circuit. The two parallel hold-up caps are provided by Nippon Chemi-Con (400 V; 330 μF each or 660 μF combined; 105°C; KMR series).


This small PCB houses the PFC controller, an NPC1654 IC.


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


All +12V fets and the LLC resonant controller, a Champion CM6901 IC, are installed on a vertical PCB located on the secondary side. As you can see, two heatsinks handle the cooling of the +12V fets and a thermistor is attached on top of one to, most likely, provide information to the fan-speed circuit. Finally, a series of Enesol polymer caps and several Nippon Chemi-Con electrolytic caps (105°C, KZE series) filter the +12V rail.


The DC-DC converters are installed directly onto the modular PCB in order to minimize energy losses from power transfers to the modular sockets through wires. Both are controlled by an APW7159 PWM controller and each one uses three Infineon BSC0906NS fets. Many Enesol polymer caps are soldered onto the front for extra ripple-filtering purposes.


The supervisor IC, a Weltrend WT7527, can be found on this vertical PCB along with an LM393 dual-voltage comparator. The WT7527 supports OCP for up to two +12V virtual rails, but only one exists in this PSU.


Soldering quality on the main PCB is very good and all component leads are, to our delight, carefully trimmed.


The cooling fan (San Ace 120) is of high quality and is provided by Sanyo Denki. It uses double ball-bearings and its model number is 9S1212F404 (12 V, 0.19 A, 2.200 RPM, 70.6 CFM). Exactly the same fan was used on the previous AX750 and AX850 models, and there was no reason for a change since it did its job very well.