A Look Inside

Before reading this page we strongly suggest to take a look at this article, which will help you understand the internal components of a PSU much better.


The OEM of AX850 is Seasonic. On the main PCB we find several pretty small heatsinks. You see these Gold PSUs have very low energy losses, thus operational temperatures are kept low and there is no need for large heatsinks.


The AC receptacle incorporates a Yun Pen EMI line filter which includes all necessary components (one X, two Y capacitors and two coils). On the main PCB there are one X and two Y capacitors, two coils and an MOV. There is also a thermistor along with an electromagnetic relay which bypasses it once the PSU starts to minimize energy losses and to allow it also to cool down. Near the relay and the thermistor resides an ICE2QR4765 Quasi-Resonant PWM Controller, which handles the standby mode of the PSU.


The bridge rectifiers, two GBU1506, are cooled passively by a heatsink. In APFC three mosfets (60R160C6) separate the intermediate DC voltage coming from the bridge rectifiers into constant pulse sequences. As boost diode a C3D08060A is used. The two parallel smoothing/reservoir capacitors are provided by Nippon Chemi-Con (420V, 390μF, 105°C, KMR). The main switches are two 60R160C6 mosfets. The PSU utilizes an LLC-resonant converter to achieve higher efficiency, and the resonant controller is a CM6901 which is housed on a vertical daughter-board right next to the resonant inductor. This controller operates the main switches in PWM mode at light loads and in FM mode at higher loads. Seasonic chose not to use an integrated transformer so two transformers are used in the resonant converter along with the main transformer.


In the secondary we find several smaller heatsinks that cool the mosfets (four IPD031N06L) used for the +12V generation. These mosfets reside on the solder side of the main PCB and are also cooled from the casing through a thermal pad. The minor rails are generated from +12V with the use of two DC-DC converters. The latter are housed on the modular PCB, in order to minimize the distance that current has to travel and thus effectively decrease energy losses. Both converters use an APW7159 PWM controller and four PD060N03L mosfets. In the secondary side and on the modular PCB we meet many polymer capacitors, something that guarantees top performance along with increased life time. One of the few electrolytic capacitors we found is used in 5VSB regulation and it's provided from Nippon Chemi-Con too.


The protections of the PSU handles a PS223, which is added by an LM393 Dual Voltage Comparator.


Soldering quality and workmanship in general is very high.


The cooling fan is a San Ace 120 by SANYO DENKI (model number: 9S1212F404).