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.


Once we removed the casing the platform looked familiar and this is because we have recently met a modified version of it in the Be Quiet Dark Power Pro 10 550W. It uses a modern design since a half bridge topology along with an LLC converter is used in the primary side while in the secondary we meet synchronous rectification and VRMs for the generation of the minor rails. In an effort to avoid the use of wires to transfer power to the modular sockets, FSP didn't use a modular PCB but soldered the few sockets directly on the main PCB.


Before we start analyzing components let's take a look at the enclosure of the unit. On its bottom we find many thermally conductive pads which help to transfer the heat from the PCB and its components to the casing, which acts as a big heatsink. The top of the case looks empty without a fan installed and on the last of the photos you can see one of the clips that hold the two plastic trims that surround the top exhaust grill.


The EMI or transient filtering stage starts at the AC receptacle with two Y and one caps, which is equipped with the necessary bleeding resistor to discharge it quickly, once power is cut. On the main PCB we find the remaining components of the transient filtering stage, two CM chokes, one X cap and two Y ones and an MOV. There is also a thermistor responsible for protection against large inrush currents during the start up phase of the PSU and a relay that isolates it from the circuit once the PSU starts.


The bridge rectifier is cooled by a large dedicated heatsink. Its model number is LL25XB60 and can handle up to 25A of current so it is overspecced for the mere 500W capacity of this PSU.


In the APFC we find three STF22NM60N fets and a C3D04060 boost diode. The two parallel hold up caps are provided by the widely known Nippon Chemi-Con (450V, 220μF, 105°C, KMR series). In order to take a look at the main switchers we had to remove one of the APFC caps.


Both the PFC and LLC controllers are installed on small vertical PCBs. The first is an NCP1654B IC while the second is a Champion CM6901T2X IC.


The standby PWM controller is a TNY280PN IC which is soldered directly to the main PCB.


This is the resonant tank of the LLC converter and the two caps next to the main transformer form the capacitor part of the LLC circuit.


In the secondary side we find three heatsinks which remind us of the ones that Seasonic uses in their X series PSUs. The mosfets responsible for +12V rectification are installed on the solder side of the PCB and the aforementioned three heatsinks help in removing the heat from them. The filtering caps consist of several polymer Capxons and some electrolytic Nippon Chemi-Cons (105°C, KZE series).


The VRMs that generate the minor rails are installed on this PCB. As you can see there are two metal shields around them to restrict EMI transmissions. It seems they are not fed with power through the main PCB but instead two wires transfer +12V and ground to them. Or maybe these wires are supplementary since they are not so thick for the 100W max combined power that the minor rails can deliver.


The protections IC is installed on a large daughter-board, residing on the secondary side. Its model number is GR8323N and this is the first time we meet this specific IC in a PSU. From its specifications we found out that it supports OCP for up to two +12V virtual rails, matching the rails that this PSU has.


The few modular sockets are soldered directly to the main PCB, in an effort to minimize energy dissipation, provide lower voltage drops at high loads and of course increase efficiency. In small capacity units where few modular sockets are needed this is a feasible solution, but in higher capacity PSUs a modular PCB is essential for the housing of all modular sockets.


Soldering quality on the main PCB overall is very good, yet not perfect since we spotted a few blobby solder joints, which however don't pose any threat to the unit's performance and reliable operation. The fets responsible for +12V rectification are installed on this side and they are four Infineon IPD036N04L.