Seasonic Platinum Fanless 520 W Power Supply Review

Primary Analysis

On this page, we will take an in-depth look at the primary stage of the Seasonic Platinum Fanless 520 W. For a better understanding, please read our “Anatomy of Switching Power Supplies” tutorial.       

This power supply uses two GBJ2506 rectifying bridges connected in parallel, which are attached to an individual heatsink. Each bridge supports up to 25 A at 100° C. In theory, you would be able to pull up to 5,750 W from a 115 V power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 4,600 W without burning themselves out (or 5,175 W at 90% efficiency). Of course, we are only talking about these particular components. The real limit will depend on all the components combined in this power supply.

Figure 10: Rectifying bridges

The active PFC circuit uses two IPP60R160C6 MOSFETs, each one supporting up to 23.8 A at 25&deg
; C or 15 A at 100° C in continuous mode (note the difference temperature makes), or 70 A at 25° C in pulse mode. These transistors present a 160 mΩ maximum resistance when turned on, a characteristic called RDS(on). The lower the number the better, meaning that the transistor will waste less power, and the power supply will have a higher efficiency.

Figure 11: The active PFC diode and the two active PFC transistors

The active PFC circuit is managed by an NCP1654 active PFC controller.

Figure 12: Active PFC controller

The output of the active PFC circuit is filtered by one 330 µF x 420 V Japanese electrolytic capacitor, from Hitachi, labeled at 105° C.

Figure 13: Capacitor

In the switching section, four IPP50R250CP MOSFETs are employed using a full-bridge, resonant configuration. Each transistor supports up to 13 A at 25° C or 9 A at 100° C in continuous mode or up to 31 A at 25° C in pulse mode, with a maximum RDS(on) of 250 mΩ.

Figure 14: The four switching transistors

The switching transistors are controlled by a CM6901 controller.  

Figure 15: Resonant controller

Let’s now take a look at the secondary of this power supply.