Seasonic G-550 Power Supply Review

Primary Analysis

On this page, we will take an in-depth look at the primary stage of the Seasonic G-550. For a better understanding, please read our “Anatomy of Switching Power Supplies” tutorial.

This power supply uses one GBU10JL rectifying bridge, which is attached to an individual heatsink. This bridge supports up to 10 A at 100° C. In theory, you would be able to pull up to 1,150 W from a 115 V power grid. Assuming 80% efficiency, the bridge would allow this unit to deliver up to 1,380 W without burning itself out (or 1,553 W at 90% efficiency). Of course, we are only talking about this particular component. The real limit will depend on all the components combined in this power supply. This is exactly the same bridge used in the 360 W model.

Figure 11: Rectifying bridge

The active PFC circuit uses two SPP20N60C3 MOSFETs, which support up to 20.7 A at 25° C or 13.1 A at 100° C in continuous mode (note the difference temperature makes) or 62.1 A at 25° C in pulse mode. These transistors present a 190 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 12: The active PFC transistors and diode

The active PFC circuit is managed by an ICE3PCS01 active PFC controller.

The output of the active PFC circuit is filtered by one 390 µF x 420 V Japanese electrolytic capacitor, from Chemi-Con, labeled at 105° C.

Figure 13: Capacitor

In the switching section, two FDP18N50 MOSFETs are employed using a resonant configuration. Each transistor supports up to 18 A at 25° C or 10.5 A at 100° C in continuous mode or up to 72 A at 25° C in pulse mode, with a maximum RDS(on) of 265 mΩ.

Figure 14: The switching transistors

The switching transistors are controlled by an ICE2HS01G resonant controller.

Figure 15: Resonant controller (left) and active PFC controller (right)

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