Rosewill CAPSTONE-550M Power Supply Review

Primary Analysis

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

This power supply uses one GBU806 rectifying bridge, which is attached to the same heatsink as the active PFC and switching transistors. This bridge supports up to 8 A at 100° C. So, in theory, you would be able to pull up to 920 W from a 115 V power grid. Assuming 80% efficiency, the bridge would allow this unit to deliver up to 726 W without burning itself out. (Or 828 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.

Figure 9: Rectifying bridge

The active PFC circuit uses one IPW60R165CP MOSFET. This transistor supports up to 21 A at 25° C or 13 A at 100° C in continuous mode (see the difference temperature makes) or up to 61 A at 25° C in pulse mode. This transistor p
resents a 165 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.

The active PFC circuit is controlled by an NCP1653A integrated circuit.

Figure 10: Active PFC controller

The output of the active PFC circuit is filtered by one 390 µF x 400 V Japanese electrolytic capacitor, from Chemi-Con, labeled at 85° C.

In the switching section, two IPA50R250CP MOSFETs are used in a resonant configuration. Each supports up to 13 A at 25° C or 9 A at 100° C in continuous mode or 31 A at 25° C in pulse mode, with a maximum RDS(on) of 250 mΩ.

Figure 11: Active PFC transistors, active PFC diode, and one of the switching transistors

The switching transistor is managed by an SF29601 resonant controller, which is a custom solution from Super Flower. This integrated circuit is located in the secondary and also provides the necessary protection circuitry.

Figure 12: Resonant controller

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