Athena Power AP-MFATX40P8 400 W Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of the Athena Power AP-MFATX40P8. For a better understanding, please read our “Anatomy of Switching Power Supplies” tutorial.

This power supply uses one US8K80R rectifying bridge, which is attached to the same heatsink used by one of the switching transistors. This bridge supports up to 8 A at 108° 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 736 W without burning itself out. 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 10: Rectifying bridge

The active PFC circuit uses one SPW32N50C3 MOSFET, which supports up to 32 A at 25° C or 20 A at 100° C in continuous mode (note the difference temperature makes), or up to 96 A in pulse mode at 25° C. These transistors present a 110 mΩ resistance when turned on, a characteristic called RDS(on). The lower this number the better, meaning that the transistors will waste less power, and the power supply will achieve a higher efficiency.

Figure 11: One of the switching transistors, the active PFC diode, and the active PFC transistor

The output of the active PFC circuit is filtered by a 220 µF x 400 V electrolytic capacitor from Yihcon and labeled at 105° C.

In the switching section, two FQPF13N50 MOSFETs are used in the traditional two-transistor forward configuration, supporting up to 13 A at 25° C or 8 A at 100° C in continuous mode, or up to 52 A in pulse mode at 25° C, with an RDS(on) of 480 mΩ.

Figure 12: The other switching transistor

The primary is managed by an omnipresent CM6800 active PFC/PWM controller.

Figure 13: Active PFC/PWM controller

The primary of the 400 W model is identical to the primary of the 350 W model. Let’s now take a look at the secondary of this power supply.