Athena Power AP-MFATX35 350 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-MFATX35. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one US8K80R rectifying bridge in its primary, which is attached to the same heatsink used by one of the switching transistors. This component 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 component, and the real limit will depend on all the other components 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 at 25° C in pulse mode. This transistor presents a 110 mΩ resistance when turned on, a
characteristic called RDS(on). The lower this number the better, meaning that the transistor will waste less power, and the power supply will have a higher efficiency.

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

The electrolytic capacitor that filters the output of the active PFC circuit is from Yihcon and is labeled at 105° C.

In the switching section, two FQPF13N50C MOSFETs are used in the traditional two-transistor forward configuration, each supporting up to 13 A at 25° C or 8 A at 100° C in continuous mode, or up to 52 A at 25° C in pulse mode, with an RDS(on) of 480 mΩ.

Figure 12: The other switching transistor

The primary is controlled by the popular CM6800 active PFC/PWM combo controller.

Figure 13: Active PFC/PWM combo controller

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