Primary Analysis

On this page we will take an in-depth look at the primary stage of the Enermax NAXN 80+ 600 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBU1006 rectifying bridge in its primary, which is attached to an individual heatsink. This bridge supports up to 10 A at 100° C, so 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 920 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.

Enermax NAXN 80+ 600 W power supplyFigure 10: Rectifying bridge

The active PFC circuit uses two MDF18N50 MOSFETs, each one supporting up to 18 A at 25° C or 11 A at 100° C in continuous mode (note the difference temperature makes), or up to 72 A at 25° C in pulse mode. This transistor presents a 270 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.

Enermax NAXN 80+ 600 W power supplyFigure 11: Active PFC transistors and diode

The electrolytic capacitor that filters the output of the active PFC circuit is from Samxon and labeled at 85° C.

In the switching section, another two MDF18N50 MOSFETs are used in the traditional two-transistor forward configuration. The specifications for these transistors were already posted above.

Enermax NAXN 80+ 600 W power supplyFigure 12: Switching transistors

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

Enermax NAXN 80+ 600 W power supplyFigure 13: Active PFC/PWM combo controller

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

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