Amacrox Free Earth 88PLUS 600 W Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of the Amacrox Free Earth 88PLUS 600 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses three GBU1006 rectifying bridges connected in parallel, each one supporting up to 10 A at 100° C. The bridges aren’t connected to a heatsink and the datasheet for the bridges doesn’t give the current limit for this piece. In theory, you would be able to pull up to 3,450 W from a 115 V power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 2,760 W without burning themselves out. Talk about over-specification! Of course we are only talking about these components, and the real limit will depend on all the other components in the power supply.

Figure 10: Rectifying bridges

The active PFC circuit uses two FCPF21N60NT MOSFETs, each one capable of delivering up to 20 A at 25° C, up to 12.5 A at 100° C in continuous mode (note the difference temperature makes), or up to 60 A in pulse mode at 25° C. These transistors present a 150 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: Active PFC transistors and diode

The electrolytic capacitor used to filter the output of the active PFC circuit is Japanese, from Matsushita (Panasonic), and labeled at 105° C.

In the switching section, two IPI60R125CP power MOSFET transistors are used in the traditional two-transistor forward configuration, each one supporting up to 25 A at 25° C, up to 16 A at 100° C in continuous mode, or up to 82 A at 25° C in pulse mode, presenting an RDS(on) of 125 mΩ.

Figure 12: Switching transistors

The primary is controlled by a CM6802 active PFC/PWM combo.

Figure 13: Active PFC/PWM combo controller

Now let’s take a look at the secondary of this power supply.