Aerocool E85M-550 Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of the Aerocool E85M-550. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one PBU1005 rectifying bridge on its primary, and it is connected to an individual heatsink. This component 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 al
low this unit to deliver up to 920 W without burning itself out. Of course, we are only talking about these components, and the real limit will depend on all the other components in this power supply. This is exactly the same component used in the Aerocool V12XT-600.

Figure 10: Rectifying bridge

The active PFC circuit uses two FDP18N50 MOSFETs, each one capable of delivering up to 18 A at 25° C or up to 10.8 A at 100° C in continuous mode (note the difference temperature makes), or up to 72 A in pulse mode at 25° C. These transistors present a 265 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 have a higher efficiency. The Aerocool V12XT-600 uses more powerful transistors here (20.7 A at 25° C, or 13.1 A at 100° C), which present a lower RDS(on) (190 mΩ).

Figure 11: Active PFC transistors and diode

The electrolytic capacitor used to filter the output of the active PFC circuit is from CapXon and labeled at 85° C.

In the switching section, another two FDP18N50 power MOSFET transistors are used in the traditional two-transistor forward configuration. The specs for these transistors were already published above. The Aerocool V12XT-600 again uses more powerful transistors here (20.7 A at 25° C, or 13.1 A at 100° C), which present a lower RDS(on) (190 mΩ).

Figure 12: One of the switching transistors

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

Figure 13: Active PFC/PWM combo controller

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