Enermax ECO80+ 620 W Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of Enermax ECO80+ 620 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBU15J rec
tifying bridge in its primary, which can deliver up to 15 A at 100° C. This component is clearly overspec’ed: at 115 V this unit would be able to pull up to 1,725 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 1,380 W without burning this component. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.

Figure 10: Rectifying bridge.

On the active PFC circuit two IRFP460A power MOSFET transistors are used, each one capable of delivering up to 20 A at 25° C or 13 A at 100° C in continuous mode (note the difference temperature makes), or up to 80 A in pulse mode at 25° C. These transistors present a resistance of 270 mΩ when turned on, a characteristic called RDS(on). This number indicates the amount of power that is wasted, so the lower this number the better, as less power will be wasted thus increasing efficiency.

This power supply uses two electrolytic capacitors to filter the output from the active PFC circuit. The use of more than one capacitor here has absolute nothing to do with the “quality” of the power supply, as laypersons may assume (including people without the proper background in electronics doing power supply reviews around the web). Instead of using one big capacitor, manufacturers may choose to use two or more smaller components that will give the same total capacitance, in order to better accommodate space on the printed circuit board, as two or more capacitors with small capacitance are physically smaller than one capacitor with the same total capacitance. On ECO80+ 620 W two 220 µF x 400 V capacitors are used in parallel; this is equivalent of one 440 µF x 400 V capacitor.

These capacitors are Japanese, from Chemi-Con and are labeled at 85° C.

In the switching section, another two IRFP460A power MOSFET transistors are used on the traditional two-transistor forward configuration.

Figure 11: Active PFC transistor, active PFC diode, switching transistor and standby (+5VSB) switching transistor.

The primary is controlled by a CM6802 PFC/PWM combo controller, which is an updated version from the famous CM6800 controller.

Figure 12: PFC/PWM combo controller.

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