Enermax REVOLUTION85+ 920 W Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of Enermax REVOLUTION85+ 920 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses two GBU15J rectifying bridges connected in parallel on its primary, and they are connected to a heatsink. Each bridge supports up to 15 A at 100° C, so in theory, you would be able to pull up to 3,450 W from the power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 2,760 W without burning themselves 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.

The active PFC circuit uses two TK20J60U MOSFETs, each one capable of delivering up to 20 A at 25° C in continuous mode (unfortunately the manufacturer doesn’t say the current limit at 100° C) or 40 A in pulse mode at 25° C. These transistors present a 165 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.

The active PFC circuit is controlled by a CM6502 integrated circuit.

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. The Enermax REVOLUTION85+ 920 W uses two 330 µF x 450 V capacitors connected in parallel; this is the equivalent of one 660 µF x 450 V capacitor.

These capacitors are Japanese, from Rubycon, and are labeled at 85° C.

In the switching section, another two TK20J60U power MOSFET transistors are used. The specs for these transistors were already published above.

The switching transistors are connected using a design called “LLC resonant,” also known as a series parallel resonant converter, being controlled by a CM6901 integrated circuit, which operates under PWM (Pulse Width Modulation) mode when the power supply is operating under light load but under FM (Frequency Modulation) mode under other loads. This is the same design used in the MODU87+ power supply series from the same manufacturer.

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