Enermax REVOLUTION85+ 920 W Power Supply Review

Secondary Analysis

This power supply uses a synchronous design in its secondary, meaning that the Schottky rectifiers were replaced by MOSFET transistors in order to increase efficiency. On top of that this unit uses a DC-DC project, meaning that this unit is basically a +12 V power supply, with the +5 V and +3.3 V outputs being generated by two small power supplies attached to the +12 V output.

The +12 V output is generated by six IPP041N04N MOSFETs, each one capable of handling up to 80 A at 100° C in continuous mode, or up to 400 A at 25° C in pulse mode, with an RDS(on) of only 4.1 mΩ. Three are in charge of the direct rectification while three are in charge of the “freewheeling” part of the rectification process. In this power supply the +12 V output is also used to generate the +5 V and the +3.3 V outputs, as you know. As an exercise, if we assume that all load was exclusively pulled from the +12 V output, we would have a maximum theoretical current limit of 343 A or 4,114 W.

The +5 V and the +3.3 V outputs are generated by two small power supplies available on small daughterboards attached to the +12 V rail. Each of these power supplies is comprised of three APM2556N MOSFETs (60 A at 25° C or 48 A at 100° C, 7.5 mΩ resistance) and one APW7073 PWM controller. They use solid capacitors.

The outputs are monitored by a PS232S integrated circuit that is soldered on the printed circuit board shown in Figure 20. This circuit supports over voltage (OVP), under voltage (UVP) and over current (OCP) protections. This circuit offers six over current protection channels (one for +3.3 V, one for +5 V and four for +12 V), correctly matching the number of +12 V rails advertised by the manufacturer (four).

The electrolytic capacitors available in the secondary are also Japanese, from Chemi-Con, and labeled at 105° C.