Enermax NAXN 82+ 550 W Power Supply Review

Secondary Analysis

The Enermax NAXN 82+ 550 W uses a regular design in its secondary, with Schottky rectifiers.

The maximum theoretical current each line can deliver is given by the formula I / (1 – D) where D is the duty cycle used and I is the maximum current supported by the rectifying diode. As an exercise, we can assume a duty cycle of 30 percent.

The +12 V output uses three SBR40U60CT Schottky rectifiers (40 A, 20 A per internal diode at 100° C, 0.60 V maximum voltage drop), which gives us a maximum theoretical current of 86 A or 1,029 W for this output. The NAXN 80+ 600 W uses three 30 A rectifiers here, but the maximum theoretical current and power are the same.

The +5 V output uses one SBR30U30CT Schottky rectifier (30 A, 15 A per internal diode at 140° C, 0.54 V maximum voltage drop), which gives us a maximum theoretical current of 21 A or 107 W for this output. The NAXN 80+ 600 W uses two of these rectifiers instead of only one, thus having double the maximum theoretical current and power.

The +3.3 V output uses one STPS40L45CW Schottky rectifier (40 A, 20 A per internal diode at 130° C, 0.70 V maximum voltage drop), which gives us a maximum theoretical current of 29 A or 94 W for this output. This component is a lower voltage drop version of the one used in the NAXN 80+ 600 W.

Figure 14: The +5 V rectifier and two of the +12 V rectifiers

Figure 15: One of the +12 V rectifiers and the +3.3 V rectifier

This power supply uses an ST9S429 monitoring integrated circuit, which apparently is a rebranded S3515. This chip supports over voltage (OVP), under voltage (UDP), and over current (OCP) protections. There are two +12 V OCP channels, matching the number of +12 V rails advertised by the manufacturer.

Figure 16: Monitoring circuit

The electrolytic capacitors that filter the outputs are also from Samxon and are labeled at 105° C, as usual.