Cooler Master eXtreme Power Plus 400 W Power Supply Review

Secondary Analysis

This power supply has four Schottky rectifiers on its secondary and an LM7912 voltage regulator in charge of the -12 V output.

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. Just as an exercise, we can assume a typical duty cycle of 30%.

The +12 V output is produced by two SBR20100CT Schottky rectifiers, each one supporting up to 20 A (10 A per internal diode at 150° C, 0.82 V maximum voltage drop), giving us a maximum theoretical current of 29 A or 343 W for the +12 V output. Both 460 W and 500 W models use rectifiers with the same specs.

The +5 V output is produced by one STPS3045CT Schottky rectifier, which supports up to 30 A (15 A per internal diode at 150° C, 0.84 V maximum voltage drop), giving us a maximum theoretical current of 21 A or 107 W for the +5 V output. The 460 W and 500 W models use two 20 A rectifiers connected in parallel here.

The +3.3 V output is produced by another STPS3045CT Schottky rectifier, giving us a maximum theoretical current of 21 A or 71 W for the +3.3 V output. The 460 W and 500 W models use two 20 A rectifiers connected in parallel here.

All these numbers are theoretical. The real amount of current/power each output can deliver is limited by other components, especially by the coils used on each output.

Figure 12: -12 V voltage regulator, +3.3 V, +5 V and +12 V rectifiers.

The outputs are monitored by a WT7527 integrated circuit, which supports OVP (over voltage protection), UVP (under voltage protection) and OCP (over current protection). This circuit has four over current channels. Additionally this power supply has an LM339 integrated circuit (which has four voltage comparators inside) for other protections.

Figure 13: Monitoring integrated circuit.

Figure 14: Monitoring integrated circuit.

The electrolytic capacitors from the secondary are from Ltec.