Spire BlackDragon 400 W Power Supply Review

Secondary Analysis

The Spire BlackDragon 400 W uses a regular design in its secondary, with Schottky rectifiers.

The maximum theoretical current that 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 two PFR30L60CT Schottky rectifiers, each supporting up to 30 A (15 A per internal diode at 110° C, maximum voltage drop of 0.60 V), giving us a maximum theoretical current of 43 A or 514 W for this output.

The +5 V output uses one PFR30V30CT Schottky rectifier, which supports up to 30 A (15 A per internal diode at 90° C, maximum voltage drop of 0.44 V), giving us a maximum theoretical current of 21 A or 257 W for this output.

The +3.3 V output uses two PFR30V45CT Schottky rectifiers, each supporting up to 30 A (15 A per internal diode at 110° C, maximum voltage drop of 0.47 V), giving us a maximum theoretical current of 43 A or 141 W for this output.

Figure 16: The +3.3 V, +5 V, and +12 V rectifiers

The outputs of the power supply are monitored by a WT7502 integrated circuit, which only provides over voltage (OVP) and under voltage (UVP) protections.

Figure 17: Monitoring circuit

The electrolytic capacitors available in the secondary are also from CapXon, and labeled at 105° C, as usual.

Figure 18: Capacitors