Seventeam ST-650PWL Power Supply Review

Secondary Analysis

This power supply has eight Schottky rectifiers on its secondary heatsink, all the same model: PFR30V45CT. Each one supports up to 30 A (15 A per internal diode at 120° C, 0.45 V maximum voltage drop).

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%.

The +12 V output uses four of those rectifiers, giving us a maximum theoretical current of 86 A or 1,029 W for the +12 V output.

The +5 V output uses two of those rectifiers, giving us a maximum theoretical current of 43 A or 214 W for the +5 V output.

The +3.3 V output uses the other two rectifiers, giving us a maximum theoretical current of 43 A or 141 W for the +3.3 V output.

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 13: +3.3 V, +5 V and +12 V rectifiers

The secondary is monitored by a PS113 integrated circuit, which supports only over voltage (OVP) and  under voltage (UVP) protections.

Figure 14: Monitoring circuit

All electrolytic capacitors used in this power supply are also from Su’scon and labeled at 105° C.