Secondary Analysis
Contents
This power supply uses four Schottky rectifiers on its secondary, all the same model: S30D40C (30 A, 15 A per internal diode at 125° C, maximum voltage drop of 0.65 V). The main difference between Rosewill Green Series 630 W and Performance 650 W lies here. Even though on the Performance 650 W sample we’ve got most components were scratched, we can definitely say that at least the +5 V and +3.3 V rectifiers had inferior current limits (the +3.3 V output used a 20 A rectifier). So this 630 W model is, at least in theory, more powerful than this 650 W model.
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 of the rectifiers, giving us a maximum theoretical current of 43 A or 514 W.
The +5 V output is produced by one of the rectifiers, giving us a maximum theoretical current of 21 A or 107 W.
The +3.3 V output is produced by the last rectifier, giving us a maximum theoretical current of 21 A or 71 W.
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, +5 V and +3.3 V rectifiers.
The outputs are monitored by a WT7510 integrated circuit, which supports only under voltage (UVP), over voltage (OVP) protections. Any other protection that this unit may have is implemented outside this integrated circuit. Notice how the printed circuit board shown in Figure 13 has space for the installation of another integrated circuit, probably supporting the protections that are missing.
Figure 13: Monitoring circuit.
Electrolytic capacitors from the secondary are also from Teapo and labeled at 105° C.