Rocketfish 550 W Power Supply Review

Secondary Analysis

This power supply uses four Schottky rectifiers on its secondary.

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 SBR30A60CT (30 A, 15 A per internal diode at 110° C, typical voltage drop of 0.53 V) connected in parallel. This gives us a maximum theoretical current of 43 A or 514 W for the +12 V output.

By the way, we are now talking about the voltage drop presented by the rectifiers. This parameter shows how much voltage is wasted by the rectifier. The lower this number is, the better, as less voltage is wasted, increasing efficiency.

The +5 V output is produced by one STPS30L30CT Schottky rectifier (30 A, 15 A per internal diode at 140° C, maximum voltage drop of 0.57 V), giving us a maximum theoretical current of 21 A or 107 W for this output.

The +3.3 V output is produced by one STPS3045CW Schottky rectifier (30 A, 15 A per internal diode at 155° C, maximum voltage drop of 0.57 V), giving us a maximum theoretical current of 21 A or 71 W for this 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 12: +12 V rectifier and +3.3 V rectifier.

Figure 13: +5 V rectifier and +12 V rectifier.

The outputs are monitored by an SG6516DZ integrated circuit, which supports under voltage (UVP), over voltage (OVP) and over current (OCP) protections. Any other protection that this unit may have is implemented outside this integrated circuit.

Figure 14: Monitoring integrated circuit.

Most electrolytic capacitors from the secondary are Japanese from Chemi-Con, but some of them are Chinese from Samxon.