Ultra X4 850 W Power Supply Review

Secondary Analysis

This power supply has nine Schottky rectifiers attached to its secondary heatsink.

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 four ESAE83-004 Schottky rectifiers, each one providing up to 60 A (30 A per internal diode at 110° C, maximum voltage drop of 0.55 V). This gives us a maximum theoretical current of 171 A or 2,057 W. That is what we call overspecification!

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 two SPR30L30CT Schottky rectifiers connected in parallel (30 A, 15 A per internal diode at 125° C, typical voltage drop of 0.38 V), giving us a maximum theoretical current of 43 A or 214 W for this output.

The +3.3 V output is produced by another two SPR30L30CT Schottky rectifiers, so the maximum theoretical power this output can deliver is of 141 W.

The ninth rectifier, an STPS20L60CT (20 A total, 10 A per diode at 140° C, maximum voltage drop of 0.56 V), is used by the standby (+5VSB) 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: Rectifiers.

The outputs are monitored by a PS232 integrated circuit, which supports the following protections: over current (OCP), under voltage (UVP) and over voltage (OVP). Any other protection that this unit may have is implemented outside this integrated circuit.

Figure 14: Monitoring circuit.

Electrolytic capacitors from the secondary are from Teapo and labeled at 105° C.