This power supply uses four Schottky rectifiers on its secondary (ST-750P-AF has six).

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 STPS60L45CW Schottky rectifiers, each one capable of delivering up to 60 A (30 A per internal diode at 135º C, maximum voltage drop of 0.50 V). This gives us a maximum theoretical current of 86 A or 1,029 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 KCQ60A04 Schottky rectifier (60 A, 30 A per internal diode at 83º C, maximum voltage drop of 0.58 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 KCQ60A04 Schottky rectifier, so the maximum theoretical power this output can deliver is of 141 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.

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Figure 11: +3.3 V, +5 V and +12 V rectifiers.

The outputs are monitored by a PS223 integrated circuit, which supports under voltage (UVP), over voltage (OVP), over current (OCP) and over temperature (OTP, not implemented on this power supply) protections. Any other protection that this unit may have is implemented outside this integrated circuit.

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Figure 12: Monitoring circuit.

Electrolytic capacitors from the secondary are Chinese from Samxon and labeled at 105º C.