Cooler Master GX 750 W Power Supply Review

Secondary Analysis

This power supply has eight 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 four PFR60L60CT Schottky rectifiers, each one supporting up to 60 A (30 A per internal diode at 120° C, 0.65 V maximum voltage drop), giving us a maximum theoretical current of 171 A or 2,057 W for the +12 V output. That’s what we call overspecification!

The +5 V output is produced by two PFR30V30CT Schottky rectifiers, each one supporting up to 30 A (15 A per internal diode at 120° C, 0.45 V maximum voltage drop), giving us a maximum theoretical current of 43 A or 214 W.

The +3.3 V output is produced by another two PFR30V30CT Schottky rectifiers, giving us a maximum theoretical current of 43 A or 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.

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

The outputs are monitored by a PS113 integrated circuit, which supports only OVP (over voltage protection) and SCP (Short-Circuit Protection). Any other protection this power supply may have is implemented outside this circuit. In fact this unit has two thermistors. When this configuration is used it usually means the unit has over temperature protection (OTP).

Figure 12: Monitoring circuit.

All capacitors from the secondary are also from Su’scon.