Cooler Master GX 450 W Power Supply Review

Secondary Analysis

The Cooler Master GX 450 W has four 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. As an exercise, we can assume a duty cycle of 30%.

The +12 V output uses one STPS30L60CW Schottky rectifier for its direct rectification (30 A, 15 A per internal diode at 130° C, 0.75 V maximum voltage drop) and one 40CPQ060 Schottky rectifier for the “freewheeling” part of the rectification (40 A, 20 A per internal diode at 120° C, 0.68 V maximum voltage drop). This gives us a maximum theoretical current of 43 A or 514 W for the +12 V output.

The +5 V output uses one STPS30L40CW Schottky rectifier (30 A, 15 A per internal diode at 135° C, 0.74 V maximum voltage drop), giving us a maximum theoretical current of 21 A or 107 W for the +5 V output.

The +3.3 V output uses one STPS40L45CW Schottky rectifier (40 A, 20 A per internal diode at 130° C, 0.7 V maximum voltage drop), giving us a maximum theoretical current of 29 A or 94 W for the +3.3 V 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: +3.3 V, +5 V and +12 V rectifiers

This power supply uses a PS223 monitoring integrated circuit, which supports over voltage (OVP), under voltage (UVP), over temperature (OTP), and over current (OCP) protections. The over current protection circuit available in this integrated circuit has four channels, one for +3.3 V, one for +5 V, and two for +12 V. However, in this power supply only one +12 V OCP channel is used, as it has a single-rail design.

Figure 14: Monitoring circuit

The electrolytic capacitors available in the secondary are from Teapo and labeled at 105° C.