CWT 750VH 750 W Power Supply Review

Secondary Analysis

This power supply uses four Schottky rectifiers on its secondary.

The +12 V output is produced by two STPS6045CW Schottky rectifiers connected in parallel. Each rectifier supports up to 60 A at 150° C (30 A per internal diode). The maximum theoretical current the +12 V 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 (which in this case is made by two 30 A diodes in parallel). Just as an exercise, we can assume a typical duty cycle of 30%. This would give us a maximum theoretical current of 86 A or 1,029 W for the +12 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used.

The +5 V output is produced by one STPS40L45CW Schottky rectifier, which supports up to 40 A at 130° C (20 A per internal diode). The maximum theoretical current the +5 V 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 (which in this case is made by one 20 A diode). Just as an exercise, we can assume a typical duty cycle of 30%. This would give us a maximum theoretical current of 29 A or 143 W for the +5 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used. This is the same rectifier used by Corsair TX750W and Thermaltake Toughpower 750 W.

The +3.3 V output is produced by another STPS40L45CW Schottky rectifier, which supports up to 40 A at 130° C (20 A per internal diode). The maximum theoretical current the +12 V 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 (which in this case is made one 20 A diode). Just as an exercise, we can assume a typical duty cycle of 30%. This would give us a maximum theoretical current of 29 A or 94 W for the +3.3 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used.

Even though this power supply uses a separated rectifier for the +3.3 V output, it is generated from the same transformer output that feeds the +5 V rail, so the maximum current the +5 V and +3.3 V outputs can deliver together is limited by the transformer.

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

Figure 13: Thermal sensor and +12 V rectifier.

This power supply uses a PS229 monitoring integrated circuit, which is in charge of the power supply protections. Unfortunately there is no information about this model on the manufacturer’s website.

The thermal sensor is attached to the secondary heatsink and you can see it in Figure 13. This sensor is used to control the fan speed according to the power supply internal temperature. During our tests we could see the power supply fan gradually increasing its speed as the power supply temperature increased.

This power supply uses capacitors from Samxon on the secondary, a company from Hong Kong with manufacturing facilities in China. They are all rated at 105° C, as usual.