Secondary Analysis

This power supply uses four Schottky rectfiers on its secondary.

The +12 V output is produced by two SBR30A50CT Schottky rectifiers connected in parallel, which can deliver up to 30 A each (measured at 25º C), thus the maximum theoretical current the +12 V line can deliver is of 60 A, which equals to 720 W at 25º C. The maximum current this line can really deliver will depend on other components, especially the transformer, the coil, the capacitor and the wire gauge used.

The +5 V output is produced by one STPS30L30CT Schottky rectifier, which support up to 30 A (measured at 140º C). So the maximum theoretical power the +5 V output can deliver is 150 W. Of course the maximum current (and thus power) this line can really deliver will depend on other components, especially the transformer, the coil, the capacitor and the wire gauge used, as mentioned before.

The +3.3 V output is produced by another STPS30L30CT Schottky rectifier, which support up to 30 A (measured at 140º C). So the maximum theoretical power the +3.3 V output can deliver is of 99 W. Of course the maximum current (and thus power) this line can really deliver will depend on other components, especially the transformer, the coil, the capacitor and the wire gauge used, as mentioned before.

Even though this power supply has a separated rectifier for the +3.3 V output, this rectifier is connected to the same transformer output as the +5 V line, so the maximum current +5 V and +3.3 V can pull together is limited by the transformer.

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Figure 11: Three of the four Schottky rectifiers used on the secondary. The other rectifier is on the other side of the heatsink.

This power supply uses a semiconductor thermal sensor, which is very small and installed on the solder side of the printed circuit board, between the transformer and the +12 V rectifiers. This sensor is used to control the fan speed according to the power supply internal temperature and also to shut it down in the case of an overheating situation.

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Figure 12: Thermal sensor.

On this power supply the active PFC capacitor is rated at 85º C, while the electrolytic capacitors from the secondary are rated at 105º C and are manufactured by OST, a Taiwanese company.

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