Secondary Analysis

This power supply uses four power Schottky rectifiers on its secondary section: one SBL4060PT and three SBL4040PT, all of them capable of delivering up to 40 A @ 100º C.

The +12 V output uses one SBL4040PT, so it can deliver up to 480 W. The maximum current this line can really deliver will depend on other components, especially the transformer, the coil, the capacitor, the wire gauge and even the width of the printed circuit board traces used.

The +5 V output uses two SBL4040PT in parallel, so it can deliver up to 80 A or 400 W. Funny because usually it is the +12 V output that has two rectifiers in parallel.

Here we found something different from the majority of power supplies with no PFC we’ve seen so far. Usually the +3.3 V output on low-end power supplies is done by a 3.3 V voltage regulator connected to the +5 V output. This power supply from Seventeam, however, uses the same design as high-end power supplies, using an independent Schottky rectifier for producing its +3.3 V output. So even though on the primary this power supply uses the same design as old AT power supplies, on the secondary it uses the same design as modern power supplies.

The +3.3 V output is produced by the SBL4060PT, so it can deliver up to 132 W. Always keep in mind that the maximum current this line can really deliver will depend on other components, especially the transformer, the coil, the capacitor, the wire gauge and even the width of the printed circuit board traces used.

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Figure 11: Power rectifiers used on the secondary.

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Figure 12: Power rectifiers used on the secondary.

Even though the +5 V line and the +3.3 V line have separated rectifiers, they share the same transformer output. So the maximum current both lines can deliver will depend a lot on the transformer.

On Figure 13 you can see a thermal sensor connected to the secondary heatsink, which commands the power supply to shut down under an overheating situation (we removed the secondary heatsink to take this photo) and also controls the fan speed according to the power supply temperature.

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Figure 13: Thermal sensor found on the secondary heatsink.

This power supply uses two Japanese electrolytic capacitors from Toshin Kogyo (TK) on its voltage doubler (rated at 85º C) but all other capacitors are Taiwanese, from CapXon (all rated 105º C).

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