Antec Signature 650 uses five S60SC6M Schottky Rectifiers on its secondary, each one able to handle up to 60 A at 110º C (30 A per internal diode). Because of the color used on the lacquer layer from the printed circuit board (the foreground and the background had the same color: brown) it was almost impossible for us to follow the traces for a precise analysis of the circuit. From what we could understand, they are all in charge of the +12 V rectification, with the +3.3 V and +5 V outputs being produced by lowering +12 V to +5 V or +3.3 V using two individual voltage regulator circuits (each one also based on switching technology) based on ISL6540ACRZ integrated circuits. This is what Antec refers to “DC to DC voltage regulator modules which ensure greater system stability” on their website.

We can do a quick exercise to see the maximum theoretical power this unit can deliver. 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 five 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 214 A or 2,571 W for the main +12 V bus, which is also used to produce the +5 V and +3.3 V outputs, as explained. As you can see, the rectifiers are clearly overspec'ed, which is always something nice to see.

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Figure 14: Rectifiers.

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Figure 15: Voltage regulators for the +3.3 V and +5 V outputs.

The -12 V output is produced by one LM7912 voltage regulator integrated circuit, which has a current limit of 1.5 A.

Instead of using a monitoring integrated circuit to control the secondary, the manufacturer implemented its own discrete solution, based on two LM339 voltage comparators and one MC1455 timer.

All the electrolytic capacitors from the secondary are Japanese from Chemi-Con and labeled at 105º C.