This power supply uses a synchronous design in its secondary, meaning that the Schottky rectifiers were replaced by MOSFET transistors in order to increase efficiency. On top of that, this unit uses a DC-DC design, meaning that this unit is basically a +12 V power supply, with the +5 V and +3.3 V outputs being generated by two small power supplies attached to the +12 V output.
The +12 V output is generated by six IPP040N06N3 MOSFETs, each one capable of handling up to 90 A at 100⁰ C in continuous mode, or up to 360 A at 25⁰ C in pulse mode, with an RDS(on) of only 3.7 mΩ. In this power supply, the +12 V output is also used to generate the +5 V and the +3.3 V outputs, as you know. As an exercise, if we assume that all load was exclusively pulled from the +12 V output, we would have a maximum theoretical current limit of 386 A or 4,629 W.
Usually, power supplies that use DC-DC converters in the secondary to generate the +5 V and +3.3 V outputs have two separate printed circuit boards, one for each output. The Sentey Golden Steel Power 850 W, however, has a single printed board hosting both circuits.
Each converter is based on one NCP1587A PWM controller and four ME70N03S MOSFETs, each one with a current limit of 62 A at 25° C or 50 A at 70° C in continuous mode, or up to 100 A at 25° C in pulse mode, with a maximum RDS(on) of 11 mΩ.
We didn’t see an integrated circuit for monitoring the power supply outputs, and since the Power Good wire and sensors were connected to the small printed circuit board to where the resonant controller was attached, our best
guess is that the enigmatic SF29601 controller, with the aid of four operational amplifiers provided by an LM324 integrated circuit, do the trick.
The electrolytic capacitors available in the secondary are also from Chemi-Con and labeled at 105° C.