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Secondary Analysis

As one would expect in a high-efficiency power supply, the FSP Aurum Pro 850 W uses a synchronous design, where the Schottky rectifiers are replaced with MOSFETs. Also, the reviewed product uses a DC-DC design in its secondary. This means that the power supply is basically a +12 V unit, with the +5 V and +3.3 V outputs produced by two smaller power supplies connected to the main +12 V rail. Both designs are used to increase efficiency.

The +12 V output uses four IPD036N04L G MOSFETs, each one supporting up to 90 A at 25° C or 87 A at 100° C in continuous mode, or up to 400 A at 25° C in pulse mode, with a maximum RDS(on) of only 3.6 mΩ. These transistors are located on the solder side of the printed circuit board, and the power supply housing is used as a heatsink for these transistors.

FSP Aurum Pro 850 W power supplyFigure 17: The +12 V transistors

As explained, the +5 V and +3.3 V outputs are produced by two DC-DC converters, which are located on a single daughterboard soldered to the main printed circuit board. In Figures 18 and 19, you can see the physical aspect of this card. The converters are controlled by an APW7158 integrated circuit, using four APM3116N and four APM3109N MOSFETs. Unfortunately, datasheets for these components are not available on their manufacturer’s website.

FSP Aurum Pro 850 W power supplyFigure 18: The DC-DC converters

FSP Aurum Pro 850 W power supplyFigure 19: The DC-DC converters

This power supply uses a PS223 monitoring integrated circuit, which supports over voltage (OVP), under voltage (UVP), and over current (OCP) protections, with four channels (+12V1, +12V2, +5 V, and +3.3 V). The manufacturer decided to use only one of the +12 V over current protection channels, making this unit a single-rail design. 

FSP Aurum Pro 850 W power supplyFigure 20: Monitoring circuit

The electrolytic capacitors that filter the +12 V output are solid, from CapXon. (Some standard Japanese electrolytic capacitors, from Rubycon and Chemi-Con, are also used.)

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Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.