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Secondary Analysis

This power supply has five Schottky rectifiers attached to its secondary heatsink.

The maximum theoretical current each 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. Just as an exercise, we can assume a typical duty cycle of 30%.

The +12 V output is produced by three SBR30A50CT Schottky rectifiers, each one capable of delivering up to 30 A (15 A per internal diode at 125° C with a maximum voltage drop of 0.55 V). From the six diodes available (two per device), two are used for the direct rectification path and four are used for the “freewheeling” path. This gives us a maximum theoretical current of 43 A or 514 W for the +12 V output.

The +5 V output is produced by one STPS30L30CT Schottky rectifier, which can handle up to 30 A (15 A per internal diode at 140° C, maximum voltage drop of 0.46 V). This gives a maximum theoretical current of 21 A or 107 W for the +5 V output.

The +3.3 V output is produced by one SBR40U45CT Schottky rectifier, which can handle up to 40 A (20 A per internal diode at 110° C, maximum voltage drop of 0.52 V). This gives us a maximum theoretical current of 29 A or 94 W for the +3.3 V output.

Seasonic S12II Bronze 520 W power supplyFigure 12: +12 V, +3.3 V and +5VSB V rectifiers.

The outputs are monitored by an HY-510N integrated circuit, which supports only over voltage (OVP) and under voltage (UVP) protections.

Seasonic S12II Bronze 520 W power supplyFigure 13: Monitoring integrated circuit.

The secondary capacitors are also Japanese, from Chemi-Con.

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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.