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Secondary Analysis

This power supply has five Schottky rectifiers on its secondary.

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 two S30D150C Schottky rectifiers, each one supporting up to 30 A (15 A per internal diode at 100° C, 0.95 V maximum voltage drop), giving us a maximum theoretical current of 43 A or 514 W for the +12 V output.

The +5 V output is produced by one SBL6040PT Schottky rectifier, which supports up to 60 A (30 A per internal diode), giving us a maximum theoretical current of 43 A or 214 W for the +5 V output.

The +3.3 V output is produced by two SBL3040PT Schottky rectifiers connected in parallel, each one supporting up to 30 A (15 A per internal diode), giving us a maximum theoretical current of 43 A or 141 W for the +3.3 V output.

One curious thing we noticed was the presence of a -5 V output (white wire), that has been removed from the ATX12V specification in January 2002. Interesting enough this unit is labeled as being an ATX12V 2.3 model.

All these numbers are theoretical. The real amount of current/power each output can deliver is limited by other components, especially by the coils used on each output.

Cooler Master eXtreme Power Plus 550 W RS-550-PCAR-E3 power supplyFigure 12: +3.3 V, +5 V and +12 V rectifiers.

The outputs are monitored by a WT7510 integrated circuit, which supports only OVP (over voltage protection) and UVP (under voltage protection) protections.

Cooler Master eXtreme Power Plus 550 W RS-550-PCAR-E3 power supplyFigure 13: Monitoring integrated circuit.

The electrolytic capacitors from the secondary are also from Su’scon.

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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.