Each secondary is completely independent, with one of them generating the +3.3 V, +12V1 and +12V4 rails and the other generating the +5 V, +12V2 and +12V3 rails.

This power supply is basically a +12 V power supply, with the +12 V output the +5 V and +3.3 V outputs being produced using DC-DC converters (i.e. a small switching power supplies) connected to the +12 V output. Each secondary uses two MBRH300EPT Schottky rectifiers, one STPS30H100CW Schottky rectifier and one STP140NF75 Power MOSFET transistor to produce the +12 V output.

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Figure 16: Semiconductors used on each secondary.

One thing that caught our attention was the fact that all capacitors used on this power supply are Japanese from Chemi-Con, using aluminum solid capacitors on the filtering of the +5 V and +3.3 V voltages. This is the first time we saw solid capacitors being used on a power supply.

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Figure 17: Japanese and solid capacitors used on the secondary. The small printed circuit board is one of the DC-DC converters.

Each secondary is controlled by its own monitoring integrated circuit (PS229), which is installed on a small printed circuit board. Unfortunately the specs for this circuit aren’t available on the manufacturer’s website.

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Figure 18: PS229 monitoring integrated circuit.