The secondary from ST-550P-AM is different from ST-550P-AG’s. ST-550P-AG uses six Schottky rectifiers, while ST-550P-AM uses only four. This is not necessarily a drawback: even though ST-550P-AG uses two rectifiers for the +5 V output and two rectifiers for the +3.3 V output instead of one each like ST-550P-AM, they use a smaller package than the one used on ST-550P-AM (TO-220 vs. TO-247), meaning they can dissipate less power.

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%. Of course the maximum current (and thus power) this line can really deliver will depend on other components, especially the coil.

The +12 V output is produced by two SBL3060PT Schottky rectifiers, each one supporting up to 30 A (15 A per internal diode at 95º C), so we have a maximum theoretical current of 43 A (15 A x 2 / 0.70), which corresponds to 514 W.

The +5 V output is produced by one SBL4040PT Schottky rectifier, capable of handling up to 40 A (20 A per internal diode at 100º C). This translates into a maximum theoretical current of 29 A or 143 W.

The +3.3 V output is produced by another SBL4040PT Schottky rectifier, so the maximum theoretical power for this output is of 94 W.

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Figure 13: +12 V rectifier and +5 V rectifier.

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Figure 14: +3.3 V rectifier and +12 V rectifier.

The outputs are monitored by a PS223 integrated circuit, which supports the following protections: over current (OCP), under voltage (UVP), over voltage (OVP) and over temperature (OTP, not implemented on this power supply). Any other protection that this unit may have is implemented outside this integrated circuit.

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Figure 15: Monitoring integrated circuit.

The electrolytic capacitors from the secondary are from Samxon, with some Japanese caps from Rubycon also being used, which is really nice to see.