This power supply uses nine STPS30L60CT Schottky rectifiers on its secondary and each one is capable of handling up to 30 A (15 A per internal diode at 130º C, maximum voltage drop of 0.75 V). Eight of these rectifiers are in charge of producing the +12 V output, with +5 V and +3.3 V being generated from the +12 V output using separated DC-DC converters (i.e. small switching power supplies) located on two small printed circuit boards. As mentioned before, this is the same design used by Antec Signature, Seasonic M12D and Corsair HX (750W and up) power supply series.

The ninth rectifier available is in charge of the +5VSB output. Also on the secondary heatsink there is a 7912 voltage regulator, in charge of the -12 V output.

Four of the rectifiers are in charge of the direct rectification, while the other four are in charge of the “freewheeling” part of the rectification process (i.e. discharging the coil).

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%.

Thus the secondary from UCP 700 W has a maximum theoretical current of 171 A (30 A x 4 / 0.70). This maximum theoretical current limit is for the whole secondary, since +5 V and +3.3 V are also produced from the +12 V output. The practical limit will depend on other factors, but mainly on the coils used and on the design from the small DC-DC converter used to generate the +5 V and +3.3 V outputs. If this 171 A was solely pulled from the +12 V outputs, this would give us 2,052 W.

click to enlarge
Figure 12: Rectifiers.

On Figure 13 you can see the two DC-DC converters in charge of the +5 V and +3.3 V outputs. As you can see, their outputs are filtered using solid aluminum caps. Each converter is based on an APW7073 controller and uses three FDD8896 power MOSFET transistors, which present a maximum RDS(on) of only 6.8 mΩ.

click to enlarge
Figure 13: DC-DC converters.

The outputs are monitored by a WT7527 integrated circuit, which supports under voltage (UVP), over voltage (OVP) and over current (OCP). Any other protection that this unit may have is implemented outside this integrated circuit.

click to enlarge
Figure 14: Monitoring integrated circuit.

Electrolytic capacitors from the secondary are from Ltec, a Taiwanese manufacturer. We think the manufacturer should have added Japanese capacitors here, since the electrolytic capacitors from the primary are Japanese and the capacitors from the +5 V and +3.3 V outputs are solid.