Component Analysis (Cont’d)

On Figures 23 and 24 you can see the components that are attached to the primary heatsink. As mentioned, even though there are four power MOSFET transistors (labeled Q4 thru Q7), Q4 and Q5 are connected in parallel, as it is Q6 and Q7.

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Figure 23: Rectifying bridges, active PFC transistors and active PFC diode.

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Figure 24: Switching transistors and rectifying bridges.

This power supply uses eight Schottky power rectifiers on its secondary, four 63CPQ100 (60 A @ 153º C) and four 40CTQ045 (40 A @ 116º C).

For the +5 V output two 40CTQ045 are used. This means that in theory the +5 V output is capable of delivering up to 80 A or 400 W. Keep in mind that the maximum power the power supply can deliver depends on other components used – like the transformer, coils, capacitors, the PCB layout, the wire gauge and even the width of the printed circuit board traces.

The +3.3 V output also uses two 40CTQ045 Schottky rectifiers, connected to a dedicated transformer output, which is terrific. On the vast majority of power supplies even when the +3.3 V output has its own rectifiers, they are connected to the same transformer output as the +5 V line, so the transformer limits the maximum current (and thus power) the +5 V and +3.3 V lines can deliver together (a concept called “combined power”). So in theory the +3.3 V output is capable of delivering 80 A or 264 W. Like we said before, the other components used on the power supply will limit the maximum current and power this output can actually deliver.

And the +12 V output uses all the four 63CPQ100 Schottky rectifiers. Two of them are connected to one transformer and the other two are connected to the other transformer, however the outputs of all four rectifiers are connected together, creating the big bottleneck found on this unit. In theory the +12 V rectifiers from this power supply could deliver up to 240 A (60 A x 4) or 2,880 W, but the other components, especially the coil and the electrolytic capacitors, limit this amount.

On the pictures below you can see the rectifiers used on this power supply secondary.

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Figure 25: Rectifiers used on the secondary.

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Figure 26: Rectifiers used on the secondary.

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