Primary Stage (Cont’d )

This power supply uses a D15XB60 rectifying bridge, which can deliver up to 15 A, rated at 100º C. It also uses two power diodes connected in parallel on its active PFC circuit, where the normal is using just one. The rectifying bridge and the two PFC diodes are located on the same heatsink, which you can see on Figure 11.

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Figure 11: Active PFC diodes and rectifying bridge.

The active PFC circuit uses two 20N60C3 power MOSFET transistors and the switching section uses two more of them. Several other power supplies from several different power ranges, like Cooler Master iGreen Power 430 W, Antec Neo 550 HE, OCZ StealthXStream 600 W, Zalman ZM600-HP, Corsair HX620W, OCZ GameXstream 700 W and Thermaltake Toughpower 750 W, just to name a few, use these same transistors on their active PFC circuit. On the switching section, however, only OCZ ProXStream 1000 W uses them; these other power supplies use other transistors, some with higher specs.

These 20N60C3 can drive up to 20 A at 25º C or up to 12.5 A at 100º C in continuous mode (see how the maximum current drops a lot depending on the temperature; since power is directly proportional to current, drop in maximum available current also means drop in maximum available power) or 60 A in pulse mode, which is the one used.

The two switching transistors are using the traditional two-transistor forward configuration. A detailed description of this configuration including schematics can be found on our Anatomy of Power Supplies tutorial.

The four 20N60C3 are found on the same heatsink, as shown on Figure 12.

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Figure 12: Two of these transistors are used by the active PFC circuit and the other two are used on the switching section.

Let’s now take a closer look on the secondary stage from this power supply.

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