On this page we will take an in-depth look at the primary stage of EliteXStream 1000 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBJ2006 rectifying bridge in its primary, capable of delivering up to 20 A at 110º C. This component is clearly overspec'ed: at 115 V this unit would be able to pull up to 2,300 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 1,840 W without burning this component. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.

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Figure 8: Rectifying bridge.

The active PFC circuit uses three 20N60C3 power MOSFET transistors, the same used by several other power supplies we looked. Each one is capable of handling up to 300 A @ 25º C in pulse mode (which is the case) or up to 45 A @ 25º C or 20 A @ 110º C (note the difference temperature makes). Usually the active PFC circuit has only two transistors. Other power supplies that use three transistors on the active PFC circuit we’ve seen so far include Zalman ZM-600HP, OCZ StealthXstream 600 W and OCZ GameXstream 700 W.

Another unusual thing about the active PFC circuit from this power supply is the use of three Japanese electrolytic capacitors from Hitachi rated at 105º C connected in parallel. When capacitors are connected in parallel the value of their capacitances are added. So three 330 µF capacitors connected in parallel is equivalent as one single 990 µF capacitor. This is a very smart trick to achieve a higher capacitance without using a physically bigger component. This is the best possible configuration: Japanese capacitors, high temperature range and very high capacitance.

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Figure 9: The active PFC capacitors.

On the switching section this power supply uses two other 20N60C3 transistors, on the traditional two-transistor forward configuration. The specs for these transistors are published above. They drive the two available transformers, which have their primaries connected in parallel. So even though this power supply has two transformers they share the same driving circuit.

As you can see in Figure 10, all main semiconductors from the primary side are installed on the same heatsink.

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Figure 10: Active PFC diode, three active PFC transistors and two switching transistors.

This power supply uses a discrete active PFC/PWM controller instead of using an integrated circuit that has this circuit already ready to use. On this power supply this circuit was built using one LM339 comparator, one UC3845B current mode controller and one ICE2PCS02 PFC controller.

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Figure 11: Active PFC/PWM controller circuit.