On this page we will take an in-depth look at the primary stage of OCZ StealthXStream 400 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one KBU10J rectifying bridge in its primary, which can deliver up to 10 A at 100º C, if a heatsink is used, or up to 8 A at 50º C if a heatsink isn’t used, as unfortunately is the case. Nevertheless at 115 V this unit would be able to pull up to 920 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 736 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 9: Rectifying bridge.

On the active PFC circuit two STP14NK50ZFP power MOSFET transistors are used, each one capable of delivering up to 14 A at 25º C or 7.6 A at 100º C in continuous mode (note the difference temperature makes) or 48 A in pulse mode at 25º C, presenting a resistance of 380 mΩ when turned on, a characteristic called RDS(on) – the lower this number the higher efficiency is.

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Figure 10: Active PFC transistors and diode.

The electrolytic capacitor in charge of filtering the output from the active PFC circuit is Japanese from Rubycon and labeled at 85º C.

In the switching section, another two STP14NK50ZFP power MOSFET transistors are used on the traditional two-transistor forward configuration.

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Figure 11: Switching transistors.

The primary is controlled by a CM6800 PFC/PWM combo controller.

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Figure 12: PFC/PWM combo controller.

Now let’s take a look at the secondary of this power supply.