OCZ StealthXStream 400 W Power Supply Review

Primary Analysis

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 100° C, if a heatsink is used, or up to 8 A at 50° 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.

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 25° C or 7.6 A at 100° C in continuous mode (note the difference temperature makes) or 48 A in pulse mode at 25° C, presenting a resistance of 380 mΩ when turned on, a characteristic called RDS(on) – the lower this number the higher efficiency is.

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 85° C.

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

Figure 11: Switching transistors.

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

Figure 12: PFC/PWM combo controller.

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