As mentioned, the problem was that the manufacturer did the favor of scratching off the markings from all semiconductors used in this power supply, preventing us from making a more in-depth analysis about the used components. We wonder why a manufacturer would do that. To prevent other companies from copying the project? As if anyone would copy a project from a manufacturer that is not even on the radar screen.

On the primary we could identify only the rectifying bridge and the PFC/PWM combo controller.

This power supply uses one KBU8K rectifying bridge in its primary, which supports up to 8 A at 100º C. This component is correctly dimensioned: 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 8: Rectifying bridge.

This unit has four power transistors on the primary, two for the active PFC circuit and two for the switching circuit, which uses the traditional two-transistor forward configuration. As mentioned we couldn’t identify them as they had their markings scratched.

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Figure 9: Primary transistors with their markings scratched off.

The electrolytic capacitor used on the active PFC circuit is from Teapo, a Taiwanese company, and labeled at 85º C.

Even though the PWM/PFC controller integrated circuit had also its markings scratched, we could read them: this power supply uses the omnipresent CM6800 controller.

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Figure 10: PWM/PFC controller.

Now let’s take a look at the secondary from Rosewill Performance 650 W.