Primary Analysis

Let’s now take an in-depth look on the primary stage from Enermax PRO82+ 525 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBU10J rectifying bridge on its primary, which support up to 10 A at 100º C. This bridge is attached to an individual heatsink and is clearly overspec'ed: at 115 V this unit would be able to pull up to 1,150 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 920 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.

The active PFC circuit uses two TK20J60T power MOSFET transistors, which one capable of handling up to 20 A in continuous mode or 40 A in pulse mode, both at 25º C. These transistors are located on the same heatsink as the switching transistors.

On the switching section this power supply uses another two TK20J60T power MOSFET transistors in the traditional two-transistor forward configuration.

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Figure 10: Active PFC transistor (left) and switching transistor (right).

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Figure 11: Switching transistor, active PFC diode, active PFC transistor and +5VSB switching transistor.

The primary section of this power supply is controlled by a CM6802B integrated circuit, which is a newer version of CM6800, the most popular active PFC/PWM controller combo around. On this new version the manufacturer guarantees at least 80% efficiency. Nice choice.

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Figure 12: Active PFC/PWM controller combo.