Let’s now take an in-depth look on the primary stage from Rosewill RD600N-2SB-SL-BK. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.
This power supply uses one GBU1006 rectifying bridge on its primary, capable of delivering up to 10 A at 100º C, if it has a heatsink attached, which is the case (without the heatsink the current limit drops to 3.2 A). This is an adequate rating for a 600 W power supply. The reason why is that 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.
On this power supply the rectifying bridge is protected by a rubber tape, as you can see on Figure 8.
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Figure 8: Rectifying bridge.
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Figure 9: Rectifying bridge.
The active PFC circuit uses two FQA24N50 power MOSFET transistors, each one capable of delivering up to 15.2 A at 100º C (or 24 A at 25º C, see the difference temperature makes). They are located on the same heatsink as the switching transistors.
The switching section from this power supply uses two SPW20N60C3 power MOSFET transistors in the traditional two-transistor forward configuration. Each switching transistor can handle up to 13.1 A at 100º C (or 20.7 A at 25º C, once again see the difference temperature makes).
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Figure 10: Switching transistor, active PFC transistor and the other switching transistor (the second active PFC transistor is on the other side of the heatsink).
The primary is controlled by a CM6800 integrated circuit, which is a very popular PFC/PWM combo controller.
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Figure 11: PFC/PWM controller.
We couldn’t recognize the manufacturer of the electrolytic capacitor used on the active PFC circuit. It is rated at 85º C.
