On this page we will take an in-depth look at the primary stage of Cooler Master Silent Pro M 850 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.
This power supply uses three GBU806 rectifying bridges in its primary. Each bridge supports up to 8 A at 100º C if a heatsink is used or only 3.5 A at 100º C is a heatsink is not available. Unfortunately a formal heatsink isn’t used but the three bridges are screwed together. At the nominal 8 A current the power supply would be able to pull up to 2,769 W from a 115 V power grid, but at 3.5 A we have a maximum theoretical AC power of 1,208 W at 115 V. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 966 W without burning them. Of course, we are only talking about these components, and the real limit will depend on all the other components in this power supply.
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Figure 9: Rectifying bridges.
The active PFC circuit uses three FCPF21N60N power MOSFET transistors. Unfortunately we couldn’t find this component being listed on the website from the manufacturer (Fairchild).
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Figure 10: Active PFC transistors and diode.
This power supply uses one big Japanese 680 µF x 420 V capacitor to filter the output from the active PFC circuit, labeled at 105º C. This is good for two reasons, first, Japanese capacitors do not leak; and second, usually manufacturers use 85º C capacitors here, so it is good to see a manufacturer using a capacitor with a higher temperature rating.
In the switching section, two IPI60R125CP power MOSFET transistors are used on the traditional two-transistor forward configuration. Each transistor supports up to 25 A at 25º C or 16 A at 100º C (note the difference temperature makes) or 82 A in pulse mode at 25º C, presenting an RDS(on) of 125 mΩ.
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Figure 11: Switching transistors.
This power supply uses a CM6802 active PFC/PWM combo controller.
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Figure 12: Active PFC/PWM combo controller.
Now let’s take a look at the secondary of this power supply.
