On this page, we will take an in-depth look at the primary stage of the Cougar GX-S 500 W. For a better understanding, please read our “Anatomy of Switching Power Supplies” tutorial.
This power supply uses one BU1006A rectifying bridge, which is attached to the same heatsink as the active PFC and switching transistors. This bridge supports up to 10 A at 90° C. In theory, you would be able to pull up to 1,150 W from a 115 V power grid. Assuming 80% efficiency, the bridge would allow this unit to deliver up to 920 W without burning itself out (or 1,035 W at 90% efficiency). Of course, we are only talking about this particular component. The real limit will depend on all the components combined in this power supply.
The active PFC circuit uses two P22N60E MOSFETs, each one supporting up to 22 A at 25° C or 13.8 A at 100° C in continuous mode (note the difference temperature makes), or 66 A at 25° C in pulse mode. These transistors pre
sent a 165 mΩ maximum resistance when turned on, a characteristic called RDS(on). The lower the number the better, meaning that the transistor will waste less power, and the power supply will have a higher efficiency.
The active PFC circuit is controlled by a CM6502 integrated circuit.
The output of the active PFC circuit is filtered by a 390 μF x 400 V Japanese electrolytic capacitor, from Hitachi, labeled at 85° C.
In the switching section, two STP28NM50N MOSFETs are employed using a resonant configuration. Each transistor supports up to 21 A at 25° C or 13 A at 100° C in continuous mode or up to 84 A at 25° C in pulse mode, with a maximum RDS(on) of 158 mΩ.
The switching transistors are controlled by a CM6901 resonant controller, which was placed in the secondary of the power supply.
Let’s now take a look at the secondary of this power supply.