High Power Direct12 BR 850 W Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of the High Power Direct12 BR 850 W. For a better understanding, please read our “
Anatomy of Switching Power Supplies” tutorial.

This power supply uses one GBJ2506 rectifying bridge, which is attached to the same heatsink as the active PFC components. This bridge supports up to 25 A at 100° C, so in theory, you would be able to pull up to 2,875 W from a 115 V power grid. Assuming 80% efficiency, the bridge would allow this unit to deliver up to 2,300 W without burning itself out. Of course, we are only talking about this particular component. The real limit will depend on all the components combined in this power supply.

Figure 10: Rectifying bridge

The active PFC circuit uses two SPW24N60C3 MOSFETs, each supporting up to 24.3 A at 25° C or 15.4 A at 100° C in continuous mode (note the difference temperature makes), or 72.9 A at 25° C in pulse mode. These transistors present a 160 mΩ 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.

Figure 11: The active PFC transistors

The output of the active PFC circuit is filtered by a Japanese capacitor, from Chemi-Con, labeled at 105° C.

In the switching section, another two SPW24N60C3 MOSFETs are used in the traditional two-transistor forward configuration. The specifications for these transistors were discussed above.

Figure 12: The switching transistors

The primary is controlled by the omnipresent CM6800 active PFC/PWM combo controller.

Figure 13: Active PFC/PWM combo controller

Let’s now take a look at the secondary of this power supply.