Cooler Master GX 450 W Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of the Cooler Master GX 450 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBU806 rectifying bridge on its primary, which is attached to an individual heatsink. This component supports up to 8 A at 100° C, so in theory, you would be able to pull up to 920 W from a 115 V power grid. Assuming 80% efficiency, the bridge would allow this unit to deliver up to 736 W without burning itself out. Of course, we are only talking about this component, and the real limit will depend on all the other components in this power supply.

Figure 10: Rectifying bridge

The active PFC circuit uses only one transistor, an IPW50R140CP, which supports up to 23 A at 25° C or up to 15 A at 100° C (note the difference temperature makes) in continuous mode, or up to 56 A in pulse mode at 25° C. This transistor presents a 140 mΩ resistance when turned on, a characteristic called RDS(on). The lower this number the better, meaning that the transistor will waste less power and the power supply will have a higher efficiency. The BFG LS-450 used a more powerful transistor here (32 A at 25° C or 20 A at 100° C).

The electrolytic capacitor that filters the output of the active PFC circuit is Japanese, from Matsushita (Panasonic), and labeled at 105° C.

In the switching section, two STP12NM50 MOSFETs are used in the traditional two-transistor forward configuration. Each one supports up to 12 A at 25° C or up to 7.5 A at 100° C in continuous mode, or up to 48 A at 25° C in pulse mode, with an RDS(on) of 350 mΩ.

Figure 11: One of the switching transistors, active PFC diode, and active PFC transistor

The primary is controlled by a CM6806 active PFC/PWM combo.

Figure 12: Active PFC/PWM combo controller

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