Thermaltake Toughpower Grand 750 W Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of the Thermaltake Toughpower Grand 750 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses two GBU806 rectifying bridges, which are attached to the same heatsink where the active PFC transistors are located. Each bridge supports up to 8 A at 100° C so, in theory, you would be able to pull up to 1,840 W from a 115 V power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 1,472 W without burning themselves out. Of course, we are only talking about these components, and the real limit will depend on all the other components in this power supply.

Figure 10: Rectifying bridges

The active PFC circuit uses two SPW35N60C3 MOSFETs, each one capable of delivering up to 34.6 A at 25° C or up to 21.9 A at 100° C (note the difference temperature makes) in continuous mode, or up to 103.8 A in pulse mode at 25° C. These transistors present a 100 mΩ resistance when turned on, a characteristic called RDS(on). The lower this number the better, meaning that the transistors will waste less power and the power supply will achieve a higher efficiency.

Figure 11: 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 SPW35N60C3 MOSFETs are used, installed in the two-transistor forward configuration, and their technical specs were already published above.

Figure 12: Switching transistors

The primary is controlled by the famous CM6800 active PFC/PWM combo controller. This was definitely an unusual choice, since most manufacturers decided to use a resonant project in their 80 Plus Gold power supplies instead of the traditional two-transistor forward configuration.

Figure 13: Active PFC/PWM combo controller

Now let’s take a look at the secondary of this power supply.