OCZ ZT Series 650 W Power Supply Review

Secondary Analysis

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

This power supply uses two T10KB60 rectifying bridges, which are attached to an individual heatsink. Each bridge supports up to 10 A at 100° C, so in theory, you would be able to pull up to 2,300 W from a 115 V power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 1,840 W without burning themselves out. Of course, we are only talking about these particular components. The real limit will depend on all the components combined in this power supply.

Figure 10
: Rectifying bridges

The active PFC circuit uses two FDA24N50 MOSFETs, each one supporting up to 24 A at 25° C or 14 A at 100° C in continuous mode (note the difference temperature makes), or 96 A at 25° C in pulse mode. These transistors present a 190 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 diode and transistors

The output of the active PFC circuit is filtered by a 560 µF x 420 V electrolytic capacitor, from Teapo, labeled at 85° C.

In the switching section, two FDP20N50 MOSFETs are employed using the traditional two-transistor forward configuration. Each transistor supports up to 20 A at 25° C or 12.9 A at 100° C in continuous mode, or 80 A at 25° C in pulse mode, with a 230 mΩ RDS(on).

Figure 12: The switching transistors

The switching transistors are controlled by the famous CM6800 PWM/active PFC combo controller.

Figure 13: Active PFC/PWM controller

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