Thortech Thunderbolt Plus 800 W Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of the Thortech Thunderbolt Plus 800 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GSIB2580 rectifying bridge, which is attached to an individual heatsink. This bridge supports up to 25 A at 98° 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 component, and the real limit will depend on all the other components in this power supply.

Figure 11: Rectifying bridge

The design of the active PFC circuit is somewhat different. The Thortech Thunderbolt Plus 800 W has two active PFC circuits, each one connected to one of the rectified outputs of the rectifying bridge. That is why there are two transformers in the primary of this power supply, they are the active PFC coils. Each active PFC circuit uses one IXFH44N50P MOSFET, which is capable of delivering up to 44 A at 25° C or up to 28 A at 100° C (note the difference temperature makes) in continuous mode, or up to 110 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 transistors will waste less power and the power supply will achieve a higher efficiency.

Figure 12: Active PFC diodes and transistors

This power supply has two electrolytic capacitors, each one connected to the output of each active PFC circuit. Both are Japanese, from Chemi-Con, and labeled at 105° C.

The active PFC circuit is controlled by a UCC28061 chip (see Figure 14).

In the switching section, another two IXFH44N50P MOSFET transistors are used.

Figure 13: Switching transistors

The switching transistors are connected using a design called resonant half-bridge topology, controlled by an L6599 integrated circuit, which allows the PFC circuit to be turned off when the unit is operating with a light load.

Figure 14: Primary control board

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