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 one T8KB80 rectifying bridge, which is not attached to a heatsink. We couldn’t find the datasheet for this component, but it is clear that it is an 8 A part, 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 particular component. The real limit will depend on all the components combined in this power supply.
As mentioned before, this power supply doesn’t have a PFC circuit.
The voltage doubler circuit uses two 470 µF x 220 V electrolytic capacitors from CapXon and labeled at 105° C.
Usually, power supplies without a PFC circuit are based on the obsolete half-bridge design; the Antec VP350 uses the single-transistor forward configuration, which is better. The Antec VP450, on the other hand, uses the two-transistor forward configu
ration, which is excellent.
In the switching section, one STW12NK90Z MOSFET is used in the single-transistor forward configuration, supporting up to 11 A at 25° C or 7 A at 100° C in continuous mode, or up to 44 A at 25° C in pulse mode, with an RDS(on) of 880 mΩ, which is very high (i.e., low efficiency).
The switching transistor is controlled by an NCP1252 PWM controller.
Let’s now take a look at the secondary of this power supply.