Antec VP350 Power Supply Review

Primary 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 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.

Figure 10: Rectifying bridge

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).

Figure 11: The switching transistor

The switching transistor is controlled by an NCP1252 PWM controller.

Figure 12: PWM controller

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