Nexus Value 430 Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of the Nexus Value 430. For a better understanding, please read our “Anatomy of Switching Power Supplies” tutorial.

This power supply uses one GBU806 rectifying bridge, which is attached to the same heatsink as the active PFC and switch transistors. This bridge supports up to 8 A at 100° C. 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

The active PFC circuit uses one IXTH22N50P MOSFET, which supports up to 22 A at 25° C in continuous mode or 50 A at 25° C in pulse mode. Unfortunately, the manufacturer doesn’t mention which is the current limit at 100° C. These transistors present a 270 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: Active PFC diode and transistor

The output of the active PFC circuit is filtered by one 220 µF x 400 V electrolytic capacitor from Teapo, labeled at 85° C.

In the switching section, two IXTP12N50PM MOSFETs are employed using the traditional two-transistor forward configuration. Each of these transistors support up to 6 A at 25° C in continuous mode or up to 30 A at 25° C in pulse mode, with a maximum RDS(on) of 500 mΩ (which is high). Unfortunately, the manufacturer doesn’t publish the current limits at 100° C.

Figure 12: The switching transistors

The primary is managed by a CM6805 active PFC/PWM combo controller.

Figure 13: Active PFC/PWM combo controller

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