ADATA BN-550 Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of the ADATA BN-550. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one KBU10J rectifying bridge on its primary, which is attached to an individual heatsink. This component supports up to 10 A at 75° C, so in theory, you would be able to pull up to 1,115 W from a 115 V power grid. Assuming 80% efficiency, the bridge would allow this unit to deliver up to 920 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 10: Rectifying bridge

The a
ctive PFC circuit uses two IPP60R190C6 MOSFETs, each supporting up to 20.2 A at 25° C or up to 12.8 A at 100° C (note the difference temperature makes) in continuous mode, or up to 59 A in pulse mode at 25° C. These transistors present a 190 mΩ resistance when turned on, a characteristic called RDS(on). The lower this number the better, meaning that the transistor will waste less power, and the power supply will have a higher efficiency.

Figure 11: Active PFC transistors

The electrolytic capacitor that filters the output of the active PFC circuit is from CapXon and labeled at 85° C.

In the switching section, two FDP18N50 MOSFETs are used in the traditional two-transistor forward configuration, each supporting up to 18 A at 25° C or up to 10.8 A at 100° C (note the difference temperature makes) in continuous mode, or up to 72 A in pulse mode at 25° C, with an RDS(on) of 265 mΩ.

Figure 12: One of the switching transistors

The primary is controlled by an FAN4800 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.