Seventeam ST-550P-AM ASM Power Supply Review

Primary Analysis

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

This power supply uses one GBU1006 rectifying bridge in i
ts primary, capable of delivering up to 10 A at 100° C. This component is clearly overspec’ed: at 115 V this unit would be able to pull up to 1,150 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 920 W without burning this component. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.

Figure 9: Rectifying bridge.

The active PFC circuit uses two SPW16N50C3 power MOSFET transistors, each one capable of handling up to 48 A @ 25° C in pulse mode (which is the case) or up to 16 A @ 25° C or 10 A @ 100° C (note the difference temperature makes).

Figure 10: Active PFC transistors and diode.

The electrolytic capacitor used on the active PFC circuit is Japanese from Matsushita (Panasonic), which is great. It is labeled at 85° C.

On the switching section this power supply uses another two SPW16N50C3 power MOSFET transistors, on the traditional two-transistor forward configuration. The specs for these transistors are published above.

Figure 11: Switching transistors.

The primary is controlled by a FAN4800 active PFC/PWM controller combo installed on a small printed circuit board, a direct competitor to the very popular CM6800 integrated circuit.

Figure 12: Active PFC/PWM controller.

The primary from ST-550P-AM is identical to ST-550P-AG’s. Let’s see now the secondary.