Seventeam ST-650PWL Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of the Seventeam ST-650PWL. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses two GBU1008 rectifying bridges connected in parallel, attached to the same heatsink as the active PFC and switching transistors. Each bridge supports up to 10 A at 100° C so, in theory, you would be able to pull up to 2,300 W from a 115 V power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 1,840 W without burning themselves out. Of course, we are only talking about these components, and the real limit will depend on all the other components in this power supply.

Figure 10: Rectifying bridges

The active PFC circuit uses two SPW35N60C3 MOSFETs, which are capable of delivering up to 34.6 A at 25° C or up to 21.9 A at 100° C (note the difference temperature makes) in continuous mode, or up to 103.8 A in pulse mode at 25° C, each. These transistors present a 100 mΩ resistance when turned on, a characteristic called RDS(on). The lower this number the better, meaning that the transistors will waste less power a
nd the power supply will achieve higher efficiency.

The output of the active PFC circuit is filtered by a capacitor from Su’scon, labeled at 85° C.

In the switching section, two SPP24N60C3 MOSFET transistors are used, installed in the two-transistor forward configuration. Each one supports up to 24.3 A at 25° C or up to 15.4 A at 100° C in continuous mode, or up to 72.9 A at 25° C in pulse mode, with a 160 mΩ RDS(on).

Figure 11: Switching and active PFC transistors

The primary is controlled by the famous CM6800 active PFC/PWM combo controller.

Figure 12: Active PFC/PWM combo controller

Now let’s take a look at the secondary of this power supply.