Zalman ZM600-ST Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of Zalman ZM600-ST. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBU1006 rectifying bridge, which supports up to 10 A at 100° C if a heatsink is used, which is the case. 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 itself out. 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 only one transistor, an SPW35N60C3, capable of delivering up to 34.6 A at 25° C or 21.9 A at 100° C in continuous mode (note the difference temperature makes) or up to 103.8 A at 25° C in pulse mode. This transistor presents a maximum resistance of 100 mΩ when turned on, a characteristic called RDS(on). This number indicates the amount of power that is wasted, so the lower this number the better, as less power will be wasted thus increasing efficiency. Usually power supplies use two transistors on this stage and not only one.

The electrolytic capacitor used to filter the output from the active PFC circuit is Japanese from Matsushita (Panasonic) and labeled at 105° C. The product webpage says “Japanese capacitors” (in the plural), but this information is wrong, as there is only one cap present on the primary.

The reviewed power supp
ly uses two STP25NM50N power MOSFET transistors on its switching section, installed on the traditional two-transistor forward configuration. Each transistor can handle up to 22 A at 25° C or up to 14 A at 100° C in continuous mode, or up to 88 A at 25° C in pulse mode, with a maximum RDS(on) of 140 mΩ.

Figure 10: Switching transistors, active PFC diode and active PFC transistor.

The primary is controlled by a CM6806 PFC/PWM combo controller.

Figure 11: PFC/PWM combo controller.

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