SilverStone Strider Plus 750 W Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of SilverStone Strider Plus 750 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBU1006 rectifying bridge in its primary, capable of delivering up to 10 A at 100° C. 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 an
d the real limit will depend on all other components from the power supply. Interesting enough Zalman ZM-770XT, which is based on a similar project, has two of these bridges connected in parallel.

Figure 9: Rectifying bridge.

On the active PFC circuit two STW25NM50N power MOSFET transistors are used, each one capable of delivering up to 22 A at 25° C or 14 A at 100° C in continuous mode (note the difference temperature makes), or up to 88 A in pulse mode at 25° C. These transistors present a resistance of 140 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. Zalman ZM-770XT uses more powerful transistors here (32 A,  20 A and 96 A, respectively).

This power supply uses two electrolytic capacitors to filter the output from the active PFC circuit. The use of more than one capacitor here has absolute nothing to do with the “quality” of the power supply, as laypersons may assume (including people without the proper background in electronics doing power supply reviews around the web). Instead of using one big capacitor, manufacturers may choose to use two or more smaller components that will give the same total capacitance, in order to better accommodate space on the printed circuit board, as two or more capacitors with small capacitance are physically smaller than one capacitor with the same total capacitance. SilverStone Strider Plus 750 W uses two 270 µF x 420 V capacitors in parallel; this is equivalent of one 540 µF x 420 V capacitor. These capacitors are Japanese, from Chemi-Con and labeled at 85° C. These are the same components used on Zalman ZM-770XT.

In the switching section, two STW25NM50N power MOSFET transistors are used, using the traditional two-transistor forward design. Each one is capable of delivering up to 22 A at 25° C or 14 A at 100° C in continuous mode, or up to 88 A at 25° C in pulse mode, with an RDS(on) of 140 mΩ. These are the same transistors used on Zalman ZM-770XT.

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

The primary is controlled by the popular CM6802 PWM/PFC combo integrated circuit. Interesting enough Zalman ZM-770XT is controlled by the previous version from this chip, CM6800.

Figure 11: PWM/PFC combo controller.

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