PC Power & Cooling Silencer 760 W Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of the PC Power & Cooling Silencer 760 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

Like the Seasonic S12D 750 W and the Seasonic M12D 750 W (which are internally identical to the Silencer 760 W) this unit has two rectifying bridges feeding two separate active PFC circuits. Each bridge is a GBU806, supporting up to 8 A at 100° C so, in theory, you would be
able to pull up to 1,840 W from a 115 V power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 1,472 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. The two bridges are attached to a heatsink.

Figure 10: Rectifying bridges

As explained, there are two separate active PFC circuits, each one using two FWP12N50C MOSFETs, so we have a total of four transistors. Each one of them is capable of delivering up to 13 A at 25° C or up to 8 A at 100° C (note the difference temperature makes) in continuous mode, or up to 52 A in pulse mode at 25° C. These transistors present a 480 mΩ resistance when turned on, a characteristic called RDS(on). The lower this number the better, meaning that the transistors will waste less power and the power supply will achieve a higher efficiency.

Figure 11: Active PFC transistors

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 components on the printed circuit board, as capacitors with lower capacitance are physically smaller than capacitors with higher capacitance. Also, the use of two capacitors in parallel divides the current that flows through each one of them, reducing the amount of heat generated. The Silencer 760 W uses one 390 µF x 420 V and one 330 µF x 420 V capacitors connected in parallel; this is equivalent of one 720 µF x 420 V capacitor. These capacitors are Japanese, from Chemi-Con, and are labeled at 105° C.

In the switching section, two SPP24N60C3 MOSFETs are used, installed in the traditional two-transistor forward configuration. Each transistor supports up to 24.3 A at 25° C or 15.4 A at 100° C (note the difference temperature makes) or 72.9 A in pulse mode at 25° C, presenting an RDS(on) of 160 mΩ.

Figure 12: Switching transistors and active PFC transistors

The primary is managed by a CM6802 active PFC/PWM combo controller.

Figure 13: Active PFC/PWM controller

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