On this page we will take an in-depth look at the primary stage of SilverStone Nightjar 400 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one TS15P06G rectifying bridge in its primary, which can deliver up to 15 A at 100º C. At 115 V this unit would be able to pull up to 1,725 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 1,380 W without burning this component. Talk about overspecification! Of course we are only talking about this component and the real limit will depend on all other components from the power supply.

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Figure 11: Rectifying bridge.

On the active PFC circuit two SPW20N60C3 power MOSFET transistors are used, each one capable of delivering up to 20.7 A at 25º C or 13.1 A at 100º C in continuous mode (note the difference temperature makes) or 62.1 A in pulse mode at 25º C, presenting a resistance of 190 mΩ when turned on, a characteristic called RDS(on) – the lower this number the higher efficiency is.

The electrolytic capacitor in charge of filtering the output from the active PFC circuit is Japanese from Chemi-Con and labeled at 105º C. This is terrific, especially because being a fanless power supply we would expect this unit to achieve a higher internal temperature.

The active PFC coil is attached to the primary heatsink, which is quite interesting.

In the switching section, two STP20NM50FP power MOSFET transistors, each one capable of delivering up to 20 A at 25º C or 12.6 A at 100º C in continuous mode (note the difference temperature makes) or 80 A in pulse mode at 25º C, presenting a maximum RDS(on) of 250 mΩ.

The switching transistors are connected using a design called “LLC resonant,” also known as a series parallel resonant converter, being controlled by an L6598 integrated circuit. The coil required by this design is also attached to the primary heatsink. So far we’ve seen only a couple of other power supplies using this kind of design, like Seasonic X-Series 650 W and Thermaltake Toughpower 800 W.

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Figure 12: Active PFC transistor and the two switching transistors. Note the resonant coil.

The active PFC circuit is controlled by a separated integrated circuit, an L4981A.

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Figure 13: Active PFC controller (left) and resonant controller (right).

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