Transient Filtering Stage
As we have mentioned in other articles and reviews, the first place we look when opening a power supply for a hint about its quality, is its filtering stage. The recommended components for this stage are two ferrite coils, two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor), and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components, usually removing the MOV and the first coil.
The AC receptacle used in this power supply isn’t a simple connector, but a complete filtering circuit. The Seasonic X-400 Fanless has all the required components, as you can see in Figure 9.
In the next page we will have a more detailed discussion about the components used in the Seasonic X-400 Fanless.