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, yellow component on the pictures below) and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components, usually removing the MOV and the first coil.

At least here this power supply uses a good design, with two Y capacitors and one X capacitor more than needed. The MOV’s are placed between the two electrolytic capacitors from the voltage doubler, as it is usual to be done on power supplies without active PFC.

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Figure 7: Transient filtering stage (part 1).

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Figure 8: Transient filtering stage (part 2).

In the next page we will have a more detailed discussion of the components used in the eXtreme Power Plus 500 W.