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 transient filtering stage from this power supply is flawless, providing two Y capacitors and one ferrite coil more than required, plus one X capacitor after the rectifying bridge. The MOV is located after the bridge and not before as usual.

Enermax ECO 80+ 620 W power supplyFigure 8: Transient filtering stage (part 1).

Enermax ECO 80+ 620 W power supplyFigure 9: Transient filtering stage (part 2).

In the next page we will have a more detailed discussion about the components used in the Enermax ECO80+ 620 W.


Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.