Analog filters are some of the most fundamental and flexible structures in electrical engineering. They are used in impedance matching, harmonic oscillation, signal processing and control. However, the most common application is signal rejection. As explained in our previous article Introduction to Filter Circuits, filters are classified as active and passive filters. Active filters are powerful tools capable of recovering very small signals and rejecting the rest of undesired noise. Passive filters, on the other hand, may not be as powerful as their active counterparts, but they are definitely more efficient, as active filters require extra power to feed the circuit amplifiers. Therefore, passive filters are widely applied in power transmission and converting applications. In this article, we will discuss the Pi Filter, which is a topology of passive filter applied in ripple rejection for AC-DC voltage converters.
