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Pi filter designer series#
This topology adds a choke inductor in series with a capacitor in parallel with the load, acting as a resonant second-order filter. In applications with large load variation, the L-section is more adequate (Figure 3). As the load demand increases, the speed of capacitor discharge increases and, consequently, the AC ripple increases.
![pi filter designer pi filter designer](https://i.stack.imgur.com/mPFtA.png)
However, as you may have notice, there is one fundamental limitation to this approach: its effectiveness is dependent on the load. This technique is extremely simple and effective, which explain its widely used in most applications. In terms of impedance, it can be said that the capacitor provides a lower impedance path for the AC current compared to the load, and a lower AC current passing through the load means smaller AC voltage component. The capacitor absorbs the AC current from the source, but due to its energy storage capability the voltage is kept at the peak value, decreasing slowly as the energy is dissipated by the load, until the next peak is reached (Figure 2). The shunt capacitor consists of a simple capacitor at the output of the rectifier, in parallel with the load. Both are applied at the output of voltage rectifiers (typically full-bridge topology, but it can also be used with half-wave rectifiers), which are used in AC to DC conversion. 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.įigure 1: Pi Filter at the output of a rectifierīefore we approach the Pi Filter, let us take a look at two simpler filters: the shunt capacitor and the L-section filter.
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Therefore, passive filters are widely applied in power transmission and converting applications. 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. Active filters are powerful tools capable of recovering very small signals and rejecting the rest of undesired noise. As explained in our previous article Introduction to Filter Circuits, filters are classified as active and passive filters. However, the most common application is signal rejection. They are used in impedance matching, harmonic oscillation, signal processing and control. Analog filters are some of the most fundamental and flexible structures in electrical engineering.