The bypassed AC ripple goes into the inductor. Due to this low impedance across AC, the first capacitor of the Pi filter bypasses the AC ripple coming from the bridge rectifier. The capacitor provides low impedance in AC but a high resistance in DC due to the effect of capacitance and reactance. The output voltage across the pi filter is quite high making it suitable for the most power related application where high voltage DC filters are required.Ĭonfigured as a low pass filter In DC filtration purposes, Pi filter is an efficient filter, to filter out unwanted AC ripple coming from a bridge rectifier. Where, the Z 0 is the impedance characteristic in ohms and fc is the cut off frequency. Value of the capacitance is (C) = 1/4Z 0ᴫfc The construction and the component values of the Pi filter can be derived from the below equation – The above Pi Filter circuit image is showing the filter in high pass configuration, and not to mention the construction is also looking like a symbol Pi. Instead of a single inductor, here two separate inductors are used with a single capacitor. In low pass configuration the filter is designed as two capacitors are in parallel with an inductor in between, but in high pass configuration, the position and the quantity of the passive components get exactly the opposite. It is also made using two types of passive components, two inductors, and one capacitor. In such a case, the filter blocks the low frequency and allows the high frequency to pass. Same as the low pass filter, pi filters can also be configured as a high pass filter. Cut off frequency(fc) = 1/ᴫ(LC) 1/2 Value of the Capacitance is (C) = 1/Z 0ᴫfc Value of the inductance (L1) = Z 0/ᴫfc Where, the Z 0 is the impedance characteristic in ohms and fc is the cut off frequency. The construction and the component values of the Pi filter calculation can be derived from the below equation to design a Pi Filter for your application. Thus, it is commonly used in a transmission line to block unwanted high frequencies. As this is a low pass filter, it produces high impedance at high frequency and low impedance at low frequency. The Pi Filter circuit consists of two capacitors connected in parallel followed by an inductor in series forming a Pi shape as shown in the image belowĪs seen in the above image, it consists of two capacitors which are connected to ground with an in-between series inductor. The design of a low pass filter using the Pi configuration is pretty straightforward. When a Pi filter is designed for a low pass, the output remains stable with a constant-k factor. The Pi filter is an excellent low pass filter that is much more different than the traditional LC Pi filter. In low pass filter application, Pi filter also called the Capacitor input filter as the capacitor stays across the input side in low pass configuration. The main component of a Pi filter is the capacitor and inductor making it an LC filter. In majority, Pi filters are used for Low pass filter application, but another configuration is also possible. The construction arrangement of all the components creates the shape of the Greek letter Pi (π), thus the name Pi section Filter. Pi Filter is a type of passive filter that consists of mainly three components other than the traditional two-element passive filters. So, let’s get into detail on what these filters are and how to design them. We have already used Pi-Filter in a few of our previous Power supply designs like this 5V 2A SMPS circuit and 12V 1A SMPS Circuit. In this tutorial, we learn another new type of filter called Pi Filter, which is very commonly used in power supply circuit designs. We have already discussed in details about these filters: The active filter uses one or more active components with other passive components while passive filters are solely made using passive components. All these filters can be categorized into two types- Active filters and passive filters. There are many different types of filters used in electronic circuit designs based on the application but the underlying concept of all of them is the same, that is to remove unwanted signals. Filters are commonly used in power and audio electronics to reject unwanted frequencies.
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