EMI Filter Applications and Uses

EMI Means Electromagnetic Interference. It is a disturbance in the radio frequency spectrum by an external source and it affects the electrical circuits. Electromagnetic interference may affect the working of the electrical or electronic circuits that perform any vital operations. The EMI filter is basically an electronic circuit that can reduce the EMI effects or block the unwanted EMI signals so a circuit can work properly without any effects.

Some common applications of EMI Filters are,

• Mobile Charger Circuit
• Smart Battery Charger Circuit
• AM Radio Circuit
• FM Radio Circuit
• Television
• Medical Equipment
• Electronic Warfare System
• Radio Jammer Circuit
• Telecommunication Circuits
• Switched Mode Power Supply Circuit
• High-Frequency Power Converters

Electromagnetic Interference may happen due to direct physical contact with the EMI or induction where physical contact is not available. It can be categorized into two types - broadband EMI and narrowband EMI. Narrowband EMI happens from the sources of Radio signals and electromagnetic signals processing devices such as Radios, TV stations, and Mobile Phones. On the other hand, broadband EMI happens from the source of electrical power transmission lines. Of course here also the frequency has a very important role.

EMI filters are used in power converters circuits such as DC-DC converters, Converters, Rectifiers, and Inverters because they create interferences due to their high-frequency switching operations.

EMI can decrease the listening experience of the radios. Even it can make the picture quality blur on televisions. So these devices also use EMI Filters.

There are two types of EMI filters are available - Active EMI Filter and Passive EMI Filter.

Active filters are built with active components and they need an external power supply for their own internal circuitry. On the other hand, passive filters are built with passive components and they mainly depend upon the impedances of the surrounding electrical system. Passive filters have more advantages than active filters such as they provide guaranteed stability, can handle a large signal, and they are less expensive. 

Passive EMI filters are mostly used in Power Converter circuits, power distribution networks, speaker crossover circuits, monolithic integrated circuits, and hybrid integrated circuits whereas Active Filter Circuits are mainly used in signal processing devices.

Nowadays, you will see there are huge applications of EMI filters in consumer devices also. For example, EMI Filters are used in,

• Electric Blanket
• Electronic Doorbell(used with its transformer)
• Toaster Ovens
• Electric Bug Zappers
• Heating Pads
• Touch Controlled Lamps
• CRT Monitors

Most of the wireless devices and power supply devices especially that deliver more than 2A current can generate a huge amount of electromagnetic interference. A ferrite bead or ferrite core noise suppressor is a very inexpensive EMI suppressor device. It just has to be clipped onto the power lead of the power supply devices. Also, a very common and easy method to suppress EMI is using of a snubber network. It is a circuit where a resistor is connected in series with a capacitor but remember that it cannot be used for a high-current circuit. Generally, it works well below the 2A current.

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Read Also: 

• Electronic Band Pass, Band Reject, Low Pass, High Pass Filter Symbol
• What is Dynamic Noise Reduction(DNR)? Explained
• What is Clipper Circuit or Clippers? Applications, Types
• Band Pass Filter Applications, Examples, Advantages, Types
• [Exact] Difference between Coupling Capacitor and Bypass Capacitor

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