What are the main types of Electromagnetic Interference EMI?

Published : 07/07/2022 10:00:00

Continued technological evolution has led to an exponential increase in electronic components that accompany our lives. Telecommunication systems represent one of the fields that has evolved most emphatically, and many of these systems rely on wireless communication to transmit signals.

Although the benefits of this change are numerous there is no shortage of downsides, and among them we cannot fail to mention electromagnetic interference. Indeed, the inability to measure and counteract such interference can lead to the production and use of unreliable equipment, and it is therefore essential to understand the nature of these disturbances. So what do we mean by EMI and how can these interferences be reduced within switching power supply circuits.



EMI - Interferenze Elettromagnetiche



What is electromagnetic interference (EMI)?



Electromagnetic Interference (EMI) refers to all those signals that impair the operation of a telecommunications service. Any device with electronic circuits is susceptible to these disturbances, including the circuits of switching power supplies that are used daily for power conversion.

These unexpected signals can produce distortions, loss of information, interruptions within the data transmission process, and in borderline cases even damage switching circuits. Thus, electromagnetic interference is a cross-cutting phenomenon that must be taken into account especially within industrial, military, medical and aerospace projects, where the reliability and accuracy of electronic instruments must be maximized.



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What are the types of electromagnetic interference?



Electromagnetic interference can result from numerous sources, both natural and man-made. Broadly speaking, we can classify them into the following types:



Conducted or intentional EMI

This interference is generated by equipment designed to emit electromagnetic energy, such as radar and radio transmitters.



Radiated or unintentional EMI

These interferences are generated by equipment that involves the development of electromagnetic emissions only as a side effect; by way of example we give devices such as motors, converters, computers, power lines...



Intra-system EMI

In this case we are talking about interference produced within a system that goes to couple the signal from the source of the interference and the electronic system itself.



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How to reduce EMI in switch mode power circuits?



To avoid malfunction and damage caused by electromagnetic interference, it is essential to minimize its presence. There are several ways to reduce EMI in SMPS circuits, the most effective of which are as follows:

Linear systems

Although linear power supply designs tend to be bulkier, they certainly produce significantly less interference. These solutions are therefore preferable in terms of reducing electromagnetic interference.



Power modules

Power supply modules are often used as a quick and easy solution to reduce EMI. They are pre-packaged modules designed to provide a good combination of efficient power supply and good performance against radiated EMI.



Grounding systems

Grounding systems are essential to handle the return current, and several factors such as frequencies, impedances, and wiring length must be considered for proper setup. In some cases, it is also advisable to use a mix of grounding types to best handle any interference.



Electromagnetic shielding

Electromagnetic shielding is one of the most common methods used to reduce interference; by using a metal shield to enclose the electronic circuit, it is indeed possible to create a physical barrier between the source and destination of the interference, resulting in the weakening or attenuation of interference. The shield can consist of shielded or unshielded cables.



EMI Filter

Regarding conducted disturbances, using an inductor and capacitor (LC filter) in combination is the choice to be followed to mitigate any interference.



Optimized design

It may be trivial, but proper design is the simplest and most effective way to avoid EMI damage. Therefore, it is important to place the noisy nodes as far as possible from the sensitive nodes, design the ground plane below the EMI source, bundle the wires to reduce the loop area (radiated EMI), and use the EMI filter for conducted EMI.





What factors should be considered to mitigate the effects of electromagnetic interference?



With this in-depth study, we learned how challenging the design of switched-mode power supplies can be from the perspective of reducing electromagnetic interference. The technical characteristics and reliability of industrial power supply solutions proposed by Digimax comply with quality standards (including IEC/EN/UL62368, IEC/EN60335, IEC/EN61558 and GB4943).



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