What are the main types of Electromagnetic Interference EMI?

The continuous technological evolution has led to an exponential increase in electronic components that accompany our lives. Telecommunication systems are one of the fields that has evolved with greater emphasis and many of these systems rely on wireless communication for the transmission of signals.

Although the advantages of this change are numerous, there are also negative aspects, and among all we cannot fail to mention electromagnetic interference. 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.

Electromagnetic Interference (EMI) refers to all those signals that compromise the functioning of a telecommunications service. Any device equipped with electronic circuits is susceptible to these disturbances, including switching power supply circuits that are used daily for the conversion of electrical energy.

These unexpected signals can produce distortions, loss of information, interruptions within the data transmission process and in extreme cases even damage the switching circuits. Electromagnetic disturbances therefore represent a transversal phenomenon that must be taken into account, especially within industrial, military, medical and aerospace projects, where the reliability and precision of electronic instruments must be maximum.

Electromagnetic interference can come from many sources, both natural and artificial. Generally speaking, we can classify them into the following types:

Conducted or intentional EMI

These interferences are generated by equipment designed to emit electromagnetic energy, such as radar and radio transmitters.

Radiated or unintentional EMI

These disturbances are generated by equipment that foresee the development of electromagnetic emissions only as a collateral effect; for example, we report devices such as motors, converters, computers, power lines...

Intrasystem or coupled EMI

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

To avoid malfunctions 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:

Linear systems

Although linear power supply designs tend to be bulkier, they certainly produce significantly less interference. These solutions are therefore preferable when it comes to reducing EMI.

Power modules

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

Grounding systems

Grounding systems are essential to manage the return current and correct setup requires consideration of several factors such as frequencies, impedances and length of wiring. In some cases, it is also advisable to use a mix of grounding types to best manage any interference.

Electromagnetic shielding

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

EMI filter

For conducted interference, the combination of an inductor and a capacitor (LC filter) is the choice to follow to attenuate any interference.

Optimized design

It may seem trivial but an adequate design is the simplest and most effective method to avoid damage due to EMI. It is therefore important to position the noisy nodes as far as possible from the sensitive nodes, design the ground plane below the EMI source, group the wires to reduce the loop area (radiated EMI) and use the EMI filter for conducted EMI.

With this insight we have learned how challenging it can be to design switching power supplies from the point of view of reducing electromagnetic interference. The technical characteristics and reliability of industrial power solutions proposed by Digimax comply with quality standards (including IEC/EN/UL62368, IEC/EN60335, IEC/EN61558 and GB4943).