App note: The behavior of electro-magnetic radiation of power inductors in power management


Application note form Würth Elektronik about EM radiation radiated from inductors in DC-DC converters. Link here (PDF)

This Application Note focuses on the Electro-Magnetic (EM) radiation behavior of power inductor(s) in DC-DC converters, which is dependent on several parameters such as ripple current, switching frequency, rise & fall time of a switching device, the core material and its permeability and suggests several design tips to mitigate these EMI effects.

App note: Consideration of self-pollution reduction for electronic systems


App note from ON Semiconductors discussing how locally generated EMI affects its own system and how to prevent it. Link here (PDF)

This application note will address the problem of Electro Magnetic Interference (EMI) self pollution in which one part of an electrical systems such as cell phones and consumer electrical products emit radiation that interferes with the operation of other parts of the system.

Build Your Own EMI Probes

[Gerald Musy] wanted to investigate the source of electromagnetic interference (EMI) in his switching power supply design. Stymied by the high cost of EMI probes, he decided to build his own. Lucky for us, he wrote up his results of experimenting with four different designs.

The probes include an unshielded loop, a shielded loop, a ferrite core probe, and an electric field probe. None of these are especially complex to build–the ferrite core one is probably the most involved–you can see from the scope traces that the different probes pick up different information.

Of course, once you identify where the EMI is coming from, your next task is what to do about it. The probes won’t help you figure that out, but identifying the source of the interference is a critical first step.

Some scope probes are very expensive commercially. Building your own can be a viable alternative. We’ve also used the old syringe trick to make specialized probes for many years.

Filed under: tool hacks

App note: Going wireless with magnetic shielding

Efficient magnetic shielding application note from Würth Elektronik, Link here (PDF)

Magnetic Field Interferences are increasing in electronic devices due to a number of factors including reduced separation distances of PCB’s, Integrated Circuits and many other sensitive components. In addition to this the extended use of magnetically coupled communication technologies (Qi-WPC, NFC, RFID, PMA, A4WP, WCT…) leads to more complex layout and proximity considerations.

With Ferrite materials it is possible to manage and predict magnetic flux flow and thereby improve efficiency of power transfers, increase distances of near field communications and of course avoid additional unwanted coupling effects which could lead to losses or noise.