EMC
Addressing power supply systematic failures: improving electromagnetic immunity
By Bryan Angelo Borres, senior functional safety engineer, and Camille Bianca Gomez, senior product applications engineer, Analog Devices
E
lectromagnetic immunity is a critical requirement for power supplies in safety-related systems because electromagnetic disturbances can lead to dangerous failures if safety functions are compromised. Functional safety standards and related electromagnetic compatibility (EMC) standards such as IEC 61508, IEC 61000-1-2, and IEC 61326-3-1 demand higher immunity levels, stricter test margins, and robust design measures to ensure reliable system operation under harsh electromagnetic environments. While traditional discrete components such as ferrite beads, RC snubbers, transient-voltage suppressors (TVS), and metal oxide varistors (MOV) provide useful baseline protection, they often fall short when dealing with high energy surges, tight voltage tolerances, and increasing system complexity. To address these challenges, Analog Devices offers advanced integrated solutions – including surge stoppers, ideal diode controllers, eFuses, and high-side drivers – that significantly enhance electromagnetic immunity and simplify compliance with functional safety requirements.
Introduction
Power supplies have stringent electromagnetic compatibility (EMC) requirements because they are the first block in the electrical path, acting as the primary interface between the noisy power grid and sensitive electronics. As the first stage, they are both the largest source of noise and the primary barrier against incoming interference. Examples of EMC standards relevant to power supplies can be seen in Table 1. This includes standards addressing electromagnetic interference (EMI), as well as electromagnetic susceptibility (EMS), which focuses on immunity.
Under EMC, we have EMI and EMS. EMS (electromagnetic susceptibility) is otherwise known as electromagnetic immunity, which is important in functional safety. A safety-related system (SRS) with great vulnerability to electromagnetic disturbance may have its safety function lost when needed, thus causing a dangerous failure. With such, the basic functional safety standard IEC 615083
38 June 2026
Figure 1. (a) Traditional TVS solution for voltage spikes with (b) I-V characteristic waveform for unidirectional TVS.
provides guidance and requirements for electromagnetic immunity.
What does IEC 61508 say about electromagnetic immunity? The basic functional safety standard IEC 61508 specifies electromagnetic disturbance as one of the environmental stresses that SRS shall be tolerant against. Regardless of safety integrity level (SIL), employing measures to increase immunity to EMI is mandatory. Depending on the SIL, required levels of effectiveness can range from low to high. Low effectiveness may refer to the application of a noise filter at the power supply or critical ports, as well as using shielding. Meanwhile,
Standard Reference Number
Description
EN 55032 and EN 55011 Conducted and radiated EMI emitted by the power supply IEC/EN 61000-3-2
IEC/EN 61000-3-3
IEC/EN 61000-4-2 IEC/EN 61000-4-3 IEC/EN 61000-4-4 IEC/EN 61000-4-5 IEC/EN 61000-4-6 IEC/EN 61000-4-8
Components in Electronics
high effectiveness may refer to using a filter against the worst EMI.3,4
electromagnetic immunity requirements?
IEC 61508 provides EMC requirements as shown in Table 2. It references IEC 61000-1-2 and IEC 61326-3-1 standards for the corresponding electromagnetic immunity limits and safety margins.3,4 Notably, IEC 61000-1-25
provides a
methodology to achieve functional safety in SRS considering EMC, where it shows examples of conditions to increase the test severity compared to the requirements in
the basic standard. This is done to increase the level of confidence regarding immunity against electromagnetic disturbance when having higher SIL requirements. Meanwhile, the IEC 61326-3-1,6
an EMC standard for
electrical equipment for measurement, control, and laboratory use in industrial applications, provides immunity requirements for SRS. We have the enclosure port, AC and DC input and output ports, input/output control ports, which shows that complying with higher SIL increases the severity of certain test parameters by a corresponding factor with respect to the basic standard. Furthermore, both standards specified the application of a performance criterion DS,6 which specifies a required operation for safety-related functions and nonsafety-related functions, as opposed to the usual performance A, B, and C of EMC standards.4-7 With functional safety compliance, an SRS
Limits to the harmonic currents that can be taken from the input line
Limits to the voltage fluctuations that the power supply can cause to the line input voltage
Immunity to electrostatic discharge Immunity to radiated radio frequencies
Immunity to fast transient voltages on the input lines Immunity to lightning surges on the input lines Immunity to conducted radio frequencies
Immunity to power mains frequency magnetic fields Table 1. Examples of power supply relevant EMC standards1,2
is required to comply with more stringent EMC requirements to improve robustness against electromagnetic disturbance and ensure that safety functions will work when demanded or as designed. Aside from this, an SRS may not fail immediately when exposed to high levels of stress, but its reliability may be impacted, which can result in its lifetime being shortened, thus no longer meeting the reliability assumptions during the safety analysis. For this reason, employing different techniques to protect downstream components from electromagnetic disturbances has become the norm.
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