Mitigating Growing EMI Challenges from High-Efficiency Power Systems
Key Highlights
- Wide-bandgap semiconductors such as SiC and GaN improve efficiency but can increase conducted EMI in power systems.
- Design choices like power stage topology and grounding significantly impact EMI propagation and mitigation efforts.
- Higher switching frequencies, while beneficial for efficiency, broaden spectral bandwidth and can interfere with sensitive equipment.
Around 2020, Tesla stopped putting AM radios in its vehicles. Tesla and other makers of electric vehicles (EVs) asserted that electrical noise from high-frequency switches and electronic equipment built on wide-bandgap semiconductors ruined reception.[1] Conventional FM radios are less severely affected, but they are also being phased out.[2]
Electromagnetic interference (EMI) can be an annoyance to radio listeners, but in industrial environments, EMI problems are increasing as today’s power systems scale up to improve efficiency. On this larger scale, the effects are more damaging than poor reception.
Today’s power systems are designed for efficiency. A common tactic is the use of variable-frequency drives for motors, allowing speeds to be optimized while minimizing power consumption. Such systems increasingly depend on silicon carbide (SiC) and gallium nitride (GaN) components rather than traditional silicon, due to their wide-bandgap characteristics, which permit better performance in high-voltage, high-temperature, and high-frequency applications. The result is lower power consumption and higher power density, which are important in challenging applications such as EVs.
Electronic equipment used in these applications must be tested for electromagnetic compatibility (EMC) in accordance with multiple standards and protocols. These testing methods also evaluate EMI characteristics. Passing EMC is typically required for market access and helps reduce the risk of interfering with nearby equipment and infrastructure.
This blog discusses how high-efficiency power conversion using SiC and GaN devices is increasing conducted EMI in modern industrial and energy systems, and how proper front-end filtering helps mitigate those effects.
High Efficiency as Baseline
Designing electrical equipment involves balancing complex trade-offs, with market forces determining priority. Modern design cycles frequently prioritize early optimization for power level, efficiency, cost, and power density. This is understandable, but it deprioritizes EMI concerns. The highest practical switching speeds are applied for each type of transistor, SiC for its high power handling and GaN for its high speeds. Designers push these to their edge rates to deliver maximum performance, always trying to squeeze out more efficiency, thermal margin, and power density to reach platform-level performance targets. Some EMI-minimizing mechanisms are built in, but they stop short of impacting performance. When the desired characteristics are optimized, producers hope that the product will still pass EMC testing.
The basic architecture of a system and its resulting current paths determine how conducted EMI propagates. When currents flow through circuit imbalances or certain parasitic circuit elements, it creates conducted EMI. This type of interference can also be created by PC board trace inductances and capacitances. The resulting noise can couple to other areas of the circuit magnetically (inductive) or electrically (capacitive).
The following design choices can influence these effects:
- Power stage topology—The arrangement of switches, diodes, inductors, etc., for efficient power conversion.
- DC-link and input network structure—The intermediate stage that decouples the primary source from downstream power-conversion stages.
- Cable length, grounding scheme, and enclosure design—Good configuration choices minimize undesired output.
Once designers make these choices, correcting for their effects later via local tuning becomes very difficult. Careful choices early on are critical.
How EMI Results from High-Efficiency Designs
EMC testing labs (Figure 1) closely examine equipment. While they cannot determine the equipment’s efficiency during a test, they can draw conclusions from the configuration about how much EMI a given design is likely to generate.
Designers often undermine their own efforts by raising switching frequencies to achieve higher efficiency. However, pushing frequencies to edge rates to reduce switching losses increases the noise’s spectral bandwidth. Unfortunately, some frequency ranges and their harmonics cause problems with other types of equipment, including various medical devices. EMC testers are mostly concerned with frequencies between 150kHz and 30MHz for conducted EMI, as these frequencies cause the greatest interference with specific classes of consumer, medical, and industrial equipment.
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Author
Peter Welander, now semiretired, has been working as a freelance writer and editor for more than 10 years, following seven years as a senior editor and content manager for Control Engineering magazine. During this time he has written heavily about industrial automation, primarily in process industries. Responsibilities have also included audio and video production, podcasts, and blogging.
Moving into the publishing world followed many years working in sales and marketing management, engineering, and operations for a variety of industrial manufacturers. One capability that he has had throughout his career is the ability to grasp technical concepts and explain complex ideas clearly. His personal interests include photography, a machine shop, woodworking, and pipe organ building.
[1] https://spectrum.ieee.org/am-radio-ev-interference
[2] https://www.ceoutlook.com/2026/01/15/car-makers-remove-am-fm-what-it-means-for-12-volt/
