Desing System
Addressing EMI challenges in power electronics based on WBG semiconductors
Niobium-bearing nanocrystalline magnetic materials support compact, thermally stable, and high-performance EMI filters for Wide-bandgap (WBG) power converters.
Wide-bandgap (WBG) semiconductor devices such as Silicon Carbide (SiC) MOSFETs and Gallium Nitride (GaN) HEMTs are transforming modern power electronics.
Their material properties enable lower conduction and switching losses, higher switching frequencies, and improved thermal capability compared with traditional silicon devices.
These advantages drive higher efficiency and power density in applications such as electric vehicles, renewable energy systems, industrial power supplies, and data centers. However, higher switching speeds also increase dv/dt and di/dt, intensifying conducted electromagnetic interference and making EMI control a fundamental design requirement in WBG-based power converters.
Traditional MnZn ferrite-based CMCs show limitations in high-frequency SiC and GaN applications due to reduced permeability at higher frequencies and strong temperature dependence. These constraints often result in larger components and conservative design margins.
Niobium-bearing nanocrystalline magnetic materials address these limitations by offering high permeability, high saturation flux density, and stable magnetic behavior across wide temperature ranges.
In the frequency range most critical for wide-bandgap (WBG) power converters, nanocrystalline common-mode choke consistently outperform traditional ferrite-based solutions.
This enables either smaller EMI filters for the same attenuation target or improved noise suppression without increasing converter size.
(A) Comparison of insertion loss of CMC made of nanocrystalline and ferrite with similar attenuation properties at 1 MHz.
. Nanocrystalline: 16*10*6 mm, N=18
. Ferrite: 25*15*10 mm, N=26
(B) Comparison of insertion loss of CMC made of nanocrystalline and ferrite with similar size and windings.
. Nanocrystalline: 25*16*10 mm, N=26
. Ferrite: 25*15*10 mm, N=26
Source: Vacuumschmelze. (2023). EMC Products based on Nanocrystalline VITROPERM [Brochure]. www.vacuumschmelze.com
Nanocrystalline CMCs maintain nearly constant insertion loss across a wide temperature range, typically from –40 °C to 120 °C.
This thermal stability reduces the need for conservative design margins and helps simplify qualification processes, particularly in high-reliability and wide-temperature applications.
Source: Vacuumschmelze. (2023). EMC Products based on Nanocrystalline VITROPERM [Brochure]. www.vacuumschmelze.com
By enabling compact, reliable EMI filters, nanocrystalline CMCs help designers meet stringent EMI requirements without compromising efficiency or converter footprint. Together, these characteristics make Niobium-bearing nanocrystalline materials a key enabler for compact, high-performance EMI filters in next-generation WBG power converters.
What is a common-mode choke (CMC) and why does it matter in EMI filters?
If you work with power electronics, you’ve likely seen that the common-mode choke (CMC) plays a central role in EMI filters. Its primary function is to suppress common-mode noise by presenting high impedance to common-mode currents. In practice, the CMC largely defines how effective, compact, and robust an EMI filter can be, especially in high-frequency switch-mode power supplies where common-mode noise dominates.
Why do SiC MOSFETs and GaN HEMTs increase EMI at higher frequencies?
As power electronics transition to silicon carbide (SiC) MOSFETs and gallium nitride (GaN) HEMTs, switching speeds increase significantly. Owing to their smaller die area and lower parasitic capacitances, these devices exhibit much faster voltage and current transitions, resulting in higher dv/dt and di/dt. While this enables higher efficiency and power density, it also pushes EMI toward higher frequency ranges. Consequently, EMI mitigation in WBG-based converters becomes more challenging than in systems using conventional silicon devices.
How do nanocrystalline magnetic materials differ from MnZn ferrite in EMI filters?
When designing EMI filters, you may notice that MnZn ferrite cores start to show limitations at higher frequencies. Nanocrystalline magnetic materials behave differently: they offer much higher permeability, allowing the same or higher impedance with fewer turns. This translates into smaller cores, less copper, and lower parasitic capacitances. As a result, nanocrystalline cores provide broadband attenuation at high frequencies for SiC and GaN applications.
How stable is EMI attenuation over temperature with nanocrystalline CMCs?
In real-world applications – automotive, industrial, or energy – temperature matters. Nanocrystalline CMCs maintain nearly constant insertion loss from –40 °C to 120 °C, which is a clear contrast to ferrite solutions that vary significantly with temperature. For designers, this stability reduces uncertainty during validation and minimizes the need for conservative safety margins.
What role does Niobium play in nanocrystalline magnetic materials?
You may wonder what enables nanocrystalline materials to deliver such stable performance. Niobium is a key enabler in this process. It helps stabilize the nanocrystalline structure during manufacturing, controlling grain growth, which is essential for achieving superior magnetic properties like high permeability. This microstructural stability directly translates into predictable, broadband EMI suppression, making nanocrystalline materials well suited for high-frequency SiC and GaN power electronic applications.
What defines a Wide-Bandgap (WBG) power converter and how does it impact EMI filter design?
A Wide-Bandgap (WBG) power converter is typically based on SiC MOSFETs or GaN HEMTs to achieve higher efficiency, higher switching frequencies, and greater power density. These performance gains are enabled by fast switching transitions and reduced switching losses, but they also lead to significantly higher dv/dt and di/dt, and wider-band EMI spectra. That’s why EMI filters, and especially the magnetic material used in the common-mode choke, become critical elements in WBG converter architectures.