Toroidal Electromagnetic Filter for Common and Differential Modes

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Solution Overview

Problem

Existing electromagnetic filters do not effectively address both common and differential mode operations while providing sufficient leakage inductance and thermal management for compact designs.

Innovation Solution

A dual-mode electromagnetic filter with a toroidal-like magnetic core and multiple coils, encapsulated by a thermal conductive magnetic compound, enhances leakage inductance and thermal link to a cooling plate, featuring a capacitor thermally isolated by polystyrene sheets and a nanocrystalline core.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If traditional electromagnetic filters are used for common mode operation, then common mode filtering is achieved, but differential mode filtering capability is insufficient

Engineering Contradiction:

Improvedifferential mode filtering capabilityVSAvoidfiltering effectiveness

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies universality by designing a single electromagnetic filter structure that performs both common mode and differential mode filtering functions. The toroidal magnetic core with specifically arranged coils enables the filter to handle both types of electromagnetic interference simultaneously, making one device serve multiple filtering purposes without requiring separate filters for each mode.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Volume of moving object

If filter components are arranged in a compact configuration, then space is saved, but thermal management becomes difficult

Engineering Contradiction:

Improvefilter volumeVSAvoidthermal dissipation

Core Design Contradiction:

Volume of moving objectVSTemperature

Solution Approach 1:

The patent applies nesting by placing the capacitor inside the hollow central region of the toroidal magnetic core. This nested arrangement allows the capacitor to be positioned within the space already defined by the magnetic core structure, achieving compact integration without requiring additional external space. The thermal management is facilitated by the inherent spacing and potential thermal pathways provided by this nested configuration.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Reliability

If leakage inductance is increased for better filtering, then filtering performance improves, but device complexity increases

Engineering Contradiction:

Improvefiltering performanceVSAvoidstructural complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies spheroidality by using a toroidal (doughnut-shaped) magnetic core instead of traditional linear or rectangular core structures. This curved, continuous toroidal geometry naturally provides the required leakage inductance for effective filtering while maintaining structural simplicity. The circular path of the magnetic flux in the toroid creates favorable magnetic properties without requiring complex winding arrangements or additional magnetic shielding components.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The filter achieves improved differential mode attenuation and mechanical integration with enhanced thermal management, offering over 20dB attenuation at 100k-1MHz and compatibility with customer cooling systems.

Implementation Method 1

a layer of a thermal conductive magnetic compound configured to enclose/encapsulate the toroidal-like magnetic core, the first, second and third coils, the capacitor, and the two sheets to: increase leakage inductance, to enclose/encapsulate the magnetic field generated by the third coil, and also to provide good thermal link to the customer cooling plate

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

Methodology Applied

Scientific EffectMagnetic field: Magnetic Field

Implementation Method 3

a toroidal-like magnetic core and first and second separated coils that are wound around the toroidal-like magnetic core, the first and second separated coils and the toroidal-like magnetic core being configured to provide a common mode filter

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentEP4390985B1An electromagnetic filter for operating in common and differential mode

Publication Date: 2025.09.10 PREMO SL

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AI summary

An electromagnetic filter for operating in common and differential mode is provided. The filter comprises a toroidal-like magnetic core; first and second separated coils wound around the magnetic core, the first and second coils and the magnetic core being configured to provide a common mode filter. The filter also has a third coil that surrounds the magnetic core and the first and second coils and arranged around a Z axis that is coaxial with an inner hollow part of the magnetic core, the third coil being configured to provide a filter operating in differential mode. Two sheets are also arranged between opposite external faces of a capacitor to thermally isolate the capacitor from the coils, the capacitor and sheets being arranged inside the inner hollow part. A layer of a thermal conductive magnetic compound encloses all the elements to increase leakage inductance and to enclose a magnetic field generated by the third coil.