Inductor Core Segmentation for MRI Saturation Resistance

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Solution Overview

Problem

Implantable medical devices face operational issues due to magnetic field saturation, particularly in strong MRI fields, which can lead to voltage loss and impaired therapy delivery in devices like implantable cardioverter-defibrillators.

Innovation Solution

An inductive component with a core comprising two portions: a first portion made of a material with a low magnetic saturation level, such as ferrite, and a second portion made of a high permeability iron alloy, allowing for effective inductance in both weak and strong magnetic fields.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a ferrite core is used in an inductive component, then inductance is provided in weak magnetic fields, but the core saturates when exposed to strong magnetic fields (above 0.35 Tesla)

Engineering Contradiction:

Improveinductance provision in weak magnetic fieldsVSAvoidmagnetic field saturation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The core is divided into two distinct portions: a first portion made of ferrite material for operating in weak magnetic fields, and a second portion made of high permeability iron alloy for operating in strong magnetic fields. This segmentation allows each portion to be optimized for its specific magnetic field range, preventing saturation while maintaining inductance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The core uses a composite structure combining two different magnetic materials with complementary properties. The ferrite portion provides low-loss operation in weak fields, while the high permeability iron alloy portion provides saturation resistance in strong fields, creating a core that performs reliably across the full magnetic field range.

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If a high permeability iron alloy is used for the core, then saturation resistance in strong magnetic fields is improved, but other magnetic properties such as permeability and bulk conductivity are not appropriate for IMD applications

Engineering Contradiction:

Improvemagnetic field saturation resistanceVSAvoidmagnetic property suitability for IMD

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

Different portions of the core have different material properties optimized for their specific function. The ferrite portion has properties suitable for weak field operation with appropriate permeability and low conductivity, while the high permeability iron alloy portion has properties optimized for strong field saturation resistance. Each material's properties are locally optimized rather than requiring uniform properties throughout the entire core.

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If the inductive component uses a single material core, then device simplicity is maintained, but the component cannot operate effectively in both weak and strong magnetic field environments

Engineering Contradiction:

Improveoperation in varying magnetic field environmentsVSAvoidcore structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The core is segmented into two portions with different materials, where the first portion (ferrite) handles weak magnetic field operation and the second portion (high permeability iron alloy) handles strong magnetic field operation. This segmentation enables the inductive component to adapt to varying magnetic field environments while maintaining a relatively simple integrated core structure.

Inventive Principle:

Principle #1Segmentation

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

Enables continuous operation of implantable medical devices by maintaining inductance across varying magnetic field strengths, ensuring reliable therapy delivery even during MRI scans.

Implementation Method 1

the first portion can be composed of a material having a low magnetic saturation level (e.g., a ferrite)

Methodology Applied

Scientific EffectFerromagnetism: Ferromagnetism

Implementation Method 2

the second portion can be composed of a material having a high magnetic saturation level (e.g., a high permeability iron alloy)

Methodology Applied

Scientific EffectFerromagnetism: Ferromagnetism

Data Source

PatentUS8390418B2Apparatus and method for reducing inductor saturation in magnetic fields

Publication Date: 2013.03.05 CARDIAC PACEMAKERS INC

AI summary

This document discusses, among other things, an inductive component that can include a core having two portions: (1) a first portion composed of a first material having a first magnetic saturation level; and (2) a second portion composed of a second material selected to provide inductance for the inductive component when an external magnetic field is greater than the first magnetic saturation level. In an example, the first portion can be composed of a material having a relatively low magnetic saturation level (e.g., a ferrite), and the second portion can be composed of a material having a relatively high magnetic saturation level (e.g., a high permeability iron alloy).