Current Sensor Shielding with Inverted Magnetic Structure

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Solution Overview

Problem

Current sensors face challenges in effectively suppressing external magnetic fields and achieving a low profile and strong fixation to the circuit board due to the arch-like structure of the magnetic substance portion and limited bonding area.

Innovation Solution

A current sensor design featuring a magnetism detection unit interposed between two opposing plates with a fixing member extending on both sides, a linking portion for enhanced shielding, and a low-profile configuration that integrates the shield and fixing members for improved stability and reduced external magnetic field influence.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If the magnetic substance portion is made arch-like to surround the magnetic sensor, then the external magnetic field influence is suppressed, but the circuit board size in the normal direction increases and the fixing area is reduced

Engineering Contradiction:

Improveexternal magnetic field influenceVSAvoidcircuit board size in normal direction

Core Design Contradiction:

Object-affected harmful factorsVSLength of stationary object

Solution Approach 1:

Instead of placing the magnetic substance portion above the circuit board in a conventional arch-like structure, the patent inverts the structure by placing it below the circuit board. The magnetic substance portion extends in the normal direction from the rear surface of the circuit board, surrounding the magnetic sensor from below rather than from above, thereby suppressing external magnetic field influence while reducing the overall height of the circuit board assembly.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If the magnetic substance portion is fixed with adhesive or soldering on the circuit board, then the magnetic sensor is protected, but the fixing area is small and fixing strength is lowered

Engineering Contradiction:

Improvemagnetic sensor protectionVSAvoidfixing strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent extends the magnetic substance portion in the normal direction of the circuit board to form a three-dimensional structure that surrounds the magnetic sensor. This dimensional extension transforms the fixing approach from a two-dimensional surface bonding (adhesive/soldering on the circuit board surface) to a three-dimensional structural integration, where the magnetic substance portion is fixed to the rear surface of the circuit board with extended legs that provide much larger fixing area and enhanced fixing strength.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Reliability

If the magnetic substance portion is resin-sealed in a package with the magnetic sensor, then the magnetic sensor is protected, but the profile in the normal direction increases

Engineering Contradiction:

Improvemagnetic sensor protectionVSAvoidprofile in normal direction

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

Instead of placing the resin seal and magnetic substance portion above the magnetic sensor (which would increase the profile in the normal direction), the patent inverts the structure by placing these protective elements below the circuit board. The magnetic substance portion extends downward from the rear surface of the circuit board, and the resin seal encapsulates this inverted structure, thereby protecting the magnetic sensor while maintaining a low-profile circuit board assembly.

Inventive Principle:

Principle #13The other way round (Inversion)

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 design significantly reduces external magnetic field interference, enhances fixing strength, and achieves a low profile, resulting in high shield performance and precise magnetic field measurement.

Implementation Method 1

a shield member that can block an external magnetic field

Methodology Applied

Scientific EffectMagnetic shielding: Magnetic Field

Implementation Method 2

a magnetism detection unit that can detect a component of a magnetic field generated when a current flows in a current path

Methodology Applied

Scientific EffectMagnetic field detection: Magnetic Field

Data Source

PatentUS20230034792A1Current sensor

Publication Date: 2023.02.02 ALPS ALPINE CO LTD

AI summary

A current sensor has: a magnetism detection unit that can detect a component, in a first direction, of a magnetic field generated when a current flows in a current path; a shield member that can block an external magnetic field; a circuit board on which the magnetism detection unit is mounted; and a fixing member, composed of a magnetic material, that fixes the shield member to the circuit board. The first direction is parallel to the front surface of the circuit board. The shield member has two opposing plates placed so that their plate surfaces face each other in the first direction. The magnetism detection unit is placed by being interposed between the two opposing plates in the first direction. The fixing member extends toward both sides of the magnetism detection unit in the first direction when viewed along the normal of the front surface of the circuit board.