MAGNETIC-BALANCE-SYSTEM CURRENT SENSOR

• US 20120062215A1
• Filed: 11/18/2011
• Published: 03/15/2012
• Est. Priority Date: 06/12/2009
• Status: Active Grant

• Current Assignee: Alps Alpine Co., Ltd.
• Original Assignee: Alps Green Devices Co., Ltd. (Alps Alpine Co., Ltd.)
• Inventors: IDE, Yosuke, SAITO, Masamichi, TAKAHASHI, Akira, NOJIMA, Tsuyoshi, MIYAJIMA, Shigenobu, SAKATSUME, Naoki, ICHINOHE, Kenji, NISHIYAMA, Yoshihiro, KOGURE, Tatsuya, KOBAYASHI, Hidekazu, IIZUKA, Masahiro
• Granted Patent: US 8,519,704 B2
• Time in Patent Office: Days
• US Class Current: 324/202
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G01R 15/205 using magneto-resistance devices, e.g. field plates
• CPC Class Codes: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00

Abstract

A magnetic-balance-system current sensor includes: a magnetoresistive element, a resistance value of the magnetoresistive element being changed by applying an induction magnetic field generated by a measurement target current; magnetic cores disposed near the magnetoresistive element; a feedback coil disposed near the magnetoresistive element and configured to generate a cancelling magnetic field that cancels out the induction magnetic field; and a magnetic-field detecting bridge circuit having two outputs. The measurement target current is measured on the basis of a current flowing through the feedback coil when the induction magnetic field and the induction magnetic field and the cancelling magnetic field cancel each other out. The feedback coil, the magnetic cores, and the magnetic-field detecting bridge circuit are formed on a same substrate. The feedback coil is of a spiral type, and the magnetic cores are provided above and below the feedback coil.

Claims

1. A magnetic-balance-system current sensor comprising:

a magnetoresistive element, a resistance value of the magnetoresistive element being changed by application of an induction magnetic field generated by a measurement target current;

magnetic cores disposed in the vicinity of the magnetoresistive element;

a feedback coil disposed in the vicinity of the magnetoresistive element and configured to generate a cancelling magnetic field, the cancelling magnetic field being a field cancelling out the induction magnetic field; and

a magnetic-field detecting bridge circuit having two outputs having a voltage difference therebetween, the voltage difference being generated in accordance with the induction magnetic field,

wherein the measurement target current is measured on the basis of a current flowing through the feedback coil when electricity is conducted through the feedback coil due to the voltage difference and the induction magnetic field and the cancelling magnetic field enter a state of equilibrium in which the induction magnetic field and the cancelling magnetic field cancel each other out,

wherein the feedback coil, the magnetic cores, and the magnetic-field detecting bridge circuit are formed on a same substrate, and

wherein the feedback coil is of a spiral type, and the magnetic cores are provided above and below the feedback coil.

2. The magnetic-balance-system current sensor according to claim 1, wherein the magnetic cores are two magnetic cores, the magnetoresistive element is disposed between the two magnetic cores, and the magnetoresistive element and the magnetic cores are formed in a same plane.

3. The magnetic-balance-system current sensor according to claim 1, wherein the magnetic cores are provided so that an easy axis of magnetization coincides with a current direction of the feedback coil.

4. The magnetic-balance-system current sensor according to claim 1, wherein the feedback coil is provided so that a direction orthogonal to a direction in which the measurement target current flows is an axial center direction, and the magnetic cores are provided so that an easy axis of magnetization is orthogonal to the axial center direction.

5. The magnetic-balance-system current sensor according to claim 1, wherein the magnetoresistive element is a spin-valve-type giant magnetoresistive element or tunneling magnetoresistive element.

6. The magnetic-balance-system current sensor according to claim 5, wherein the giant magnetoresistive element has a meandering shape having a width ranging from 1 μ

m to 10 μ

m, a length in a longitudinal direction is equal or larger than twice the width, and the giant magnetoresistive element is disposed so that the longitudinal direction is perpendicular to both a direction of the induction magnetic field and a direction of the cancelling magnetic field.

7. The magnetic-balance-system current sensor according to claim 5, wherein the tunneling magnetoresistive element has a rectangular shape having a width ranging from 1 μ

m to 10 μ

m, a length in a longitudinal direction is equal or larger than twice the width, and the tunneling magnetoresistive element is disposed so that the longitudinal direction is perpendicular to both a direction of the induction magnetic field and a direction of the cancelling magnetic field.

8. The magnetic-balance-system current sensor according to claim 1, wherein the magnetic cores are formed of a high-magnetic-permeability material selected from a group constituted by an amorphous magnetic material, a permalloy magnetic material, and a ferrous microcrystalline material.