EQUILIBRIUM-TYPE MAGNETIC FIELD DETECTION DEVICE
An equilibrium-type magnetic field detection device is provided with a magnetism detection unit that detects a magnetic field under measurement. According to a detection output from the magnetism detection unit, a cancel current is supplied to a feedback coil and a cancel magnetic field is supplied to the magnetism detection unit. The detection output is a coil current at a time when the magnetic field under measurement and the cancel magnetic field are placed in an equilibrium state. Since a plurality of magnetoresistance effect elements oppose a single coil conductor, it is possible to improve the linearity of detection outputs, reduce hysteresis, and increase detection sensitivity.
1 . An equilibrium-type magnetic field detection device comprising:
a feedback coil formed by winding at least one coil conductor around a flat surface;
at least one magnetism detection unit that has a plurality of magnetoresistance effect elements, each of which is formed in an elongated-strip shape along the at least one coil conductor;
a coil energization unit that supplies, to the at least coil conductor, a current that induces a magnetic field according to a detection output obtained when the at least magnetism detection unit detects a magnetic field under measurement, the magnetic field being directed so as to cancel the magnetic field under measurement; and
a current detection unit that detects an amount of current that flows in the at least coil conductor; wherein
in one of the at least one magnetism detection unit, the plurality of magnetoresistance effect elements are arranged in parallel and are connected in series, detection axes of the plurality of magnetoresistance effect elements being disposed in the same orientation, and
a plurality of magnetoresistance effect elements included in one of the at least one magnetism detection unit oppose one of the at least one coil conductor.
2 . The equilibrium-type magnetic field detection device according to claim 1 , wherein the plurality of the magnetoresistance effect elements preferably oppose a portion of the at least one coil conductor, the portion linearly extending.
3 . The equilibrium-type magnetic field detection device according to claim 1 , wherein each of the at least one coil conductor has a rectangular cross-sectional shape in which a dimension in a height direction is shorter than a dimension in a width direction, the magnetoresistance effect elements opposing a long side of the cross-sectional shape, the long side extending in the width direction of the cross-sectional shape.
4 . The equilibrium-type magnetic field detection device according to claim 1 , wherein the plurality of the magnetoresistance effect elements do not protrude from the at least one coil conductor in the width direction.
5 . The equilibrium-type magnetic field detection device according to claim 1 , further comprising a magnetic shield layer that reduces the magnetic field under measurement, which extends to the magnetoresistance effect elements.
6 . The equilibrium-type magnetic field detection device according to claim 1 , further comprising a current path, wherein
the magnetic field under measurement induced by the current path is supplied to the magnetoresistance effect elements.