Current sensor
The present invention provides a current sensor of smaller and simpler configuration, capable of measuring a current to be detected with high precision and stability. A current sensor has a V-shaped conductor line and a pair of magnetoresistive elements disposed along with the conductor line so that a resistance value of one of the magnetoresistive elements changes in a direction opposite to that of resistance-value-change of the other magnetoresistive element according to current magnetic fields produced by a current to be detected flowing through the conductor line.
1. A current sensor comprising:
a conductor line having a V-shaped flat surface, the V-shaped flat surface being spread over a two-dimensional plane; and
a pair of magnetoresistive elements disposed along with the conductor line so that a resistance value of one of the magnetoresistive elements changes in a direction opposite to that of resistance-value-change of the other magnetoresistive element according to current magnetic fields produced by a current to be detected flowing through the conductor line; and
a pair of bias applying means,
wherein one of the pair of magnetoresistive elements is disposed on a first arm portion of a pair of arm portions configuring a V shape of the conductor line,
the other of the pair of magnetoresistive elements is disposed on a second arm portion of the pair of arm portions, and
one side of the pair of magnetoresistive elements is disposed on one side of the first arm portion, and another side of the pair of magnetoresistive elements is disposed on one side of the second arm portion and detects the induction field induced by the current flowing through the opposing arm portions, and
the pair of magnetoresistive elements includes: a pinned layer having a magnetization direction pinned to a direction; a free layer whose magnetization direction changes according to an external magnetic field, while the magnetization direction under no external magnetic field is parallel or antiparallel to a direction in which the conductor line is extending; and an intermediate layer inserted between the pinned layer and the free layer; and
the magnetization direction of the pinned layer is parallel to the magnetization direction of the free layer when no external magnetic field is applied, and
the pair of bias applying means each applying a bias magnetic field to each of the pair of magnetoresistive elements, respectively, the bias magnetic field having a parallel component parallel to the magnetization direction of the pinned layer and an orthogonal component orthogonal to the parallel component.
2. The current sensor according to claim 1 , wherein the magnetization direction of the pinned layer is orthogonal to the magnetization direction of the free layer when no external magnetic field is applied.
3. The current sensor according to claim 2 , further comprising a pair of bias applying means each applying a bias magnetic field to each of the magnetoresistive elements in a direction same as that of the magnetization direction of the free layer under no external magnetic field.
4. The current sensor according to claim 3 , wherein the bias applying means is a magnetic sheet attached on one side of the magnetoresistive element.
5. The current sensor according to claim 1 , wherein the bias applying means is a magnetic sheet attached on one side of the magnetoresistive elements.
6. The current sensor according to claim 1 , further comprising:
a pair of constant current sources each supplying a constant current of a common magnitude to each of the magnetoresistive elements; and
a difference detector detecting a difference in the voltage drops resulting from the constant current in each of the magnetoresistive elements.