JP6099588B2 - Magnetically coupled isolator - Google Patents

Description

  In the present invention, when transmitting and receiving signal information while electrically insulating two circuits, the signal superimposed on the current flowing in the transmitting circuit is changed to a magnetic field so that the signal is electrically insulated from the transmitting circuit. The present invention relates to a magnetically coupled isolator that detects a change in resistance of a magnetic sensor attached to a receiving circuit.

  In electric vehicles, industrial robots, etc., there are a high-voltage circuit in which a high-voltage current that drives a motor flows and a low-voltage circuit in which a low-voltage current that operates a microcomputer for controlling the motor flows. Control signals are sent and received between them. At this time, if the signal is transmitted / received in a state where the high voltage circuit and the low voltage circuit are electrically connected, the low voltage circuit may malfunction due to a voltage on the high voltage circuit side or a malfunction may occur. . Therefore, a circuit element capable of transmitting a signal while electrically insulating the high voltage circuit and the low voltage circuit is used. As such a circuit element, there is a magnetically coupled isolator that transmits a signal through a magnetic field generated by a current.

  For example, Japanese Unexamined Patent Application Publication No. 2012-227517 uses a microtransformer in which one planar coil is used for each of the high voltage circuit side and the low voltage circuit side, and an electrical insulating layer is formed between the planar coils. A temperature detection device is described. This is because two circuits that are insulated by flowing a current with a superimposed signal through one planar coil to generate a magnetic field according to the magnitude of the current and detecting the generated magnetic field with the other planar coil. It is possible to send and receive signals between them. As described above, when a signal is transmitted while insulating between two circuits of a high voltage and a low voltage, a method using a magnetic field generated by a current is generally used.

  International Publication No. 2010/032825 discloses a planar coil and a magnetoresistive effect element whose resistance is changed by a magnetic field, particularly a giant magnetoresistive (GMR) element or a tunneling magnetoresistive (TMR). ) A magnetically coupled isolator using elements is described. In this magnetic coupling type isolator, an insulating film is formed on the upper part of the laminated film structure of the magnetoresistive effect element, and a planar coil is formed thereon. When a current with a signal superimposed thereon is passed through the planar coil, the magnetic field generated thereby is applied in the magnetosensitive effect direction of the magnetoresistive element, and the resistance of the magnetoresistive element changes. At this time, if a constant current is applied to the magnetoresistive element, the change in resistance becomes a change in voltage, so that the signal can be measured as a voltage value.

JP2012-227517A International Publication No. 2010/032825

  However, in a magnetically coupled isolator using a planar coil, magnetic fields in opposite directions are generated simultaneously when current lines flowing in different directions are adjacent to each other. These magnetic fields interact with each other to reduce the strength of the magnetic field detected by the magnetic field detection device. Therefore, it is necessary to provide a large planar coil and increase the distance between coils flowing in different directions. Therefore, such a magnetically coupled isolator has a problem that it is difficult to reduce the size.

  The present invention has been made to solve the above-described problems. A main object of the present invention is to provide a magnetically coupled isolator that can be reduced in size as compared with a conventional magnetically coupled isolator.

  A magnetically coupled isolator according to the present invention includes a signal current line for flowing a current with a signal superimposed thereon, a magnetic field detection device for detecting a magnetic field generated by a current flowing through the signal current line, and the signal current. The signal current line is configured to apply a magnetic field to the magnetic field detection device in one direction, and the magnetic field detection The apparatus includes a magnetoresistive element having a major axis and a minor axis perpendicular to the major axis, the magnetoresistive element comprising an antiferromagnetic layer, a first ferromagnetic layer, a nonmagnetic layer, and a shape The first ferromagnetic layer has a laminated structure in which a second ferromagnetic layer having magnetic anisotropy and having a magnetization direction oriented in the direction along the major axis in a magnetic field is sequentially laminated. The magnetization direction is generated by the current flowing through the signal current line. That is fixed in the direction along the direction of the magnetic field, the magnetization direction of the second ferromagnetic layer is changed according to a magnetic field generated when a current flows through the signal current line.

  According to the present invention, it is possible to provide a magnetically coupled isolator that can be reduced in size as compared with a conventional magnetically coupled isolator.

1 is a perspective view for explaining a magnetically coupled isolator according to a first embodiment. FIG. 2 is a top view for explaining the magnetic field detection device according to the first embodiment. FIG. 3 is a cross-sectional view for explaining the magnetoresistive effect element according to the first embodiment. FIG. 3 is a cross-sectional view for explaining the magnetoresistive effect element according to the first embodiment. FIG. 10 is a top view for explaining a modification of the magnetic field detection device according to the first embodiment. 4 is a graph showing a relationship between a signal current and electric resistance of the magnetic field detection device according to the first embodiment. 6 is a top view for explaining a magnetically coupled isolator according to a second embodiment. FIG. FIG. 5 is a cross-sectional view for explaining a magnetically coupled isolator according to a second embodiment. FIG. 6 is a top view for explaining a magnetic field detection device according to a third embodiment. FIG. 6 is a top view for explaining a magnetic field detection device according to a fourth embodiment. 10 is a graph showing a relationship between a signal current and electric resistance of the magnetic field detection device according to the fourth embodiment. FIG. 10 is a top view for explaining a magnetic field detection device according to a fifth embodiment. FIG. 10 is a perspective view for explaining a magnetically coupled isolator according to a sixth embodiment. FIG. 10 is a cross-sectional view for explaining a magnetically coupled isolator according to a sixth embodiment. FIG. 10 is a top view for explaining a magnetically coupled isolator according to a sixth embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
First, the magnetically coupled isolator 100 according to the first embodiment will be described with reference to FIGS. In the magnetically coupled isolator 100 according to the first exemplary embodiment, the signal current line 1 through which a signal superimposed current flows on the back surface of the insulating substrate 2 and a magnetic field generated by the current flowing through the signal current line 1. The magnetic field detection device 10 to be detected is provided on the surface of the insulating substrate 2.

  The signal current line 1 is provided so as to extend linearly along the Y direction in the drawing. In other words, the signal current line 1 is not a planar coil. That is, the signal current line 1 applies a unidirectional magnetic field to the magnetic field detection device 10 described later.

  The cross-sectional shape in a plane (XZ plane in the drawing) perpendicular to the current direction of the signal current line 1 is rectangular. The long side length L of the signal current line 1 in the cross section is longer than the thickness T of the insulating substrate 2. In this way, the current flowing in the normal direction (Y direction) of the cross section in the signal current line 1 having a rectangular cross section is from the signal current line 1 with respect to the length L of the long side in the cross section. In a place where the distance is short, the surface current is obtained. As a result, the distance dependency of the strength of the magnetic field generated by the current flowing through the signal current line 1 can be reduced, and a sufficiently strong magnetic field is generated in the region where the magnetic field detection device 10 is provided. be able to. In general, the magnetic field generated by the current flowing in the current line is generated concentrically around the current line and becomes smaller as the distance from the current line becomes longer. The magnetic field generated by an ideal surface current through which current flows at the same current density does not depend on the distance from the flat plate surface.

  The material forming the signal current line 1 can be any material having conductivity, but may be a metal material such as copper (Cu) or aluminum (Al) or an alloy thereof.

  The insulating substrate 2 electrically insulates between the signal current line 1 and the magnetic field detection device 10. The insulating substrate 2 is configured as a plate-like member having a thickness T. The length of the insulating substrate 2 in the X direction is longer than, for example, the length L of the signal current line 1 and the length of the magnetic field detection device 10 in the X direction, and the length of the insulating substrate 2 in the Y direction is the length of the magnetic field detection device 10. Longer than the length. The length of the insulating substrate 2 in the X direction may be shorter than the length L of the signal current line 1. For example, even if the magnetically coupled isolator 100 is configured by bonding the insulating substrate 2 having a length in the X direction shorter than the length L on the signal current line 1 having a length L in the X direction, Good.

  A wiring pattern that is electrically connected to the magnetic field detection device 10 is formed on the surface of the insulating substrate 2, and the wiring pattern is connected to the power source 5 and the like.

  A bias magnetic field current line 6 is provided inside the insulating substrate 2. The bias magnetic current line 6 is electrically insulated from the signal current line 1 provided on the back surface of the insulating substrate 2 by being provided inside the insulating substrate 2. In the region where the magnetic field detection device 10 is formed, the bias magnetic field current line 6 has a magnetic field generated by the current flowing through the signal current line 1 in the direction of the magnetic field generated by the current flowing through the bias magnetic field current line 6. It is provided so as to be orthogonal to the direction. For example, the bias magnetic field current line 6 is provided so as to extend in the X direction. The bias magnetic field current line 6 may have an arbitrary shape and size, but the length of the long side in the cross section of the bias magnetic field current line 6 is preferably longer than the thickness T of the insulating substrate 2. .

  The signal current line 1 may be installed inside the insulating substrate 2, and the bias magnetic field current line 6 may be installed on the back surface of the insulating substrate 2. Further, the signal current line 1 and the bias magnetic field current line 6 are not limited to the structure formed so as to sandwich the insulating substrate 2 as long as they are electrically insulated from each other, and are, for example, covered with an insulating material. May be.

The material constituting the insulating substrate 2 may be any material having electrical insulation, and may be, for example, glass, silicon dioxide (SiO ₂ ), ceramic, resin, or the like, and is composed of other materials. The above material may be deposited on the substrate.

  FIG. 2 is a top view of the magnetic field detection device 10 formed on the surface of the insulating substrate 2. The arrow drawn on the magnetoresistive effect element 3 in FIG. 2 represents the direction of magnetization of the fixed layer 54 of the magnetoresistive effect element 3a. Referring to FIG. 2, magnetic field detection device 10 includes a plurality of magnetoresistive elements 3a. The plurality of magnetoresistive elements 3a are connected in series to form a serial connection element 31A. The magnetoresistive effect element 3a is a tunnel magnetoresistive effect element (TMR element). The serial connection element 31 </ b> A has one end electrically connected to the ground pad 23 formed on the surface of the insulating substrate 2, and the other end formed on the surface of the insulating substrate 2. The power supply pad 24 is electrically connected. The serial connection element 31A and the pads 23 and 24 are electrically connected by, for example, metal wiring. The ground pad 23 is grounded. The power pad 24 is electrically connected to a voltage source or a current source via the resistor 7.

  FIG. 3 shows a cross-sectional view of the magnetoresistive effect element 3a. Referring to FIG. 3, a magnetoresistive effect element 3a as a TMR element includes a substrate 51, a lower electrode layer 52, an antiferromagnetic layer 53, a fixed layer 54 as a first ferromagnetic layer, and a nonmagnetic layer. 55, a free layer 56 as a second ferromagnetic layer, and an upper electrode layer 57 are sequentially stacked.

  The material constituting the substrate 51 may be, for example, silicon (Si), silicon carbide (SiC), gallium nitride (GaN), gallium arsenide (GaAs), glass, or the like.

  The material constituting the lower electrode layer 52 and the upper electrode layer 57 may be any conductive material. For example, tantalum (Ta), tungsten (W), titanium (Ti), ruthenium (Ru), cobalt (Co ), Si, molybdenum (Mo), platinum (Pt), gold (Au), or the like.

  Lower electrode layer 52 and upper electrode layer 57 are connected to metal wiring. The material constituting the metal wiring can be any material having electrical conductivity, and for example, Cu or Al is used.

  The material constituting the antiferromagnetic layer 53 may be any material having antiferromagnetism. For example, an iridium-manganese alloy (IrMn), a platinum-manganese alloy (PtMn), an iron-manganese alloy (FeMn), Nickel-manganese (NiMn) or the like may be used. Further, the antiferromagnetic layer 53 is configured as a SAF (Synthetic Anti-Ferromagnetic) structure in which two ferromagnetic layers stacked with a thin nonmagnetic layer such as Ru or Cu sandwiching each other are antiferromagnetically coupled to each other. It may be.

  The material constituting the fixed layer 54 and the free layer 56 may be any material having ferromagnetism, for example, a metal containing any one of Fe, Co, and Ni, or any alloy thereof. Alternatively, a nickel-iron alloy (NiFe) or a cobalt-iron alloy (CoFe) may be used. Moreover, the fixed layer 54 and the free layer 56 may be configured as a laminated body in which thin films made of these materials are laminated.

The material constituting the nonmagnetic layer 55 may be any material having electrical insulation properties. For example, alumina (Al ₂ O ₃ ), manganese oxide (MgO), hafnium oxide (HfO ₂ ), tantalum oxide ( An oxide film such as Ta ₂ O ₅ ) or spinel (MgAl ₂ O ₄ ) may be used, and nitride or fluoride may be used.

  The antiferromagnetic layer 53 and the fixed layer 54 are exchange coupled. Therefore, the magnetization direction R (see FIG. 2) of the fixed layer 54 is fixed, and the magnetization direction R does not change even when a magnetic field generated by the signal current line 1 or the like is received. The nonmagnetic layer 55 is configured as a tunnel insulating film.

  The planar shape (XY plane) of the plurality of magnetoresistive effect elements 3a has a rectangular shape having a major axis and a minor axis. The plurality of magnetoresistive elements 3a are arranged along a direction (X direction) in which each minor axis direction is perpendicular to the direction (Y direction) in which the signal current line 1 extends. The magnetization direction R of each fixed layer 54 of the plurality of magnetoresistive effect elements 3a is fixed so as to be perpendicular to the direction in which the signal current line 1 extends (Y direction) and along the minor axis direction of the magnetoresistive effect element 3a. And fixed in parallel with the direction of the magnetic field (+ X direction) generated by the current flowing through the signal current line 1. In this specification, for each of the X direction, the Y direction, and the Z direction, The direction of the arrow shown on the coordinate axes in the drawing is described as a positive (+) direction, and the reverse direction of the positive direction is described as a negative (−) direction. In this specification, parallel means that two vectors are in the same direction and parallel, and anti-parallel means that the two vectors are in opposite directions and are parallel. In addition, the parallel and antiparallel in this specification intend the thing of including the error on manufacture of an apparatus, clearance, etc. naturally.

  The plurality of magnetoresistive effect elements 3a are electrically connected in series and connected in a straight line in the Y direction to form a series connection element 31A. The serial connection element 31A is preferably disposed on the surface of the insulating substrate 2 on the region overlapping the signal current line 1 and at the center of the region in the X direction. FIG. 4 shows a cross-sectional view of the serial connection element 31A. The serial connection elements 31 </ b> A are electrically connected in series when adjacent magnetoresistive elements 3 a share the lower electrode layer 52 or the upper electrode layer 57. The number of magnetoresistive effect elements 3a constituting the serial connection element 31A is four in the example shown in FIGS. 2 and 4, but the number is not limited to this, and any number may be used. In the example of the serial connection element 31A shown in FIG. 4, the electrical connection between the serial connection element 31A and the ground pad 23 or the power supply pad 24 is performed through the upper electrode layer 57 and, for example, a metal wiring. That's fine.

  Next, a method for manufacturing the magnetoresistive effect element 3a according to Embodiment 1 will be described. First, the substrate 51 is prepared. An electronic circuit may be formed on the substrate 51 in advance by a transistor, a diode, a wiring, or the like.

  Next, the lower electrode layer 52, the antiferromagnetic layer 53, the fixed layer 54, the nonmagnetic layer 55, the free layer 56, and the upper electrode layer 57 are formed on the substrate 51. The method for forming each layer may be any method, for example, various sputtering methods such as DC magnetron sputtering, molecular beam epitaxy (MBE) method, chemical vapor deposition (CVD) method, vapor deposition. Law, plating method, etc. can be adopted. At this time, the fixed layer 54 is magnetized in a direction parallel to the direction of the magnetic field applied during the process by being subjected to a heat treatment at a predetermined temperature in a state where the magnetic field is applied after being formed. The The magnetization direction R of the fixed layer 54 is along the minor axis direction of the magnetoresistive effect element 3a and is the + X direction. The heat treatment temperature may be a temperature at which exchange coupling between the antiferromagnetic layer 53 and the fixed layer 54 is substantially eliminated. In this way, the laminated structure of the magnetoresistive effect element 3a shown in FIG. 3 is formed.

  Next, referring to FIG. 4, the laminated structure thus obtained is processed into a predetermined pattern, thereby forming magnetoresistive effect element 3 and series connection element 31A in which this is connected in series. Is done. For example, a resist mask having a predetermined pattern shape is formed using a photoresist, and thereafter, a series connection element 31A having the predetermined shape is obtained by ion milling or reactive ion etching (RIE) using the resist mask. . For example, first, each layer from the upper electrode layer 57 to the antiferromagnetic layer 53 is etched in the laminated structure. Next, each layer from the upper electrode layer 57 to the substrate 51 is etched in a part of the stacked structure sandwiched between the etching regions. Next, a metal wiring layer 58 that electrically connects the upper electrode layers 57 facing each other across the region where the layers from the upper electrode layer 57 to the substrate 51 are etched is formed. Any method can be adopted as a method of forming the metal wiring layer 58. In this way, the two magnetoresistive elements 3a electrically connected in series via the lower electrode layer 52 are electrically connected in series via the metal wiring layer 58, whereby FIG. A serial connection element 31A is formed by connecting four magnetoresistive effect elements 3a shown in FIG. 4 in series.

  At this time, the planar shape (shape in the XY plane) of each magnetoresistive element 3a is a rectangle having a major axis and a minor axis as described above. As a result, the magnetization direction of the free layer 56 is the major axis direction of the magnetoresistive element 3a. In this way, the magnetoresistive effect element 3a and the serial connection element 31A according to the first embodiment can be obtained.

  Further, an insulating substrate 2 is prepared. A ground pad 23 and a power supply pad 24 are formed on the surface of the insulating substrate 2. A signal current line 1 is formed on the back surface of the insulating substrate 2. The serial connection element 31 </ b> A is fixed on the surface of the insulating substrate 2. Furthermore, the serial connection element 31A, the ground pad 23, and the power supply pad 24 are electrically connected to each other by metal wiring or the like. In this way, the magnetically coupled isolator 100 according to the first embodiment can be obtained.

  Note that the serial connection element 31A is not limited to one formed in a straight line in the Y direction as shown in FIG. 4 as long as the plurality of magnetoresistance effect elements 3a are electrically connected in series. Referring to FIG. 5, for example, a plurality of magnetoresistive elements 3a are connected in series in the Y direction, and in the X direction by the lower electrode layer 52 or the upper electrode layer 57 formed to extend in the X direction. A series connection element 31 </ b> B in which a plurality of magnetoresistive effect elements 3 a provided so as to be arranged is electrically connected may be used. Also in this case, the magnetization direction of the fixed layer 54 of each magnetoresistive effect element 3a only needs to be formed in the + X direction.

  Next, the operation of the magnetically coupled isolator 100 according to the first embodiment will be described. In the magnetically coupled isolator 100, when a signal current flows through the signal current line 1, a magnetic field proportional to the current value is applied to the magnetoresistive effect element 3a constituting the magnetic field detection device 10, and according to the strength of the magnetic field. As a result, the magnetization direction of the free layer 56 changes. As a result, in the magnetoresistive effect element 3a constituting the series connection element 31A, the magnitude of the current passing through the nonmagnetic layer 55 changes according to the relative relationship of magnetization between the fixed layer 54 and the free layer 56, and the TMR element As a result, the electrical resistance in the stacking direction (Z direction) of the magnetoresistive effect element 3a changes. Thereby, the electrical resistance value of the magnetoresistive effect element 3a changes linearly with respect to the magnetic field. By measuring the resistance change of the magnetoresistive effect element 3a as a voltage value between the power supply pads 24 and 23, a voltage value that changes linearly with respect to the current value flowing through the signal current line 1 can be obtained.

  FIG. 6 is a graph showing a change in resistance value of the magnetic field detection device 10 when a signal current is input to the magnetic field detection device 10. In FIG. 6, the horizontal axis indicates the current value applied to the magnetic field detection device 10, and the vertical axis indicates the change in the resistance value of the magnetic field detection device 10. When a magnetic field parallel to the magnetization direction of the fixed layer 54 is applied to the magnetic field detection device 10 due to the current flowing in the signal current line 1 in the + Y direction, the resistance of the series connection element 31A increases linearly. It becomes constant at. On the other hand, when the current amount of the signal current line 1 is decreased and the current is further passed in the −Y direction, the resistance becomes constant with a linearly decreasing magnetic field. The magnetic field detection device 10 can output the change in resistance as a voltage signal between the power supply pad 24 and the ground pad 23. At this time, in the magnetically coupled isolator 100, the voltage value between the power supply pads 24 and 23 can change linearly with respect to the current value of the signal current line 1, so that the temperature and current values change linearly, for example. Even when analog information is to be transmitted / received, analog information can be directly transmitted without performing AD (Analog-to-Digital) conversion and DA (Digital-to-Analog) conversion, thereby reducing the circuit cost.

  Here, referring to FIG. 6, the magnetic field-resistance characteristics of the magnetoresistive effect element 3 are different from each other in resistance even when the magnetic field is increased and decreased, and show hysteresis characteristics. In order to suppress the hysteresis, it is effective to apply a magnetic field in addition to the magnetic field that generates the signal current to leave the free layer 56 in a single domain state. For example, by providing a bias magnetic field current line 6 extending in the X direction so as to be orthogonal to the signal current line 1 and passing a current therethrough, the free layer 56 has a magnetization direction (+ Y direction) due to its shape magnetic anisotropy. It can be made into a single domain state by receiving a parallel magnetic field. Thereby, the sensitivity with respect to the signal magnetic field in the linear region of the magnetic field-resistance characteristic of the magnetoresistive effect element 3a can be changed. That is, the sensitivity of the magnetoresistive element 3a to the signal magnetic field can be adjusted by adjusting the magnitude of the current flowing through the bias magnetic field current line 6. Note that a magnetic field (hereinafter referred to as a bias magnetic field) generated when a current flows through the bias magnetic field current line 6 is 90 degrees different from a magnetic field generated by the signal current line 1, and the serial connection element 31 </ b> A has the magnetization of the free layer 56. Does not become noise when detecting changes.

  The method of applying the bias magnetic field to the magnetoresistive effect element 3a is not limited to the method of generating the bias magnetic field current line 6, and may be generated by installing a permanent magnet (not shown). If a permanent magnet is used, power is not consumed to generate the bias magnetic field, and thus power consumption can be reduced. The permanent magnet is installed so that the magnetic field generated by the permanent magnet and the magnetic field generated by the signal current line 1 are orthogonal to each other. The permanent magnet is preferably arranged sufficiently away from the magnetic field detection device 10. In this way, a uniform bias magnetic field can be applied to the magnetic field detection device 10.

  Next, functions and effects of the magnetically coupled isolator 100 according to the first embodiment will be described. The magnetically coupled isolator 100 is provided with a signal current line 1 extending linearly in the Y direction, which generates a signal magnetic field. Conventional coupled isolators use a planar coil to generate a signal magnetic field. In this case, a signal current can be generated in a + Y direction region and a -Y direction region. The strength of the magnetic field is affected by the magnetic field generated in each region according to the positional relationship between the magnetic field detection device and the planar coil. As a result, in order to increase the conversion accuracy of the magnetically coupled isolator, it is necessary to increase the size of the planar coil in order to increase the distance between the two regions, and there is a problem that the coupled isolator is increased in size. . Further, if it is attempted to reduce the size of the coupled isolator, there is a problem that the conversion accuracy is lowered due to the influence of the magnetic fields generated by the two regions. In addition, when the installation position of the magnetic field detection device is deviated from the design center, the influence of the magnetic field in the reverse direction received by the magnetic field detection device also changes, which causes a problem that the position robustness is lowered.

  On the other hand, since the signal current line 1 according to the first embodiment is provided so as to extend linearly, the current flowing through the signal current line 1 flows in either the + Y direction or the −Y direction. Thereby, since the magnetic field of a reverse direction does not arise simultaneously, conversion accuracy is high and it can reduce in size. Further, the position robustness can be improved as compared with the case where a planar coil is used.

  In addition, the magnetoresistive effect element 3a is designed to be a rectangle having a major axis and a minor axis, so that the magnetization of the free layer in a magnetic-free state is designed in the major axis direction. Fixed in the minor axis direction by heat treatment. When a magnetic field is applied in the magnetization direction of the fixed layer, the resistance of the magnetoresistive element changes linearly with respect to the magnetic field. Using this characteristic, if a signal current is passed, a generated magnetic field is applied to the magnetoresistive effect element, and the change in resistance of the magnetoresistive effect element is measured as a voltage value, the signal current is linearly expressed. A changing voltage value is obtained. That is, according to the magnetically coupled isolator 100 according to the first embodiment, analog signals and digital signals can be transmitted and received without using an AD conversion circuit, a DA conversion circuit, or the like.

(Embodiment 2)
Next, the magnetically coupled isolator 100 according to the second embodiment will be described with reference to FIGS. The magnetically coupled isolator 100 according to the second embodiment basically has the same configuration as that of the magnetically coupled isolator 100 according to the first embodiment, but includes a magnetic flux collecting core 41 and a magnetic shield 43 as magnetic cores. Furthermore, it differs in that it is equipped.

  The magnetic flux collecting core 41 surrounds the periphery of the signal current line 1 and the insulating substrate 2 along the direction of the magnetic field generated by the signal current flowing through the signal current line 1 (Y direction), and sandwiches the magnetic field detection device 10 therebetween. The opening portion 42 is provided. That is, the magnetoresistive effect element 3 provided in the magnetic field detection device 10 is disposed between the opening portions 42 of the magnetic flux collecting core 41.

  The distance between the opening portions 42 can be set to an arbitrary distance, but is preferably shorter from the viewpoint of strengthening the magnetic field between the opening portions 42. In order to strengthen the magnetic field between the opening portions 42, the length (magnetic path length) of the central portion of the cross section (YZ plane) of the magnetic collecting core 41 is shortened, and the cross sectional area of the magnetic collecting core 41 is increased. It is preferable.

  7 and 8, only the magnetic field detection device 10 is sandwiched between the opening portions 42, but may be sandwiched between the insulating substrate 2 and the like.

  The magnetic shield 43 is provided so as to surround, for example, the signal current line 1, the insulating substrate 2, the magnetic field detection device 10, and the magnetic flux collecting core 41. An opening may be formed in the magnetic shield 43, and the opening is preferably in the direction of the magnetic field (Z direction) that the magnetic field detection device 10 does not substantially detect. In the example shown in FIGS. 7 and 8, the upper end and the lower end in the Z direction of the magnetic shield 43 are open. The opening of the magnetic shield 43 is preferably provided wider than the opening portion 42 of the magnetic flux collecting core 41. A magnetic field generated by a current flowing through the signal current line 1 preferentially passes through a path having a high magnetic permeability, and therefore passes through the magnetic core 41 having a shorter interval between the opening portions 42 than the widely opened magnetic shield 43. Become. The magnetic shield 43 may have a square annular structure or a cylindrical shape.

  Any material may be used for the magnetic core 41 and the magnetic shield 43 as long as the magnetic permeability is sufficiently larger than 1, such as iron, electromagnetic steel plate, ferrite, and amorphous metal. In order to suppress this, it is desirable to use a material with high magnetic permeability.

  In this way, for example, when a current flows through the signal current line 1 in the + Y direction, a magnetic field is generated in the opening portion 42 in the + X direction. Specifically, an annular magnetic field generated around the signal current line 1 passes through the magnetic core 41 made of a magnetic material having a high magnetic permeability, passes through the opening 42, and passes through the magnetic core 41 again. Go around. At this time, since the magnetic flux preferentially passes through a path having a high magnetic permeability, the magnetic field in the opening portion 42 can be strengthened as compared with the case where the magnetic flux collecting core 41 is not provided. Therefore, for example, even if the distance between the signal current line 1 and the magnetic field detection device 10 is increased, a large magnetic field can be applied to the magnetic field detection device 10, and a magnetic field having a magnitude that can be detected by the magnetic field detection device 10. Can be obtained. Further, even when the signal current flowing through the signal current line 1 is very small, a magnetic field having a magnitude that can be detected by the magnetic field detection device 10 can be obtained. As a result, the magnetic field detection accuracy of the magnetic field detection device 10 can be further increased.

  Further, for example, in addition to the magnetic field generated by the current flowing through the signal current line 1, the disturbance magnetic field is an arbitrary magnetic field in the magnetic sensing direction of the magnetic field detection device 10 (in the plane (XY plane) where each layer of the magnetoresistive effect element 3 a extends). Even when applied in the X direction or the Y direction, which is the direction, for example, the magnetization direction of the fixed layer 54 or the magnetization direction of the free layer 56, the magnetic field passes through a material having a high magnetic permeability, so The light is again radiated into the air through the magnetic shield 43 configured as described above. Therefore, it is possible to reduce the influence of the magnetic field that becomes a disturbance on the magnetic field detection device 10 arranged inside the magnetic shield 43.

  At this time, as long as the signal current line 1 is provided so that a current flows in a specific direction, the signal current line 1 may not be provided in a straight line but may be provided in a curved line. However, the signal current line 1 is not a planar coil as described above. For example, in the case where the signal current line 1 is provided as a planar coil having a portion in which the current flows in the + Y direction and a portion in which the current flows in the −Y direction, a collection provided so as to surround the signal current line 1. It is difficult for the magnetic core 41 to increase the strength of the signal magnetic field generated by the planar coil. For example, when the opening portion 42 of the magnetic flux collecting core 41 is positioned between the portion where the current flows in the + Y direction and the portion where the current flows in the −Y direction in the planar coil, the signal magnetic field in the opposite direction is simultaneously generated in the opening portion 42 Therefore, both signal magnetic fields are canceled out, and the strength cannot be increased. On the other hand, in the magnetically coupled isolator 100 according to the second embodiment, the signal current line 1 is not a planar coil but provided so that current flows in one direction (Y direction). By using it, the above effects can be obtained.

  The opening of the magnetic shield 43 may be disposed at a location that is larger than the area of the opening 42 of the magnetic flux collecting core 41 and away from the magnetoresistive element 3. Thus, the magnetic field generated by the current flowing through the signal current line 1 can be collected by the magnetic flux collecting core 41 rather than the magnetic shield 43 and applied to the magnetic field detection device 10.

  If the influence of the disturbance magnetic field on the magnetic field detection device 10 is small, only the magnetic collecting core 41 may be used, or the magnetic field generated by the current flowing through the signal current line 1 can be sufficiently detected. For example, only the magnetic shield 43 may be used. Similarly to the magnetically coupled isolator 100 according to the first embodiment, a bias magnetic field current line 6 (see FIG. 1) or a permanent magnet capable of applying a bias magnetic field orthogonal to the magnetic field generated by the signal current line 1 is used. It may be provided. In this case, the bias magnetic field current line 6 and the permanent magnet may be provided in the magnetic shield 43.

  With reference to FIG. 8B, the magnetic flux collecting core 41 may be provided as a so-called cut core so as to be divided into a plurality of parts. In this manner, for example, after the magnetically coupled isolator 100 according to the first embodiment is prepared, the magnetically coupled core 41 according to the second embodiment is combined with the magnetic flux collecting core 41 as a cut core so as to surround the isolator 100. The isolator 100 can be easily configured.

(Embodiment 3)
Next, the magnetically coupled isolator 100 according to the third embodiment will be described with reference to FIG. The magnetically coupled isolator 100 according to the third embodiment basically has the same configuration as that of the magnetically coupled isolator 100 according to the first embodiment, except that the magnetic field detection device 12 includes a plurality of series connection elements 32A, 32B, It is different in that it is configured as a bridge circuit composed of 32C and 32D.

  Arrows R1 and R2 drawn on the series connection elements 32A to 32D in FIG. 9 indicate the magnetization directions of the fixed layer 54 (see FIG. 3) of the magnetoresistive effect element 3 constituting each of the series connection elements. . The serial connection element 31A or the serial connection element 31B described in the first embodiment can be used as the serial connection elements 32A to 32D.

  The serial connection elements 32 </ b> A to 32 </ b> D are formed in a region overlapping the signal current line 1 when the signal current line 1 is viewed in plan. Further, the serial connection elements 32A to 32D have the major axis direction of the magnetoresistive effect element 3 constituting the serial connection elements 32A to 32D and the direction of the current flowing in the signal current line 1 (+ Y direction or -Y direction). It is formed as follows. That is, the magnetization direction of the free layer 56 of each magnetoresistance effect element 3 is provided to be the + Y direction or the −Y direction.

  On the other hand, the magnetization direction of the fixed layer 54 of the serial connection elements 32A to 32D is arranged to be parallel or antiparallel to the direction of the magnetic field generated when a current flows through the signal current line 1. Specifically, in the serial connection elements 32A and 32B, the magnetization direction R1 of the fixed layer 54 is fixed in the −X direction, and each is formed as one resistor. The serial connection element 32C and the serial connection element 32D can be formed as one resistor because the magnetization direction R2 of the fixed layer 54 is fixed in the + X direction. As long as the magnetization direction R1 of the fixed layer 54 of the series connection elements 32A and 32B and the magnetization direction R2 of the fixed layer 54 of the series connection elements 32C and 2D are different from each other by 180 °, the fixed values of the series connection elements 32A and 32B are fixed. The magnetization direction R1 of the layer 54 may be the + X direction, and the magnetization direction R2 of the fixed layer 54 of the series connection elements 32C and 32D may be the -X direction.

  A half-bridge circuit 27A is configured by connecting a series connection element 32A having a fixed layer 54 having a magnetization direction R1 and a series connection element 32C having a fixed layer 54 having a magnetization direction R2 in series. Specifically, the power supply pad 24b, the series connection elements 32A and 32C, and the ground pad 23a are electrically connected in series in order to form the half bridge circuit 27A. An output pad 21 is formed between the series connection element 32A and the series connection element 32C.

  Similarly, a half-bridge circuit 27B is configured by connecting a series connection element 32B having a fixed layer 54 having a magnetization direction R1 and a series connection element 32D having a fixed layer 54 having a magnetization direction R2 in series. . Specifically, the power supply pad 24a, the series connection element 32D having the fixed layer 54 with the magnetization direction R2, the series connection element 32B having the fixed layer 54 with the magnetization direction R1, and the ground pad 23b are sequentially electrically connected in series. Thus, a half bridge circuit 27B is formed. An output pad 22 is formed between the series connection element 32D and the series connection element 32B. The power pads 24a and 24b are connected to a voltage source or a current source, and the ground pads 23a and 23b are both grounded.

  Next, the operation of the magnetic field detection device 12 according to the third embodiment will be described. When a current in the + Y direction flows through the signal current line 1 from a state in which the signal magnetic field from the signal current line 1 is not applied, a magnetic field in the + X direction is applied to the half bridge circuit 27A. While the resistance increases, the resistance of the serial connection element 32C decreases. Therefore, the voltage between the output pad 21 and the ground pad 23a decreases. On the other hand, in the half-bridge circuit 27B, the resistance of the series connection element 32B increases while the resistance of the series connection element 32D decreases. As a result, the voltage between the output pad 22 and the ground pad 23b increases. On the other hand, when a current in the -Y direction flows through the signal current line 1 and a magnetic field in the -X direction is applied to the half bridge circuit 27A, the voltage between the output pad 21 and the ground pad 23a increases. The voltage between the output pad 22 and the ground pad 23b decreases.

  That is, the voltage between the output pad 21 and the ground pad 23a and the voltage between the output pad 22 and the ground pad 23b fluctuate in response to each other in accordance with the signal magnetic field generated by the signal current line 1. Therefore, by detecting the difference between these voltages, it is possible to reduce the influence of noise equally applied to the series connection elements 32A to 32D, and to increase the magnetic field detection accuracy.

  As with the magnetically coupled isolator 100 according to the first embodiment, a bias magnetic field capable of applying a bias magnetic field orthogonal to the magnetic field generated by the signal current line 1 in order to suppress the hysteresis of the series connection elements 32A to 32D. Current lines 6 (see FIG. 1) and permanent magnets may be provided.

(Embodiment 4)
Next, a magnetically coupled isolator 100 according to the fourth embodiment will be described with reference to FIG. The magnetically coupled isolator 100 according to the fourth embodiment basically has the same configuration as that of the magnetically coupled isolator 100 according to the first embodiment, but the magnetization direction R (see FIG. 10) of the fixed layer 54 is magnetic. The difference is that the resistive element 3 is fixed in the major axis direction (+ X direction). In other words, the major axis direction of the magnetoresistive effect element 3 is different in that it is arranged so as to be in the same direction as the magnetic field generated by the current flowing through the signal current line 1.

  The plurality of magnetoresistive elements 3c in the fourth embodiment are arranged so that the major axis direction is the same direction as the magnetic field generated by the current flowing through the signal current line 1, and are electrically connected in series with each other. Thus, the serial connection element 31C is configured. The serial connection element 31C is preferably disposed on a region overlapping the signal current line 1 on the surface of the insulating substrate 2 and on a region overlapping the central portion of the signal current line 1 in the X direction.

  In the magnetoresistive effect element 3c, the magnetization direction R of the fixed layer 54 is fixed in the + X direction by induced magnetic anisotropy by heat treatment in a magnetic field. In addition, the magnetization direction of the free layer 56 faces the long axis direction (+ X direction or -X direction) in the absence of a magnetic field due to shape magnetic anisotropy.

  FIG. 11 shows a change in resistance of the magnetic field detection device 10 with respect to the current value of the signal current line 1. When a magnetic field is applied in parallel to the magnetization direction R of the fixed layer 54 by causing a current in the + Y direction to flow through the signal current line 1, the resistance of the serial connection element 31 </ b> C rapidly changes with a predetermined current value as a boundary. After that, it becomes a constant value. When the current value in the + Y direction flowing through the signal current line 1 is decreased and the current is further flowed in the −Y direction, the resistance of the series connection element 31C rapidly changes with a predetermined current value as a boundary and thereafter becomes constant.

  As described above, in the magnetically coupled isolator according to the fourth embodiment, the electric resistance value of the series connection element 31C changes as a binary variable with respect to the current flowing through the signal current line 1. This is suitable when it is desired to determine whether the information is equal to or greater than a threshold value. In such a case, by designing the threshold value of the TMR element using the magnetic field detection device 12 according to the fourth embodiment, whether or not the analog information directly exceeds the threshold value without using a comparator. And the determination result can be transmitted as (0) and (1) signals. As a result, the magnetically coupled isolator 100 according to the fourth embodiment does not need to include a comparator, so that manufacturing costs can be reduced and power consumption can be suppressed. Furthermore, the magnetically coupled isolator 100 can be reduced in size.

  Although four magnetoresistive elements 3c constituting the serial connection element 31C are illustrated in the figure, any number may be used. The method of connecting the serial connection elements 31C in series can be the same as that of the magnetic field detection apparatus 10 according to the first embodiment.

(Embodiment 5)
Next, the magnetically coupled isolator 100 according to the fifth embodiment will be described with reference to FIG. The magnetically coupled isolator 100 according to the fifth embodiment basically has the same configuration as that of the magnetically coupled isolator 100 according to the third embodiment, but includes a plurality of series connection elements 33A to 33D that constitute a bridge circuit. The difference is that a series connection element 31C according to the fourth embodiment is configured instead of the series connection element 31A according to the first embodiment.

  An arrow R drawn on the series connection elements 33A to 33D in FIG. 12 represents the direction of magnetization of the fixed layer 54 of the magnetoresistive effect element 3c constituting each series connection element. In the magnetic field detection device 14 according to the fourth embodiment, the series connection element 33A having the fixed layer 54 with the magnetization direction R1 and the series connection element 33C having the fixed layer 54 with the magnetization direction R2 are connected in series. A half-bridge circuit 28A is configured. Specifically, the power supply pad 24b, the serial connection elements 33A and 33C, and the ground pad 23a are electrically connected in series in order to form the half bridge circuit 28A. An output pad 21 is formed between the series connection element 33A and the series connection element 33C.

  Similarly, a half-bridge circuit 28B is configured by connecting a serial connection element 33B having a fixed layer 54 with a magnetization direction R1 and a serial connection element 33D having a fixed layer 54 with a magnetization direction R2 in series. . Specifically, the power supply pad 24a, the series connection element 33D having the fixed layer 54 in the magnetization direction R2, the series connection element 33B having the fixed layer 54 in the magnetization direction R1, and the ground pad 23b are sequentially electrically connected in series. Thus, the half bridge circuit 28B is formed. An output pad 22 is formed between the series connection element 33D and the series connection element 33B.

  Next, the operation of the magnetic field detection apparatus 14 according to the fifth embodiment will be described. When a magnetic field in the + Y direction is applied to the half-bridge circuit 28A due to a current flowing in the + Y direction from the state where the signal magnetic field by the signal current line 1 is not applied, the series connection element 33A The resistance increases rapidly when the current exceeds a predetermined current value. On the other hand, the resistance of the serial connection element 33C rapidly decreases when the resistance becomes a predetermined current value or less. For this reason, the voltage between the output pad 21 and the ground pad 23a rapidly decreases with a predetermined current value as a boundary. On the other hand, in the half-bridge circuit 28B, the resistance of the series connection element 33B increases rapidly with a predetermined current value as a boundary, whereas the resistance of the series connection element 33D decreases rapidly with a predetermined current value as a boundary. For this reason, the voltage between the output pad 22 and the ground pad 23b rapidly increases with a predetermined current value as a boundary. In contrast, when a current in the −Y direction flows through the signal current line 1 and a magnetic field in the −X direction is applied to the half-bridge circuit 28A, the voltage between the output pad 21 and the ground pad 23a becomes a predetermined current. The voltage increases abruptly with the value as a boundary, and the voltage between the output pad 22 and the ground pad 23b rapidly decreases with a predetermined current value as the boundary.

  In this way, the magnetic field detection device 14 according to the fifth embodiment can achieve the same effects as the magnetic field detection device 12 according to the third embodiment, and the magnetic field detection device 13 according to the fourth embodiment. Similar effects can be achieved.

(Embodiment 6)
Next, the magnetically coupled isolator 101 according to the sixth embodiment will be described with reference to FIGS. The magnetically coupled isolator 101 according to the sixth embodiment basically has the same configuration as that of the magnetically coupled isolator 100 according to the first embodiment, but a signal current line provided on the back surface of the insulating substrate 2. 1 is different in that a solenoid coil 8 having an insulating substrate 2 and a magnetic field detection device 10 disposed therein is formed.

  The magnetic field generated by the current flowing through the solenoid coil 8 increases in proportion to the number of turns. The solenoid coil 8 can generate a stronger magnetic field when the same current value is passed as compared to a linear current line. In other words, by using the solenoid coil 8 to generate the signal magnetic field, it is possible to generate a signal magnetic field that can be detected by the magnetic field detection device 10 even if the current value changes more minutely.

  In addition, a magnetic field having a uniform direction and size is generated inside the winding of the solenoid coil 8 regardless of the position. For this reason, even if the installation position of the magnetic field detection apparatus 10 deviates from the design center, a desired magnetic field is applied, so that the position robustness can be improved.

  14 and 15, in order to reduce the influence from the disturbance magnetic field, the entire solenoid coil 8 including the magnetic field detection device 10 and the like may be surrounded by a magnetic shield 43. The magnetic shield 43 may be the same as the magnetic shield 43 according to the second embodiment. In this way, the same effect as that of the magnetically coupled isolator 100 according to the second embodiment can be obtained.

  Further, similarly to the magnetically coupled isolator 100 according to the first embodiment, a bias magnetic field current line 6 (see FIG. 1) and a permanent magnet may be provided. The bias magnetic field current line 6 and the permanent magnet may be provided inside the solenoid coil 8 or may be provided outside.

  In the magnetically coupled isolator 100 according to the first to sixth embodiments, the magnetoresistive effect elements 3a and 3c are not limited to a rectangular shape as long as they have a major axis and a minor axis, and may be elliptical.

  The magnetically coupled isolators 100 according to the first to sixth embodiments can be applied in combination as appropriate. For example, the magnetic core 41 and the magnetic shield 43 according to the second embodiment may be applied to the magnetically coupled isolator 100 according to the third to fifth embodiments.

  Although the embodiment of the present invention has been described above, the above-described embodiment can be variously modified. The scope of the present invention is not limited to the above-described embodiment. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention is particularly advantageously applied to a magnetically coupled isolator that can transmit and receive an analog signal and a digital signal without using an AD conversion circuit or the like.

  DESCRIPTION OF SYMBOLS 1 Signal current line, 2 Insulation board, 3, 3a, 3c Magnetoresistive element, 6 Bias magnetic field current line, 7 Resistance, 8 Solenoid coil 10, 12, 13, 14 Magnetic field detection apparatus 21, 22 Output pad , 23, 23a, 23b Ground pad, 24, 24a, 24b Power pad, 27A, 27B, 28A, 28B Half bridge circuit, 31A, 31B, 31C, 32A, 32B, 32C, 32D, 33A, 33B, 33C, 33D Connection element, 41 Magnetic collecting core, 42 Opening portion, 43 Magnetic shield, 51 Substrate, 52 Lower electrode layer, 53 Antiferromagnetic layer, 54 Fixed layer, 55 Nonmagnetic layer, 56 Free layer, 57 Upper electrode layer, 58 Metal Wiring layer, 100, 101 Magnetic coupling type isolator.

Claims (10)

A signal current line for carrying a current superimposed signal,
A magnetic field detection device for detecting a magnetic field generated by a current flowing through the signal current line;
An insulating substrate that electrically insulates between the signal current line and the magnetic field detector;
The signal current line is configured to be able to apply a magnetic field in one direction to the magnetic field detection device,
The magnetic field detection device includes a magnetoresistive element having a major axis and a minor axis perpendicular to the major axis,
The magnetoresistive effect element has an antiferromagnetic layer, a first ferromagnetic layer, a nonmagnetic layer, and a shape magnetic anisotropy, and a magnetization direction is directed in a direction along the major axis in the absence of a magnetic field. The second ferromagnetic layer is laminated in order,
The magnetization direction of the first ferromagnetic layer is fixed in a direction along the direction of a magnetic field generated by a current flowing through the signal current line,
The magnetic coupling type isolator, wherein the magnetization direction of the second ferromagnetic layer changes according to a magnetic field generated when a current flows through the signal current line.   The magnetically coupled isolator according to claim 1, wherein the signal current line is formed to extend linearly in one direction.   2. The magnetically coupled isolator according to claim 1, wherein the signal current line is formed as a solenoid coil wound so as to surround the magnetic field detection device and the insulating substrate. A plurality of the magnetoresistive effect elements are formed,
The plurality of magnetoresistive elements are connected in series with each other,
4. The short axis direction of the plurality of magnetoresistive effect elements is provided along a direction of a magnetic field generated by a current flowing through the signal current line, respectively. 5. The magnetically coupled isolator described.   5. The magnetically coupled isolator according to claim 4, further comprising a bias magnetic field generation unit that generates a magnetic field along a direction orthogonal to a direction of a magnetic field generated when a current flows through the signal current line. A plurality of the magnetoresistive effect elements are formed,
The plurality of magnetoresistive elements are connected in series with each other,
4. The long axis direction of the plurality of magnetoresistive elements is provided along the direction of a magnetic field generated when a current flows through the signal current line, respectively. 5. The magnetically coupled isolator described. The plurality of magnetoresistive elements form a bridge circuit,
The plurality of magnetoresistive elements connected in series in the bridge circuit are connected such that the magnetization directions of the first ferromagnetic layers are opposite to each other. The magnetically coupled isolator according to claim 1.   The magnetic core further includes an opening that surrounds the signal current line and the insulating substrate along a direction of a magnetic field generated by a current flowing through the signal current line and sandwiches the magnetic field detection device. The magnetically coupled isolator according to any one of claims 1 to 7.   The magnetically coupled isolator according to claim 8, wherein the magnetic core is provided so as to be divided into a plurality of parts.   The magnetically coupled isolator according to claim 1, further comprising a magnetic shield provided so as to surround the signal current line, the insulating substrate, and the magnetic field detection device.

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