Sensor device

Abstract

A sensor device (1) comprises: a magnetic material core part (2) capable of forming a closed magnetic circuit including two outer leg parts; two coil parts (L1 and L2) that are respectively formed by winding wires around the two outer leg parts and each generate a signal magnetic flux according to an alternating-current signal applied; a magnetic flux generation unit that generates a bias magnetic flux so that the bias magnetic flux circulates through the closed magnetic circuit; an alternating-current signal circuit (3) for applying an alternating-current signal to each of the two coil parts so that a signal magnetic flux in the same direction as the bias magnetic flux is generated in each of the outer leg parts; and signal output terminals (V1 and V2) for outputting detection signals that allow for detection of voltage balance between the two coil parts (L1 and L2) that changes according to an external magnetic field acting on the magnetic material core part (2).

Description

Sensor Device

[0001] The present invention relates to a sensor device based on magnetic detection.

[0002] Hall elements that utilize the Hall effect to detect magnetism are known as magnetic sensors. Patent Documents 1 and 2 listed below disclose current sensors in which a Hall element is disposed in a gap in a magnetic core. Patent Document 1 listed below points out the problem of detection errors caused by changes in the characteristics of the magnetic core and the Hall element due to temperature changes, and to solve this problem, a temperature compensation circuit is added to the amplifier circuit for the output signal of the Hall element. Patent Document 2 listed below also discloses that, in order to reduce errors caused by the inaccuracy of the Hall element placement during sensor assembly, the Hall element is used to detect the direction of the current to be detected, but is not used directly to measure the magnitude of the current to be detected.

[0003] JP 63-61961 A JP 2012-37508 A

[0004] As mentioned above, Hall elements can cause detection errors due to temperature changes, sensor placement during assembly, etc. For this reason, when using a Hall element as a magnetic sensor, it is necessary to correct the characteristics of the Hall element itself to ensure detection accuracy, but such characteristic correction is problematic in that it is quite difficult.

[0005] The present invention has been made in view of the above-mentioned problems, and provides a sensor device that is less susceptible to environmental changes and can maintain magnetic detection accuracy.

[0006] One aspect of the present invention is a sensor device comprising: a first magnetic core portion capable of forming a first closed magnetic circuit including two outer legs; two coil portions configured by windings wound around each of the two outer legs, each generating a signal magnetic flux in response to an applied AC signal; a magnetic flux generating portion generating a bias magnetic flux to circulate through the first closed magnetic circuit; an AC signal circuit applying an AC signal to the two coil portions so that the signal magnetic flux in the same direction as the bias magnetic flux is generated in each of the outer legs; and a signal output terminal outputting a detection signal capable of detecting the voltage balance between the two coil portions, which changes in response to an external magnetic field acting on the first magnetic core portion.

[0007] According to the above-described aspect, it is possible to provide a sensor device that is less susceptible to environmental changes and can maintain magnetic detection accuracy.

[0008] 9 is a schematic diagram showing the configuration of a sensor device according to a first embodiment. FIG. 10 is a schematic diagram showing the flow of magnetic flux in a magnetic core portion. FIG. 11 is a schematic diagram showing the configuration of a sensor device according to a second embodiment. FIG. 12 is a schematic diagram showing the configuration of a sensor device according to a third embodiment. FIG. 13 is a graph showing core characteristics (magnetic permeability and magnetic field strength characteristics) of a magnetic core. FIG. 14 is a schematic diagram showing the configuration of a sensor device according to a fourth embodiment. FIG. 15 is a circuit diagram showing a first example of an AC signal circuit and a signal output circuit. FIG. 16 is a diagram showing an example of an output signal when the AC signal circuit and the signal output circuit shown in FIG. 7 are applied. FIG. 17 is a circuit diagram showing a second example of an AC signal circuit and a signal output circuit. FIG. 18 is a diagram showing an example of an output signal when the AC signal circuit and the signal output circuit shown in FIG. 9 are applied. FIG. 19 is a schematic diagram showing the appearance of a current sensor device according to a fifth embodiment. FIG. 19 is a partial schematic diagram showing the arrangement of a magnetic core portion of the sensor device in the current sensor device according to the fifth embodiment. FIG. 19 is a graph showing an example of a voltage signal (detection signal) output from a signal output terminal in the current sensor device according to the fifth embodiment. FIG. 19 is a schematic diagram showing an example of the arrangement of a current sensor device according to a sixth embodiment with respect to a current line. FIG. 19 is a schematic diagram showing the appearance of a sensor device according to a seventh embodiment. FIG. 19 is a schematic diagram showing the flow of signal magnetic flux and bias magnetic flux in a sensor device according to the seventh embodiment. 13 is a schematic diagram showing an external appearance of a sensor device according to a modified example of the seventh embodiment. FIG. 14 is a schematic diagram showing an example of arrangement of a current sensor device according to an eighth embodiment with respect to a current line. FIG. 15 is a graph showing the results of an evaluation test of the current sensor device according to the present example.

[0009] Hereinafter, embodiments of the present invention will be described. Note that the following embodiments are merely examples, and the present invention is not limited to the configurations of the following embodiments.

[0010] 1 is a schematic diagram showing the configuration of a sensor device 1 according to a first embodiment. The sensor device 1 according to the first embodiment includes a magnetic core portion 2, coil portions L1 and L2, an AC signal circuit 3, signal output terminals V1 and V2, etc.

[0011] In the example of FIG. 1 , the magnetic core portion 2 has a core shape known as an EE core, in which E-shaped cores 21 and 22, each having a center leg and two outer legs, are butted together to form a closed magnetic circuit. The E-shaped core 21 has outer legs 21a and 21b and a center leg 21c, while the E-shaped core 22 has outer legs 22a and 22b and a center leg 22c. The center legs 21c and 22c may be cylindrical or prismatic. The magnetic core portion 2 corresponds to a first magnetic core portion. Hereinafter, the continuous outer legs 21a and 22a and the continuous outer legs 21b and 22b may be referred to as core outer legs, respectively, and the continuous center legs 21c and 22c may be referred to as core center legs.

[0012] The shape of the magnetic core portion 2 is not limited to the example shown in FIG. 1 , and may be any shape that forms a closed magnetic circuit including two outer legs. For example, the magnetic core portion 2 may be an EI-type core. The magnetic core portion 2 may also have a core shape that does not have a center leg, such as a UU-type core. The magnetic core portion 2 may be any general magnetic core, such as a ferrite core or a dust core, and its material and molding method are not limited.

[0013] The coil sections L1 and L2 are configured by winding a wire around each outer leg (each core outer leg) of the magnetic core section 2. In the example of Fig. 1, the coil section L1 is configured by winding a wire around the outer legs 21a and 22a of the E-shaped cores 21 and 22, and the coil section L2 is configured by winding a wire around the outer legs 21b and 22b of the E-shaped cores 21 and 22.

[0014] The AC signal circuit 3 is a circuit that applies AC signals to the coils L1 and L2. The AC signal circuit 3 applies AC signals to the coils L1 and L2 so that the magnetic flux generated from the coils L1 and L2 has polarity that circulates in the same direction through the closed magnetic circuit of the magnetic core 2. In the example of Fig. 1, a DC bias current is superimposed on the AC signals applied to the coils L1 and L2.

[0015] In the example of FIG. 1 , the AC signal circuit 3 includes coils L5 and L6 and is connected to an AC signal source VS1. The AC signal circuit 3 is configured such that the coil sections L1 and L2 are each connected in parallel to the AC signal source VS1. The coil L5 is connected in series with the coil section L1, and the coil L6 is connected in series with the coil section L2. The coils L5 and L6 remove noise components from the AC signal applied to the coil sections L1 and L2. In this embodiment, as will be described later, the coils L5 and L6 are connected in series with the coil sections L1 and L2 as reactance elements to output the impedance of the coil sections L1 and L2 as a voltage signal. The AC signal source VS1 supplies an AC signal on which a DC bias current is superimposed.

[0016] The signal output terminals V1 and V2 are connected to the AC signal circuit 3 and are terminals that output detection signals capable of detecting the voltage balance between the coil portions L1 and L2. In the example of Fig. 1, the signal output terminal V1 outputs a voltage signal to be applied to the coil portion L1, and the signal output terminal V2 outputs a voltage signal to be applied to the coil portion L2. The voltage signals output from the signal output terminals V1 and V2 make it possible to detect the voltage difference between the coil portions L1 and L2, and therefore both output signals can be called detection signals capable of detecting the voltage balance between the coil portions L1 and L2.

[0017] 2 is a schematic diagram showing the flow of magnetic flux within the magnetic core 2. Within the magnetic core 2, magnetic flux (hereinafter sometimes referred to as signal magnetic flux) generated by an AC signal applied to the coils L1 and L2 flows in a circulating direction from one outer core leg to the other outer core leg of the magnetic core 2. This signal magnetic flux is indicated by dashed arrows in FIG. 2.

[0018] On the other hand, as shown by the solid arrows in Figure 2, when an external magnetic field acts on the magnetic core 2 in the extension direction of the middle leg of the core, magnetic flux based on the external magnetic field flows within the magnetic core 2. At this time, most of the magnetic flux based on the external magnetic field flows through the middle leg of the core, and a leakage portion flows through the outer leg of the core. As a result, a magnetic flux that is the signal magnetic flux plus the leakage magnetic flux based on the external magnetic field flows in one outer leg of the core (left side of the page in Figure 2), and a magnetic flux that is the signal magnetic flux minus the leakage magnetic flux based on the external magnetic field flows in the other outer leg of the core (right side of the page in Figure 2).

[0019] Therefore, when no external magnetic field is acting on the magnetic core 2, the signal output terminals V1 and V2 output voltage signals of the same phase and level. However, when an external magnetic field, such as that shown in FIG. 2, is acting on the magnetic core 2, a difference occurs between the amount of magnetic flux passing through the coil L1 and the amount of magnetic flux passing through the coil L2, as described above, resulting in a difference in the inductance of the coils L1 and L2. As a result, a difference also occurs in the levels of the voltage signals output from the signal output terminals V1 and V2. Therefore, the strength of the external magnetic field can be indicated by the difference in the levels of the output voltage signals. When an external magnetic field opposite to the direction shown in FIG. 2 acts on the magnetic core 2, the direction of the magnetic flux based on the external magnetic field flowing through the outer core legs is also reversed, resulting in the levels of the voltage signals output from the signal output terminals V1 and V2 being reversed.

[0020] Therefore, according to this embodiment, the strength and direction of the external magnetic field can be detected by using the voltage signals (detection signals) output from the signal output terminals V1 and V2. In this embodiment, the strength and direction of the external magnetic field can be detected by outputting a detection signal that can detect the voltage balance between the coils L1 and L2, which changes depending on the external magnetic field acting on the magnetic core 2. This enables high-precision magnetic detection without being affected by the hysteresis or temperature characteristics of the magnetic core 2.

[0021] Furthermore, detection sensitivity can be increased by using a magnetic core with high magnetic permeability as the magnetic core unit 2. Furthermore, it is also possible to adjust the magnitude of the level difference between the voltage signals (detection signals) output from the signal output terminals V1 and V2 by adjusting the magnitude of the DC bias current superimposed on the AC signals applied to the coil units L1 and L2.

[0022] Furthermore, according to this embodiment, if the magnetic core unit 2 has a core center leg, it can detect a strong external magnetic field even if the coil units L1 and L2 have few windings. This is because the arrangement of the magnetic core unit 2 relative to the external magnetic field allows most of the magnetic flux based on the external magnetic field to flow through the core center leg, and the voltage balance between the coil units L1 and L2 can be detected by the leakage magnetic flux. However, if the external magnetic field is not very strong, the magnetic core unit 2 may have a core shape that does not have a core center leg.

[0023] [Second embodiment] Fig. 3 is a schematic diagram showing the configuration of a sensor device 1 according to a second embodiment. The sensor device 1 according to the second embodiment will be described below with reference to Fig. 3. In the following description, the configuration different from the first embodiment will be mainly described, and the description of the configuration similar to the first embodiment will be omitted as appropriate.

[0024] In the second embodiment, the AC signal circuit 3 does not include coils L5 and L6, and the coils L1 and L2 are connected in series to the AC signal source VS1. In this way, in the second embodiment, the coils L1 and L2 are connected in series and act as reactance elements, so the coils L5 and L6 are not provided. Note that the AC signal source VS1 supplies an AC signal on which a DC bias current is superimposed, similar to the first embodiment.

[0025] In the second embodiment, the signal output terminal V1 is connected between the AC signal source and the coil portion L1, and the signal output terminal V2 is connected between the coil portion L1 and the coil portion L2. That is, the signal output terminal V2 outputs a detection signal at an intermediate signal level between the coil portion L1 and the coil portion L2. Therefore, if the inductances of the coil portion L1 and the coil portion L2 are the same, the voltage signal level output from the signal output terminal V2 is theoretically half the voltage signal level output from the signal output terminal V1. However, if an external magnetic field causes a difference between the amount of magnetic flux passing through the coil portion L1 and the amount of magnetic flux passing through the coil portion L2, resulting in a difference in the inductances of the coil portions L1 and L2, the voltage signal level output from the signal output terminal V2 will no longer be half the voltage level output from the signal output terminal V1. Therefore, both the output signals from the signal output terminals V1 and V2 can be called detection signals capable of detecting the voltage balance between the coil portion L1 and the coil portion L2.

[0026] In this way, the sensor device 1 according to the second embodiment can also achieve the same effects as those of the first embodiment.

[0027] [Third embodiment] Fig. 4 is a schematic diagram showing the configuration of a sensor device 1 according to a third embodiment. The sensor device 1 according to the third embodiment will be described below with reference to Fig. 4. In the following description, the configuration different from the first embodiment will be mainly described, and the description of the configuration similar to the first embodiment will be omitted as appropriate.

[0028] The sensor device 1 according to the third embodiment further includes bias coil units L3 and L4 and a DC signal circuit 5 in addition to the configuration of the first embodiment. The bias coil units L3 and L4 are configured by winding a wire around each outer leg of the magnetic core unit 2, separately from the coil units L1 and L2. In the example of Fig. 4, the coil unit L1 is configured by winding a wire around the outer leg 22a of the E-shaped core 22, the coil unit L2 is configured by winding a wire around the outer leg 22b of the E-shaped core 22, the bias coil unit L3 is configured by winding a wire around the outer leg 21a of the E-shaped core 21, and the bias coil unit L4 is configured by winding a wire around the outer leg 21b of the E-shaped core 21.

[0029] The DC signal circuit 5 is a circuit that applies DC signals to the bias coil portions L3 and L4. The DC signal circuit 5 applies DC signals to the bias coil portions L3 and L4 so that the magnetic flux generated from the bias coil portion L3 and the magnetic flux generated from the bias coil portion L4 have polarities that circulate in the same direction through the closed magnetic circuit of the magnetic core portion 2. The magnetic flux generated in the magnetic core portion 2 by the DC signal flowing through the bias coil portions L3 and L4 is sometimes referred to as bias magnetic flux.

[0030] 4, the DC signal circuit 5 includes a resistance element Rd and is connected to a DC power supply DCV1. The DC signal circuit 5 is configured such that the resistance element Rd and bias coil units L3 and L4 are each connected in series to the DC power supply DCV1.

[0031] In the third embodiment, the AC signal circuit 3 is connected to AC signal sources VS1 and VS2 as shown in FIG. 4 , and is configured such that the AC signal source VS1 applies an AC signal to the coil portion L1 via the coil L5, and the AC signal source VS2 applies an AC signal to the coil portion L2 via the coil L6. The AC signal sources VS1 and VS2 only need to supply AC signals of the same phase and level, and the same effects as those of the configuration in the first embodiment can be obtained. In the third embodiment, because the configuration for passing bias magnetic flux (bias coil portions L3 and L4, DC signal circuit 5) is provided as described above, a DC bias current does not need to be superimposed on the AC signals supplied from the AC signal sources VS1 and VS2.

[0032] In this way, in the third embodiment, by newly providing the bias coils L3 and L4 and the DC signal circuit 5 and passing a bias magnetic flux through the magnetic core 2, it is not necessary to superimpose a DC bias current on the AC signal applied to the coils L1 and L2. Note that, also in the third embodiment, it is possible to adjust the magnitude of the level difference between the voltage signals (detection signals) output from the signal output terminals V1 and V2 by varying the amount of bias magnetic flux by adjusting the resistance value of the resistive element Rd and the output of the DC power supply.

[0033] [Fourth Embodiment] In the first and second embodiments described above, an AC signal with a DC bias current superimposed thereon is applied to the coils L1 and L2, and in the third embodiment, a DC signal is applied to the bias coils L3 and L4, thereby generating a bias magnetic flux in the magnetic core 2. Therefore, in the first and second embodiments, the AC signal circuit 3 can be described as including a magnetic flux generating unit that generates a bias magnetic flux, and in the third embodiment, the bias coils L3 and L4 and the DC signal circuit 5 can be described as the magnetic flux generating unit. Furthermore, in each of the above-described embodiments, the signal magnetic flux and the bias magnetic flux are generated with polarities that circulate in the same direction through the closed magnetic circuit within the magnetic core 2. That is, the signal magnetic flux and the bias magnetic flux are configured to have the same polarity in at least each outer core leg.

[0034] Figure 5 is a graph showing the core characteristics (magnetic permeability and magnetic field strength characteristics) of a magnetic core. The vertical axis represents magnetic permeability, and the horizontal axis represents magnetic field strength. As shown in Figure 5, magnetic cores generally have the characteristic that their permeability decreases as the magnetic field strength generated in the core increases, and the range of permeability from approximately 30% to 70% is the region where permeability linearly decreases with increasing magnetic field strength. Meanwhile, the inductance of a coil using such a magnetic core as its core material is proportional to the magnetic permeability of the magnetic core.

[0035] The sensor device 1 according to each of the above-described embodiments is capable of detecting the strength and direction of an external magnetic field through the difference in inductance between the coils L1 and L2 caused by the action of the external magnetic field. Therefore, in order to improve detection accuracy, it is desirable to perform detection within a region in the core characteristics where the permeability decays linearly. Here, "decaying linearly" does not necessarily mean that the permeability decays in a completely linear (proportional) relationship with the magnetic field strength, but also encompasses decay with a roughly linear relationship. Hereinafter, the region in the core characteristics where the permeability decays linearly with respect to the increase in magnetic field strength may be referred to as the "permeability decay region."

[0036] Therefore, in each of the above-described embodiments, a bias magnetic flux having a predetermined magnetic field strength within a specific range within the permeability decay region of the core characteristics is generated to set the base of the detection operation within that specific range. This specific range of permeability is preferably set to 40% to 60%, approximately 10% inside the permeability decay region (the range of permeability from approximately 30% to 70%). That is, the magnetic flux generator preferably generates a bias magnetic flux having a magnetic field strength within the permeability range of 40% to 60%, which corresponds to the specific range within the permeability decay region of the core characteristics of the magnetic core portion provided with the two coil portions L1 and L2. For example, the magnetic flux generator is configured to generate a bias magnetic flux having a magnetic field strength such that the permeability is 50%.

[0037] However, to generate such a magnetic field strength as a bias, the DC bias current and the DC current applied to the bias coil sections L3 and L4 must be of a certain magnitude. For example, in the example of Figure 5, a magnetic field strength of 45 oersteds (Oe) is required to achieve a magnetic permeability of 50%, and to generate a bias magnetic flux of that magnetic field strength in the third embodiment, the bias coil sections L3 and L4 must have approximately 1,000 turns and a current of approximately 150 mA must be applied to each coil. In other words, each of the above-mentioned embodiments requires power or a coil to generate the bias magnetic flux. Therefore, in the fourth embodiment, a magnet is used to generate the bias magnetic flux.

[0038] Fig. 6 is a schematic diagram showing the configuration of a sensor device 1 according to a fourth embodiment. The sensor device 1 according to the fourth embodiment will be described below with reference to Fig. 6. In the following description, the description will focus on configurations that are different from those in the first embodiment, and descriptions of configurations that are similar to those in the first embodiment will be omitted as appropriate.

[0039] The sensor device 1 according to the fourth embodiment includes a magnetic core 2, coils L1 and L2, a bias magnet 25, an AC signal circuit 3, a signal output terminal Vout, a ground terminal GND, and the like. The magnetic core 2 includes a U-shaped core 23 and a U-shaped core 24 that are butted together and connected via two bias magnets 25 to form a closed magnetic circuit, forming a core shape that can be called a UU-shaped core. In the magnetic core 2, the bottom of the U-shape of the U-shaped core 23 forms an outer leg 23a, and the bottom of the U-shape of the U-shaped core 24 forms an outer leg 24a. However, the shape of the magnetic core 2 in the fourth embodiment is not limited to the example shown in FIG. 6 . It is sufficient for the closed magnetic circuit to include one or more bias magnets 25, and the magnetic core 2 may have a core shape known as a ring core or an O-shaped core. Furthermore, the material and molding method of the magnetic core 2 are not limited. The magnetic core 2 in the fourth embodiment also corresponds to a first magnetic core.

[0040] The bias magnet section 25 is a magnet that generates a bias magnetic flux in the closed magnetic path of the magnetic core section 2. That is, the bias magnet section 25 is provided locally in the magnetic core section 2 so as to generate bias magnetic flux with polarity that circulates in the same direction in the closed magnetic path of the magnetic core section 2. In the example of Fig. 5, two bias magnet sections 25 are provided at positions facing each other on two connecting sections that connect the two outer legs so as to generate bias magnetic flux with polarity that circulates counterclockwise on the page in the closed magnetic path formed by the magnetic core section 2. As a result, the signal magnetic flux generated from the coil sections L1 and L2 and the bias magnetic flux generated by the bias magnet section 25 have polarity in the same direction in each of the outer legs 23a and 24a.

[0041] However, the positions and number of the bias magnet portions 25 are not limited to the example in Fig. 6. The bias magnet portions 25 may be provided inside the outer legs 23a and 24a of the magnetic core portion 2, or may be attached to the surface of the magnetic core portion 2. The bias magnet portions 25 may be provided at multiple locations on the diagonal line of the closed magnetic circuit on the surface or inside of the magnetic core portion 2.

[0042] Furthermore, as described above, the magnetic characteristics of the bias magnet portion 25 are not particularly limited as long as they can generate a bias magnetic flux with a magnetic field strength that is in the range of 40% or more and 60% or less of the magnetic permeability corresponding to a specific range within the magnetic permeability attenuation region in the core characteristics of the magnetic core portion 2.

[0043] Other configurations in the fourth embodiment, i.e., the AC signal circuit 3, the output terminals, etc., may be the same as those in the above-described embodiments. In the example of Fig. 6, the midpoint between the coil portion L1 and the coil portion L2 connected in series is connected to the signal output terminal Vout.

[0044] In this way, in the fourth embodiment, the bias magnetic flux is generated by the bias magnet unit 25, so the bias coil units L3 and L4 are not required, and power for generating the bias magnetic flux is also not required. Therefore, according to the fourth embodiment, the manufacturing cost and power consumption of the sensor device 1 can be reduced compared to the above-described embodiments.

[0045] [Detailed Circuit Configuration] In each of the above-described embodiments, a simple configuration is shown for the AC signal circuit 3, and only the signal output terminals V1 and V2 and Vout are shown on the signal output side of the coil portions L1 and L2. Therefore, specific configurations of the AC signal circuit 3 and the signal output circuit are exemplified below and explained. The AC signal circuit 3 and the signal output circuit shown below can be applied to any of the above-described embodiments. However, the circuit configurations of the above-described embodiments are not limited to the following examples.

[0046] 7 is a circuit diagram showing a first example of the AC signal circuit 3 and the signal output circuit 7. The AC signal circuit 3 includes a resonant capacitor C1, gate timing capacitors C2 and C3, transistors Q1 and Q2, gate bias resistors R1 to R4, a choke coil Lc, and a DC power supply, which together form a collector resonant self-oscillating circuit. The DC power supply is a power source that provides DC power and is a battery or a storage battery.

[0047] The coils L1 and L2 are connected in series, with their midpoint connected to the positive side of a DC power supply via a choke coil Lc. The other end of the coil L1 is connected to the negative side of the DC power supply via a transistor Q1, and the other end of the coil L2 is connected to the negative side of the DC power supply via a transistor Q2.

[0048] The resonant capacitor C1 is connected in parallel to the coils L1 and L2, and together with the coils L1 and L2, forms a resonant circuit. The transistors Q1 and Q2 are, for example, field effect transistors (FETs) or bipolar transistors, and can be described as a switching element pair. The drain of the transistor Q1 is connected to the coil L1, and the drain of the transistor Q2 is connected to the coil L2. The sources of the transistors Q1 and Q2 are connected to the negative side of a DC power supply. The gates of the transistors Q1 and Q2 are connected to a bias circuit.

[0049] The bias circuit is composed of gate bias resistors R1, R2, R3, and R4, and is connected in parallel to a DC power supply to apply a bias voltage to the gates of transistors Q1 and Q2. Specifically, a pair of resistors R1 and R2 connected in series and a pair of resistors R3 and R4 connected in series are connected in parallel, with the midpoint between resistors R1 and R2 connected to the gate of transistor Q1 and the midpoint between resistors R3 and R4 connected to the gate of transistor Q2.

[0050] The gate of transistor Q1 is connected to one end of resonant capacitor C1 via gate timing capacitor C2, and the gate of transistor Q2 is connected to the other end of resonant capacitor C1 via gate timing capacitor C3, so that the transistors Q1 and Q2 perform switching operations in response to the charging and discharging of resonant capacitor C1 and gate timing capacitors C2 and C3.

[0051] With the above configuration, the AC signal circuit 3 can apply an oscillation signal (sine wave signal) to the coils L1 and L2 based on DC power supplied from the DC power supply. Furthermore, the AC signal circuit 3 realizes a simplified circuit configuration by generating the oscillation signal using a self-excited oscillation circuit.

[0052] On the other hand, a signal output circuit 7 is provided on the signal output terminal Vout side of the coil portions L1 and L2. The signal output circuit 7 includes coupling capacitors C4 and C5, rectifier diodes D1, D2, D3 and D4, balancing resistors R5 and R6, output resistors R7 and R8, and an output capacitor C6.

[0053] Coupling capacitors C4 and C5 and rectifier diodes D1 to D4 form a voltage doubler rectifier circuit that rectifies the signal across coils L1 and L2 to both the positive and negative sides. Balancing resistors R5 and R6 and output resistors R7 and R8 divide the signal rectified by the voltage doubler rectifier circuit, and output capacitor C6 smoothes the divided signal and outputs the resulting DC signal to the signal output terminal Vout. Therefore, the output signal from the signal output terminal Vout can be called a detection signal that can detect the voltage balance between coils L1 and L2.

[0054] With the above configuration, when no external magnetic field is applied and no difference in inductance occurs between the coils L1 and L2, a DC signal having a voltage value (including voltage division by the balancing resistors R5 and R6, etc.) biased by the DC voltage supplied from the DC power supply of the AC signal circuit 3 is output from the signal output terminal Vout. On the other hand, when a difference occurs in the inductance between the coils L1 and L2 due to the action of an external magnetic field, the voltage value fluctuates up or down based on the biased voltage value according to the direction of the magnetic flux of the external magnetic field. Furthermore, the base voltage value of the output signal can be set arbitrarily by adjusting the ratio of the resistance values ​​of the balancing resistors R5 and R6 and the output resistors R7 and R8.

[0055] FIG. 8 is a diagram showing an example of an output signal when the AC signal circuit 3 and signal output circuit 7 shown in FIG. 7 are used. This example shows the output signal when the balance resistors R5 and R6 in the signal output circuit 7 have the same resistance value and the output resistor R8 is open. As shown in FIG. 8 , the output signal indicates the voltage value of the DC power supply of the AC signal circuit 3 (5 V = reference voltage value) when no external magnetic field is applied. When an external magnetic field is applied in a positive direction, the output signal indicates a voltage value higher than the reference voltage value. When an external magnetic field is applied in a negative direction, the output signal indicates a voltage value lower than the reference voltage value. The difference between the voltage value of the output signal and the reference voltage value increases depending on the strength of the external magnetic field. Thus, the AC signal circuit 3 and signal output circuit 7 shown in FIG. 7 can detect the strength and direction of an external magnetic field using the output signal.

[0056] 9 is a circuit diagram showing a second example of the AC signal circuit 3 and the signal output circuit 7. The following description of the circuit configuration of the second example will focus on the differences from the first example, and the same details as the first example will be omitted as appropriate.

[0057] The AC signal circuit 3 of the second example has the same circuit configuration as the first example, but differs in circuit connection from the first example. In the second example, the midpoint between the coils L1 and L2 is connected to the negative side (GND) of the DC power supply, the other end of the coil L1 is connected to the positive side of the DC power supply via a transistor Q1, and the other end of the coil L2 is connected to the positive side of the DC power supply via a transistor Q2. The source of the transistor Q1 is connected to the coil L1, the source of the transistor Q2 is connected to the coil L2, and the drains of the transistors Q1 and Q2 are connected to the positive side of the DC power supply.

[0058] The signal output circuit 7 of the second example differs from the circuit configuration of the first example in that it does not have an output resistor R8. The signal output circuit 7 of the second example also differs from the first example in circuit connection. While the midpoint of the rectifier diodes D1 and D2 in the first example is connected to the positive side of the DC power supply, in the second example, the midpoint of the rectifier diodes D1 and D2 is connected to the negative side (GND) of the DC power supply. Furthermore, an output capacitor C6 and an output resistor R7 are connected in parallel.

[0059] In this second example, the midpoint between the coils L1 and L2 and the midpoint between the rectifier diodes D1 and D2 are both connected to the negative side (GND) of the DC power supply. Therefore, when no external magnetic field is applied and no difference in the inductance between the coils L1 and L2 occurs, a DC signal corresponding to the ground (GND) potential is output from the signal output terminal Vout. On the other hand, when a difference in the inductance between the coils L1 and L2 occurs due to the application of an external magnetic field, a DC signal indicating the voltage difference between the coils L1 and L2 relative to the ground potential is output. Therefore, according to the second example, only the change in the voltage balance between the coils L1 and L2 due to the application of an external magnetic field can be indicated by the output signal.

[0060] FIG. 10 is a diagram showing an example of an output signal when the AC signal circuit 3 and signal output circuit 7 shown in FIG. 9 are applied. This example shows the output signal when the balance resistors R5 and R6 in the signal output circuit 7 have the same resistance value. As shown in FIG. 10, the output signal exhibits a voltage value (0 V) corresponding to ground potential when no external magnetic field is applied, a positive voltage value when the external magnetic field is applied in a positive direction, and a negative voltage value when the external magnetic field is applied in a negative direction. The absolute value of the voltage value of the output signal increases depending on the magnetic field strength of the external magnetic field. Thus, with the AC signal circuit 3 and signal output circuit 7 shown in FIG. 9, the output signal can not only detect the strength and direction of the external magnetic field, but also indicate only the change in the voltage balance of the coils L1 and L2 due to the application of the external magnetic field.

[0061] As mentioned above, the AC signal circuit 3 and the signal output circuit 7 are not limited to the circuit configurations shown in Figures 7 and 9. For example, in the AC signal circuits 3 of the first and second examples (see Figures 7 and 9), the resonant capacitor C1 is provided, which is connected in parallel to the coil portions L1 and L2. However, the resonant capacitor C1 may be omitted. Even in a configuration in which the resonant capacitor C1 is omitted, if the transistors Q1 and Q2 are FETs, self-oscillation is possible due to the output capacitance (Coss = drain-source capacitance (Cds) + gate-drain capacitance (Cgd)) of the transistors Q1 and Q2.

[0062] Fifth Embodiment When an external current generates an external magnetic field that can be detected by the sensor device 1 according to each of the above-described embodiments, the magnitude and direction of the external current can be detected by a detection signal output from the sensor device 1. In the fifth embodiment, a current sensor device 10 including the configuration of the first, second, third, or fourth embodiment will be described. The following description will focus on configurations that are different from the above-described embodiments, and descriptions of configurations that are similar to the above-described embodiments will be omitted as appropriate.

[0063] FIG. 11 is a schematic diagram showing the appearance of a current sensor device 10 according to a fifth embodiment. The current sensor device 10 according to the fifth embodiment includes a current detection magnetic core (hereinafter referred to as a current detection core) 15 in addition to the components of the sensor device 1 according to the first, second, third, or fourth embodiment. As shown in FIG. 11 , the current detection core 15 is a magnetic core having an air gap, which is interposed in a magnetic path formed by the flow of a current to be detected. In the example of FIG. 11 , the current detection core 15 is formed in a square ring shape with one side cut in the middle to provide a gap. However, the shape of the current detection core 15 is not limited to the example of FIG. 11 , and it may also be a doughnut-shaped shape with a gap in the middle, such as a toroidal core. Furthermore, the material and molding method of the current detection core 15 are not limited.

[0064] 11, the current line 12 through which the current to be detected flows is inserted inside the current detection core 15. However, the current line 12 may be wound around the current detection core 15.

[0065] In the current sensor device 10, the magnetic core portion 2 of the sensor device 1 preferably has a central core leg portion and two outer core legs, as illustrated in Fig. 1. That is, in the current sensor device 10, the magnetic core portion 2 preferably has a core shape known as an EE-type core or an EI-type core.

[0066] 12 is a partial schematic diagram showing the arrangement of the magnetic core portion 2 of the sensor device 1 in the current sensor device 10 according to the fifth embodiment. As shown in FIG. 11 , the magnetic core portion 2 is arranged in the air gap of the current detection core 15 so that the two outer core legs and the middle core leg extend in a direction perpendicular to the core end faces 15a and 15b of the current detection core 15, which face each other across the air gap. Furthermore, as shown in FIGS. 11 and 12 , the magnetic core portion 2 is preferably arranged in such a direction that the distances between the coil portions L1 and L2 and the current line 12 are approximately equal. This arrangement prevents the magnetic flux flowing through the two outer core legs of the magnetic core portion 2 due to the magnetic field generated by the current line 12 from becoming unbalanced.

[0067] Furthermore, the magnetic core portion 2 is preferably formed so that the area of ​​a cross section DM perpendicular to the extension direction of the core middle leg is equal to or larger than the area of ​​each of the core end faces 15a and 15b of the current detection core 15. In other words, the core middle leg of the magnetic core portion 2 preferably has a size (volume) that is not saturated by the magnetic flux generated by the current to be detected and flowing between the core end faces 15a and 15b of the current detection core 15 (hereinafter, sometimes referred to as external magnetic flux). In addition, as shown in Figure 12, the magnetic core portion 2 is preferably aligned so that the cross section DM of the core middle leg encompasses each of the core end faces 15a and 15b of the current detection core 15 when viewed from a direction perpendicular to the core end faces 15a and 15b (on the plane of Figure 12).

[0068] By doing so, most of the magnetic flux flowing in the magnetic core portion 2 of the sensor device 1 based on the magnetic flux (hereinafter sometimes referred to as external magnetic flux) generated by the current to be detected and flowing between the core end faces 15a and 15b of the current detection core 15 can be made to flow in the middle leg of the magnetic core portion 2, and the leakage portion can be made to flow in the outer leg of the magnetic core portion 2. In this case, by making the area of ​​the cross section DM of the middle leg of the magnetic core portion 2 larger than the areas of the core end faces 15a and 15b of the current detection core 15, the magnetic resistance of the middle leg of the core becomes sufficiently smaller than the magnetic resistance of the air gap. As a result, even if there is a slight misalignment between the center of the cross section DM of the middle leg of the core and the center of the core end faces 15a and 15b, it is possible to prevent the magnetic flux leaking to the two outer legs of the core from becoming unbalanced. As described in each of the above embodiments, by outputting a detection signal capable of detecting the voltage balance between the coil sections L1 and L2, it is possible to detect with high accuracy the amount and direction of the external magnetic flux generated by the current to be detected, and ultimately to detect with high accuracy the magnitude and direction of the current to be detected.

[0069] The current sensor device 10 according to the fifth embodiment preferably includes two types: one in which the core end faces 15a and 15b of the current detection core 15 are joined to the magnetic core portion 2 of the sensor device 1, and another in which a gap is provided between the core end faces 15a and 15b of the current detection core 15 and the magnetic core portion 2 of the sensor device 1. Because the amount of external magnetic flux changes depending on the magnitude of the current to be detected, the magnetic gap between the core end faces 15a and 15b of the current detection core 15 and the magnetic core portion 2 of the sensor device 1 absorbs the change in the amount of external magnetic flux, allowing the sensor device 1 to appropriately detect the current to be detected even with the same configuration. Specifically, when the current to be detected is large, the type in which a gap is provided between the core end faces 15a and 15b of the current detection core 15 and the magnetic core portion 2 of the sensor device 1 is used, and when the current to be detected is small, the type in which the core end faces 15a and 15b of the current detection core 15 are joined to the magnetic core portion 2 of the sensor device 1 is used.

[0070] 13(a), 13(b), and 13(c) are graphs showing examples of voltage signals (detection signals) output from the signal output terminals V1 and V2 of the current sensor device 10 according to the fifth embodiment. Each graph shows a detection signal output when an AC signal having a frequency of 1000 kHz (kilohertz) is applied to the coils L1 and L2 by the AC signal circuit 3. FIG. 13(a) shows a state in which no current to be detected flows through the current line 12, FIG. 13(b) shows a state in which a current to be detected of the same magnitude as that in FIG. 13(b) flows through the current line 12 in the opposite direction. The solid line indicates the voltage signal output from the signal output terminal V1, and the dashed line indicates the voltage signal output from the signal output terminal V2.

[0071] 13(a) shows that when no external magnetic field is generated by the current to be detected, there is no difference between the voltage signals output from the signal output terminals V1 and V2. Figures 13(b) and 13(c) show that when the current to be detected is flowing through the current line 12, a difference occurs between the voltage signals output from the signal output terminals V1 and V2. The magnitude of this difference indicates that the strength of the external magnetic field generated by the current to be detected and the magnitude of the current to be detected can be detected. Also, in Figures 13(b) and 13(c), the magnitudes of the voltage signals output from the signal output terminals V1 and V2 are reversed. This indicates that the direction of the external magnetic field generated by the current to be detected and the direction of the current to be detected can be detected by comparing the magnitudes of the voltage signals output from the signal output terminals V1 and V2.

[0072] Sixth Embodiment The current sensor device 10 according to the fifth embodiment described above includes the current detection core 15. However, the sensor device 1 may be configured to be disposed in proximity to the current line 12 without including the current detection core 15. Even in this case, the magnitude and direction of the current to be detected can be detected, as in the fifth embodiment, by using the sensor device 1 to detect an external magnetic field that is generated around the current line 12 when the current to be detected flows. In this case, if the strength of the external magnetic field is weak, the magnetic core portion 2 of the sensor device 1 may have a shape that does not include a core center leg portion.

[0073] The current sensor device 10 according to the sixth embodiment may include the sensor device 1 according to the first, second, third, or forty-third embodiment described above, and the sensor device 1 is installed in proximity to or in contact with a current line 12. The shape of the current line 12 is rod-shaped in the example of Fig. 11, but is not limited to such a shape. The current line 12 may be any plate- or rod-shaped conductive conductor known as a bus bar or the like.

[0074] Fig. 14 is a schematic diagram showing an example of the arrangement of the current sensor device 10 according to the sixth embodiment with respect to the current line 12. As shown in Fig. 14, the current sensor device 10 is arranged so that the two coil portions L1 and L2 of the sensor device 1 are close to or abut the conductor (current line 12) through which the current to be detected flows. The example of Fig. 14 illustrates the sensor device 1 according to the fourth embodiment, in which the coil portions L1 and L2 are close to the conductor and the arrangement of the coil portions L1 and L2 generally coincides with the flow direction of the current to be detected.

[0075] By arranging them in this manner, as shown in Figure 14 (b), the external magnetic field generated by the current to be detected acts equally on both of the outer legs 23a and 24a of the magnetic core portion 2, particularly on which coil portions L1 and L2 are provided, and when an external magnetic field is not generated by the current to be detected, no voltage difference occurs between coil portions L1 and L2, so the magnitude and direction of the current to be detected can be detected with high accuracy using this voltage difference.

[0076] In the first to fourth embodiments described above, the strength and direction of an external magnetic field can be detected by outputting the difference in voltage generated in the coils L1 and L2 due to the action of the external magnetic field, but in the fourth embodiment described above, the bias magnet 25 is interposed between the U-shaped core 23 and the U-shaped core 24 in the magnetic core 2, and therefore leakage flux corresponding to the voltage difference between the coils L1 and L2 may occur from the gap between the cores. In this case, if this leakage flux is coupled with the magnetic field of the external magnetic field, unnecessary noise may be superimposed on the current to be detected that is generating the external magnetic field.

[0077] Therefore, the sensor device 1 of the seventh embodiment is configured so that the signal magnetic flux generated from coil section L1 and the signal magnetic flux generated from coil section L2 circulate through different closed magnetic circuits, thereby preventing the generation of leakage magnetic flux corresponding to the voltage difference between coil sections L1 and L2.

[0078] The sensor device 1 according to the seventh embodiment will be described below with reference to Fig. 15 and Fig. 16. Fig. 15 is a schematic diagram showing the appearance of the sensor device 1 according to the seventh embodiment, and Fig. 16 is a schematic diagram showing the flow of signal magnetic flux and bias magnetic flux in the sensor device 1 according to the seventh embodiment. The following description will focus on configurations that are different from the first embodiment, and descriptions of configurations that are similar to those in the first embodiment will be omitted as appropriate.

[0079] The sensor device 1 according to the seventh embodiment includes a magnetic core portion, coil portions L1 and L2, a bias magnet portion 25, an AC signal circuit 3, a signal output circuit 7, a signal output terminal Vout, a ground terminal GND, etc., and the configuration of the magnetic core portion differs from that of each of the above-described embodiments. The bias magnet portion 25 is as described in the fourth embodiment, and the other configurations are as described in any of the embodiments.

[0080] The sensor device 1 according to the seventh embodiment has a structure in which a ring core 26 provided with a coil portion L1 and a ring core 27 provided with a coil portion L2 are connected via two bias magnet portions 25. The ring core 26 corresponds to the second magnetic core portion, and the ring core 27 corresponds to the third magnetic core portion. Specifically, the winding of the coil portion L1 is wound around one outer leg portion 26a of the ring core 26, and the winding of the coil portion L2 is wound around one outer leg portion 27a of the ring core 27. The surface of the ring core 26 provided with an opening and the surface of the ring core 27 provided with an opening face each other, and two bias magnet portions 25 are interposed between the outer leg end portions 26b and 27b at both ends of the outer legs 26a and 27a on which the coil portions L1 and L2 are provided on each of the opposing surfaces.

[0081] Such a configuration of the magnetic core portions generates bias magnetic flux and signal magnetic flux as shown in Fig. 16. Specifically, signal magnetic flux M1 generated from coil portion L1 in response to an AC signal applied by AC signal circuit 3 has a polarity that circulates in a closed magnetic circuit (corresponding to a second closed magnetic circuit) within ring core 26 in which coil portion L1 is provided, and signal magnetic flux M2 generated from coil portion L2 in response to the AC signal has a polarity that circulates in a closed magnetic circuit (corresponding to a third closed magnetic circuit) within ring core 27 in which coil portion L2 is provided. On the other hand, bias magnetic flux Mb generated by bias magnet portion 25 has a polarity that circulates in a closed magnetic circuit (corresponding to a first closed magnetic circuit) formed by the two bias magnet portions 25, a portion of ring core 26 (outer leg portion 26a and outer leg end portion 26b), and a portion of ring core 27 (outer leg portion 27a and outer leg end portion 27b), as shown in Fig. 16.

[0082] Therefore, in the seventh embodiment, the two bias magnet portions 25, a portion of the ring core 26 (the outer leg portion 26a and the outer leg end portion 26b), and a portion of the ring core 27 (the outer leg portion 27a and the outer leg end portion 27b) correspond to a first magnetic core portion that forms a first closed magnetic circuit. In each of the outer legs 26a and 27a on which the coil portions L1 and L2 are provided, the bias magnetic flux Mb and the signal magnetic fluxes M1 and M2 flow in the same direction (have the same polarity), as shown in FIG. 16 . Furthermore, in the seventh embodiment, the magnetic flux generating portion can be described as including two or more bias magnet portions 25 that are locally provided in the first magnetic core portion so as to generate bias magnetic fluxes with polarities that circulate in the same direction through the first closed magnetic circuit.

[0083] With this magnetic core configuration, the bias magnetic flux Mb is added to the signal magnetic fluxes M1 and M2, thereby generating a magnetic field strength within a specific range within the magnetic permeability attenuation region of the core characteristics of the ring cores 26 and 27 in at least the outer legs 26a and 27a where the coils L1 and L2 are provided. Furthermore, the signal magnetic fluxes M1 and M2 circulate in separate closed magnetic circuits (in the ring core 26 and the ring core 27), respectively, preventing the generation of leakage magnetic flux corresponding to the voltage difference between the coils L1 and L2 caused by the action of an external magnetic field. This prevents unnecessary noise from being superimposed on the current to be detected, which generates an external magnetic field, even when the sensor device 1 according to the seventh embodiment is used as a current sensor, as will be described later.

[0084] However, the core shape of the ring cores 26 and 27 is not limited to a ring core as long as it can form a closed magnetic path for the signal magnetic flux, and may be an O-type core, a UU-type core, a UI-type core, etc. Furthermore, the ring cores 26 and 27 may be any general magnetic core such as a ferrite core or a dust core, and the material and molding method thereof are not limited.

[0085] The arrangement of the bias magnet portion 25 is not limited to the example shown in Fig. 15 . For example, the bias magnet portion 25 may be longer than that shown in Fig. 15 , and instead of being interposed between the ring cores 26 and 27, it may be joined to the end faces of the ring cores 26 and 27 outside the faces where the openings of the ring cores 26 and 27 are provided, and provided so as to bridge between the ring cores 26 and 27. That is, the two bias magnet portions 25 may be arranged so that a closed magnetic circuit through which the bias magnetic flux circulates is formed by the two bias magnet portions 25, a part of the ring core 26 (including the outer leg portion 26a), and a part of the ring core 27 (including the outer leg portion 27a). Furthermore, although there is a possibility that the closed magnetic circuit through which the bias magnetic flux circulates may branch, the bias magnet portion 25 may be arranged at a position offset from the outer leg end portions 26b located at both ends of the outer legs 26a and 27a.

[0086] In the example of Fig. 15, the ring cores 26 and 27 are arranged so that their surfaces having openings face each other, but they may also be arranged as shown in Fig. 17. Fig. 17 is a schematic diagram showing the appearance of a sensor device 1 according to a modified example of the seventh embodiment. In the modified example shown in Fig. 17, the ring cores 26 and 27 are arranged so that their surfaces having openings are parallel to each other and so that the outer end faces (opposite the inner side where the openings are provided) of the outer leg portions 26a and 27a, on which the coil portions L1 and L2 are provided, face each other. The ring cores 26 and 27 are connected to each other via two bias magnet portions 25 provided between the outer end faces (opposite the inner side where the openings are provided) of the outer leg end portions 26b and 27b at both ends of the outer leg portions 26a and 27a. 16 , even with this configuration, the signal magnetic flux M1 generated from the coil portion L1 circulates in a closed magnetic circuit within the ring core 26 in which the coil portion L1 is provided, the signal magnetic flux M2 generated from the coil portion L2 circulates in a closed magnetic circuit within the ring core 27 in which the coil portion L2 is provided, and the bias magnetic flux Mb generated by the bias magnet portion 25 circulates in a closed magnetic circuit (corresponding to a first closed magnetic circuit) formed by the two bias magnet portions 25, a portion of the ring core 26 (outer leg portions 26 a and outer leg end portions 26 b), and a portion of the ring core 27 (outer leg portions 27 a and outer leg end portions 27 b). Therefore, even with this modified example, it is possible to prevent the generation of leakage magnetic flux corresponding to the voltage difference between the coil portions L1 and L2 that occurs due to the action of an external magnetic field.

[0087] [Eighth embodiment] The sensor device 1 according to the seventh embodiment can also be placed in a position close to or in contact with the current line 12, as in the sixth embodiment, to realize a current sensor device that detects the magnitude and direction of the current to be detected flowing through the current line 12.

[0088] 18 is a schematic diagram showing an example of the arrangement of the current sensor device 10 according to the eighth embodiment relative to the current line 12. As shown in Fig. 18, the current sensor device 10 is arranged so that the two coil portions L1 and L2 of the sensor device 1 are close to or in contact with the conductor (current line 12) through which the current to be detected flows. In the eighth embodiment, as in the sixth embodiment, the sensor device 1 is arranged so that the arrangement of the coil portions L1 and L2 generally coincides with the flow direction of the current to be detected.

[0089] Furthermore, in the arrangement of the eighth embodiment, the plane (imaginary plane) of the closed magnetic circuit through which the bias magnetic flux Mb circulates is parallel to the current line 12, and the plane (imaginary plane) of the closed magnetic circuit through which the signal magnetic fluxes M1 and M2 circulate is perpendicular to the current line 12. With this arrangement, also in the eighth embodiment, the external magnetic field generated by the current to be detected acts in the same manner on both of the outer legs 26 a and 27 a on which the coil portions L1 and L2 are provided, and the magnitude and direction of the current to be detected can be detected with high accuracy based on the voltage difference between the coil portions L1 and L2 generated by the action of the external magnetic field.

[0090] Even when using a sensor device 1 according to a modified example of the seventh embodiment (see FIG. 17 ), the sensor device 1 is similarly arranged such that the two coils L1 and L2 are adjacent to or in contact with the conductor (current line 12) through which the current to be detected flows, and the arrangement of the coils L1 and L2 generally coincides with the direction of the current to be detected. In this case, both the plane (imaginary plane) of the closed magnetic circuit through which the bias magnetic flux Mb circulates and the plane (imaginary plane) of the closed magnetic circuit through which the signal magnetic flux M1 and M2 circulate are parallel to the current line 12, so that the external magnetic field (main magnetic flux) generated by the current to be detected acts similarly on the entire ring cores 26 and 27. As a result, the change in magnetic permeability of the entire ring cores 26 and 27 is large, thereby improving detection sensitivity. Furthermore, this also prevents the generation of leakage magnetic flux corresponding to the voltage difference between the coils L1 and L2 due to the action of the external magnetic field, thereby preventing unnecessary noise from being superimposed on the current to be detected, which generates the external magnetic field.

[0091] [Modifications] The contents of each of the above-described embodiments can be modified as appropriate. That is, the sensor device 1 and the current sensor device 10 according to each embodiment are not limited to the circuit configuration examples shown in the drawings.

[0092] Depending on the relationship between the position of the magnetic core unit 2 of the sensor device 1 and the direction of the external magnetic field, the magnetic flux flowing through the outer core legs within the magnetic core unit 2 due to the external magnetic field may become unbalanced. For example, in the fourth embodiment described above, this may occur when the magnetic core unit 2 is not positioned so that the cross section DM of the middle core leg encompasses the core end faces 15a and 15b of the current detection core 15. In such a case, a correction circuit element corresponding to the magnetic flux imbalance between the outer core legs can be provided at the AC signal circuit 3 or the signal output terminals V1 and V2 to correct the output signal (detection signal), thereby achieving the same effect as in the previous embodiments. In this case, the correction circuit element is, for example, a circuit that applies a bias to one or both of the coil units L1 and L2 to offset the magnetic flux imbalance.

[0093] The present inventors have conducted an evaluation test of the current sensor device 10 described above, and the contents and results of the evaluation test will be described below as an example.

[0094] The current sensor device 10 evaluated was the sensor device 1 according to the fourth embodiment, which is equipped with the AC signal circuit 3 and signal output circuit 7 as a first example shown in FIG. 7 . In this evaluation test, the input power (DC power supply) of the AC signal circuit 3 was set to Vin 3.3 (V) and Iin 4.8 (mA), and the oscillation frequency was set to 1250 kHz. The current sensor device 10 housed in a case was fixed to a bus bar, and the voltage of the output signal output from the signal output terminal Vout of the current sensor device 10 was measured while changing the magnitude of the current to be detected flowing through the bus bar.

[0095] 19 is a graph showing the results of an evaluation test of the current sensor device 10 according to the present example. The horizontal axis represents the current value (DCI (A)) of the current to be detected that was passed through the bus bar, and the vertical axis represents the voltage change (ΔVout (mV)) of the output signal from the current sensor device 10. The current value of the current to be detected was varied as follows: 0 (A), ±2 (A), ±4 (A), ±6 (A), ±8 (A), ±10 (A), ±20 (A), ±30 (A), ±40 (A), ±50 (A), ±60 (A), ±70 (A), ±80 (A), ±90 (A), and ±100 (A). The voltage value of the output signal when the current to be detected was passed at each current value was measured, and the difference (ΔVout (mV)) from the voltage value of the output signal when the current to be detected was not passing, i.e., when the current value of the current to be detected was 0 (A), was calculated. FIG. 19 is a graph plotting combinations of the voltage change amount of the output signal calculated in this manner and the current value of the current to be detected.

[0096] Based on this graph, the least squares method was used to find an approximate straight line (theoretical calculation formula) of y = 1.4982x - 0.2333. Using this theoretical calculation formula, the theoretical value of the voltage change amount was calculated for each current value of the current to be detected, and the linearity error was calculated by dividing the difference between each calculated theoretical value of the voltage change amount and each measured value by the full-scale voltage (F.S.).

[0097] As a result, it was demonstrated that the current sensor device 10 under evaluation could suppress the linearity error to 0.28% or less when the current value of the current to be detected was varied within a range of ±100 (A). In other words, it was demonstrated that the current sensor device 10 under evaluation can achieve high detection accuracy. In addition, it was demonstrated that the current sensor device 10 does not use a Hall element, uses a magnet (bias magnet unit 25) to generate bias magnetic flux, and further employs a simple self-oscillation circuit, thereby suppressing power consumption (Vin 3.3 (V), Iin 4.8 (mA)).

[0098] Some or all of the above-described embodiments and modifications can be specified as follows: However, the above-described embodiments and modifications are not limited to the following descriptions.

[0099] <1> A sensor device comprising: a first magnetic core portion capable of forming a first closed magnetic circuit including two outer legs; two coil portions configured by windings around the two outer legs, each generating a signal magnetic flux in response to an applied AC signal; a magnetic flux generation portion generating a bias magnetic flux to circulate through the first closed magnetic circuit; an AC signal circuit applying an AC signal to the two coil portions so that the signal magnetic flux in the same direction as the bias magnetic flux is generated in each of the outer legs; and a signal output terminal outputting a detection signal capable of detecting a voltage balance between the two coil portions that changes in response to an external magnetic field acting on the first magnetic core portion. <2> The sensor device described in <1> above, wherein the magnetic flux generation portion generates the bias magnetic flux of a magnetic field strength falling within a permeability range of 40% to 60%, which corresponds to a specific range within a region where permeability linearly decreases with an increase in magnetic field strength in a core characteristic of the magnetic core portion provided with the two coil portions. <3> The sensor device according to <2> above, wherein the signal magnetic flux generated from the two coil units has polarity that circulates in the same direction through the first closed magnetic path, the AC signal circuit includes the magnetic flux generation unit, and the AC signal circuit applies the AC signal, on which a DC bias current corresponding to the bias magnetic flux is superimposed, to the two coil units. <4> The sensor device according to <2> above, wherein the signal magnetic flux generated from the two coil units has polarity that circulates in the same direction through the first closed magnetic path, and the magnetic flux generation unit includes: two bias coil units formed by windings around the two outer legs, respectively; and a DC signal circuit that applies DC signals to the two bias coil units so that the bias magnetic flux is generated with polarity that circulates in the same direction through the first closed magnetic path. <5> The sensor device described in <2> above, wherein the signal magnetic flux generated from the two coil portions has polarity that circulates in the same direction through the first closed magnetic circuit, and the magnetic flux generating portion includes a bias magnet portion that is locally provided in the first magnetic core portion so as to generate the bias magnetic flux with polarity that circulates in the same direction through the first closed magnetic circuit.<6> The sensor device according to <1> or <2> above, further comprising: a second magnetic core portion capable of forming a second closed magnetic circuit including one of the two outer legs and the other outer leg; and a third magnetic core portion capable of forming a third closed magnetic circuit including the other of the two outer legs and the other outer leg; wherein the magnetic flux generating portion includes two or more bias magnet portions locally provided in the first magnetic core portion so as to generate the bias magnetic flux with a polarity that circulates in the same direction through the first closed magnetic circuit; the signal magnetic flux generated from one of the two coil portions has a polarity that circulates through the second closed magnetic circuit, and the signal magnetic flux generated from the other of the two coil portions has a polarity that circulates through the third closed magnetic circuit; the second magnetic core portion and the third magnetic core portion are connected via the two or more bias magnet portions; and the first closed magnetic circuit is formed by the two or more bias magnet portions, a part of the second magnetic core portion, and a part of the third magnetic core portion. <7> The sensor device according to any one of <1> to <6> above, wherein the two coil sections are installed so as to be close to or in contact with a conductor through which a current to be detected flows, and wherein the current value of the current to be detected can be measured by the detection signal. <8> The sensor device according to any one of <1> to <7> above, wherein the two coil sections are connected in series in the AC signal circuit, and the signal output terminal is capable of outputting an intermediate signal level between the two coil sections as the detection signal. <9> The sensor device according to <8> above, wherein the AC signal circuit includes a self-oscillating circuit having a resonant capacitor connected in parallel to the two coil sections, and an oscillation signal output from the self-oscillating circuit is applied to both ends of the two coil sections.<10> The sensor device according to any one of <1> to <5>, <8> and <9>, further comprising: a current detection magnetic core having an air gap interposed in a magnetic path formed by the flow of a current to be detected, wherein the signal magnetic flux generated from the two coil portions has polarity that circulates in the same direction in the first closed magnetic path, the magnetic core portion further includes a middle leg portion, and the two outer legs and the middle leg portion are arranged in the air gap in an orientation that extends in a direction perpendicular to each core end face of the current detection magnetic core that faces across the air gap, the area of ​​a cross section of the magnetic core portion perpendicular to the extension direction of the middle leg portion is the same as or larger than the area of ​​the core end face of the current detection magnetic core, and the magnetic core portion is positioned so that the cross section of the middle leg portion encompasses the core end face of the current detection magnetic core when viewed from a direction perpendicular to the core end face. <11> The sensor device according to <10>, wherein the core end surface of the current detection magnetic core and the magnetic core portion are joined together. <12> The sensor device according to <10>, wherein a gap is provided between the core end surface of the current detection magnetic core and the magnetic core portion.

[0100] This application claims priority based on International Application No. PCT / JP2023 / 42221, filed November 24, 2023, the entire disclosure of which is incorporated herein by reference.

[0101] REFERENCE SIGNS LIST 1 sensor device 2 magnetic core portion 3 AC signal circuit 5 DC signal circuit 7 signal output circuit 10 current sensor device 12 current line 15 current detection core 15a, 15b core end surface 21, 22 E-shaped core 23, 24 U-shaped core 25 bias magnet portion 26, 27 ring core L1, L2 coil portion V1, V2, Vout signal output terminal

Claims

1. A sensor device comprising: a first magnetic core portion capable of forming a first closed magnetic circuit including two outer legs; two coil portions configured by windings around the two outer legs, each of which generates a signal magnetic flux in response to an applied AC signal; a magnetic flux generating portion which generates a bias magnetic flux to circulate through the first closed magnetic circuit; an AC signal circuit which applies an AC signal to the two coil portions so that the signal magnetic flux in the same direction as the bias magnetic flux is generated in each of the outer legs; and a signal output terminal which outputs a detection signal capable of detecting the voltage balance between the two coil portions which changes in response to an external magnetic field acting on the first magnetic core portion.

2. The sensor device described in claim 1, wherein the magnetic flux generating unit generates the bias magnetic flux of a magnetic field strength in the range of magnetic permeability of 40% or more and 60% or less, which corresponds to a specific range within an area where the magnetic permeability decays linearly with respect to an increase in magnetic field strength in the core characteristics of the magnetic core unit in which the two coil units are provided.

3. A sensor device as described in claim 2, wherein the signal magnetic flux generated from the two coil sections has a polarity that circulates in the same direction in the first closed magnetic circuit, the AC signal circuit includes the magnetic flux generating section, and the AC signal circuit applies the AC signal having a DC bias current superimposed thereon corresponding to the bias magnetic flux to the two coil sections.

4. A sensor device as described in claim 2, wherein the signal magnetic flux generated from the two coil sections has a polarity that circulates in the same direction through the first closed magnetic circuit, and the magnetic flux generating section includes: two bias coil sections each formed by winding wire around each of the two outer legs; and a DC signal circuit that applies a DC signal to the two bias coil sections so that the bias magnetic flux is generated with a polarity that circulates in the same direction through the first closed magnetic circuit.

5. A sensor device as described in claim 2, wherein the signal magnetic flux generated from the two coil portions has a polarity that circulates in the same direction through the first closed magnetic circuit, and the magnetic flux generating portion includes a bias magnet portion that is locally provided in the first magnetic core portion so as to generate the bias magnetic flux with a polarity that circulates in the same direction through the first closed magnetic circuit.

6. A sensor device as described in claim 1 or 2, further comprising: a second magnetic core portion capable of forming a second closed magnetic circuit including one of the two outer legs and the other outer leg; and a third magnetic core portion capable of forming a third closed magnetic circuit including the other of the two outer legs and the other outer leg; wherein the magnetic flux generating portion includes two or more bias magnet portions locally provided in the first magnetic core portion so as to generate the bias magnetic flux with a polarity that circulates in the same direction through the first closed magnetic circuit; the signal magnetic flux generated from one of the two coil portions has a polarity that circulates through the second closed magnetic circuit, and the signal magnetic flux generated from the other of the two coil portions has a polarity that circulates through the third closed magnetic circuit; the second magnetic core portion and the third magnetic core portion are connected via the two or more bias magnet portions; and the first closed magnetic circuit is formed by the two or more bias magnet portions, a portion of the second magnetic core portion and a portion of the third magnetic core portion.

7. A sensor device as claimed in any one of claims 1 to 6, wherein the two coil sections are arranged in close proximity to or in contact with a conductor through which a current to be detected flows, and the detection signal makes it possible to measure the current value of the current to be detected.

8. A sensor device as described in any one of claims 1 to 7, wherein the two coil sections are connected in series in the AC signal circuit, and the signal output terminal is capable of outputting an intermediate signal level of the two coil sections as the detection signal.

9. The sensor device according to claim 8, wherein the AC signal circuit includes a self-oscillating circuit having a resonant capacitor connected in parallel to the two coil sections, and an oscillation signal output from the self-oscillating circuit is applied to both ends of the two coil sections.

10. A sensor device as described in any one of claims 1 to 5, 8 and 9, further comprising: a current detection magnetic core having an air gap interposed in a magnetic path formed by the flow of a current to be detected; the signal magnetic flux generated from the two coil portions has a polarity that circulates in the same direction in the first closed magnetic path; the first magnetic core portion further includes a middle leg portion, and the two outer legs and the middle leg portion are arranged in the air gap in an orientation that extends in a direction perpendicular to each core end face that faces each other through the air gap in the current detection magnetic core; the area of ​​a cross section of the first magnetic core portion perpendicular to the extension direction of the middle leg portion is the same as or larger than the area of ​​the core end face of the current detection magnetic core; and the first magnetic core portion is aligned so that the cross section of the middle leg portion encompasses the core end face of the current detection magnetic core when viewed from a direction perpendicular to the core end face.

11. The sensor device according to claim 10, wherein the core end face of the current detection magnetic core and the first magnetic core portion are joined together.

12. The sensor device according to claim 10, wherein a gap is provided between the core end face of the current detection magnetic core and the first magnetic core portion.

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