Magnetic sensor and magnetic measurement device

Abstract

To provide a magnetic sensor and magnetic measurement device, which can suppress power consumption compared to conventional products.SOLUTION: A magnetic sensor is provided, comprising a magnetism detection unit configured to output a detection signal corresponding to external magnetism, a signal processing unit configured to generate an output signal by applying given signal processing to the detection signal, a current generation unit configured to generate a bias current, and a current limiting unit for limiting the flow of the bias current to the magnetism detection unit to within a given time period.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a magnetic sensor and a magnetic measurement device. [Background technology]

[0002] The following Patent Document 1 discloses a magnetic sensor and a biomagnetic measurement device that generates a bias magnetic field in a pickup coil in order to suppress sensitivity variations caused by environmental changes such as temperature, manufacturing variations, etc. In this magnetic sensor and biomagnetic measurement device, a bias magnetic field is generated in the pickup coil by passing a current generated by a constant current source circuit or a current proportional to the output signal of the magnetic sensor through the pickup coil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-100055 Summary of the Invention [Problem to be solved by the invention]

[0004] In the background art, a current (constant current) generated by a constant current source circuit or a current (feedback current) proportional to the output signal of a magnetic sensor is passed through a pickup coil as a bias current. In this background art, a magnetic field (magnetic field) having an opposite phase to the external magnetic field to be detected is generated in the pickup coil by the bias current.

[0005] However, in order to suppress the variation in sensitivity of the magnetic sensor, it is necessary to set the bias current to a relatively large current value. In other words, the background art has a problem of relatively large power consumption. For example, when applying the background art to a device that requires multiple magnetic sensors, the large power consumption of the magnetic sensors becomes an important technical issue that must be resolved.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a magnetic sensor and a magnetic measurement device that can reduce power consumption more than before. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention adopts, as a first solution relating to a magnetic sensor, a magnetic detection unit that outputs a detection signal corresponding to an external magnetic field, a signal processing unit that generates an output signal by performing a predetermined signal processing on the detection signal, a current generating unit that generates a bias current, and a current limiting unit that limits the supply of the bias current to the magnetic detection unit for a predetermined time.

[0008] The present invention employs, as a second solution relating to the magnetic sensor, the solution according to the first solution, in which the signal processing unit includes a correlated double sampling circuit that performs a sample-and-hold process on the detection signal.

[0009] The present invention employs, as a third solution related to a magnetic sensor, a solution according to the second solution, in which the correlated double sampling circuit includes a sample-and-hold circuit that acquires and holds two sample values ​​by sampling the detection signal at different timings, and an integration circuit that integrates the difference between the two sample values.

[0010] The present invention employs, as a fourth solution relating to the magnetic sensor, the solution according to the third solution, in which the integrating circuit is configured as a zero drift amplifier.

[0011] The present invention employs a fifth solution related to a magnetic sensor, in which, in any of the first to fourth solutions above, the current generating unit includes a resistor that generates the bias current based on the output signal, and the current limiting unit includes an open / close switch provided between the signal processing unit and the current generating unit or between the current generating unit and the magnetic detection unit.

[0012] The present invention employs a sixth solution relating to a magnetic sensor, which is any one of the first to fourth solutions described above, in which the magnetic detection unit includes a magnetic impedance element and a drive unit that applies a drive voltage to the magnetic impedance element.

[0013] The present invention provides a seventh solution related to the magnetic sensor according to the sixth solution, in which the drive section limits the application of the drive voltage in synchronization with the current limiting section limiting the current.

[0014] In the present invention, as a first solution related to a magnetic measurement device, a solution is adopted in which the magnetic measurement device includes a magnetic sensor related to any one of the first to fourth solutions, and a magnetic measurement unit that measures magnetism using the output signal.

[0015] The present invention employs, as a second solution relating to the magnetic measurement device, the solution according to the first solution relating to the magnetic measurement device, in which the external magnetism is biomagnetism generated in a living body. Effect of the Invention

[0016] According to the present invention, it is possible to provide a magnetic sensor and a magnetic measurement device that can reduce power consumption more than before. [Brief description of the drawings]

[0017] [Figure 1] 1 is a block diagram showing an overview of a magnetic sensor A1 according to a first embodiment of the present invention. [Diagram 2] 1 is a circuit diagram showing a detailed configuration of a magnetic sensor A1 according to a first embodiment of the present invention. [Diagram 3] 1 is a block diagram showing a configuration of a magnetic measurement device B1 according to a first embodiment of the present invention. [Figure 4] 4 is a timing chart showing the operation of the magnetic sensor A1 according to the first embodiment of the invention. [Diagram 5] 10 is a circuit diagram showing a detailed configuration of a magnetic sensor A2 according to a second embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [First embodiment] First, a first embodiment of the present invention will be described with reference to FIGS. As shown in Figure 1, the magnetic sensor A1 of the first embodiment includes a sensor head 1, a drive unit 2, a pickup coil 3, a signal processing unit 4, a high-voltage side current limiting unit 5H, a high-voltage side current generating unit 6H, a low-voltage side current limiting unit 5L, and a low-voltage side current generating unit 6L.

[0019] As will be described later in detail, R in Figure 1 P is the parasitic resistance of the pickup coil 3. The pickup coil 3 has a parasitic resistance R P In addition, the sensor head 1 and the pickup coil 3 (parasitic resistance R P ) constitutes a magnetic impedance element S.

[0020] The sensor head 1 is a two-terminal element with one end connected to the output end of the driver 2 and the other end grounded. This sensor head 1 is made of a magnetic material whose magnetic properties change when a drive voltage is applied from the driver 2 while an external magnetic field G is acting on it. That is, in this sensor head 1, a magnetization change according to the strength (magnitude) of the external magnetic field G, that is, a magnetic flux change, occurs in the sensor head 1.

[0021] The sensor head 1 is, for example, an amorphous wire. When a driving voltage is applied from the driving unit 2 to the sensor head 1 while an external magnetic field G is acting on it, the impedance of the sensor head 1 changes, and the magnetic flux penetrating the inside of the sensor head 1 changes. The amount of change in this impedance depends on the magnitude of the external magnetic field G.

[0022] The driver 2 has an output end connected to one end of the sensor head 1, and applies a predetermined drive voltage from the output end to one end of the sensor head 1. This driver 2 constitutes the magnetic comparison unit of the present invention together with the magnetic impedance element S. Such a driver 2 is a voltage source that generates a fluctuating voltage such as a pulse voltage or a high-frequency voltage, and outputs this fluctuating voltage to the sensor head 1 as a drive voltage MIE.

[0023] The pickup coil 3 is a winding wound around the sensor head 1. One end of the pickup coil 3 is connected to one input end (first input end) of the signal processing unit 4 and an output end of the high-voltage side current generating unit 6H, and the other end is connected to the other input end (second input end) of the signal processing unit 4 and an output end of the low-voltage side current generating unit 6L.

[0024] Such a pickup coil 3 is wound around the sensor head 1, and a change in magnetic flux on the surface of the sensor head 1 in response to an external magnetic field appears as an induced voltage at both ends of the coil through the pickup coil 3.

[0025] This induced voltage corresponds to the detection signal of the present invention, and as shown in the figure, the high-voltage side detection voltage V P and the low-voltage side detection voltage V generated at the other end of the pickup coil 3. N This induced voltage is the difference voltage between the input voltage V in The signal is input to the signal processing unit 4 as the signal.

[0026] As mentioned above, the pickup coil 3 has a certain parasitic resistance R P This parasitic resistance R P As shown in the figure, the parasitic resistance R functions as a resistor connected in series to the pickup coil 3 and has a predetermined resistance value (parasitic resistance value). In other words, when a current is passed through the pickup coil 3, the parasitic resistance R P The parasitic voltage V P occurs.

[0027] This parasitic voltage V P As described in the well-known document (JP 2022-100055 A), the parasitic voltage V P is the input voltage V input to the signal processing unit 4 in It is preferable to subtract from

[0028] As shown in the figure, signal processing unit 4 is a two-input, two-output electronic circuit. A first input terminal of signal processing unit 4 is connected to one end of pickup coil 3 and an output terminal of high-voltage side current generator 6H, and a second input terminal is connected to the other end of pickup coil 3 and an output terminal of low-voltage side current generator 6L.

[0029] The first output terminal of the signal processing unit 4 is connected to an external device (not shown) and a high-voltage side current limiting unit 5H, and outputs a positive-phase output signal V out Furthermore, the signal processing unit 4 has a second output terminal connected to the external device and the low-voltage side current limiting unit 5L, and outputs a negative-phase output signal V out Outputs (-).

[0030] Such a signal processing unit 4 detects the input voltage V in By applying a predetermined signal processing to the out (+) and inverted output signal V out (-) are generated. That is, these positive phase output signals V out (+) and inverted output signal V out (-) is an analog signal indicating the strength (magnitude) of the external magnetic field G detected by the pickup coil 3 (magnetic impedance element S).

[0031] The output signal of the signal processor 4 may be either an analog signal or a digital signal, but in the first embodiment, it is an analog signal. out(+) is a positive-phase analog voltage signal that indicates the strength (magnitude) of the external magnetic field G. In contrast, the negative-phase output signal V out (-) is an analog voltage signal of the opposite phase that indicates the strength (magnitude) of the external magnetic field G. The positive phase output signal V out (+) and inverse phase output signal V out (-) means that the amplitude is the same but the phase is inverted.

[0032] High-voltage side current limiting unit 5H has an input terminal connected to the first output terminal of signal processing unit 4 and an output terminal connected to the input terminal of high-voltage side current generating unit 6H. High-voltage side current limiting unit 5H receives positive phase output signal V out Supply / non-supply of (+) to high-voltage side current generating unit 6H is set based on a switching signal input from a control device (not shown).

[0033] That is, the high-voltage side current limiting unit 5H controls the positive phase output signal V out By setting the supply / non-supply to the (+) high-voltage side current generating unit 6H, the magnetic feedback current I fb The supply of current (bias current) to the pickup coil 3 is limited to a predetermined time.

[0034] The magnetic feedback current I fb generates a magnetic field according to the magnitude of the current through the pickup coil 3 to the nearby sensor head 1. That is, the magnetic feedback current I fb is the positive phase output signal V out (+) and inverse phase output signal V out Since it is proportional to the difference with (-), the magnetic feedback current I fb The magnetic field generated is also proportional to this difference and is in opposite phase to the external magnetic field G, which acts as a magnetic feedback and solves problems such as the nonlinearity of the magnetic impedance element S.

[0035] High-voltage side current generating unit 6H has an input terminal connected to the output terminal of high-voltage side current limiting unit 5H, and an output terminal connected to one end of pickup coil 3 and a first input terminal of signal processing unit 4. High-voltage side current generating unit 6H receives positive-phase output signal V out (+) based on magnetic feedback current I fb (bias current).

[0036] The input terminal of the low-voltage side current limiting unit 5L is connected to the second output terminal of the signal processing unit 4, and the output terminal is connected to the input terminal of the low-voltage side current generating unit 6L. out Supply / non-supply of (-) to low-voltage side current generating section 6L is set based on the above-mentioned switching signal.

[0037] That is, the low-voltage side current limiting unit 5L generates the negative phase output signal V out By setting the supply / non-supply to the low-voltage side current generating unit 6L of (-), the magnetic feedback current I fb The supply of current (bias current) to the pickup coil 3 is limited to a predetermined time.

[0038] Here, although details will be described later, the above-mentioned drive unit 2 is a high-voltage side current limiting unit 5H and a low-voltage side current limiting unit 5L, and a magnetic feedback current I fb The application of the drive voltage to the sensor head is limited in synchronization with the limiting of the current (bias current) passing through the pickup coil.

[0039] The low-voltage side current generating unit 6L has an input terminal connected to the output terminal of the low-voltage side current limiting unit 5L, and an output terminal connected to the other end of the pickup coil 3 and the second input terminal of the signal processing unit 4. The low-voltage side current limiting unit 5L receives the negative-phase output signal V out (-) based on magnetic feedback current I fb (bias current).

[0040] Next, a specific circuit configuration of the magnetic sensor A1 will be described with reference to FIG. As shown in FIG. 2, the signal processing unit 4 of the magnetic sensor A1 includes a first switch 4a, a second switch 4b, a third switch 4c, a fourth switch 4d, a first capacitor 4e, a second capacitor 4f, a fifth switch 4g, a sixth switch 4h, a seventh switch 4i, an eighth switch 4j, a ninth switch 4k, a tenth switch 4m, a third capacitor 4n, a fourth capacitor 4p, an eleventh switch 4q, a twelfth switch 4r, a differential amplifier 4s, a fifth capacitor 4t and a sixth capacitor 4u.

[0041] That is, the signal processing unit 4 includes 12 open / close switches, six capacitors, and one differential amplifier. The first switch 4a is an open / close switch (electronically controlled switch) with two contacts and a control end. The first switch 4a has a first contact connected to one end of the pickup coil 3 and a first contact of the second switch 4b, and a second contact connected to a first contact of the third switch 4c and one end of the first capacitor 4e.

[0042] The first switch 4a has a control end connected to a control device (not shown). The control device is an electronic device that comprehensively controls the magnetic sensor A1 shown in Fig. 2. The first switch 4a is set to an open or closed state based on a first sampling signal SMPL input from the control device.

[0043] The second switch 4b is an open / close switch (electronically controlled switch) having two contacts and a control terminal. The first contact of the second switch 4b is connected to one end of the pickup coil 3 and the first contact of the first switch 4a, and the second contact is connected to the first contact of the fourth switch 4d and one end of the second capacitor 4f. The control terminal of the second switch 4b is connected to the above-mentioned control device (not shown), and the open / close state is set based on the second sampling signal CDS input from the control device.

[0044] The third switch 4c is an open / close switch (electronically controlled switch) having two contacts and a control terminal. The first contact of the third switch 4c is connected to the second contact of the first switch 4a and one end of the first capacitor 4e, and the second contact is grounded. The control terminal of the third switch 4c is connected to the above-mentioned control device (not shown), and the open / close state is set based on a timing signal Tx input from the control device.

[0045] The fourth switch 4d is an open / close switch (electronically controlled switch) with two contacts and a control terminal. The first contact of this fourth switch 4d is connected to the second contact of the second switch 4b and one end of the second capacitor 4f, and the second contact is grounded. The control terminal of the fourth switch 4d is connected to the above-mentioned control device (not shown), and the open / close state is set based on the timing signal Tx in the same manner as the third switch 4c.

[0046] The first capacitor 4e is a two-terminal element having a predetermined capacitance. One end of the first capacitor 4e is connected to the second contact of the first switch 4a and the first contact of the third switch 4c, and the other end is connected to the first contact of the fifth switch 4g and the first contact of the sixth switch 4h. The other end of the first capacitor 4e is also connected to one end of the third capacitor 4n.

[0047] The second capacitor 4f is a two-terminal element having a predetermined capacitance. One end of the second capacitor 4f is connected to the second contact of the second switch 4b and the first contact of the fourth switch 4d, and the other end is connected to one end of the fourth capacitor 4p, the first contact of the eleventh switch 4q, and the first contact of the twelfth switch 4r.

[0048] The fifth switch 4g is an open / close switch (electronically controlled switch) with two contacts and a control terminal. The first contact of the fifth switch 4g is connected to one end of the third capacitor 4n in addition to the other end of the first capacitor 4e and the first contact of the sixth switch 4h, and the second contact is grounded. The control terminal of the fifth switch 4g is connected to the above-mentioned control device (not shown), and the open / close state is set based on the first sampling signal SMPL in the same manner as the first switch 4a.

[0049] The sixth switch 4h is an open / close switch (electronically controlled switch) having two contacts and a control terminal. The sixth switch 4h has a first contact connected to the other terminal of the first capacitor 4e, the first contact of the fifth switch 4g, and one terminal of the third capacitor 4n, and a second contact connected to the positive phase input terminal of the differential amplifier 4s and one terminal of the fifth capacitor 4t. The sixth switch 4h has a control terminal connected to the above-mentioned control device (not shown), and the open / close state is set based on a timing signal Tx input from the control device, similar to the third switch 4c and the fourth switch 4d.

[0050] The seventh switch 4i is an open / close switch (electronically controlled switch) having two contacts and a control terminal. The seventh switch 4i has a first contact connected to the other end of the pickup coil 3 and the first contact of the eighth switch 4j, and a second contact connected to the first contact of the ninth switch 4k and the other end of the third capacitor 4n. The seventh switch 4i has a control terminal connected to the above-mentioned control device (not shown), and the open / close state is set based on the first sampling signal SMPL, similar to the first switch 4a and the fifth switch 4g.

[0051] The eighth switch 4j is an open / close switch (electronically controlled switch) having two contacts and a control terminal. The first contact of the eighth switch 4j is connected to the other end of the pickup coil 3 and the first contact of the seventh switch 4i, and the second contact is connected to the first contact of the tenth switch 4m and the other end of the fourth capacitor 4p. The control terminal of the eighth switch 4j is connected to the above-mentioned control device (not shown), and the open / close state is set based on the second sampling signal CDS in the same manner as the above-mentioned second switch 4b.

[0052] The ninth switch 4k is an open / close switch (electronically controlled switch) having two contacts and a control terminal. The first contact of the ninth switch 4k is connected to the second contact of the seventh switch 4i and the other end of the third capacitor 4n, and the second contact is grounded. The control terminal of the ninth switch 4k is connected to the above-mentioned control device (not shown), and the open / close state is set based on the timing signal Tx in the same manner as the above-mentioned third switch 4c, fourth switch 4d, and sixth switch 4h.

[0053] The tenth switch 4m is an open / close switch (electronically controlled switch) having two contacts and a control terminal. The first contact of the tenth switch 4m is connected to the second contact of the eighth switch 4j and the other end of the fourth capacitor 4p, and the second contact is grounded. The control terminal of the tenth switch 4m is connected to a control device (not shown), and the open / close state is set based on the timing signal Tx in the same manner as the third switch 4c, the fourth switch 4d, the sixth switch 4h, and the ninth switch 4k described above.

[0054] The third capacitor 4n is a two-terminal element having a predetermined capacitance. One end of the third capacitor 4n is connected to the other end of the second capacitor 4f, the first contact of the eleventh switch 4q, and the first contact of the twelfth switch 4r, and the other end is connected to the second contact of the seventh switch 4i and the first contact of the ninth switch 4k.

[0055] The fourth capacitor 4p is a two-terminal element having a predetermined capacitance. One end of the fourth capacitor 4p is connected to the other end of the first capacitor 4e, the first contact of the fifth switch 4g, and the first contact of the sixth switch 4h, and the other end is connected to the second contact of the eighth switch 4j and the first contact of the tenth switch 4m.

[0056] The eleventh switch 4q is an open / close switch (electronically controlled switch) with two contacts and a control terminal. The first contact of the eleventh switch 4q is connected to the other end of the second capacitor 4f in addition to the other end of the third capacitor 4n and the first contact of the twelfth switch 4r, and the second contact is grounded. The control terminal of the eleventh switch 4q is connected to a control device (not shown), and the open / close state of the eleventh switch 4q is set based on the first sampling signal SMPL, similar to the first switch 4a, the fifth switch 4g, and the seventh switch 4i described above.

[0057] The twelfth switch 4r is an open / close switch (electronically controlled switch) having two contacts and a control terminal. The first contact of the twelfth switch 4r is connected to the other end of the second capacitor 4f in addition to the other end of the third capacitor 4n and the first contact of the eleventh switch 4q, and the second contact is connected to the negative phase input terminal of the differential amplifier 4s and one end of the sixth capacitor 4u. The control terminal of the twelfth switch 4r is connected to a control device (not shown), and the open / close state is set based on the timing signal Tx in the same manner as the third switch 4c, the fourth switch 4d, the sixth switch 4h, the ninth switch 4k, and the tenth switch 4m described above.

[0058] The differential amplifier 4s is a two-input, two-output integrated circuit as shown in the drawing. The positive-phase input terminal of this differential amplifier 4s is connected to the second contact of the sixth switch 4h and one end of the fifth capacitor 4t, and the negative-phase input terminal is connected to the second contact of the twelfth switch 4r and one end of the sixth capacitor 4u.

[0059] The positive-phase output terminal of the differential amplifier 4s is connected to the other terminal of the fifth capacitor 4t and the input terminal of the high-voltage side current limiting unit 5H, and is also connected to the above-mentioned external device. The negative-phase output terminal of the differential amplifier 4s is connected to the other terminal of the sixth capacitor 4u and the input terminal of the low-voltage side current limiting unit 5L, and is also connected to the above-mentioned external device.

[0060] The fifth capacitor 4t is a two-terminal element having a predetermined capacitance. One end of the fifth capacitor 4t is connected to the second contact of the sixth switch 4h and the positive input terminal of the differential amplifier 4s, and the other end is connected to the positive input terminal of the differential amplifier 4s and the external device described above.

[0061] The sixth capacitor 4u is a two-terminal element having a predetermined capacitance. One end of the sixth capacitor 4u is connected to the second contact of the twelfth switch 4r and the negative phase input terminal of the differential amplifier 4s, and the other end is connected to the negative phase input terminal of the differential amplifier 4s and the external device described above.

[0062] Here, among the components of the magnetic sensor A1, the first switch 4a, the second switch 4b, the third switch 4c, the fourth switch 4d, the first capacitor 4e, the second capacitor 4f, the fifth switch 4g, the seventh switch 4i, the eighth switch 4j, the ninth switch 4k, the tenth switch 4m, the third capacitor 4n, the fourth capacitor 4p and the eleventh switch 4q constitute the sample-hold circuit Ka in the first embodiment.

[0063] In this sample-and-hold circuit Ka, the first capacitor 4e and the fourth capacitor 4p are mutually connected at the other end of the first capacitor 4e and one end of the fourth capacitor 4p. Such first capacitor 4e and fourth capacitor 4p constitute a first series circuit. Also, the second capacitor 4f and the third capacitor 4n are mutually connected at the other end of the second capacitor 4f and one end of the third capacitor 4n. Such second capacitor 4f and third capacitor 4n constitute a second series circuit.

[0064] As will be described in detail later, this sample-and-hold circuit Ka detects the high-voltage side detection voltage V at different timings based on the well-known correlated double sampling method. P and low voltage detection voltage V N This is a correlated double sampling circuit that acquires and holds two sample values ​​by performing sample-and-hold processing on the detection signal.

[0065] The differential amplifier 4s, the fifth capacitor 4t, and the sixth capacitor 4u constitute the integrating circuit Kb in the first embodiment. The integrating circuit Kb integrates the difference between the high-voltage side detection voltage VH input from the sample-and-hold circuit Ka via the sixth switch 4h and the low-voltage side detection voltage VL input from the sample-and-hold circuit Ka via the twelfth switch 4r to generate the positive-phase output signal V out (+) and inverted output signal V out Produces (-).

[0066] Here, the integrating circuit Kb may be configured as a well-known zero drift amplifier. There are several known circuit configurations for the zero drift amplifier, and for example, a chopper type or chopper type auto-zero type circuit configuration may be adopted. Also, a circuit configuration in which a correlated double sampling technique different from the above is applied to the differential amplifier may be adopted.

[0067] By configuring the integrating circuit Kb as a zero drift amplifier, it is possible to suppress drift due to input offset voltage and 1 / f noise caused by characteristic variations of the transistors constituting the differential amplifier 4s, etc. In other words, by adopting a zero drift amplifier as the integrating circuit Kb, it is possible to improve the accuracy of the magnetic sensor A1.

[0068] 2, high-voltage side current limiting unit 5H includes switch 5a. Switch 5a is an electronically controlled switch that includes two contacts and a control terminal. One end of switch 5a is connected to the positive phase output terminal of differential amplifier 4s and the other end of fifth capacitor 4t, and the other end is connected to the input terminal of high-voltage side current generating unit 6H.

[0069] The control end of the open / close switch 5a is connected to the above-mentioned control device (not shown). That is, the open / close switch 5a is an electronically controlled switch whose open / close state is set based on a switching signal EN input from the control device to the control end, and the positive phase output signal V out Supply / non-supply to (+) high-voltage side current generating unit 6H is set based on the above-mentioned switching signal.

[0070] As shown in the figure, high-voltage side current generating unit 6H is equipped with resistor 6a. This resistor 6a is a two-terminal element having a predetermined resistance value, with one end connected to the second contact of open / close switch 5a in high-voltage side current limiting unit 5H, and the other end connected to one end of pickup coil 3, the first contact of first switch 4a, and the first contact of second switch 4b.

[0071] Such a resistor 6a is connected to one end of the positive-phase output signal V out (+) is the magnetic feedback current I fb In other words, the high-voltage side current generating unit 6H shown in FIG. 2 functions as a voltage / current converter that converts the magnetic feedback current I fb This is the simplest circuit in the current generating section of the present invention that generates a bias current.

[0072] The low-voltage side current limiting unit 5L includes an open / close switch 5b. The open / close switch 5b is an electronically controlled switch that includes two contacts and a control terminal. One terminal of the open / close switch 5b is connected to the negative-phase output terminal of the differential amplifier 4s and the other terminal of the sixth capacitor 4u, and the other terminal is connected to the input terminal of the low-voltage side current generating unit 6L.

[0073] Similarly to the switch 5a of the high-voltage side current limiting unit 5H, the switch 5b has a control terminal connected to the control device (not shown). That is, the switch 5a has an open / closed state set based on a switching signal EN input to the control terminal, similar to the switch 5a, and the negative-phase output signal V out Supply / non-supply of (-) to low-voltage side current generating section 6L is set based on the above-mentioned switching signal.

[0074] As shown in the figure, the low-voltage side current generating unit 6L includes a resistor 6b, which is a two-terminal element having a predetermined resistance value, with one end connected to the second contact of the open / close switch 5b in the low-voltage side current limiting unit 5L, and the other end connected to the other end of the pickup coil 3, the first contact of the seventh switch 4i, and the first contact of the eighth switch 4j.

[0075] Such a resistor 6b is connected to one end of the inverted output signal V out (-) is the magnetic feedback current I fb In other words, the low-voltage side current generating unit 6L shown in FIG. 2 functions as a voltage / current converter that converts the magnetic feedback current I fb This is the simplest circuit in the current generating section of the present invention that generates a bias current.

[0076] Next, the magnetic measurement device C1 according to the first embodiment will be described with reference to FIG. As shown in FIG. 3, the magnetic measurement device C1 includes a plurality of magnetic sensors A1 according to the first embodiment and positive-phase output signals V out (+) and inverted output signal V out The apparatus further includes four magnetic measurement units E1 to E4 that use (-) to measure magnetism (biomagnetism) emitted by a living body.

[0077] The magnetic sensors A1 detect biomagnetism generated by various organs in the human body, for example. That is, the magnetic sensors A1 detect magnetism generated by the brain (brain magnetism), magnetism generated by nerves (neuromagnetism), magnetism generated by the heart (cardiac magnetism), and magnetism generated by muscles (muscle magnetism).

[0078] The magnetic sensor A1 for detecting brain magnetism is connected to a first magnetic measurement unit E1, and outputs a positive-phase output signal V out (+) and inverted output signal V out The magnetic sensor A1 for detecting neuromagnetism is connected to a second magnetic measurement unit E2, and outputs a positive phase output signal V out (+) and inverted output signal V out Outputs (-).

[0079] The magnetic sensor A1 for detecting cardiac magnetism is connected to a third magnetic measurement unit E3, and outputs a positive phase output signal V indicative of cardiac magnetism to the third magnetic measurement unit E3. out (+) and inverted output signal V out The magnetic sensor A1 for detecting muscle magnetism is connected to the fourth magnetic measurement unit E4, and outputs a positive phase output signal V out (+) and inverted output signal V out Outputs (-).

[0080] The first magnetic measurement unit E1 outputs a positive phase output signal V out (+) and inverted output signal V out The second magnetic measurement unit E2 measures the intensity and distribution of the brain magnetism based on the positive phase output signal V out (+) and inverted output signal V out The third magnetic measurement unit E3 measures the intensity and distribution of neuromagnetic fields based on the positive phase signal V out (+) and inverted output signal V out The fourth magnetic measurement unit E4 measures the strength and distribution of the cardiac magnetism based on the positive phase output signal Vout (+) and inverted output signal V out Based on (-), the strength and distribution of muscle magnetism is measured and output to the outside.

[0081] According to the magnetic measuring device C1, a stable and high-resolution (picotesla level) biomagnetic measuring device can be realized with small size and low power consumption. That is, according to the magnetic measuring device C1, there is no need to use a known magnetic sensor head (SQUID, etc.) for biomagnetic measurement, and it is possible to realize a significant reduction in size and cost.

[0082] Next, the operations of the magnetic sensor A1 and the magnetic measurement device C1 according to the first embodiment will be described in detail with reference to the timing chart shown in FIG.

[0083] This timing chart shows the various signals described above, namely, the switching signal EN for controlling the open / close switch 5a (high-voltage side current limiting section 5H) and the open / close switch 5b (low-voltage side current limiting section 5L), the drive voltage MIE for the sensor head 1, the first sampling signal SMPL for controlling the first switch 4a, the fifth switch 4g, the seventh switch 4i, and the eleventh switch 4q, the second sampling signal CDS for controlling the second switch 4b and the eighth switch 4j, the timing signal Tx for controlling the third switch 4c, the fourth switch 4d, the sixth switch 4h, the ninth switch 4k, the tenth switch 4m, and the twelfth switch 4r, and the input voltage V in and output signal D out This shows the relationship between

[0084] First, the switching signal EN transitions from L (Low level) to H (Hi level) at time t1, causing the magnetic feedback current I fb The magnetic feedback current I fb As a result of the current flow, the input voltage V in rises from 0V to the bias voltage Vb.

[0085] At this time t1, the drive voltage MIE is not input to the sensor head 1, so the pickup coil 3 (magnetic impedance element S) is not in a state where it can detect the external magnetic field G. The bias voltage Vb is P The magnetic feedback current I fb is the voltage resulting from the flow of

[0086] Here, at time t1, in addition to the transition of the switching signal EN from "L" to "H", the first sampling signal SMPL and the second sampling signal CDS transition from "L" to "H". Due to these transitions of the first sampling signal SMPL and the second sampling signal CDS, the first switch 4a, the fifth switch 4g, the seventh switch 4i, the eleventh switch 4q, the second switch 4b, and the eighth switch 4j are set from "open" (open state) to "closed" (closed state).

[0087] Also, at this time t1, the timing signal Tx transitions from "H" to "L." Due to this transition of the timing signal Tx, the third switch 4c, the fourth switch 4d, the sixth switch 4h, the ninth switch 4k, the tenth switch 4m, and the twelfth switch 4r are set from "closed" to "open."

[0088] That is, at time t1, a high-voltage side detection voltage VB corresponding to the bias voltage Vb is applied to one end of the first capacitor 4e and the second capacitor 4f. P The other ends of the first capacitor 4e and the second capacitor 4f are grounded. The other ends of the third capacitor 4n and the fourth capacitor 4p are applied with a low-voltage detection voltage VB corresponding to the bias voltage Vb. N is applied, and one end of the third capacitor 4n and one end of the fourth capacitor 4p are grounded.

[0089] As a result, the first capacitor 4e and the second capacitor 4f are connected to the high-voltage side detection voltage VB P The third capacitor 4n and the fourth capacitor 4p are charged by the low-voltage side detection voltage VB N is charged by.

[0090] Then, at time t2, a predetermined time after time t1, the second sampling signal CDS transitions from "H" to "L." That is, at this time t2, the high-voltage side detection voltage VB P The application of the high voltage detection voltage VB P At time t2, the low-voltage side detection voltage VB N The application of the low voltage detection voltage VB N is held.

[0091] Then, at time t3, a predetermined time after time t2, the drive voltage MIE is supplied to the sensor head 1, and the pickup coil 3 (magnetic impedance element S) is in a state where it can detect the external magnetic field G. As a result, the input voltage V in is the magnetic feedback current I fb When an external magnetic field G is detected with the bias current (bias current) flowing and with the drive voltage MIE being supplied to the sensor head 1, the voltage Vb increases above the bias voltage Vb and reaches a peak voltage Vm at time t4.

[0092] A high-voltage side detection voltage VM corresponding to the peak voltage Vm is applied to one end of the first capacitor 4e. P A low-voltage detection voltage VM corresponding to the peak voltage Vm is applied to the other end of the fourth capacitor 4p. N As a result, the first capacitor 4e is charged to the high-voltage side detection voltage VM P The fourth capacitor 4p is charged by the low-voltage side detection voltage VM N is charged by.

[0093] Then, at time t4, the first sampling signal SMPL transitions from “H” to “L.” That is, at this time t4, the high-voltage side detection voltage VM PThe application of the high voltage detection voltage VM P The low-voltage side detection voltage VM N The application of the low voltage detection voltage VM N is held.

[0094] Then, at time t5, when a predetermined time has elapsed from time t4, the switching signal EN and the driving voltage MIE transition from "H" to "L." That is, the application of the driving voltage by the driving unit 2 to the sensor head 1 is controlled by the magnetic feedback current I fb The bias current is limited in synchronization with the current flow to the pickup coil 3.

[0095] As a result, at time t5, the magnetic feedback current I fb The supply of the magnetic feedback current I fb At the same time that the supply of the bias current to the pickup coil 3 ends, the application of the drive voltage MIE to the sensor head 1 ends.

[0096] Then, at time t6, when a predetermined time has elapsed since the time t5, the timing signal Tx transitions from "L" to "H." That is, the third switch 4c, the fourth switch 4d, the sixth switch 4h, the ninth switch 4k, the tenth switch 4m, and the twelfth switch 4r are set from "open" to "closed" at time t6.

[0097] As a result, the fourth capacitor 4p in the first series circuit is connected in parallel to the first capacitor 4e with a polarity opposite to that during charging, and the third capacitor 4n in the second series circuit is connected in parallel to the second capacitor 4f with a polarity opposite to that during charging.

[0098] That is, the voltage at the connection point between the first capacitor 4e and the fourth capacitor 4p is the high-voltage side detection voltage VH obtained by subtracting the bias voltage Vb from the peak voltage Vm at the high-voltage side detection voltage VH, and the voltage at the connection point between the second capacitor 4f and the third capacitor 4n is the low-voltage side detection voltage VL obtained by subtracting the bias voltage Vb from the peak voltage Vm at the low-voltage side detection voltage VL.

[0099] Here, the high-voltage side detection voltage VB held in the first capacitor 4e and the second capacitor 4f during the period from time t1 to t2 is P and the low-voltage side detection voltage VL held in the third capacitor 4n and the fourth capacitor 4p. P is the first sample value. Also, high-voltage side detection voltage VM P and the low-voltage side detection voltage VM held in the fourth capacitor 4p. P is the second sample value.

[0100] Of these first and second sample values, the high-voltage side detection voltage VB P and high voltage detection voltage VM P is the high voltage detection voltage V P The two sample values ​​(high-voltage side sample values) are sampled at different times for the low-voltage side detection voltage VL P and low voltage detection voltage VM P is the low voltage detection voltage V N are two sample values ​​(low-voltage side sample values) sampled at different times.

[0101] The high-voltage side detection voltage VH and the low-voltage side detection voltage VL generated by the operation of the sample-and-hold circuit Ka over the period from time t1 to t5 are output from the sample-and-hold circuit Ka to the integrating circuit Kb at time t5. The integrating circuit Kb then differentially amplifies the high-voltage side detection voltage VH and the low-voltage side detection voltage VL to generate the positive-phase output signal V out (+) and inverted output signal V out Outputs (-).

[0102] The magnetic sensor A1 and magnetic measurement device C1 according to the first embodiment include a pickup coil 3 (magnetic detection unit) that outputs a detection signal in response to an external magnetic field G, and an input voltage V in By applying a predetermined signal processing to the detection signal, a positive phase output signal V out (+) and inverted output signal V out A signal processor 4 generates a magnetic feedback current I fb The magnetic detection unit includes a high-voltage side current generating unit 6H and a low-voltage side current generating unit 6L that generate a bias current, and a high-voltage side current limiting unit 5H and a low-voltage side current limiting unit 5L that limit the supply of the bias current to the magnetic detection unit for a predetermined time.

[0103] That is, according to the first embodiment, by providing the high-voltage side current limiting unit 5H and the low-voltage side current limiting unit 5L, the magnetic feedback current I fb By limiting the period during which a current (bias current) is applied to the pickup coil 3 (magnetic detection unit), it is possible to provide a magnetic sensor A1 and a magnetic measurement device C1 that can reduce power consumption more than ever before.

[0104] In the magnetic sensor A1 and the magnetic measurement device C1 according to the first embodiment, the signal processing unit 4 detects the input voltage V in Since the pickup coil 3 (magnetic detection unit) is equipped with a correlated double sampling circuit that performs sample-and-hold processing on the detection signal, the parasitic resistance R P Therefore, according to the first embodiment, it is possible to detect the external magnetic field G with high accuracy.

[0105] In addition, in the magnetic sensor A1 and the magnetic measurement device C1 according to the first embodiment, the correlated double sampling circuit detects the input voltage V in The first embodiment includes a sample-and-hold circuit Ka that obtains and holds two sample values ​​by sampling the detection signal at different timings, and an integration circuit Kb that integrates the difference between the two sample values. According to the first embodiment, it is possible to suppress the influence of the parasitic resistance RP with a simple circuit configuration.

[0106] Moreover, in the magnetic sensor A1 and the magnetic measurement device C1 according to the first embodiment, the differential amplifier Kb is configured as a zero-drift amplifier, so that the external magnetic field G can be detected with high accuracy.

[0107] In the magnetic sensor A1 and the magnetic measurement device C1 according to the first embodiment, the high-voltage side current generating unit 6H and the low-voltage side current generating unit 6L generate a positive-phase output signal V out (+) and inverted output signal V out (-) based on magnetic feedback current I fb The high-voltage side current limiting unit 5H and the low-voltage side current limiting unit 5L each include an open / close switch 5a, 5b provided between the signal processing unit 4 and the current generating unit.

[0108] According to the first embodiment, it is possible to configure high-voltage side current generating section 6H, low-voltage side current generating section 6L, high-voltage side current limiting section 5H, and low-voltage side current limiting section 5L with a simple circuit configuration.

[0109] Furthermore, in the magnetic sensor A1 and magnetic measuring device C1 of the first embodiment, the magnetic detection unit includes a magnetic impedance element S and a driving unit 2 that applies a driving voltage MIE to the magnetic impedance element S, so that it is possible to detect external magnetic fields G with high sensitivity.

[0110] According to the first embodiment, the driving unit 2 controls the magnetic feedback current I fb Since the application of the driving voltage MIE to the sensor head 1 is limited in synchronization with the current limit of the bias current, it is possible to reduce the power consumption of the driving unit 2. Therefore, this also makes it possible to reduce the power consumption of the magnetic sensor A1 and the magnetic measurement device C1.

[0111] Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. The magnetic sensor A2 according to the second embodiment is configured as a single-ended circuit as shown in the figure. In Fig. 5, the same components as those in Figs. 1 and 2 of the first embodiment are denoted by the same reference numerals. The following mainly describes the points that are different from the first embodiment.

[0112] This magnetic sensor A2 has a pickup coil 3 (magnetic detection unit) that outputs a detection signal in response to an external magnetic field G, and an input voltage V in By applying a predetermined signal processing to the (detection signal), an output signal V out and a signal processor 7 for generating a magnetic feedback current I fb (bias current), and a magnetic feedback current I fb and a current limiting unit 8 that limits the current (bias current) flowing through the pickup coil 3 (magnetic detection unit) to a predetermined time.

[0113] In the second embodiment, the signal processing unit 7 includes a first switch 7a, a second switch 7b, a third switch 7c, a fourth switch 7d, a first capacitor 7e, a second capacitor 7f, a fifth switch 7g, a sixth switch 7h, a differential amplifier 7i, and a third capacitor 7j, as shown in the figure.

[0114] Among these components, the first switch 7a, the second switch 7b, the third switch 7c, the fourth switch 7d, the first capacitor 7e, the second capacitor 7f, and the fifth switch 7g constitute a sample-and-hold circuit Kc, while the differential amplifier 7i and the third capacitor 7j constitute an integrating circuit.

[0115] The first switch 7a is an open / close switch (electronically controlled switch) with two contacts and a control terminal. The first contact of the first switch 7a is connected to one end of the pickup coil 3 and the first contact of the second switch 7b, and the second contact is connected to the first contact of the third switch 7c and one end of the first capacitor 7e.

[0116] The first switch 7a has a control end connected to a control device (not shown). The control device is an electronic device that comprehensively controls the magnetic sensor A2 shown in Fig. 5. The first switch 7a is set to an open or closed state based on a first sampling signal SMPL input from the control device.

[0117] The second switch 7b is an open / close switch (electronically controlled switch) having two contacts and a control terminal. The first contact of this second switch 7b is connected to one end of the pickup coil 3 and the first contact of the first switch 7a, and the second contact is connected to the first contact of the fourth switch 7d and one end of the second capacitor 7f. The control terminal of the second switch 7b is connected to the above-mentioned control device (not shown), and the open / close state is set based on the second sampling signal CDS input from the control device.

[0118] The third switch 7c is an open / close switch (electronically controlled switch) having two contacts and a control terminal. The first contact of the third switch 7c is connected to the second contact of the first switch 7a and one end of the first capacitor 7e, and the second contact is grounded. The control terminal of the third switch 7c is connected to the above-mentioned control device (not shown), and the open / close state is set based on a timing signal Tx input from the control device.

[0119] The fourth switch 7d is an open / close switch (electronically controlled switch) having two contacts and a control terminal. The first contact of the fourth switch 7d is connected to the second contact of the second switch 7b and one end of the second capacitor 7f, and the second contact is connected to the other end of the first capacitor 7e, one end of the fifth switch 7g, and one end of the sixth switch 7h. The control terminal of the fourth switch 7d is connected to the above-mentioned control device (not shown), and the open / close state is set based on the timing signal Tx, similar to the third switch 7c.

[0120] The first capacitor 7e is a two-terminal element having a predetermined capacitance. One end of the first capacitor 7e is connected to the second contact of the first switch 7a and the first contact of the third switch 7c, and the other end is connected to the first contact of the fifth switch 7g, the second contact of the fourth switch 7d, and the first contact of the sixth switch 7h.

[0121] The second capacitor 7f is a two-terminal element having a predetermined capacitance. One end of the second capacitor 7f is connected to the second contact of the second switch 7b and the first contact of the fourth switch 7d, and the other end is grounded.

[0122] The fifth switch 7g is an open / close switch (electronically controlled switch) having two contacts and a control terminal. The first contact of the fifth switch 7g is connected to the other end of the first capacitor 7e, the second contact of the fourth switch 7d, and the first contact of the sixth switch 7h, and the second contact is grounded. The control terminal of the fifth switch 7g is connected to the above-mentioned control device (not shown), and the open / close state is set based on the first sampling signal SMPL in the same manner as the first switch 4a.

[0123] The sixth switch 7h is an open / close switch (electronically controlled switch) having two contacts and a control terminal. The sixth switch 7h has a first contact connected to the other end of the first capacitor 7e, a second contact of the fourth switch 7d, and a first contact of the fifth switch 7g, and a second contact connected to the negative phase input terminal of the differential amplifier 7i and one end of the third capacitor 7j. The sixth switch 7h has a control terminal connected to the above-mentioned control device (not shown), and the open / close state is set based on the timing signal Tx in the same manner as the third switch 4c and the fourth switch 4d.

[0124] As shown in the figure, the differential amplifier 7i is an integrated circuit with two inputs and one output. The negative input terminal of this differential amplifier 7i is connected to the second contact of the sixth switch 7h and one end of the third capacitor 7j, and the positive input terminal is grounded. The output terminal of this differential amplifier 7i is connected to the other end of the third capacitor 7j and the input terminal of the current limiting unit 8, and is also connected to an external device.

[0125] The third capacitor 7j is a two-terminal element having a predetermined capacitance. One end of the third capacitor 7j is connected to the second contact of the sixth switch 7h and the inverting input terminal of the differential amplifier 7i, and the other end is connected to the output terminal of the differential amplifier 7i and an external device.

[0126] In the sample-and-hold circuit Kc in the second embodiment, the first capacitor 7e and the second capacitor 7f are connected in parallel via the fourth switch 7d. That is, the other end of the first capacitor 7e is connected to the other end of the second capacitor 7f via the fourth switch 7d.

[0127] The sample-and-hold circuit Kc is a correlated double sampling circuit that obtains and holds sample values ​​by performing sample-and-hold processing on the detection voltage Vc (detection signal) at different timings based on a well-known correlated double sampling method. Also, the integrating circuit Kd in the second embodiment amplifies the detection voltage Vs input from the sample-and-hold circuit Kc via the sixth switch 7h to generate an output signal V out Generate.

[0128] In the second embodiment, the current limiting unit 8 includes an open / close switch 8a. The open / close switch 8a is an open / close switch (electronically controlled switch) that has two contacts and a control terminal. A first contact of the open / close switch 8a is connected to the output terminal of the differential amplifier 7i and the other terminal of the third capacitor 7j, and a second contact is connected to the input terminal of the current generating unit 9.

[0129] The control end of the open / close switch 8a is connected to the above-mentioned control device (not shown). That is, the open / close switch 8a is an electronically controlled switch whose open / close state is set based on a switching signal EN input from the control device to the control end, and the output signal V out Supply / non-supply of the current to the current generating unit 9 is set based on the switching signal EN.

[0130] In the second embodiment, the current generating unit 9 includes a resistor 9a. The resistor 9a is a two-terminal element having a predetermined resistance value, with one end connected to the second contact of the open / close switch 8a in the current limiting unit 8 and the other end connected to one end of the pickup coil 3, the first contact of the first switch 7a, and the first contact of the second switch 7b.

[0131] Next, an operation of the magnetic sensor A2 according to the second embodiment will be described. Note that since the operation of the magnetic sensor A2 is similar to that of the first embodiment, the operation of the magnetic sensor A2 will be described with reference to the timing chart of FIG.

[0132] This timing chart shows the switching signal EN, the driving voltage MIE, the first sampling signal SMPL, the second sampling signal CDS, the timing signal Tx, and the input voltage V in and output signal D out This shows the relationship between

[0133] When the switching signal EN transitions from “L” to “H” at time t1, the magnetic feedback current I fb The magnetic feedback current I fb As a result of the current flow, the input voltage V in rises from 0V to the bias voltage Vb.

[0134] At this time t1, the drive voltage MIE is not input to the sensor head 1, so the pickup coil 3 (magnetic impedance element S) is not in a state where it can detect the external magnetic field G. The bias voltage Vb is P The magnetic feedback current I fb is the voltage resulting from the flow of

[0135] Here, at time t1, in addition to the transition of the switching signal EN from "L" to "H", the first sampling signal SMPL and the second sampling signal CDS transition from "L" to "H". Due to these transitions of the first sampling signal SMPL and the second sampling signal CDS, the first switch 7a, the second switch 7b and the fifth switch 7g are set from "open" (open state) to "closed" (closed state).

[0136] Also, at this time t1, the timing signal Tx transitions from "H" to "L." Due to this transition of the timing signal Tx, the third switch 7c, the fourth switch 7d, and the sixth switch 7h are set from "closed" to "open."

[0137] That is, at time t1, a high-voltage side detection voltage VB corresponding to the bias voltage Vb is applied to one end of the first capacitor 7e and the second capacitor 7f. P is applied to the first capacitor 7e and the second capacitor 7f, and the other ends of the first capacitor 7e and the second capacitor 7f are grounded. As a result, the first capacitor 7e and the second capacitor 7f are in is charged by the input voltage V in Hold the.

[0138] Then, at time t2, when a predetermined time has elapsed from time t1, the second sampling signal CDS transitions from “H” to “L.” That is, at this time t2, the input voltage V in The application of is interrupted.

[0139] Then, at time t3, a predetermined time after time t2, the drive voltage MIE is supplied to the sensor head 1, and the pickup coil 3 (magnetic impedance element S) is in a state where it can detect the external magnetic field G. As a result, the input voltage V in is the magnetic feedback current I fb When an external magnetic field G is detected with the bias current (bias current) flowing and with the drive voltage MIE being supplied to the sensor head 1, the voltage Vb increases above the bias voltage Vb and reaches a peak voltage Vm at time t4.

[0140] A high-voltage side detection voltage VM corresponding to the peak voltage Vm is applied to one end of the first capacitor 7e. P As a result, the first capacitor 7e is connected to the input voltage V in is charged by the input voltage V in Hold the.

[0141] Then, at the time t4, the first sampling signal SMPL transitions from “H” to “L.” That is, at this time t4, the input voltage V in The application of is interrupted.

[0142] Then, at time t5, when a predetermined time has elapsed from time t4, the switching signal EN and the driving voltage MIE transition from "H" to "L." That is, at time t5, the magnetic feedback current I fb The supply of the bias current to the pickup coil 3 is terminated, and the supply of the drive voltage MIE to the sensor head 1 is terminated.

[0143] Then, at time t6, which is a predetermined time after time t5, the timing signal Tx transitions from "L" to "H." That is, the third switch 7c, the fourth switch 7d, and the sixth switch 7h are set from "open" to "closed" at time t6.

[0144] As a result, the second capacitor 7f is connected in series with the first capacitor 7e with polarity opposite to that during charging, so that the voltage at the connection point between the first capacitor 7e and the second capacitor 7f becomes the detection voltage Vc obtained by subtracting the bias voltage Vb from the peak voltage Vm.

[0145] The detection voltage Vc generated by the operation of the sample-and-hold circuit Kc from time t1 to time t5 is output from the sample-and-hold circuit Kc to the integrating circuit Kd at time t5. The integrating circuit Kd then differentially amplifies the detection voltage Vc to generate an output signal V out Generate.

[0146] The magnetic sensor A2 and the magnetic measurement device C2 according to the second embodiment include a pickup coil 3 (magnetic detection unit) that outputs a detection signal in response to an external magnetic field G, and an input voltage V in By applying a predetermined signal processing to the (detection signal), an output signal V out and a signal processor 7 for generating a magnetic feedback current I fb The magnetic sensor includes a current generating unit 9 that generates a bias current, and a current limiting unit 8 that limits the supply of the bias current to the magnetic detection unit for a predetermined period of time.

[0147] Therefore, according to the second embodiment, since the current limiting unit 8 is provided, the magnetic feedback current I fb It is possible to limit the period during which a current (bias current) is applied to the pickup coil 3 (magnetic detection unit). Therefore, according to the second embodiment, it is possible to provide a magnetic sensor A2 and a magnetic measurement device C2 that can reduce power consumption more than in the past.

[0148] The present invention is not limited to the above-described embodiment, and the following modifications are possible. (1) In the above embodiment, the bias current is generated based on the output signal. fb However, the present invention is not limited to this. A constant current generated independently of the output signal may be used as the bias current.

[0149] (2) In the above embodiment, the magnetic feedback current I fb A magnetic feedback current I (bias current) was passed through a coil (magnetic feedback coil) provided separately from the pickup coil 3. fb (bias current) may be passed through.

[0150] (3) In the above embodiment, the magnetic measuring device that measures biomagnetism as an external magnetic field G has been described, but the present invention is not limited thereto. The magnetic measuring device according to the present invention is capable of detecting various external devices other than biomagnetism with low power consumption and high accuracy. [Explanation of symbols]

[0151] A1, A2 magnetic sensors C1 Magnetic measurement device E1 Magnetic measurement section G External magnetic field Ka, Kc sample and hold circuit Kb, Kd integration circuit S Magnetic impedance element 1 Sensor head 2 Drive unit 3 Pickup coil 4. Signal Processing Section 4a First Switch 4b Second switch 4c 3rd switch 4d 4th switch 4e First capacitor 4f Second Capacitor 4g 5th switch 4h 6th switch 4i 7th switch 4j 8th switch 4k 9th Switch 4m 10th switch 4n 3rd Capacitor 4p 4th capacitor 4q 11th switch 4r 12th switch 4s differential amplifier 4t 5th capacitor 4u 6th Capacitor 5L Low voltage side current limiting section 5H High voltage side current limiting section 6L Low voltage side current generating section 6H High voltage side current generator 7 Signal Processing Section 7a First Switch 7b Second switch 7c 3rd switch 7d 4th switch 7e First capacitor 7f Second Capacitor 7g 5th switch 7h 6th switch 7i Differential Amplifier 7j 3rd Capacitor 8 Current limiting section 9 Current generation section

Claims

1. a magnetic detection unit that outputs a detection signal in response to an external magnetic field; a signal processing unit that performs a predetermined signal processing on the detection signal to generate an output signal; a current generating unit that generates a bias current; a current limiting unit that limits the bias current to be applied to the magnetic detection unit for a predetermined time; A magnetic sensor comprising:

2. The magnetic sensor according to claim 1 , wherein the signal processing unit includes a correlated double sampling circuit.

3. The correlated double sampling circuit comprises: a sample-and-hold circuit that samples the detection signal at different timings to obtain and hold two sample values; an integrating circuit for integrating the difference between the two sample values; 3. The magnetic sensor according to claim 2, further comprising:

4. 4. The magnetic sensor according to claim 3, wherein the integrating circuit is configured as a zero drift amplifier.

5. the current generating unit includes a resistor that generates the bias current based on the output signal; The current limiting unit includes an open / close switch provided between the signal processing unit and the current generating unit or between the current generating unit and the magnetic detection unit.

3. The magnetic sensor according to claim 1, wherein the first and second electrodes are arranged in a first direction.

6. The magnetic detection unit includes: A magnetic impedance element; A drive unit that applies a drive voltage to the magnetic impedance element; 4. The magnetic sensor according to claim 1, further comprising:

7. 7. The magnetic sensor according to claim 6, wherein the drive section limits the application of the drive voltage in synchronization with the current limiting section limiting the current.

8. The magnetic sensor according to claim 1 or 2, a magnetic measurement unit that measures the external magnetic field using the output signal; A magnetic measuring device comprising:

9. 9. The magnetic measuring device according to claim 8, wherein the external magnetic field is a biomagnetic field generated in a living body.

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