Magnetic sensor and biomagnetic measuring device

Abstract

A magnetic sensor characterized by comprising: a magnetic sensitive body whose electromagnetic characteristics change by the action of an external magnetic field; a coil configured to obtain an induced voltage in proportion to the external magnetic field; a sampler that samples the induced voltage generated in the coil to obtain a sampled voltage; and an automatic correction circuit that relatively adjusts the rising edge timing of a magnetic sensitive body clock that drives the magnetic sensitive body and the rising edge timing of a sampler clock that drives the sampler, based on the sampled voltage.

Description

TECHNICAL FIELD

[0001] The present application relates to a magnetic sensor and a living body magnetic measurement device. BACKGROUND

[0002] A magnetic sensor composed of a magnetic impedance element needs to perform envelope detection in order to perform external magnetic field strength detection. Since external magnetic field strength detection needs to be performed at high speed, generally, synchronous detection based on peak value sampling is used.

[0003] For example, Patent Literature 1 discloses a magnetic impedance effect micro magnetic sensor having a high magnetic permeability magnetic body head that is excited in a circumferential direction by pulse current, a coil that is wound along the circumferential direction of the high magnetic permeability magnetic body head, and an electronic switch that detects a first pulse of an induced voltage of the coil.

[0004] Patent Literature 2 discloses a magnetic sensor having a magnetic sensitive body whose electromagnetic characteristics change by the action of an external magnetic field, a drive circuit that supplies a current to the magnetic sensitive body, a detection coil that is wound around the magnetic sensitive body, and a sample-and-hold circuit that measures the magnitude of an induced voltage that is induced in the detection coil. The sample-and-hold circuit of Patent Literature 2 is configured to measure the induced voltage value in synchronization with the cut-off of the current of the drive circuit.

[0005] Patent Literature 3 discloses a magnetic impedance sensor having a magnetic impedance element that has a magnetic sensitive wire composed of an amorphous alloy that is a soft magnetic alloy that becomes zero magnetostriction, and has a detection coil that is separated by an insulator around the magnetic sensitive wire, detects a voltage that is generated from the detection coil according to an external magnetic field by applying a high frequency current to the magnetic sensitive wire, a current supply device that supplies a high frequency current to the magnetic impedance element, and a signal processing circuit that performs signal processing on an output from the detection coil.

[0006] Patent Literature 4 discloses an ultra-high sensitivity micro magnetic sensor composed of: a unit that causes a pulse current to flow through a magnetic field detection element and a magnetic field detection magnetic wire that has conductivity, in which the magnetic field detection element is provided with the magnetic wire, a coil that is wound around the magnetic wire, two electrodes for magnetic wire current supply, and two electrodes for coil voltage detection on a substrate; a signal processing circuit that senses a coil voltage that is generated when the pulse current flows; and a unit that converts the coil voltage into an external magnetic field H.

[0007] Patent Literature 5 discloses a magnetic impedance sensor composed of a magnetic impedance element that supplies a pulse current or a high frequency current to an amorphous wire, and outputs an alternating current decay vibration voltage of a magnitude corresponding to an external magnetic field that is induced in a detection coil that is wound around the amorphous wire.

[0008] Prior Art Documents

[0009] Patent Documents

[0010] Patent Document 1: Japanese Patent No. 3645116

[0011] Patent Document 2: Japanese Patent No. 3801194

[0012] Patent Document 3: Japanese Patent No. 4655247

[0013] Patent Document 4: Japanese Patent No. 6506466

[0014] Patent Document 5: Japanese Patent No. 5924503 SUMMARY

[0015] PROBLEMS TO BE SOLVED BY THE INVENTION

[0016] However, in the magnetic sensor described in Patent Documents 1 to 4, adjustment of the time from driving the magnetic impedance element to performing peak sampling is performed by a delay circuit based on a constant of an element, which is configured by a CMOS (Complementary Metal Oxide Semiconductor) inverter, an RC circuit, or the like. Therefore, there is a problem that the timing of peak sampling shifts due to environmental changes, manufacturing variations, and the like, and thus the sensitivity (V / T) of the magnetic sensor deviates.

[0017] By applying strong negative feedback (magnetic feedback) with a large loop gain as in Patent Document 1 and Patent Document 5, it is possible to suppress the sensitivity (V / T) deviation of the magnetic sensor.

[0018] On the other hand, the sensitivity reduction due to the timing error of peak sampling also reduces the loop gain, and causes gain variation, noise characteristic degradation, and the like, and thus appropriate timing adjustment is required even in the case where strong negative feedback is implemented. However, in the case where the above-described delay amount adjustment (trimming) is individually performed for each manufactured magnetic sensor by an RC time constant or the like, a drastic cost increase can be caused. Furthermore, even in the case where strong negative feedback is implemented as in Patent Document 1 and Patent Document 5, the sensitivity variation due to environmental changes over time cannot be sufficiently suppressed.

[0019] The present application has been achieved in order to solve the above-described problems, and aims to provide a magnetic sensor and a biomagnetic measurement apparatus that can automatically correct the optimal sampling timing for synchronous detection without increasing the cost even in the case where there are environmental changes and manufacturing variations, and that are excellent in detection accuracy.

[0020] Solutions for solving the problem

[0021] To solve the above problems, the present application provides the following solutions.

[0022] (1) One solution of the magnetic sensor of the present application is characterized by comprising:

[0023] a magnetic sensitive body whose electromagnetic characteristics change by the action of an external magnetic field;

[0024] a coil configured to obtain an induced voltage proportional to the external magnetic field;

[0025] a sampler that samples the induced voltage generated in the coil to obtain a sampled voltage; and

[0026] an automatic correction circuit that relatively adjusts the rising edge timing of a magnetic sensitive body clock that drives the magnetic sensitive body and the rising edge timing of a sampler clock that drives the sampler, based on the sampled voltage,

[0027] the automatic correction circuit detects a delay time until the sampled voltage first becomes a peak value by observing the displacement of the sampled voltage from a predetermined period after the rising of the magnetic sensitive body clock, and sets the rising edge timings of the magnetic sensitive body clock and the sampler clock to be staggered by a time corresponding to the delay time.

[0028] (2) The magnetic sensor according to (1), characterized in that the automatic correction circuit comprises:

[0029] a delay synchronization circuit having a plurality of delay elements connected in cascade;

[0030] a logic circuit that outputs a selection signal Dctrl that selects any one of the outputs of the plurality of delay elements in the delay synchronization circuit each time the sampled voltage is input, and records the selection signal Dctrl output at the timing at which the induced voltage generated in the coil becomes a peak value;

[0031] a multiplexer that selects any one of the respective outputs of the plurality of delay elements in the delay synchronization circuit according to the selection signal Dctrl, and generates the sampler clock; and

[0032] a clock generation circuit that generates the magnetic sensitive body clock.

[0033] (3) The magnetic sensor according to (1) or (2), characterized in that,

[0034] The automatic correction circuit further has a detection circuit that outputs peak sampling state information having information of a timing at which the induced voltage generated in the coil becomes a peak value, based on the sampling voltage.

[0035] (4) The magnetic sensor according to (3), characterized in that

[0036] The detection circuit has an analog-digital conversion circuit,

[0037] The analog-digital conversion circuit converts the sampling voltage into the peak sampling state information.

[0038] (5) The magnetic sensor according to (3), characterized in that

[0039] The detection circuit has a comparator,

[0040] The comparator outputs information binarized based on a prescribed threshold value as the peak sampling state information.

[0041] (6) The magnetic sensor according to any one of (1) to (5), characterized in that

[0042] A constant current source circuit is connected to the coil.

[0043] (7) One aspect of the biomagnetism measuring apparatus of the present application is characterized by comprising:

[0044] The magnetic sensor according to any one of (1) to (6); and

[0045] A biomagnetism measuring section that measures a magnetic field emitted by a living body using an output signal from the magnetic sensor.

[0046] Effects of the Invention

[0047] According to the present application, it is possible to provide a magnetic sensor and a biomagnetism measuring apparatus that can automatically correct an optimal sampling timing for synchronous detection without increasing costs even in the presence of environmental changes and manufacturing variations, and that have excellent detection accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 is a schematic diagram of the magnetic sensor of the first embodiment of the present application and a diagram showing an example of an operation at the time of automatic correction.

[0049] Figure 2 is a diagram showing details of an automatic correction circuit of the magnetic sensor of Figure 1 and an example of an operation at the time of automatic correction.

[0050] Figure 3 is a diagram showingFigure 2 A diagram showing the details of the detection circuit of the magnetic sensor.

[0051] Figure 4 This is a flowchart illustrating the automatic calibration process of the magnetic sensor according to the first embodiment of the present invention.

[0052] Figure 5 This is a schematic diagram of a magnetic sensor according to the second embodiment of the present invention.

[0053] Figure 6 This is a flowchart illustrating the automatic calibration process of the magnetic sensor according to the second embodiment of the present invention.

[0054] Figure 7 This is a diagram illustrating a modified example of the magnetic sensor according to an embodiment of the present invention.

[0055] Figure 8 The figure shows other variations of the magnetic sensor according to embodiments of the present invention.

[0056] Figure 9 This is a schematic diagram of a biomagnetic measurement device according to an embodiment of the present invention. Detailed Implementation

[0057] "Magnetic sensor"

[0058] <First Implementation>

[0059] First, the magnetic sensor 10 of the first embodiment of the present invention will be described with reference to the accompanying drawings. It should be noted that, in the case of the same configuration, the same reference numerals may sometimes be used and the description may be omitted.

[0060] like Figure 1 As shown, the magnetic sensor 10 of the first embodiment of the present invention is characterized by comprising a magnetic sensor 20, a coil 30, a sampler 40, an amplifier circuit 50 (AMP), a detection circuit 60, an automatic calibration circuit 70, and a constant current source circuit 80.

[0061] Coil 30 is configured to generate an induced voltage Vi proportional to an external magnetic field. Sampler 40 is connected to coil 30 to perform peak sampling of the induced voltage Vi. Sampler 40 is connected to detection circuit 60 via amplifier circuit 50. Detection circuit 60 outputs an output signal OUT for displaying the sensing result of magnetic sensor 10 and peak sampling status information PS with timing information of when the induced voltage Vi generated in coil 30 reaches its peak value. Peak sampling status information PS and external clock CLK are input to automatic calibration circuit 70. Automatic calibration circuit 70 generates a magnetic sensor clock SMI for driving magnetic sensor 20 in synchronization with external clock CLK, and similarly generates a sampler clock SMPL for driving sampler 40 in synchronization with external clock CLK.

[0062] (auto-correction circuit)

[0063] As Figure 2 shown in the magnetic sensor 10 of the first embodiment of the present application, the auto-correction circuit 70 is provided with a logic circuit 71, a delay-locked loop circuit 72 (DLL), a multiplexer 73, and a clock generation circuit 74.

[0064] The auto-correction circuit 70 relatively adjusts the rising edge timing of the magnetic sensitive body clock SMI that drives the magnetic sensitive body 20 and the rising edge timing of the sampler clock SMPL that drives the sampler 40, based on the sampled voltage detected by the sampler 40.

[0065] Further, the auto-correction circuit 70 detects the delay time until the sampled voltage first becomes a peak value by observing the displacement of the sampled voltage from the magnetic sensitive body clock SMI rising for a prescribed period. Then, the auto-correction circuit 70 sets the rising edge timings of the magnetic sensitive body clock SMI and the sampler clock SMPL to be staggered by a time corresponding to the above-mentioned delay time.

[0066] The delay-locked loop circuit 72 has a plurality of delay elements 721 connected in cascade. The delay-locked loop circuit 72 that inputs the external clock CLK outputs signals having different delay amounts with respect to the external clock CLK through the plurality of delay elements 721 connected in cascade.

[0067] The logic circuit 71 is connected to the detection circuit 60 and the multiplexer 73. Each time the peak value sampling state information PS is input from the detection circuit 60, the logic circuit 71 outputs a selection signal Dctrl that selects any one of the outputs from the plurality of delay elements 721 to the multiplexer 73, causing the output timing of the sampler clock SMPL to change. The logic circuit 71 monitors the peak value sampling state information PS and records the selection signal Dctrl output at the timing when the induced voltage generated in the coil 30 becomes a peak value.

[0068] The multiplexer 73 selects any one of the respective outputs of the delay elements 721 according to the selection signal Dctrl, generating the sampler clock SMPL. The sampler clock SMPL can be a pulse current, a high-frequency current.

[0069] The clock generation circuit 74 is provided with a clock gen 741 and a drive circuit 742. The clock gen 741 that inputs the external clock CLK drives the drive circuit 742 to generate the magnetic sensitive body clock SMI that is synchronized with the external clock CLK. The magnetic sensitive body clock SMI can be a pulse current, a high-frequency current. The clock genThe external clock CLK of 741 is the same as the external clock CLK input to the above-mentioned delay synchronization circuit 72.

[0070] (detection circuit)

[0071] As Figure 3 shown in the magnetic sensor 10 of the first embodiment of the present application, the detection circuit 60 is provided with an analog-digital conversion circuit 61 (ADC). The analog-digital conversion circuit 61 converts the sampling voltage amplified by the amplification circuit 50 into peak sampling state information PS.

[0072] In the case where a digital output is required as the magnetic sensor 10 at the time of sensing operation, the above-mentioned analog-digital conversion circuit 61 can be used as it is as a circuit outputting a digital output signal OUT. Thus, as the detection circuit 60, it is not necessary to additionally add a circuit, and it is possible to further improve the detection accuracy without increasing the cost of the magnetic sensor 10.

[0073] (magnetic sensitive body)

[0074] As Figures 1-3 shown, the magnetic sensitive body 20 is connected to the clock generation circuit 74 of the automatic correction circuit 70. By the magnetic sensitive body clock SMI generated by the clock generation circuit 74, a current flows through the magnetic sensitive body 20. Thus, a magnetic impedance effect (MI effect) in which not only the inductance of the magnetic sensitive body 20 changes but also the resistance changes at the same time is generated.

[0075] The electromagnetic characteristics of the magnetic sensitive body 20 change by the action of an external magnetic field. As the magnetic sensitive body 20, a magnetic impedance element (MI element) can be cited. The material constituting the magnetic sensitive body 20 is not particularly limited as long as it has soft magnetic characteristics, and for example, an amorphous alloy composed of a known alloy system such as Co-Mn-Si-B system, Fe-Si system, etc. can be cited.

[0076] (coil)

[0077] As Figures 1-3 shown, the coil 30 is arranged so as to obtain an induced voltage V i in proportion to the generated external magnetic field by the magnetic sensitive body 20. It is preferable that the coil 30 is arranged close to the magnetic sensitive body 20 (wound around the magnetic sensitive body 20). Thus, it is easy to obtain an induced voltage V i in proportion to the generated external magnetic field by the magnetic sensitive body 20. The coil 30 can use a known component, and for example, can be composed of a wire.

[0078] (sampler)

[0079] As Figures 1-3As shown, the sampler 40 includes a switch 41 and a capacitor 42 connected in parallel to the coil 30. The sampler 40 samples the induced voltage Vi generated in the coil 30 to obtain a sampled voltage. The switch 41 is driven by a sampler clock SMPL generated by the automatic calibration circuit 70. The switch 41 and the capacitor 42 can use known components.

[0080] (Constant current source circuit)

[0081] like Figures 1-3 As shown, the constant current source circuit 80 is connected to the coil 30. The constant current source circuit 80 includes a reference voltage circuit 81 (VREF) and a resistor 82. The constant current source circuit 80 operates in a manner that provides a constant current to the magnetic sensor 20 to provide a constant DC magnetic field during automatic calibration. Furthermore, during normal operation, the constant current source circuit 80 is reconfigured to achieve strong negative feedback by allowing a current proportional to the output signal OUT to flow through the coil 30.

[0082] During automatic calibration, a current flows through coil 30 to generate a constant magnetic field stronger than the external magnetic field, thereby applying a constant, strong magnetic field to the magnetic sensor 20 that is independent of the strength of the external magnetic field. This minimizes the influence of the external magnetic field strength. As a result, the sensitivity (induced voltage V) during automatic calibration (scanning the selection signal Dctrl) is improved. i By maximizing the amplitude, more accurate detection and correction can be achieved.

[0083] (Modified Example)

[0084] like Figure 7 and Figure 8 As shown, in the magnetic sensor 10 of the present invention, the constant current source circuit 80 can also be reconfigured to provide strong negative feedback, with the resistor 82 shared in the magnetic sensor 20, the sampler 40, and the detection circuit 60. For example... Figure 8 As shown, during normal sensing, if the connection of the reference voltage circuit 81 is switched to the output signal OUT, the output of the digital-to-analog converter (DAC), then the resistor 82 can be shared in the magnetic sensor 20, the sampler 40, and the detection circuit 60. This saves resistor area and further reduces the cost of the magnetic sensor 10. The constant current source circuit 80 can also be a constant current source. Furthermore, the constant current source circuit 80 can be an open-loop circuit without using strong negative feedback (the path of the resistor).

[0085] (Amplifier circuit)

[0086] like Figures 1-3As shown, the amplifier circuit 50 (AMP) is connected between the sampler 40 and the detection circuit 60. The amplifier circuit 50 amplifies the sampled voltage obtained by the sampler 40, thus improving the detection accuracy of the detection circuit 60. Alternatively, during automatic calibration, with the strong negative feedback of the circuit forming a deactivated open loop, the output of the amplifier circuit 50 can be directly coupled to the detection circuit 60, thereby reusing the amplifier circuit 50 as a preamplifier for the detection circuit 60. This further improves the accuracy of the detection circuit 60 without increasing cost.

[0087] (Automatic calibration method)

[0088] The automatic calibration method of the magnetic sensor 10 according to the first embodiment of the present invention will be described.

[0089] like Figure 2 As shown, during automatic calibration, firstly, the magnetic sensor 20 is energized with a driving current using the magnetic sensor clock SMI. Consequently, an induced voltage V in coil 30, proportional to the magnetic field generated by the driving current flowing through the magnetic sensor 20, is obtained. i At this point, the magnitude of the induced voltage Vi generated in coil 30 becomes the maximum timing ratio, and the magnitude of the magnetic field generated by the current flowing through magnetor 20 becomes the maximum timing delay Δtopt.

[0090] Induced voltage V i The sampled voltage is sampled by sampler 40 and output to detection circuit 60 via amplifier circuit 50. Analog-to-digital converter 61 of detection circuit 60 converts the sampled voltage input via amplifier circuit 50 into peak sampling status information PS and outputs it. Peak sampling status information PS and external clock CLK are input to automatic correction circuit 70. Automatic correction circuit 70 then searches for, determines, and stores the delay amount Δtopt based on the peak sampling status information PS. Then, based on the determined delay amount Δtopt, it generates a magnetor clock SMI synchronized with the external clock and a sampler clock SMPL that is also synchronized with the external clock and enables sampler 40 to sample the peak value of the induced voltage Vi generated in coil 30.

[0091] like Figure 2 As shown, when the automatic correction circuit 70 is configured as described above, during automatic correction, the logic circuit 71 sequentially searches the selection signal Dctrl to determine whether the peak value of the induced voltage Vi has been sampled in the sampler 40. Then, the logic circuit 71 operates by saving the value of the selection signal Dctrl, which is the output of the optimal delay element 721.

[0092] Specifically, such as Figure 2 and Figure 4As shown, in the automatic correction, the logic circuit 71 of the magnetic sensor 10 of the first embodiment of the present application starts scanning for the selection signal Dctrl from the value at which the sampler clock SMPL becomes the minimum delay amount (selection signal DctrlO). Here, the minimum delay amount means the timing at which the peak of the induced voltage V i The timing of the sampling (t2) is delayed by the minimum amount with respect to the rising edge timing (tl) of the magnetic sensitive element clock SMI. Note that, in the case where the magnetic sensitive element clock SMI is high frequency, tl is the timing at which the rising edge of the magnetic sensitive element clock SMI first becomes a peak.

[0093] Then, the logic circuit 71 monotonously increases the selection signal Dctrl in order, thereby scanning the delay amount Δtopt of the sampler clock SMPL in synchronization with the external clock CLK. In the case where the absolute value of the peak sample state information PS (that is, |output signal OUT|) is above that of the peak sample state information PS one clock before, in each cycle of the external clock CLK, the logic circuit 71 monotonously increases the selection signal Dctrl to continue the scanning of the sampling timing. Then, the selection signal Dctrl set one clock before the timing at which the absolute value of the peak sample state information PS becomes reduced, in each cycle of the external clock, is set as the selection signal Dctrl n ) and the selection signal DctrlO. n－1 The sampling is performed, and the scanning of the sampling timing is ended. At this time, the time difference corresponding to the difference between the selection signal Dctrl n－1 and the selection signal DctrlO is the optimal delay amount Δtopt.

[0094] Here, the delay amount Δtopt means the delay amount of the timing (t3) of the peak of the induced voltage generated in the coil by the rising edge of the magnetic sensitive element clock SMI with respect to the rising edge timing (tl) of the magnetic sensitive element clock SMI.

[0095] Thus, the optimal delay amount Δtopt for sampling the peak of the induced voltage Vi generated in accordance with the external magnetic field can be automatically searched. As a result, the detection accuracy can be improved without increasing the cost of the magnetic sensor 10. Further, by using the delay synchronization circuit 72, the delay amount of each delay section of the plurality of delay elements 721 can be fixed with high accuracy regardless of the temporal change of the environment. Therefore, the optimal delay amount Δtopt can be stably held.

[0096] In ordinary sensing, the strong negative feedback control is performed in such a manner that the sampler clock SMPL synchronized with the magnetic sensitive element clock SMI and capable of causing the sampler 40 to sample the peak of the induced voltage generated in the coil 30 is generated using the above optimal delay amount Δtopt. Thus, the accuracy of the magnetic sensor 10 can be improved.

[0097] The detection circuit 60 can also operate in such a manner that it outputs the peak sampling state information PS in the automatic correction, and releases the connection for transmitting the peak sampling state information PS in the sensing operation, to obtain the digital output signal OUT from the detection circuit 60. Further, in the case where the digital output is required from the magnetic sensor 10 in the sensing operation, the above-described analog-digital conversion circuit 61 can also be used as the circuit for outputting the digital output signal OUT. Thus, as the detection circuit 60, it is not necessary to additionally add a circuit, and it is possible to further improve the detection accuracy without increasing the cost of the magnetic sensor 10.

[0098] (EFFECTS)

[0099] The resonance frequency of the ringing generated at both ends of the coil 30 at the time of the peak sampling is determined by the product of the coil 30 and the sampling parallel capacitor existing in parallel with the coil 30 and the installed parasitic capacitor. Therefore, there is a variation in the resonance frequency of the ringing in each device, but the resonance frequency of the ringing is substantially uniquely determined at the time of production, and has a feature that it is substantially not affected by environmental changes such as temperature.

[0100] Therefore, the magnetic sensor 10 according to the first embodiment of the present application, after the production of the device, determines and stores the amount of delay Δtopt of the timing of the peak of the induced voltage V i generated in the coil 30 by the rising edge of the magnetic sensitive body clock SMI and the timing of the rising edge of the peak sampler clock SMPL, and thereby can always perform the optimal peak sampling. As a result, it is possible to prevent the shift of the peak sampler clock SMPL due to the manufacturing variation, the environmental change, and the time-dependent degradation of the device, and the like. The amount of delay Δtopt is substantially not affected by the environmental change and the time-dependent degradation of the device, and thus it is possible to omit the manual adjustment. Therefore, even in the case where there is the environmental change and the manufacturing variation, it is possible to automatically correct the optimal sampling timing for the synchronous detection without increasing the cost. Thus, it is possible to reduce the workload of the manual correction, and it is possible to improve the accuracy of the magnetic sensor 10.

[0101] As described above, the magnetic sensor 10 according to the first embodiment of the present application can automatically correct the optimal sampling timing for the synchronous detection without increasing the cost even in the case where there is the environmental change and the manufacturing variation, and has an excellent detection accuracy.

[0102] <SECOND EMBODIMENT>

[0103] Next, the magnetic sensor 11 according to the second embodiment of the present application and the automatic correction method thereof will be described based on the drawings. Note that in the case where the same configuration as that of the above-described embodiment is used, the same reference numerals can be marked and the description can be omitted.

[0104] (Detection circuit)

[0105] like Figure 5 As shown, in the magnetic sensor 11 of the second embodiment of the present invention, the detection circuit 60a includes a comparator 61a, which outputs information binarized based on a predetermined threshold as peak sampling state information PS. For example, the comparator 61a may set a specific sampling voltage A as the threshold and output binarized signals for cases where the voltage is higher than the sampling voltage A and cases where the voltage is lower than the sampling voltage A as peak sampling state information PS. In the magnetic sensor 11 of the second embodiment of the present invention, the output signal OUT is the same as the sampling voltage amplified by the amplifier circuit 50.

[0106] like Figure 5 As shown, when an analog output is required for the magnetic sensor 11, only a comparator 61a needs to be added. Therefore, as the detection circuit 60a, there is no need to set up a separate analog-to-digital converter, which further reduces power consumption and cost.

[0107] In the magnetic sensor 11 of the second embodiment of the present invention, the configuration other than the detection circuit 60a is the same as that of the second embodiment.

[0108] (Automatic calibration method)

[0109] like Figure 6 As shown, in automatic calibration, logic circuit 71 scans the sampling timing starting from a value that makes the sampler clock SMPL reach its minimum delay, for the selection signal Dctrl. At this time, comparator 61a sets the sampled voltage obtained by sampler 40 at the value that makes the sampler clock SMPL reach its minimum delay (selection signal Dctrl0) as a threshold. Then, logic circuit 71 sequentially increases the selection signal Dctrl monotonically, thereby scanning the sampling timing synchronously with the external clock for the delay Δtopt of the sampler clock SMPL. The timing at which the two adjacent values ​​of the peak sampling state information PS reverse (comparator polarity reversal) according to each cycle of the external clock (selection signal Dctrl) is used to determine the timing. n The selection signal Dctrl n The nearest selection signal, half of the timing interval, is saved as the selection signal Dctrl, ending the sampling timing scan. At this point, the distance from the selection signal Dctrl... n The difference between the timing of the most recent selection signal and the selection signal Dctrl0 is the delay Δtopt.

[0110] Thus, the optimal delay amount Δtopt for sampling the peak value of the induced voltage Vi can be automatically searched for. As a result, the detection accuracy can be improved without increasing the cost of the magnetic sensor 11. Furthermore, by using the delay synchronization circuit 72, the delay amount of each delay section of the plurality of delay elements 721 can be fixed with high accuracy regardless of the temporal change in the environment. Thus, the optimal delay amount Δtopt can be stably held.

[0111] In ordinary sensing, the above-described optimal delay amount Δtopt is used to generate a sampler clock SMPL that is synchronized with the magnetic sensitive body clock SMI and enables the sampler 40 to sample the peak value of the induced voltage generated in the coil 30. On the other hand, by connecting in such a manner that a current proportional to the output signal OUT flows through the coil 30, strong negative feedback can be achieved while the loop gain is maximally maintained. Thus, the accuracy of the magnetic sensor 11 can be further improved. Figure 7

[0112] "Biological magnetic measurement device"

[0113] A biological magnetic measurement device according to an embodiment of the present application will be described.

[0114] As shown in FIG. 1, the biological magnetic measurement device 100 according to the embodiment of the present application includes a magnetic sensor 10, a control device 20, and a signal processing device 30. Figure 9 The biological magnetic measurement device 100 according to the embodiment of the present application can also include N (channels) of the above-described magnetic sensor, the control device, and the signal processing device. By N-channel simultaneous measurement achieved by the control device and processing in the signal processing device thereafter, a biomagnetic field measurement such as magnetoencephalography, magnetocardiography, and muography can be performed. The biological magnetic measurement device 100 can also be configured in pairs of a probe (array) including the magnetic sensor and a data acquisition system. Furthermore, the connection between the probe and the data acquisition system can be wired, wireless, or a combination thereof.

[0115] Thus, a high-resolution (pico Tesla class) biological magnetic measurement device that can stably operate can be implemented in a small and low-power-consumption manner. Therefore, without using the conventional magnetic sensor head (SQUID or the like) for biological magnetic measurement, a significant reduction in size and cost can be achieved.

[0116] ​As an example of the biological magnetic measurement device 100, there is no particular limitation, and examples include MEG (Magnetoencephalography), MNG (Magnetoneurography), MCG (Magnetocardiography), MMG (Magnetomyography), biological implanted brain activity measurement, etc.

[0117] Throughout the specification, when using "having" or "possessing" for a component having a certain part, this means that as long as there is no particularly contrary description, other components are not excluded, and other components may also be included.

[0118] In addition, the term "…… part" described in the specification refers to a unit that processes at least one function or action, which can be embodied as hardware or software, or as a combination of hardware and software.

[0119] In addition, within the scope not departing from the gist of the present invention, the components in the above-described embodiments can be appropriately replaced with well-known components, and in addition, the above-described modification examples can be appropriately combined.

[0120] Industrial Applicability

[0121] From the above, according to the present invention, a magnetic sensor and a biological magnetic measurement device can be provided. Even in the presence of environmental changes and manufacturing deviations, the magnetic sensor and the biological magnetic measurement device can automatically correct the optimal sampling timing for synchronous detection at low cost, and thus have high industrial utilization value.

[0122] Description of Reference Numerals [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​

[0133] 70: automatic correction circuit;

[0134] 71: logic circuit;

[0135] 72: delay synchronization circuit;

[0136] 721: delay element;

[0137] 73: multiplexer;

[0138] 74: clock generation circuit;

[0139] 741: clock gen;

[0140] 742: drive circuit;

[0141] 80: constant current source circuit;

[0142] 81: reference voltage circuit;

[0143] 82: resistor;

[0144] 83: digital-analog conversion circuit;

[0145] 100: living body magnetic measurement device.

Claims

1. A magnetic sensor, characterized by Possessing: a magnetic sensitive body, whose electromagnetic characteristics change by the action of an external magnetic field; a coil configured to obtain an induced voltage proportional to the external magnetic field; a sampler that samples the induced voltage generated in the coil to obtain a sampled voltage; and an automatic correction circuit that relatively adjusts the rising edge timing of a magnetic sensitive body clock that drives the magnetic sensitive body and the rising edge timing of a sampler clock that drives the sampler based on the sampled voltage, the automatic correction circuit detects a delay time until the sampled voltage first becomes a peak value by observing the displacement of the sampled voltage from the magnetic sensitive body clock rising for a prescribed period, and sets the rising edge timings of the magnetic sensitive body clock and the sampler clock to be staggered by a time corresponding to the delay time. The automatic correction circuit possesses:

2. The magnetic sensor of claim 1, wherein, a delay synchronization circuit having a plurality of delay elements connected in cascade; a logic circuit that outputs a selection signal Dctrl that selects any one of the outputs of the plurality of delay elements in the delay synchronization circuit each time the sampled voltage is input, and records the selection signal Dctrl output at the timing at which the induced voltage generated in the coil becomes a peak value; a multiplexer that selects any one of the respective outputs of the plurality of delay elements in the delay synchronization circuit according to the selection signal Dctrl, and generates the sampler clock; and a clock generation circuit that generates the magnetic sensitive body clock.

3. The magnetic sensor according to claim 1 or 2, further comprising a detection circuit that outputs peak sampling state information having information of the timing at which the induced voltage generated in the coil becomes a peak value based on the sampled voltage.

4. The magnetic sensor according to claim 3, wherein the detection circuit comprises an analog-digital conversion circuit, the analog-digital conversion circuit converts the sampled voltage into the peak sampling state information.

5. The magnetic sensor according to claim 3, wherein the detection circuit comprises a comparator, the comparator outputs information binarized based on a prescribed threshold value as the peak sampling state information.

6. The magnetic sensor according to claim 1 or 2, wherein a constant current source circuit is connected to the coil. Possessing: the magnetic sensor according to any one of claims 1 to 6; and a living body magnetic measurement unit that measures a magnetic emitted from a living body using an output signal from the magnetic sensor. ​ ​ ​ 7. A biological magnetic measurement device, characterized in that, ​ ​ ​

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