Signal injection device and impedance measurement device

Abstract

To provide a signal injection device capable of reliably injecting an AC signal to an injection target line in which a DC current is flowing.SOLUTION: Provided is a signal injection device 10 comprising an annular magnetic core 2 through which is inserted an injection target line L in which a DC current Ib is flowing, and a signal injection unit 3 for generating an AC signal S1 to be injected to the injection target line L and injecting it to the injection target line L. The signal injection device 10 includes a magnetic flux cancellation unit 4 for supplying a cancellation current Ic to a winding W1 for magnetic flux cancellation which is wound round the magnetic core 2, the cancellation current Ic generating a magnetic flux Md to cancel a magnetic flux Mb generated in the magnetic core 2 due to that the DC current Ib flows in the injection target line L that is inserted in the magnetic core 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a signal injection device capable of contactlessly injecting an AC signal into an injection target line made of a conductor, particularly to a signal injection device suitable for injecting an AC signal into an injection target line for supplying power through which a large DC current flows, and also to an impedance measurement device equipped with such a signal injection device for measuring the impedance of an object to be measured while an AC signal is flowing through the object to be measured. [Background technology]

[0002] As a signal injection device of this type, a signal injection / extraction device disclosed in the following Patent Document is known. In this signal injection / extraction device, a ferromagnetic material ( Magnetic Core ), and a first winding ( Signal injection winding ) and a second winding ( Magnetic flux cancellation winding ) and an amplifier circuit connected to the second winding. In this signal injection / extraction device, the amplifier circuit is configured to include a filter section that passes a current of the first frequency and blocks a signal current of the second frequency, an amplifier section that is arranged in series with the filter section, and an impedance element that is arranged in parallel with the filter section and the amplifier section.

[0003] In this signal injection / extraction device, a signal current having a second frequency of 1.7 MHz to 50 MHz, in particular 1.7 MHz to 30 MHz, is supplied to a first winding wound around a ferromagnetic material. When a high-current commercial AC current of 50 Hz or 60 Hz is flowing through the conductor, a large magnetic flux due to the commercial AC may be generated in the ferromagnetic material, causing magnetic saturation in the ferromagnetic material. In such a case, it becomes difficult to inject the signal current. Therefore, to suppress this magnetic saturation, this signal injection / extraction device passes a cancellation current through a second winding wound around the ferromagnetic material to cancel out the magnetic flux generated in the ferromagnetic material by the commercial AC.

[0004] In this case, when a signal current is injected into the first winding while a canceling current is flowing through the second winding, both magnetic flux caused by the supply of the signal current and magnetic flux caused by the flow of the canceling current are generated in the ferromagnetic material. Therefore, in this signal injection / extraction device, the second winding detects induced currents caused by both magnetic fluxes, and the filter section blocks the induced current caused by the signal current out of the induced current output from the second winding while allowing the induced current caused by the commercial AC to pass.

[0005] The amplifier circuit amplifies the induced current caused by the commercial AC output from the filter section and supplies a cancellation current to the second winding via the impedance element in a direction that cancels out the magnetic field generated by the commercial current. This efficiently cancels out the magnetic flux caused by the commercial AC of the first frequency applied to the conductor, but does little or nothing to cancel out the magnetic flux caused by the signal current of the second frequency. Therefore, this signal injection / extraction device can more reliably inject the signal current of the second frequency into a conductor through which the commercial AC of the first frequency flows. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4114615 (pages 3-7, Figure 1) Summary of the Invention [Problem to be solved by the invention]

[0007] However, the above-described signal injection and extraction device has the following problems. Specifically, for example, in a fuel cell vehicle (FCV), a battery consisting of multiple battery cells connected in series is connected to a power line (injection target line) through which a large DC current flows, and a large DC current flows from the battery through this power line. In such a situation, there is a demand for measuring the impedance of the battery as a whole and the impedance of each battery cell. To measure the impedance, an AC signal (for example, 100 Hz to 10 MHz, particularly 1 KHz to 10 KHz) for impedance measurement must be supplied to the battery. In this case, if a load is connected to the battery and a large DC current flows from the battery to the load, even if the above-described signal injection and extraction device is used to inject a measurement AC signal into the power line, the signal injection and extraction device can cancel out magnetic flux caused by commercial AC current flowing through a ferromagnetic material, but cannot cancel out magnetic flux generated in the ferromagnetic material due to the flow of DC current. Therefore, when a power line is inserted into a ferromagnetic material, the magnetic flux caused by the large DC current flowing through it causes the ferromagnetic material to become magnetically saturated, resulting in the problem that an AC signal cannot be injected into the power line.

[0008] The present invention has been made in consideration of these problems, and its main object is to provide a signal injection device that can reliably inject an AC signal into an injection target line through which a DC current is flowing, and an impedance measurement device that is equipped with such a signal injection device and can measure the impedance of an object to be measured. [Means for solving the problem]

[0010] To achieve the above objectives, Claim 1 The signal injection device described comprises: A signal injection device comprising: an annular magnetic core through which an injection target line through which a DC current flows is inserted; and a signal injection unit that generates an AC signal to be injected into the injection target line and injects the AC signal into the injection target line, wherein the signal injection device further comprises a magnetic flux cancellation unit that supplies a cancellation current to a first winding wound around the magnetic core, the cancellation current generating a second magnetic flux for canceling a first magnetic flux generated in the magnetic core due to the DC current flowing through the injection target line inserted through the magnetic core; The magnetic flux canceling unit , the above a first winding; Magnetic Core The relevant Magnetic Core a magnetic flux detection circuit that outputs a voltage signal corresponding to the magnetic flux generated in the first winding; an amplifier circuit that amplifies the voltage signal output from the magnetic flux detection circuit; and a cancel current that is supplied to the first winding in a direction that cancels the first magnetic flux by preventing the output of a voltage signal based on the AC signal included in the voltage signal amplified by the amplifier circuit and passing a voltage signal based on the DC current. First Winding and a filter circuit that blocks a voltage signal generated in the signal injection unit from being input to the amplifier circuit, and the signal injection unit includes a second winding wound around the magnetic core, and supplies the AC signal to the second winding to inject the AC signal into the injection target line. R .

[0011] Also, claims 2 The signal injection device described comprises: A signal injection device comprising: an annular magnetic core through which an injection target line through which a DC current flows is inserted; and a signal injection unit that generates an AC signal to be injected into the injection target line and injects the AC signal into the injection target line, wherein the signal injection device further comprises a magnetic flux cancellation unit that supplies a cancellation current to a first winding wound around the magnetic core, the cancellation current generating a second magnetic flux for canceling a first magnetic flux generated in the magnetic core due to the DC current flowing through the injection target line inserted through the magnetic core; The magnetic flux canceling unit , the above a first winding; Magnetic Core The relevant Magnetic Core a filter circuit that blocks the output of a voltage signal based on the AC signal included in the voltage signal output from the magnetic flux detection circuit and passes a voltage signal based on the DC current; an adder circuit that adds the voltage signal that has passed through the filter circuit and the AC signal to output a sum signal; and an amplifier circuit that amplifies the sum signal output from the adder circuit and supplies it to the first winding, supplies the cancel current to the first winding in a direction that cancels the first magnetic flux, and supplies the AC signal to the first winding to inject the AC signal into the injection target line.

[0012] Also, claims 3 The signal injection device described comprises: A signal injection device comprising: an annular magnetic core through which an injection target line through which a DC current flows is inserted; and a signal injection unit that generates an AC signal to be injected into the injection target line and injects the AC signal into the injection target line, wherein the signal injection device further comprises a magnetic flux cancellation unit that supplies a cancellation current to a first winding wound around the magnetic core, the cancellation current generating a second magnetic flux for canceling a first magnetic flux generated in the magnetic core due to the DC current flowing through the injection target line inserted through the magnetic core; The magnetic flux canceling unit , the above a first winding; Magnetic Core The relevant Magnetic Corea filter circuit that blocks the output of a voltage signal based on the AC signal included in the voltage signal output from the magnetic flux detection circuit and passes a voltage signal based on the DC current; and an amplifier circuit that amplifies the voltage signal that has passed through the filter circuit and supplies the cancellation current to one end of the first winding in a direction that cancels the first magnetic flux, and the signal injection unit includes an amplifier circuit that amplifies the AC signal and supplies the amplified AC signal to the other end of the first winding to inject the AC signal into the injection target line.

[0013] Also, claims 4 The signal injection device described comprises: A signal injection device comprising: an annular magnetic core through which an injection target line through which a DC current flows is inserted; and a signal injection unit that generates an AC signal to be injected into the injection target line and injects the AC signal into the injection target line, wherein the signal injection device further comprises a magnetic flux cancellation unit that supplies a cancellation current to a first winding wound around the magnetic core, the cancellation current generating a second magnetic flux for canceling a first magnetic flux generated in the magnetic core due to the DC current flowing through the injection target line inserted through the magnetic core; The magnetic flux canceling unit , the above a first winding; Magnetic Core The relevant Magnetic Core a filter circuit that blocks the output of a voltage signal based on the AC signal included in the voltage signal output from the magnetic flux detection circuit and passes a voltage signal based on the DC current; and a current driver that amplifies the voltage signal that has passed through the filter circuit and supplies the cancellation current to the first winding in a direction that cancels the first magnetic flux, and the signal injection unit has a second winding wound around the magnetic core and supplies the AC signal to the second winding to inject the AC signal into the injection target line.

[0014] Also, claims 5 The signal injection device according to claim 1 from 4 In the signal injection device described in any one of the above, the magnetic flux detection circuit is configured by arranging any one of a Hall element, a fluxgate sensor, and a GMR element in the magnetic core.

[0015] Also, claims 6 The signal injection device according to claim 1 ~ 5In the signal injection device described in any one of the above, the filter circuit is configured as a low-pass filter including an inductor formed by a reactor.

[0016] Also, claims 7 The signal injection device described a signal injection device comprising: an annular magnetic core through which an injection target line through which a DC current flows is inserted; and a signal injection unit that generates an AC signal to be injected into the injection target line and injects the AC signal into the injection target line, and a magnetic flux cancellation unit that supplies a cancellation current to a first winding wound around the magnetic core to generate a second magnetic flux for canceling a first magnetic flux generated in the magnetic core due to the DC current flowing through the injection target line inserted through the magnetic core; The magnetic flux canceling unit supplies the canceling current to the first winding, which reduces the signal level of a voltage signal corresponding to magnetic flux based on a frequency twice that of the AC signal generated in the magnetic core.

[0017] Also, claims 8 The signal injection device described a signal injection device comprising: an annular magnetic core through which an injection target line through which a DC current flows is inserted; and a signal injection unit that generates an AC signal to be injected into the injection target line and injects the AC signal into the injection target line, and a magnetic flux cancellation unit that supplies a cancellation current to a first winding wound around the magnetic core to generate a second magnetic flux for canceling a first magnetic flux generated in the magnetic core due to the DC current flowing through the injection target line inserted through the magnetic core; The signal injection unit generates the AC signal to be injected into the injection target line and a reference signal for synchronous detection having a frequency twice that of the AC signal, and the magnetic flux cancellation unit , the above The inverter comprises a first winding, a synchronous detection circuit that synchronously detects a voltage signal having twice the frequency of the AC signal generated in the first winding using the reference signal, a filter circuit that extracts a DC signal included in the output signal of the synchronous detection circuit, an adder circuit that adds the DC signal and the AC signal output from the filter circuit, and an amplifier circuit that amplifies the output signal of the adder circuit and supplies it to the first winding, supplies the cancel current to the first winding in a direction that cancels the first magnetic flux, and supplies the AC signal to the first winding to inject the AC signal into the injection target line. A signal injection device according to claim 9 includes an annular magnetic core through which a line to be injected with a direct current flows is inserted, and a signal injection unit that generates an alternating current signal to be injected into the line to be injected, and injects the signal into the line to be injected, the signal injection unit further including a magnetic flux cancellation unit that supplies a cancellation current to a first winding wound around the magnetic core to generate a second magnetic flux for canceling a first magnetic flux generated in the magnetic core due to the direct current flowing through the line to be injected, the signal injection unit generates the alternating current signal to be injected into the line to be injected and a reference signal for synchronous detection having a frequency twice that of the alternating current signal, and the magnetic flux cancellation unit cancels the first winding and the first winding. a synchronous detection circuit that synchronously detects, with the reference signal, a voltage signal having twice the frequency of the AC signal generated in the magnetic core; a filter circuit that extracts a DC signal included in the output signal of the synchronous detection circuit; an adder circuit that adds the DC signal and the AC signal output from the filter circuit; and an amplifier circuit that amplifies the output signal of the adder circuit and supplies it to the first winding, supplies the cancel current to the first winding in a direction that cancels the first magnetic flux, and supplies the AC signal to the first winding to inject the AC signal into the injection target line, and supplies the cancel current to the first winding to reduce the signal level of a voltage signal corresponding to a magnetic flux based on twice the frequency of the AC signal generated in the magnetic core. .

[0018] The signal injection device according to claim 10 is the signal injection device according to any one of claims 1 to 9, Signal injection part sweeps the frequency of the AC signal.

[0019] The impedance measuring device described in claim 11 is an impedance measuring device that includes a signal injection device described in any one of claims 1 to 10 and measures the impedance of a measurement object connected in series to the injection target line, and includes a processing unit that, when the AC signal is injected into the injection target line, measures the impedance of the measurement object based on the current value of the AC signal flowing through the injection target line and the voltage value generated in the measurement object.

[0020] The impedance measuring device of claim 12 is the impedance measuring device of claim 11, further comprising: a non-contact current sensor that detects the current of the AC signal flowing through the injection target line without contacting the injection target line and outputs a detection signal to the processing unit; and a voltage detection unit that detects the voltage across the object to be measured, wherein the voltage detection unit comprises a voltage detection circuit that contacts both ends of the object to be measured to detect a voltage signal across the end, and an isolation circuit that outputs the detected voltage signal across the object to the processing unit while being insulated from the object to be measured, and the processing unit receives the detection signal as the current value of the AC signal and receives the voltage signal across the object to be measured as the voltage value generated across the object to be measured.

[0021] The impedance measuring device according to claim 13 is the impedance measuring device according to claim 12, wherein the processing unit receives the AC signal and performs quadrature detection on the detection signal to obtain the corresponding The current value of the AC signal a first quadrature detection circuit for receiving the AC signal and performing quadrature detection on the voltage signal at both ends to generate an in-phase component and a quadrature component of the AC signal; the voltage value of the voltage signal between both ends a second quadrature detection circuit for generating an in-phase component and a quadrature component of the The current value of the AC signal and the in-phase and quadrature components output from the second quadrature detection circuit. The voltage value of the voltage signal between both ends and a calculation circuit that calculates the impedance of the object to be measured based on the in-phase and quadrature components of the signal. [Effects of the Invention]

[0022] Claim 1~4,7~9 In the described signal injection device, the magnetic flux cancellation unit supplies a cancellation current that generates a second magnetic flux in the magnetic core to a first winding wound around the magnetic core, thereby canceling the first magnetic flux generated in the magnetic core due to a DC current flowing in the injection target line inserted through the magnetic core. Therefore, with this signal injection device, it is possible to avoid magnetic saturation of the magnetic core caused by a large DC current flowing in the injection target line, and as a result, by supplying an AC signal to the second winding, it is possible to reliably generate a magnetic flux based on the AC signal in the magnetic core, and to reliably and efficiently inject the AC signal into the injection target line through which the DC current is flowing.

[0023] Also, claims 1 The described signal injection device includes a first winding and a second winding that are independent of each other, and the filter circuit of the magnetic flux cancellation unit blocks the output of a voltage signal based on an AC signal included in a voltage signal amplified by the amplifier circuit, while passing a voltage signal based on a DC current to supply a cancellation current to the first winding in a direction that cancels the first magnetic flux, and blocks the input of a voltage signal generated in the first winding based on the AC signal to the amplifier circuit. Therefore, with this signal injection device, magnetic saturation of the magnetic core caused by a large DC current flowing through the injection target line can be avoided, and by supplying an AC signal to the second winding, magnetic flux based on the AC signal can be reliably generated in the magnetic core, and the AC signal can be reliably and efficiently injected into the injection target line.

[0024] Also, claims 2In the described signal injection device, the amplifier circuit amplifies an added signal obtained by adding the voltage signal and the AC signal using the adder circuit and supplies the resulting signal to the first winding. The cancel current and an AC current based on the AC signal are added in the first winding, generating a second magnetic flux and a magnetic flux based on the AC signal in the magnetic core. This signal injection device thus avoids magnetic saturation in the magnetic core caused by a large DC current flowing through the injection target line. Supplying an AC signal (added signal) to the first winding reliably generates a magnetic flux based on the AC signal in the magnetic core, enabling the AC signal to be reliably and efficiently injected into the injection target line. Furthermore, this signal injection device uses a single first winding to function as both a cancel winding and a signal injection winding, allowing the signal injection device to be constructed inexpensively.

[0025] Also, claims 3 In the described signal injection device, the amplifier circuit supplies a cancellation current to one end of the first winding, and the amplifier circuit of the signal injection unit supplies the amplified AC signal to the other end of the first winding. The cancellation current and an AC current based on the AC signal are added together in the first winding, generating a second magnetic flux and a magnetic flux based on the AC signal in the magnetic core. This signal injection device thus avoids magnetic saturation in the magnetic core caused by a large DC current flowing through the injection target line. Supplying an AC signal to the first winding reliably generates a magnetic flux based on the AC signal in the magnetic core, enabling the AC signal to be reliably and efficiently injected into the injection target line. Furthermore, this signal injection device uses a single first winding to function as both a cancellation winding and a signal injection winding, allowing the signal injection device to be constructed inexpensively.

[0026] Also, claims 4In the described signal injection device, the current driver supplies a cancel current to the first winding while maintaining a high output impedance. In this case, the signal injection unit supplies an AC signal to the second winding, generating a magnetic flux in the magnetic core based on the AC signal. At this time, the AC current based on the generated magnetic flux attempts to flow through the first winding, but because the output impedance of the current driver is high, the AC current based on the magnetic flux does not flow from the first winding toward the output unit of the current driver. Therefore, the current driver does not supply a cancel current that would cancel the magnetic flux based on the AC signal generated in the magnetic core, but instead generates a cancel current that reduces the magnitude of the first magnetic flux detected by the magnetic flux detection circuit to zero and supplies it to the first winding. This signal injection device thus avoids magnetic saturation of the magnetic core due to a large DC current flowing through the signal injection line. Therefore, supplying an AC signal to the second winding reliably generates a magnetic flux based on the AC signal in the magnetic core, thereby enabling the AC signal to be reliably and efficiently injected into the signal injection line.

[0027] Also, claims 5 According to the described signal injection device, a magnetic flux detection circuit is configured by arranging any one of a Hall element, a fluxgate sensor, and a GMR element in a magnetic core, thereby making it possible to reliably detect the first magnetic flux despite a simple configuration.

[0028] Also, claims 6According to the described signal injection device, by configuring the filter circuit with a low-pass filter including an inductor formed by a reactor with large inductance, it is possible to bring the cutoff frequency as close to 0 Hz as possible, thereby allowing only voltage signals based on DC current to pass and enabling an inexpensive configuration. In particular, according to a signal injection device equipped with a filter circuit that has the function of blocking input of a voltage signal generated in a first winding based on an AC signal to an amplifier circuit, the filter circuit blocks input of a voltage signal generated in the first winding based on magnetic flux generated in the magnetic core by supplying an AC signal to the second winding to the amplifier circuit. This prevents a decrease in the level of the AC signal injected into the injection target line based on the magnetic flux generated by the magnetic core, thereby enabling reliable and efficient injection of the AC signal into the injection target line.

[0029] Also, claims 7 In the described signal injection device, the magnetic flux cancellation unit supplies a cancellation current to the first winding that reduces the signal level of a voltage signal corresponding to magnetic flux based on twice the frequency of the AC signal generated in the magnetic core, thereby making it possible to directly detect magnetic saturation in the magnetic core.As a result, magnetic flux based on the AC signal can be more reliably generated without causing magnetic saturation in the magnetic core, and the AC signal can be more reliably and efficiently injected into the injection target line.

[0030] Also, claims 8,In the signal injection device described in No. 9, the synchronous detection circuit synchronously detects a voltage signal having twice the frequency of the AC signal generated in the first winding using a reference signal, the adder circuit adds the DC signal and the AC signal included in the output signal of the synchronous detection circuit, and the amplifier circuit amplifies the added signal output from the adder circuit and supplies it to the first winding to supply a cancellation current to the first winding in a direction that cancels the first magnetic flux.This makes it possible to avoid magnetic saturation of the magnetic core caused by the large DC current flowing through the injection target line, and by supplying an AC signal to the first winding, magnetic flux based on the AC signal can be reliably generated in the magnetic core, allowing the AC signal to be reliably and efficiently injected into the injection target line.In addition, in this signal injection device, the magnetic flux cancellation unit as a whole is feedback-controlled to detect the magnitude of a harmonic signal having twice the frequency of the AC signal, which is a distortion signal of the AC signal generated in the magnetic core in a magnetically saturated state, and to reduce the distortion signal. Therefore, with this signal injection device, magnetic saturation of the magnetic core can be directly detected, and as a result, magnetic flux based on the AC signal can be more reliably generated without causing magnetic saturation in the magnetic core, and the AC signal can be more reliably and efficiently injected into the injection target line. Also, with this signal injection device, the function of the cancellation winding and the function of the signal injection winding can be realized using a single first winding, so the signal injection device can be configured inexpensively.

[0031] Furthermore, in the signal injection device described in claim 10, the signal injection unit sweeps the frequency of the AC signal, so that when the signal injection device is incorporated into an impedance measurement device, for example, it can be configured as an FRA that can supply an AC signal, which is a sinusoidal signal, to the object to be measured and measure its frequency response, thereby enabling high-precision impedance measurements.

[0032] Furthermore, in the impedance measuring device of claim 11, when the processing unit measures the impedance of the object to be measured that is connected in series to the injection target line, when an AC signal is injected into the injection target line, the processing unit measures the impedance of the object to be measured based on the current value of the AC signal flowing through the injection target line and the voltage value generated in the object to be measured.This makes it possible to more reliably generate magnetic flux based on the AC signal in the magnetic core, and more reliably and efficiently inject the AC signal into the injection target line, thereby making it possible to measure the impedance of the object to be measured with high accuracy.

[0033] In the impedance measuring device described in claim 12, a non-contact current sensor detects the AC current flowing through the injection target line without contacting the injection target line and outputs the detection signal to a processing unit, and a voltage detection unit contacts both ends of the measurement target and outputs a detected voltage signal across the measurement target to the processing unit while being insulated from the measurement target.This allows for accurate detection of the minute AC voltage generated within the measurement target when a current based on the injection of an AC signal flows through the measurement target, even if a very high voltage is generated in the measurement target or if noise such as switching noise is present around the load or the impedance measuring device.Therefore, this impedance measuring device can accurately measure the impedance of the measurement target.Furthermore, by using a non-contact current sensor, this impedance measuring device can measure the impedance of the measurement target without contacting the injection target line, without disconnecting the injection target line.

[0034] In the impedance measuring device according to claim 13, the arithmetic circuit of the processing unit receives the signal output from the first quadrature detection circuit. Current value of AC signal and the in-phase and quadrature components output from the second quadrature detection circuit. Voltage value of the voltage signal at both ends By calculating the impedance of the object to be measured based on the in-phase and quadrature components of the signal level (S / N), the ratio of the signal level (S) to the noise level (N) can be increased and the impedance can be measured with high accuracy, even when the signal level of the AC signal injected into the injection target line is small. [Brief explanation of the drawings]

[0035] [Figure 1] 1 is a diagram showing the configuration of an impedance measuring device 1. FIG. [Figure 2] 10 is a characteristic diagram showing the frequency characteristics of LPF 43 (a characteristic diagram showing the ability of magnetic flux cancellation unit 4 to cancel magnetic flux Mb generated in magnetic core 2). FIG. [Figure 3] FIG. 3 is a diagram showing the configuration of a magnetic flux canceling unit 4A. [Figure 4] FIG. 4 is a diagram showing the configuration of a magnetic flux canceling section 4B. [Figure 5] FIG. 4 is a diagram showing the configuration of a magnetic flux canceling unit 4C. [Figure 6] 3 is a diagram showing the configuration of a signal injection unit 3 and a magnetic flux cancellation unit 4D. FIG. [Figure 7] FIG. 10 is a diagram showing another configuration of the LPF 43. DETAILED DESCRIPTION OF THE INVENTION

[0036] Hereinafter, embodiments of a signal injection device and an impedance measurement device will be described with reference to the accompanying drawings.

[0037] 1 is an example of an "impedance measuring device" and is configured to be able to measure, for example, the internal impedance Zb of a battery Bat as a measurement target when a load Load is connected. The impedance measuring device 1 is also configured as an FRA (Frequency Response Analyzer) that can supply an AC signal S1, which is a sine wave signal (described below), to the battery Bat and measure its frequency response, thereby enabling highly accurate impedance measurement.

[0038] For example, in a fuel cell vehicle, a load Load that consumes a large current, such as a motor, and a battery Bat (shown as a single battery in the figure) consisting of multiple battery cells connected in series are connected by a power line (hereinafter also referred to as the "injection target line L") made of a conductor such as an insulated cable with an insulating core, an enameled wire, or an uninsulated electric wire, and a large DC current flows from the battery Bat to the load Load through this injection target line L. To measure the internal impedance Zb of the battery Bat in this connection state, it is necessary to supply an AC signal S1 (for example, 100 Hz to 10 MHz, particularly 1 kHz to 10 kHz) for impedance measurement to the battery Bat. In this case, the impedance measurement device 1 is configured to inject the AC signal S1 into the injection target line L through which the large DC current flows from the battery Bat to the load Load using an injection extraction device 10, which will be described later.

[0039] Specifically, the impedance measuring device 1 is configured to include a magnetic core 2, a signal injection unit 3, a magnetic flux cancellation unit 4, a non-contact current sensor 5, a voltage detection unit 6, a processing unit 7, and an output unit 8. In this case, the magnetic core 2, the signal injection unit 3, and the magnetic flux cancellation unit 4 form a "signal injection device 10."

[0040] The magnetic core 2 is formed using materials such as ferrite, permalloy, permendur, silicon steel, and pure iron in a circular, elliptical, rectangular, or polygonal shape so that the injection target line L, through which the DC current Ib flows, can be inserted. The magnetic core 2 is wound with a magnetic flux cancellation winding W1 as a first winding for supplying a negative feedback DC current (hereinafter also referred to as the "cancellation current Ic") as a cancellation current for magnetic flux cancellation, and a signal injection winding W2 as a second winding for injecting an AC signal S1. A Hall element 41 is disposed in a gap G between the magnetic flux cancellation winding W1 and the signal injection winding W2. The gap G prevents magnetic saturation of the magnetic core 2. The magnetic core 2 may also be configured as a separable clamp type. A signal is injected into one end of the magnetic flux cancellation winding W1 and the signal injection winding W2, and the other end is connected to a reference potential (floating ground) described below.

[0041] The signal injection unit 3 is configured to generate an AC signal S1 for measurement and to be able to inject the AC signal S1 into the injection target line L (to the core wire (conductor) of the injection target line L) in a non-contact manner. Specifically, the signal injection unit 3 is configured to include a signal generation circuit 31 that is configured to generate the AC signal S1, which is a sine wave signal for measuring the internal impedance Zb of the battery Bat, and to be able to class-D amplify and output the AC signal S1 using a class-D amplifier circuit arranged in an output stage, and the signal injection winding W2 described above. In this signal injection unit 3, the signal generation circuit 31 controls the signal level and frequency of the AC signal S1 to be injected into the injection target line L by a control signal Sc1 output from the processing unit 7, sweeping the frequency (for example, 1 KHz to 10 KHz), and outputs the generated AC signal S1 to the processing unit 7 and class-D amplifies it before supplying it to the signal injection winding W2. In this case, the AC signal S1 is supplied to the signal injection winding W2 using a transformer method (the signal injection winding W2 is a primary winding with multiple turns and the injection target line L is a secondary winding with one turn) (i.e., the AC signal S1 is applied to both ends of the signal injection winding W2), so that an AC current Iac based on the AC signal S1 flows through the signal injection winding W2, and a magnetic flux Mc based on the AC signal S1 is generated in the magnetic core 2 in the direction shown in Fig. 1, and an injection current Ii, which is an AC signal with a current value corresponding to the magnitude of the magnetic flux Mc, is supplied (injected) as a normal mode signal to the injection target line L. Note that sweeping of the frequency by the signal generation circuit 31 is not essential, and if sweeping is not necessary, a configuration that generates an AC signal S1 of a fixed frequency can be applied to the signal generation circuit 31.

[0042] The magnetic flux cancellation unit 4 is configured to be able to cancel (offset) the magnetic flux Mb as a first magnetic flux generated in the magnetic core 2 in the direction shown in Fig. 1 when a DC current Ib flows through the injection target line L by generating a magnetic flux Md as a second magnetic flux in the opposite direction to the magnetic flux Mb in the magnetic core 2 by the zero flux method. Specifically, the magnetic flux cancellation unit 4 includes a Hall element 41 as an example of a magnetic flux detection circuit disposed in the gap G, a voltage driver 42, a low pass filter 43 (hereinafter also referred to as "LPF 43"), and Magnetic flux cancellation winding W1 The device is configured with the following:

[0043] The Hall element 41 is an example of a "magnetic flux detection circuit" and is provided in the magnetic core 2. Magnetic Core 2, and outputs a voltage signal S2 corresponding to the magnetic flux generated in the magnetic core 2. In this case, a configuration in which a current signal is output as a detection signal from the Hall element 41 may be adopted, and a signal converted from such a current signal into a voltage signal is also included in the "voltage signal S2." Note that the "magnetic flux detection circuit" is not limited to a Hall element, and can also be configured by arranging a fluxgate sensor or a magnetoresistive element (MR: Magneto Resistive) in the magnetic core 2. Furthermore, the magnetoresistive element can be a GMR element (Giant Magneto Resistive), a semiconductor magnetoresistive element (SMR), an anisotropic magnetoresistive element (AMR: Anisotropic Magneto Resistive) using a ferromagnetic thin film material, a giant magnetoresistive element (GMR: Giant Magneto Resistive), or a tunnel magnetoresistive element (TMR: Tunnel Magneto Resistive).

[0044] The voltage driver 42 is an example of an amplifier circuit that functions as a negative feedback amplifier circuit as a whole, and amplifies the voltage signal S2 and outputs it at low impedance to the LPF 43. The LPF 43 is an example of a filter circuit, and prevents the output of a voltage signal S2 based on the AC signal S1 included in the voltage signal S2 amplified by the voltage driver 42, and passes the voltage signal S2 based on the DC current Ib, thereby supplying a cancellation current Ic to the magnetic flux cancellation winding W1 in a direction that cancels the magnetic flux Mb, and also generates a voltage signal (based on the AC signal) in the magnetic flux cancellation winding W1 based on the magnetic flux Mc generated in the magnetic core 2 by supplying the AC signal S1 to the signal injection winding W2. First Winding1, LPF 43 is configured as an L-type LC filter in which, for example, a capacitor C1 is connected between an input terminal Ti on the voltage driver 42 side and a reference potential, and an inductor L1 is connected between the input terminal Ti and an output terminal To on the magnetic flux cancellation winding W1 side, and as shown in FIG. 2, it has frequency characteristics in which its cutoff frequency is lower than the frequency of AC signal S1 (the lowest frequency of AC signal S1 when frequency sweeping is being performed), and it blocks the output of voltage signal S2 based on AC signal S1 and passes voltage signal S2 based on DC current Ib.

[0045] In this case, to pass only the voltage signal S2 based on the DC current Ib, it is preferable that the cutoff frequency be as close to 0 Hz as possible. Therefore, the magnetic flux cancellation unit 4 includes a filter circuit, for example, an LPF 43 including an inductor formed by a reactor with a large inductance. Therefore, the LPF 43 has a cutoff frequency as close to 0 Hz as possible, which prevents the output of the voltage signal S2 based on the AC signal S1 and allows only the voltage signal S2 based on the DC current Ib to pass, thereby supplying the cancellation current Ic to the flux cancellation winding W1 in a direction that cancels the magnetic flux Mb. Furthermore, the supply of the AC signal S1 to the signal injection winding W2 prevents the voltage signal generated in the flux cancellation winding W1 based on the magnetic flux Mc generated in the magnetic core 2 from being input to the voltage driver 42. This prevents a decrease in the level of the injection current Ii (AC signal S1) injected into the injection target line L based on the magnetic flux Mc generated in the magnetic core 2. The LPF 43 can be configured as a low-pass filter of various configurations other than the L-type LC filter shown in FIG. 1. For example, as shown in FIG. 7, the LPF 43 may be configured as a T-type LC filter in which the inductor L1 and a low-inductance inductor L2 are connected in series between the input terminal Ti and the output terminal To, and the capacitor C1 is connected between the junction of the inductors L2 and L1 and a reference potential. Although not shown, the LPF 43 may also be configured as a π-type LC filter. Furthermore, the LPFs 43 in the magnetic flux cancellation units 4A, 4B, and 4C described below and the LPF 48 in the magnetic flux cancellation unit 4D do not require the function of preventing a decrease in the level of the injected current Ii. Therefore, a low-inductance inductor can be used for the internal inductor L1, rather than a high-inductance reactor. Furthermore, the configuration of the LPF 43 in each of the magnetic flux cancellation units 4, 4A, 4B, and 4C and the LPF 48 in the magnetic flux cancellation unit 4D is not limited to LC-type low-pass filters such as L-type, T-type, and π-type, but various types of low-pass filters can be used, such as RC-type low-pass filters such as L-type, T-type, and π-type that use resistors instead of inductors.Furthermore, the frequency characteristics of the LPF 43 coincide with the frequency characteristics that indicate the ability of the magnetic flux cancellation unit 4 to cancel the magnetic flux generated in the magnetic core 2.

[0046] Furthermore, the direction of the flow of the cancel current Ic and the winding direction of the magnetic flux canceling winding W1 are preset so that the flow of DC current Ib supplied from battery Bat to load Load generates magnetic flux Md in a direction that reduces magnetic flux Mb generated in magnetic core 2. Therefore, the voltage driver 42 of the magnetic flux canceling unit 4 generates a voltage signal S2 (cancellation current Ic) that reduces the magnitude of magnetic flux Mb detected by the Hall element 41 to zero, and supplies this to the magnetic flux canceling winding W1 wound around the magnetic core 2, thereby avoiding magnetic saturation of the magnetic core 2 caused by the large DC current Ib flowing through the injection target line L. As a result, by supplying an AC signal S1 to the signal injection winding W2, magnetic flux Mc is reliably generated in the magnetic core 2, and the AC signal S1 is reliably injected into the injection target line L.

[0047] The non-contact current sensor 5 is a so-called clamp-type current sensor that detects the injection current Ii, which is an AC current flowing through the injection target line L (core wire (conductor) of the injection target line L), without contacting the injection target line L, and outputs a detection signal S3 indicating the current value of the injection current Ii to the processing unit 7.

[0048] The voltage detection unit 6 includes a pair of contact-type probes P1 and P2, a buffer circuit 61, and an isolation circuit 62, and detects the voltage across the battery Bat and outputs a voltage signal S4 across the battery Bat to the processing unit 7. In this case, the buffer circuit 61 is an example of a voltage detection circuit, and includes coupling capacitors at each of a pair of input sections that block the input of DC voltages and allow the input of AC voltages. The buffer circuit 61 generates a differential voltage of the AC voltages detected by the probes P1 and P2 and outputs a voltage signal S4 across the battery Bat. The isolation circuit 62 isolates the reference potential (ground) of the circuit including the load Load, the battery Bat, and the buffer circuit 61 from the reference potential (floating ground) of the impedance measurement device 1 excluding the buffer circuit 61, and outputs the voltage signal S4 across the battery Bat in an isolated state to the processing unit 7.

[0049] The processing unit 7 is, for example, configured with a CPU and equipped with A / D conversion circuits 71-73, a phase shift circuit 74, quadrature detection circuits 75 and 76, an arithmetic circuit 77, and an internal memory 78. The processing unit 7 receives the detection signal S3 and the end-to-end voltage signal S4 and measures the internal impedance Zb of the battery Bat, which is the measurement target, based on the detection signal S3 and the end-to-end voltage signal S4. The A / D conversion circuit 71 receives the AC signal S1 output from the signal generation circuit 31, performs A / D conversion (analog-to-digital conversion), and outputs signal data D11 (sinωt) indicating the voltage value, frequency, and phase of the sinusoidal AC signal S1 to the phase shift circuit 74 and the quadrature detection circuits 75 and 76. The A / D conversion circuit 72 receives the detection signal S3 output from the non-contact current sensor 5, performs A / D conversion, and outputs signal data D12 indicating the current value, frequency, and phase of the detection signal S3 (injection current Ii) to the quadrature detection circuit 75. The A / D conversion circuit 73 receives the voltage signal S4 output from the isolation circuit 62, performs A / D conversion, and outputs signal data D13 indicating the voltage value, frequency, and phase of the voltage signal S4 to the quadrature detection circuit .

[0050] The phase-shift circuit 74 receives the signal data D11(sinωt) output from the A / D conversion circuit 71, shifts the phase of the AC signal S1, which is a sine wave signal indicated by the signal data D11, by 90° to generate a cosine wave signal, and also generates signal data D11(cosωt) indicating the current value, frequency, and phase of the cosine wave signal and outputs it to the quadrature detection circuits 75 and 76. The quadrature detection circuit 75 receives signal data D12 indicating the detection signal S3 (AC value of the injection current Ii) output from the A / D conversion circuit 72, and performs quadrature detection on the signal data D12 using signal data D11 (sinωt) indicating the sine wave AC signal S1 output from the A / D conversion circuit 71 and signal data D11 (cosωt) indicating the cosine wave AC signal S1 output from the phase shift circuit 74. The quadrature detection circuit 75 generates current data Di indicating the in-phase component (I component: In-phase component) and quadrature component (Q component: Quadrature component) of the current value of the injection current Ii as complex numbers and outputs the current data Di to the arithmetic circuit 77. The quadrature detection circuit 76 receives signal data D13 indicating the end-to-end voltage signal S4 (the voltage value of the AC voltage generated across the battery Bat due to the injection current Ii flowing) output from the A / D conversion circuit 73, and performs quadrature detection on the signal data D13 using signal data D11 (sinωt) indicating the sine wave AC signal S1 output from the A / D conversion circuit 71 and signal data D11 (cosωt) indicating the cosine wave AC signal S1 output from the phase shift circuit 74. The quadrature detection circuit 76 generates voltage data Dv indicating the in-phase component (I component: In-phase component) and quadrature component (Q component: Quadrature component) of the voltage value of the end-to-end voltage signal S4 as complex numbers and outputs the voltage data Dv to the arithmetic circuit 77.

[0051] The arithmetic circuit 77 receives the current data Di output from the quadrature detection circuit 75 and the voltage data Dv output from the quadrature detection circuit 76, and calculates the internal impedance Zb of the battery Bat based on the current data Di and the voltage data Dv. The arithmetic circuit 77 outputs impedance data Dz indicating the internal impedance Zb of the battery Bat as the calculation result to the internal memory 78 for storage and also outputs the data to the output unit 8. The arithmetic circuit 77 also outputs a control signal Sc1 to the signal injection unit 3 to control the signal level of the AC signal S1 output from the signal injection unit 3 (signal generation circuit 31) so that the current value of the injection current Ii detected by the non-contact current sensor 5 falls within a target current value range (e.g., 1 mA ± 0.1 mA) required for impedance measurement. Specifically, the arithmetic circuit 77 monitors the current value (signal level of the AC signal S1) of the injection current Ii injected into the injection target line L based on the input current data Di (which may be signal data D12 output from the A / D conversion circuit 72), and controls the signal level of the AC signal S1 output from the signal injection unit 3 by outputting a control signal Sc1. The internal memory 78 is composed of a semiconductor memory, a hard disk drive, or the like, and stores the impedance data Dz, etc.

[0052] The output unit 8 is configured, for example, by a display device such as a liquid crystal panel or an organic EL panel, and receives the impedance data Dz output from the processing unit 7 to display the internal impedance Zb of the battery Bat on the screen. Note that instead of a display device, the output unit 8 may be configured by an interface device that performs data communication with an external device and outputs the impedance data Dz to this external device.

[0053] Next, a measurement method for measuring the internal impedance Zb of the battery Bat as a measurement target using the impedance measuring device 1 will be described with reference to the accompanying drawings.

[0054] First, the battery Bat and the load Load are connected by the injection target line L. When the load Load is activated in this state, a large DC current Ib flows from the battery Bat to the load Load via the injection target line L. In this state, the non-contact current sensor 5 is clamped to the injection target line L, and the probes P1 and P2 are brought into contact with both ends of the battery Bat.

[0055] Next, a measurement start switch (not shown) is operated. This causes the processing unit 7 to control the signal generation circuit 31 to generate an AC signal S1. The signal generation circuit 31 generates the AC signal S1 while sweeping the frequency, outputs the generated AC signal S1 to the processing unit 7, and supplies the class-D amplified AC signal S1 to the signal injection winding W2. In this case, supplying the AC signal S1 to the signal injection winding W2 causes an AC current Iac to flow through the signal injection winding W2. A magnetic flux Mc based on the AC signal S1 is generated in the magnetic core 2 in the direction shown in FIG. 1. An injection current Ii, an AC signal with a current value corresponding to the magnitude of the magnetic flux Mc, is injected into the injection target line L. Therefore, the AC signal S1 is injected into the injection target line L via the signal injection winding W2 without contacting the core wire of the injection target line L.

[0056] When a direct current Ib flows through the magnetic core 2, the magnetic flux cancellation unit 4 generates a magnetic flux Mb as a first magnetic flux in the direction shown in FIG. 1 in the magnetic core 2, and cancels this by generating a magnetic flux Md as a second magnetic flux in the opposite direction to the magnetic flux Mb in the magnetic core 2 by the zero flux method. Specifically, the Hall element 41 Magnetic CoreThe voltage driver 42 outputs a voltage signal S2 corresponding to the magnetic flux generated in the magnetic core 2 to the voltage driver 42. Next, the voltage driver 42 amplifies the voltage signal S2 and outputs it with low impedance to the LPF 43. The LPF 43 blocks the output of a voltage signal S2 (voltage signal S2 based on magnetic flux Mc) based on the AC signal S1 included in the voltage signal S2 amplified by the voltage driver 42, and passes the voltage signal S2 based on the DC current Ib to supply a cancellation current Ic to the magnetic flux cancellation winding W1 in a direction that cancels the magnetic flux Mb, and also blocks the input of a voltage signal generated in the magnetic flux cancellation winding W1 due to the AC signal S1 being supplied to the signal injection winding W2 to the voltage driver 42. Therefore, the voltage driver 42 does not pass a cancellation current that attempts to cancel the magnetic flux Mc generated in the magnetic core 2 based on the AC signal S1, and generates and supplies the cancellation current Ic to the magnetic flux cancellation winding W1 so that the magnitude of the magnetic flux Mb detected by the Hall element 41 becomes zero. This prevents magnetic saturation of the magnetic core 2, which would be caused by a large DC current Ib flowing through the injection target line L. Furthermore, the LPF 43 blocks input to the voltage driver 42 of a voltage signal generated in the magnetic flux cancellation winding W1 based on the magnetic flux Mc generated in the magnetic core 2 by supplying the AC signal S1 to the signal injection winding W2, thereby preventing a decrease in the level of the injection current Ii (AC signal S1) that is injected into the injection target line L based on the magnetic flux Mc generated in the magnetic core 2. As a result, supplying the AC signal S1 to the signal injection winding W2 reliably generates the magnetic flux Mc in the magnetic core 2, and the AC signal S1 is injected into the injection target line L reliably and efficiently.

[0057] On the other hand, when an AC signal S1 is injected into the injection target line L and a DC current Ib is flowing, the non-contact current sensor 5 detects the injection current Ii flowing through the injection target line L without contacting the injection target line L, and outputs a detection signal S3 indicating the current value to the processing unit 7.

[0058] Furthermore, the buffer circuit 61 of the voltage detection unit 6 inputs the voltage across the battery Bat via a pair of probes P1 and P2 and outputs a voltage signal S4, which is a differential voltage of the AC voltage, to the isolation circuit 62. In this case, because the buffer circuit 61 is equipped with a coupling capacitor at the pair of inputs, it generates only the differential voltage of the AC voltage detected by the probes P1 and P2 and outputs the voltage signal S4 as the voltage across the battery Bat. Next, the isolation circuit 62 outputs the voltage signal S4 to the processing unit 7. At this time, the isolation circuit 62 outputs the voltage signal S4 to the processing unit 7 while isolating the reference potential (ground) on the load Load and battery Bat side from the reference potential (floating ground) of the impedance measurement device 1. As a result, by outputting the voltage signal S4 to the impedance measurement device 1 via the isolation circuit 62, it is possible to accurately detect the minute AC voltage generated within the battery Bat when the AC signal S1 flows through the battery Bat, even if the output voltage of the battery Bat is very high.

[0059] Meanwhile, in the processing unit 7, the A / D conversion circuit 71 receives the AC signal S1 and performs A / D conversion to output signal data D11 (sinωt) indicating the voltage value, frequency, and phase of the sinusoidal AC signal S1 to the phase shift circuit 74 and the quadrature detection circuits 75 and 76. The A / D conversion circuit 72 receives the detection signal S3 and performs A / D conversion to output signal data D12 indicating the current value, frequency, and phase of the detection signal S3 to the quadrature detection circuit 75. The A / D conversion circuit 73 receives the end-to-end voltage signal S4 and performs A / D conversion to output signal data D12 indicating the voltage value, frequency, and phase of the end-to-end voltage signal S4 to the quadrature detection circuit 76. Furthermore, the phase-shift circuit 74 receives signal data D11, shifts the phase of the AC signal S1, which is a sine wave signal indicated by the signal data D11, by 90° to generate a cosine wave signal, and generates signal data D11(cosωt) indicating the current value, frequency, and phase of the cosine wave signal, and outputs the signal data D11(cosωt) to the quadrature detection circuits 75 and 76.

[0060] The quadrature detection circuit 75 also receives signal data D12 indicating the detection signal S3, and performs quadrature detection on the signal data D12 using signal data D11(sinωt) indicating the sine wave AC signal S1 and signal data D11(cosωt) indicating the cosine wave AC signal S1 to generate current data Di indicating the in-phase and quadrature components of the current value of the injection current Ii as complex numbers, and outputs this to the arithmetic circuit 77. The quadrature detection circuit 76 also receives signal data D13 indicating the end-to-end voltage signal S4, and performs quadrature detection on the signal data D13 using the signal data D11(sinωt) and signal data D11(cosωt) to generate voltage data Dv indicating the in-phase and quadrature components of the voltage value of the end-to-end voltage signal S4 as complex numbers, and outputs this to the arithmetic circuit 77. Next, the calculation circuit 77 inputs the current data Di and voltage data Dv, calculates the internal impedance Zb of the battery Bat based on the current data Di and voltage data Dv, and outputs impedance data Dz to the internal memory 78 for storage, as well as to the output unit 8. At this time, the output unit 8 inputs the impedance data Dz and displays the internal impedance Zb of the battery Bat on the screen of the display device. Note that the calculation circuit 77 can also display the frequency characteristics of the internal impedance Zb of the battery Bat relative to the frequency of the AC signal S1 on the screen of the display device by including frequency information of the AC signal S1 in the impedance data Dz. Furthermore, the calculation circuit 77 generates current value information of the DC current Ib flowing through the injection target line L based on the input current data Di (which may be signal data D12 output from the A / D conversion circuit 72), and can display the characteristics of the internal impedance Zb of the battery Bat relative to the current value of the DC current Ib on the screen of the display device by including the current value information in the impedance data Dz.

[0061] Furthermore, the arithmetic circuit 77 monitors the current value of the injection current Ii being injected into the injection target line L based on the input current data Di (which may be the signal data D12 output from the A / D conversion circuit 72), and outputs a control signal Sc1 to control the signal level of the AC signal S1 output from the signal injection unit 3 so that the current value of the injection current Ii detected by the non-contact current sensor 5 falls within the target current value range required for impedance measurement. As a result, the injection current Ii falls within the target current value range, and the ratio (S / N) of the signal level (S) to the noise level (N) of the detection signal S3 and the end-to-end voltage signal S4 can be increased, resulting in accurate measurement of the internal impedance Zb in the calculation process (measurement process) of the internal impedance Zb performed by the arithmetic circuit 77. This completes the measurement of the internal impedance Zb of the battery Bat by the impedance measuring device 1.

[0062] In this manner, in the signal injection device 10, the magnetic flux cancellation unit 4 supplies the cancellation current Ic, which generates the magnetic flux Md in the magnetic core 2, to the magnetic flux cancellation winding W1 wound around the magnetic core 2, thereby canceling the magnetic flux Mb generated in the magnetic core 2 due to the DC current Ib flowing in the injection target line L inserted through the magnetic core 2. Therefore, with this signal injection device 10, it is possible to avoid magnetic saturation of the magnetic core 2, which would be caused by a large DC current Ib flowing in the injection target line L, and as a result, by supplying the AC signal S1 to the signal injection winding W2, it is possible to reliably generate the magnetic flux Mc in the magnetic core 2 and reliably and efficiently inject the AC signal S1 into the injection target line L through which the DC current Ib is flowing.

[0063] Furthermore, this signal injection device 10 includes separate and independent magnetic flux canceling windings W1 and W2, and the LPF 43 of the magnetic flux canceling section 4 blocks the output of a voltage signal S2 based on the AC signal S1 included in the voltage signal S2 amplified by the voltage driver 42, while passing the voltage signal S2 based on the DC current Ib to supply a cancellation current Ic to the magnetic flux canceling winding W1 in a direction that cancels the magnetic flux Mb, and blocks the input to the voltage driver 42 of a voltage signal generated in the magnetic flux canceling winding W1 based on the AC signal S1. Therefore, this signal injection device 10 can avoid magnetic saturation of the magnetic core 2 caused by a large DC current Ib flowing through the injection target line L, and as a result, supplying the AC signal S1 to the signal injection winding W2 reliably generates a magnetic flux Mc in the magnetic core 2, making it possible to inject the AC signal S1 reliably and efficiently into the injection target line L.

[0064] The configuration of the "signal injection device" and the configuration of the "impedance measurement device" are not limited to the example of the impedance measurement device 1 described above. For example, the configuration shown in FIG. 3 can be adopted for the magnetic flux cancellation unit 4. In the configuration described below, components having the same functions as the components in the impedance measurement device 1 described above are assigned the same reference numerals, and duplicated explanations will be omitted.

[0065] The magnetic flux cancellation unit 4A shown in FIG. 3 is configured with a Hall element 41, a magnetic flux cancellation winding W1, an LPF 43, an adder circuit 44, and a voltage driver 42. In this case, one magnetic flux cancellation winding W1 functions as both a cancellation winding and a signal injection winding. The LPF 43 is an example of a filter circuit and has frequency characteristics similar to those of the LPF 43 of the magnetic flux cancellation unit 4. It blocks the output of a voltage signal S2 based on the AC signal S1 included in the voltage signal S2 output from the Hall element 41 and passes a voltage signal S2 based on the DC current Ib. The adder circuit 44 adds the voltage signal S2 that has passed through the LPF 43 and the AC signal S1 to generate and output a sum signal Sa. The voltage driver 42 amplifies the addition signal Sa output from the addition circuit 44 and supplies it to the magnetic flux cancellation winding W1, supplies a cancellation current Ic to the magnetic flux cancellation winding W1 in a direction that cancels the magnetic flux Mb, and also supplies an AC signal S1 (AC current Iac) to the magnetic flux cancellation winding W1, thereby injecting the AC signal S1 into the injection target line L.

[0066] In this signal injection device 10, the voltage driver 42 amplifies the sum signal Sa, which is obtained by adding the voltage signal S2 and the AC signal S1 together using the adder circuit 44, and supplies the amplified sum signal Sa to the flux cancellation winding W1. As a result, the cancellation current Ic and the AC current Iac are added together in the flux cancellation winding W1, generating magnetic fluxes Md and Mc in the magnetic core 2. Therefore, this signal injection device 10 can avoid magnetic saturation of the magnetic core 2, which would be caused by a large DC current Ib flowing through the injection target line L. As a result, supplying the AC signal S1 (sum signal Sa) to the flux cancellation winding W1 reliably generates magnetic flux Mc in the magnetic core 2, and the AC signal S1 can be reliably and efficiently injected into the injection target line L. Furthermore, this signal injection device 10 can use a single flux cancellation winding W1 to function as both a cancellation winding and a signal injection winding, allowing the signal injection device 10 to be configured inexpensively.

[0067] The magnetic flux cancellation unit 4B shown in FIG. 4 is configured with a Hall element 41, a magnetic flux cancellation winding W1, an LPF 43, and a voltage driver 42. The signal injection unit 3A includes a voltage driver 32 in addition to the components of the signal injection unit 3. In this case, one magnetic flux cancellation winding W1 functions as both a cancellation winding and a signal injection winding. The LPF 43 is an example of a filter circuit and has frequency characteristics similar to those of the LPF 43 of the magnetic flux cancellation unit 4. It blocks the output of a voltage signal S2 based on the AC signal S1 included in the voltage signal S2 output from the Hall element 41 and passes a voltage signal S2 based on the DC current Ib. The voltage driver 42 amplifies the voltage signal S2 that has passed through the LPF 43 and supplies a cancellation current Ic to one end T1 of the magnetic flux cancellation winding W1 in a direction that cancels the magnetic flux Mb. Furthermore, the voltage driver 32 amplifies the AC signal S1 and supplies the amplified AC signal S1 (AC current Iac) to the other end T2 of the magnetic flux cancellation winding W1, thereby injecting the AC signal S1 into the injection target line L.

[0068] In this signal injection device 10, the voltage driver 42 supplies a voltage signal S2 (cancellation current Ic) from one end T1 of the flux cancellation winding W1 to the output of the voltage driver 32 via the flux cancellation winding W1, and the voltage driver 32 supplies an AC signal S1 (AC current Iac) from the other end T2 of the flux cancellation winding W1 to the output of the voltage driver 42 via the flux cancellation winding W1, so that the cancellation current Ic and the AC current Iac are added together in the flux cancellation winding W1, generating magnetic fluxes Md and Mc in the magnetic core 2. Therefore, this signal injection device 10 can avoid magnetic saturation of the magnetic core 2 caused by a large DC current Ib flowing through the injection target line L, and as a result, supplying the AC signal S1 to the flux cancellation winding W1 reliably generates magnetic flux Mc in the magnetic core 2, making it possible to inject the AC signal S1 reliably and efficiently into the injection target line L. Furthermore, according to this signal injection device 10, the function of the cancellation winding and the function of the signal injection winding can be realized using a single magnetic flux cancellation winding W1, so the signal injection device 10 can be constructed inexpensively.

[0069] The magnetic flux cancellation unit 4C shown in FIG. 5 includes a Hall element 41, a magnetic flux cancellation winding W1, an LPF 43, and a current driver 45. The LPF 43, an example of a filter circuit, has frequency characteristics similar to those of the LPF 43 of the magnetic flux cancellation unit 4. It blocks the output of a voltage signal S2 based on the AC signal S1 included in the voltage signal S2 output from the Hall element 41 and passes the voltage signal S2 based on the DC current Ib. The current driver 45 amplifies the voltage signal S2 that has passed through the LPF 43 and outputs a cancellation current Ic with high output impedance in a direction that cancels the magnetic flux Mb, and supplies the cancellation current Ic to the magnetic flux cancellation winding W1. Similarly to the signal injection unit 3 shown in FIG. 1, the signal injection unit 3 includes a signal injection winding W2 wound around the magnetic core 2. The signal injection winding W2 supplies an AC signal S1 (AC current Iac) to inject the AC signal S1 into the injection target line L.

[0070] In this signal injection device 10, the current driver 45 supplies a voltage signal S2 (cancellation current Ic) to the magnetic flux cancellation winding W1 while maintaining a high output impedance. In this case, the signal injection unit 3 supplies an AC signal S1 to the signal injection winding W2, generating a magnetic flux Mc in the magnetic core 2. At this time, an AC current based on the generated magnetic flux Mc attempts to flow through the magnetic flux cancellation winding W1, but because the output impedance of the current driver 45 is high, the AC current based on the magnetic flux Mc does not flow in a direction from the magnetic flux cancellation winding W1 to the output unit of the current driver 45. Therefore, the current driver 45 does not pass a cancel current that would cancel the magnetic flux Mc generated in the magnetic core 2 based on the AC signal S1, but instead generates and supplies to the magnetic flux cancellation winding W1 a cancel current Ic that will cause the magnitude of the magnetic flux Mb detected by the Hall element 41 to become zero. Therefore, this signal injection device 10 can avoid magnetic saturation of the magnetic core 2 caused by a large DC current Ib flowing through the injection target line L, and as a result, by supplying an AC signal S1 (AC current Iac) to the signal injection winding W2, a magnetic flux Mc can be reliably generated in the magnetic core 2, and the AC signal S1 can be reliably and efficiently injected into the injection target line L.

[0071] Furthermore, according to the signal injection device 10 described above, by configuring a magnetic flux detection circuit by arranging any one of a Hall element 41, a fluxgate sensor, and a GMR element in the magnetic core 2, it is possible to reliably detect magnetic flux Mb despite the simple configuration.

[0072] Furthermore, by configuring the filter circuit with the LPF 43 including an inductor formed by a reactor with large inductance, it is possible to bring the cutoff frequency as close to 0 Hz as possible, which allows only the voltage signal S2 based on the DC current Ib to pass, and allows for an inexpensive configuration. Furthermore, with the signal injection device 10 having the magnetic flux cancellation unit 4, the LPF 43 blocks the voltage signal generated in the magnetic flux cancellation winding W1 based on the magnetic flux Mc generated in the magnetic core 2 when the AC signal S1 is supplied to the signal injection winding W2, from being input to the voltage driver 42. This prevents a decrease in the level of the injection current Ii (AC signal S1) injected into the injection target line L based on the magnetic flux Mc generated in the magnetic core 2, and as a result, the AC signal S1 can be reliably and efficiently injected into the injection target line L.

[0073] 6 is configured to supply to the flux cancellation winding W1 a cancellation current Ic that reduces the signal level of the voltage signal S2 corresponding to the magnetic flux based on twice the frequency of the AC signal S1 generated in the magnetic core 2, thereby preventing magnetic saturation of the magnetic core 2 caused by a large DC current Ib flowing through the injection target line L. Note that the signal injection device 10 that uses this magnetic flux cancellation unit 4D does not use a magnetic flux detection circuit such as a Hall element 41, and therefore uses an annular core without a gap as the magnetic core 2. However, an annular core with a gap can also be used as the magnetic core 2.

[0074] 6, the signal generation circuit 31 of the signal injection unit 3 is configured to include a 2f signal generation circuit 31a and a 1 / 2 frequency divider circuit 31b. In this case, the 2f signal generation circuit 31a generates a reference signal Sr for synchronous detection having a frequency twice that of the AC signal S1. Furthermore, the 1 / 2 frequency divider circuit 31b generates the AC signal S1 to be injected into the injection target line L by dividing the reference signal Sr output from the 2f signal generation circuit 31a by 1 / 2.

[0075] On the other hand, the magnetic flux cancellation unit 4D is configured with a magnetic flux cancellation winding W1, an adder circuit 44, voltage drivers 42, 46, and 49, a synchronous detection circuit 47, and an LPF 48. In this case, the synchronous detection circuit 47 synchronously detects, with a reference signal Sr, the voltage signal S2 (i.e., a distorted signal of the AC signal S1) contained in the voltage signal S2 generated in the magnetic flux cancellation winding W1 and having a frequency twice that of the AC signal S1, and outputs an output signal Sd. The LPF 48 is an example of a filter circuit, and extracts (passes) a DC signal Sdc generated based on a harmonic signal (the same frequency component as the frequency reference signal Sr) having a frequency twice that of the AC signal S1, which is a distorted signal of the AC signal S1, contained in the output signal Sd of the synchronous detection circuit 47, while blocking the passage of AC signals with frequencies twice or more that of the reference signal Sr. The voltage driver 49 amplifies the DC signal Sdc output from the LPF 48 and outputs it. The adder circuit 44 adds the DC signal Sdc output from the amplifier circuit 49 and the AC signal S1 output from the signal generation circuit 31 (1 / 2 frequency divider circuit 31b) to output a sum signal Sa. The voltage driver 42 amplifies the sum signal Sa output from the adder circuit 44 and supplies it to the magnetic flux cancellation winding W1.

[0076] In this signal injection device 10, a 2f signal generation circuit 31a in a signal generation circuit 31 of a signal injection unit 3 generates a reference signal Sr for synchronous detection and outputs it to a 1 / 2 frequency divider circuit 31b and a synchronous detection circuit 47. Furthermore, the 1 / 2 frequency divider circuit 31b receives the reference signal Sr and divides it by 1 / 2 to generate an AC signal S1, which is output to an adder circuit 44 and an A / D conversion circuit 71 of the processing unit 7. Meanwhile, in the magnetic flux cancellation unit 4D, a voltage driver 46 amplifies the input addition signal Sa and outputs it to the synchronous detection circuit 47. At this time, the synchronous detection circuit 47 synchronously detects a voltage signal having a frequency twice that of the AC signal S1 generated in the magnetic flux cancellation winding W1 using the input reference signal Sr, and outputs the voltage signal generated by synchronous detection as an output signal Sd. Furthermore, the LPF 48 extracts (passes) the DC signal Sdc included in the output signal Sd of the synchronous detection circuit 47 (i.e., a DC signal based on a harmonic signal with twice the frequency, which is a distorted signal of the AC signal S1) and blocks the passage of the AC signal. Next, the voltage driver 49 amplifies the DC signal Sdc output from the LPF 48 and outputs it to the adder circuit 44. At this time, the adder circuit 44 adds the DC signal Sdc output from the amplifier circuit 49 and the AC signal S1 output from the signal generation circuit 31 (1 / 2 frequency divider circuit 31b) to output the sum signal Sa. Furthermore, the voltage driver 42 amplifies the sum signal Sa output from the adder circuit 44 and supplies it to the magnetic flux cancellation winding W1. In this case, the voltage driver 42 outputs the addition signal Sa, so that a cancellation current Ic based on the DC signal Sdc is supplied to the flux cancellation winding W1 in a direction that cancels the magnetic flux Mb, thereby avoiding magnetic saturation of the magnetic core 2, and an AC signal S1 (AC current Iac) is supplied to the flux cancellation winding W1, and the AC signal S1 is injected into the injection target line L. In other words, in this magnetic flux cancellation unit 4D, feedback control is performed as a whole without using a magnetic flux detection circuit such as a Hall element 41, and the magnetic flux cancellation unit is configured as a flux gate sensor as a whole.

[0077] Therefore, this signal injection device 10 can avoid magnetic saturation of the magnetic core 2 caused by a large DC current Ib flowing through the injection target line L. As a result, by supplying an AC signal S1 (AC current Iac) to the magnetic flux cancellation winding W1, magnetic flux Mc is reliably generated in the magnetic core 2, and the AC signal S1 can be reliably and efficiently injected into the injection target line L. Furthermore, in this signal injection device 10, the magnetic flux cancellation unit 4D is feedback-controlled as a whole to detect the magnitude of a harmonic signal having a frequency twice the frequency of the AC signal S1, which is a distorted signal of the AC signal S1 generated in the magnetic core 2 in a magnetically saturated state, and to reduce the distorted signal. Therefore, this signal injection device 10 can directly detect magnetic saturation of the magnetic core 2. As a result, magnetic flux Mc can be more reliably generated without causing magnetic saturation in the magnetic core 2, and the AC signal S1 can be more reliably and efficiently injected into the injection target line L. Furthermore, according to this signal injection device 10, the function of the cancellation winding and the function of the signal injection winding can be realized using a single magnetic flux cancellation winding W1, so the signal injection device 10 can be constructed inexpensively.

[0078] In addition, in magnetic flux cancellation section 4D, if the necessary gain is ensured in each circuit, at least one of voltage driver 46 and voltage driver 49 can be omitted.

[0079] Furthermore, according to this signal injection device 10, by sweeping the frequency of the AC signal S1 for the signal generation circuit 31 in the signal injection unit 3, for example, when the signal injection device 10 is incorporated into an impedance measurement device, it can be configured as an FRA that can supply the AC signal S1, which is a sine wave signal, to a battery Bat or the like and measure its frequency response, thereby enabling high-precision impedance measurements.

[0080] Furthermore, according to this impedance measuring device 1, which is equipped with the above-mentioned signal injection device 10, when the processing unit 7 measures the internal impedance Zb of the battery Bat, which is the measurement target connected in series to the injection target line, when an AC signal S1 is injected into the injection target line L, the processing unit 7 measures the internal impedance Zb of the battery Bat based on the current value of the AC signal S1 flowing through the injection target line L (current value of the injected current Ii: voltage signal S2) and the voltage value generated across the battery Bat (voltage signal S4 across both ends).This makes it possible to more reliably generate magnetic flux Mc in the magnetic core 2 and more reliably and efficiently inject the AC signal S1 into the injection target line L, thereby making it possible to measure the internal impedance Zb of the battery Bat (measurement target) with high accuracy.

[0081] Furthermore, in this impedance measuring device 1, the non-contact current sensor 5 detects the injection current Ii (AC current) flowing through the injection target line L without contacting the injection target line L and outputs a voltage signal S2 to the processing unit 7. The voltage detection unit 6 contacts both ends of the battery Bat (the measurement target) and detects a voltage signal S4 across the battery Bat and outputs the detected voltage signal S4 to the processing unit 7 while being insulated from the battery Bat. This makes it possible to accurately detect the minute AC voltage generated within the battery Bat when the injection current Ii flows through the battery Bat, even if the output voltage of the battery Bat is very high or even if noise such as switching noise is present around the load Load or the impedance measuring device 1. Therefore, the impedance measuring device 1 can accurately measure the internal impedance Zb of the battery Bat. Furthermore, by using the non-contact current sensor 5, the impedance measuring device 1 can measure the internal impedance Zb of the battery Bat without contacting the injection target line L and without disconnecting it.

[0082] Furthermore, according to this impedance measuring device 1, the calculation circuit 77 of the processing unit 7 calculates the internal impedance Zb of the battery Bat as the measurement target based on the in-phase and quadrature components of the injection current Ii (detection signal S3) as an AC current output from the quadrature detection circuit 75 and the in-phase and quadrature components of the end-to-end voltage signal S4 as an AC voltage output from the quadrature detection circuit 76.This makes it possible to increase the ratio (S / N) of the signal level (S) to the noise level (N) and measure the internal impedance Zb with high accuracy even when the signal level of the AC signal S1 injected into the injection target line L is small.

[0083] Furthermore, the signal injection device 10 is not limited to being used in impedance measurement devices, but can also be used in various measuring instruments that inject and measure an AC signal S1 into an injection target line L. The impedance measurement device is not limited to measuring the internal impedance Zb of a battery Bat, but can also measure the impedance of various measurement targets. For example, when a water electrolysis cell that produces hydrogen by electrolyzing water is used as the measurement target, the water electrolysis cell can be connected to a power supply for the water electrolysis cell, instead of a load Load, via an injection target line L in a closed loop, and the internal impedance of the water electrolysis cell can be measured by connecting probes P1 and P2 to the anode and cathode of the water electrolysis cell.

[0084] Furthermore, in the impedance measuring device 1, a magnetic core through which the injection target line L is inserted may be provided separately from the magnetic core 2, and the winding W2 may be wound around this separate magnetic core 2.

[0085] Furthermore, an example of the impedance measuring device 1 using a non-contact current sensor 5 as a current sensor for detecting the current value of the injection current Ii has been described, but the current sensor is not limited to the non-contact type, and a configuration for detecting the current value of the injection current Ii by disposing a current transformer or a current detection resistor in the injection target line L can also be adopted.

[0086] Furthermore, if there is no need to insulate the reference potential (floating ground) of the impedance measuring device 1, the provision of the insulation circuit 62 can be omitted and the reference potential (ground) and the reference potential (floating ground) of the impedance measuring device 1 can be set to the same potential. Also, the A / D conversion circuits 71, 72, and 73 can be provided in the signal generating circuit 31, the non-contact current sensor 5, and the voltage detecting unit 6, respectively. Also, although an example has been described in which the 2f signal generating circuit 31a and the ½ frequency divider circuit 31b are configured as part of the signal generating circuit 31, a configuration in which the 2f signal generating circuit 31a and the ½ frequency divider circuit 31b are provided separately and independently from the signal generating circuit 31 can also be adopted.

[0087] Furthermore, with regard to measuring the internal impedance Zb of the battery Bat using the impedance measuring device 1 described above, when measuring the internal impedance Zb of one or more battery cells in a battery Bat configured by connecting multiple battery cells in series, the internal impedance Zb of one battery cell to be measured or the series internal impedance Zb of multiple battery cells connected in series can be measured by contacting probes P1 and P2 to both ends of the battery cell to be measured and measuring in the same manner as the measurement method described above.

[0088] Furthermore, in the impedance measuring device 1, an example has been described in which impedance such as the internal impedance Zb of the battery Bat is calculated by digital processing, but it is also possible to adopt a configuration in which the impedance is calculated by analog calculation using an analog circuit based on the AC signal S1, the detection signal S3, and the voltage signal S4 across both ends. [Industrial Applicability]

[0089] According to the present invention, it is possible to avoid magnetic saturation of the magnetic core caused by a large DC current flowing through the injection target line, and as a result, by supplying an AC signal to the second winding, a magnetic flux based on the AC signal is reliably generated in the magnetic core, and the AC signal can be reliably and efficiently injected into the injection target line through which the DC current is flowing. As a result, the present invention can be widely applied to such signal injection devices and impedance measurement devices. [Explanation of symbols]

[0090] 1. Impedance measuring device 10 Signal injection device 2 magnetic core 3,3A signal injection part 4, 4A to 4D Magnetic flux cancellation section 41 Hall element 42 Voltage Driver 43,48 LPF 44 Adding Circuit 45 Current Driver 47 Synchronous detection circuit 5. Non-contact current sensor 6 Voltage detection section 61 Buffer circuit 62 Insulation Circuit 7 Processing section 74 Phase shift circuit 75,76 Quadrature detection circuit 77 Arithmetic circuit Bat battery Ii injection current Load Load S1 AC signal S2 voltage signal S3 detection signal S4 Voltage signal at both ends SD output signal Sdc direct current signal Sr reference signal W1 Magnetic flux cancellation winding W2 Signal injection winding

Claims

1. An annular magnetic core through which an injection target line carrying a direct current is inserted; a signal injection unit that generates an AC signal to be injected into the injection target line and injects the AC signal into the injection target line, a magnetic flux canceling unit that supplies a canceling current to a first winding wound around the magnetic core, the canceling current generating a second magnetic flux for canceling a first magnetic flux generated in the magnetic core due to the DC current flowing through the injection target line that is inserted through the magnetic core; the magnetic flux canceling unit is configured to include the first winding, a magnetic flux detection circuit provided in the magnetic core and outputting a voltage signal corresponding to magnetic flux generated in the magnetic core, an amplifier circuit that amplifies the voltage signal output from the magnetic flux detection circuit, and a filter circuit that prevents output of a voltage signal based on the AC signal included in the voltage signal amplified by the amplifier circuit, but passes a voltage signal based on the DC current, thereby supplying the canceling current to the first winding in a direction that cancels the first magnetic flux, and that prevents input of a voltage signal generated in the first winding based on the AC signal to the amplifier circuit, The signal injection unit includes a second winding wound around the magnetic core, and supplies the AC signal to the second winding to inject the AC signal into the injection target line.

2. An annular magnetic core through which an injection target line through which a direct current flows is inserted; a signal injection unit that generates an AC signal to be injected into the injection target line and injects the AC signal into the injection target line, a magnetic flux canceling unit that supplies a canceling current to a first winding wound around the magnetic core, the canceling current generating a second magnetic flux for canceling a first magnetic flux generated in the magnetic core due to the DC current flowing through the injection target line that is inserted through the magnetic core; the magnetic flux cancellation unit is a signal injection device comprising: the first winding; a magnetic flux detection circuit provided in the magnetic core and outputting a voltage signal corresponding to the magnetic flux generated in the magnetic core; a filter circuit that blocks output of a voltage signal based on the AC signal included in the voltage signal output from the magnetic flux detection circuit and passes a voltage signal based on the DC current; an adder circuit that adds the voltage signal that has passed through the filter circuit and the AC signal to output a sum signal; and an amplifier circuit that amplifies the sum signal output from the adder circuit and supplies it to the first winding, so as to supply the canceling current to the first winding in a direction that cancels the first magnetic flux, and supplies the AC signal to the first winding to inject the AC signal into the injection target line.

3. An annular magnetic core through which an injection target line through which a direct current flows is inserted; a signal injection unit that generates an AC signal to be injected into the injection target line and injects the AC signal into the injection target line, a magnetic flux canceling unit that supplies a canceling current to a first winding wound around the magnetic core, the canceling current generating a second magnetic flux for canceling a first magnetic flux generated in the magnetic core due to the DC current flowing through the injection target line that is inserted through the magnetic core; the magnetic flux canceling unit comprises the first winding, a magnetic flux detection circuit provided in the magnetic core and outputting a voltage signal corresponding to the magnetic flux generated in the magnetic core, a filter circuit that blocks output of a voltage signal based on the AC signal included in the voltage signal output from the magnetic flux detection circuit and passes a voltage signal based on the DC current, and an amplifier circuit that amplifies the voltage signal that has passed through the filter circuit and supplies the canceling current to one end of the first winding in a direction that cancels the first magnetic flux, The signal injection device includes an amplifier circuit that amplifies the AC signal and supplies the amplified AC signal to the other end of the first winding to inject the AC signal into the injection target line.

4. An annular magnetic core through which an injection target line through which a direct current flows is inserted; a signal injection unit that generates an AC signal to be injected into the injection target line and injects the AC signal into the injection target line, a magnetic flux canceling unit that supplies a canceling current to a first winding wound around the magnetic core, the canceling current generating a second magnetic flux for canceling a first magnetic flux generated in the magnetic core due to the DC current flowing through the injection target line that is inserted through the magnetic core; the magnetic flux canceling unit comprises: the first winding; a magnetic flux detection circuit provided in the magnetic core and outputting a voltage signal corresponding to magnetic flux generated in the magnetic core; a filter circuit that blocks output of a voltage signal based on the AC signal included in the voltage signal output from the magnetic flux detection circuit and passes a voltage signal based on the DC current; and a current driver that amplifies the voltage signal that has passed through the filter circuit and supplies the canceling current to the first winding in a direction that cancels the first magnetic flux; The signal injection unit includes a second winding wound around the magnetic core, and supplies the AC signal to the second winding to inject the AC signal into the injection target line.

5. 5. The signal injection device according to claim 1, wherein the magnetic flux detection circuit is configured by arranging any one of a Hall element, a fluxgate sensor, and a GMR element in the magnetic core.

6. 6. The signal injection device according to claim 1, wherein the filter circuit is configured as a low-pass filter including an inductor formed by a reactor.

7. An annular magnetic core through which an injection target line through which a direct current flows is inserted; a signal injection unit that generates an AC signal to be injected into the injection target line and injects the AC signal into the injection target line, a magnetic flux canceling unit that supplies a canceling current to a first winding wound around the magnetic core, the canceling current generating a second magnetic flux for canceling a first magnetic flux generated in the magnetic core due to the DC current flowing through the injection target line that is inserted through the magnetic core; The magnetic flux cancellation unit supplies the cancellation current to the first winding, which reduces the signal level of a voltage signal corresponding to a magnetic flux based on twice the frequency of the AC signal generated in the magnetic core.

8. An annular magnetic core through which an injection target line through which a direct current flows is inserted; a signal injection unit that generates an AC signal to be injected into the injection target line and injects the AC signal into the injection target line, a magnetic flux canceling unit that supplies a canceling current to a first winding wound around the magnetic core, the canceling current generating a second magnetic flux for canceling a first magnetic flux generated in the magnetic core due to the DC current flowing through the injection target line that is inserted through the magnetic core; the signal injection unit generates the AC signal to be injected into the injection target line and a reference signal for synchronous detection having a frequency twice that of the AC signal; the magnetic flux cancellation unit is a signal injection device comprising: the first winding; a synchronous detection circuit that synchronously detects, with the reference signal, a voltage signal having twice the frequency of the AC signal generated in the first winding; a filter circuit that extracts a DC signal included in an output signal of the synchronous detection circuit; an adder circuit that adds the DC signal and the AC signal output from the filter circuit; and an amplifier circuit that amplifies the output signal of the adder circuit and supplies it to the first winding, thereby supplying the canceling current to the first winding in a direction that cancels the first magnetic flux, and supplies the AC signal to the first winding to inject the AC signal into the injection target line.

9. An annular magnetic core through which an injection target line through which a direct current flows is inserted; a signal injection unit that generates an AC signal to be injected into the injection target line and injects the AC signal into the injection target line, a magnetic flux canceling unit that supplies a canceling current to a first winding wound around the magnetic core, the canceling current generating a second magnetic flux for canceling a first magnetic flux generated in the magnetic core due to the DC current flowing through the injection target line that is inserted through the magnetic core; the signal injection unit generates the AC signal to be injected into the injection target line and a reference signal for synchronous detection having a frequency twice that of the AC signal; the magnetic flux cancellation unit includes the first winding, a synchronous detection circuit that synchronously detects a voltage signal having twice the frequency of the AC signal generated in the first winding using the reference signal, a filter circuit that extracts a DC signal included in the output signal of the synchronous detection circuit, an adder circuit that adds the DC signal and the AC signal output from the filter circuit, and an amplifier circuit that amplifies the output signal of the adder circuit and supplies it to the first winding, thereby supplying the cancellation current to the first winding in a direction that cancels the first magnetic flux, and supplies the AC signal to the first winding and injects the AC signal into the injection target line, and is a signal injection device that supplies the cancellation current to the first winding, which reduces the signal level of a voltage signal corresponding to magnetic flux based on twice the frequency of the AC signal generated in the magnetic core.

10. 10. The signal injection device according to claim 1, wherein the signal injection unit sweeps the frequency of the AC signal.

11. 11. An impedance measurement device comprising the signal injection device according to claim 1, for measuring the impedance of a measurement target connected in series to the injection target line, An impedance measuring device comprising: a processing unit that measures the impedance of the object to be measured based on the current value of the AC signal flowing through the injection target line and the voltage value generated in the object to be measured when the AC signal is injected into the injection target line.

12. a non-contact current sensor that detects the current of the AC signal flowing through the injection target line without contacting the injection target line and outputs a detection signal to the processing unit; a voltage detection unit that detects a voltage between both ends of the object to be measured; the voltage detection unit includes a voltage detection circuit that contacts both ends of the object to be measured to detect a voltage signal across both ends, and an isolation circuit that outputs the detected voltage signal across both ends to the processing unit while being insulated from the object to be measured; 12. The impedance measuring device according to claim 11, wherein the processing unit receives the detection signal as the current value of the AC signal and the end-to-end voltage signal as the voltage value generated in the object to be measured, thereby measuring the impedance of the object to be measured.

13. the processing unit includes a first quadrature detection circuit that receives the AC signal and performs quadrature detection on the detection signal to generate an in-phase component and a quadrature component of the current value of the AC signal, and a second quadrature detection circuit that receives the AC signal and performs quadrature detection on the both-end voltage signal to generate an in-phase component and a quadrature component of the voltage value of the both-end voltage signal; 13. The impedance measuring device according to claim 12, further comprising a calculation circuit that calculates the impedance of the object to be measured based on an in-phase component and a quadrature component of the current value of the AC signal output from the first quadrature detection circuit and an in-phase component and a quadrature component of the voltage value of the end-to-end voltage signal output from the second quadrature detection circuit.

Images