Impedance Measuring Device

Abstract

To reduce a level of a current component flowing in a load connection line connected to a load to avoid load failure when a level of an AC signal supplied to the load connection line is increased.SOLUTION: A current cancellation device includes: a non-contact type current sensor 3 for detecting a current component flowing in a load connection line L connected to the load Load in a non-contact manner with respect to the load connection line L; and a cancellation signal injection unit 4 for generating a cancellation signal Sk for canceling a noise signal Sn detected by the non-contact type current sensor 3 and injecting the generated cancellation signal Sk into the load connection line L in a non-contact manner.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a current cancellation device that cancels a current component flowing through a load connection line connected to a load. Place The present invention relates to an impedance measuring device that measures the impedance of a measurement object that is connected in series to a load connection line. [Background technology]

[0002] A known example of this type of impedance measurement device is a battery internal impedance measurement device (hereinafter also referred to as the "measurement device") disclosed in the following Patent Document: This measurement device includes an AC power supply unit, an AC voltage detection unit, an AC current detection unit, and an arithmetic control unit, and is configured to be able to measure the internal impedance of a secondary battery in a state where a DC current is being supplied to a load connected via a pair of power supply lines.

[0003] In this measurement device, an AC current supply unit supplies a measurement AC current to the secondary battery. At this time, an AC voltage detection unit detects the AC voltage generated across both terminals of the secondary battery when the AC current is supplied, and an AC current detection unit detects the AC current flowing through the secondary battery when the AC current is supplied. Next, an arithmetic and control unit calculates the internal impedance of the secondary battery based on the AC voltage detected by the AC voltage detection unit and the AC current detected by the AC current detection unit. Therefore, with this measurement device, when a measurement AC signal is supplied to a pair of power supply lines formed of conductors, it is possible to measure the impedance of a secondary battery as a measurement target connected in series to the pair of power supply lines. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-251625 A (pages 3-7, Figure 1) Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-described measuring device has the following problems. Specifically, when a device that generates switching noise, such as a switching power supply, is used as a load, switching noise is superimposed on the connection line (load connection line) connecting the load and the secondary battery, and the switching noise passes through the secondary battery. In this case, the AC current detection unit detects not only the AC current flowing through the secondary battery but also the switching noise, and the AC voltage detection unit detects not only the voltage caused by the AC current flow but also the switching noise, resulting in a decrease in the measurement accuracy of the impedance of the secondary battery. Therefore, there is a demand for improving this decrease in measurement accuracy. Furthermore, when the level of the measurement AC signal is increased to improve the measurement accuracy, there is a risk that the load may be damaged when a circuit element with low voltage resistance is used as the load and an AC signal with a large current value passes through the load. Therefore, there is also a demand for preventing this load damage.

[0006] The present invention has been made in view of the above-mentioned problem to be solved, and provides a current cancellation device that reduces the level of a current component flowing through a load connection line connected to a load and can avoid a breakdown of the load when the level of an AC signal supplied to the load connection line is increased. Place The main object of the present invention is to provide an impedance measuring device that reliably and accurately measures the impedance of an object to be measured that is connected in series to a load connection line. [Means for solving the problem]

[0017] To achieve the above objectives The impedance measuring device according to the present invention is an impedance measuring device for measuring the impedance of an object to be measured connected in series to the load connection line, the impedance measuring device comprising: a current component detecting unit that detects a current component flowing through a load connection line connected to a load without contacting the load connection line; and a cancellation signal injection unit that generates a cancellation signal that cancels the current component detected by the current component detecting unit and injects the generated cancellation signal into the load connection line without contacting the load connection line; the impedance measuring device comprising: a measurement signal supplying unit that generates an AC signal to be measured and supplies the AC signal to the object to be measured; a voltage detection unit that detects a voltage value of an AC voltage occurring across both ends of the object to be measured by contacting the both ends and outputs a voltage detection signal; and a processing unit that inputs the voltage detection signal and measures the impedance of the object to be measured based on the current value of the AC signal supplied from the measurement signal supplying unit to the object to be measured and the voltage value of the AC voltage indicated by the voltage detection signal;The object to be measured is a battery, the measurement signal supply unit is composed of an AC electronic load that converts the stored power of the battery into AC and supplies the AC signal generated by the AC conversion as the measurement AC signal, the object to be measured and the measurement signal supply unit are connected by a connection line to form a first closed loop, and the measurement signal supply unit and the load are connected by a connection line to form a second closed loop, and the current cancellation device connects two connection points between the connection line that forms the first closed loop and the connection line that forms the second closed loop, and injects the cancellation signal using the connection line that forms the second closed loop as the load connection line.

[0018] According to this impedance measuring device, the signal level of the AC signal can be increased by the AC electronic load, and the ratio (S / N) of the signal level (S) to the noise level (N) of the current detection signal or voltage detection signal can be increased. As a result, the impedance can be measured with high accuracy in the impedance calculation processing (measurement processing) performed by the processing unit. Furthermore, with this impedance measuring device, the influence of current components on the current detection signal and voltage detection signal can be avoided, thereby increasing the ratio (S / N) of the signal level (S) to the noise level (N) of the current detection signal and voltage detection signal, and as a result, impedance can be measured with high accuracy in the impedance calculation process (measurement process) performed by the processing unit. Furthermore, with this impedance measuring device, even if the level of the AC signal supplied to the load connection line (current value of the AC current) is increased, the current cancellation device sufficiently reduces the AC current flowing through the first closed loop, thereby avoiding load failure caused by the flow of an AC current of a large current value. Furthermore, with this impedance measuring device, even if switching noise occurs in the load, the noise current flowing through the load connection line can be sufficiently reduced. Furthermore, even if a large current flows through the load connection line, this impedance measuring device can sufficiently reduce the current flowing through the load connection line, thereby preventing load failure caused by the flow of a current of a large value.

[0019] Furthermore, the impedance measuring device according to the present invention comprises: an impedance measuring device for measuring the impedance of an object to be measured connected in series to the load connection line, the impedance measuring device comprising: a current component detecting unit that detects a current component flowing through a load connection line connected to a load without contacting the load connection line; and a cancellation signal injection unit that generates a cancellation signal that cancels the current component detected by the current component detecting unit and injects the generated cancellation signal into the load connection line without contacting the load connection line; the impedance measuring device comprising: a measurement signal supplying unit that generates an AC signal to be measured and supplies the AC signal to the object to be measured; a voltage detection unit that detects a voltage value of an AC voltage occurring across both ends of the object to be measured by contacting the both ends and outputs a voltage detection signal; and a processing unit that inputs the voltage detection signal and measures the impedance of the object to be measured based on the current value of the AC signal supplied from the measurement signal supplying unit to the object to be measured and the voltage value of the AC voltage indicated by the voltage detection signal; The measurement signal supply unit is composed of a bipolar power supply that generates the AC signal, the measurement object and the measurement signal supply unit are connected by a connection line to form a first closed loop, and the measurement signal supply unit and the load are connected by a connection line to form a second closed loop, and the current cancellation device connects two connection points between the connection line that forms the first closed loop and the connection line that forms the second closed loop, and injects the cancellation signal using the connection line that forms the second closed loop as the load connection line.

[0020] According to this impedance measuring device, the signal level of the AC signal can be increased by the AC bipolar power supply, and the ratio (S / N) of the signal level (S) to the noise level (N) of the current detection signal or voltage detection signal can be increased. As a result, the impedance can be measured with high accuracy in the impedance calculation process (measurement process) performed by the processing unit. Furthermore, with this impedance measuring device, the influence of current components on the current detection signal and voltage detection signal can be avoided, thereby increasing the ratio (S / N) of the signal level (S) to the noise level (N) of the current detection signal and voltage detection signal, and as a result, impedance can be measured with high accuracy in the impedance calculation process (measurement process) performed by the processing unit. Furthermore, with this impedance measuring device, even if the level of the AC signal supplied to the load connection line (current value of the AC current) is increased, the current cancellation device sufficiently reduces the AC current flowing through the first closed loop, thereby avoiding load failure caused by the flow of an AC current of a large current value. Furthermore, with this impedance measuring device, even if switching noise occurs in the load, the noise current flowing through the load connection line can be sufficiently reduced. Furthermore, even if a large current flows through the load connection line, this impedance measuring device can sufficiently reduce the current flowing through the load connection line, thereby preventing load failure caused by the flow of a current of a large value.

[0021] Furthermore, the impedance measuring device according to the present invention comprises: an impedance measuring device for measuring the impedance of an object to be measured connected in series to a load connection line, the impedance measuring device comprising: a current component detecting unit that detects a current component flowing through a load connection line connected to a load without contacting the load connection line; and a cancellation signal injection unit that generates a cancellation signal that cancels the current component detected by the current component detecting unit and injects the generated cancellation signal into the load connection line without contacting the load connection line; the impedance measuring device comprising: a measurement signal supplying unit that generates an AC signal for measurement and supplies the AC signal to the object to be measured; a voltage detection unit that detects a voltage value of an AC voltage occurring across both ends of the object to be measured by contacting the both ends and outputs a voltage detection signal; and a processing unit that inputs the voltage detection signal and measures the impedance of the object to be measured based on the current value of the AC signal supplied from the measurement signal supplying unit to the object to be measured and the voltage value of the AC voltage indicated by the voltage detection signal; Bypass capacitor Sa and the object to be measured and the bypass capacitor are connected by a connection line to form a first closed loop, and the bypass capacitor and the load are connected by a connection line to form a second closed loop, and the current cancellation device connects two connection points between the connection line that forms the first closed loop and the connection line that forms the second closed loop, and injects the cancellation signal using the connection line that forms the second closed loop as the load connection line.

[0022] In this impedance measuring device, the bypass capacitor sufficiently reduces the current component flowing through the first closed loop, reliably avoiding the influence of the current component on the current detection signal and the voltage detection signal, allowing the processing unit to measure the impedance more accurately. Also, in this impedance measuring device, the bypass capacitor causes the two connection points to be almost short-circuited in AC, causing the AC current to flow only through the second closed loop, allowing the current value of the AC current supplied to the object to be measured to be increased, thereby increasing the ratio (S / N) of the signal level (S) to the noise level (N) in the impedance calculation (measurement) performed by the processing unit, allowing the processing unit to measure the impedance more accurately. Furthermore, with this impedance measuring device, the influence of current components on the current detection signal and voltage detection signal can be avoided, thereby increasing the ratio (S / N) of the signal level (S) to the noise level (N) of the current detection signal and voltage detection signal, and as a result, impedance can be measured with high accuracy in the impedance calculation process (measurement process) performed by the processing unit. Furthermore, with this impedance measuring device, even if the level of the AC signal supplied to the load connection line (current value of the AC current) is increased, the current cancellation device sufficiently reduces the AC current flowing through the first closed loop, thereby avoiding load failure caused by the flow of an AC current of a large current value. Furthermore, with this impedance measuring device, even if switching noise occurs in the load, the noise current flowing through the load connection line can be sufficiently reduced. Furthermore, even if a large current flows through the load connection line, this impedance measuring device can sufficiently reduce the current flowing through the load connection line, thereby preventing load failure caused by the flow of a current of a large value.

[0023] Also, in the impedance measuring device according to the present invention, the measurement signal supplying section supplies the AC signal in a non-contact manner to the connection line that connects the two connection points and forms the first closed loop.

[0024] In addition, in the impedance measuring device according to the present invention, the measurement signal supply unit includes an AC signal generation circuit that generates the AC signal, and a supply circuit that supplies the AC signal generated by the AC signal generation circuit, and the supply circuit is composed of a ring-shaped second magnetic core that connects the two connection points and through which the connection line that forms the first closed loop is inserted, and a second winding wound around the second magnetic core, and the AC signal generated by the AC signal generation circuit is supplied to both ends of the second winding to supply the AC signal.

[0025] According to the impedance measuring device described above, even when the connection line forming the first closed loop is made of an insulating coated wire, an AC signal can be supplied without stripping the coating of the insulating coated wire.

[0026] In the impedance measuring device according to the present invention, the second magnetic core is provided with a gap. By providing a gap in the second magnetic core, this impedance measuring device can effectively avoid magnetic saturation of the second magnetic core even if the level of the AC signal (current value of the AC current) supplied to the load connection line is increased.

[0027] In addition, in the impedance measuring device according to the present invention, the measurement signal supply unit is configured to include an AC signal generation circuit that generates the AC signal and a supply circuit that supplies the AC signal generated by the AC signal generation circuit, the supply circuit being configured by an air core coil that connects the two connection points and through which the connection line that forms the first closed loop is inserted, and the AC signal generated by the AC signal generation circuit is supplied to both ends of the air core coil, thereby supplying the AC signal to the object to be measured. This impedance measuring device has a simple configuration but can reliably supply an AC signal to the load connection line.

[0028] In the impedance measuring device according to the present invention, the measurement signal supplying section supplies the AC signal According to this impedance measuring device, the configuration is simple, so that the impedance measuring device can be configured inexpensively.

[0031] Furthermore, the impedance measuring device according to the present invention comprises: an impedance measuring device for measuring the impedance of an object to be measured connected in series to the load connection line, the impedance measuring device comprising: a current component detecting section that detects a current component flowing through a load connection line connected to a load without contacting the load connection line; and a cancellation signal injection section that generates a cancellation signal that cancels the current component detected by the current component detecting section and injects the generated cancellation signal into the load connection line without contacting the load connection line; the impedance measuring device for measuring the impedance of an object to be measured connected in series to the load connection line, the impedance measuring device comprising: a measurement signal supplying section that generates an AC signal for measurement and supplies the AC signal to the object to be measured; a voltage detecting section that detects a voltage value of an AC voltage generated across both ends of the object to be measured by contacting both ends and outputs a voltage detection signal; a processing unit that measures the impedance of the object to be measured based on a current value of the AC signal supplied to the object to be measured and a voltage value of the AC voltage indicated by the voltage detection signal; and a current detection unit that detects the current value of the AC signal supplied to the object to be measured and outputs the detected current value to the processing unit as a current detection signal, wherein the processing unit comprises: a first quadrature detection circuit that receives the AC signal and performs quadrature detection on the current detection signal to generate in-phase and quadrature components of the AC current; a second quadrature detection circuit that receives the AC signal and performs quadrature detection on the voltage detection signal to generate in-phase and quadrature components of the AC voltage; and a calculation circuit that calculates the impedance of the object to be measured based on the in-phase and quadrature components of the AC current output from the first quadrature detection circuit and the in-phase and quadrature components of the AC voltage output from the second quadrature detection circuit, The cancellation signal injection unit of the current cancellation device includes a class D amplifier circuit as a final stage, and injects the cancellation signal amplified by the class D amplifier circuit. The cancellation signal injection unit is also provided with an A / D conversion circuit that performs analog-to-digital conversion on the current detection signal detected by the current detection unit and outputs the converted signal to the processing unit as current data, and an A / D conversion circuit that performs analog-to-digital conversion on the voltage detection signal detected by the voltage detection unit and outputs the converted signal to the processing unit as voltage data. Cancellation signal injection section The analog-to-digital conversion is performed in synchronization with an operation clock common to the operation clock of the class D amplifier circuit.

[0032] With this impedance measuring device, even when the signal level of the AC signal supplied to the load connection line is small, the ratio (S / N) of the signal level (S) to the noise level (N) can be increased, thereby enabling accurate impedance measurement. Also,With this impedance measuring device, even if the operating clock of the class D amplifier circuit is superimposed on the load connection line or propagated by radio waves, noise caused by the operating clock is sufficiently reduced by each A / D conversion circuit, so that the impedance can be measured with even greater accuracy in the impedance calculation process (measurement process) performed by the processing unit. Furthermore, with this impedance measuring device, the influence of current components on the current detection signal and voltage detection signal can be avoided, thereby increasing the ratio (S / N) of the signal level (S) to the noise level (N) of the current detection signal and voltage detection signal, and as a result, impedance can be measured with high accuracy in the impedance calculation process (measurement process) performed by the processing unit. Furthermore, with this impedance measuring device, even if the level of the AC signal supplied to the load connection line (current value of the AC current) is increased, the current cancellation device sufficiently reduces the AC current flowing through the first closed loop, thereby avoiding load failure caused by the flow of an AC current of a large current value. Furthermore, with this impedance measuring device, even if switching noise occurs in the load, the noise current flowing through the load connection line can be sufficiently reduced. Furthermore, even if a large current flows through the load connection line, this impedance measuring device can sufficiently reduce the current flowing through the load connection line, thereby preventing load failure caused by the flow of a current of a large value. In addition, in the impedance measuring device according to the present invention, the object to be measured and the load are connected by the load connection line to form a closed loop, and the measurement signal supply unit supplies the AC signal between both ends of the object to be measured. This impedance measuring device has a simple configuration, so it can be constructed inexpensively. In addition, in the impedance measuring device according to the present invention, the cancellation signal injection unit is configured to include a cancellation signal generation circuit that generates the cancellation signal, and an injection circuit that injects the cancellation signal generated by the cancellation signal generation circuit into the load connection line, and the cancellation signal generation circuit amplifies and phase-adjusts the current component detected by the current component detection unit and outputs the resultant to the injection circuit as the cancellation signal. This impedance measuring device has a simpler configuration than, for example, a configuration that includes an oscillator and generates a cancellation signal that is opposite in phase to and has the same signal level as the current component detected by the current component detection unit, yet can reliably cancel the current component on the load connection line. In addition, in the impedance measuring device according to the present invention, the injection circuit is composed of an annular first magnetic core through which the load connection line is inserted and a first winding wound around the first magnetic core, and the cancellation signal is injected by supplying the cancellation signal generated by the cancellation signal generation circuit to both ends of the first winding. This impedance measuring device has a simple configuration but can reliably cancel the current component on the load connection line. In the impedance measuring device according to the present invention, the first magnetic core is provided with a gap, which makes it possible to effectively avoid magnetic saturation of the first magnetic core even when the level of the cancellation signal injected into the load connection line is increased. In addition, in the impedance measuring device according to the present invention, the cancellation signal injection section is configured to include a cancellation signal generation circuit that generates the cancellation signal, and an injection circuit that injects the cancellation signal generated by the cancellation signal generation circuit into the load connection line, the injection circuit being configured by an air core coil through which the load connection line is inserted, and the cancellation signal generated by the cancellation signal generation circuit is supplied to both ends of the air core coil, thereby injecting the cancellation signal into the load connection line. This impedance measuring device has a simple configuration but can reliably inject the cancellation signal into the load connection line. [Effects of the Invention]

[0033] The present invention Impedance Measuring Device According to the present invention, the level of a current component flowing through a load connection line connected to a load can be reduced, and a load failure can be avoided when the level of an AC signal supplied to the load connection line is increased. Current cancellation device By providing this, it is possible to reliably and accurately measure the impedance of the measurement object connected in series to the load connection line. [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a diagram showing the configuration of an impedance measuring device 1. FIG. [Figure 2] FIG. 3 is a diagram showing another configuration of the impedance measuring device 1. [Figure 3] 10 is a frequency characteristic diagram showing the ability of the cancellation signal injection unit 4 to cancel the noise signal Sn. FIG. [Figure 4] FIG. 1 is a diagram showing the configuration of an impedance measuring device 1A. [Figure 5] FIG. 2 is a diagram showing the configuration of an impedance measuring device 1B. [Figure 6]FIG. 1 is a diagram showing the configuration of an impedance measuring device 1C. [Figure 7] FIG. 1 is a diagram showing the configuration of an impedance measuring device 1D. [Figure 8] FIG. 4 is a diagram showing the configuration of an injection circuit 44A. [Figure 9] FIG. 2 is a diagram showing the configuration of an injection circuit 25A. DETAILED DESCRIPTION OF THE INVENTION

[0035] below ,stomach An embodiment of an impedance measuring device will be described with reference to the accompanying drawings.

[0036] The impedance measuring device 1 shown in FIG. 1 is an example of an "impedance measuring device" equipped with a "current canceling device (current canceling device 10 in this example)," and is configured to be able to measure, for example, the impedance (internal impedance Zb in this example) of a battery Bat as a measurement object when a load Load is connected to the measurement object and a closed loop Lo1 is established. In this case, a specific example of the measurement object is a battery Bat (an example of a battery) having a high voltage across the battery, such as about DC 650 V, used in a fuel cell vehicle (FCV). The impedance measuring device 1 is also configured as a frequency response analyzer (FRA) that can supply an AC signal Sac, which is a sine wave signal (described later), to the battery Bat and measure its frequency response, thereby enabling highly accurate impedance measurement.

[0037] Below, we will explain an example of measuring the internal impedance Zb of the battery Bat when the battery Bat is connected to the load Load by a power line (hereinafter also referred to as the "load connection line L") made of a conductor such as an insulated cable whose conductor core is insulated, an enameled wire, or an uninsulated electric wire, with the load being the motor of a fuel cell vehicle that generates electrical noise when rotating. Note that the battery Bat is made up of multiple battery cells connected in series, but in Figure 1 it is shown as a single battery as a whole.

[0038] The impedance measuring device 1 is configured to include a measuring unit 2, a non-contact current sensor 3, a cancellation signal injection unit 4, a processing unit 5, and an output unit 6. In this case, the non-contact current sensor 3 and the cancellation signal injection unit 4 configure a current cancellation device 10.

[0039] The measurement unit 2 is configured with an AC current supply circuit 21, an AC voltage detection circuit 22, a pair of contact-type probes P1 and P2, and a pair of contact-type probes P3 and P4. In this case, the AC current supply circuit 21 constitutes a "measurement signal supply unit" and a "current detection unit," and generates a measurement AC signal Sac and applies the AC signal Sac to both ends of a battery Bat (a measurement target) via probes P1 and P2, thereby supplying an AC current Iac to a closed loop Lo1 consisting of the battery Bat and a load Load, and to a closed loop Lo2 consisting of the battery Bat and the AC current supply circuit 21. The AC current supply circuit 21 also sweeps the frequency (e.g., 1 Hz to 10 MHz) by controlling the signal level and frequency of the AC signal Sac using a control signal output from the processing unit 5. However, frequency sweeping is not essential, and if sweeping is not required, the AC current supply circuit 21 can also be configured to generate an AC signal Sac with a fixed frequency. The AC current supply circuit 21 also outputs an AC reference signal Sr as a reference signal indicating the voltage value, frequency, and phase of the AC signal Sac. The AC current supply circuit 21 also detects the AC current Iac flowing through the battery Bat (closed loop Lo2) using an internal current transformer, current detection resistor, etc., and outputs a current detection signal S1 indicating the current value, frequency, and phase of the AC current Iac. The AC voltage detection circuit 22 detects, via probes P3 and P4, the voltage generated across the battery Bat when the AC current Iac is supplied from the AC current supply circuit 21, and outputs a voltage detection signal S2 indicating the voltage value, frequency, and phase of the voltage across the battery Bat.

[0040] The non-contact current sensor 3 is a so-called clamp-type current sensor and functions as a non-contact current component detector. This non-contact current sensor 5 detects the AC current component flowing through the load connection line L without contacting the load connection line L (the core wire (conductor) of the load connection line L) and outputs the detected current component as a noise signal Sn to the cancellation signal injection unit 4. Specifically, as shown in FIG. 1, the non-contact current sensor 5 is configured to include, within a semi-annular case (not shown), a pair of magnetic cores 3a, 3a, one winding wound around the magnetic cores 3a, 3a and made of an insulated wire, and a current detection circuit. Note that the winding and current detection circuit are not shown in the figure. In this non-contact current sensor 5, a pair of magnetic cores 3a, 3a are configured to be openable and closable. To clamp the load connection line L, an operation switch (not shown) is operated to open the magnetic cores 3a, allowing the load connection line L to enter through the opening. The operation switch is then operated to close the magnetic cores 3a, 3a (annular), thereby clamping the load connection line L with the magnetic cores 3a, 3a. When the load connection line L is clamped, a magnetic flux whose magnitude varies depending on the magnitude of the current component flowing through the load connection line L is generated in the magnetic cores 3a, 3a, and a current whose magnitude varies depending on the magnitude of the magnetic flux is output from the winding. The current detection circuit converts the current output from the winding into a voltage to generate a noise signal Sn and outputs it to the cancellation signal injection unit 4.

[0041] The cancellation signal injection unit 4 includes an amplifier circuit 41, a phase adjustment circuit 42, an inverting amplifier circuit 43, and an injection circuit 44. The cancellation signal injection unit 4 generates a cancellation signal Sk that cancels the current component flowing through the load connection line L and injects the generated cancellation signal Sk into the load connection line L in a non-contact manner. In this case, the amplifier circuit 41, the phase adjustment circuit 42, and the inverting amplifier circuit 43 form a "cancellation signal generation circuit." The amplifier circuit 41 amplifies the noise signal Sn output from the non-contact current sensor 3 by a predetermined gain and outputs the amplified signal to the phase adjustment circuit 42. The phase adjustment circuit 42 adjusts the phase of the input noise signal Sn so that it is in phase with the current component flowing through the load connection line L, and outputs the amplified signal to the inverting amplifier circuit 43. Specifically, the phase adjustment circuit 42 adjusts the phase of the noise signal Sn so that the signal level of the input noise signal Sn is minimized. The inverting amplifier circuit 43 is configured with a class D amplifier circuit at its output stage, which operates in synchronization with a clock signal CL2 output from the processing unit 5. The inverting amplifier circuit 43 class-D amplifies the input noise signal Sn with a predetermined gain, inverts the amplified noise signal, and outputs the amplified noise signal as a cancellation signal Sk to the injection circuit 44. The gains of the inverting amplifier circuit 43 and the phase adjustment circuit 42 are predetermined so that the magnitude of the current component flowing through the load connection line L is equal to the magnitude of the cancellation signal Sk when the current component (noise signal Sn) detected by the non-contact current sensor 3 passes through the phase adjustment circuit 42, the inverting amplifier circuit 43, and the inverting amplifier circuit 43 and is injected into the load connection line L from the injection circuit 44. The inverting amplifier circuit 43 is also supplied with a clock signal CL2 (described later) from the processing unit 5, and performs class D amplification in synchronization with this clock signal CL2. Therefore, by including a class D amplifier circuit as the final stage, the inverting amplifier circuit 43 can maintain the signal level of the cancellation signal Sk at a required level even when the load fluctuates.

[0042] 3, the "cancellation signal generation circuit" has the ability to detect the noise signal Sn over a wide frequency band and generate a cancellation signal Sk that can cancel the noise signal Sn, so as to have a nearly flat frequency characteristic in the range from a frequency slightly higher than the DC voltage to a frequency higher than the measurement AC signal Sac. Note that, as a different configuration from this example, a non-inverting amplifier circuit may be provided instead of the inverting amplifier circuit 43, and the phase adjustment circuit 42 may adjust the phase of the noise signal Sn so that it is in opposite phase to the current component flowing through the load connection line L. Furthermore, if the necessary gain is ensured in each circuit in the cancellation signal injection unit 4, the amplifier circuit 41 may be omitted.

[0043] The injection circuit 44 includes a magnetic core Mc1 as a first magnetic core and a winding W1 as a first winding wound around the magnetic core Mc1. The injection circuit 44 injects a cancellation current Ik based on the cancellation signal Sk output from the inverting amplifier circuit 43 into the core wire of the load connection line L in a non-contact manner. The magnetic core Mc1 is formed using materials such as ferrite, permalloy, permendur, silicon steel, and pure iron, and has an annular shape such as a circle, ellipse, rectangle, or polygon to allow the load connection line L to pass through. A gap G1 is provided in the magnetic core Mc1 to prevent magnetic saturation of the magnetic core Mc1. Alternatively, the magnetic core Mc1 may have a separable clamp-type configuration. The injection circuit 44 applies the cancellation signal Sk to both ends of the winding W1, thereby injecting the cancellation signal Sk into the load connection line L in a transformer-like manner (the winding W1 is a multi-turn primary winding and the load connection line L is a single-turn secondary winding). At this time, a current based on the cancellation signal Sk flows through the winding W1, a magnetic flux based on the cancellation signal Sk is generated in the magnetic core Mc1, and a cancellation current Ik having a current value according to the magnitude of the magnetic flux is injected (supplied) to the load connection line L as a normal mode signal.

[0044] 2, the processing unit 5 is configured to include A / D conversion circuits 51 to 53, a phase shift circuit 54, quadrature detection circuits 55 and 56, an arithmetic circuit 57, an internal memory 58, and a clock generation circuit 59. The processing unit 5 receives the current detection signal S1 and the voltage detection signal S2 and measures the internal impedance Zb of the battery Bat, which is the object of measurement, based on the current detection signal S1 and the voltage detection signal S2. In this case, the A / D conversion circuit 51 receives the AC reference signal Sr output from the AC current supply circuit 21 and performs A / D conversion (analog-to-digital conversion) on the signal Sr to output signal data D11 (sinωt) indicating the voltage value, frequency, and phase of the sinusoidal AC signal Sac to the phase shift circuit 54 and the quadrature detection circuits 55 and 56. The A / D conversion circuit 52 receives the current detection signal S1 output from the AC current supply circuit 21, performs A / D conversion on it, and outputs signal data D12 indicating the current value, frequency, and phase of the current detection signal S1 (AC current Iac) to the quadrature detection circuit 55. The A / D conversion circuit 53 receives the voltage detection signal S2 output from the AC voltage detection circuit 22, performs A / D conversion on it, and outputs signal data D13 indicating the voltage value, frequency, and phase of the voltage detection signal S2 to the quadrature detection circuit 56.

[0045] The phase-shift circuit 54 receives the signal data D11 (sinωt) output from the A / D conversion circuit 51, shifts the phase of the AC signal Sac, which is a sine wave signal represented 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 55 and 56. The quadrature detection circuit 55 receives signal data D12 indicating the current detection signal S1 (the AC current value of the AC current Iac) output from the A / D conversion circuit 52, and performs quadrature detection on the signal data D12 using signal data D11 (sinωt) indicating the sine wave AC signal Sac output from the A / D conversion circuit 51 and signal data D11 (cosωt) indicating the cosine wave AC signal Sac output from the phase shift circuit 54. The quadrature detection circuit 55 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 AC current Iac as complex numbers and outputs the current data Di to the arithmetic circuit 57. The quadrature detection circuit 56 receives signal data D13 indicating the voltage detection signal S2 (the voltage value of the AC voltage generated across the battery Bat due to the flow of the AC current Iac) output from the A / D conversion circuit 53, and performs quadrature detection on the signal data D13 using signal data D11 (sinωt) indicating the sine wave AC signal Sac output from the A / D conversion circuit 51 and signal data D11 (cosωt) indicating the cosine wave AC signal Sac output from the phase shift circuit 54. The quadrature detection circuit 56 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 voltage detection signal S2 as complex numbers and outputs the voltage data Dv to the arithmetic circuit 57.

[0046] The calculation circuit 57 receives the current data Di output from the quadrature detection circuit 55 and the voltage data Dv output from the quadrature detection circuit 56, and calculates the internal impedance Zb of the battery Bat based on the current data Di and the voltage data Dv. The calculation circuit 57 outputs impedance data Dz indicating the internal impedance Zb of the battery Bat as the calculation result to the internal memory 58 for storage and also outputs it to the output unit 6. The internal memory 58 is configured with a semiconductor memory, a hard disk drive, or the like, and stores the impedance data Dz, etc. The clock generation circuit 59 generates and outputs a clock signal CL1 as an operating clock for each of the A / D conversion circuits 51 to 53, and also generates and outputs a clock signal CL2 as an operating clock for the final-stage class D amplifier circuit in the inverting amplifier circuit 43 of the cancellation signal injection unit 4. In this case, the clock generation circuit 59 generates the clock signals CL1 and CL2 so that one is N times the other (N is an integer greater than or equal to 1) and is synchronized with the other.

[0047] The output unit 6 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 5 to display the internal impedance Zb of the battery Bat on the screen. Note that instead of a display device, the output unit 6 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.

[0048] Next, the measurement process of measuring the internal impedance Zb of the battery Bat as the measurement target by the impedance measuring device 1 will be described with reference to the accompanying drawings.

[0049] First, the load connection line L is inserted into the injection circuit 44, and the battery Bat and the load Load are connected by the load connection line L. When the load Load is activated in this state, a direct current Ib flows from the battery Bat to the load Load via the load connection line L, as shown in Fig. 1. In this state, the non-contact current sensor 3 is clamped to the load connection line L, and the probes P1 to P4 are brought into contact with both ends of the battery Bat.

[0050] Next, a measurement start switch (not shown) is operated. This causes the processing unit 5 to control the AC current supply circuit 21 of the measurement unit 2 to generate an AC signal Sac. At this time, the AC current supply circuit 21 generates the AC signal Sac while sweeping the frequency, supplies the generated AC signal Sac across the battery Bat via probes P1 and P2, and outputs an AC reference signal Sr based on the AC signal Sac to the processing unit 5. In this case, an AC current Iac based on the AC signal Sac flows through a closed loop Lo1 consisting of the battery Bat, the load Load, and the load connection line L connecting the battery Bat and the load Load, and also flows through a closed loop Lo2 consisting of the probe P1, the battery Bat, the probe P2, and circuits within the AC current supply circuit 21.

[0051] Meanwhile, the load Load generates electrical noise during rotation, and this electrical noise becomes a noise current In and flows through the load connection line L in the closed loop Lo1. In this case, in the current cancellation device 10, the non-contact current sensor 3 detects the current components of the AC current Iac and the noise current In flowing through the load connection line L without contacting the load connection line L (the core wire (conductor) of the load connection line L), and outputs the detected current components as a noise signal Sn to the cancellation signal injection unit 4. In the cancellation signal injection unit 4, the amplifier circuit 41 amplifies the noise signal Sn output from the non-contact current sensor 3 by a predetermined gain and outputs the amplified signal to the phase adjustment circuit 42. At this time, the phase adjustment circuit 42 adjusts the phase of the input noise signal Sn so that it has the same phase as the current component flowing through the load connection line L, that is, so that the signal level of the input noise signal Sn is minimized, and outputs the amplified signal to the inverting amplifier circuit 43. The inverting amplifier circuit 43 performs class D amplification on the input noise signal Sn with a predetermined gain, and also performs inverting amplification on the input noise signal Sn and outputs the result to the injection circuit 44 as a cancellation signal Sk.

[0052] At this time, in the injection circuit 44, the cancellation signal Sk output from the inverting amplifier circuit 43 is supplied across the winding W1, causing a magnetic flux based on the cancellation signal Sk to be generated in the magnetic core Mc1, and a cancellation current Ik of a current value corresponding to the magnitude of the magnetic flux to be injected as a normal mode signal into the load connection line L. As a result, in the load connection line L, the AC current Iac and the noise current In cancel out the cancellation current Ik, which is in opposite phase to the AC current Iac and the noise current In but at the same current level as the AC current Iac and the noise current In, and the current levels of the AC current Iac and the noise current In flowing through the load connection line L (closed loop Lo1) are sufficiently reduced. Therefore, the only AC current flowing through the battery Bat is the AC current Iac flowing through the closed loop Lo2 consisting of the battery Bat and the AC current supply circuit 21.

[0053] In the measurement unit 2, the AC current supply circuit 21 detects the AC current Iac flowing through the closed loop Lo2 and outputs a current detection signal S1 to the processing unit 5, as well as an AC reference signal Sr to the processing unit 5. Furthermore, when the AC current Iac is supplied from the AC current supply circuit 21, the AC voltage detection circuit 22 detects, via probes P3 and P4, a voltage generated across the battery Bat based on the AC current Iac flowing inside the battery Bat, and outputs this as a voltage detection signal S2 to the processing unit 5. In this case, as described above, the only AC current flowing through the battery Bat is the AC current Iac flowing through the closed loop Lo2, and therefore the current detection signal S1 and voltage detection signal S2 are detection signals based only on the AC current Iac, and therefore the internal impedance Zb can be measured accurately in the impedance measurement process by the processing unit 5, which will be described later.

[0054] Meanwhile, in the processing unit 5, the A / D conversion circuit 51 receives the AC reference signal Sr and performs A / D conversion in synchronization with the clock signal CL1 to output signal data D11 (sinωt) indicating the voltage value, frequency, and phase of the sinusoidal AC signal Sac to the phase shift circuit 54 and the quadrature detection circuits 55 and 56. The A / D conversion circuit 52 receives the current detection signal S1 and performs A / D conversion in synchronization with the clock signal CL1 to output signal data D12 indicating the current value, frequency, and phase of the AC current Iac to the quadrature detection circuit 55. The A / D conversion circuit 53 receives the voltage detection signal S2 and performs A / D conversion in synchronization with the clock signal CL1 to output signal data D12 indicating the voltage value, frequency, and phase of the AC signal Sac across the battery Bat to the quadrature detection circuit 56. In addition, the phase shift circuit 54 inputs the signal data D11 and shifts the phase of the AC signal Sac, which is a sine wave signal represented 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 55 and 56.

[0055] The quadrature detection circuit 55 also receives signal data D12 indicating the current detection signal S1, and performs quadrature detection on the signal data D12 using signal data D11 (sinωt) indicating the sine wave AC signal Sac and signal data D11 (cosωt) indicating the cosine wave AC signal Sac to generate current data Di indicating, as a complex number, the in-phase and quadrature components of the current value of the AC current Iac flowing through the battery Bat, and outputs this to the arithmetic circuit 57. The quadrature detection circuit 56 also receives signal data D13 indicating the voltage across the battery Bat (AC signal Sac) using the signal data D11 (sinωt) and signal data D11 (cosωt) to generate voltage data Dv indicating, as a complex number, the in-phase and quadrature components of the voltage value of the voltage across the battery Bat, and outputs this to the arithmetic circuit 57. Next, the arithmetic circuit 57 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 58 for storage, as well as to the output unit 6. At this time, the output unit 6 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 arithmetic circuit 57 can also display the frequency characteristics of the internal impedance Zb of the battery Bat relative to the frequency of the AC signal Sac on the screen of the display device by including frequency information of the AC signal Sac in the impedance data Dz. The arithmetic circuit 57 can also generate current value information of the DC current Ib flowing through the load connection line L based on the input current data Di (which may be signal data D12 output from the A / D conversion circuit 52), 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.

[0056] Furthermore, the arithmetic circuit 57 monitors the current value of the AC current Iac flowing through the closed loop Lo2 based on the input current data Di (which may be the signal data D12 output from the A / D conversion circuit 52), and controls the AC current supply circuit 21 so that the current value of the AC current Iac falls within a target current value range required for impedance measurement. As a result, the AC current Iac falls within the target current value range, and the ratio (S / N) of the signal level (S) to the noise level (N) of the current detection signal S1 and the voltage detection signal S2 can be increased, and as a result, the internal impedance Zb can be measured with high accuracy in the calculation process (measurement process) of the internal impedance Zb performed by the arithmetic circuit 57.

[0057] Furthermore, in the impedance measuring device 1, even if switching noise occurs in the load Load, the current cancellation device 10 reduces the noise current In flowing through the load connection line L, thereby avoiding the influence of the noise current In on the current detection signal S1 and the voltage detection signal S2. As a result, the ratio (S / N) of the signal level (S) to the noise level (N) of the current detection signal S1 and the voltage detection signal S2 can be increased, and as a result, the internal impedance Zb can be measured more accurately in the calculation process (measurement process) of the internal impedance Zb performed by the calculation circuit 57. Furthermore, in the impedance measuring device 1, the clock signal CL1, which is the operating clock of each of the A / D conversion circuits 51 to 53, and the clock signal CL2, which is the operating clock of the final-stage class D amplifier circuit in the inverting amplifier circuit 43, are synchronized with each other, so that even if the clock signal CL2 of the inverting amplifier circuit 43 is superimposed on the load connection line L or propagated by radio waves, noise caused by the clock signal CL2 is reduced by each of the A / D conversion circuits 51 to 53, and the internal impedance Zb can be measured with even greater accuracy in the calculation process (measurement process) of the internal impedance Zb performed by the arithmetic circuit 57. This completes the measurement of the internal impedance Zb of the battery Bat by the impedance measuring device 1.

[0058] Next, an impedance measuring device 1A will be described as an "impedance measuring device." In the configurations of the impedance measuring devices 1A to 1D described below, components having the same functions as the components in the impedance measuring device 1 described above will be assigned the same reference numerals, and duplicated explanations will be omitted.

[0059] 4, the impedance measuring device 1A is configured to include a measurement unit 2A, a non-contact current sensor 3, a cancellation signal injection unit 4, a processing unit 5, and an output unit 6, and measures the internal impedance Zb of the battery Bat based on a current detection signal S1 and a voltage detection signal S2, similar to the impedance measuring device 1. In this case, the measurement unit 2A is configured to include an AC voltage detection circuit 22, and an AC electronic load 23 instead of the AC current supply circuit 21 in the impedance measuring device 1.

[0060] The AC electronic load 23 constitutes a "measurement signal supply unit" and a "current detection unit," converts the power stored in the battery Bat into AC, and outputs the AC signal generated by the AC conversion as a measurement AC signal Sac. The AC electronic load 23 also outputs to the processing unit 5 an AC reference signal Sr serving as a reference signal indicating the voltage value, frequency, and phase of the AC signal Sac, and a current detection signal S1 indicating the current value, frequency, and phase of the output AC current Iac. In this case, in the impedance measurement system using the impedance measurement device 1A, the battery Bat and the AC electronic load 23 are connected by a connection line to form a closed loop Lo3 (first closed loop), and the AC electronic load 23 and the load Load are connected by a connection line to form a closed loop Lo4 (second closed loop). The current cancellation device 10 also connects two connection points (intersections) Po1 and Po2 between the connection line forming the closed loop Lo3 and the connection line forming the closed loop Lo4, and injects a cancellation signal Sk using the connection line forming the closed loop Lo4 as the load connection line L.

[0061] Next, the operation of the impedance measuring device 1A will be described. The measurement process for measuring the internal impedance Zb of the battery Bat as the measurement target is the same as that of the impedance measuring device 1, so duplicated explanations will be omitted and only the different processes will be described. First, prior to the start of measurement, both output terminals of the AC electronic load 23 are connected to the connection points Po1 and Po2. In this case, both output terminals of the AC electronic load 23 may be connected to the connection points Po1 and Po2 directly, or both output terminals of the AC electronic load 23 may be connected to the connection points Po1 and Po2 using probes (not shown). At the start of measurement, the AC electronic load 23 converts the stored power of the battery Bat into AC at a cycle controlled by the processing unit 5 and outputs the AC signal generated by the AC conversion as the measurement AC signal Sac. At this time, an AC current Iac based on the AC signal Sac is supplied to both closed loops Lo3 and Lo4.

[0062] At this time, similarly to the current cancellation device 10 in the impedance measuring device 1, a cancellation signal Sk output from the inverting amplifier circuit 43 is supplied between both ends of the winding W1, generating a magnetic flux based on the cancellation signal Sk in the magnetic core Mc1, and a cancellation current Ik having a current value corresponding to the magnitude of the magnetic flux is injected as a normal-mode signal into the load connection line L (closed loop Lo4). As a result, in the load connection line L, the AC current Iac and the noise current In cancel out the cancellation current Ik, which is opposite in phase to but has the same current level as the AC current Iac and the noise current In, thereby sufficiently reducing the current levels of the AC current Iac and the noise current In flowing through the load connection line L (closed loop Lo4). Therefore, the only AC current flowing through the battery Bat is the AC current Iac flowing through the closed loop Lo3 consisting of the battery Bat and the AC current supply circuit 21. Next, in the impedance measuring device 1A as well, the processing unit 5 performs calculation processing (measurement processing) of the internal impedance Zb, similarly to the impedance measuring device 1.

[0063] Next, an impedance measuring device 1B will be described as an "impedance measuring device." As shown in Fig. 5, the impedance measuring device 1B is configured to include a measuring unit 2B, a non-contact current sensor 3, a cancellation signal injection unit 4, a processing unit 5, and an output unit 6, and measures the internal impedance Zb of the battery Bat based on a current detection signal S1 and a voltage detection signal S2, similar to the impedance measuring device 1. In this case, the measuring unit 2B is configured to include an AC voltage detection circuit 22, and an AC bipolar power supply 24 instead of the AC electronic load 23 in the impedance measuring device 1A.

[0064] The AC bipolar power supply 24 constitutes a "measurement signal supply unit" and a "current detection unit," and outputs an AC signal generated by high-speed high-voltage amplification of the AC voltage of an AC voltage source (not shown) provided inside as a measurement AC signal Sac. The AC bipolar power supply 24 also outputs to the processing unit 5 an AC reference signal Sr serving as a reference signal indicating the voltage value, frequency, and phase of the AC signal Sac, and a current detection signal S1 indicating the current value, frequency, and phase of the output AC current Iac. In this case, in the impedance measurement system using the impedance measuring device 1B, the battery Bat and the AC bipolar power supply 24 are connected by a connection line to form a closed loop Lo5 (first closed loop), and the AC bipolar power supply 24 and a load Load are connected by a connection line to form a closed loop Lo6 (second closed loop). In addition, the current cancellation device 10 connects two connection points (intersections) Po1 and Po2 between the connection line forming the closed loop Lo5 and the connection line forming the closed loop Lo6, and injects a cancellation signal Sk into the connection line forming the closed loop Lo6 as the load connection line L.

[0065] Next, the operation of the impedance measuring device 1B will be described. The measurement process for measuring the internal impedance Zb of the battery Bat as the measurement target is the same as that of the impedance measuring device 1, so duplicated explanations will be omitted and only the different processes will be described. First, prior to the start of measurement, both output terminals of the AC bipolar power supply 24 are connected to the connection points Po1 and Po2. In this case, both output terminals of the AC bipolar power supply 24 may be connected to the connection points Po1 and Po2 directly, or both output terminals of the AC bipolar power supply 24 may be connected to the connection points Po1 and Po2 using probes (not shown). At the start of measurement, the AC bipolar power supply 24 is controlled by the processing unit 5 to change the period of the AC voltage of the internal AC voltage source and to output an AC signal generated by high-speed high-voltage amplification as the measurement AC signal Sac. At this time, an AC current Iac based on the AC signal Sac is supplied to both closed loops Lo5 and Lo6.

[0066] At this time, similarly to the current cancellation device 10 in the impedance measuring device 1, a cancellation signal Sk output from the inverting amplifier circuit 43 is supplied between both ends of the winding W1, generating a magnetic flux based on the cancellation signal Sk in the magnetic core Mc1, and a cancellation current Ik with a current value corresponding to the magnitude of the magnetic flux is supplied as a normal-mode signal to the load connection line L (closed loop Lo6). As a result, in the load connection line L, the AC current Iac and the noise current In cancel out the cancellation current Ik, which is opposite in phase to but has the same current level as the AC current Iac and the noise current In, thereby sufficiently reducing the current levels of the AC current Iac and the noise current In flowing through the load connection line L (closed loop Lo6). Therefore, the only AC current flowing through the battery Bat is the AC current Iac flowing through the closed loop Lo5 consisting of the battery Bat and the AC current supply circuit 21. Next, in the impedance measuring device 1B as well, the processing unit 5 performs calculation processing (measurement processing) of the internal impedance Zb, similarly to the impedance measuring device 1.

[0067] Next, an impedance measuring device 1C will be described as an "impedance measuring device." As shown in Fig. 6, the impedance measuring device 1C is configured with a measuring unit 2, a non-contact current sensor 3, a cancellation signal injection unit 4, a processing unit 5, an output unit 6, and a bypass capacitor Cb, and, like the impedance measuring device 1, measures the internal impedance Zb of the battery Bat based on the current detection signal S1 and the voltage detection signal S2.

[0068] The bypass capacitor Cb is composed of a multilayer capacitor having a capacitance of, for example, about 100 μF so that the impedance is sufficiently small for the AC signal Sac and switching noise. In this case, in the impedance measurement system using the impedance measuring device 1C, the battery Bat and the bypass capacitor Cb are connected by a connection line to form a closed loop Lo7 (first closed loop), and the bypass capacitor Cb and the load Load are connected by a connection line to form a closed loop Lo8 (second closed loop). The current cancellation device 10 connects two connection points Po1, Po2 between the connection line that forms the closed loop Lo7 and the connection line that forms the closed loop Lo8, and supplies a cancellation signal Sk using the connection line that forms the closed loop Lo8 as the load connection line L.

[0069] Next, the operation of the impedance measuring device 1C will be described. Note that the measurement process for measuring the internal impedance Zb of the battery Bat as the measurement target is the same as that of the impedance measuring device 1, so duplicated explanations will be omitted and different processes will be described. First, before the start of measurement, both output parts of the bypass capacitor Cb are connected to the connection points Po1 and Po2. In this case, both output parts of the bypass capacitor Cb may be directly connected to the connection points Po1 and Po2, or both output parts of the bypass capacitor Cb may be connected to the connection points Po1 and Po2 using probes (not shown).

[0070] In this impedance measuring device 1C, similarly to the impedance measuring device 1, the processing unit 5 controls the AC current supply circuit 21 of the measuring unit 2 to generate an AC signal Sac. The AC current supply circuit 21 supplies the generated AC signal Sac across the battery Bat via the probes P1 and P2. In this case, an AC current Iac based on the AC signal Sac flows through a closed loop Lo1 consisting of the battery Bat, the load Load, and the load connection line L connecting the battery Bat and the load Load; a closed loop Lo7 consisting of the battery Bat and the bypass capacitor Cb and the connection line connecting the battery Bat and the bypass capacitor Cb; and a closed loop Lo2 consisting of the probe P1, the battery Bat, the probe P2, and the circuit within the AC current supply circuit 21. However, because the impedance of the bypass capacitor Cb relative to the frequency of the AC current Iac (AC signal Sac) is sufficiently small, a nearly short-circuit state is formed between the connection points Po1 and Po2 in terms of AC. Therefore, almost no AC current Iac flows through the closed loops Lo1 and Lo7, but only through the closed loop Lo2. As a result, the only AC current flowing through the battery Bat is the AC current Iac flowing through the closed loop Lo2. Furthermore, even if switching noise is generated in the load Load, the impedance of the bypass capacitor Cb relative to the frequency of the noise current In (noise signal) is sufficiently small, so that the connection points Po1 and Po2 are almost short-circuited in terms of AC. Therefore, the noise current In based on the switching noise generated in the load Load hardly flows through the closed loop Lo1, and hardly flows through the closed loop Lo8 consisting of the bypass capacitor Cb and the load Load and the connection line connecting the bypass capacitor Cb and the load Load.

[0071] At this time, similarly to the current cancellation device 10 in the impedance measuring device 1, a cancellation signal Sk output from the inverting amplifier circuit 43 is supplied between both ends of the winding W1. This generates a magnetic flux based on the cancellation signal Sk in the magnetic core Mc1, and a cancellation current Ik with a current value corresponding to the magnitude of the magnetic flux is supplied as a normal-mode signal to the load connection line L (closed loop Lo8). As a result, in the load connection line L, the AC current Iac and the noise current In, whose current levels have been sufficiently reduced by the bypass capacitor Cb, cancel out the cancellation current Ik, which has the same current level but is in opposite phase to the AC current Iac and the noise current In. This further sufficiently reduces the current levels of the AC current Iac and the noise current In flowing through the load connection line L (closed loop Lo8). Therefore, the only AC current flowing through the battery Bat is the AC current Iac flowing through the closed loop Lo2. Next, in the impedance measuring device 1C as well, the processing unit 5 performs calculation processing (measurement processing) of the internal impedance Zb, similarly to the impedance measuring device 1.

[0072] Next, an impedance measuring device 1D will be described as an "impedance measuring device." As shown in Fig. 7, the impedance measuring device 1D is configured to include a measurement unit 2C, a non-contact current sensor 3, a cancellation signal injection unit 4, a processing unit 5, and an output unit 6, and measures the internal impedance Zb of the battery Bat based on a current detection signal S1 and a voltage detection signal S2, similar to the impedance measuring device 1. In this case, the measurement unit 2C includes an AC voltage detection circuit 22, and, instead of the AC current supply circuit 21 in the impedance measuring device 1, is configured to include an AC signal generation circuit 21A, a supply circuit 25, and a non-contact current sensor 26.

[0073] The AC signal generation circuit 21A constitutes an "AC signal generation circuit" and, together with the supply circuit 25, constitutes a "measurement signal supply unit." The AC signal generation circuit 21A is configured similarly to the AC current supply circuit 21 in terms of the configuration for generating the AC signal Sac, but differs from the AC current supply circuit 21 only in the configuration for outputting the generated AC signal Sac to the supply circuit 25 and in the configuration for not measuring the current value of the AC current Iac flowing through the battery Bat. The supply circuit 25 also includes an annular magnetic core Mc2 (second magnetic core) through which a load connection line L (connection line) that connects the two connection points Po1 and Po2 and forms a closed loop Lo7 (first closed loop) is inserted, and a winding W2 (second winding) wound around the magnetic core Mc2. The AC signal Sac generated by the AC signal generation circuit 21A is supplied to both ends of the winding W2, thereby supplying the AC signal Sac to the battery Bat. In this case, magnetic core Mc2 is made of the same material as magnetic core Mc1. Non-contact current sensor 26 is a so-called clamp-type current sensor and functions as a non-contact current detection unit. This non-contact current sensor 26 has the same configuration as non-contact current sensor 3, and detects the current value of the AC current flowing through load connection line L without contacting load connection line L (core wire (conductor) of load connection line L), and outputs a current detection signal S1 indicating the current value, frequency, and phase of the detected AC current to processing unit 5.

[0074] Next, the operation of the impedance measuring device 1D will be described. Note that the measurement process itself for measuring the internal impedance Zb of the battery Bat as the measurement target is the same as that of the impedance measuring device 1, so duplicated explanations will be omitted and only the different processes will be described. First, before the start of measurement, the load connection line L is inserted into the supply circuits 25, 44, and the battery Bat and the load Load are connected by the load connection line L. Furthermore, in the same way as when the impedance measuring device 1C is used, both output parts of the bypass capacitor Cb are connected to the connection points Po1, Po2.

[0075] In this impedance measuring device 1D, the processing unit 5 controls the AC signal generating circuit 21A of the measuring unit 2 to generate an AC signal Sac and output it to the supply circuit 25. When the AC signal Sac is supplied to both ends of the winding W2 of the supply circuit 25, an AC current Iac flows through the load connection line L inserted through the magnetic core Mc2. The AC current Iac flows through a closed loop Lo1 consisting of the battery Bat, the load Load, and the load connection line L connecting the battery Bat and the load Load, and a closed loop Lo7 consisting of the battery Bat, the bypass capacitor Cb, and the connection line connecting the battery Bat and the bypass capacitor Cb. However, because the impedance of the bypass capacitor Cb relative to the frequency of the AC current Iac (AC signal Sac) is sufficiently small, a nearly short-circuit state is formed between the connection points Po1 and Po2 in terms of AC. Therefore, almost no AC current Iac flows through the closed loop Lo1, but only through the closed loop Lo7. As a result, the only AC current flowing through the battery Bat is the AC current Iac flowing through the closed loop Lo7. Furthermore, even if switching noise is generated in the load Load, the impedance of the bypass capacitor Cb relative to the frequency of the noise current In (noise signal) is sufficiently small, so that the connection points Po1 and Po2 are almost short-circuited in terms of AC. Therefore, the noise current In based on the switching noise generated in the load Load hardly flows through the closed loop Lo1, and hardly flows through the closed loop Lo8 consisting of the bypass capacitor Cb and the load Load and the connection line connecting the bypass capacitor Cb and the load Load.

[0076] At this time, similarly to the current cancellation device 10 in the impedance measuring device 1, a cancellation signal Sk output from the inverting amplifier circuit 43 is supplied between both ends of the winding W1. This generates a magnetic flux based on the cancellation signal Sk in the magnetic core Mc1, and a cancellation current Ik with a current value corresponding to the magnitude of the magnetic flux is supplied as a normal-mode signal to the load connection line L (closed loop Lo8). As a result, in the load connection line L, the AC current Iac and the noise current In, whose current levels have been sufficiently reduced by the bypass capacitor Cb, cancel out the cancellation current Ik, which has the same current level but is in opposite phase to the AC current Iac and the noise current In. This further sufficiently reduces the current levels of the AC current Iac and the noise current In flowing through the load connection line L (closed loop Lo8). Therefore, the only AC current flowing through the battery Bat is the AC current Iac flowing through the closed loop Lo7. Next, in the impedance measuring device 1D as well, the processing unit 5 performs calculation processing (measurement processing) of the internal impedance Zb, similarly to the impedance measuring device 1.

[0077] As described above, the current cancellation device 10 includes the non-contact current sensor 3 that detects current components (noise current In and AC current Iac) flowing through the load connection line L connected to the load Load without contacting the load connection line L, and the cancellation signal injection unit 4 that generates a cancellation signal Sk that cancels the current components detected by the non-contact current sensor 3 and injects the generated cancellation signal Sk into the load connection line L without contact. Therefore, even if switching noise occurs in the load Load, the current cancellation device 10 can sufficiently reduce the noise current In flowing through the load connection line L. Furthermore, even if a large current flows through the load connection line L, the current cancellation device 10 sufficiently reduces the current flowing through the load connection line L, thereby preventing a failure of the load Load caused by a current of a large value flowing.

[0078] Furthermore, in the current cancellation device 10, the cancellation signal injection unit 4 is configured to include a cancellation signal generation circuit (amplification circuit 41, phase adjustment circuit 42, and inverting amplification circuit 43) that generates a cancellation signal Sk, and an injection circuit 44 that injects the cancellation signal Sk generated by the cancellation signal generation circuit into the load connection line L, and the cancellation signal generation circuit inverts, amplifies, and phase-adjusts the current component detected by the non-contact current sensor 3, and outputs the result as a cancellation signal Sk to the injection circuit 44. Therefore, according to this current cancellation device 10, the configuration is simpler than, for example, a configuration that includes an oscillator and generates a cancellation signal that is the same signal level as but in opposite phase to the current component detected by the non-contact current sensor 3, yet can reliably cancel the current component on the load connection line L.

[0079] Furthermore, according to the current cancellation device 10, the injection circuit 44 is composed of a magnetic core Mc1 through which the load connection line L is inserted and a winding W1 wound around the magnetic core Mc1, and the cancellation signal Sk generated by the cancellation signal generation circuit (amplification circuit 41, phase adjustment circuit 42, and inverting amplification circuit 43) is supplied to both ends of the winding W1 to inject the cancellation signal Sk, thereby enabling the current component on the load connection line L to be reliably canceled despite the simple configuration.

[0080] Furthermore, according to the current cancellation device 10, by providing the gap G1 in the magnetic core Mc1, magnetic saturation of the magnetic core Mc1 can be effectively avoided even if the level of the cancellation signal Sk injected into the load connection line L is increased.

[0081] Furthermore, the impedance measuring devices 1, 1A, 1B, 1C, and 1D are each equipped with a current cancellation device 10 and are configured to include a measurement signal supply unit (AC current supply circuit 21, 21A, AC electronic load 23, or AC bipolar power supply 24) that supplies an AC signal Sac to the object to be measured (in this example, the battery Bat), an AC voltage detection circuit 22 that detects the voltage value of the AC signal Sac generated across both ends of the battery Bat and outputs a voltage detection signal S2, and a processing unit 5 that measures the impedance of the battery Bat (in this example, the internal impedance Zb) based on the current value (in this example, the current detection signal S1) of the AC signal Sac supplied from the measurement signal supply unit to the battery Bat and the voltage value of the AC signal Sac indicated by the voltage detection signal S2. Therefore, according to the impedance measuring devices 1, 1A, 1B, 1C, and 1D, the influence of the noise current In on the current detection signal S1 and the voltage detection signal S2 can be avoided, and the ratio (S / N) of the signal level (S) to the noise level (N) of the current detection signal S1 and the voltage detection signal S2 can be increased, thereby enabling the internal impedance Zb to be measured with high accuracy in the calculation process (measurement process) of the internal impedance Zb performed by the calculation circuit 57. Furthermore, according to the impedance measuring devices 1, 1A, 1B, 1C, and 1D, even if the level of the AC signal Sac supplied to the load connection line L (the current value of the AC current Iac) is increased, the current cancellation device 10 sufficiently reduces the AC current Iac flowing through the closed loop Lo1, and therefore it is possible to avoid a failure of the load Load caused by the flow of a large current value of the AC current Iac.

[0082] Furthermore, according to the impedance measuring device 1, 1C, the battery Bat and the load Load are connected by a load connection line L to form a closed loop Lo1, and the AC current supply circuit 21 supplies an AC signal Sac between both ends of the battery Bat, which is a simple configuration, so the impedance measuring device 1, 1C can be constructed inexpensively.

[0083] Furthermore, according to the impedance measuring device 1A, the measurement signal supply unit is constituted by the AC electronic load 23, the battery Bat and the AC electronic load 23 are connected by a connection line to form a closed loop Lo3, and the AC electronic load 23 and the load Load are connected by a connection line to form a closed loop Lo4, and the current cancellation device 10 connects two connection points Po1, Po2 between the connection line forming the closed loop Lo3 and the connection line forming the closed loop Lo4, and supplies a cancellation signal Sk to the connection line forming the closed loop Lo4 as the load connection line L, thereby allowing the AC electronic load 23 to increase the signal level of the AC signal Sac, and therefore increasing the ratio (S / N) of the signal level (S) to the noise level (N) of the current detection signal S1 and the voltage detection signal S2.As a result, the internal impedance Zb can be measured with high accuracy in the calculation process (measurement process) of the internal impedance Zb performed by the calculation circuit 57.

[0084] Furthermore, according to the impedance measuring device 1B, the measurement signal supply unit is constituted by the AC bipolar power supply 24, the battery Bat and the AC bipolar power supply 24 are connected by a connection line to form a closed loop Lo5, and the AC bipolar power supply 24 and load Load are connected by a connection line to form a closed loop Lo6, and the current cancellation device 10 connects two connection points Po1, Po2 between the connection line forming the closed loop Lo5 and the connection line forming the closed loop Lo6, and supplies a cancellation signal Sk using the connection line forming the closed loop Lo6 as the load connection line L, so that the signal level of the AC signal Sac can be increased by the AC bipolar power supply 24, and the ratio (S / N) of the signal level (S) to the noise level (N) of the current detection signal S1 and the voltage detection signal S2 can be increased.As a result, the internal impedance Zb can be measured with high accuracy in the calculation process (measurement process) of the internal impedance Zb performed by the calculation circuit 57.

[0085] Furthermore, the impedance measuring devices 1C and 1D are equipped with a bypass capacitor Cb, the battery Bat and the bypass capacitor Cb are connected by a connection line to form a closed loop Lo7, and the bypass capacitor Cb and the load Load are connected by a connection line to form a closed loop Lo8, and the current cancellation device 10 connects two connection points Po1 and Po2 between the connection line forming the closed loop Lo7 and the connection line forming the closed loop Lo8, and supplies a cancellation signal Sk to the connection line forming the closed loop Lo8 as the load connection line L. Therefore, according to the impedance measuring devices 1C and 1D, the bypass capacitor Cb sufficiently reduces the noise current In flowing through the closed loop Lo1, so that the influence of the noise current In on the current detection signal S1 and the voltage detection signal S2 is reliably avoided, and as a result, the internal impedance Zb can be measured more accurately in the calculation process (measurement process) of the internal impedance Zb performed by the calculation circuit 57. Furthermore, according to the impedance measuring device 1C (or impedance measuring device 1D), the bypass capacitor Cb creates an almost AC short circuit between the connection points Po1 and Po2, causing the AC current Iac to flow only through the closed loop Lo2 (or closed loop Lo7). This makes it possible to increase the current value of the AC current Iac supplied to the battery Bat. As a result, in the calculation process (measurement process) of the internal impedance Zb performed by the calculation circuit 57, the ratio (S / N) of the signal level (S) to the noise level (N) can be increased, and the internal impedance Zb can be measured more accurately.

[0086] In the impedance measuring device 1D, the measurement signal supply unit (in this example, the AC signal generation circuit 21A and the supply circuit 25) supplies an AC signal Sac in a contactless manner to a connection line that connects the two connection points Po1 and Po2 and forms a closed loop Lo7. In the impedance measuring device 1D, the measurement signal supply unit (in this example, the AC signal generation circuit 21A and the supply circuit 25) includes the AC signal generation circuit 21A that generates the AC signal Sac and the supply circuit 25 that supplies the generated AC signal Sac, and the supply circuit 25 is composed of an annular magnetic core Mc2 through which the connection line that connects the two connection points Po1 and Po2 and forms the closed loop Lo7 is inserted, and a winding W2 wound around the magnetic core Mc2, and the AC signal Sac generated by the AC signal generation circuit 21A is supplied to both ends of the winding W2, thereby supplying the AC signal Sac to the load connection line L in a contactless manner. Therefore, according to this impedance measuring device 1D, even if the connection line forming the closed loop Lo7 is made of an insulating coated wire, the AC signal Sac can be supplied without stripping the coating of the insulating coated wire.

[0087] Furthermore, according to the impedance measuring device 1D, by providing a gap G2 in the magnetic core Mc2, magnetic saturation of the magnetic core Mc2 can be effectively avoided even if the level of the AC signal Sac supplied to the load connection line L (current value of the AC current Iac) is increased.

[0088] Furthermore, according to the impedance measuring devices 1, 1A, 1B, 1C, and 1D, the calculation circuit 57 of the processing unit 5 calculates the internal impedance Zb of the battery Bat to be measured based on the in-phase and quadrature components of the AC signal Sac (current detection signal S1) output from the quadrature detection circuit 55 and the in-phase and quadrature components of the AC signal Sac (voltage detection signal S2) output from the quadrature detection circuit 56. 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 Sac supplied to the load connection line L is small.

[0089] Furthermore, according to the impedance measuring devices 1, 1A, 1B, 1C, and 1D, the clock signal CL1, which is the operating clock of each A / D conversion circuit 51 to 53, and the clock signal CL2, which is the operating clock of the final-stage Class D amplifier circuit in the inverting amplifier circuit 43, are synchronized with each other. Therefore, even if the clock signal CL2 of the inverting amplifier circuit 43 is superimposed on the load connection line L or propagates via radio waves, the noise caused by the clock signal CL2 is sufficiently reduced by each A / D conversion circuit 51 to 53, and therefore the internal impedance Zb can be measured with even greater accuracy in the calculation process (measurement process) of the internal impedance Zb performed by the calculation circuit 57.

[0090] The configurations of the "current cancellation device" and "impedance measurement device" are not limited to the above examples and can be modified as appropriate. For example, as shown in FIG. 8, an injection circuit 44A can be configured using an air-core coil AC instead of the injection circuit 44. In this case, the load connection line L is inserted into the injection circuit 44A, and the cancellation signal Sk generated by the inverting amplifier circuit 43 is supplied to both ends of the air-core coil AC, thereby supplying the cancellation signal Sk to the load connection line L. The current cancellation device 10 and impedance measurement devices 1, 1A, 1B, 1C, and 1D having this configuration can reliably inject the cancellation signal Sk into the load connection line L despite their simple configuration.

[0091] 9, an injection circuit 25A can be configured using an air-core coil AC instead of the injection circuit 25. In this case, a connection line (load connection line L) that connects the two connection points Po1 and Po2 and forms a closed loop Lo7 is inserted through the supply circuit 25A, and the AC signal Sac generated by the AC current supply circuit 21A is supplied to both ends of the air-core coil AC, thereby supplying the AC signal Sac (AC current Iac) to the battery Bat. An impedance measuring device 1D having this configuration can reliably supply the AC signal Sac to the load connection line L despite its simple configuration.

[0092] The current cancellation device 10 is not limited to application to impedance measurement devices, but can be applied to various measuring instruments that require cancellation of a current component flowing through a load connection line L. The impedance measurement device is not limited to measuring the internal impedance Zb of the battery Bat or the internal impedance of the battery cells of the battery Bat, but can also measure the impedance of various measurement objects, including various batteries. For example, when the measurement object is a water electrolysis cell that produces hydrogen by electrolyzing water, the water electrolysis cell and a power supply for the water electrolysis cell, instead of a load Load, are connected via a load connection line L in a closed loop, and the internal impedance of the water electrolysis cell is measured by connecting a pair of probes to the anode and cathode of the water electrolysis cell.

[0093] In addition, instead of the non-contact current sensor 3 or the non-contact current sensor 26, a configuration can be adopted in which a current transformer, a current detection resistor, or the like is arranged in the load connection line L to detect the current component or the current value of the AC current Iac.

[0094] Furthermore, in the impedance measuring devices 1, 1A, 1B, 1C, and 1D, examples have been described in which impedances such as the internal impedance Zb of the battery Bat are calculated using digital processing, but a configuration can also be adopted in which the impedance is determined by analog calculation using an analog circuit based on the AC reference signal Sr, the current detection signal S1, and the voltage detection signal S2.

[0095] Although not shown, in the impedance measuring devices 1, 1A, 1B, 1C, and 1D, when there is a risk that a DC current from the battery Bat will flow through the load connection line L and cause magnetic saturation of the non-contact current sensor 3 or the non-contact current sensor 26, the devices may be configured to include a DC current cancellation circuit that cancels out the DC current flowing through the load connection line L. [Industrial Applicability]

[0096] According to the present invention ,negativeThe level of the current component flowing through the load connection line connected to the load can be reduced, and load failure can be avoided when the level of the AC signal supplied to the load connection line is increased. Ruden An impedance measuring device equipped with a current canceling device can reliably and accurately measure the impedance of a measurement object connected in series to a load connection line. Nai The present invention can be widely applied to impedance measuring devices that measure impedance. [Explanation of symbols]

[0097] 1,1A~1D Impedance measuring device 2,2A~2C measurement part 21,21A AC current supply circuit 22 AC voltage detection circuit 23 AC electronic load 24 AC Bipolar Power Supply 25,25A injection circuit 26 Non-contact current sensor 3. Non-contact current sensor 4 Cancellation signal injection section 41 Amplification circuit 42 Phase adjustment circuit 43 Inverting amplifier circuit 44,44A injection circuit 5 Processing section 51 A / D conversion circuit 52 A / D conversion circuit 53 A / D conversion circuit 54 Phase shift circuit 55 Quadrature detection circuit 56 Quadrature detection circuit 57 Arithmetic circuit 58 Internal Memory 59 Clock Generation Circuit 6 Output section AC Air Core Coil Bat battery CL1, CL2 clock signals G1,G2 gap Ik Cancellation current Load Load Mc1, Mc2 magnetic core S1 Current detection signal S2 voltage detection signal Sk cancellation signal Sn noise signal Sr AC reference signal Zb Internal Impedance W1, W2 winding

Claims

1. An impedance measuring device comprising a current cancellation device having a current component detection unit that detects a current component flowing through a load connection line connected to a load without contacting the load connection line, and a cancellation signal injection unit that generates a cancellation signal that cancels the current component detected by the current component detection unit and injects the generated cancellation signal into the load connection line without contacting the load connection line, and that measures the impedance of a measurement object that is connected in series to the load connection line, a measurement signal supply unit that generates an AC signal for measurement and supplies the AC signal to the measurement object; a voltage detection unit that detects a voltage value of an AC voltage occurring across both ends of the measurement object by contacting the both ends and outputs a voltage detection signal; a processing unit that receives the voltage detection signal and measures the impedance of the object to be measured based on the current value of the AC signal supplied from the measurement signal supply unit to the object to be measured and the voltage value of the AC voltage indicated by the voltage detection signal, The measurement object is a battery, the measurement signal supply unit is configured with an AC electronic load that converts the stored power of the battery into AC, and supplies an AC signal generated by the AC conversion as the measurement AC signal; the measurement object and the measurement signal supply unit are connected by a connection line to form a first closed loop, and the measurement signal supply unit and the load are connected by a connection line to form a second closed loop; The current cancellation device is an impedance measurement device that connects two connection points of the connection line that forms the first closed loop and the connection line that forms the second closed loop, and injects the cancellation signal using the connection line that forms the second closed loop as the load connection line.

2. An impedance measuring device comprising a current cancellation device having a current component detection unit that detects a current component flowing through a load connection line connected to a load without contacting the load connection line, and a cancellation signal injection unit that generates a cancellation signal that cancels the current component detected by the current component detection unit and injects the generated cancellation signal into the load connection line without contacting the load connection line, and that measures the impedance of a measurement object that is connected in series to the load connection line, a measurement signal supply unit that generates an AC signal for measurement and supplies the AC signal to the measurement object; a voltage detection unit that detects a voltage value of an AC voltage occurring across both ends of the measurement object by contacting the both ends and outputs a voltage detection signal; a processing unit that receives the voltage detection signal and measures the impedance of the object to be measured based on the current value of the AC signal supplied from the measurement signal supply unit to the object to be measured and the voltage value of the AC voltage indicated by the voltage detection signal, the measurement signal supply unit is configured with a bipolar power supply that generates the AC signal, the measurement object and the measurement signal supply unit are connected by a connection line to form a first closed loop, and the measurement signal supply unit and the load are connected by a connection line to form a second closed loop; The current cancellation device is an impedance measurement device that connects two connection points of the connection line that forms the first closed loop and the connection line that forms the second closed loop, and injects the cancellation signal using the connection line that forms the second closed loop as the load connection line.

3. An impedance measuring device comprising a current cancellation device having a current component detection unit that detects a current component flowing through a load connection line connected to a load without contacting the load connection line, and a cancellation signal injection unit that generates a cancellation signal that cancels the current component detected by the current component detection unit and injects the generated cancellation signal into the load connection line without contacting the load connection line, and that measures the impedance of a measurement object that is connected in series to the load connection line, a measurement signal supply unit that generates an AC signal for measurement and supplies the AC signal to the measurement object; a voltage detection unit that detects a voltage value of an AC voltage occurring across both ends of the measurement object by contacting the both ends and outputs a voltage detection signal; a processing unit that receives the voltage detection signal and measures the impedance of the object to be measured based on the current value of the AC signal supplied from the measurement signal supply unit to the object to be measured and the voltage value of the AC voltage indicated by the voltage detection signal; a bypass capacitor; the object to be measured and the bypass capacitor are connected by a connection line to form a first closed loop, and the bypass capacitor and the load are connected by a connection line to form a second closed loop; The current cancellation device is an impedance measurement device that connects two connection points of the connection line that forms the first closed loop and the connection line that forms the second closed loop, and injects the cancellation signal using the connection line that forms the second closed loop as the load connection line.

4. 4. The impedance measuring device according to claim 3, wherein the measurement signal supplying section supplies the AC signal in a non-contact manner to the connection line that connects the two connection points and forms the first closed loop.

5. the measurement signal supply unit includes an AC signal generation circuit that generates the AC signal, and a supply circuit that supplies the AC signal generated by the AC signal generation circuit, 5. The impedance measuring device according to claim 4, wherein the supply circuit is composed of an annular second magnetic core through which the connection line that connects the two connection points and forms the first closed loop is inserted, and a second winding wound around the second magnetic core, and the AC signal generated by the AC signal generating circuit is supplied to both ends of the second winding to supply the AC signal.

6. 6. The impedance measuring device according to claim 5, wherein the second magnetic core is provided with a gap.

7. the measurement signal supply unit includes an AC signal generation circuit that generates the AC signal, and a supply circuit that supplies the AC signal generated by the AC signal generation circuit, The impedance measuring device of claim 4, wherein the supply circuit is composed of an air-core coil through which the connection line that connects the two connection points and forms the first closed loop is inserted, and the AC signal generated by the AC signal generating circuit is supplied to both ends of the air-core coil, thereby supplying the AC signal to the object to be measured.

8. 4. The impedance measuring device according to claim 3, wherein the measurement signal supplying section supplies the AC signal between both ends of the object to be measured.

9. An impedance measuring device comprising a current cancellation device having a current component detection unit that detects a current component flowing through a load connection line connected to a load without contacting the load connection line, and a cancellation signal injection unit that generates a cancellation signal that cancels the current component detected by the current component detection unit and injects the generated cancellation signal into the load connection line without contacting the load connection line, and that measures the impedance of a measurement object that is connected in series to the load connection line, a measurement signal supply unit that generates an AC signal for measurement and supplies the AC signal to the measurement object; a voltage detection unit that detects a voltage value of an AC voltage occurring across both ends of the measurement object by contacting the both ends and outputs a voltage detection signal; a processing unit that receives the voltage detection signal and measures the impedance of the object to be measured based on the current value of the AC signal supplied from the measurement signal supply unit to the object to be measured and the voltage value of the AC voltage indicated by the voltage detection signal; a current detection unit that detects the current value of the AC signal supplied to the object to be measured and outputs the detected current value to the processing unit as a current detection signal; the processing unit includes a first quadrature detection circuit that receives the AC signal and performs quadrature detection on the current detection signal to generate in-phase and quadrature components of an AC current, and a second quadrature detection circuit that receives the AC signal and performs quadrature detection on the voltage detection signal to generate in-phase and quadrature components of an AC voltage, a calculation circuit that calculates the impedance of the object to be measured based on the in-phase component and the quadrature component of the AC current output from the first quadrature detection circuit and the in-phase component and the quadrature component of the AC voltage output from the second quadrature detection circuit, the cancellation signal injection unit of the current cancellation device includes a class D amplifier circuit as a final stage, and injects the cancellation signal amplified by the class D amplifier circuit; an A / D conversion circuit that performs analog-to-digital conversion on the current detection signal detected by the current detection unit and outputs the converted current data to the processing unit, and an A / D conversion circuit that performs analog-to-digital conversion on the voltage detection signal detected by the voltage detection unit and outputs the converted voltage data to the processing unit, an impedance measuring device in which each of the A / D conversion circuits performs the analog-to-digital conversion in synchronization with an operation clock common to an operation clock of the class D amplifier circuit of the cancellation signal injection unit;

10. the object to be measured and the load are connected by the load connection line to form a closed loop; 10. The impedance measuring device according to claim 1, wherein the measurement signal supplying section supplies the AC signal between both ends of the object to be measured.

11. the cancellation signal injection unit is configured to include a cancellation signal generation circuit that generates the cancellation signal, and an injection circuit that injects the cancellation signal generated by the cancellation signal generation circuit into the load connection line; 10. The impedance measuring device according to claim 1, wherein the cancellation signal generating circuit amplifies and phase-adjusts the current component detected by the current component detecting section and outputs the resultant as the cancellation signal to the injection circuit.

12. 12. The impedance measuring device according to claim 11, wherein the injection circuit is composed of an annular first magnetic core through which the load connection line is inserted and a first winding wound around the first magnetic core, and the cancellation signal generated by the cancellation signal generation circuit is supplied to both ends of the first winding to inject the cancellation signal.

13. 13. The impedance measuring device according to claim 12, wherein the first magnetic core is provided with a gap.

14. the cancellation signal injection unit is configured to include a cancellation signal generation circuit that generates the cancellation signal, and an injection circuit that injects the cancellation signal generated by the cancellation signal generation circuit into the load connection line; 12. The impedance measuring device according to claim 11, wherein the injection circuit is composed of an air-core coil through which the load connection line is inserted, and the cancellation signal generated by the cancellation signal generation circuit is supplied to both ends of the air-core coil, thereby injecting the cancellation signal into the load connection line.

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