Drive measurement circuit and drive measurement method

Abstract

A drive measurement circuit (2) comprises a current measuring unit (21) that measures the current of a battery (B1) and the current of a battery (B2), a voltage measuring unit (20) that measures the voltage of the battery (B1) and the voltage of the battery (B2), an alternating current detecting unit (22) that, on the basis of the measurement results from the voltage measuring unit (20) and the measurement results from the current measuring unit (21), measures an AC voltage and an AC current corresponding to a measuring frequency and outputs the same to an MCU (200), and a drive control unit (23) that causes an AC current to flow to the battery (B1) and the battery (B2) by driving a plurality of switching elements (11, 12) so as to periodically change the state of movement of a current passing through an inductor (14) in accordance with the measurement frequency, wherein the drive control unit (23) repeats causing and not causing the AC current to flow to the battery (B1) and the battery (B2), and in the repetitions, switches the waveform of the initial pulse when the AC current starts to flow from among two or more types of waveforms.

Description

Drive Measurement Circuit and Drive Measurement Method

[0001] The present disclosure relates to a drive measurement circuit and a drive measurement method for controlling an impedance measurement device that measures the AC impedance of a plurality of batteries connected in series.

[0002] Patent Document 1 discloses a technique for supplying an alternating current to a battery composed of a plurality of battery cells, multiplying and integrating the voltages and currents of the plurality of battery cells supplied with the alternating current by sine waves and cosine waves having a phase difference of 90° from each other to convert them into complex numbers, and measuring complex voltages and complex currents, that is, measuring the AC impedance of the battery cells.

[0003] International Publication No. 2020 / 003841

[0004] During the running or charging of a vehicle equipped with an impedance measurement device, it is necessary to measure and monitor the cell voltage at a cycle of 10 ms to 20 ms. In order to avoid the influence of voltage fluctuations caused by the application of current in AC impedance measurement, that is, EIS (Electrochemical Impedance Spectroscopy) measurement, EIS measurement is intermittently performed, the measurement results are integrated, and the integrated measurement results are averaged. Since there is an influence of the transient response of the voltage immediately after the start of the application of the current for EIS measurement, it is conceivable to perform EIS measurement by excluding the section where the influence of the transient response exists from the measurement section of EIS as the steady state section before EIS measurement, but there is a problem that the measurement time of EIS measurement becomes short.

[0005] Therefore, the present disclosure provides a drive measurement circuit and the like that can ensure the measurement time of EIS measurement.

[0006] The drive measurement circuit according to this disclosure is a drive measurement circuit for controlling an impedance measuring device for measuring the AC impedance of a first battery and a second battery connected in series, wherein the impedance measuring device comprises an inductor for storing or releasing electrical energy, a switching circuit consisting of a plurality of switching elements for intermittently moving current between the first battery and the second battery via the inductor, and current detection means for detecting the current of the first battery and the current of the second battery, and the drive measurement circuit comprises a current measuring unit for measuring the current of the first battery and the current of the second battery based on the detection result of the current detection means, and a voltage measuring unit for measuring the voltage of the first battery and the voltage of the second battery, The AC detection unit receives a measurement instruction signal including information on the measurement frequency from a higher-level system having a function to calculate AC impedance, and measures an AC voltage and AC current corresponding to the measurement frequency based on the measurement results of the voltage measurement unit and the measurement results of the current measurement unit, and outputs them to the higher-level system. The drive control unit drives a plurality of switching elements to periodically change the state of current movement through the inductor according to the measurement frequency, thereby supplying the AC current to the first battery and the second battery. The drive control unit repeatedly switches between supplying and not supplying the AC current to the first battery and the second battery, and in each repetition, switches the waveform of the first pulse when the AC current is started from two or more types of waveforms.

[0007] The drive measurement circuit according to this disclosure is a drive measurement circuit for controlling an impedance measuring device for measuring the AC impedance of a first battery and a second battery connected in series, wherein the impedance measuring device comprises an inductor for storing or releasing electrical energy, a switching circuit consisting of a plurality of switching elements for intermittently moving current between the first battery and the second battery via the inductor, and current detection means for detecting the current of the first battery and the current of the second battery, and the drive measurement circuit comprises a current measuring unit for measuring the current of the first battery and the current of the second battery based on the detection result of the current detection means, and a voltage measuring unit for measuring the voltage of the first battery and the voltage of the second battery, The AC detection unit receives a measurement instruction signal including information on the measurement frequency from a higher-level system having a function to calculate AC impedance, and measures an AC voltage and AC current corresponding to the measurement frequency based on the measurement results of the voltage measurement unit and the measurement results of the current measurement unit, and outputs them to the higher-level system. The drive control unit drives a plurality of switching elements to periodically change the state of current movement through the inductor according to the measurement frequency, thereby supplying the AC current to the first battery and the second battery. The drive control unit repeatedly supplies the AC current to the first battery and the second battery and does not supply it, and the AC detection unit varies the timing at which it starts measuring the AC voltage and the AC current during each repetition.

[0008] The drive measurement method according to this disclosure is a drive measurement method for controlling an impedance measuring device for measuring the AC impedance of a first battery and a second battery connected in series, wherein the impedance measuring device comprises an inductor for storing or releasing electrical energy, a switching circuit consisting of a plurality of switching elements for intermittently moving current between the first battery and the second battery through the inductor, and current detection means for detecting the current of the first battery and the current of the second battery, and the drive measurement method comprises a power receiving step of receiving a measurement instruction signal including information on the measurement frequency from a higher-level system having a function for calculating AC impedance, and the plurality of switches for periodically changing the state of current movement through the inductor according to the measurement frequency. The device includes a drive step of driving a pulsating element to supply alternating current to the first battery and the second battery; a current measurement step of measuring the current of the first battery and the current of the second battery based on the detection result of the current detection means; a voltage measurement step of measuring the voltage of the first battery and the voltage of the second battery; and an AC detection step of measuring an AC voltage and an AC current corresponding to the measurement frequency based on the measurement result of the voltage measurement step and the measurement result of the current measurement step, and outputting them to the higher-level system, wherein the drive step repeatedly supplies the alternating current to the first battery and the second battery and does not, and in each repetition, the waveform of the first pulse when the alternating current is started is switched from two or more types of waveforms.

[0009] The drive measurement method according to this disclosure is a drive measurement method for controlling an impedance measuring device for measuring the AC impedance of a first battery and a second battery connected in series, wherein the impedance measuring device comprises an inductor for storing or releasing electrical energy, a switching circuit consisting of a plurality of switching elements for intermittently moving current between the first battery and the second battery through the inductor, and current detection means for detecting the current of the first battery and the current of the second battery, and the drive measurement method comprises a power receiving step of receiving a measurement instruction signal including information on the measurement frequency from a higher-level system having a function for calculating AC impedance, and the plurality of switching elements for periodically changing the state of current movement through the inductor according to the measurement frequency The device includes a drive step of driving an element to supply alternating current to the first battery and the second battery; a current measurement step of measuring the current of the first battery and the current of the second battery based on the detection result of the current detection means; a voltage measurement step of measuring the voltage of the first battery and the voltage of the second battery; and an AC detection step of measuring an AC voltage and an AC current corresponding to the measurement frequency based on the measurement result of the voltage measurement step and the measurement result of the current measurement step, and outputting them to the higher-level system, wherein the drive step repeatedly supplies and does not supply the AC current to the first battery and the second battery, and the AC detection step differs the timing of starting the measurement of the AC voltage and the AC current in each repetition.

[0010] These comprehensive or specific embodiments may be implemented as a system, method, integrated circuit, computer program, or recording medium such as a computer-readable CD-ROM, or as any combination of a system, method, integrated circuit, computer program, and recording medium.

[0011] According to one aspect of this disclosure, a drive measurement circuit, etc., can be used to ensure sufficient measurement time for EIS measurement.

[0012] This is a configuration diagram showing an example of a battery monitoring system according to Embodiment 1. This is a circuit configuration diagram showing an example of a voltage measurement unit, current measurement unit, and AC detection unit of a battery monitoring system according to Embodiment 1. This is a circuit configuration diagram showing an example of a drive control unit according to Embodiment 1. This is a timing chart showing an example of the operation of the drive control unit according to Embodiment 1. This is a flowchart showing an example of the operation of a battery monitoring system according to Embodiment 1. This is a diagram showing an example of the AC impedance measurement sequence in Embodiment 1. This is a diagram showing an example of the current and voltage waveforms of a battery in Embodiment 1. This is a diagram showing another example of the AC impedance measurement sequence in Embodiment 1. This is a diagram showing another example of the current and voltage waveforms of a battery in Embodiment 1. This is a configuration diagram showing an example of a battery monitoring system according to Embodiment 2. This is a flowchart showing an example of the operation of a battery monitoring system according to Embodiment 2. This is a diagram showing an example of the current and voltage waveforms of a battery in Embodiment 2. This is a configuration diagram showing an example of a battery monitoring system according to Embodiment 3. This is a flowchart showing an example of the operation of a battery monitoring system according to Embodiment 3. This is a diagram showing an example of the current and voltage waveforms of a battery in Embodiment 3. This is a flowchart showing an example of a drive measurement method according to another embodiment.

[0013] The embodiments will be described in detail below with reference to the drawings.

[0014] The embodiments described below are all general or specific examples. The numerical values, shapes, materials, components, arrangement and connection configurations of components, steps, and the order of steps shown in the following embodiments are examples only and are not intended to limit this disclosure.

[0015] (Embodiment 1) The drive measurement circuit according to Embodiment 1 will be described below.

[0016] Figure 1 is a configuration diagram showing an example of a battery monitoring system 100 according to Embodiment 1. In addition to the battery monitoring system 100, batteries B1 and B2 are also shown in Figure 1.

[0017] The battery monitoring system 100 includes an impedance measuring device 1 and an MCU (Micro Controller Unit) 200. The impedance measuring device 1 is a device that measures the AC impedance of batteries B1 and B2 connected in series using an EIS (Electron Indication System). Battery B1 is an example of a first battery, and battery B2 is an example of a second battery. For example, batteries B1 and B2 are battery packs composed of two or more battery cells connected in series. For example, batteries B1 and B2 are rechargeable secondary batteries such as lithium-ion batteries, and battery B1 is located on the higher potential side than battery B2. The MCU 200 has a function to calculate AC impedance. The MCU 200 is an example of a higher-level system. The MCU 200 includes a repeat measurement control unit 203.

[0018] The impedance measuring device 1 includes an inductor 14 that stores or releases electrical energy, a switching circuit consisting of a plurality of switching elements that intermittently transfer electrical energy between battery B1 and battery B2 via the inductor 14, a current detection means for detecting the current of battery B1 and the current of battery B2, and a drive measurement circuit 2. The drive measurement circuit 2 may be provided separately from the impedance measuring device 1. Similarly, in each embodiment described later, the impedance measuring device and the drive measurement circuit may be provided separately.

[0019] The switching circuit includes, as a plurality of switching elements, a first switching element 11 that forms a first loop together with the battery B1 and the inductor 14, and a second switching element 12 that forms a second loop together with the battery B2 and the inductor 14. For example, the switching circuit has a current interruption means 13 connected in series with the inductor 14. For example, the current detection means includes a detection resistor 15 connected between the battery B1 and the first switching element 11, and a detection resistor 16 connected between the battery B2 and the second switching element 12. The current of the battery B1 can be detected by detecting the current flowing through the detection resistor 15, and the current of the battery B2 can be detected by detecting the current flowing through the detection resistor 16.

[0020] The first switching element 11 and the second switching element 12 are, for example, N-channel MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). The drain of the first switching element 11 is connected to the positive terminal of battery B1, the source of the first switching element 11 is connected to the drain of the second switching element 12, and the source of the second switching element 12 is connected to the negative terminal of battery B2. The series circuit of the current interruption means 13 and the inductor 14 is connected between the connection point between battery B1 and battery B2 and the connection point between the first switching element 11 and the second switching element 12. For example, the detection resistor 15 is connected between the positive terminal of battery B1 and the drain of the first switching element 11 to detect the charge / discharge current I1 of battery B1. For example, the detection resistor 16 is connected between the negative terminal of battery B2 and the source of the second switching element 12 to detect the charge / discharge current I2 of battery B2.

[0021] The first switching element 11 and the second switching element 12 are switching elements that conduct current when a voltage is applied to the control terminal (gate), and conduct current in the reverse direction (opposite to the arrows of currents I1 and I2 shown in Figure 1) by, for example, a body diode, and are represented as field-effect transistors as an example. In addition, the current interruption means 13 conducts and interrupts current in both directions, and is usually configured by connecting two field-effect transistors facing each other, but to avoid making the diagram complicated, it is represented as a switch circuit symbol.

[0022] The drive measurement circuit 2 is a circuit for controlling the impedance measuring device 1 (specifically, the switching circuit provided by the impedance measuring device 1), and includes a voltage measurement unit 20, a current measurement unit 21, an AC detection unit 22, and a drive control unit 23.

[0023] The voltage measurement unit 20 measures the voltage of battery B1 and the voltage of battery B2.

[0024] The current measuring unit 21 measures the current of battery B1 and the current of battery B2 based on the detection results of the current detection means. Specifically, the current measuring unit 21 measures the current of battery B1 based on the detection results of the detection resistor 15, and measures the current of battery B2 based on the detection results of the detection resistor 16. The current measuring unit 21 measures the current I1 flowing from battery B1 based on the detection voltage Vc1 of the detection resistor 15, and measures the current I2 flowing from battery B2 based on the detection voltage Vc2 of the detection resistor 16.

[0025] The AC detection unit 22 receives a measurement instruction signal from the MCU 200, which includes information on the measurement frequency. In accordance with the measurement instruction signal, it transmits an enable signal EN and a control signal Vs to the drive control unit 23, and also transmits information necessary for calculating the AC impedance (voltage information from the voltage measurement unit 20 and current information from the current measurement unit 21) to the MCU 200. The AC detection unit 22 also includes a current polarity control unit 24, which changes the control signal Vs according to the polarity of the first pulse of the AC current included in the measurement instruction signal.

[0026] The drive control unit 23 drives the first switching element 11 and the second switching element 12 based on the enable signal EN and control signal Vs from the AC detection unit 22. Details of the drive control unit 23 will be described later.

[0027] The repeating measurement control unit 203 outputs a measurement instruction signal to the AC detection unit 22. As a result, as will be described in detail later, the drive control unit 23 can drive multiple switching elements (specifically, the first switching element 11 and the second switching element 12) to periodically change the state of current movement through the inductor 14 according to the measurement frequency. Also, as will be described in detail later, the drive control unit 23 repeatedly switches between supplying and not supplying AC current to batteries B1 and B2, and in this repetition, it can switch the waveform of the first pulse when the AC current starts flowing from two or more types of waveforms.

[0028] Next, we will explain the details of the configuration of the AC detection unit 22.

[0029] Figure 2 is a circuit diagram showing an example of a voltage measurement unit 20, a current measurement unit 21, and an AC detection unit 22 of a battery monitoring system 100 according to Embodiment 1. Figure 2 mainly shows the internal configuration of the voltage measurement unit 20, the current measurement unit 21, and the AC detection unit 22. In Figure 2, batteries B1 and B2 each consist of two or more battery cells in series, and the voltage measurement unit 20 is shown to measure the voltage of each individual battery cell. Both the voltage measurement unit 20 and the current measurement unit 21 have an analog-to-digital converter (hereinafter abbreviated as ADC) that converts the detected voltage into a digital signal, and the voltage information from the voltage measurement unit 20 and the current information from the current measurement unit 21 are transmitted to the AC detection unit 22 as digital values. Each ADC measures the voltage and current of batteries B1 and B2 at the sampling frequency of the clock signal CK, which will be described later.

[0030] As shown in Figure 2, for example, the AC detection unit 22 includes a signal generation unit 220, a conversion unit 221, an integration unit 222, a holding unit 223, and a communication unit 224.

[0031] The signal generation unit 220 outputs a first reference frequency signal with frequency f according to the measurement command from the MCU 200, a second reference frequency signal having a phase orthogonal to the first reference frequency signal, and a clock signal CK to the ADCs of the voltage measurement unit 20 and the current measurement unit 21. The first reference frequency signal is a sine wave sin, and the second reference frequency signal is a cosine wave cos. The clock signal CK is a signal with a higher frequency than the first reference frequency signal and is synchronized with the first reference frequency signal.

[0032] The conversion unit 221 has a multiplier pair corresponding to each ADC, and each multiplier pair multiplies each digital value from each ADC by a first reference frequency signal sin and a second reference frequency signal cos, thereby converting each digital value into the real and imaginary components of a complex voltage and a complex current, respectively. The result of multiplication with the first reference frequency signal sin shows the real component when the sampled voltage is expressed as a complex voltage. The result of multiplication with the second reference frequency signal cos shows the imaginary component when the sampled voltage is expressed as a complex voltage.

[0033] The integrating unit 222 is equipped with the same number of averaging circuit pairs as the multiplier pairs of the conversion unit 221, and averages the real and imaginary components of the complex voltage and complex current, which are repeatedly measured and converted by the conversion unit 221. This averaging reduces the measurement error of the complex voltage and complex current, and oversampling improves the resolution (measurement accuracy). As a result, even with an ADC with a small number of bits (for example, around 16 bits), it is possible to obtain AC impedance measurement results with an accuracy of 20 to 24 bits.

[0034] The holding unit 223 holds the real and imaginary components of the complex voltage and complex current after the averaging process. Each register pair for holding the complex voltage consists of a register Re that holds the real component of the complex voltage and complex current of the corresponding battery cell, and a register Im that holds the imaginary component.

[0035] The communication unit 224 is a communication circuit for communicating with the MCU 200. It transmits data stored in the holding unit 223 to the MCU 200 and is used to receive measurement instruction signals from the MCU 200 (operation instructions to the drive control unit 23 and information on the frequency f of the first reference frequency signal). The communication performed by the communication unit 224 may be wireless communication or wired communication, and there are no particular limitations on the communication standard.

[0036] Next, we will describe the details of the configuration of the drive control unit 23.

[0037] Figure 3 is a circuit diagram showing an example of a drive control unit 23 according to Embodiment 1. Figure 3 shows the internal configuration of the drive control unit 23.

[0038] As shown in Figure 3, the oscillator 230 outputs a reference clock CK0 that sets the switching period, and a clock CK1 that is delayed by the maximum ON period of the first switching element 11 and the second switching element 12 from the reference clock CK0. Embodiment 1 shows an example in which these clock signals are generated by the oscillator 230 of the drive control unit 23, but these clock signals may be received from the MCU 200 or the like, or the clock signal CK of the AC detection unit 22 may be used, or these clock signals may be signals synchronized with the clock signal CK.

[0039] Reference voltage source 231 generates a threshold voltage Vr1, reference voltage source 232 generates a threshold voltage Vr2, comparator 233 compares the detected voltage Vc1 with the threshold voltage Vr1, and comparator 234 compares the detected voltage Vc2 with the reference voltage Vr2. In this disclosure, an example is shown in which these threshold voltages are generated inside the drive control unit 23, but these threshold voltages may be supplied from an MCU 200 or the like, or these threshold voltages may be made variable by instructions from the MCU 200 as described later.

[0040] The clock CK1, the output of comparator 233, and the output of comparator 234 are input to OR circuit 235. The reference clock CK0 sets SR latch 236, and the output of OR circuit 235 resets SR latch 236. The outputs Q and NQ of SR latch 236 are input to switch circuits 237 and 238. The control signal Vs from AC detection unit 22 is a signal that switches between high and low depending on the phase of the first reference frequency signal. Since the first reference frequency signal is a signal of a predetermined measurement frequency (frequency f) according to the measurement command from MCU 200, the control signal Vs is a signal of frequency f. When the control signal Vs is at a high level, switch circuit 237 selects and outputs output Q of SR latch 236, and switch circuit 238 selects and outputs output NQ. When the control signal Vs is at a low level, switch circuit 237 selects and outputs output NQ of SR latch 236, and switch circuit 238 selects and outputs output Q. The output of switch circuit 237 becomes a signal to drive the first switching element 11, and the output of switch circuit 238 becomes a signal to drive the second switching element 12.

[0041] The abnormality detection circuit 239 is not the core of this invention, so a detailed explanation and illustration are omitted. However, the abnormality detection circuit 239 outputs an abnormality signal Fail at an H level when the current value or voltage value of each battery detected by the AC detection unit 22, or the temperature of each battery detected by a temperature sensor (not shown), indicates an abnormal value. The abnormality signal Fail is logically inverted by the inverter 240 and input to the AND circuit 241 together with the enable signal EN. The output of the AND circuit 241 is the drive signal V13 of the current interruption means 13. The current interruption means 13 conducts when the drive signal V13 is at an H level and interrupts when it is at an L level. The output of the switch circuit 237 and the drive signal V13 are input to the AND circuit 242, and the drive signal Vg1 is output from the AND circuit 242. The output of the switch circuit 238 and the drive signal V13 are input to the AND circuit 243, and the drive signal Vg2 is output from the AND circuit 243. In other words, if there is no abnormality and a measurement instruction is received from the MCU 200, the drive signal V13 causes the current interruption means 13 to conduct, electrically connecting the inductor 14 to the first switching element 11 and the second switching element 12, and the first switching element 11 and the second switching element 12 are driven to switch on and off alternately.

[0042] In addition, to prevent the first switching element 11 and the second switching element 12 from being turned on simultaneously, a dead time is provided in which the normal drive signal Vg1 and drive signal Vg2 are turned off at the same time. Although not shown in the diagram, it is assumed that a delay time equivalent to the dead time is provided at the rising edge of each drive signal.

[0043] Next, we will explain the details of the operation of the drive control unit 23.

[0044] Figure 4 is a timing chart showing an example of the operation of the drive control unit 23 according to Embodiment 1. Figure 4 is a timing chart showing the operation of the main part of the drive control unit 23, and shows a reference clock CK0, a clock CK1, a control signal Vs, a drive signal Vg1, a detection voltage Vc1, a drive signal Vg2, and a detection voltage Vc2. Although not shown, the enable signal EN is at the H level and the abnormal signal Fail is at the L level. The detection voltage Vc1 corresponds to the current I1 flowing through the battery B1 and the first switching element 11, and the detection voltage Vc2 corresponds to the current I2 flowing through the battery B2 and the second switching element 12. For example, the threshold voltage Vr1 and the threshold voltage Vr2 may be the same voltage, and in Figure 4, the threshold voltages Vr1 and Vr2 are shown as the threshold voltage Vr. Hereinafter, using Figure 4, the operation in which high-frequency current pulses flow through the batteries B1 and B2 with high efficiency by the drive control unit 23 of Embodiment 1 will be described.

[0045] First, as shown on the left side of Figure 4, the operation of the drive control unit 23 at times t0 to t2 when the control signal Vs is at the H level will be described. At times t0 to t2, since the control signal Vs is at the H level, the output Q of the SR latch 236 is output as the drive signal Vg1 of the first switching element 11, and the output NQ of the SR latch 236 is output as the drive signal Vg2 of the second switching element 12.

[0046] At time t0, when the reference clock CK0 rises, the SR latch 236 is set, the output Q, that is, the drive signal Vg1 rises, and the output NQ, that is, the drive signal Vg2 falls. The first switching element 11 is turned on and conducts by the drive signal Vg1, and the current I1 flows from the positive electrode of the battery B1 through the first switching element 11, the inductor 14, and the current blocking means 13 to the negative electrode of the battery B1 through the first loop. On the other hand, the drive signal Vg2 becomes the L level and the second switching element 12 is turned off, the current I2 does not flow, and the detection voltage Vc2 also becomes zero. The current I1 increases at a slope determined by the voltage of the battery B1 and the inductance of the inductor 14, and the detection voltage Vc1 also increases in proportion to the current I1.

[0047] At time t1, when the detection voltage Vc1 reaches the threshold voltage Vr1, the output of the comparator 233 is inverted to the H level and resets the SR latch 236 via the OR circuit 235. When the SR latch 236 is reset, the output Q, that is, the drive signal Vg1 falls, and the output NQ, that is, the drive signal Vg2 rises. The first switching element 11 turns off, and the voltage of the inductor 14 is inverted. The body diode of the second switching element 12 conducts, and after the dead time, the second switching element 12 becomes on. Since the dead time is a very short period, it is not shown, and the conduction of the body diode of the second switching element 12 and the turn-on of the second switching element 12 are expressed as occurring simultaneously at time t1. The current of the inductor 14 is held, and the current I2 flows through the second loop from the negative electrode of the battery B2, through the second switching element 12, the inductor 14, and the current cutoff means 13, to the positive electrode of the battery B2. This is a negative current in the opposite direction to the direction of the current I2 in the figure, and starting from the current value corresponding to the threshold voltage Vr1 as the initial value, it increases in the positive direction at a slope determined by the voltage of the battery B2 and the inductance of the inductor 14.

[0048] Eventually, when the reference clock CK0 rises at time t2, the operation from time t0 is repeated. In this repetition, a pulse current with the current value corresponding to the threshold voltage Vr1 as the peak flows as the current I1 in the direction of discharging the battery B1, and a pulse current with the current value corresponding to the threshold voltage Vr1 as the peak flows as the current I2 in the direction of charging the battery B2.

[0049] Next, when the control signal Vs becomes the L level at time t3, the switch circuit 237 switches to select and output the output NQ of the SR latch 236, and the switch circuit 238 switches to select and output the output Q of the SR latch 236. Therefore, hereafter, the rising timings of the drive signal Vg1 and the drive signal Vg2 are also interchanged. Specifically, the drive signal Vg2 becomes the H level at the rising of the reference clock CK0, and becomes the L level when the detection voltage Vc2 reaches the threshold voltage Vr2 or when the clock CK1 rises. From time t3, the state where the current I2 flows continues, and the current I2 increases.

[0050] At time t4, when the ON state of the second switching element 12 reaches its maximum ON period, the clock CK1 rises, the SR latch 236 is reset via the OR circuit 235, the drive signal Vg2 falls, and the second switching element 12 turns off. At this time, assuming that the increasing current I2 has reached the positive direction, the voltage across the inductor 14 reverses. The body diode of the first switching element 11 conducts, and after a dead time, the first switching element 11 turns ON.

[0051] At time t5, the reference clock CK0 rises, the SR latch 236 is set, output Q, i.e., the drive signal Vg2 rises, and output NQ, i.e., the drive signal Vg1 falls. The drive signal Vg2 turns on the second switching element 12 and conducts, and current I2 flows through the second loop from the positive terminal of battery B2 to the negative terminal of battery B2 via the current interruption means 13, inductor 14, and second switching element 12. Meanwhile, the drive signal Vg1 becomes L level, the first switching element 11 turns off, current I1 does not flow, and the detected voltage Vc1 also becomes zero. Current I2 increases with a slope determined by the voltage of battery B2 and the inductance of inductor 14, and the detected voltage Vc2 also increases proportionally to the current I2. From here on, the operation from time t3, when the second switching element 12 switches during its maximum on period, is repeated. With this repetition, the peak value of current I2 increases.

[0052] At time t6, when the detected voltage Vc2 of the current I2 reaches the threshold voltage Vr2, the output of the comparator 234 inverts to a high level, resetting the SR latch 236 via the OR circuit 235. The reset of the SR latch 236 causes the output Q, i.e., the drive signal Vg2, to fall, and the output NQ, i.e., the drive signal Vg1, to rise. The second switching element 12 turns off, and the voltage across the inductor 14 inverts. The body diode of the first switching element 11 conducts, and after a dead time, the first switching element 11 turns on. The current in the inductor 14 is maintained, and the current I1 flows through the first loop from the negative terminal of the battery B1 to the positive terminal of the battery B1 via the current interruption means 13, the inductor 14, and the first switching element 11. This is a negative current, opposite in direction to the current I1 shown in the diagram. Starting with a current value whose absolute value corresponds to the threshold voltage Vr2, it increases in the positive direction with a slope determined by the voltage of battery B1 and the inductance of inductor 14.

[0053] Eventually, at time t7, the reference clock CK0 starts up, and the operation from time t5 is repeated. In this repetition, a pulsed current flows with a peak value corresponding to the threshold voltage Vr2 as the current I2 in the direction of discharging battery B2, and a pulsed current flows with a peak value corresponding to the threshold voltage Vr2 as the current I1 in the direction of charging battery B1.

[0054] Next, at time t8, when the control signal Vs reaches the H level, switch circuit 237 switches to select and output output Q of SR latch 236, and switch circuit 238 switches to select and output output NQ of SR latch 236. As a result, the rising timing of drive signals Vg1 and Vg2 is also reversed. Specifically, drive signal Vg1 reaches the H level on the rising edge of the reference clock CK0, and becomes L level when the detection voltage Vc2 reaches the threshold voltage Vr2 or when clock CK1 rises. From time t8 onwards, current I1 continues to flow, and the current I1 increases.

[0055] Subsequently, the switching operation of the first switching element 11 during its maximum on-period causes current I1 to increase and current I2 to decrease. Eventually, the peak value of current I1 becomes a current value corresponding to the threshold voltage Vr1, and the operation from time t0 onward is performed again.

[0056] As described above, in accordance with the control signal Vs, the batteries B1 and B2 are repeatedly charged and discharged with a predetermined peak value pulse current with low loss. The charge / discharge current I1 is converted to a detection voltage Vc1 by the detection resistor 15, and the current I2 is converted to a detection voltage Vc2 by the detection resistor 16, and both are input to the current measurement unit 21. During the measurement of AC impedance, the impedance measuring device 1 regenerates energy drawn from battery B1 to battery B2 during the H level period of the control signal Vs, and regenerates energy drawn from battery B2 to battery B1 during the L level period of the control signal Vs. Therefore, if the H level period and the L level period of the control signal Vs are equal, and the threshold voltages Vr1 and Vr2 are equal, the charge and discharge charges of batteries B1 and B2 will also be equal, thus suppressing increases and decreases in battery voltage and changes in charge capacity SOC (State of Charge).

[0057] Conversely, energy can be transferred from battery B1 to battery B2, or from battery B2 to battery B1, by making threshold voltages Vr1 and Vr2 different, or by changing the high-low period ratio of the control signal Vs. For example, when transferring energy from battery B1 to battery B2, it is advisable to make threshold voltage Vr1 higher than threshold voltage Vr2, or to make the high-level period of the control signal Vs longer than the low-level period. Although not the essence of this disclosure, since the voltage of each battery is also monitored, this energy transfer can also be applied to maintaining the voltage balance of the batteries.

[0058] As described above, the AC detection unit 22 receives a measurement instruction signal including information on the measurement frequency from the MCU 200, which has a function to calculate AC impedance. Based on the measurement results of the voltage measurement unit 20 and the current measurement unit 21, it measures the AC voltage and AC current corresponding to the measurement frequency and outputs them to the MCU 200. The drive control unit 23 drives the first switching element 11 and the second switching element 12 to periodically change the current movement state via the inductor 14 according to the measurement frequency, thereby supplying AC current to batteries B1 and B2.

[0059] This allows the transfer of electrical energy between battery B1 and battery B2 to be periodically changed according to the measurement frequency, enabling the measurement of AC voltage and AC current corresponding to the measurement frequency, and thus enabling the measurement of the AC impedance of batteries B1 and B2.

[0060] The voltage measurement unit 20 may simultaneously measure the voltage of two or more battery cells that make up batteries B1 and B2. This allows the voltage of battery B1 and battery B2 to be measured in a short time.

[0061] Furthermore, as shown in Figure 4, the drive control unit 23 may alternately turn on the first switching element 11 and the second switching element 12 at a frequency higher than the measurement frequency. This shortens the time during which current flows through the inductor 14 at once. In other words, since a large current is less likely to flow through the inductor 14, the inductor 14 can be made smaller, and consequently, the impedance measuring device 1 can be made smaller.

[0062] Furthermore, the drive control unit 23 may control the on-time of the first switching element 11 and the on-time of the second switching element 12 so as to repeat, at a period corresponding to the measurement frequency, a first energy transfer state (from time t0 to time t4 in Figure 4) in which a discharge current is supplied from the battery B1 when the first switching element 11 is turned on and a charging current is supplied to the battery B2 when the second switching element 12 is turned on, and a second energy transfer state (from time t4 to time t8 in Figure 4) in which a discharge current is supplied from the battery B2 when the second switching element 12 is turned on and a charging current is supplied to the battery B1 when the first switching element 11 is turned on.

[0063] As a result, as shown from time t3 to time t4 in Figure 4, by increasing the on time of the second switching element 12, a discharge current can be started to flow from the battery B2, and as a result, it is possible to switch from the first energy transfer state to the second energy transfer state. Also, as shown from time t8 onwards in Figure 4, by increasing the on time of the first switching element 11, a discharge current can be started to flow from the battery B1, and as a result, it is possible to switch from the second energy transfer state to the first energy transfer state.

[0064] Furthermore, the drive control unit 23 may limit the peak value of the discharge current from battery B1 to a predetermined value (a value corresponding to the threshold voltage Vr1) in the first energy transfer state, and limit the peak value of the discharge current from battery B2 to a predetermined value (a value corresponding to the threshold voltage Vr2) in the second energy transfer state. This allows the discharge current from battery B1 and battery B2 to be limited, thereby suppressing switching losses that occur during switching.

[0065] Furthermore, the switching circuit may also have a current interruption means 13 connected in series with the inductor 14, and the drive control unit 23 may interrupt the current flowing to the current interruption means 13 when the detection results of the detection resistors 15 and 16 exceed a predetermined amount. This allows the current to be interrupted when an overcurrent flows.

[0066] Next, we will describe the details of the operation of the battery monitoring system 100.

[0067] Figure 5 is a flowchart showing an example of the operation of the battery monitoring system 100 according to Embodiment 1.

[0068] Figure 6 shows an example of the AC impedance measurement sequence in Embodiment 1.

[0069] Figure 7 shows an example of the current and voltage waveforms of the battery in Embodiment 1. T1 is the static time before measuring the cell voltage when EIS measurement is not being performed. T2 is the time when the cell voltage is measured when EIS measurement is not being performed. T1 + T2 is the time between intermittently performed EIS measurements when EIS measurement is not being performed. T3 is the time to excite the EIS current. T4 is the static time before performing the EIS measurement during the time when the EIS current is being excited. T5 is the time to perform the EIS measurement. At T3, an AC current is excited in the battery cell to perform the EIS measurement, but the EIS measurement is performed at T5 after waiting for a certain time T4. Note that the cell current waveform shown in Figure 7 actually has the shape of a burst wave as Vc1 and Vc2 in Figure 4, but here the waveform obtained by averaging the current with the shape of a burst wave every half period is shown. The same applies to Figures 9, 12 and 15 which will be described later.

[0070] To avoid the influence of voltage fluctuations caused by the application of current during AC impedance measurement, or EIS measurement, EIS measurements are performed intermittently, for example, at a period of several tens of ms, as shown in Figure 6. The measurement results are then integrated and averaged. With each EIS measurement, an AC current, the EIS current, is excited in the battery cell. As shown in Figure 7, this AC current (cell current) alternates between positive and negative pulses for a period of T3.

[0071] Immediately after the application of current for EIS measurement, there is an effect of the transient response of the voltage. Therefore, it is conceivable to exclude the section where the transient response effect exists (the section T4 shown in Figure 7) from the EIS measurement section as a static decomposition section before EIS measurement, but this has the problem of shortening the measurement time for EIS measurement. In response to this, the drive control unit 23 repeatedly switches between supplying and not supplying alternating current to batteries B1 and B2, and in this repetition, switches the waveform of the first pulse when the alternating current is started from two or more types of waveforms. In Embodiment 1, the two or more types of waveforms include a waveform with positive polarity and a waveform with negative polarity. This will be explained using Figures 5 to 7.

[0072] As shown in Figure 5, first, the repeat measurement control unit 203 initializes the accumulated value of the EIS measurements up to the previous measurement (step S101).

[0073] Next, the repeating measurement control unit 203 issues an EIS measurement instruction to the drive measurement circuit 2 by outputting a measurement instruction signal (step S102). At this time, the repeating measurement control unit 203 issues the EIS measurement instruction so that the polarity of the control signal Vs at the start is positive. As a result, as shown in the second and fourth waveforms from the left in Figure 7, the polarity of the first pulse when AC current is started to flow through the battery cell is positive, the polarity of the next pulse is negative, and so on, and the battery cell repeatedly discharges, charges, and so on. The waveform of the AC voltage generated in the battery cell becomes a waveform that is negative at the beginning, positive at the next, and so on. At this time, a transient response occurs in the AC voltage, and as shown in the second and fourth cell voltage waveforms from the left in Figure 7, the waveform changes from a state biased towards the negative side to a steady state.

[0074] Next, the repeat measurement control unit 203 acquires the measurement results of the current EIS measurement via the AC detection unit 22 (step S103). At this time, the AC detection unit 22 may start measuring the AC voltage and AC current after a predetermined time (specifically, T4 shown in Figure 7) has elapsed since the drive control unit 23 started driving the multiple switching elements.

[0075] Then, the repeat measurement control unit 203 adds the current measurement result to the accumulated value of the previous measurement results, thereby accumulating the measurement results (step S104).

[0076] Next, the repeating measurement control unit 203 issues an EIS measurement instruction to the drive measurement circuit 2 by outputting a measurement instruction signal (step S105). At this time, the repeating measurement control unit 203 issues the EIS measurement instruction so that the polarity of the control signal Vs at the start is negative. As a result, as shown in the first and third waveforms from the left in Figure 7, the polarity of the first pulse when AC current is started to flow through the battery cell is negative, the polarity of the next pulse is positive, and so on, and the battery cell repeats charging, discharging, and so on. The waveform of the AC voltage generated in the battery cell becomes a waveform that repeats, with the first being positive, the next being negative, and so on. At this time, a transient response occurs in the AC voltage, and as shown in the first and third cell voltage waveforms from the left in Figure 7, the waveform changes from a state biased towards the positive side to a steady state.

[0077] Next, the repeat measurement control unit 203 acquires the measurement result of the current EIS measurement via the AC detection unit 22 (step S106), and adds the current measurement result to the cumulative value of the previous measurement results to accumulate the measurement results (step S107).

[0078] Next, the repeat measurement control unit 203 determines whether the number of EIS measurements is less than a threshold (step S108). This threshold is set in advance. Note that the number of measurements performed in step S102 and the number of measurements performed in step S105 do not have to be the same, and the number of measurements may be set to match the transient voltage characteristics of charging and discharging of the battery cell.

[0079] If the number of EIS measurements is less than the threshold (Yes in step S108), the process from step S102 is repeated. In other words, the process from step S102 to step S107 is repeated until the number of EIS measurements is equal to or greater than the threshold. Note that the length of T3 or the length of T4 may differ as long as the length of T5 is the same for each EIS measurement.

[0080] If the number of EIS measurements is less than a threshold (No in step S108), the repeat measurement control unit 203 calculates the average value of the accumulated measurement results (step S109). In other words, the repeat measurement control unit 203 calculates the accumulated value / number of measurements. At this time, the repeat measurement control unit 203 may align the phase of the currents of each measurement for the measured AC current and AC voltage, then average them, and use the averaged value to calculate the AC impedance. Alternatively, the repeat measurement control unit 203 may calculate the AC impedance from the AC current and AC voltage of each measurement and then average the calculated AC impedances.

[0081] As explained above, by repeatedly switching between applying and not applying AC current, and by switching the waveform of the first pulse when the AC current is started to reverse the polarity of the transient response of the voltage immediately after the application of current for EIS measurement, even if there is a transient response to the voltage, the effect of the transient response can be canceled out by averaging the repeated measurement results, and the AC impedance can be measured with high accuracy. Specifically, by averaging the voltage waveform in which a transient response occurred, changing from a state biased to the negative side to a steady state, and the voltage waveform in which a transient response occurred, changing from a state biased to the positive side to a steady state, the effect of the transient response can be canceled out, and the AC impedance can be measured with high accuracy. Therefore, it is not necessary to exclude the section in which the effect of the transient response of the voltage exists from the EIS measurement section, or the excluded section can be shortened, thus ensuring sufficient measurement time for EIS measurement.

[0082] Specifically, as shown in Figure 7, by repeatedly switching the polarity of the first pulse when the AC current is started to flow between positive and negative, the polarity of the voltage transient response can be reversed. Note that the polarity of the first pulse when the AC current is started does not necessarily have to be switched alternately with each EIS measurement. For example, multiple EIS measurements may be performed with a positive polarity for the first pulse when the AC current is started, followed by multiple EIS measurements with a negative polarity for the first pulse when the AC current is started. In this case as well, the effect of the transient response can be canceled out by averaging.

[0083] Furthermore, the drive control unit 23 does not need to switch the waveform of the first pulse when it starts supplying AC current to batteries B1 and B2, when repeatedly supplying and not supplying AC current, from two or more waveforms. This will be explained using Figures 8 and 9.

[0084] Figure 8 shows another example of the AC impedance measurement sequence in Embodiment 1. In Figure 8, the waveform of the first pulse when the AC current is started is always negative, meaning that when the AC current is started, it always begins with charging the battery cell.

[0085] Figure 9 shows another example of the current and voltage waveforms of the battery in Embodiment 1.

[0086] The drive control unit 23 may repeatedly supply and desupply alternating current to batteries B1 and B2, and the voltage measurement unit 20 may measure the voltage of battery B1 and the voltage of battery B2 after a predetermined static time (specifically, T1 shown in Figure 9) from the moment when the system switches from a state where alternating current flows to a state where it does not flow to batteries B1 and B2. At this time, as shown in Figures 8 and 9, the alternating current may flow in such a way that the battery cells are always repeatedly charged, discharged, etc. with each EIS measurement, meaning that the waveform of the first pulse when the alternating current starts to flow does not have to switch between one of two types of waveforms.

[0087] In the repeated switching between applying and not applying alternating current, the voltages of batteries B1 and B2 are affected by EIS measurement after the timing when the AC current switches from flowing to not flowing, making it impossible to measure the correct voltages of batteries B1 and B2. Therefore, by measuring the voltages of batteries B1 and B2 after a predetermined settling time from the timing when the AC current switches from flowing to not flowing, the voltages of batteries B1 and B2 can be measured with high accuracy.

[0088] Similarly, in the examples described in Figures 6 and 7, the voltage measurement unit 20 may measure the voltage of battery B1 and the voltage of battery B2 after a predetermined settling time from the moment when the system switches from a state in which AC current flows through batteries B1 and B2 to a state in which no AC current flows.

[0089] (Embodiment 2) Next, the drive measurement circuit according to Embodiment 2 will be described.

[0090] Figure 10 is a configuration diagram showing an example of a battery monitoring system 100a according to Embodiment 2. In addition to the battery monitoring system 100a, batteries B1 and B2 are also shown in Figure 10.

[0091] The battery monitoring system 100a differs from the battery monitoring system 100 according to Embodiment 1 in that it includes an impedance measuring device 1a instead of the impedance measuring device 1, and an MCU 200a instead of the MCU 200. Furthermore, the impedance measuring device 1a differs from the impedance measuring device 1 according to Embodiment 1 in that it includes a drive measuring circuit 2a instead of the drive measuring circuit 2, the drive measuring circuit 2a includes an AC detection unit 22a instead of the AC detection unit 22, and a drive control unit 23a instead of the drive control unit 23. Also, the MCU 200a differs from the MCU 200 according to Embodiment 1 in that it includes a repetitive measurement control unit 204 instead of the repetitive measurement control unit 203. Other points are the same as in Embodiment 1, so their explanation will be omitted, and the following will focus on the differences from Embodiment 1.

[0092] The AC detection unit 22a receives a measurement instruction signal from the MCU 200a that includes information on the measurement frequency. In accordance with the measurement instruction signal, it transmits an enable signal EN and a control signal Vs to the drive control unit 23a, and also transmits information necessary for calculating the AC impedance (voltage information from the voltage measurement unit 20 and current information from the current measurement unit 21) to the MCU 200a. The AC detection unit 22a also includes a current pulse width control unit 25, which changes the control signal Vs according to the pulse width of the first pulse of the AC current included in the measurement instruction signal.

[0093] The drive control unit 23a drives the first switching element 11 and the second switching element 12 based on the enable signal EN and control signal Vs from the AC detection unit 22a. Details of the drive control unit 23a will be described later.

[0094] The repeating measurement control unit 204 outputs a measurement instruction signal to the AC detection unit 22a. As a result, the drive control unit 23a drives multiple switching elements (specifically, the first switching element 11 and the second switching element 12) to periodically change the current flow state through the inductor 14 according to the measurement frequency. The drive control unit 23a also repeatedly switches between supplying and not supplying AC current to batteries B1 and B2, and in each repetition, switches the waveform of the first pulse when the AC current is started from two or more types of waveforms. In Embodiment 2, the two types of waveforms include a waveform with a shorter pulse width than the other waveforms. This will be explained using Figures 11 and 12.

[0095] Figure 11 is a flowchart showing an example of the operation of the battery monitoring system 100a according to Embodiment 2.

[0096] Figure 12 shows an example of the current and voltage waveforms of the battery in Embodiment 2.

[0097] As shown in Figure 11, first, the repeat measurement control unit 204 initializes the accumulated value of the EIS measurements up to the previous measurement (step S201).

[0098] Next, the repeating measurement control unit 204 issues an EIS measurement instruction to the drive measurement circuit 2a by outputting a measurement instruction signal to the drive measurement circuit 2a (step S202). At this time, the repeating measurement control unit 204 issues the EIS measurement instruction so that the pulse width when the control signal Vs starts is shorter than the pulse width under normal conditions. As a result, as shown in the second and fourth waveforms from the left in Figure 12, the first pulse when the alternating current is started to flow through the battery cell has a short pulse width and a negative polarity. The alternating voltage generated in the battery cell by this alternating current has a very small positive waveform at the beginning, as shown in the second and fourth cell voltage waveforms from the left in Figure 12. At this time, a transient response occurs in the alternating voltage, but because the beginning of the waveform is a very small positive waveform, the effect of the beginning of the waveform is small, and as shown in the second and fourth cell voltage waveforms from the left in Figure 12, the waveform changes from a state biased towards the negative side to a steady state. In other words, the waveforms of the second cell voltage from the left and the fourth cell voltage from the left in Figure 12 are similar to the waveforms of the second cell voltage from the left and the fourth cell voltage from the left in Figure 7.

[0099] Next, the repeat measurement control unit 204 acquires the measurement results of the current EIS measurement via the AC detection unit 22a (step S203). At this time, the AC detection unit 22a may start measuring the AC voltage and AC current after a predetermined time (specifically, T4 shown in Figure 12) after the drive control unit 23a has started driving the multiple switching elements.

[0100] Then, the repeat measurement control unit 204 adds the current measurement result to the accumulated value of the previous measurement results, thereby accumulating the measurement results (step S204).

[0101] Next, the repeating measurement control unit 204 issues an EIS measurement instruction to the drive measurement circuit 2a by outputting a measurement instruction signal to the drive measurement circuit 2a (step S205). At this time, the repeating measurement control unit 204 issues the EIS measurement instruction so that the pulse width when the control signal Vs starts becomes the pulse width of the normal state. As a result, as shown in the first and third waveforms from the left in Figure 12, the polarity of the first pulse when AC current is started to flow through the battery cell is negative, the polarity of the next pulse is positive, and so on, and the battery cell repeats charging, discharging, and so on. The AC voltage generated in the battery cell has a waveform that repeats, with the first being positive, the next being negative, and so on. At this time, a transient response occurs in the AC voltage, and as shown in the first and third cell voltage waveforms from the left in Figure 12, the waveform changes from a state biased towards the positive side to a steady state.

[0102] Next, the repeat measurement control unit 204 acquires the measurement result of the current EIS measurement via the AC detection unit 22a (step S206), and adds the current measurement result to the cumulative value of the previous measurement results to accumulate the measurement results (step S207).

[0103] Next, the repeat measurement control unit 204 determines whether the number of EIS measurements is less than a threshold (step S208). This threshold is set in advance. Note that the number of measurements performed in step S202 and the number of measurements performed in step S205 do not have to be the same, and the number of measurements may be set to match the transient voltage characteristics of charging and discharging of the battery cell.

[0104] If the number of EIS measurements is less than the threshold (Yes in step S208), the process from step S202 is repeated. In other words, the process from step S202 to step S207 is repeated until the number of EIS measurements is equal to or greater than the threshold. Note that the length of T3 or the length of T4 may differ as long as the length of T5 is the same for each EIS measurement.

[0105] If the number of EIS measurements is less than a threshold (No in step S208), the repeat measurement control unit 204 calculates the average value of the accumulated measurement results (step S209). In other words, the repeat measurement control unit 204 calculates the accumulated value / number of measurements. At this time, the repeat measurement control unit 204 may align the phase of the currents of each measurement for the measured AC current and AC voltage, then average them, and use the averaged value to calculate the AC impedance. Alternatively, the repeat measurement control unit 204 may calculate the AC impedance from the AC current and AC voltage of each measurement and then average the calculated AC impedances.

[0106] As explained above, as shown in Figure 12, by repeatedly switching between applying and not applying AC current, the pulse width of the first pulse when the AC current is applied can be switched between a short width and a normal width, thereby reversing the polarity of the transient response of the voltage, similar to switching the polarity of the first pulse when the AC current is applied between positive and negative. In other words, by shortening the pulse width of the first pulse when the AC current is applied, and then not shortening the pulse width of the first pulse when the AC current is applied, and repeating this, the waveform of the AC voltage generated in the battery cell can be made to be similar to the waveform when the polarity of the first pulse when the AC current is applied is switched between positive and negative. Note that, as in Embodiment 1, the pulse width of the first pulse when the AC current is applied does not have to be switched alternately for each EIS measurement. For example, after multiple EIS measurements with a short pulse width for the first pulse when the AC current is applied are performed, multiple EIS measurements with a normal pulse width for the first pulse when the AC current is applied may be performed. In this case as well, averaging can offset the effects of transient responses.

[0107] Furthermore, the two or more waveforms may include, in addition to a waveform with a shorter pulse width than the other waveforms, a waveform with positive polarity and a waveform with negative polarity as described in Embodiment 1, and in the repeated switching between applying and not applying AC current, the waveform of the first pulse when the AC current is applied may be switched from among these waveforms.

[0108] (Embodiment 3) Next, the drive measurement circuit according to Embodiment 3 will be described.

[0109] Figure 13 is a configuration diagram showing an example of a battery monitoring system 100b according to Embodiment 3. In addition to the battery monitoring system 100b, batteries B1 and B2 are also shown in Figure 13.

[0110] The battery monitoring system 100b differs from the battery monitoring system 100 according to Embodiment 1 in that it includes an impedance measuring device 1b instead of an impedance measuring device 1, and an MCU 200b instead of an MCU 200. Furthermore, the impedance measuring device 1b differs from the impedance measuring device 1 according to Embodiment 1 in that it includes a drive measuring circuit 2b instead of a drive measuring circuit 2, the drive measuring circuit 2b includes an AC detection unit 22b instead of an AC detection unit 22, and a drive control unit 23b instead of a drive control unit 23. Also, the MCU 200b differs from the MCU 200 according to Embodiment 1 in that it includes a repetitive measurement control unit 205 instead of a repetitive measurement control unit 203. Other points are the same as in Embodiment 1, so their explanation will be omitted, and the following will focus on the differences from Embodiment 1.

[0111] The AC detection unit 22b receives a measurement instruction signal from the MCU 200b that includes information on the measurement frequency. In accordance with the measurement instruction signal, it transmits an enable signal EN and a control signal Vs to the drive control unit 23b, and also transmits information necessary for calculating the AC impedance (voltage information from the voltage measurement unit 20 and current information from the current measurement unit 21) to the MCU 200b. The AC detection unit 22b also includes a measurement start phase control unit 26, which starts measuring the AC current and AC voltage at the timing included in the measurement instruction signal.

[0112] The drive control unit 23b drives the first switching element 11 and the second switching element 12 based on the enable signal EN and control signal Vs from the AC detection unit 22b.

[0113] The repeating measurement control unit 205 outputs a measurement instruction signal to the AC detection unit 22b. As a result, the drive control unit 23b drives multiple switching elements (specifically, the first switching element 11 and the second switching element 12) to periodically change the current flow state through the inductor 14 according to the measurement frequency. The drive control unit 23b also repeatedly switches between supplying and not supplying AC current to batteries B1 and B2, and the AC detection unit 22b varies the timing of the start of AC voltage and AC current measurements during each repetition. This will be explained using Figures 14 and 15.

[0114] Figure 14 is a flowchart showing an example of the operation of the battery monitoring system 100b according to Embodiment 3.

[0115] Figure 15 shows an example of the current and voltage waveforms of the battery in Embodiment 3.

[0116] As shown in Figure 14, first, the repeat measurement control unit 205 initializes the accumulated value of the EIS measurements up to the previous measurement (step S301).

[0117] Next, the repeating measurement control unit 205 issues an EIS measurement instruction to the drive measurement circuit 2b by outputting a measurement instruction signal to the drive measurement circuit 2b (step S302). At this time, the AC detection unit 22b starts measuring the AC voltage and AC current at the timing when the AC voltage waveform changes from negative to positive, as shown in the first and third waveforms from the left in Figure 15. In other words, it starts at the timing when T5 changes from negative to positive in the AC voltage waveform.

[0118] Next, the repeat measurement control unit 205 acquires the measurement results of the current EIS measurement via the AC detection unit 22b (step S303).

[0119] Then, the repeat measurement control unit 205 adds the current measurement result to the accumulated value of the previous measurement results, thereby accumulating the measurement results (step S304).

[0120] Next, the repeating measurement control unit 205 issues an EIS measurement instruction to the drive measurement circuit 2b by outputting a measurement instruction signal to the drive measurement circuit 2b (step S305). At this time, the AC detection unit 22b starts measuring the AC voltage and AC current at the timing when the AC voltage waveform changes from positive to negative, as shown in the second and fourth waveforms from the left in Figure 15. In other words, it starts at the timing when T5 changes from positive to negative in the AC voltage waveform.

[0121] Next, the repeat measurement control unit 205 acquires the measurement result of the current EIS measurement via the AC detection unit 22b (step S306), and adds the current measurement result to the cumulative value of the previous measurement results to accumulate the measurement results (step S307).

[0122] Next, the repeat measurement control unit 205 determines whether the number of EIS measurements is less than a threshold (step S308). This threshold is set in advance. Note that the number of measurements performed in step S302 and the number of measurements performed in step S305 do not have to be the same, and the number of measurements may be set to match the transient voltage characteristics of charging and discharging of the battery cell.

[0123] If the number of EIS measurements is less than the threshold (Yes in step S308), the process from step S302 is repeated. In other words, the process from step S302 to step S307 is repeated until the number of EIS measurements is equal to or greater than the threshold. Note that if the length of T5 is the same for each EIS measurement, the length of T3 or T4 may be different. For example, in the second waveform from the left in Figure 15, the length of T3 is shorter than the other waveforms, and in the fourth waveform from the left in Figure 15, the length of T3 is longer than the other waveforms.

[0124] If the number of EIS measurements is less than a threshold (No in step S308), the repeat measurement control unit 205 calculates the average value of the accumulated measurement results (step S309). In other words, the repeat measurement control unit 205 calculates the accumulated value / number of measurements. At this time, the repeat measurement control unit 205 may align the phase of the currents of each measurement for the measured AC current and AC voltage, then average them, and use the averaged value to calculate the AC impedance. Alternatively, the repeat measurement control unit 205 may calculate the AC impedance from the AC current and AC voltage of each measurement and then average the calculated AC impedances.

[0125] As explained above, by switching the timing of starting AC voltage and AC current measurements during repeated cycles of applying and not applying AC current, and by switching the timing of starting AC voltage and AC current measurements to coincide with the change in AC voltage polarity from negative to positive and from positive to negative, even if there is a transient response to the voltage, the effects of the transient response can be offset by averaging the repeated measurement results, allowing for highly accurate measurement of AC impedance. Therefore, the timing of starting AC voltage and AC current measurements can be set to shorten the section affected by the transient response of the voltage, and the section excluded from the EIS measurement section can be shortened, thus ensuring sufficient measurement time for the EIS measurement.

[0126] The above explanation describes an example where the timing (phase) for starting the measurement of AC voltage and AC current is switched between 0° and 180°, but it is not limited to this. For example, the timing (phase) may be switched between 0° and ±120°.

[0127] (Other Embodiments) Embodiments have been described above as examples of the technology relating to this disclosure. However, the technology relating to this disclosure is not limited thereto and can be applied to embodiments that are modified, replaced, added to, or omitted as appropriate. For example, the following modified examples are also included in one embodiment of this disclosure.

[0128] For example, in the above embodiment, an example was described in which the repetitive measurement control unit averages the results of multiple measurements of AC voltage and AC current measured in a repetitive cycle of applying and not applying AC current to batteries B1 and B2, but the invention is not limited to this. For example, the AC detection unit may average the results of multiple measurements of AC voltage and AC current measured in the above cycle. In other words, the AC detection unit may have the function of a repetitive measurement control unit.

[0129] For example, this disclosure can be implemented not only as a drive measurement circuit, but also as a drive measurement method that includes steps (processes) performed by the components constituting the drive measurement circuit.

[0130] Figure 16 is a flowchart showing an example of a drive measurement method according to another embodiment.

[0131] The drive measurement method is a drive measurement method for controlling an impedance measuring device that measures the AC impedance of a first battery and a second battery connected in series, wherein the impedance measuring device comprises an inductor that stores or releases electrical energy, a switching circuit consisting of a plurality of switching elements that intermittently move current between the first battery and the second battery via the inductor, and current detection means for detecting the current of the first battery and the current of the second battery, and the drive measurement method, as shown in Figure 16, includes a power receiving step (step S1) of receiving a measurement instruction signal including information on the measurement frequency from a higher-level system having a function to calculate AC impedance. 1) The device includes: a drive step (step S12) which drives a plurality of switching elements to periodically change the state of current movement through an inductor according to the measurement frequency, thereby supplying alternating current to a first battery and a second battery; a current measurement step (step S13) which measures the current of the first battery and the current of the second battery based on the detection result of the current detection means; a voltage measurement step (step S14) which measures the voltage of the first battery and the voltage of the second battery; and an AC detection step (step S15) which measures an alternating voltage and an alternating current according to the measurement frequency based on the measurement result of the voltage measurement step and the measurement result of the current measurement step, and outputs them to a higher-level system.

[0132] For example, in the above drive step, alternating current may be repeatedly supplied to the first battery and the second battery, and in each of these repetitions, the waveform of the first pulse when the alternating current is supplied may be switched.

[0133] For example, in the drive step, alternating current may be applied to the first battery and the second battery repeatedly, and in the AC detection step, the timing of starting the measurement of the AC voltage and AC current may be varied during each repetition.

[0134] For example, in the above drive step, alternating current may be repeatedly applied to the first battery and the second battery, and in the above voltage measurement step, the voltage of the first battery and the voltage of the second battery may be measured after a predetermined settling time from the moment when the state in which alternating current is applied to the first battery and the second battery switches from a state in which alternating current is applied to the first battery and the second battery to a state in which no alternating current is applied.

[0135] For example, this disclosure can be implemented as a program that causes a computer (processor) to execute the steps included in the drive measurement method. Furthermore, this disclosure can be implemented as a non-temporary computer-readable recording medium, such as a CD-ROM, on which the program is recorded.

[0136] For example, if this disclosure is implemented in a program (software), each step is executed by the program using hardware resources such as the computer's CPU, memory, and input / output circuits. In other words, each step is executed by the CPU obtaining data from memory or input / output circuits, performing calculations, and outputting the calculation results to memory or input / output circuits.

[0137] In the above embodiment, each component included in the drive measurement circuit may be implemented by dedicated hardware or by executing a software program suitable for each component. Each component may also be implemented by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0138] Some or all of the functions of the drive measurement circuit according to the above embodiment are typically implemented as an LSI, which is an integrated circuit. These may be individually integrated on a single chip, or some or all of them may be integrated on a single chip. Furthermore, the implementation is not limited to an LSI, but may also be implemented using a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connections and settings of circuit cells inside the LSI may also be used.

[0139] Furthermore, if advances in semiconductor technology or other derived technologies lead to the emergence of integrated circuit technologies that can replace LSIs, then naturally, those technologies may be used to integrate each component included in the drive measurement circuit into an integrated circuit.

[0140] Furthermore, this disclosure also includes forms obtained by applying various modifications to the embodiments that a person skilled in the art could conceive, and forms realized by arbitrarily combining the components and functions of each embodiment without departing from the spirit of this disclosure.

[0141] (Note) The above description of embodiments discloses the following technology.

[0142] (Technology 1) A drive measurement circuit for controlling an impedance measuring device for measuring the AC impedance of a first battery and a second battery connected in series, wherein the impedance measuring device comprises an inductor for storing or releasing electrical energy, a switching circuit consisting of a plurality of switching elements for intermittently moving current between the first battery and the second battery via the inductor, and current detection means for detecting the current of the first battery and the current of the second battery, and the drive measurement circuit comprises a current measuring unit for measuring the current of the first battery and the current of the second battery based on the detection result of the current detection means, a voltage measuring unit for measuring the voltage of the first battery and the voltage of the second battery, and AC impedance An AC detection unit that receives a measurement instruction signal including information on the measurement frequency from a higher-level system having a function to calculate the frequency, measures an AC voltage and an AC current corresponding to the measurement frequency based on the measurement result of the voltage measurement unit and the measurement result of the current measurement unit, and outputs them to the higher-level system; and a drive control unit that drives a plurality of switching elements to periodically change the state of current movement through the inductor according to the measurement frequency, thereby supplying the AC current to the first battery and the second battery, wherein the drive control unit repeatedly supplies the AC current to the first battery and the second battery and does not, and in each repetition, switches the waveform of the first pulse when the AC current is started from two or more types of waveforms.

[0143] According to this method, by repeatedly switching between applying and not applying AC current, and by switching the waveform of the first pulse when the AC current is started to apply, so that the polarity of the transient response of the voltage immediately after the start of current application for EIS measurement is reversed, even if there is a transient response to the voltage, the effect of the transient response can be canceled out by averaging the repeated measurement results, and the AC impedance can be measured with high accuracy. Therefore, it is not necessary to exclude the section in which the effect of the transient response of the voltage exists from the EIS measurement section, or the excluded section can be shortened, thus ensuring sufficient measurement time for EIS measurement.

[0144] (Technology 2) The drive measurement circuit according to Technology 1, wherein the two or more types of waveforms include a waveform with positive polarity and a waveform with negative polarity.

[0145] According to this, by repeatedly switching between applying and not applying alternating current, the polarity of the voltage transient response can be reversed by switching the polarity of the first pulse when the alternating current starts to flow between positive and negative.

[0146] (Technology 3) The drive measurement circuit according to Technology 1 or 2, wherein the two or more types of waveforms include a waveform with a shorter pulse width than the other waveforms.

[0147] According to this, by repeatedly switching between applying and not applying alternating current, the polarity of the transient response of the voltage can be reversed, similar to how the polarity of the initial pulse when the alternating current is applied can be reversed, by switching between a short pulse width and a normal pulse width.

[0148] (Technical 4) The AC detection unit starts measuring the AC voltage and AC current after a predetermined time period after the drive control unit starts driving the plurality of switching elements, according to any one of Technical 1 to 3.

[0149] Thus, the measurement of AC voltage and AC current may be started a predetermined time after the application of current for EIS measurement has begun.

[0150] (Technical 5) A drive measurement circuit for controlling an impedance measuring device for measuring the AC impedance of a first battery and a second battery connected in series, wherein the impedance measuring device comprises an inductor for storing or releasing electrical energy, a switching circuit consisting of a plurality of switching elements for intermittently moving current between the first battery and the second battery via the inductor, and current detection means for detecting the current of the first battery and the current of the second battery, and the drive measurement circuit comprises a current measuring unit for measuring the current of the first battery and the current of the second battery based on the detection result of the current detection means, a voltage measuring unit for measuring the voltage of the first battery and the voltage of the second battery, and AC impedance An AC detection unit receives a measurement instruction signal including information on the measurement frequency from a higher-level system having a function to calculate the frequency, and measures an AC voltage and AC current corresponding to the measurement frequency based on the measurement result of the voltage measurement unit and the measurement result of the current measurement unit, and outputs them to the higher-level system; and a drive control unit drives a plurality of switching elements to periodically change the state of current movement through the inductor according to the measurement frequency, thereby supplying the AC current to the first battery and the second battery, wherein the drive control unit repeatedly supplies the AC current to the first battery and the second battery and does not, and the AC detection unit changes the timing at which it starts measuring the AC voltage and the AC current during the repetition.

[0151] According to this method, by switching the timing of starting AC voltage and AC current measurements during repeated cycles of applying and not applying AC current, at the timing when the polarity of the AC voltage changes from negative to positive and from positive to negative, even if there is a transient response to the voltage, the effects of the transient response can be canceled out by averaging the repeated measurement results, allowing for highly accurate measurement of AC impedance. Therefore, the timing of starting AC voltage and AC current measurements can be set so that the section affected by the transient response of the voltage is short, and the section excluded from the EIS measurement section can be shortened, thus ensuring sufficient measurement time for the EIS measurement.

[0152] (Technical 6) The first battery and the second battery are each composed of two or more battery cells, and the voltage measuring unit simultaneously measures the voltage of each of the two or more battery cells, according to any one of Technical 1 to 5, in the drive measurement circuit.

[0153] Thus, each battery may consist of two or more battery cells.

[0154] (Technical 7) The AC detection unit further averages the multiple measurement results of the AC voltage and AC current measured in the repetition, according to any one of Technical 1 to 6.

[0155] According to this, the drive measurement circuit may have a function to average the results of multiple measurements of AC voltage and AC current.

[0156] (Technical 8) The drive measurement circuit according to any one of Technical 1 to 7, wherein the voltage measuring unit measures the voltage of the first battery and the voltage of the second battery after a predetermined settling time from the timing when the AC current switches from a state in which the AC current flows to the state in which it does not flow to the first battery and the second battery.

[0157] In the repeated switching between applying and not applying alternating current, the battery voltage is affected by the EIS measurement after the timing when the AC current switches from flowing to not flowing, making it impossible to measure the correct battery voltage. Therefore, by measuring the battery voltage after a predetermined settling time from the timing when the AC current switches from flowing to not flowing, the battery voltage can be measured with high accuracy.

[0158] (Technical 9) A drive measurement method for controlling an impedance measuring device for measuring the AC impedance of a first battery and a second battery connected in series, wherein the impedance measuring device comprises an inductor for storing or releasing electrical energy, a switching circuit consisting of a plurality of switching elements for intermittently moving current between the first battery and the second battery through the inductor, and current detection means for detecting the current of the first battery and the current of the second battery, and the drive measurement method comprises a power receiving step of receiving a measurement instruction signal including information on the measurement frequency from a higher-level system having a function for calculating AC impedance, and driving the plurality of switching elements to periodically change the state of current movement through the inductor according to the measurement frequency. A drive measurement method comprising: a drive step of supplying alternating current to the first battery and the second battery; a current measurement step of measuring the current of the first battery and the current of the second battery based on the detection result of the current detection means; a voltage measurement step of measuring the voltage of the first battery and the voltage of the second battery; and an AC detection step of measuring an AC voltage and an AC current corresponding to the measurement frequency based on the measurement result of the voltage measurement step and the measurement result of the current measurement step and outputting them to the higher-level system, wherein the drive step repeatedly supplies the alternating current to the first battery and the second battery and does not supply it, and in the repeated steps, the waveform of the first pulse when the alternating current is supplied is switched from two or more types of waveforms.

[0159] This provides a drive measurement method that can ensure sufficient measurement time for EIS measurement.

[0160] (Technical 10) A drive measurement method for controlling an impedance measuring device for measuring the AC impedance of a first battery and a second battery connected in series, wherein the impedance measuring device comprises an inductor for storing or releasing electrical energy, a switching circuit consisting of a plurality of switching elements for intermittently moving current between the first battery and the second battery through the inductor, and current detection means for detecting the current of the first battery and the current of the second battery, and the drive measurement method comprises a power receiving step of receiving a measurement instruction signal including information on the measurement frequency from a higher-level system having a function for calculating AC impedance, and driving the plurality of switching elements to periodically change the state of current movement through the inductor according to the measurement frequency. A drive measurement method comprising: a drive step of supplying alternating current to the first battery and the second battery; a current measurement step of measuring the current of the first battery and the current of the second battery based on the detection result of the current detection means; a voltage measurement step of measuring the voltage of the first battery and the voltage of the second battery; and an AC detection step of measuring an alternating voltage and an alternating current corresponding to the measurement frequency based on the measurement result of the voltage measurement step and the measurement result of the current measurement step, and outputting them to the higher-level system, wherein the drive step repeatedly supplies and does not supply the alternating current to the first battery and the second battery, and the AC detection step differs the timing of starting the measurement of the alternating voltage and the alternating current in the repeated steps.

[0161] This provides a drive measurement method that can ensure sufficient measurement time for EIS measurement.

[0162] This disclosure is useful as a system for detecting battery abnormalities and estimating their state based on the battery's internal impedance, such as for battery degradation diagnosis and temperature estimation.

[0163] 1, 1a, 1b Impedance measuring device 2, 2a, 2b Drive measuring circuit 11 First switching element 12 Second switching element 13 Current interruption means 14 Inductor 15, 16 Detection resistor 20 Voltage measuring unit 21 Current measuring unit 22, 22a, 22b AC detection unit 23, 23a, 23b Drive control unit 24 Current polarity control unit 25 Current pulse width control unit 26 Measurement start phase control unit 100, 100a, 100b Battery monitoring system 200, 200a, 200b MCU 203, 204, 205 Repeat measurement control unit 220 Signal generation unit 221 Conversion unit 222 Integration unit 223 Holding unit 224 Communication unit 230 Oscillator 231, 232 Reference voltage source 233, 234 Comparator 235 OR circuit 236 SR latch 237, 238 Switch circuit 239 Anomaly detection circuit 240 Inverter 241, 242, 243 AND circuit B1, B2 Battery

Claims

1. A drive measurement circuit for controlling an impedance measuring device for measuring the AC impedance of a first battery and a second battery connected in series, wherein the impedance measuring device comprises an inductor for storing or releasing electrical energy, a switching circuit consisting of a plurality of switching elements for intermittently moving current between the first battery and the second battery via the inductor, and current detection means for detecting the current of the first battery and the current of the second battery, wherein the drive measurement circuit comprises a current measuring unit for measuring the current of the first battery and the current of the second battery based on the detection result of the current detection means, a voltage measuring unit for measuring the voltage of the first battery and the voltage of the second battery, and an AC detection unit that receives a measurement instruction signal including information on the measurement frequency from a higher-level system having a function for calculating AC impedance, and measures an AC voltage and AC current corresponding to the measurement frequency based on the measurement result of the voltage measuring unit and the measurement result of the current measuring unit and outputs them to the higher-level system. A drive control unit drives a plurality of switching elements to periodically change the state of current movement through the inductor according to the measurement frequency, thereby supplying the alternating current to the first battery and the second battery, wherein the drive control unit repeatedly switches between supplying and not supplying the alternating current to the first battery and the second battery, and in each repetition, switches the waveform of the first pulse when the alternating current is started from two or more types of waveforms.

2. The drive measurement circuit according to claim 1, wherein the two or more types of waveforms include a waveform with positive polarity and a waveform with negative polarity.

3. The drive measurement circuit according to claim 1 or 2, wherein the two or more waveforms include a waveform with a shorter pulse width than the other waveforms.

4. The drive measurement circuit according to any one of claims 1 to 3, wherein the AC detection unit starts measuring the AC voltage and AC current after a predetermined time period after the drive control unit starts driving the plurality of switching elements.

5. A drive measurement circuit for controlling an impedance measuring device for measuring the AC impedance of a first battery and a second battery connected in series, wherein the impedance measuring device comprises an inductor for storing or releasing electrical energy, a switching circuit consisting of a plurality of switching elements for intermittently moving current between the first battery and the second battery via the inductor, and current detection means for detecting the current of the first battery and the current of the second battery, the drive measurement circuit comprises a current measuring unit for measuring the current of the first battery and the current of the second battery based on the detection result of the current detection means, a voltage measuring unit for measuring the voltage of the first battery and the voltage of the second battery, and an AC detection unit that receives a measurement instruction signal including information on the measurement frequency from a higher-level system having a function for calculating AC impedance, and measures an AC voltage and AC current corresponding to the measurement frequency based on the measurement result of the voltage measuring unit and the measurement result of the current measuring unit and outputs them to the higher-level system. A drive control unit drives a plurality of switching elements to periodically change the state of current movement through the inductor according to the measurement frequency, thereby supplying the alternating current to the first battery and the second battery, wherein the drive control unit repeatedly supplies and does not supply the alternating current to the first battery and the second battery, and the AC detection unit varies the timing at which it starts measuring the alternating voltage and the alternating current during the repeated cycles.

6. The drive measurement circuit according to any one of claims 1 to 5, wherein the first battery and the second battery are each composed of two or more battery cells, and the voltage measurement unit simultaneously measures the voltage of each of the two or more battery cells.

7. The drive measurement circuit according to any one of claims 1 to 6, wherein the AC detection unit further averages the multiple measurement results of the AC voltage and AC current measured in the repetition.

8. The drive measurement circuit according to any one of claims 1 to 7, wherein the voltage measuring unit measures the voltage of the first battery and the voltage of the second battery after a predetermined settling time from the timing when the AC current switches from a state in which the AC current flows through the first battery and the second battery to a state in which it does not flow.

9. A drive measurement method for controlling an impedance measuring device for measuring the AC impedance of a first battery and a second battery connected in series, wherein the impedance measuring device comprises an inductor for storing or releasing electrical energy, a switching circuit consisting of a plurality of switching elements for intermittently moving current between the first battery and the second battery via the inductor, and current detection means for detecting the current of the first battery and the current of the second battery, and the drive measurement method comprises: a power receiving step of receiving a measurement instruction signal including information on the measurement frequency from a higher-level system having a function for calculating AC impedance; a drive step of driving the plurality of switching elements to periodically change the state of current movement via the inductor according to the measurement frequency, thereby flowing AC current to the first battery and the second battery; a current measurement step of measuring the current of the first battery and the current of the second battery based on the detection result of the current detection means; and a voltage measurement step of measuring the voltage of the first battery and the voltage of the second battery. A drive measurement method comprising: an AC detection step which measures an AC voltage and an AC current corresponding to the measurement frequency based on the measurement result in the voltage measurement step and the measurement result in the current measurement step and outputs them to the higher-level system, wherein the drive step repeatedly switches between supplying and not supplying the AC current to the first battery and the second battery, and in each repetition, switches the waveform of the first pulse when the AC current is started to flow from two or more types of waveforms.

10. A drive measurement method for controlling an impedance measuring device for measuring the AC impedance of a first battery and a second battery connected in series, wherein the impedance measuring device comprises an inductor for storing or releasing electrical energy, a switching circuit consisting of a plurality of switching elements for intermittently moving current between the first battery and the second battery via the inductor, and current detection means for detecting the current of the first battery and the current of the second battery, the drive measurement method comprising: a power receiving step of receiving a measurement instruction signal including information on the measurement frequency from a higher-level system having a function for calculating AC impedance; a drive step of driving the plurality of switching elements to periodically change the state of current movement via the inductor according to the measurement frequency, thereby flowing AC current to the first battery and the second battery; a current measurement step of measuring the current of the first battery and the current of the second battery based on the detection result of the current detection means; and a voltage measurement step of measuring the voltage of the first battery and the voltage of the second battery. A drive measurement method comprising: an AC detection step which measures an AC voltage and an AC current corresponding to the measurement frequency based on the measurement result in the voltage measurement step and the measurement result in the current measurement step and outputs them to the higher-level system, wherein the drive step repeatedly switches between supplying and not supplying the AC current to the first battery and the second battery, and in the AC detection step, the timing of starting the measurement of the AC voltage and the AC current is varied in the repetition.

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