JP6868347B2 - Impedance measuring device and impedance measuring method - Google Patents

Description

The present invention relates to an impedance measuring device and an impedance measuring method.

As a method of measuring the internal impedance of an element constituting an electric circuit, there is an AC impedance measuring method in which an AC signal is given to a sample to be measured and the electric response thereof is measured. In this method, the magnitudes of the resistance component, capacitance component, and inductance component of the sample can be investigated. In addition, what kind of equivalent circuit these components constitute in the sample, or the parameters of the equivalent circuit can be obtained.

As such an impedance measurement method, a sinusoidal measurement alternating current is supplied from a constant current source to the sample, and the voltage signal appearing on the sample is referred to as a reference signal (or reference signal) having the same frequency that synchronizes with the supplied measurement alternating current. ), There is an impedance measurement method using synchronous detection that reduces the influence of noise components appearing on the sample.
The following prior art documents are available for impedance measuring devices by synchronous detection.

Impedance measurement by synchronous detection will be described below with reference to FIG. FIG. 6 is a diagram illustrating a conventional impedance measuring device by synchronous detection.
The measured alternating current i is supplied from the constant current source 110 to the sample 111 (Device under test: DUT). Here, the sample 111 is a battery having an internal resistance Rx. The resistors (Rs) 112 are current detection resistors for detecting the current value of the measured alternating current i, and are inserted in series with the constant current source 110 and the sample 111. Reference numeral 115 is an amplifier that amplifies the detection signal (voltage signal) appearing on the sample 111 according to the measured alternating current i. Similarly, reference numeral 116 is an amplifier that amplifies the voltage signal detected by the current detection resistor (Rs) 112. The voltage detection signal v ₁ amplified by the amplifier 115 is input to the synchronous detector 120 through a band pass filter (BPF: Band Pass Filter) 117 that passes the measurement frequency. The reference signal v ₂ to synchronize the measuring alternating current i is input to the synchronous detector 120 is amplified by the amplifier 116. Synchronous detector 120 synchronously detects the voltage detection signal _{v 1} by the reference signal _{v 2,} the detection output, the AC component low pass filter for removing (Low-Pass Filter: LPF) 122 is inputted AC component is It is removed and input to an analog-to-digital converter (ADC) 123. The analog-to-digital converter 123 converts the synchronous detection output into a digital signal. The converted digital signal is input to an arithmetic unit (not shown), the AC impedance value of the sample 111, the parameters of the equivalent circuit, etc. are calculated, and these values are displayed or printed on a display device (not shown) and output. Will be done.

Next, the impedance measurement operation in the impedance measuring device of FIG. 6 will be described.
From the constant current source 110, _{a sine wave of i = Isin (ω 1} t) is applied to the sample 111 as the measured alternating current. At both ends of the sample 111, voltage corresponding to the internal resistance R _X of the battery occurs, the voltage is output as v _{1 =} iR _X is amplified by the amplifier 115. Further, from the amplifier 116, it is _v 2 = iR _S corresponding to the current detection resistor _{R S} is output and synchronous detection by the synchronous detector 120. Here, v ₁ and v ₂ can be obtained by the following mathematical formulas (1) and (2), respectively. In addition, k is a constant (I and _RS are assumed to be constant).

The synchronous detection output can be obtained by the following mathematical formula (3).

交流成分をローパスフィルタで遮断すると、アナログデジタル変換器１２３の入力は、以下の数式（４）により求めることができる。

When the AC component is blocked by the low-pass filter, the input of the analog-to-digital converter 123 can be obtained by the following mathematical formula (4).

数式（４）より以下の数式（５）を導き、試料の抵抗値Ｒ_Ｘを求めることができる。

Lead to from the following equation (5) Equation (4), it is possible to obtain the resistance value R _X of the sample.

In this way, the voltage detection signals across the sample are synchronously detected with a reference signal in phase with the measured AC current, and the AC component (cos (2ω ₁ t)) is removed by a low-pass filter to extract only the DC component. Therefore, the effective impedance of the sample to be measured containing components other than the pure resistance such as a battery can be obtained. Further, since the AC component appearing in the synchronous detection is removed by the low-pass filter, the influence of the AC noise can be removed, and a minute signal buried in the noise can be taken out.

JP-A-2007-132806

By the way, when the signal passes through the bandpass filter 117 and its peripheral devices, the gain may fluctuate or the phase may rotate (fluctuate). If the gain or phase fluctuates, an error will occur in the obtained measured value, and as a result, the measured value will vary, causing a problem that the measured value is not stable.

An object of the present invention is to provide an impedance measuring device and a measuring method capable of stable measurement by reducing the influence caused by gain and phase fluctuations and reducing measurement errors.

The first aspect of the impedance measuring apparatus according to the present invention is an AC source that supplies a measurement signal of a predetermined frequency to a sample to be measured, a reference signal generation unit that generates a first reference signal synchronized with the measurement signal, and the like. A phase adjuster that generates a second reference signal whose phase is different from that of the first reference signal, a bandpass filter that passes at least a detection signal that appears in the sample, and a detection that appears in the sample as a signal input to the bandpass filter. A first selection unit that selects and outputs either a signal or a first reference signal, an output signal output from a bandpass filter using the output signal of the first selection unit as an input, and a first reference signal. A second selection unit that selects and outputs one of the above, a third selection unit that selects and outputs one of the output signal of the second selection unit and the second reference signal, and at least the third selection unit. A first synchronous detection unit that synchronously detects the output signal of the second selection unit with the first reference signal, and a second synchronous detection unit that synchronously detects the output signal of at least the second selection unit with the output signal of the third selection unit. An impedance measuring device including a synchronous detection unit, a first synchronous detection unit, and a calculation unit provided on the output side of the second synchronous detection unit, and a first reference signal is generated by a second selection unit. When selected and the second reference signal is selected by the third selection unit, the first synchronous detection unit synchronously detects the output signal of the second selection unit with the first reference signal, and the second The synchronous detection unit of is synchronously detects the output signal of the second selection unit with the second reference signal, and the arithmetic unit is the first based on the detection output of the first synchronous detection unit and the second synchronous detection unit. The phase difference between the reference signal and the second reference signal is calculated, the first selection section selects the first reference signal to be input to the bandpass filter, and the second selection section selects the first reference signal from the bandpass filter. When the output signal is selected and the output signal from the bandpass filter is selected by the third selection unit to be input to the second synchronous detection unit, the first synchronous detection unit is selected from the bandpass filter. The output signal of the above is synchronously detected by the first reference signal, the second synchronous detection unit synchronously detects the output signal from the band path filter as a reference signal, and the arithmetic unit performs the first synchronous detection unit and the first synchronous detection unit. The gain and phase rotation of the bandpass filter are calculated based on the detection output of the synchronous detection unit of 2, and the detection signal appearing on the sample is selected by the first selection unit to be output to the bandpass filter, and the second selection unit is used. The output signal from the bandpass filter is selected by the selection unit, and the second reference signal is selected by the third selection unit. When selected, the first synchronous detection unit synchronously detects the output signal from the bandpass filter with the first reference signal, and the second synchronous detection unit synchronously detects the output signal from the bandpass filter with the second reference signal. Synchronous detection is performed using the reference signal of the above, and the calculation unit calculates the impedance of the sample based on the detection outputs of the first synchronous detection unit and the second synchronous detection unit.

The first selection unit selects the first reference signal to be input to the bandpass filter, the second selection unit selects the output signal from the bandpass filter, and the third selection unit selects the output signal from the bandpass filter. When the second reference signal is selected by, the first synchronous detection unit synchronously detects the output signal from the bandpass filter with the first reference signal, and the second synchronous detection unit performs the bandpass filter. The output signal from is synchronously detected by the second reference signal, and the arithmetic unit calculates the phase circumference polarity of the bandpass filter based on the detection outputs of the first synchronous detection unit and the second synchronous detection unit. It is characterized in that it is determined whether the phase circumference of the bandpass filter is a delayed phase or a leading phase based on the calculated polarity.

It is preferable that the sample is a battery and the AC supply unit is a constant current source.

Another aspect of the present invention includes the steps of providing a measurement signal of a predetermined frequency to the sample of the AC source is measured, a step of the reference signal generating unit generates a first reference signal synchronized with the measurement signal, the phase adjustment A step of generating a second reference signal whose phase is different from that of the first reference signal, a step of passing a detection signal at least appearing in the sample by the bandpass filter, and a first selection section of the bandpass filter. A band path filter in which one of the detection signal appearing in the sample and the first reference signal is selected and output as an input signal, and the second selection unit receives the output signal of the first selection unit as an input signal. The step of selecting and outputting one of the output signal and the first reference signal output from the third selection unit, and the third selection unit selects either the output signal of the second selection unit or the second reference signal. And the step that the first synchronous detection unit synchronously detects the output signal of at least the second selection unit with the first reference signal, and the second synchronous detection unit is at least the second selection unit. An impedance measurement method comprising a step of synchronously detecting an output signal with the output signal of a third selection unit and a step of measuring the AC impedance of a sample by the calculation unit, wherein the second selection unit is a first reference signal. Is selected, and when the third selection unit selects the second reference signal, the first synchronous detection unit synchronously detects the output signal of the second selection unit with the first reference signal, and the second The synchronous detection unit of the second selection unit synchronously detects the output signal of the second selection unit with the second reference signal, and the calculation unit performs the first synchronous detection unit based on the detection outputs of the first synchronous detection unit and the second synchronous detection unit. It has a step of calculating the phase difference between the reference signal and the second reference signal, the first selection section selects so that the first reference signal is input to the band path filter, and the second selection section is the band. When the output signal from the path filter is selected and the third selection unit selects to input the output signal from the band path filter to the second synchronous detection unit, the first synchronous detection unit sets the band. The output signal from the path filter is synchronously detected by the first reference signal, the second synchronous detection unit synchronously detects the output signal from the band path filter as a reference signal, and the arithmetic unit performs the first synchronous detection unit. And a step of calculating the gain and phase rotation of the bandpass filter based on the detection output of the second synchronous detection section, so that the first selection section outputs the detection signal appearing on the sample to the bandpass filter. Select to, the second selection selects the output signal from the bandpass filter, and the third When the selection unit selects the second reference signal, the first synchronous detection unit synchronously detects the output signal from the band path filter with the first reference signal, and the second synchronous detection unit performs the band path. The output signal from the filter is synchronously detected by the second reference signal, and the calculation unit has a step of calculating the impedance of the sample based on the detection outputs of the first synchronous detection unit and the second synchronous detection unit. It is characterized by.

The first selection unit selects the first reference signal to be input to the bandpass filter, the second selection unit selects the output signal from the bandpass filter, and the third selection unit. When the unit selects the second reference signal, the first synchronous detection unit synchronously detects the output signal from the bandpass filter with the first reference signal, and the second synchronous detection unit performs the bandpass filter. The output signal from is synchronously detected by the second reference signal, and the arithmetic unit calculates the polarity around the phase of the bandpass filter based on the detection outputs of the first synchronous detection unit and the second synchronous detection unit. It has a step of determining whether the phase rotation of the bandpass filter is a delayed phase or a leading phase based on the calculated polarity.

It is possible to provide an impedance measuring device and a measuring method capable of stable measurement by reducing the influence caused by the fluctuation of gain and phase, reducing the measurement error.

It is a figure which showed the structure of the impedance measuring apparatus which concerns on one Embodiment of this invention, and showed the 1st connection structure mode. It is a figure which showed the 2nd connection structure mode for obtaining the gain G _{BPF of a} bandpass filter, and the phase rotation θ _BPF. It is a figure which showed the 3rd connection configuration mode for determining whether the phase _rotation θ BPF obtained in the 2nd connection configuration mode is a lag phase or a lead phase. It is a diagram showing a fourth connection configuration mode for obtaining the effective resistance R _X. It is a figure which showed the structure of the impedance measuring apparatus which concerns on the modification of this invention. It is a figure which shows the structure of the impedance measuring apparatus using the conventional synchronous detection.

Embodiments of the present invention will be described below with reference to the drawings. The impedance measuring device 1 includes a constant current source 10, amplifiers 15, 16, switch SW1, bandpass filter (BPF) 17, phase adjuster 19, switch SW2, switch SW3, synchronous detectors 20-1, 20-2, and low pass. It is configured to include a filter (LPF) 22-1,22-2 and an analog-to-digital converter (ADC) 23-1,32-2. The constant current source 10 corresponds to the AC supply unit according to claim 1, and the synchronous detector 20 corresponds to the synchronous detector unit according to claim 1.

In the impedance measuring device according to the embodiment of the present invention, the first to fourth connection configuration modes are generated depending on the mode of selecting (switching) the switches SW1 to SW3. Here, the switch SW1 selects either the output of the amplifier 15 or the output of the amplifier 16. The switch SW2 selects either the output of the bandpass filter (BPF) 17 or the output of the amplifier 16. The switch SW3 selects either the output of the switch SW2 or the output of the phase adjuster 19. The switches SW1 to SW3 correspond to the selection unit of claim 2.
Therefore, in the following, the first connection configuration mode, the second connection configuration mode, the third connection configuration mode, and the fourth connection configuration mode will be described separately.

Here, the first connection configuration mode is a connection configuration mode in which the output of the amplifier 15 is selected by SW1, the output of the amplifier 16 is selected by SW2, and the output of the phase adjuster 19 is selected by the switch SW3 (FIG. 1). The second connection configuration mode is a connection configuration mode in which the output of the amplifier 16 is selected by SW1, the output of the bandpass filter (BPF) 17 is selected by SW2, and the output of switch SW2 is selected by switch SW3 (FIG. 2). The third connection configuration mode is a connection configuration mode in which the output of the amplifier 16 is selected by SW1, the output of the bandpass filter (BPF) 17 is selected by SW2, and the output of the phase adjuster 19 is selected by the switch SW3. (See FIG. 3). The fourth connection configuration mode is a connection configuration mode in which the output of the amplifier 15 is selected by SW1, the output of the bandpass filter (BPF) 17 is selected by SW2, and the output of the phase adjuster 19 is selected by the switch SW3. (See FIG. 4).

[First connection configuration mode]
FIG. 1 is a diagram showing a configuration of an impedance measuring device according to an embodiment of the present invention and showing a first connection configuration mode.

The constant current source 10 is connected to the sample (DUT) 11 to be measured via a pair of output terminals (not shown). In this embodiment, the sample 11 is a battery and has R _x as an internal resistance. _{A current detection resistor R s} is inserted (connected) between the constant current source 10 and the sample 11, and the detection signal of the sample 11 is input to a bandpass filter (BPF) 17 that passes the measurement frequency via the amplifier 15. Will be done. The current detection resistor R _s corresponds to the reference signal generation unit of claim 1.

The amplifier 15 amplifies the detection signal (voltage signal) appearing in the sample 11 according to the measured alternating current i supplied from the constant current source 10, and the amplifier 16 amplifies the voltage signal detected by the _{current detection resistor RS.} To do. Voltage detection signal amplified by the amplifier 15 v ₁ is in this connection configuration mode not input to the synchronous detector 20. The measured alternating current i corresponds to the measurement signal of claim 1.

The current detection resistor _RS is connected to the amplifier 16. The output amplified by the amplifier 16 is input to the synchronous detectors 20-1 and 20-2 via the switch SW2, and is synchronized with the measured alternating current i and has the same phase as the measured alternating current i. It is input to the synchronous detector 20-1 as a signal (hereinafter referred to as "first reference signal") v _{2 (see the following formula (6)).}

Further, the output amplified by the amplifier 16 (measured current detection signal), the phase adjuster 19, a second reference signal (hereinafter, referred to as a "second reference signal".) Through the switch SW3 v ₃ as the synchronization It is input to the detector 20-2. The phase adjuster 19 adjusts the phase of the output signal of the amplifier 16 so that the phase has a phase difference of a predetermined angle with respect to the other reference signal (θ _{2 in} this example). Note that θ ₂ is _{other than θ 2} ≠ θ ₁ and θ ₁ + π.

The detection outputs of the synchronous detectors 20-1 and 20-2 are input to the low-pass filter (LPF) 22-1,22-2, respectively, and the output of the low-pass filter 22-1,22-2 from which the AC component is removed is , Are input to the analog-to-digital converters (ADCs) 23-1 and 23-2, respectively.

The analog-digital converters 23-1 and 23-2 convert the synchronous detection output into a digital signal. The converted digital signal is input to an arithmetic unit (not shown), the AC impedance value of the sample 11 and the parameters of the equivalent circuit are calculated, and these values are displayed or printed on a display device (not shown) and output. Will be done.

In the first connection configuration mode, the phase difference θ _{1-2 of the first reference signal v 2} and the second reference signal v ₃ is obtained, and the calculation procedure will be described in detail below.

In the first reference signal v ₂ described above, theta _I is a phase rotation by the amplifier (detection circuit) 16, it is assumed no phase around the amplifier _{16 (θ I = 0 °)} . This is because if there is a phase rotation, it can be canceled by the initial adjustment. Therefore, the first reference signal v ₂ is obtained by the following mathematical formula (7).

First, from the output of the amplifier 16, the first reference signal (in phase with the measured alternating current i) v ₂ and (see the following mathematical formula (8)), and the _second reference signal v 2 having a phase different from that of the first reference signal v 2. A signal v ₃ (see equation (9) below) is generated.

Next, the measured alternating current i is synchronously detected by _{the first reference signal v 2} and the second reference signal v _3. In the synchronous detection of the first reference signal _{v 2,} the input voltage _{V ADC1_V2 × V2} of ADCs 23-1, determined using the following equation (10).

これより、測定交流電流ｉの振幅値Ｉは以下の数式（１１）を用いて求められる。

From this, the amplitude value I of the measured alternating current i can be obtained by using the following mathematical formula (11).

第２の参照信号ｖ _３ との同期検波においてＡＤＣ２３−２の入力電圧Ｖ_{ＡＤＣ２＿Ｖ２×Ｖ３}は以下の数式（１２）を用いて求められる。

Input voltage _{V ADC2_V2 × V3} of ADC23-2 in synchronous detection of the second reference signal v ₃ is obtained using the following equation (12).

Note that θ _1-2 is the phase difference between the first reference signal v ₂ and the second reference signal v ₃ , and the following mathematical formula (13) derived by the mathematical formula (12) ÷ mathematical formula (10) is used. Desired. The lag phase and the lead phase are known because they can be arbitrarily set by the phase adjuster 19.

[Second connection configuration mode]
In the second connection configuration mode, the gain G _BPF and the phase rotation θ _BPF of the bandpass filter 17 are obtained, and the calculation procedure will be described in detail below with reference to FIG.

The output v _{2'of the} bandpass filter 17 is obtained by using the following mathematical formula (15).

Further, to generate a third reference signal v _index3 of the output v _2'same phase. In this connection configuration mode, the third reference signal v _index3 becomes equal to the output v _2'of the band-pass filter 17. Here, the output v _2'of the band-pass filter 17, to synchronous detection by the first reference signal v ₂ and the third reference signal v _index3. Input voltage _{V ADC1_V2' × V2} of ADC23-1 when the synchronous detection output _{v 2'first} reference signal _{v 2} is determined using the following equation (16).

In the synchronous detection with the third reference signal v _INDEX3 , the input voltage V _{ADC2_V2 ′ × V2 ′} of the ADC 23-2 is obtained by using the following mathematical formula (17).

When the formula (17) ÷ formula (10) is executed, the following formula (18) is derived.

Therefore, the gain G _BPF can be obtained by using the following mathematical formula (19).

Further, when the mathematical formula (16) ÷ the mathematical formula (17) is executed, the following mathematical formula (20) is obtained, and when the denominator on the right side of the mathematical formula (20) is taken, the following mathematical formula (21) is obtained.

The following mathematical formula (22) is derived from the mathematical formula (21), and the phase rotation θ _BPF is obtained from the mathematical formula (22).

[Third connection configuration mode]
In the third connection configuration mode, it is _{determined whether the phase rotation θ BPF} obtained in the second connection configuration mode is the lag phase or the lead phase. The determination procedure is described below with reference to FIG. This will be described in detail.

_{For the phase rotation θ BPF} obtained in the second connection configuration mode, only the solution of the phase angle 0 ≦ θ ≦ π can be obtained. Since the phase rotation θ _BPF of the bandpass filter 17 may be in the range of −π <θ <0 because there is a possibility of either a delayed phase or a leading phase, it is necessary to determine which one it is. is there.
First, synchronous detection output _{v 2'of} the band-pass filter 17 at the second reference signal _{v 3.} The input voltage V _{ADC2_V2'x V3} of the ADC 23-2 at that time can be obtained by using the following mathematical formula (23).

The following mathematical formula (24) is obtained by the mathematical formula (23) ÷ mathematical formula (16).

The denominators of the left and right sides of the formula (24) are calculated as the following formula (25), which is expanded into the formulas (26), (27), and (28), and the phase rotation θ _BPF is the following formula (29). More demanded.

Here, when 0 <| θ _BPF | ≤ π / 2,
If X> 0, _{the polarity of the phase rotation θ BPF} is +, and if X <0, the polarity of the _{phase rotation θ BPF is −.}
Also, when π / 2 << | θ _BPF | <π,
If X <0, _{the polarity of the phase rotation θ BPF} is +, and if X> 0, the polarity of the _{phase rotation θ BPF is −.} Therefore, when the phase rotation θ _BPF is 0 and when the phase rotation θ _BPF is π, the polarity determination is not necessary.

[Fourth connection configuration mode]
In the fourth connection configuration form, but obtains the effective resistance R _X, with reference to FIG. 4 explaining the calculation procedure in detail below. First, to detect the voltage across _{v 1} of the specimen 11 by the following equation (30).

Here, θ _{IV is the phase difference between the voltage v 1} across the sample 11 and the measured alternating current i, and θ _AMP is the phase circumference of the amplifier 15. In this embodiment, θ _AMP is set to 0 °. This is because when there is a phase rotation, it can be canceled by the initial adjustment. Therefore, the voltage across v ₁ can be obtained by using the following mathematical formula (31).

_{The output v 1'of the} bandpass filter (BPF) 17 is obtained by using the following mathematical formula (32).

_{The output v 1'of the} bandpass filter 17 is synchronously detected by the first reference signal v ₂ and the second reference signal v ₃ , and the amplitude and phase of the voltage generated at both ends of the sample 11 are obtained. The input voltage V _{ADC1_V1 ′ × V2} of the ADC 23-1 when the output v _{1 ′} is synchronously detected by the first reference signal v ₂ is obtained by using the following mathematical formula (33).

The input voltage V _{ADC2_V1 ′ × V3} of the ADC 23-2 when the output v _{1 ′} is synchronously detected by the second reference signal v ₃ is obtained by using the following mathematical formula (34).

When the formula (33) ÷ formula (34) is executed, the following formula (35) is derived.

The following formula (36) is obtained by taking the denominators of the left and right sides of the formula (35).

Further, when the left side is expanded, it becomes the following formula (37), and when the right side is expanded, it becomes the following formula (38).

As a result, the following mathematical formula (39) is derived, and when the left side of the mathematical formula (39) is replaced with _{tan (θ IV ), θ IV} can be obtained by using the following mathematical formula (40). Note that θ _IV is −π ≦ θ _IV ≦ π.

The amplitude of the voltage generated across the sample 11 (V = IR _X) is determined using equation (41) below obtained by modifying the above equation (33).

_{Then, the effective resistance RX} is obtained by using the following mathematical formula (42) obtained based on the above mathematical formula (41).

Regarding the selection (switching) by the switches SW1 to 3, in the above-described embodiment, the first connection configuration mode, the second connection configuration mode, the third connection configuration mode, and the fourth connection configuration mode are connected in this order. Switching is performed to change the configuration, but the order of switching is not limited to this. For example, since the impedance measurement in the fourth connection configuration mode may be performed after the measurement and determination are finally performed in all the first to third connection configuration modes, the order in which the first to third connection configuration modes are switched is sufficient. Can be changed as appropriate. Further, the switching may be performed according to the order stored in the memory in the arithmetic unit (not shown), or may be manually switched according to the measured value displayed on the display device (not shown).

[effect]
As described above, according to the present embodiment, the fluctuation amount of the gain and / or phase of the bandpass filter (BPF) 17 and its peripheral devices is calculated, and the measured gain and phase are used. Impedance is being measured. Therefore, even if the gain or phase of the bandpass filter (BPF) 17 or its peripheral device fluctuates, the influence of the gain fluctuation or phase rotation can be suppressed, so that measurement error can be reduced and stable measurement can be performed. Become.

<Modification example>
In the above embodiment, two synchronous detectors 20-1, 20-2 and two low-pass filters 22-1, 22-2 corresponding to them are used, but as shown in FIG. 5, one synchronous detector is used. The device 30 and one low-pass filter 32 and ADC 33 corresponding thereto may be used to perform measurement and determination in all of the first to fourth connection configurations. In that case, the measurement and determination relating to the first to fourth connection configurations are the same as described above, and thus the description thereof will be omitted here.

Further, the above-described embodiment has been described with an example in which an AC constant current is supplied from the constant current source 10 to the sample to measure the impedance, but impedance measurement by voltage is also possible. For example, the impedance may be measured by supplying a constant AC voltage from a voltage source to the sample and performing synchronous detection. When the measurement target is a battery, it is preferable to measure the impedance with a constant current, but for example, in the case of a capacitor incorporated in an electric circuit where noise may appear, the impedance measurement with an AC constant voltage may be used. ..

10 constant current source
11 Sample (DUT)
12 Current detection resistor (Rs)
15, 16 Amplifier 17 Bandpass Filter (BPF)
19 Phase adjuster 20-1, 20-2 Synchronous detector 22-1, 22-2 Low-pass filter (LPF)
23-1, 23-2 Analog-to-digital converter (ADC)
SW1 to SW3 switch

Claims (5)

An AC source that supplies a measurement signal of a predetermined frequency to the sample to be measured,
A reference signal generation unit that generates a first reference signal synchronized with the measurement signal,
A phase adjusting unit that generates a second reference signal whose phase is different from that of the first reference signal,
At least a bandpass filter that passes the detection signal appearing in the sample,
As a signal to be input to the bandpass filter, a first selection unit that selects and outputs either a detection signal appearing in the sample or the first reference signal, and
A second selection unit that selects and outputs either an output signal output from the bandpass filter or the first reference signal with the output signal of the first selection unit as an input, and a second selection unit.
A third selection unit that selects and outputs either the output signal of the previous second selection unit or the second reference signal, and the third selection unit.
At least the first synchronous detection unit that synchronously detects the output signal of the second selection unit with the first reference signal, and
At least a second synchronous detection unit that synchronously detects the output signal of the second selection unit with the output signal of the third selection unit, and
The first synchronous detection unit and the calculation unit provided on the output side of the second synchronous detection unit are
It is an impedance measuring device equipped with
When the first reference signal is selected by the second selection unit and the second reference signal is selected by the third selection unit, when the second reference signal is selected.
The first synchronous detection unit synchronously detects the output signal of the second selection unit with the first reference signal.
The second synchronous detection unit synchronously detects the output signal of the second selection unit with the second reference signal.
The calculation unit calculates the phase difference between the first reference signal and the second reference signal based on the detection outputs of the first synchronous detection unit and the second synchronous detection unit.
The first selection unit selects the first reference signal to be input to the bandpass filter, the second selection unit selects the output signal from the bandpass filter, and the third selection unit selects the output signal from the bandpass filter. When the selection unit selects the output signal from the bandpass filter to be input to the second synchronous detection unit,
The first synchronous detection unit synchronously detects the output signal from the bandpass filter with the first reference signal, and then performs synchronous detection.
The second synchronous detection unit synchronously detects the output signal from the bandpass filter as a reference signal.
The calculation unit calculates the gain and phase rotation of the bandpass filter based on the detection outputs of the first synchronous detection unit and the second synchronous detection unit.
The first selection unit selects the detection signal appearing in the sample to be output to the bandpass filter, the second selection unit selects the output signal from the bandpass filter, and the third selection unit selects the output signal from the bandpass filter. When the second reference signal is selected by the selection unit,
The first synchronous detection unit synchronously detects the output signal from the bandpass filter with the first reference signal, and then performs synchronous detection.
The second synchronous detection unit synchronously detects the output signal from the bandpass filter with the second reference signal, and then performs synchronous detection.
The calculation unit calculates the impedance of the sample based on the detection outputs of the first synchronous detection unit and the second synchronous detection unit.
An impedance measuring device characterized by the fact that. The first selection unit selects the first reference signal to be input to the bandpass filter, the second selection unit selects the output signal from the bandpass filter, and the third selection unit selects the output signal from the bandpass filter. When the second reference signal is selected by the selection unit,
The first synchronous detection unit synchronously detects the output signal from the bandpass filter with the first reference signal, and then performs synchronous detection.
The second synchronous detection unit synchronously detects the output signal from the bandpass filter with the second reference signal, and then performs synchronous detection.
The calculation unit calculates the polarity around the phase of the bandpass filter based on the detection outputs of the first synchronous detection unit and the second synchronous detection unit, and the bandpass filter is based on the calculated polarity. Determining whether the phase rotation of is a lagging phase or a leading phase.
The impedance measuring device according to claim 1. The sample is a battery and the alternating current source is a constant current source.
The impedance measuring apparatus according to claim 1 or 2. The step in which the AC source supplies a measurement signal of a predetermined frequency to the sample to be measured,
A step in which the reference signal generator generates a first reference signal synchronized with the measurement signal, and
A step in which the phase adjusting unit generates a second reference signal whose phase is different from that of the first reference signal.
The step that the bandpass filter passes at least the detection signal that appears in the sample,
A step in which the first selection unit selects and outputs either a detection signal appearing in a sample or a first reference signal as a signal to be input to the bandpass filter.
A step in which the second selection unit selects and outputs either the output signal output from the bandpass filter or the first reference signal with the output signal of the first selection unit as an input, and
A step in which the third selection unit selects and outputs either the output signal of the second selection unit or the second reference signal, and
A step in which the first synchronous detection unit synchronously detects at least the output signal of the second selection unit with the first reference signal.
A step in which the second synchronous detection unit synchronously detects at least the output signal of the second selection unit with the output signal of the third selection unit.
The arithmetic unit has a step of measuring the AC impedance of the sample.
Impedance measurement method
When the second selection unit selects the first reference signal and the third selection unit selects the second reference signal,
The first synchronous detection unit synchronously detects the output signal of the second selection unit with the first reference signal.
The second synchronous detection unit synchronously detects the output signal of the second selection unit with the second reference signal.
The calculation unit has a step of calculating the phase difference between the first reference signal and the second reference signal based on the detection outputs of the first synchronous detection unit and the second synchronous detection unit. ,
The first selection unit selects so that the first reference signal is input to the bandpass filter, the second selection unit selects an output signal from the bandpass filter, and the third selection unit selects the output signal from the bandpass filter. When the selection unit of is selected so that the output signal from the bandpass filter is input to the second synchronous detection unit,
The first synchronous detection unit synchronously detects the output signal from the bandpass filter with the first reference signal.
The second synchronous detection unit synchronously detects the output signal from the bandpass filter as a reference signal, and then performs synchronous detection.
The calculation unit has a step of calculating the gain and phase rotation of the bandpass filter based on the detection outputs of the first synchronous detection unit and the second synchronous detection unit.
The first selection unit selects so that the detection signal appearing in the sample is output to the bandpass filter, the second selection unit selects the output signal from the bandpass filter, and the third selection unit selects the output signal from the bandpass filter. When the selection unit of the above selects the second reference signal,
The first synchronous detection unit synchronously detects the output signal from the bandpass filter with the first reference signal.
The second synchronous detection unit synchronously detects the output signal from the bandpass filter with the second reference signal.
The calculation unit has a step of calculating the impedance of the sample based on the detection outputs of the first synchronous detection unit and the second synchronous detection unit.
An impedance measurement method characterized by this. The first selection unit selects so that the first reference signal is input to the bandpass filter, the second selection unit selects an output signal from the bandpass filter, and the third selection unit selects the output signal from the bandpass filter. When the selection unit of the above selects the second reference signal,
The first synchronous detection unit synchronously detects the output signal from the bandpass filter with the first reference signal, and then performs synchronous detection.
The second synchronous detection unit synchronously detects the output signal from the bandpass filter with the second reference signal, and then performs synchronous detection.
The calculation unit calculates the polarity around the phase of the bandpass filter based on the detection outputs of the first synchronous detection unit and the second synchronous detection unit, and the bandpass filter is based on the calculated polarity. Has a step of determining whether the phase circumference of is a lagging phase or a leading phase.
The impedance measuring method according to claim 4, wherein the impedance is measured.

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