JP2012163510A - Impedance measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an impedance measuring apparatus capable of measuring an internal impedance of a battery in a short period of time.SOLUTION: An impedance measuring apparatus 1 supplies a battery 30 of a measuring object with an alternating current Ifrom an AC supply 2 and measures the internal impedance of the battery 30 based on the supplied alternating current Iand an interpolar AC voltage Vgenerated between both the electrodes of the battery 30. In the impedance measuring apparatus, the AC supply 2 and the battery 30 are configured to be connected via a first DC voltage supply 3, a negative electrode of which is connected to the output end of the AC supply 2 and a positive electrode of which is connected to a positive electrode of the battery 30. The battery 30 and a differential amplifier may be connected via a second DC voltage supply 4.

Description

  The present invention relates to an impedance measuring apparatus that supplies an alternating current to a battery and measures the internal impedance of the battery from the alternating current and an alternating voltage generated between both electrodes of the battery.

  The battery generates a direct current electromotive force. For example, in addition to a primary battery such as a manganese battery or an alkaline manganese battery, a secondary battery such as a lead storage battery, a lithium ion storage battery, or a nickel cadmium storage battery, a fuel cell, a solar battery, or the like. There are various types of batteries. In order to evaluate the characteristics of such a battery, the value of the internal impedance (output impedance) of the battery is measured.

  Patent Document 1 describes an impedance measuring device capable of measuring the internal impedance of a battery. In this impedance measuring apparatus 1, an alternating current is supplied from a constant AC current source (AC source) to a battery via a capacitor, and an AC voltage generated at both extremes of the battery via a different capacitor is converted to a differential amplifier circuit (voltage detection). Circuit). These capacitors block direct current and prevent direct current voltage generated by the battery from being directly applied to an alternating current source or a differential amplifier circuit. Thereby, the internal impedance of the battery can be measured without destroying the AC source or the like regardless of the level of the battery voltage.

Japanese Patent Laid-Open No. 11-295363

  In the impedance measuring device of Patent Literature 1, when a battery is connected to the device, the capacitor is charged with a potential difference from the battery voltage. During the transition period until the capacitor is charged, the voltage input to the differential amplifier circuit exceeds the common-mode input voltage range due to the transient characteristics, and the output voltage of the differential amplifier circuit is saturated. I can't. This saturation period is particularly long when the direct current electromotive force of the battery is larger than the power supply voltage of the alternating current source or the differential amplifier circuit and the difference is large. In order to shorten the charging time (saturation period), it is conceivable to reduce the capacitance of the capacitor. However, if the capacitance of the capacitor on the AC source side is reduced, the capacitor becomes a load (resistance) of the AC source. Therefore, it is necessary to increase the power supply voltage of the AC source in order to allow the specified AC current to flow. Further, if the capacitance of the capacitor on the differential amplifier circuit side is reduced, the rotation of the phase of the AC signal is increased, so that the measurement accuracy is deteriorated. For this reason, since it is necessary to set a capacitor | condenser to a big electrostatic capacitance, charging time becomes long, the saturation period of a differential amplifier circuit becomes long, and there exists a subject that a measurement takes time.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an impedance measuring apparatus capable of measuring the internal impedance of a battery in a short time.

  An impedance measuring device according to claim 1, which is made to achieve the above object, supplies an alternating current from an alternating current source to a battery to be measured, and the supplied alternating current, and An impedance measuring device for measuring an internal impedance of the battery based on an AC voltage between both electrodes generated between both electrodes of the battery, wherein the AC source and the battery are connected to a negative electrode at an output terminal of the AC source. In addition, the battery is connected to a positive electrode of the battery via a first DC voltage source connected to the positive electrode.

  An impedance measuring device according to a second aspect is the one according to the first aspect, wherein the first DC voltage source is disposed inside a device housing in which the AC source is incorporated, or the device housing. It is arranged outside the apparatus housing so that it can be connected to the body by a cable.

  An impedance measuring device according to claim 3 is the impedance measuring device according to claim 1, wherein a second DC voltage source having a positive electrode connected to the positive electrode of the battery, a negative electrode of the battery, and the And a voltage detection circuit for detecting a voltage between the negative electrodes of the second DC voltage source, and measuring the AC voltage between both electrodes from the AC component of the output of the voltage detection circuit.

  An impedance measuring device according to a fourth aspect is the one according to the third aspect, wherein the second DC voltage source is disposed inside a device housing in which the voltage detection circuit is incorporated, or the device. It is arranged outside the apparatus casing so that a cable can be connected to the casing.

  The impedance measuring device according to claim 5 is the impedance measuring device according to claim 1 or 2, wherein the series resistance connected in series with a known resistance voltage dividing ratio connected between the two electrodes of the battery, A voltage detection circuit for detecting a voltage divided by a series resistor, and measuring the AC voltage between both electrodes from an AC component of an output of the voltage detection circuit.

  According to the impedance measuring apparatus of the present invention, since the AC source and the battery are connected without a capacitor, a transient phenomenon in which the capacitor is charged by the battery does not occur, and the measurement can be performed in a short time.

  Furthermore, since the voltage detection circuit and the battery are connected without a capacitor, a transient phenomenon in which the capacitor is charged by the battery does not occur, and the measurement can be performed in a short time.

  When the first DC voltage source or the second DC voltage source is built in the apparatus housing, it is convenient to carry the apparatus. Further, when the first DC voltage source or the second DC voltage source is arranged outside the device casing and can be connected to the cable, for example, the same type as a commercially available DC voltage source device or a battery to be measured is used. By connecting the battery to the device with a cable, it can be used as a first DC voltage source or a second DC voltage source.

It is a block diagram which shows the structure of the use condition of the impedance measuring apparatus to which this invention is applied. It is a block diagram which shows the structure of the use condition of the other impedance measuring apparatus to which this invention is applied.

  Hereinafter, although embodiment of this invention is described in detail, the scope of the present invention is not limited to these embodiment.

The impedance measuring apparatus 1 shown in FIG. 1 includes an AC source 2, a first DC voltage source 3, a second DC voltage source 4, a measuring unit 5, and a display unit 6, and the AC source 2 is connected to the battery 30 to be measured. supplying an alternating current I _AC from the supplied alternating current I _AC, and based on the electrode-to-electrode AC voltage V _AC generated between both electrodes of the battery 30, to measure the internal impedance R _BAT of the battery 30 by the 4-terminal type Is. In the drawing, an equivalent internal resistance 30 a is shown for the battery 30. The resistance value of the internal resistor 30a is the internal impedance _RBAT .

  The AC source 2 is an AC constant current source that outputs a constant current having an AC frequency of 1 kHz as an example. The AC source 2 and the battery 30 are connected via a DC voltage source 3. Specifically, as shown in the figure, the negative electrode of the DC voltage source 3 is connected to the output terminal of the AC source 2, and the positive electrode of the DC voltage source 3 is connected to the positive electrode of the battery 30 by the test probe 21a. The The other output terminal of the AC source 2 is connected to the negative electrode of the battery 30 by the test probe 21b and to the reference potential. As the AC source 2, an AC constant voltage source may be used.

The DC voltage source 3 is such that the voltage difference between the DC electromotive force (DC electromotive voltage) V _BAT of the battery 30 and the DC voltage V _DC1 output from the DC voltage source 3 is less than the maximum voltage that can be applied to the output of the AC source 2. DC voltage V _DC1 is output. If the DC voltage source 3 outputs a DC voltage V _DC1 substantially equal to the DC electromotive force V _BAT of the battery 30, the voltage difference between the two voltages is preferable. In this example, a battery similar to the battery 30 is used as the DC voltage source 3. In this case, the battery serving as the DC voltage source 3 can be replaced when exhausted. Note that a known DC constant voltage circuit may be used as the DC voltage source 3.

  The direct-current voltage source 3 may be disposed inside the device housing of the impedance measuring device 1 including the alternating current source 2, the measurement unit 5, and the display unit 6, or may be disposed outside the device housing. You may connect to the connector terminal provided in the apparatus housing | casing with an electric cable.

  The positive electrode of the second DC voltage source 4 is connected to the positive electrode of the battery 30 by the test probe 22a. The negative electrode of the DC voltage source 4 is connected to an inverting input terminal of a differential amplifier circuit 11 described later of the measurement unit 5. Further, the non-inverting input terminal of the differential amplifier circuit 11 is connected to the negative electrode of the battery 30 by the test probe 22b.

The DC voltage source 4 has a DC voltage V at which the voltage difference between the DC electromotive force V _BAT of the battery 30 and the DC voltage V _DC2 output from the DC voltage source 4 is less than the maximum voltage that can be input to the measuring unit 5 and measured. _DC2 is output. Specifically, the DC voltage source 4 is such that the voltage difference between the DC electromotive force V _BAT and the DC voltage V _DC2 is equal to or less than the maximum voltage (common-mode input voltage range) that can be input between both input terminals of the differential amplifier circuit 11. The DC voltage V _DC2 that does not saturate the output of the differential amplifier circuit 11 is output even when the interpolar _AC voltage V _AC is superimposed on the DC voltage V _DC2 . If the DC voltage source 4 outputs a DC voltage V _DC2 substantially equal to the DC electromotive force V _BAT of the battery 30, it is preferable because the voltage difference between the two voltages is reduced. In this example, a battery similar to the battery 30 is used as the DC voltage source 4. In this case, the battery serving as the DC voltage source 4 can be replaced when consumed. Note that a known DC constant voltage circuit may be used as the DC voltage source 4.

  The direct current voltage source 4 may be disposed inside the device housing of the impedance measuring device 1 including the alternating current source 2, the measurement unit 5, and the display unit 6, or may be disposed outside the device housing, You may connect to the connector terminal provided in the apparatus housing | casing with an electric cable.

  The measurement unit 5 includes a differential amplifier circuit 11, a BPF 12, an A / D converter 13, an arithmetic processing unit 14, and an A / D converter 15. The differential amplifier circuit 11 is an example of a voltage detection circuit according to the present invention, and the impedance between a pair of input terminals (in this case, an inverting input terminal and a non-inverting input terminal) is sufficiently high compared to a voltage detection target. The voltage waveform detection input circuit outputs a signal waveform of a voltage applied between the input terminals as it is or after being amplified with a desired amplification degree. In this case, the differential amplifier circuit 11 differentially amplifies the potential difference between the inverting input terminal and the non-inverting input terminal with a desired amplification level and outputs it. The BPF 12 connected to the output of the differential amplifier circuit 11 is a band-pass filter that passes an AC component of a frequency (1 kHz in this example) output from the AC source 2 and does not pass a DC component. The A / D converter 13 performs analog / digital conversion on the output signal of the BFF 12 and outputs the result to the arithmetic processing unit 14.

In addition, the AC source 2 detects the current waveform of the _AC current I _AC output from the AC source 2 by using a current detection resistor (not shown) as an example, and a current measurement terminal 18 that outputs a voltage waveform. Have. The A / D converter 15 performs analog / digital conversion on the output signal of the current measurement terminal 18 and outputs the result to the arithmetic processing unit 14.

As an example, the arithmetic processing unit 14 includes an arithmetic processing circuit such as a microprocessor or a CPU, and a storage unit such as a ROM incorporating an operation program thereof or a RAM storing an arithmetic result. Arithmetic processing unit 14, with taking into account the amplification degree of the differential amplifier circuit 11 from the output of the A / D converter 13 to measure the electrode-to-electrode AC voltage V _AC of the battery 30, from the output of the A / D converter 13 The AC current I _AC is measured, the internal impedance R _BAT of the battery 30 is calculated based on the amplitude and phase difference of the _AC voltage V _AC between the two electrodes and the AC current I _AC , and is output to the display unit 6. The display unit 6 is a liquid crystal display panel as an example.

  Next, the measurement operation of the impedance measuring apparatus 1 will be described.

First, as shown in FIG. 1, test probes 21a, 21b, 22a, and 22b are connected to a battery 30 to be measured. When the measurement is started, the AC source 2 outputs an _AC current I _AC . The alternating current I _AC flows in a closed loop formed by the alternating current source 2, the direct current voltage source 3, and the battery 30. Since the input impedance of the differential amplifier circuit 11 is high impedance, the alternating current I _AC does not flow to the DC voltage source 4 or the differential amplifier circuit 11.

The DC voltage applied between the output terminals of the AC source 2 by the connection of the battery 30 is (DC electromotive force V _BAT ) − (DC voltage V _DC1 ) because the DC voltage source 3 is connected. That is, the direct current electromotive force V _BAT of the battery 30 is not directly applied to the alternating current source 2, but a voltage that is different from the direct current voltage V _DC1 of the direct current voltage source 3 is applied. Since the voltage of this difference is set within a voltage range that can be applied to the AC source 2, the AC source 2 is not damaged. That is, by providing the DC voltage source 3, it is not necessary to provide a DC blocking capacitor as in the conventional Patent Document 1. For this reason, the saturation phenomenon of the differential amplifier circuit 11 due to the charging of the capacitor does not occur. Further, since the DC electromotive force V _BAT of the battery 30 is not applied to the AC source 2 as it is, the AC source 2 can be applied to an output such as an AC source whose circuit power supply voltage is higher than the DC electromotive force V _BAT. It is not necessary to use an AC source with a large maximum voltage. If the battery 30 and the DC power source 3 are similar batteries, it is preferable that the DC electromotive force V _BAT ≈DC voltage V _DC1 , and almost no DC voltage is applied to the AC source 2. Further, if the DC voltage source 3 is a DC constant voltage circuit capable of adjusting the output voltage, it is preferable because it can be adjusted to DC electromotive force V _BAT ≈DC voltage V _DC1 .

An AC voltage (AC voltage between both ends) V _AC is generated between both ends of the battery 30 due to the _AC current I _AC being supplied to the battery 30 and the AC current I _AC flowing through the internal resistance 30a of the battery 30. To do. Since the battery 30 itself generates a DC electromotive force V _BAT , the voltage V _DUT across the battery 30 is
Voltage between both ends V _DUT = DC electromotive force V _BAT + AC voltage between both ends V _AC
It becomes. The input voltage V _IN1 input between both input terminals of the differential amplifier circuit 11 is connected to the DC voltage source 4 between the battery 30 and the differential amplifier circuit 11.
Input voltage V _IN1 = Voltage between both ends V _DUT -DC voltage V _DC2
= DC electromotive force V _BAT + AC voltage V _AC across both ends-DC voltage V _DC2
It becomes.

That is, the direct current electromotive force V _BAT of the battery 30 is not applied to the differential amplifier circuit 11 in direct current, and a direct current voltage that is the difference between the direct current electromotive force V _BAT and the direct current voltage V _DC2 of the direct current voltage source 4 is applied. Is done. Since the voltage of this difference is set within a voltage range that can be input by the differential amplifier circuit 11, the differential amplifier circuit 11 is not damaged and an amplification operation (measurement) is possible. That is, by providing the DC voltage source 4, it is not necessary to provide a DC blocking capacitor, and therefore, the saturation phenomenon of the differential amplifier circuit 11 due to the charging of the capacitor does not occur. Further, since the DC electromotive force V _BAT of the battery 30 is not applied to the differential amplifier circuit 11 as it is, the differential amplifier circuit 11 is, for example, a differential amplifier circuit in which the power supply voltage of the circuit is higher than the DC electromotive force V _BAT. In addition, there is no need to use a differential amplifier circuit having a large maximum input voltage range.

If the battery 30 and the DC voltage source 4 are similar batteries, since the DC electromotive force V _BAT ≈DC voltage V _DC2 , almost no DC voltage is applied to the differential amplifier circuit 11 and the battery 30 Since the generated AC voltage V _AC between both ends is applied, it is preferable. Further, if the DC voltage source 4 is a DC constant voltage circuit capable of adjusting the output voltage, it is preferable because the DC electromotive force V _BAT ≈DC voltage V _DC2 can be adjusted.

The differential amplifier circuit 11 differentially amplifies the input voltage V _IN1 , and the BPF 12 passes only an AC component (AC voltage signal) having a frequency of 1 kHz. The A / D converter 13 converts the signal into a digital signal. The A / D converter 15 converts a voltage signal corresponding to the alternating current I _AC into a digital signal. The arithmetic processing unit 14 calculates the internal impedance R _BAT of the battery 30 from both input signals and outputs it to the display unit 6. The display unit 6 displays the value of the internal impedance R _BAT output from the arithmetic processing unit 14.

This completes the measurement of the internal impedance R _BAT of the battery 30.

  Thus, there is no capacitor in the closed loop formed by the AC source 2, the DC voltage source 3, and the battery 30, or in the closed loop formed by the battery 30, the DC voltage source 4, and the differential amplifier circuit 11. Therefore, since the saturation phenomenon of the differential amplifier circuit 11 due to the charging of the capacitor does not occur, the measurement can be performed immediately after the battery 30 is connected. Therefore, measurement can be performed in a short time.

  Next, an impedance measuring apparatus 1a according to another embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected about the structure similar to the already demonstrated structure, and detailed description is abbreviate | omitted.

In the impedance measuring device 1 of Figure 1 already described, whereas was measured between terminals AC voltage V _AC by connecting a DC voltage source 4 to the battery 30, the impedance measuring device 1a of FIG. 2, the battery 30 The resistors 25 and 26 connected in series (series resistors in the present invention) having a known resistance voltage dividing ratio are connected between the two electrodes, and the AC voltage V _AC between the two electrodes is measured from the voltage divided by the resistors 25 and 26. Is different. The point that the AC source 2 and the battery 30 are connected via the DC voltage source 3 is the same.

  Specifically, as shown in the figure, one end of the resistor 25 is connected to the positive electrode of the battery 30 by a test probe 22a, and one end of the resistor 26 is connected to the negative electrode of the battery 30 by a test probe 22b. The other ends of the resistors 25 and 26 are connected to each other, and the resistors 25 and 26 are connected in series. The other ends of the resistors 25 and 26 are connected to the inverting input terminal of the differential amplifier circuit 11. One end of the resistor 26 is connected to the non-inverting input terminal of the differential amplifier circuit 11. The differential amplifier circuit 11 differentially amplifies the voltage across the resistor 26.

Series connected resistors 25 and 26, so as not to affect the measurement of the AC current I _AC, alternating current I _AC is set to high impedance, as hardly flows. By appropriately setting the resistance values of the resistors 25 and 26, the resistance voltage dividing ratio is appropriately set. That is, the resistance voltage dividing ratio of the resistors 25 and 26 is set so that the voltage across the resistor 26 (input voltage V _IN2 ) is within the voltage range that can be differentially amplified by the differential amplifier circuit 11.

The arithmetic processing unit 14a of the measuring unit 5a can calculate the _AC voltage VAC between both electrodes of the battery 30 in consideration of the resistance voltage dividing ratio of the resistors 25 and 26 and the amplification degree of the differential amplifier circuit 11. The arithmetic processing unit 14a calculates the internal impedance R _BAT of the battery 30 from the _AC voltage V _AC between the two electrodes and the AC current I _AC .

  A measuring operation of the impedance measuring apparatus 1a will be described.

When the battery 30 is connected and the AC source 2 outputs the _AC current I _AC , the voltage V _DUT across the battery 30 is the same as that of the impedance measuring device 1.
Voltage between both ends V _DUT = DC electromotive force V _BAT + AC voltage between both ends V _AC
It becomes. Since the voltage V _DUT between both ends is resistance-divided by the resistors 25 and 26, the input voltage V _IN2 to the differential amplifier circuit 11 is obtained by multiplying the voltage V _DUT between both ends by the resistance voltage dividing ratio as follows. It can be calculated.
Input voltage V _IN2 = voltage across both ends V _DUT × R26 / (R25 + R26)
= DC electromotive force V _BAT × R26 / (R25 + R26)
+ Both ends AC voltage V _AC × R26 / (R25 + R26)
It becomes. Here, R25 is the resistance value of the resistor 25, and R26 is the resistance value of the resistor 26.

Since the voltage dividing ratio of the input voltage V _IN2 is set so as to be within the voltage range that the differential amplifier circuit 11 can input, the differential amplifier circuit 11 is not damaged and can be amplified (measured). It becomes. Accordingly, since there is no need to provide a DC blocking capacitor at the input of the differential amplifier circuit 11, a saturation phenomenon of the differential amplifier circuit 11 due to charging of the capacitor does not occur. Further, as the differential amplifier circuit 11, it is not necessary to use a differential amplifier circuit having a large maximum input voltage range, such as a differential amplifier circuit in which the power supply voltage of the circuit is higher than the DC electromotive force _VBAT .

The differential amplifier circuit 11 differentially amplifies the input voltage V _IN2 , and the BPF 12 passes only an AC component having a frequency of 1 kHz. The signal is digitally converted by the A / D converter 13 and output to the arithmetic processing unit 14a. Processing unit 14a measures the electrode-to-electrode AC voltage V _AC, and calculates the internal impedance R _BAT of the battery 30 from the AC current I _AC output from the inter-electrode AC voltage V _AC, and A / D converter 13 Display on the display unit 6.

This completes the measurement of the internal impedance R _BAT of the battery 30.

  Thus, there is no capacitor in the closed loop formed by the AC source 2, the DC voltage source 3, and the battery 30, or in the closed loop formed by the battery 30, the resistors 25 and 26, and the differential amplifier circuit 11. Therefore, since the saturation of the differential amplifier circuit 11 due to charging of the capacitor does not occur, the measurement can be performed immediately after the battery 30 is connected, so that the measurement can be performed in a short time.

  The configuration in which the BPF 12 is disposed between the differential amplifier circuit 11 and the D / A converter 13 has been described. However, the output of the differential amplifier circuit 11 is connected to the D / A converter 13 and the arithmetic processing unit 14 is connected. However, the band pass filter processing may be performed digitally.

  Further, the example in which the differential amplifier circuit 11 is used as the voltage detection circuit has been described. However, the present invention is not limited to this, and the voltage waveform of the voltage detection target is detected (input) without affecting the voltage detection target, and the waveform is directly used. Alternatively, various known circuits can be used as long as they can be amplified (including an amplification degree of 1 or less) and output. For example, as shown in FIG. 1, since the test probes 21b and 22b are grounded to the reference potential, an amplifier circuit having one input terminal capable of amplifying a voltage waveform with respect to the reference potential may be used as the voltage detection circuit. Good.

1 and 1a are impedance measuring devices, 2 is an AC source, 3 is a first DC voltage source, 4 is a second DC voltage source, 5 and 5a are measurement units, 6 is a display unit, 11 is a differential amplifier circuit, 12 is a BPF, 13 is an A / D converter, 14 and 14a are arithmetic processing units, 15 is an A / D converter, 18 is a terminal for current measurement, 21a, 21b, 22a and 22b are test probes, and 25 and 26 are Resistance, 30 is battery, 30a is internal resistance, I _AC is AC current, V _AC is AC voltage across battery 30, V _BAT is DC voltage, V _DC1 and V _DC2 are DC voltage, V _DUT is both ends of battery 30 The voltage between V _IN1 and V _IN2 is the input voltage.

Claims (5)

An impedance measuring device that supplies an alternating current from an alternating current source to a battery to be measured, and measures the internal impedance of the battery based on the supplied alternating current and the alternating voltage between both electrodes generated between both electrodes of the battery. There,
The AC source and the battery are connected via a first DC voltage source having a negative electrode connected to an output terminal of the AC source and a positive electrode connected to a positive electrode of the battery. Impedance measuring device.   The first DC voltage source is disposed inside an apparatus housing containing the AC source, or is disposed outside the apparatus housing so that a cable can be connected to the apparatus housing. Item 4. The impedance measuring apparatus according to Item 1.   A second DC voltage source having a positive electrode connected to the positive electrode of the battery; a voltage detection circuit for detecting a voltage between the negative electrode of the battery and the negative electrode of the second DC voltage source; The impedance measuring apparatus according to claim 1, wherein the AC voltage between both electrodes is measured from an AC component of an output of the circuit.   The second DC voltage source is disposed inside an apparatus housing incorporating the voltage detection circuit, or is disposed outside the apparatus housing so that a cable can be connected to the apparatus housing. The impedance measuring apparatus according to claim 3.   A series resistor connected in series with a known resistance voltage dividing ratio connected between the two electrodes of the battery; and a voltage detection circuit for detecting a voltage divided by the series resistor. The impedance measuring apparatus according to claim 1 or 2, wherein the AC voltage between both electrodes is measured from an AC component of an output.

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