JP2011053201A - Voltage detection device and line voltage detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect the voltage of a detection object without calculating the capacitance between a detecting electrode and the detection object. <P>SOLUTION: The voltage detector includes: a detecting electrode 12 arranged in opposition to a detection object 4; a detecting section 14A that is connected with the detecting electrode 12 to use the reference signal Ss as an input for outputting a detection signal S1 changing its amplitude in accordance with both current values of a detection object current Iv1 flowing according to the AC voltage V1 and a reference current Is1 flowing according to the reference signal Ss; and a signal extraction section 32 for extracting a signal component of the AC voltage V1 from an amplified detection signal S3 and outputting the signal component as an output signal So while generating the amplified detection signal S3 by amplifying an isolated detection signal S2 of a detection signal S1 at a given gain and controlling the gain so as to cancel the reference signal Ss and a signal component of the reference signal Ss included in the amplified detection signal S3 by addition or subtraction of the reference signal Sr (reference signal Ss output from a reference signal output section 31) and the amplified detection signal S3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a non-contact type voltage detection device that detects a detection target AC voltage of a detection target body in a non-contact manner, and a line voltage detection device including the voltage detection device.

  As this type of voltage detection device, a non-contact voltage measurement device (hereinafter also referred to as “voltage detection device”) disclosed in Patent Document 1 below is known. This voltage detection device includes a detection probe including a detection electrode capable of covering a part of the surface of an insulator of a wire and a shield electrode covering the detection electrode, and an oscillator that outputs a signal of a predetermined frequency. , By applying an oscillator signal to the detection electrode, measure the impedance between the detection electrode and the conductor of the wire, and detect the current flowing out of the detection electrode due to the voltage applied to the conductor (resistor It is possible to measure the voltage applied to the conductor from the current and impedance by using the value: R1).

  Specifically, in this voltage detection device, first, the detection probe is opened, and a signal from the oscillator is applied to the detection electrode via the detection resistor. Capacitance (hereinafter referred to as first capacitance for explanation) is measured. Since the first capacitance obtained by this measurement is so small that the resistance value of the detection resistor is negligible compared to the reactance of the first capacitance, the signal voltage output from the oscillator, the detection resistor , The angular frequency of the signal output from the oscillator, and the voltage across the detection resistor.

  Next, the detection probe is closed with the electric wire sandwiched, and the capacitance (hereinafter referred to as a second capacitance for explanation) in a state where the signal from the oscillator is applied to the detection electrode via the detection resistor. Take measurements. The second capacitance measured by this is a combined capacitance of the first capacitance described above and the capacitance between the detection electrode and the electric wire (hereinafter referred to as a third capacitance for explanation), and is detected. Because the resistance value of the resistor for use is negligibly small compared to the reactance for this combined capacitance, the signal voltage output from the oscillator, the resistance value of the detection resistor, the angular frequency of the signal output from the oscillator, and It is calculated from the voltage across the detection resistor. Further, the third capacitance, that is, the capacitance between the detection electrode and the conductor of the electric wire is calculated by subtracting the first capacitance from the calculated second capacitance.

  Subsequently, the detection probe is closed with the electric wire interposed therebetween, and both ends of the detection resistor caused by the voltage applied to the conductor in a state where the signal from the oscillator is applied to the detection electrode via the detection resistor. Find the voltage. The impedance of the circuit passing through the detection resistor as viewed from the conductor side is the sum of the resistance value of the detection resistor and the reactance of the third capacitance, but the resistance value of the detection resistor is the first value. The reactance for the third capacitance is smaller than the reactance for the third capacitance, which is negligible. As a result, the current flowing through the detection resistor has a value obtained by dividing the voltage applied to the conductor by this reactance, so the voltage across the detection resistor is equal to the current flowing through the detection resistor. It is a value obtained by multiplying the resistance value of. In this case, the voltage across the detection resistor includes the angular frequency of the voltage applied to the conductor, the third capacitance between the detection electrode and the wire, the voltage applied to the conductor, and the detection resistor. It is represented by each parameter of the resistance value. Therefore, in the voltage detection device, the voltage applied to the conductor includes the voltage across the detection resistor, the angular frequency of the voltage applied to the conductor, the third capacitance between the detection electrode and the electric wire, and the detection. It is calculated from the resistance value of the resistor and is displayed on the display unit.

Japanese Patent No. 3158063 (page 4-6, Fig. 3)

  However, the above voltage detection device has the following problems. That is, in this voltage detection device, the capacitance between the shield electrode and the ground (the first capacitance described above), and the capacitance between the detection electrode and the conductor of the electric wire (the third capacitance described above). (Capacitance) must be calculated individually, and there is a problem that it takes time and effort to detect the voltage applied to the conductor.

  The present invention has been made to solve the above problem, and without detecting the capacitance between the detection electrode and the detection object (conductor of the electric wire in the above example), the voltage of the detection object. It is a main object of the present invention to provide a non-contact type voltage detection device capable of detecting the above. Another main object is to provide a line voltage detecting device capable of detecting a line voltage between electric circuits.

  In order to achieve the above object, a voltage detection device according to claim 1 is a voltage detection device for detecting a detection target AC voltage generated in a detection target body, and is disposed to face the detection target body. A detection electrode that is capacitively coupled to the detection target, a reference signal output unit that outputs a reference signal, and a detection target current that is connected to the detection electrode and that receives the reference signal and flows based on the detection target AC voltage And a detection unit that outputs a detection signal whose amplitude changes according to both current values of a reference current that flows based on the reference signal, and amplifying the detection signal with a predetermined gain to generate an amplified detection signal, The reference signal and the signal component of the reference signal included in the amplified detection signal can be canceled by adding or subtracting the reference signal output from the reference signal output unit and the amplified detection signal. Controls the obtained and a signal component of the detected AC voltage and a signal extraction unit for outputting as the extraction and output signals from the amplified detection signal.

  In order to achieve the above object, the voltage detection device according to claim 2 is a voltage detection device that detects a detection target alternating voltage generated in a detection target body, and is disposed to face the detection target body. A detection electrode that is capacitively coupled to the detection object and a floating power source that is generated based on the voltage of the reference voltage unit are operated to generate an AC potential difference between the detection target AC voltage and the voltage of the reference voltage unit. A detection unit that outputs a detection signal whose amplitude changes in response, a reference signal output unit that outputs a reference signal to the reference voltage unit, and amplifying the detection signal with a predetermined gain to generate an amplified detection signal, The gain that can cancel out the reference signal and the signal component of the reference signal included in the amplified detection signal by adding or subtracting the reference signal output from the reference signal output unit and the amplified detection signal Controls, and a signal component of the detected AC voltage and a signal extraction unit for outputting as the extraction and output signals from the amplified detection signal.

  According to a third aspect of the present invention, there is provided the voltage detection device according to the first or second aspect, wherein the signal extraction unit is configured to amplify the detection signal with the gain to generate the amplified detection signal. A synchronous detection circuit for detecting a detection signal indicating an amplitude of a signal component of the reference signal included in the amplification detection signal or the output signal by synchronous detection using the reference signal output from the reference signal output unit And a control circuit for controlling the gain of the amplifier circuit based on the detection signal.

  In order to achieve the above object, the voltage detection device according to claim 4 is a voltage detection device for detecting a detection target AC voltage generated in a detection target body, and is disposed to face the detection target body. A detection electrode that is capacitively coupled to the detection object and a floating power source that is generated based on the voltage of the reference voltage unit are operated to generate an AC potential difference between the detection target AC voltage and the voltage of the reference voltage unit. A detection unit that outputs a detection signal whose amplitude changes in response, a reference signal output unit that outputs a reference signal to the reference voltage unit, and the detection signal that is input and electrically insulated and output as an insulation detection signal An amplification unit generates an amplification detection signal by amplifying the insulation detection signal with a predetermined gain, and adds or subtracts the reference signal output from the reference signal output unit and the amplification detection signal. The gain is controlled so that the reference signal and the signal component of the reference signal included in the amplified detection signal can be canceled, and the signal component of the detection target AC voltage is extracted from the amplified detection signal as an output signal. And an output signal extraction unit.

  The voltage detection device according to claim 5 is the voltage detection device according to claim 4, wherein the signal extraction unit amplifies the insulation detection signal with the gain and generates the amplified detection signal; A synchronous detection circuit for detecting a detection signal indicating an amplitude of a signal component of the reference signal included in the amplification detection signal or the output signal by synchronous detection using the reference signal output from the reference signal output unit; And a control circuit for controlling the gain of the amplifier circuit based on the detection signal.

  The voltage detection device according to claim 6 is the voltage detection device according to claim 2, 4 or 5, wherein the positive voltage and the negative voltage supplied to the reference signal output unit and the signal extraction unit are positive. A first series power supply circuit that generates a first floating voltage that is a constant positive voltage with respect to the voltage of the reference signal based on the voltage; and the first floating circuit with respect to the voltage of the reference signal based on the negative voltage. The power supply unit includes a second series power supply circuit that generates a second floating voltage that is a negative voltage whose absolute value is equal to the voltage, and the power supply unit supplies each floating voltage to the detection unit.

  The voltage detection device according to claim 7 is the voltage detection device according to claim 6, wherein the first series power supply circuit supplies a current from the first resistor connected to the positive voltage and the first resistor. And a first transistor having a collector terminal connected to the positive voltage and receiving a Zener voltage of the first Zener diode at a base terminal to generate the first floating voltage at an emitter terminal. The second series power supply circuit includes a second resistor connected to the negative voltage, a second Zener diode that operates upon receiving a current from the second resistor, and a collector terminal connected to the negative voltage. And the Zener voltage of the second Zener diode is input to the base terminal to generate the second floating voltage at the emitter terminal. And a second transistor for.

  The voltage detection device according to claim 8 is the voltage detection device according to any one of claims 1 to 6, wherein the signal extraction unit is configured to output the reference signal and the reference signal output from the reference signal output unit. An addition circuit that cancels the signal component of the reference signal by the addition and outputs the output signal, or cancels the reference signal output from the reference signal output unit and the signal component of the reference signal by the subtraction. A subtracting circuit for outputting the output signal is provided.

  The voltage detection device according to claim 9 is the voltage detection device according to any one of claims 1 to 7, wherein the signal extraction unit is configured to change an amplitude of the reference signal output from the reference signal output unit. The signal extracting unit controls the gain so that the reference signal whose amplitude has been changed by the amplitude changing unit and the signal component of the reference signal can be canceled out.

  A voltage detection device according to a tenth aspect is the voltage detection device according to any one of the first to eighth aspects, further including a processing unit that detects the detection target AC voltage based on the output signal.

  The voltage detection device according to claim 11 is the voltage detection device according to claim 9, wherein the processing unit calculates a voltage value of the detection target AC voltage based on the output signal.

  The voltage detection device according to claim 12 is the voltage detection device according to any one of claims 1 to 10, wherein the reference signal output unit includes a square wave generation circuit that generates a square wave, and the square wave. An integration circuit that integrates and outputs an integrated square wave is output, and the integrated square wave is output as the reference signal to the detection unit, and the square wave is output as the reference signal to the signal extraction unit. .

  The voltage detection device according to claim 13 is the voltage detection device according to any one of claims 1 to 10, wherein the reference signal output unit includes a pseudo noise generation circuit that generates pseudo noise, and the detection unit. The pseudo noise is output as the reference signal to the signal extraction unit.

  Further, the line voltage detection device according to claim 14 is configured such that the detection electrodes can be opposed to a plurality of corresponding electric circuits as the detection object, and an AC voltage generated in each electric circuit is detected as the detection target AC. A plurality of voltage detection devices according to any one of claims 1 to 10, each of which can be detected as a voltage, and the AC voltage of two electric circuits detected by a pair of voltage detection devices of the plurality of voltage detection devices. And a calculating unit for calculating a line voltage between the two electric circuits.

  3. The voltage detection apparatus according to claim 1, wherein the detection unit is connected to a detection electrode that is capacitively coupled to the detection target body and receives a reference signal from the reference signal output unit to detect the detection target AC voltage of the detection target body. A detection signal whose amplitude changes in accordance with both current values of the detection target current flowing based on the reference signal and the reference current flowing based on the reference signal is output, and the signal extraction unit amplifies the detection signal by a predetermined gain to detect amplification While generating the signal, the gain is controlled so that the reference signal and the signal component of the reference signal contained in the amplified detection signal can be canceled by adding or subtracting the reference signal output from the reference signal output unit and the amplified detection signal. At the same time, the signal component of the AC voltage to be detected is extracted from the amplified detection signal and output as an output signal. In this case, the current caused by the reference signal and the current caused by the detection target AC voltage flow through one current path including the coupling capacitance (capacitance) between the detection target body and the detection electrode. The detection signal is constituted by the voltage components based on it (the signal component of the reference signal and the signal component of the AC voltage to be detected).

  Therefore, according to these voltage detection devices, even when the coupling capacitance between the detection target body and the detection electrode is unknown, the sensitivity with respect to the detection target AC voltage is controlled to be constant. Therefore, since the amplitude of the signal component of the detection target AC voltage included in the output signal is controlled so as to correspond to the amplitude of the detection target AC voltage, this voltage component included in the output signal By detecting this, it is possible to detect the AC voltage to be detected in a non-contact manner without calculating the coupling capacitance.

  In the voltage detection device according to claim 3, in the signal extraction unit, the amplification circuit amplifies the detection signal with a predetermined gain to generate an amplification detection signal, and the synchronous detection circuit is included in the amplification detection signal or the output signal. A detection signal indicating the amplitude of the signal component of the reference signal is detected by synchronous detection using the reference signal, and the control circuit controls the gain of the amplifier circuit based on the detection signal. Therefore, according to this voltage detection device, since the signal component of the reference signal can be accurately detected by synchronous detection, the signal component of the reference signal included in the amplified detection signal can be canceled with high accuracy. As a result of significantly reducing the signal component of the reference signal included in the output signal, the detection accuracy of the detection target AC voltage can be further improved.

  In the voltage detection device according to claim 4, the reference signal output unit outputs a reference signal to the reference voltage unit, and the detection unit operated by the floating power source is configured to detect an alternating current between the detection target AC voltage and the voltage of the reference voltage unit. A detection signal whose amplitude changes according to the potential difference is output, the insulation unit inputs the detection signal and outputs it as an insulation detection signal, and the signal extraction unit amplifies the insulation detection signal with a predetermined gain to generate an amplified detection signal. A gain (insulation detection signal) that can cancel the reference signal and the signal component of the reference signal included in the amplification detection signal by adding or subtracting the reference signal output from the reference signal output unit and the amplification detection signal while generating The signal component resulting from the detection target AC voltage is extracted from the amplified detection signal and output as an output signal.

  Even in this case, the current caused by the reference signal and the current caused by the detection target AC voltage flow through one current path including the coupling capacitance (capacitance) between the detection target and the detection electrode. The detection signal is composed of voltage components based on the current (the signal component of the reference signal and the signal component of the AC voltage to be detected). Therefore, according to this voltage detection apparatus, the signal component of the reference signal and the reference signal included in the amplified detection signal generated from the detection signal are canceled, that is, the amplitude of the signal component of the reference signal is referred to Even if the coupling capacitance between the detection object and the detection electrode is unknown, the signal processing unit generates the amplified detection signal by controlling the gain for the insulation detection signal so as to match the amplitude of the signal. The detection target AC included in the output signal so that the sensitivity of the signal component of the detection target AC voltage included in the amplified detection signal is constant (regardless of the capacitance value of the coupling capacitor). Since the amplitude of the signal component of the voltage is controlled so as to correspond to the amplitude of the AC voltage to be detected, the detection target AC is based on the amplitude of the output signal composed of the signal component of this detection target AC voltage. It is possible to detect the pressure accurately. As a result, according to the voltage detection device, the detection target AC voltage is saved without calculating the coupling capacitance (capacitance) between the detection target body and the detection electrode (without calculating the coupling capacitance). Can be detected in a non-contact manner. In addition, according to this voltage detection device, for example, a guard electrode is used as the reference voltage unit, and thus the detection electrode, the floating power source, the detection unit, and the insulation unit are accommodated in the guard electrode and operated in a floating state. Therefore, CMRR (Common Mode Rejection Ratio) can be increased.

  In the voltage detection device according to claim 5, in the signal extraction unit, the amplification circuit amplifies the insulation detection signal with a predetermined gain to generate an amplification detection signal, and the synchronous detection circuit converts the amplification detection signal or the output signal into A detection signal indicating the amplitude of the signal component of the included reference signal is detected by synchronous detection using the reference signal, and the control circuit controls the gain of the amplifier circuit based on the detection signal. Therefore, according to this voltage detection device, since the signal component of the reference signal can be accurately detected by synchronous detection, the signal component of the reference signal included in the amplified detection signal can be canceled with high accuracy. As a result of significantly reducing the signal component of the reference signal included in the output signal, the detection accuracy of the detection target AC voltage can be further improved.

  According to the voltage detection device of the sixth aspect, the first series power supply circuit and the second series power supply circuit have the detection unit based on the positive voltage and the negative voltage supplied to the reference signal output unit and the signal extraction unit. Since the first floating voltage that is positive and the second floating voltage that is negative are generated with respect to the voltage of the reference signal used in the circuit, the use of expensive parts such as a battery and a transformer can be avoided, resulting in a product cost. Can be greatly reduced.

  According to the voltage detection device of claim 7, since the first series power supply circuit and the second series power supply circuit are respectively configured by the resistor, the Zener diode, and the transistor, each series power supply circuit can be simplified with a small number of parts. And it can be configured at low cost.

  According to the voltage detecting device of the eighth aspect, the addition circuit that outputs the output signal by canceling the signal component of the reference signal and the reference signal by addition, or the signal component of the reference signal and the reference signal by subtraction. By providing a subtracting circuit that cancels and outputs an output signal, a circuit that can be simply configured by a circuit such as an adding circuit or a subtracting circuit, cancels the signal component of the reference signal and the reference signal, and outputs the output signal. Can be output. Therefore, it is possible to reliably output an output signal while simplifying the device configuration.

  According to the voltage detection device of the ninth aspect, the amplitude detecting unit that changes the amplitude of the reference signal and outputs the changed signal to the signal extracting unit is provided, and the signal extracting unit has the signal component and the amplitude of the reference signal changed. By controlling the gain of the amplifier circuit so that the reference signal can be canceled out, it is composed of the signal component of the AC voltage to be detected when the magnification of the reference signal amplitude after the change relative to the amplitude of the reference signal before the change is k. The detection target AC voltage can be detected by multiplying the amplitude of the output signal by 1 / k. Therefore, the detection range of the detection target AC voltage can be expanded by changing the magnification k.

  In addition, according to the voltage detection device of the tenth aspect, by including the processing unit that detects the detection target AC voltage based on the output signal, for example, the detection target AC voltage is detected at regular intervals with respect to the processing unit. In addition, the detected AC voltage to be detected can be displayed as a waveform on a display device or the like, and convenience can be improved.

  According to the voltage detection device of the eleventh aspect, since the processing unit calculates the voltage value of the detection target AC voltage based on the output signal, the detection target AC voltage can be accurately detected (measured).

  According to the voltage detection device of the twelfth aspect, the reference signal output unit includes a square wave generation circuit that generates a square wave, and an integration circuit that integrates the square wave and outputs an integral square wave. In contrast, by outputting this integrated square wave as a reference signal, the square wave generation circuit can be simply configured using a logic circuit, etc., thereby simplifying the overall configuration of the reference signal output unit. The reference current that flows based on the signal can be the same square wave that is output from the reference signal output unit to the signal extraction unit. Thus, while simplifying the device configuration (specifically, the entire configuration of the reference signal output unit), the signal extraction unit ensures the reference signal and the signal component of the reference signal included in the amplified detection signal. The signal component of the detection target AC voltage can be reliably extracted from the amplified detection signal and output as an output signal.

  According to the voltage detection device of the thirteenth aspect, the reference signal output unit includes a pseudo noise generation circuit that generates pseudo noise, and outputs the pseudo noise as a reference signal to the detection unit and the signal extraction unit. Thus, it is possible to make it less susceptible to disturbance (noise).

  Further, according to the line voltage detection device of the fourteenth aspect, since the voltage detection device is used, the coupling capacitance between the electric circuit as the detection object and the detection electrode corresponding to the electric circuit is unknown. Even in this case, it is possible to accurately detect the line voltage between the lines without calculating the coupling capacitance (capacitance) between the electric circuit and the detection electrode.

1 is a configuration diagram of a voltage detection device 1. FIG. It is a circuit diagram of the floating circuit part 2 in FIG. It is a circuit diagram of the amplifier circuit 41 in FIG. It is a block diagram of voltage detection apparatus 1A. It is a circuit diagram of the detection part 14A in FIG. It is a block diagram of 31 A of other reference signal output parts. It is a block diagram of the other reference signal output part 31B. It is a block diagram of the line voltage detection apparatus 51 which uses the voltage detection apparatus 1. FIG. It is a block diagram of the line voltage detection apparatus 51A using the voltage detection apparatus 1A. It is a block diagram of the floating circuit part 2 in the voltage detection apparatus 1 (1A) provided with the other power supply part 13A. It is a circuit diagram of other power supplies 13A. 3 is a circuit diagram of a floating circuit unit 2 and a differential amplifier circuit 63 that are configured not to use an insulating unit 15. FIG.

  Hereinafter, embodiments of a voltage detection device and a line voltage detection device will be described with reference to the accompanying drawings.

  First, the voltage detection apparatus 1 will be described with reference to the drawings.

  The voltage detection device 1 is a non-contact type voltage detection device and includes a floating circuit portion 2 and a main body circuit portion 3 as shown in FIG. 1 and is generated in the detection target body 4 with the ground potential Vg as a reference. The AC voltage V <b> 1 (AC voltage to be detected) can be detected without contact.

  As shown in FIG. 1, the floating circuit unit 2 includes a guard electrode 11, a detection electrode 12, a power supply unit 13, a detection unit 14, and an insulating unit 15. The guard electrode 11 is configured as a reference voltage unit in the floating circuit unit 2 using a conductive material (for example, a metal material), and the detection electrode 12, the detection unit 14, and the insulating unit 15 are accommodated therein. As will be described later, the insulating unit 15 has a function of outputting a signal input from the primary side circuit in a state of being electrically insulated from the secondary side circuit from the primary side circuit. The part to be covered with the electrode 11 may be at least the primary side circuit, but the secondary side circuit may be covered with the guard electrode 11 as well. In this example, as an example, an opening (hole) 11 a is formed in the guard electrode 11. The detection electrode 12 is formed in a flat plate shape as an example, and is disposed in a non-contact state with the guard electrode 11 at a position facing the opening 11 a in the guard electrode 11. Further, when detecting the AC voltage V1, the detection electrode 12 is capacitively coupled (coupled via the capacitance C0) to the detection object 4 as shown in FIG.

  The power supply unit 13 is configured as a floating power supply that generates various floating voltages using the voltage Vr of the guard electrode 11 as a reference (zero volts). Further, the power supply unit 13 supplies the generated floating voltage as an operating voltage to each component arranged in the guard electrode 11. In this example, as an example, the power supply unit 13 is configured to include a battery and a DC / DC converter (both not shown), and the DC / DC converter performs various operations based on the DC voltage output from the battery. Floating voltage (for example, when the voltage Vr is set to zero volts, the first floating voltage Vf + that is positive with respect to the voltage Vr, and the first voltage that is negative with the absolute value equal to the first floating voltage Vf + with respect to the voltage Vr. 2 Floating voltage Vf− (hereinafter, also simply referred to as floating voltage Vf + and floating voltage Vf−) is generated as an operating voltage. Although not shown, instead of the battery, an AC voltage is supplied into the guard electrode 11 while being electrically insulated from the outside of the guard electrode 11 via a transformer, and this AC voltage is supplied to the guard electrode 11. It is also possible to adopt a configuration in which the rectifying / smoothing unit provided is converted to a DC voltage and supplied to the DC / DC converter.

  The detection unit 14 is connected to the detection electrode 12 and receives the reference signal Ss from the reference signal output unit 31 (the reference signal Ss is applied), and the detection target current (AC voltage) that flows based on the AC voltage V1. The detection signal S1 whose amplitude changes according to both current values of the current signal component (Iv1 caused by V1) and the reference current (current signal component caused by the reference signal Ss) Is1 flowing based on the reference signal Ss is output. Specifically, the detection unit 14 operates by receiving supply of a floating voltage Vf + that is a positive voltage and a floating voltage Vf− that is a negative voltage with respect to the voltage Vr of the guard electrode 11, and the AC voltage V1 and the guard electrode 11 is detected based on a current signal I (detection current) flowing at a current value corresponding to an AC potential difference (V1−Vr) with respect to the 11 voltage Vr, with the amplitude changing according to the AC potential difference (V1−Vr). A signal S1 is generated and output. In this case, a reference signal Ss is output (applied) to the guard electrode 11 from a reference signal output unit 31 described later. With this configuration, the voltage Vr matches the voltage Vs of the reference signal Ss. As a result, the current signal I includes the reference current Is1 caused by the reference signal Ss and the detection target current Iv1 caused by the AC voltage V1, and the detection signal S1 based on the current signal I is also the reference current Is1. Voltage signal component (hereinafter referred to as “reference voltage component”) Vs1 and voltage signal component based on detection target current Iv1 (hereinafter referred to as “detection target voltage component”) Vv1. Further, since the detection unit 14 operates based on the voltage of the guard electrode 11 that varies with the voltage Vs of the reference signal Ss to generate the detection signal S1, the reference voltage component Vs1 included in the detection signal S1 is the voltage of the reference signal Ss. The signal is in reverse phase with respect to Vs.

  In this example, as an example, the detection unit 14 includes an integration circuit 21 and an amplification circuit 22 as shown in FIG. The integrating circuit 21 has an operational amplifier 21a having a non-inverting input terminal connected to the guard electrode 11 and an inverting input terminal connected to the detection electrode 12, and a capacitor connected between the inverting input terminal and the output terminal of the operational amplifier 21a. 21b and a resistor 21c connected in parallel to the capacitor 21b. In this case, the capacitor 21b is constituted by a capacitor of about 0.01 μF, for example, and the resistor 21c is constituted by a resistor having a high resistance value of about 1 MΩ, for example. For this reason, in the integrating circuit 21, the current signal I mainly flows through the capacitor 21 b, whereby the integrating operation is performed simultaneously with the current-voltage conversion operation, and the AC voltage V 1 of the detection target body 4 and the voltage Vr of the guard electrode 11 are A voltage signal S0 whose voltage value changes in proportion to the AC potential difference (V1-Vr) is generated. In the integrating circuit 21, the feedback amount in the vicinity of DC is remarkably reduced only by the capacitor 21b, the gain becomes extremely large, and the operational amplifier 21a may be saturated by the offset due to the bias current. In order to suppress the decrease in the resistance 21c, a resistor 21c is provided. The amplifier circuit 22 amplifies the voltage signal S0 with a predetermined amplification factor and outputs it as a detection signal S1. Although not shown, the integration circuit 21 is configured by two circuits, for example, a current-voltage conversion circuit that converts the current signal I into a voltage signal, and an integration circuit that integrates the voltage signal and outputs it as a detection signal S1. You can also

  The insulating unit 15 receives the detection signal S1 and electrically insulates it and outputs it as an insulation detection signal S2. Specifically, the insulating unit 15 is configured using an optical isolation element (in this example, a photocoupler as an example) as an example, and a detection signal input to a light emitting diode (not shown) as a primary side circuit thereof. S1 is output as an insulation detection signal S2 from the phototransistor as the secondary side circuit. That is, the insulating unit 15 outputs a signal having the same phase as the detection signal S1 and having an amplitude that is proportional to the amplitude of the detection signal S1, as the insulation detection signal S2. Instead of the photocoupler, the insulating unit 15 can be configured using an optical MOS-FET in which the primary side circuit is configured by a light emitting diode and the secondary side circuit is configured by an FET pair. In this case, in the insulating unit 15, the primary side circuit operates by receiving supply of the floating voltages Vf + and Vf−. In addition, when the detection signal S1 is an alternating current with a high frequency, the insulating unit 15 can be configured using a transformer.

  As shown in FIG. 1, the main body circuit unit 3 includes a reference signal output unit 31, a signal extraction unit 32, a processing unit 33, a storage unit 34, and an output unit 35. In this case, the reference signal output unit 31 generates a reference signal Ss having a constant amplitude (an AC signal having a constant frequency and amplitude. For example, a sine wave signal) in which the voltage Vs changes in a predetermined cycle with the ground potential Vg as a reference. And output to the guard electrode 11. As a result, the voltage Vr of the guard electrode 11 is regulated to the voltage Vs of the reference signal Ss. That is, the voltage Vr of the guard electrode 11 changes at a predetermined cycle in a state where the voltage Vr matches the voltage Vs of the reference signal Ss. In this example, the reference signal output unit 31 directly outputs the reference signal Ss to the guard electrode 11. However, since the reference signal Ss is an AC signal, the reference signal output unit 31 is not shown in the figure. The reference signal Ss may be output to the guard electrode 11 through a capacitor. The reference signal output unit 31 also outputs the reference signal Ss to the signal extraction unit 32. In addition, the amplitude change part 36 shown with the broken line in the figure is not contained in the main body circuit part 3 in this example. For this reason, the reference signal Ss output from the reference signal output unit 31 is directly input to the signal extraction unit 32. Further, in this example, as an example, the reference signal Ss is defined to have a frequency that is higher than the frequency of the AC voltage V <b> 1 of the detection object 4. In this case, the frequency of the reference signal Ss can be defined to be lower than the frequency of the AC voltage V1 of the detection target body 4.

  For example, the signal extraction unit 32 includes an amplifier circuit 41, an adder circuit 42, a synchronous detection circuit 43, and a control circuit 44. The signal extraction unit 32 amplifies the insulation detection signal S2 with a predetermined gain to generate an amplification detection signal S3, and performs amplification detection. When the insulation detection signal S2 is amplified so that the signal component of the reference signal Ss and the reference signal Ss included in the signal S3 can be canceled by addition or subtraction (addition in this example) of the amplification detection signal S3 and the reference signal Ss. And the signal component of the AC voltage V1 is extracted (generated) from the amplified detection signal S3 and output as the output signal So. In this case, the signal component of the reference signal Ss included in the amplified detection signal S3 is caused by the reference voltage component Vs1 included in the detection signal S1 based on the output (application) of the reference signal Ss to the guard electrode 11. This is a signal component (that is, a signal component having the same frequency as that of the reference signal Ss included in the amplified detection signal S3).

  Specifically, the amplification circuit 41 receives the insulation detection signal S2 and also has an amplification factor defined by the level (DC voltage level) of the control signal (specifically, control voltage) Sc output from the control circuit 44. The insulation detection signal S2 is amplified with a gain of 1 or more (less than 1), and an amplified detection signal S3 is generated and output. As an example, as shown in FIG. 3, the amplifier circuit 41 includes an operational amplifier 41a, a variable resistance element disposed between the inverting input terminal of the operational amplifier 41a and the ground potential (in this example, J− An FET (Junction Field Effect Transistor) 41b and a resistor 41c disposed between the inverting input terminal and the output terminal of the operational amplifier 41a are configured as a non-inverting amplifier circuit as a whole. It is configured as. In this case, the resistance value of the variable resistance element 41b changes according to the level of the input control signal Sc. Therefore, the amplifier circuit 41 changes the amplification factor according to the level of the input control signal Sc, and amplifies the insulation detection signal S2 with this amplification factor and outputs the amplified detection signal S3. The variable resistance element only needs to be an element whose resistance value changes according to an externally input voltage, and can be configured using an element or circuit other than the J-FET. In this example, as an example, the variable resistance element 41b is configured such that its resistance value decreases when the level of the input control signal Sc increases, and its resistance value increases when the level of the control signal Sc decreases. Has been. With this configuration, the amplification factor of the amplifier circuit 41 increases when the level of the control signal Sc increases, and decreases when the level of the control signal Sc decreases.

  The adder circuit 42 inputs the voltage Vr generated at the guard electrode 11 as the reference signal Sr (in this example, since only the reference signal Ss is applied to the guard electrode 11, the reference signal Sr becomes the reference signal Ss). At the same time, the amplified detection signal S3 is input, both the signals S3 and Sr are added, and an addition signal obtained by the addition is output as the output signal So. In this case, as described above, the detection signal S1 includes the reference voltage component Vs1 having a phase opposite to that of the reference signal Ss and the detection target voltage component Vv1 having the same phase as the AC voltage V1. For this reason, the insulation detection signal S2 generated based on the detection signal S1 and the amplified detection signal S3 generated by amplifying the insulation detection signal S2 are also a signal component having an opposite phase to the reference signal Ss, and an AC voltage. It is composed of signal components in phase with V1. Therefore, the adder circuit 42 performs an addition process of both signals S3 and Sr, thereby obtaining a signal component having an antiphase with respect to the reference signal Ss constituting the amplification detection signal S3 (hereinafter also referred to as “an antiphase signal component”). A process of canceling (cancelling) with the reference signal Sr (reference signal Ss in this example) is executed. That is, the addition circuit 42 functions as a cancellation circuit. In this case, the signal component having the same frequency as that of the reference signal Ss included in the output signal So is completely canceled when the amplitude of the antiphase signal component constituting the amplification detection signal S3 is the same as the amplitude of the reference signal Sr ( It is canceled out). On the other hand, the signal component having the same frequency as that of the reference signal Ss remains in the output signal So when the amplitude of the antiphase signal component constituting the amplification detection signal S3 is different from the amplitude of the reference signal Sr, and the amplification detection signal S3. When the amplitude of the anti-phase signal component constituting the reference signal Sr is larger than the amplitude of the reference signal Sr, the phase becomes opposite to that of the reference signal Ss. It has the same phase as the signal Ss.

  The synchronous detection circuit 43 receives the output signal So and the reference signal Ss, and generates and outputs a detection signal Vd by synchronously detecting the output signal So with the reference signal Ss. Specifically, the synchronous detection circuit 43 responds to the increase or decrease of the amplitude of the signal component of the reference signal Ss included in the output signal So (specifically, the signal component having the same frequency as the reference signal Ss) by synchronous detection. When the absolute value of the voltage increases and decreases, and the phase of the signal component of the reference signal Ss included in the output signal So coincides with the phase of the reference signal Ss (when it is the same phase), and when it is shifted by 180 ° (inversely) A detection signal Vd having a different polarity in phase) is generated and output. In this example, as an example, the synchronous detection circuit 43 has a positive polarity (positive voltage) when a predetermined signal component included in the output signal So and the reference signal Ss are in phase, and a negative polarity ( A detection signal Vd having a negative voltage is generated and output.

  The control circuit 44 generates a control signal Sc whose voltage increases or decreases based on the polarity of the input detection signal Vd, and outputs the control signal Sc to the amplifier circuit 41. In this example, as an example, the control circuit 44 increases the voltage level of the control signal Sc when the input detection signal Vd is positive, while the control signal Sc of the control signal Sc when the input detection signal Vd is negative. Reduce the voltage level. With the above configuration, in the signal extraction unit 32, feedback control on the gain (amplification factor) of the amplifier circuit 41 is performed by the synchronous detection circuit 43 and the control circuit 44, and the control circuit 44 is the inverse of the amplification detection signal S3. The amplitude of the phase signal component (the signal component having the same frequency as the reference signal Ss) is constant (in this example, the amplitude is the same as the amplitude of the reference signal Ss input as the reference signal Sr to the adder circuit 42). The amplification factor of the amplifier circuit 41 is controlled based on the detection signal Vd. Thereby, the amplitude of the anti-phase signal component constituting the amplification detection signal S3 is made to coincide with the amplitude of the reference signal Sr (reference signal Ss in this example) input to the adder circuit. Therefore, the addition circuit 42 executes the addition process of the amplified detection signal S3 and the reference signal Sr, cancels (cancels) the reverse phase signal component constituting the amplified detection signal S3 with the reference signal Ss, and detects the detection object 4 An output signal So composed of a voltage component (a signal component having the same frequency as the AC voltage V1) based on the detection target current Iv1 caused by the AC voltage V1 is generated and output.

  In this case, the reference current Is1 and the detection target current Iv1 included in the current signal I fluctuate at the same rate according to the magnitude of the capacitance C0 formed between the detection target body 4 and the detection electrode 12. The reference voltage component Vs1 and the detection target voltage component Vv1 included in the detection signal S1 also vary at the same rate. Therefore, both of the anti-phase signal component (the signal component having the same frequency as that of the reference signal Ss) and the signal component having the same frequency as that of the AC voltage V1 constituting the amplification detection signal S3 vary at the same rate, but the signal extraction unit. In 32, the amplitude of the anti-phase signal component (the signal component having the same frequency as that of the reference signal Ss) constituting the signal S3 is the reference signal Sr (reference signal Ss in this example) by the feedback control described above. Is generated by the amplifying circuit 41 so as to coincide with the amplitude of. For this reason, in the voltage detection device 1 having the configuration of this example, the voltage component based on the detection target current Iv1 included in the output signal So has an amplitude of the detection target 4 regardless of the magnitude of the capacitance C0. Theoretically, the amplitude corresponds to the amplitude of the AC voltage V1 generated at the same time, and the amplitude thereof coincides with the amplitude of the AC voltage V1 generated at the detection object 4.

  The processing unit 33 includes an A / D converter and a CPU (both not shown), samples the voltage waveform (level) of the output signal So with a sampling clock having a predetermined frequency, and converts it into digital data D1. Then, a storage process to be stored in the storage unit 34, a voltage calculation process for calculating the AC voltage V1 based on the digital data D1, and an output process for outputting the calculated AC voltage V1 are executed. The storage unit 34 includes a ROM, a RAM, and the like, and stores a voltage calculation table TB used in the voltage calculation process in the processing unit 33 in advance. An outline of the procedure for creating the voltage calculation table TB will be described. As an example, in a state where a reference signal Ss of a known voltage Vs (constant) is output to the guard electrode 11 and feedback control is performed by the synchronous detection circuit 43 and the control circuit 44, the AC voltage V1 generated in the detection target 4 The digital data D1 is acquired while changing the amplitude of the AC voltage at a predetermined voltage step, and the digital data D1 is stored together with the voltage value of the AC voltage V1 in association with the AC voltage V1 changed at the voltage step. A calculation table TB is created. With this configuration, the processing unit 33 calculates the AC voltage V1 of the detection target body 4 by acquiring the voltage value of the AC voltage V1 corresponding to the acquired digital data D1 with reference to the voltage calculation table TB. Is possible. In this example, the output unit 35 is configured by a display device as an example, and displays the waveform of the AC voltage V1 and the calculated voltage parameter (amplitude and effective value) in the output process of the processing unit 33.

  Next, the detection operation for the AC voltage V1 of the detection object 4 by the voltage detection device 1 will be described.

  First, the floating circuit unit 2 (or the entire voltage detection device 1) is positioned in the vicinity of the detection target body 4 so that the detection electrode 12 faces the detection target body 4 in a non-contact state. Thereby, as shown in FIG. 1, the capacitance C0 is formed between the detection electrode 12 and the detection target body 4. In this case, the capacitance value of the capacitance C0 changes in inverse proportion to the distance between the detection electrode 12 and the detection object 4. However, once the floating circuit unit 2 is disposed, the environment such as temperature is constant. Below it is a constant (non-fluctuating) value. Further, since the capacitance value of the capacitance C0 is generally extremely small (for example, about several pF to several tens pF), even if the frequency of the AC voltage V1 is about several hundred Hz, the detection object 4 and the detection electrode The impedance between 12 becomes a sufficiently large value (several MΩ). For this reason, in this voltage detection apparatus 1, even when the AC voltage V1 of the detection object 4 and the voltage Vr of the guard electrode 11 are significantly different (when the potential difference Vdi is large), the operational amplifier 21a that constitutes the detection unit 14 An inexpensive product with a low input withstand voltage can be used, and even in this configuration, destruction of the operational amplifier 21a due to the potential difference Vdi is avoided.

  In addition, the detection electrode 12 and the detection target body 4 are connected in an AC manner via the capacitance C0, so that the detection target body 4, the detection electrode 12, the detection unit 14, the guard electrode 11 and the ground potential Vg A current path A (path indicated by a one-dot chain line in FIG. 1) reaching the ground potential Vg through the reference signal output unit 31 is formed. Therefore, a current signal I composed of a reference current Is1 caused by the voltage Vs of the reference signal Ss and a detection target current Iv1 caused by the AC voltage V1 of the detection target body 4 flows through the current path A. Yes.

  Thereby, in the floating circuit unit 2, as shown in FIGS. 1 and 2, the integrating circuit 21 of the detecting unit 14 integrates the current signal I to generate the voltage signal S0, and the amplifying circuit 22 amplifies the voltage signal S0. And output as a detection signal S1. The insulating unit 15 receives the detection signal S1 and outputs it as an insulation detection signal S2 that is electrically insulated from the detection signal S1.

  In the signal extraction unit 32 of the main body circuit unit 3, as shown in FIG. 1, the amplification circuit 41 receives the insulation detection signal S <b> 2 and is specified by the voltage level of the control signal Sc output from the control circuit 44. The insulation detection signal S2 is amplified with the amplification factor to be output as an amplification detection signal S3. Next, the adder circuit 42 receives the amplification detection signal S3 and the reference signal Sr, executes addition processing for adding both signals S3 and Sr to each other, and outputs the result as an output signal So. In this case, as described above, feedback control on the gain (amplification factor) of the amplifier circuit 41 is performed by the synchronous detection circuit 43 and the control circuit 44, and the anti-phase signal component constituting the amplification detection signal S3 from the amplifier circuit 41 is obtained. The amplitude of (a signal component having the same frequency as the reference signal Ss) is made to coincide with the amplitude of the reference signal Sr (reference signal Ss in this example). For this reason, the addition processing in the addition circuit 42 cancels (cancels) the reverse phase signal component constituting the amplification detection signal S3 with the reference signal Sr, that is, removes the reverse phase signal component constituting the amplification detection signal S3. Thus, an output signal So composed of a voltage component (a signal component having the same frequency as the AC voltage V1) based on the detection target current Iv1 caused by the AC voltage V1 of the detection target body 4 is output.

  Next, the processing unit 33 executes a storage process, inputs the output signal So, converts it into digital data D1, and stores it in the storage unit 34. Subsequently, the processing unit 33 executes a voltage calculation process. In this voltage calculation process, the processing unit 33 reads the digital data D1 stored in the storage unit 34 and refers to the voltage calculation table TB to acquire the AC voltage V1 corresponding to the read digital data D1. . Further, the processing unit 33 calculates, for example, an effective value or amplitude of the AC voltage V1 based on the acquired AC voltage V1, and stores it in the storage unit 34. Finally, the processing unit 33 executes output processing, and displays the effective value, amplitude, and the like of the AC voltage V1 stored in the storage unit 34 on the output unit 35 configured by a display device. Thereby, the detection of the alternating voltage V1 of the detection target body 4 by the voltage detection apparatus 1 is completed. In the output process, a configuration in which the processing unit 33 displays the voltage waveform of the AC voltage V1 on the output unit 35 based on the acquired AC voltage V1 may be employed.

  In this voltage detection device 1, the reference signal output unit 31 outputs the reference signal Ss to the guard electrode 11, and the detection unit 14 that operates by receiving the supply of the floating voltages Vf + and Vf− is detected via the detection electrode 12. Based on the current signal I flowing between the body 4 and the guard electrode 11 at a current value corresponding to the AC potential difference (V1−Vr) between the AC voltage V1 and the voltage Vr of the guard electrode 11, an AC potential difference ( V1-Vr) outputs a detection signal S1 whose amplitude changes according to V1-Vr), the insulation unit 15 inputs the detection signal S1 and outputs it as an insulation detection signal S2, and the signal extraction unit 32 is included in the insulation detection signal S2 The amplitude of the same signal component as the reference signal Ss is predetermined amplitude (the same signal component as the reference signal Ss included in the amplified detection signal S3 can be canceled by addition or subtraction with the reference signal Ss) Width), that is, the amplitude of the insulation detection signal S2 is controlled so as to be constant and output as the amplification detection signal S3, and the amplification detection signal S3 and the reference signal output unit 31 thus controlled in amplitude. The signal component same as the reference signal Ss included in the amplified detection signal S3 is removed by addition or subtraction with the reference signal Ss output from the signal, and output as the output signal So, and the processing unit 33 detects the detection target current Iv1 ( The AC voltage V1 is calculated based on the level of the output signal So composed of voltage components generated based on the AC component V1 generated due to the AC voltage V1 of the detection object 4.

  Therefore, according to the voltage detection apparatus 1, the signal extraction unit 32 controls the amplitude of the amplified detection signal S3 so that the amplitude of the signal component having the same frequency as that of the reference signal Ss is constant, and the amplified detection signal S3 and the reference are referred to. By removing or adding the same signal component as the reference signal Ss included in the amplified detection signal S3 by addition or subtraction with the signal Ss and outputting it as the output signal So, the detection object 4 and the detection electrode 12 are Even when the coupling capacitance (capacitance C0) is unknown (regardless of the value of the capacitance C0), the sensitivity with respect to the AC voltage V1 is controlled to be a constant sensitivity, that is, the output Since the amplitude of the voltage component based on the detection target current Iv1 included in the signal So is controlled so as to correspond to the amplitude of the AC voltage V1, this voltage component included in the output signal So. By detecting, without performing calculation of the electrostatic capacitance C0, it is possible to detect the AC voltage V1 in a non-contact manner.

  In this voltage detection apparatus 1, in the signal extraction unit 32, the synchronous detection circuit 43 refers to the detection signal Vd indicating the amplitude of the signal component for the reference signal Ss included in the amplification detection signal S3 or the output signal So. The detection is performed by synchronous detection using the signal Ss, and the control circuit 44 controls the gain of the amplifier circuit 41 based on the detection signal Vd. Therefore, according to the voltage detection device 1, the signal component of the reference signal Ss can be accurately detected by synchronous detection. As a result, the signal component of the reference signal Ss included in the amplified detection signal S3 can be detected with high accuracy. Since the signal component of the reference signal Ss included in the output signal So can be greatly reduced, the detection accuracy of the AC voltage V1 can be further improved.

  Further, in this voltage detection device 1, a process of canceling (cancelling) a signal component (anti-phase signal component) having an antiphase with respect to the reference signal Ss constituting the amplification detection signal S3 with the reference signal Sr (reference signal Ss in this example). The signal extraction unit 32 is configured by including an addition circuit 42 that executes the above as a cancellation circuit, and the control circuit 44 includes a negative-phase signal component (of the reference signal Ss) included in the amplification detection signal S3 input to the addition circuit 42. The gain of the amplifier circuit 41 is controlled so that the signal component) can be canceled by the reference signal Sr. Therefore, according to the voltage detection device 1, since the cancellation circuit can be configured with a simple circuit such as an addition circuit, the output signal So can be reliably generated while simplifying the device configuration. .

  Moreover, according to this voltage detection apparatus 1, by providing the processing unit 33 that detects the AC voltage V1 based on the output signal So, the processing unit 33 can detect the AC voltage V1 at regular intervals, Further, the detected AC voltage V1 can be stored and stored in the storage unit 34, or the voltage waveform of the AC voltage V1 can be displayed on the output unit 35 based on the AC voltage V1 stored in the storage unit 34. .

  Moreover, according to this voltage detection apparatus 1, since the process part 33 calculates the voltage value of the alternating voltage V1 based on the output signal So, the alternating voltage V1 can be detected (measured).

  Note that the voltage detection device 1 described above utilizes the fact that the signal component of the reference signal Ss included in the amplification detection signal S3 is in reverse phase with respect to the reference signal Sr (reference signal Ss in this example). Thus, the adder circuit 42 is used as a canceling circuit to cancel the signal component of the reference signal Ss and the reference signal Ss included in the amplified detection signal S3. However, the detection unit 14, the insulating unit 15, and the amplification circuit In 41, it is also possible to invert the phases of the detection signal S1, the insulation detection signal S2, and the amplified detection signal S3, or to invert the reference signal Sr to the cancellation circuit and output it. In this configuration, the signal component of the reference signal Ss included in the amplification detection signal S3 and the reference signal Ss can be in phase, and in this case, a subtraction circuit is used as the cancellation circuit. The signal component of the reference signal Ss included in the amplification detection signal S3 and the reference signal Ss can be canceled out.

  In the above example, a configuration is adopted in which the reference signal Ss is directly input as the reference signal Sr to the cancellation circuit (in the above example, the addition circuit 42). However, as shown by a broken line in FIG. 31 and an adder circuit 42, an amplitude changing unit 36 is provided, and the amplitude of the reference signal Ss output from the reference signal output unit 31 is multiplied by k (k is a positive real number) in the amplitude changing unit 36. It is also possible to adopt a configuration in which it is changed and output to the adder circuit 42 as the reference signal Sr1. The amplitude changing unit 36 can be simply configured with an attenuator configured with, for example, a voltage dividing resistor. In addition, the amplitude changing unit 36 may be configured by an amplifier that amplifies a signal with a predetermined gain (k times), so that the amplitude of the reference signal Sr1 can be increased more than the amplitude of the voltage signal Sr. In these configurations, the signal extraction unit 32 matches the amplitude of the signal component of the reference signal Ss included in the amplified detection signal S3 with the amplitude of the reference signal Ss multiplied by k (the amplitude of the reference signal Sr1). Feedback control is performed. In this case, in a state where the signal component of the reference signal Ss included in the amplification detection signal S3 and the reference signal Sr1 multiplied by k are canceled by the adder circuit 42, the AC voltage V1 included in the output signal So is obtained. The amplitude of the voltage component based on the detected current to be detected Iv1 is also detected in a state multiplied by k. For this reason, the AC voltage V1 can be detected by multiplying the voltage component based on the detected current to be detected Iv1 by 1 / k.

  Therefore, according to this configuration, the range of the AC voltage V1 that can be detected (measured) can be expanded by changing the magnification k in the amplitude changing unit 36. For example, when the input level of the output signal So in the processing unit 33 is stipulated (in the configuration including the A / D converter as described above, the input level of the output signal So depends on the input rating of the A / D converter. Even if the magnification k is a numerical value 1/10, it is defined in comparison with the case where the numerical value 1 is set to 1 (a configuration in which the reference signal Ss is directly input to the adding circuit 42 as the reference signal Sr). While satisfying the input level of the output signal So, even higher AC voltage V1 can be detected (measured).

  In the voltage detection device 1 described above, the detection electrode 12, the power supply unit 13, the detection unit 14, and the insulating unit 15 are accommodated in the guard electrode 11, so that the floating circuit unit 2 is separated from the main body circuit unit 3. In order to increase the CMRR (Common Mode Rejection Ratio) and to detect the high-voltage AC voltage V1, the detection unit 14 is not required to be operated in a floating state (for example, In the case where the AC voltage V1 is relatively low or a high CMRR is not required), a configuration in which the guard electrode 11, the power supply unit 13, and the insulating unit 15 are not used as in the voltage detection device 1A shown in FIG. It can also be adopted. Hereinafter, the voltage detection apparatus 1A will be described.

  As illustrated in FIG. 4, the voltage detection device 1 </ b> A includes a detection electrode 12 and a detection unit 14 </ b> A instead of the floating circuit unit 2 of the voltage detection device 1. Therefore, the voltage detection device 1A includes the detection electrode 12, the detection unit 14A, and the main body circuit unit 3, and is configured to be able to detect the AC voltage V1 generated in the detection target body 4 without contact. Since the detection electrode 12 and the main body circuit unit 3 are configured in the same manner as the voltage detection device 1, the same reference numerals are assigned and the redundant description is omitted, and the detection unit 14 </ b> A that is different from the voltage detection device 1 is omitted. Will be mainly described.

  The detection unit 14A generates an operating voltage (based on the ground potential Vg) from a power source (not shown) that is the same as each component (the reference signal output unit 31, the signal extraction unit 32, the processing unit 33, and the like) constituting the main body circuit unit 3. Are supplied with a positive voltage Vcc + and a negative voltage Vcc−). Further, as shown in FIG. 4, the detection unit 14A is connected to the detection electrode 12 and receives the reference signal Ss (the reference signal Ss is applied), and the detection electrode is caused by the presence of the AC voltage V1. 12 and a detection current Iv1 that flows between the detection target body 4 and a reference current Is1 that flows between the detection electrode 12 and the detection target body 4 due to the input of the voltage Vs of the reference signal Ss. A signal I (= Iv1 + Is1) is detected, and a detection signal S1 whose amplitude changes according to the current value of the current signal I is output. Note that the amplitude of the current signal I changes according to the AC potential difference (V1−Vr) between the AC voltage V1 and the voltage Vr (= voltage Vs) of the guard electrode 11, that is, the potential difference (V1−V1). It can be said that the current signal flows at a current value corresponding to Vr).

In this example, the detection unit 14A includes a detection resistor 61 and a differential amplification unit 62 as illustrated in FIG. The detection resistor 61 has one end connected to the detection electrode 12 and the other end connected to the reference signal output unit 31. The differential amplifying unit 62 includes a known instrumentation amplifier including three operational amplifiers AP1 to AP3 and seven resistors R1 to R7. In the differential amplifier 62, capacitors C1 and C2 are connected in parallel to the resistors R6 and R7, respectively, and the output stage including the operational amplifier AP3 has an integration function. In the differential amplifying unit 62, the resistors at symmetrical positions among the resistors R1 to R7 are balanced (that is, R2 and R3, R4 and R5, and R6 and R7 are respectively It is assumed that capacitors C1 and C2 are balanced (C1 and C2 are defined to have the same capacitance value). In the differential amplifier 62, the non-inverting input terminal of the operational amplifier AP1 that functions as one input terminal in the differential amplifier 62 is connected to one end of the detection resistor 61, and the other one in the differential amplifier 62 is connected. A non-inverting input terminal of the operational amplifier AP2 functioning as an input terminal is connected to the reference signal output unit 31. In the differential amplifier 62, when the voltages input to the input terminals are Vin1 and Vin2, the detection signal S1 is expressed by the following equation.
S1 = (Vin2-Vin1) × (1 + 2 × R2 / R1) × R6 / R4
In this case, (Vin2−Vin1) in the equation of S1 represents a voltage generated between both ends of the detection resistor 61 when the current signal I (= Iv1 + Is1) flows. Therefore, as described above, the detection unit 14A outputs the detection signal S1 whose amplitude changes according to the current value of the current signal I (= Iv1 + Is1).

  In the main body circuit unit 3, the signal extraction unit 32 amplifies the detection signal S1 with a predetermined gain to generate an amplification detection signal S3, and amplifies and detects the signal component of the reference signal Ss included in the amplification detection signal S3. The gain at the time of amplification of the detection signal S1 is controlled so that it can be canceled by adding or subtracting the signal S3 and the reference signal Ss, and the signal component of the AC voltage V1 is extracted (generated) from the amplified detection signal S3 and output signal So. Output as. In this case, the signal component of the reference signal Ss included in the amplified detection signal S3 is the reference voltage component Vs1 included in the detection signal S1 (that is, having the same frequency as the reference signal Ss included in the amplified detection signal S3). Signal component).

  Next, the processing unit 33 performs the storage process, the voltage calculation process, and the output process in the same manner as the voltage detection apparatus 1, thereby calculating the effective value, the amplitude, and the like of the AC voltage V1, and configured by the display device. Displayed on the output unit 35. Thereby, the detection of the alternating voltage V1 of the detection target body 4 by the voltage detection apparatus 1 is completed.

  Therefore, also in this voltage detection device 1A, as in the voltage detection device 1, the signal extraction unit 32 makes the amplitude of the signal component having the same frequency as the reference signal Ss included in the amplified detection signal S3 constant. The amplitude of the amplified detection signal S3 is controlled, and by adding or subtracting the amplified detection signal S3 and the reference signal Ss, the same signal component as that of the reference signal Ss included in the amplified detection signal S3 is removed to obtain an output signal So. By outputting, even when the coupling capacitance (capacitance C0) between the detection object 4 and the detection electrode 12 is unknown (regardless of the value of the capacitance C0), the AC voltage V1 Since the sensitivity is controlled to be a constant sensitivity, that is, the amplitude of the voltage component based on the detection target current Iv1 included in the output signal So is a magnitude corresponding to the amplitude of the AC voltage V1. To be controlled so as, by detecting the voltage component contained in the output signal So., without performing the calculation of the electrostatic capacitance C0, it is possible to detect the AC voltage V1 in a non-contact manner.

  Also in the voltage detection device 1A, in the same manner as the voltage detection device 1, in the signal extraction unit 32, the synchronous detection circuit 43 performs a signal on the reference signal Ss included in the amplified detection signal S3 or the output signal So. A detection signal Vd indicating the amplitude of the component is detected by synchronous detection using the reference signal Ss, and the control circuit 44 controls the gain of the amplifier circuit 41 based on the detection signal Vd. Therefore, according to the voltage detection device 1, the signal component of the reference signal Ss can be accurately detected by synchronous detection. As a result, the signal component of the reference signal Ss included in the amplified detection signal S3 can be detected with high accuracy. Since the signal component of the reference signal Ss included in the output signal So can be greatly reduced, the detection accuracy of the AC voltage V1 can be further improved.

  Also in this voltage detection apparatus 1A, a signal component (anti-phase signal component) having a phase opposite to that of the reference signal Ss constituting the amplification detection signal S3 is canceled (cancelled) by the reference signal Sr (reference signal Ss in this example). The signal extraction unit 32 is configured by including an addition circuit 42 that performs processing as a cancellation circuit, and the control circuit 44 includes a negative-phase signal component (reference signal Ss) included in the amplified detection signal S3 input to the addition circuit 42. The gain of the amplifying circuit 41 is controlled so that the signal component can be canceled by the reference signal Sr. Therefore, also with this voltage detection device 1A, the canceling circuit can be configured with a simple circuit such as an adding circuit, so that the output signal So can be reliably generated while simplifying the device configuration.

  Note that the voltage detection apparatus 1A also uses the fact that the signal component of the reference signal Ss included in the amplified detection signal S3 is in reverse phase with respect to the reference signal Sr (reference signal Ss in this example). Thus, the adder circuit 42 is used as a canceling circuit to cancel the signal component of the reference signal Ss and the reference signal Ss contained in the amplified detection signal S3. It is also possible to invert the phase of the signal S1 and the amplification detection signal S3, or to invert the reference signal Sr to the cancellation circuit and output it. In this configuration, since the signal component of the reference signal Ss and the reference signal Ss included in the amplification detection signal S3 can be in phase, the subtraction circuit is used as the cancellation circuit according to this configuration. Thus, the signal component of the reference signal Ss and the reference signal Ss included in the amplification detection signal S3 can be canceled.

  In the above example, a configuration is adopted in which the reference signal Ss is directly input to the cancellation circuit (in the above example, the addition circuit 42) as the reference signal Sr. However, as indicated by a broken line in FIG. 31 and an adder circuit 42, an amplitude changing unit 36 is disposed, and the amplitude of the reference signal Ss output from the reference signal output unit 31 is multiplied by k (k is a positive real number) in the amplitude changing unit 36. It is also possible to adopt a configuration in which it is changed and output to the adder circuit 42 as the reference signal Sr1. According to this configuration, the range of the AC voltage V1 that can be detected (measured) can be expanded by changing the magnification k in the amplitude changing unit 36 in the same manner as the voltage detecting device 1.

  In the voltage detection device 1 described above, for example, between the insulating unit 15 and the amplifier circuit 41, between the reference signal output unit 31 and the addition circuit 42, and between the reference signal output unit 31 and the synchronous detection circuit 43. In the voltage detection device 1A, for example, between the detection unit 14A and the amplification circuit 41, between the reference signal output unit 31 and the addition circuit 42, and reference signal output Although a configuration in which the unit 31 and the synchronous detection circuit 43 are directly connected to each other is employed, a configuration in which a buffer is interposed may be employed as necessary, although not illustrated. Further, although an example in which the reference signal Ss output from the reference signal output unit 31 is supplied to the synchronous detection circuit 43 at the same level as described above has been described, although not illustrated, the reference signal Ss is configured by a voltage dividing resistor or the like as an example. It is also possible to employ a configuration in which the reference signal Ss is reduced to a required level and supplied to the synchronous detection circuit 43 using an attenuator.

  Although not shown, an A / D conversion unit that converts the insulation detection signal S2 that is an analog signal into digital data, and a reference signal Ss that is an analog signal supplied from the reference signal output unit 31 to the signal extraction unit 32. By providing an A / D conversion unit for converting into digital data in the main body circuit unit 3, it is possible to adopt a configuration in which all or part of the processing in the signal extraction unit 32 is performed by digital processing. In this case, it is possible to employ a configuration in which the processing unit 33 has the function of the signal extraction unit 32. According to this configuration, the number of circuit components can be significantly reduced. Further, the function of the processing unit 33 and the function of the signal extraction unit 32 may be realized by software, or may be realized by hardware (DSP (Digital Signal Processor) or logic array).

  Moreover, although the reference signal output unit 31 has been described above with respect to the example in which the AC signal (for example, a sine wave signal) having a constant frequency and amplitude is output as the reference signal Ss, as in the reference signal output unit 31A illustrated in FIG. Instead of the sine wave signal, a configuration in which a square wave signal is output as the reference signal Ss may be employed. Specifically, the reference signal output unit 31A integrates a square wave generation circuit 31a that generates a square wave (square wave signal), and a square wave (square wave signal) as an integrated square wave (integrated square wave signal). An integrating circuit 31b for outputting is provided. The reference signal output unit 31A outputs the square wave signal generated by the square wave generation circuit 31a as a reference signal Ss to the synchronous detection circuit 43 of the signal extraction unit 32, and also extracts the square wave signal as a reference signal Sr. The data is output to the adder circuit 42 of the unit 32. Further, the reference signal output unit 31A outputs the integrated square wave signal output from the integration circuit 31b to the detection unit 14 (detection unit 14A in the voltage detection device 1A) as the reference signal Ss. In this case, since the detection unit 14 (14A) is connected in series with the capacitance C0 via the detection electrode 12, the reference current Is1 flowing through the circuit including the detection unit 14 (14A) and the capacitance C0 is , A signal obtained by differentiating the reference signal Ss.

  Therefore, by integrating the reference signal Ss output from the reference signal output unit 31A to the detection unit 14 (14A) in advance by the integration circuit 31b, the square wave generation circuit 31a can be easily used using a logic circuit or the like. By configuring the reference signal output unit 31A, the reference current Is1 flowing through the circuit including the detection unit 14 (14A) and the capacitance C0 is extracted from the reference signal output unit 31A while the configuration of the entire reference signal output unit 31A is simplified. The square wave signal can be the same as the square wave signal output to 32. Thereby, while simplifying the device configuration (specifically, the entire configuration of the reference signal output unit 31A), in the signal extraction unit 32, the adder circuit 42 reverses the reference signal Ss constituting the amplification detection signal S3. The phase signal component can be reliably canceled (cancelled) by the reference signal Sr (reference signal Ss in this example), and the signal component of the AC voltage V1 is reliably extracted from the amplified detection signal S3 and output as the output signal So. In addition, the synchronous detection circuit 43 can surely synchronously detect the output signal So with the reference signal Ss.

  Moreover, it is also possible to employ a configuration in which a pseudo noise generation circuit 31c is provided and a pseudo noise signal is output as the reference signal Ss as in the reference signal output unit 31B illustrated in FIG. In this case, the reference signal output unit 31B outputs the pseudo noise signal generated by the pseudo noise generation circuit 31c to the detection unit 14 (14A) and the synchronous detection circuit 43 of the signal extraction unit 32 as a reference signal Ss, and this square shape. The wave signal is output as a reference signal Sr to the addition circuit 42 of the signal extraction unit 32. Further, the pseudo noise generation circuit 31c is configured by using various known shift registers such as a linear feedback shift register such as an M series as an example, or by using a microcomputer that generates a pseudo noise signal by software processing. Can do. By using the reference signal output unit 31B configured as described above, it is possible to realize the voltage detection device 1 (1A) that is not easily affected by disturbance (noise).

  Next, a line voltage detection device 51 using a plurality of the voltage detection devices 1 described above will be described.

  First, the configuration of the line voltage detection device 51 will be described with reference to the drawings. In the following, an example will be described in which line voltages of three-phase (R-phase, S-phase, and T-phase) three-wire AC circuits (hereinafter also referred to as “electric circuits”) R, S, and T are detected.

  As an example, the line voltage detection device 51 corresponds to the same number (three) of the electric circuits R, S, T as the number of electric circuits R, S, T (hereinafter referred to as each electric circuit R, S, T). Voltage detectors 1r, 1s, and 1t (hereinafter also referred to as “voltage detector 1” unless otherwise specified), a calculation unit 52, and a display unit 53, and a line voltage Vrs between electric circuits R and S, electric circuit S , T and the line voltage Vrt between the electric circuits R, T can be detected in a non-contact manner.

  As shown in FIG. 8, each voltage detection device 1 includes the above-described floating circuit unit 2 and main body circuit unit 3 and is configured in the same manner, and each AC circuit R, S, and T is used as a detection target body. The effective values of the voltages Vrp, Vsp, and Vtp (each AC voltage to be detected) are detected, and data indicating the effective values are output as detection data Dva, Dvb, and Dvc. Hereinafter, the detection data Dva, Dvb, and Dvc are also referred to as “detection data Dv” unless particularly distinguished. In this example, the output unit 35 of each voltage detection device 1 is configured by a transmission device capable of transmitting data, and has a function of transmitting the detection data Dva, Dvb, Dvc input from the processing unit 33 to the calculation unit 52. I have. In addition, since it is the same as the structure mentioned above about the other components except the output part 35 in the voltage detection apparatus 1, detailed description is abbreviate | omitted.

  The calculation unit 52 includes a CPU and a memory (both not shown), and calculates (detects) a line voltage based on the detection data Dv output from each voltage detection device 1. Execute the calculation process. The calculation unit 52 causes the display unit 53 to display the result of the line voltage calculation process. In this example, the display unit 53 is configured by a monitor device such as a liquid crystal display. In addition, it can also be comprised with printing apparatuses, such as a printer. Further, as will be described later, each body circuit unit 3 is connected to a portion (for example, a housing of the body circuit unit 3) G1 having a mutual ground potential Vg. As an example, the calculation unit 52 and the display unit 53 operate by receiving a voltage supply from a power supply circuit (not shown) included in any one of the three main body circuit units 3. To do.

  Next, the detection operation of the line voltage detection device 51 will be described.

  First, at the time of detection, as shown in FIG. 8, in order to detect the AC voltage Vrp of the electric circuit R by the voltage detection device 1r, the floating circuit portion 2 is brought close to the electric circuit R and the detection electrode 12 is moved to the corresponding electric circuit R. Make them face each other. Similarly, with respect to the other voltage detection devices 1s and 1t, the detection electrodes 12 of the floating circuit portions 2 are made to face the corresponding electric circuits S and T in order to detect the AC voltages Vsp and Vtp of the electric circuits S and T. . As a result, a capacitance C0 (see FIG. 1) is formed between each of the detection electrodes 12 and each of the electric circuits R, S, T, and the corresponding electric circuit in each of the voltage detection devices 1r, 1s, 1t. Detection of AC voltages Vrp, Vsp, Vtp of R, S, T is started. In this case, as described above, in each of the voltage detection devices 1r, 1s, and 1t, the AC voltages Vrp, Vsp, and Vtp are accurately detected by the processing unit 33 regardless of the capacitance value of the capacitance C0.

  Moreover, in each voltage detection apparatus 1r, 1s, and 1t, the output part 35 makes the effective value about AC voltage Vrp, Vsp, and Vtp of each electric circuit R, S, T calculated by the process part 33, detection data Dva, respectively. , Dvb, Dvc.

  The calculation unit 52 inputs each detection data Dva, Dvb, Dvc output from each voltage detection device 1 and stores it in the memory. Next, the calculation unit 52 executes a line voltage calculation process. Specifically, the calculation unit 52 obtains the line voltage Vrs between the electric circuits R and S by calculating the differential voltage between the effective values of the AC voltages Vrp and Vsp indicated by the detection data Dva and Dvb. (To detect). Similarly, the calculation unit 52 calculates the differential voltage between the effective values of the AC voltages Vsp and Vtp indicated by the detection data Dvb and Dvc, thereby calculating the line voltage Vst between the electric circuits S and T. The line voltage Vrt between the electric circuits R and T is obtained (detected) by calculating (detecting) and calculating the differential voltage between the effective values of the AC voltages Vrp and Vtp indicated by the detection data Dva and Dvc. ). The calculation unit 52 causes the display unit 53 to display the calculated line voltages Vrs, Vst, Vrt.

  Thus, according to this line voltage detection device 51, by using the voltage detection device 1, the detection electrode 12 in each voltage detection device 1 and each electric circuit R as a detection object of each voltage detection device 1 are used. , S, and T, even if the coupling capacitance (capacitance C0) is unknown, the line voltages Vrs, Vst, and Vrt are accurately detected without contact without calculating the coupling capacitance. can do.

  Next, a line voltage detection device 51A using a plurality of the voltage detection devices 1A described above will be described.

  First, the configuration of the line voltage detection device 51A will be described with reference to the drawings. In addition, about the structure same as the line voltage detection apparatus 51, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted. Moreover, below, the example which detects the line voltage of the electric circuit R, S, T of a three-phase three-wire system is demonstrated.

  As an example, as shown in FIG. 9, the line voltage detection device 51A corresponds to the same number (three) of the electric circuits R, S, T as the number of electric circuits R, S, T (hereinafter referred to as each electric circuit R, S, T). Voltage detectors 1Ar, 1As, 1At (hereinafter also referred to as “voltage detector 1A” unless otherwise specified), a calculation unit 52, and a display unit 53, and a line voltage Vrs between electric circuits R and S, electric circuit S , T and the line voltage Vrt between the electric circuits R, T can be detected in a non-contact manner.

  As shown in FIG. 9, each voltage detection device 1 </ b> A includes the above-described detection electrode 12, detection unit 14 </ b> A, and main body circuit unit 3, and is configured in the same way, with each electric circuit R, S, T as a detection target. The effective values of these AC voltages Vrp, Vsp, and Vtp (each AC voltage to be detected) are detected, and data indicating the effective values are output as detection data Dva, Dvb, and Dvc. In this example, the output unit 35 of each voltage detection device 1 is configured by a transmission device capable of transmitting data, and has a function of transmitting the detection data Dva, Dvb, Dvc input from the processing unit 33 to the calculation unit 52. I have. In addition, since it is the same as the structure mentioned above about the other components except the output part 35 in 1 A of voltage detection apparatuses, detailed description is abbreviate | omitted. Moreover, since the calculation part 52 and the display part 53 are also the same as the line voltage detection apparatus 51 mentioned above, detailed description is abbreviate | omitted.

  Next, the detection operation of the line voltage detection device 51A will be described.

  First, at the time of detection, as shown in FIG. 9, in order to detect the AC voltage Vrp of the electric circuit R with the voltage detection device 1Ar, the detection electrode 12 is brought close to the electric circuit R so as to face each other. Similarly, with respect to the other voltage detection devices 1As and 1At, in order to detect the AC voltages Vsp and Vtp of the electric circuits S and T, the detection electrodes 12 are made to face the corresponding electric circuits S and T, respectively. As a result, a capacitance C0 (see FIG. 4) is formed between each of the detection electrodes 12 and each of the electric circuits R, S, and T, and the corresponding electric circuit in each of the voltage detection devices 1Ar, 1As, and 1At. Detection of AC voltages Vrp, Vsp, Vtp of R, S, T is started. In this case, as described above, in each of the voltage detection devices 1Ar, 1As, and 1At, the AC voltage Vrp, Vsp, and Vtp are accurately detected by the processing unit 33 regardless of the capacitance value of the capacitance C0.

  Further, in each voltage detection device 1Ar, 1As, 1At, the output unit 35 calculates the effective value for the AC voltages Vrp, Vsp, Vtp of the electric circuits R, S, T calculated by the processing unit 33, respectively, as the detection data Dva. , Dvb, Dvc.

  The calculation unit 52 inputs each detection data Dva, Dvb, Dvc output from each voltage detection device 1 and stores it in the memory. Next, the calculation unit 52 executes a line voltage calculation process, and calculates a differential voltage between the effective values of the AC voltages Vrp and Vsp indicated by the detection data Dva and Dvb, whereby the electric circuits R and S are connected. The line voltage Vrs between the electric circuits S and T is obtained by calculating the differential voltage between the effective values of the AC voltages Vsp and Vtp indicated by the detection data Dvb and Dvc. Moreover, the line voltage Vrt between each electric circuit R and T is calculated | required by calculating the differential voltage of each effective value of AC voltage Vrp and Vtp shown by each detection data Dva and Dvc. The calculation unit 52 causes the display unit 53 to display the calculated line voltages Vrs, Vst, Vrt.

  Thus, according to this line voltage detection device 51A, by using the voltage detection device 1A, the detection electrode 12 in each voltage detection device 1A and each electric circuit R as a detection object of each voltage detection device 1A. , S, and T, even if the coupling capacitance (capacitance C0) is unknown, the line voltages Vrs, Vst, and Vrt are accurately detected without contact without calculating the coupling capacitance. can do.

  The power supply unit 13 that generates the floating voltages Vf + and Vf− used in the voltage detection device 1 includes a battery and a DC / DC converter (both not shown), and a guard instead of the battery. An AC voltage is supplied into the guard electrode 11 in a state of being electrically insulated from the outside of the electrode 11 through a transformer, and this AC voltage is converted into a DC voltage by a rectifying / smoothing unit provided in the guard electrode 11. As described above with reference to the configuration for supplying to the DC / DC converter, as shown in FIG. Based on the operating voltage (positive voltage Vcc + and negative voltage Vcc− generated with reference to the ground potential Vg) supplied from a power source (not shown), Pressure Vr, i.e. above the floating voltage relative to the voltage Vs (zero volt) of the reference signal Ss Vf +, it is also possible to employ a configuration that uses the power unit 13A for generating a Vf-.

  As shown in FIG. 11, when the voltage Vr of the guard electrode 11 is zero volts, the power supply unit 13A has a floating voltage Vf + that is a constant positive voltage with respect to the voltage Vr of the guard electrode 11 based on the positive voltage Vcc +. And the first series power supply circuit 61 that generates a difference between the floating voltage Vf− (the difference between the voltage Vr− and the floating voltage Vf−), which is a negative voltage whose absolute value is equal to the voltage Vr of the guard electrode 11 based on the negative voltage Vcc−. And a second series power supply circuit 62 that generates a voltage whose absolute value is equal to the absolute value of the difference between the floating voltage Vf + and the voltage Vr. Specifically, the first series power supply circuit 61 includes an NPN-type bipolar transistor 61a (hereinafter also referred to as “first transistor 61a”), a first resistor 61b, a first Zener diode 61c (zener voltage Vz), and a first capacitor. 61d. In this case, the first transistor 61a has a collector terminal connected to the supply line of the positive voltage Vcc +, an emitter terminal connected to the output line of the floating voltage Vf +, and a base terminal connected to the cathode terminal of the Zener diode 61c. The first Zener diode 61c has an anode terminal connected to the supply line of the voltage Vr. The first resistor 61b has one end connected to the collector terminal of the first transistor 61a and the other end connected to the base terminal. The first capacitor 61d has one end connected to the emitter terminal of the first transistor 61a and the other end connected to a supply line for the voltage Vr.

  The second series power supply circuit 62 includes a PNP bipolar transistor 62a (hereinafter also referred to as “second transistor 62a”), a second resistor 62b, a second Zener diode 62c (the same Zener voltage Vz as the first Zener diode 61c), and A second capacitor 62d is provided. In this case, in the second transistor 62a, the base-emitter terminal voltage Vbe is defined to be the same as that of the first transistor 61a, the collector terminal is connected to the supply line of the negative voltage Vcc−, and the emitter terminal is connected to the floating voltage Vf−. The base terminal is connected to the anode terminal of the second Zener diode 62c. The second Zener diode 62c has a cathode terminal connected to the supply line of the voltage Vr. The second resistor 62b has one end connected to the collector terminal of the second transistor 62a and the other end connected to the base terminal. The second capacitor 62d has one end connected to the emitter terminal of the second transistor 62a and the other end connected to a supply line for the voltage Vr.

  With the above configuration, in the power supply unit 13A, the first series power supply circuit 61 generates and outputs the floating voltage Vf + (= Vr + Vz−Vbe) from the positive voltage Vcc +, and the second series power supply circuit 62 outputs the negative voltage Vcc. A floating voltage Vf − (= Vr−Vz + Vbe) is generated from − and output. Specifically, in the first series power supply circuit 61, the first Zener diode 61c is supplied with current from the first resistor 61b to generate the Zener voltage Vz at the cathode terminal, and the base terminal is regulated to the Zener voltage Vz. The first transistor 61a generates a voltage (Vz−Vbe) with respect to the anode terminal of the first Zener diode 61c as the emitter terminal. Therefore, the first series power supply circuit 61 generates and outputs a floating voltage Vf + whose voltage is (Vr + Vz−Vbe) with respect to the ground potential Vg. In the second series power supply circuit 62, the second Zener diode 62c is supplied with current from the second resistor 62b to generate the Zener voltage Vz at the anode terminal, and the second transistor has the base terminal defined by the Zener voltage Vz. 62a generates a voltage (−Vz + Vbe) with respect to the anode terminal of the second Zener diode 62c as an emitter terminal. Therefore, the second series power supply circuit 62 generates and outputs the floating voltage Vf− in which the voltage with respect to the ground potential Vg is (Vr−Vz + Vbe).

  That is, as long as the voltage Vr fluctuates while the voltage (Vr + Vz−Vbe) does not reach the positive voltage Vcc + and the voltage (Vr−Vz + Vbe) does not reach the negative voltage Vcc−, the power supply unit 13A While following the variation of Vr, a floating voltage Vf + that is a positive voltage having an absolute value | Vz−Vbe | equal to the voltage Vr and a floating voltage Vf− that is a negative voltage are generated and output. Therefore, each circuit in the floating circuit section 2 operates normally upon receiving the supply of the floating voltages Vf + and Vf−, and as a result, the insulation detection signal S2 is normally output from the floating circuit section 2. Therefore, by using this power supply unit 13A, it is possible to avoid the use of expensive parts such as a battery and a transformer. As a result, the product cost of the voltage detection device 1 can be significantly reduced. Although not shown, a known overcurrent protection circuit or a known overvoltage protection circuit can be added to each of the series power supply circuits 61 and 62.

  In addition, the configuration in which the insulating unit 15 is disposed in the floating circuit unit 2 and the detection signal S1 detected by the detection unit 14 is converted into the insulation detection signal S2 electrically insulated from the detection signal S1 and output is described above. However, as shown in FIG. 12, a configuration in which the insulating portion 15 is not disposed in the floating circuit portion 2 may be employed. In this configuration, a detection signal S1 and a signal indicating the voltage Vr are output from the floating circuit unit 2 to the main body circuit unit 3 as a pair, and the detection signal S1 and the voltage Vr are arranged in the main circuit unit 3. It is also possible to adopt a configuration in which 63 is input and the detection signal S2a indicating the difference between the detection signal S1 and the voltage Vr is output to the amplifier circuit 41 instead of the insulation detection signal S2.

  As shown in FIG. 12 as an example, the differential amplifier circuit 63 includes an operational amplifier 63a, an input resistor 63b disposed between the inverting input terminal of the operational amplifier 63a and the amplifier circuit 22 of the floating circuit unit 2, an arithmetic circuit 63 An input resistor 63c disposed between the non-inverting input terminal of the amplifier 63a and the guard electrode 11 of the floating circuit section 2, a feedback resistor 63d for the operational amplifier 63a, and a non-inverting input terminal of the operational amplifier 63a and the ground potential Vg. The resistor 63e disposed between the two can be used. In addition, in the configuration shown in FIG. 12, any of the power supply units 13 and 13A described above can be used as a power supply for supplying the respective floating voltages Vf + and Vf− to the respective components of the floating circuit unit 2.

  Further, as shown in FIG. 11, the reference signal output unit 31 is made to function as a new reference signal output unit as a whole by adding an operational amplifier AP4 configured in a voltage follower circuit to the reference signal output unit 13. Therefore, it is possible to adopt a configuration in which the reference signal Ss generated by the reference signal output unit 13 is output with lower impedance.

1, 1A, 1r, 1s, 1t, 1Ar, 1As, 1At Voltage detection device 2 Floating circuit part 3 Main body circuit part 4 Detection object 11 Guard electrode 11a Opening part 12 Detection electrode 13, 13A Power supply part 14, 14A Detection part 15 Insulating section 31, 31A, 31B Reference signal output section 32 Signal extraction section 33 Processing section 36 Amplitude changing section 41 Amplifying circuit 42 Adder circuit 43 Synchronous detection circuit 44 Control circuit 51, 51A Line voltage detection device 52 Calculation section I Current signal R , S, T circuit S1 detection signal S2 insulation detection signal S3 amplification detection signal So output signal Ss reference signal V1, Vrp, Vsp, Vtp AC voltage Vdi potential difference Vrs, Vrt, Vst line voltage

Claims (14)

A voltage detection device for detecting a detection target alternating voltage generated in a detection target body,
A detection electrode disposed opposite to the detection object and capacitively coupled to the detection object;
A reference signal output unit for outputting a reference signal;
Detection in which amplitude is changed according to both current values of a detection target current flowing based on the detection target AC voltage and a reference current flowing based on the reference signal by being connected to the detection electrode and inputting the reference signal A detector for outputting a signal;
While amplifying the detection signal with a predetermined gain to generate an amplified detection signal, the reference signal and the amplified detection signal are added or subtracted between the reference signal output from the reference signal output unit and the amplified detection signal. A signal extractor that controls the gain so as to cancel out the signal component of the reference signal included in the signal, and extracts the signal component of the detection target AC voltage from the amplified detection signal and outputs the signal as an output signal. Equipped with a voltage detection device. A voltage detection device for detecting a detection target alternating voltage generated in a detection target body,
A detection electrode disposed opposite to the detection object and capacitively coupled to the detection object;
It operates with a floating power source generated with reference to the voltage of the reference voltage unit, and outputs a detection signal whose amplitude changes in accordance with the AC potential difference between the detection target AC voltage and the voltage of the reference voltage unit. A detection unit;
A reference signal output unit that outputs a reference signal to the reference voltage unit;
While amplifying the detection signal with a predetermined gain to generate an amplified detection signal, the reference signal and the amplified detection signal are added or subtracted between the reference signal output from the reference signal output unit and the amplified detection signal. A signal extractor that controls the gain so as to cancel out the signal component of the reference signal included in the signal, and extracts the signal component of the detection target AC voltage from the amplified detection signal and outputs the signal as an output signal. Equipped with a voltage detection device.   The signal extraction unit indicates an amplification circuit that amplifies the detection signal with the gain to generate the amplified detection signal, and indicates an amplitude of the signal component of the reference signal included in the amplified detection signal or the output signal A synchronous detection circuit that detects a detection signal by synchronous detection using the reference signal output from the reference signal output unit; and a control circuit that controls the gain of the amplifier circuit based on the detection signal. The voltage detection apparatus according to claim 1 or 2. A voltage detection device for detecting a detection target alternating voltage generated in a detection target body,
A detection electrode disposed opposite to the detection object and capacitively coupled to the detection object;
It operates with a floating power source generated with reference to the voltage of the reference voltage unit, and outputs a detection signal whose amplitude changes in accordance with the AC potential difference between the detection target AC voltage and the voltage of the reference voltage unit. A detection unit;
A reference signal output unit that outputs a reference signal to the reference voltage unit;
An insulating part that inputs the detection signal and electrically insulates and outputs an insulation detection signal;
While amplifying the insulation detection signal with a predetermined gain to generate an amplification detection signal, the reference signal and the amplification detection are added or subtracted between the reference signal output from the reference signal output unit and the amplification detection signal. A signal extraction unit that controls the gain so as to cancel out the signal component of the reference signal included in the signal, and extracts the signal component of the detection target AC voltage from the amplified detection signal and outputs the signal as an output signal; A voltage detection device comprising:   The signal extraction unit amplifies the insulation detection signal with the gain to generate the amplification detection signal, and an amplitude of the signal component of the reference signal included in the amplification detection signal or the output signal. A synchronous detection circuit that detects a detected detection signal by synchronous detection using the reference signal output from the reference signal output unit, and a control circuit that controls the gain of the amplifier circuit based on the detection signal. The voltage detection device according to claim 4.   A first floating voltage that is a constant positive voltage with respect to the voltage of the reference signal is generated based on the positive voltage of the positive voltage and the negative voltage supplied to the reference signal output unit and the signal extraction unit. A power supply comprising: a first series power supply circuit; and a second series power supply circuit that generates a second floating voltage having a negative voltage equal in absolute value to the first floating voltage with respect to the voltage of the reference signal based on the negative voltage 6. The voltage detection device according to claim 2, wherein the power supply unit supplies the floating voltages to the detection unit. The first series power supply circuit includes a first resistor connected to the positive voltage, a first Zener diode that operates upon receiving a current from the first resistor, and a collector terminal connected to the positive voltage. A first transistor that receives a Zener voltage of the first Zener diode at a terminal and generates the first floating voltage at an emitter terminal;
The second series power supply circuit includes a second resistor connected to the negative voltage, a second Zener diode that operates upon receiving a current from the second resistor, and a collector terminal connected to the negative voltage. The voltage detection device according to claim 6, further comprising a second transistor that receives the Zener voltage of the second Zener diode at a terminal and generates the second floating voltage at an emitter terminal.   The signal extraction unit cancels the reference signal output from the reference signal output unit and the signal component of the reference signal by the addition and outputs the output signal, or from the reference signal output unit 8. The voltage detection device according to claim 1, further comprising a subtraction circuit that cancels the output reference signal and the signal component of the reference signal by the subtraction and outputs the output signal. 9. An amplitude changing unit that changes the amplitude of the reference signal output from the reference signal output unit and outputs it to the signal extraction unit,
9. The voltage detection according to claim 1, wherein the signal extraction unit controls the gain so that the reference signal having the amplitude changed by the amplitude changing unit and the signal component of the reference signal can be canceled out. 10. apparatus.   The voltage detection apparatus in any one of Claim 1 to 9 provided with the process part which detects the said detection object alternating voltage based on the said output signal.   The voltage detection device according to claim 10, wherein the processing unit calculates a voltage value of the detection target AC voltage based on the output signal.   The reference signal output unit includes a square wave generation circuit that generates a square wave, and an integration circuit that integrates the square wave and outputs the integrated square wave, and outputs the integration square wave to the detection unit as the reference signal. The voltage detection device according to claim 1, wherein the square wave is output as the reference signal to the signal extraction unit.   12. The reference signal output unit includes a pseudo noise generation circuit that generates pseudo noise, and outputs the pseudo noise as the reference signal to the detection unit and the signal extraction unit. Voltage detection device. The plurality of corresponding electric circuits as the detection object are configured such that the detection electrodes can face each other, and an AC voltage generated in each electric circuit can be detected as the detection object AC voltage, respectively. Any one of the voltage detection devices;
A calculating unit that calculates a differential voltage between the AC voltages of two electric circuits detected by a pair of voltage detecting devices out of the plurality of voltage detecting devices, and obtains a line voltage between the two electric circuits; Line voltage detection device.

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