JP2010025918A - Voltage detection device and line voltage detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a voltage of a detection object having a high voltage, while avoiding use of a high breakdown voltage electronic component. <P>SOLUTION: This voltage detection device 1 for detecting an AC voltage V1 generated in the detection object 4 includes a detection electrode 22 disposed oppositely to the detection object 4; a current-voltage conversion circuit 23 wherein a noninverting input terminal is regulated at a reference voltage (voltage of a voltage signal V4), for converting into a detection voltage signal V2, a current signal I flowing between itself and a measuring object 4 through the detection electrode 22 with a current value corresponding to an AC potential difference Vdi between an IC voltage V1 and the reference voltage, and outputting the signal; an integration circuit 24 for integrating the detection voltage signal V2, and outputting an integration signal V3 whose amplitude is changed corresponding to the potential difference Vdi; a photocoupler 26 disposed on a subsequent stage of the integration circuit 24, for outputting the input integration signal V3 in the electrically insulated state; and a voltage generation circuit 34 for generating a voltage signal V4 by amplifying a signal based on the integration signal V3 to reduce the potential difference Vdi. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a voltage detection device that detects the voltage of a detection object, and a line voltage detection device that includes 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 Japanese Patent Publication No. 7-58297 is known. This voltage detection device is a non-contact potential measurement device that reads changes in potential of a detection target (sample) in a non-contact manner, and detects a field emission current or a tunnel current through a metal needle with a sharp tip and this metal needle. A feedback circuit for applying a voltage to the metal needle so that the current of the lever is constant and a circuit for reading the voltage of the metal needle are provided. In this voltage detection device, when the metal needle is held close to the detection object, the voltage applied to the metal needle is controlled by the feedback circuit so that the field emission current or the tunnel current becomes constant. Therefore, since the voltage of the metal needle at this time follows the voltage of the detection object, it is possible to read the change in the voltage of the detection object by reading the voltage of the metal needle.

Japanese Patent Publication No. 7-58297 (2nd page, Fig. 1)

  However, the above voltage detection device has the following problems. That is, in this voltage detection apparatus, a metal needle whose voltage changes following the voltage of the detection object (sample) is directly connected to the input terminal of the current-voltage converter. Therefore, in order to make this voltage detection device usable for a detection object having a high voltage, a current-voltage converter is configured using a high-voltage operational amplifier, that is, a high-voltage electronic component. There is a problem that the cost of the apparatus increases.

  The present invention has been made to solve the above-mentioned problem, and can detect the voltage of a detection object having a high voltage (non-contact type) while avoiding the use of high-voltage electronic components. The main purpose is to provide a device.

  In order to achieve the above object, the voltage detection device according to claim 1 is a voltage detection device that detects a detection target AC voltage generated in a detection target body, and is a detection device disposed opposite to the detection target body. An electrode and a first input terminal are defined as a reference voltage, and a second input terminal is directly or indirectly connected to the detection electrode, and a feedback is connected to the detection electrode and the second input terminal. A current-voltage conversion circuit having an operational amplifier that converts a detection current flowing at a current value corresponding to an AC potential difference between the detection target AC voltage and the reference voltage into a detection voltage signal and outputs the detection voltage signal in a path including the circuit An integration circuit that integrates the detection voltage signal and outputs an integration signal whose amplitude changes in accordance with the potential difference, and is disposed in a front stage or a rear stage of the integration circuit, and includes the detection voltage signal and the integration signal. of It comprises an insulating circuit electrically insulate and outputs and inputs towards, and a voltage generating circuit for amplifying a signal based on the integration signal such that the potential difference is reduced to generate the reference voltage.

  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, the detection electrode disposed to face the detection target body, A detector that is disposed between a detection electrode and a reference voltage portion and converts a detection current flowing at a current value corresponding to an AC potential difference between the detection target AC voltage and the reference voltage into a voltage signal; And a current-voltage conversion circuit having an amplifier that impedance-converts the voltage signal and outputs it as a detection voltage signal, an integration circuit that integrates the detection voltage signal and outputs an integration signal whose amplitude changes according to the potential difference, An insulation circuit that is arranged in a preceding stage or a subsequent stage of the integration circuit and inputs one of the detection voltage signal and the integration signal and electrically insulates the output, and the potential difference is reduced. Amplifies the signal based on sea urchin said integration signal and a voltage generation circuit for generating the reference voltage.

  According to a third aspect of the present invention, there is provided a voltage detection device for detecting a detection target alternating voltage generated in a detection target body, wherein the detection electrode disposed opposite to the detection target body, The first input terminal is defined as a reference voltage, and the second input terminal is connected directly or indirectly to the detection electrode, and includes a detection circuit and a feedback circuit connected to the second input terminal. An operational amplifier that outputs an integration signal whose amplitude changes according to the potential difference by integrating a detection current flowing at a current value corresponding to the AC potential difference between the detection target AC voltage and the reference voltage in the path. An integration circuit having an integration circuit that receives the integration signal and electrically insulates and outputs the signal; and a voltage generator that amplifies a signal based on the integration signal to reduce the potential difference and generates the reference voltage And a road.

  According to a fourth aspect of the present invention, there is provided the voltage detecting device according to any one of the first to third aspects, wherein the insulating circuit includes an optical insulating element and / or a transformer.

  A voltage detection device according to claim 5 is the voltage detection device according to any one of claims 1 to 3, wherein the insulating circuit includes a digital isolator.

  The voltage detection device according to claim 6 is the voltage detection device according to any one of claims 1 to 5, further comprising a guard electrode defined by the reference voltage, and the insulation from a circuit subsequent to the detection electrode. The space up to the primary circuit of the circuit is covered with the guard electrode.

  The voltage detection device according to claim 7 is the voltage detection device according to claim 6, wherein an opening is formed in the guard electrode, and the detection electrode is located at a position facing the opening in the guard electrode. It arrange | positions in the state which does not protrude from the said opening part.

  The voltage detection device according to claim 8 is the voltage detection device according to any one of claims 1 to 7, further comprising an insulator covering the entire surface of the detection electrode facing the detection object.

  The line voltage detection device according to claim 9 is configured such that the detection electrode 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 8, 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 calculation unit for calculating a line voltage between the two electric circuits by calculating a differential voltage of the two.

  In the voltage detection device according to claim 1, in a state where the detection electrode is arranged to face the detection target body, the current-voltage conversion circuit includes the capacitance and the detection formed between the detection target body and the detection electrode. A detection current that flows at a current value corresponding to a potential difference between the detection target AC voltage and the reference voltage in a path including the detection electrode and the feedback circuit connected to the second input terminal via the electrode is converted into a detection voltage signal. The integration circuit integrates this detection voltage signal (specifically, a current that flows based on the potential difference between the detection voltage signal and the reference voltage) to obtain a potential difference between the voltage of the detection electrode and the AC voltage of the detection object. In response, an integration signal whose amplitude changes is generated, and an insulation circuit disposed in the front stage or the rear stage of the integration circuit inputs one of the detection voltage signal and the integration signal and electrically isolates and outputs it. Voltage generation circuit , The potential difference between the detected AC voltage and the reference voltage have amplifies the signal based on the integrated signal so as to reduce to generate a reference voltage.

  Therefore, according to this voltage detection device, since the capacitance value of the capacitance is generally extremely small, the impedance between the detection object and the detection electrode can be set to a sufficiently large value (several MΩ). As a result, the input impedance of the current-voltage conversion circuit can be made relatively small, so that overvoltage is hard to be applied to the current-voltage conversion circuit, and inexpensive electronic components (for example, operational amplifiers) with low input withstand voltage are used for the current-voltage conversion circuit. Even if it does, possibility that a current-voltage conversion circuit will be destroyed by the potential difference of a detection object alternating voltage and a reference voltage can be reduced significantly. Further, such a destruction can be surely avoided by adding a protection circuit such as a diode.

  In addition, according to the voltage detection device of the second aspect, since the input impedance of the current-voltage conversion circuit can be made relatively small as in the case of the voltage detection device described above, it is difficult for overvoltage to be applied, and the detection target AC voltage and The possibility that the current-voltage conversion circuit is destroyed by the potential difference of the reference voltage can be greatly reduced.

  Further, according to the voltage detection device of the third aspect, since the input impedance of the current-voltage conversion circuit can be made relatively small as in the case of the voltage detection device described above, it is difficult to apply an overvoltage, and the detection target AC voltage and The possibility that the integration circuit is destroyed by the potential difference of the reference voltage can be greatly reduced.

  According to the voltage detection device of the fourth aspect, since the insulating circuit is configured by using the optical insulating element and / or the transformer, the current-voltage conversion circuit and the subsequent circuit can be simplified at an arbitrary portion. Can be electrically insulated (separated). In addition, when an optical insulating element is used, since the frequency characteristics are good over a wide frequency range, it is possible to accurately detect the AC voltage of the detection object over a wide frequency range. In addition, when a transformer is used as an insulating circuit, the transformer generally has good frequency characteristics in a higher frequency range than the optical insulating element, and therefore the frequency of the AC voltage is limited to a high frequency. Sometimes, a transformer can be used to accurately detect an AC voltage. In addition, when an insulation circuit is configured by connecting an optical insulation element and a transformer in parallel, the optical insulation element mainly operates on the low frequency side and the transformer mainly operates on the high frequency side. As a result, it is possible to accurately detect the AC voltage of the detection object over a wider frequency range.

  According to the voltage detection device of the fifth aspect, since the insulation circuit is configured using the digital isolator, the insulation circuit is affected by the temperature of the transmission line for transmitting the electrically insulated signal, the change with time, and the like. Since this signal can be transmitted to the voltage generation circuit with high accuracy without any problem, the detection accuracy of the AC voltage to be detected can be further improved.

  According to the voltage detection device of the sixth aspect of the present invention, the space from the circuit behind the detection electrode to the primary circuit of the insulation circuit is accommodated in the guard electrode, and these are covered with the guard electrode. As a result of these circuits being less susceptible to the influence of an external electric field, the detection accuracy of the AC voltage to be detected can be improved.

  According to the voltage detection device of claim 7, the detection electrode is disposed in the guard electrode at a position facing the opening formed in the guard electrode so as not to protrude from the opening (non-projecting state). As a result, the detection electrode can be made less susceptible to the influence of an external electric field, and as a result, the detection accuracy of the detection target AC voltage can be further improved.

  In addition, according to the voltage detection device of the eighth aspect, the entire surface of the detection electrode facing the detection target body is covered with the insulator, thereby reliably preventing a short circuit between the detection target body and the detection electrode. be able to.

  According to the line voltage detecting device of the ninth aspect, since the voltage detecting device is used, an inexpensive electronic component (for example, an operational amplifier) having a low input withstand voltage is used for the current-voltage conversion circuit in each voltage detecting device. Even if it is used, it is possible to avoid destruction of the current-voltage conversion circuit due to the potential difference between the AC voltage to be detected and the reference voltage, so that the line voltage can be detected while reducing the device cost.

1 is a configuration diagram of a voltage detection device 1. FIG. 3 is a perspective view of a floating circuit unit 2. FIG. FIG. 3 is a conceptual cross-sectional view taken along the line WW in FIG. 2 for explaining the structure of the floating circuit section 2. It is a circuit diagram which shows the other structure of the current-voltage conversion part CV. It is a circuit diagram which shows the other structure of the current-voltage conversion part CV. It is a circuit diagram which shows the other structure of the current-voltage conversion part CV. It is a block diagram of other voltage detection apparatuses 1A. It is a block diagram of the other voltage detection apparatus 1B. It is a block diagram of the line voltage detection apparatus 51 which uses the voltage detection apparatus 1. 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 voltage detection device, and includes a floating circuit portion 2 and a main body circuit portion 3 as shown in FIG. 1, and an alternating current generated in a detection object (measurement object) 4. The voltage V1 (detection target AC voltage) can be detected (measured) in a non-contact manner.

  As shown in FIGS. 1, 2, and 3, the floating circuit unit 2 includes a guard electrode 21, a detection electrode 22, a current-voltage conversion unit CV, a drive circuit 25, and an insulation circuit 26. In this example, the current-voltage conversion unit CV includes a current-voltage conversion circuit 23 and an integration circuit 24 as an example. In this example, the insulating circuit 26 is configured by a photocoupler (hereinafter also referred to as “photocoupler 26”). The guard electrode 21 is configured as a reference voltage unit in the floating circuit unit 2 using a conductive material (for example, a metal material), and as an example, a circuit from the circuit subsequent to the detection electrode 22 to the insulating circuit 26 is provided therein. That is, the current-voltage conversion circuit 23, the integration circuit 24, the drive circuit 25, and the photocoupler 26 are accommodated. Thus, the configuration from the current-voltage conversion circuit 23 to the photocoupler 26 is covered with the guard electrode 21. The portion to be covered with the guard electrode 21 is a circuit on the downstream side of the detection electrode 22 (a circuit connected to the detection electrode 22; in this example, a current-voltage conversion circuit 23) to a primary circuit of a photocoupler 26 (a light emitting diode described later). ). For this reason, the secondary circuit (phototransistor described later) of the photocoupler 26 may be configured not to be covered with the guard electrode 21. As an example, in the case of an optical insulating element such as a photocoupler 26 in which a primary side circuit and a secondary side circuit are sealed in one package with a resin material, a portion including the primary side circuit in the package. (Half of the light emitting diode side of the package) is located inside the guard electrode 21, and a portion including the secondary side circuit (half of the phototransistor side of the package) protrudes (exposes) to the outside of the guard electrode 21. The photocoupler 26 is disposed with respect to the guard electrode 21. The guard electrode 21 has an opening (hole) 21a. In this example, as shown in FIGS. 2 and 3, the entire guard electrode 21 is covered with an insulating layer (an example of an insulator) 21b. It has been broken. For example, the detection electrode 22 is formed in a flat plate shape and does not protrude from the opening 21a to the outside of the guard electrode 21 at a position facing the opening 21a in the guard electrode 21 (that is, the surface of the detection electrode 22 is guarded). It is arranged in a non-projecting state in which it is recessed from the surface of the electrode 21. Since the entire guard electrode 21 is thus covered with the insulating layer 21b and the detection electrode 22 is disposed at a position facing the opening 21a, the insulating layer 21b faces the detection target body 4 in the detection electrode 22. The entire surface is covered.

  As an example, as shown in FIG. 1, the current-voltage conversion circuit 23 has a non-inverting input terminal (first input terminal) connected to the guard electrode 21 via a resistor 23a and an inverting input terminal (second input terminal). Input terminal) is connected to the detection electrode 22, and a resistor 23b is provided as a feedback circuit with a first operational amplifier 23c connected between the inverting input terminal and the output terminal. In the current-voltage conversion circuit 23, the first operational amplifier 23c operates by receiving supply of a positive voltage Vf + and a negative voltage Vf−, which will be described later, and the AC voltage V1 of the detection object 4 and the voltage of the guard electrode 21 (reference voltage). ) And the detection object 4 and the detection electrode 22 at a current value corresponding to the potential difference Vdi due to the potential difference (AC potential difference, that is, the potential difference between the AC component of the AC voltage V1 and the AC component of the reference voltage) Vdi. (Specifically, a path including the detection electrode 22 and the resistor 23b) I is converted into a detection voltage signal V2 and output. In this case, the amplitude of the detection voltage signal V2 changes in proportion to the amplitude of the current signal I.

  As an example, the integrating circuit 24 has a non-inverting input terminal connected to the guard electrode 21 via the resistor 24a, an inverting input terminal connected to the output terminal of the first operational amplifier 23c via the input resistor 24b, and The capacitor 24c includes a second operational amplifier 24d connected between the inverting input terminal and the output terminal as a feedback circuit. In the integrating circuit 24, the second operational amplifier 24d operates by receiving the supply of the positive voltage Vf + and the negative voltage Vf−, and integrates the detection voltage signal V2, whereby the AC voltage V1 of the detection object 4 and the guard electrode are integrated. The integrated signal V3 whose voltage value changes in proportion to the potential difference Vdi from the voltage 21 (reference voltage) is generated and output. The integrating circuit 24 can be configured by a low-pass filter instead of the above configuration.

  The drive circuit 25 is arranged with the photocoupler 26 at the subsequent stage of the integration circuit 24, that is, between the integration circuit 24 and the voltage generation circuit 34. For example, the drive circuit 25 has a base terminal connected to the output terminal of the second operational amplifier 24d via the input resistor 25a, a collector terminal connected to the photocoupler 26, and an emitter terminal connected to the negative voltage Vf−. Transistor 25b (in this example, an NPN bipolar transistor as an example). The photocoupler 26 is included in an optical isolation element which is an example of an isolation circuit. The light emitting diode as a primary side circuit of the photocoupler 26 has a cathode terminal connected to the collector terminal of the transistor 25b and an anode terminal connected to a positive voltage Vf +. It is connected to the. The phototransistor as the secondary circuit of the photocoupler 26 is connected to the main body circuit unit 3 through the wiring W1. With this configuration, when the photocoupler 26 is driven by the drive circuit 25 and operates in the linear region, the resistance value of the phototransistor in the photocoupler 26 changes according to the voltage value of the integration signal V3 (substantially in proportion). . Therefore, the photocoupler 26 is coupled with a resistor 33 of the main body circuit section 3 to be described later, and an integration signal V3 that is an analog signal input from the integration circuit 24 is newly insulated from the integration signal V3. Is converted into an integrated signal V3a which is a simple analog signal. Further, instead of the photocoupler 26, an optical MOS-FET which is the same optical insulating element can be used. In this case, in the optical MOS-FET, the light emitting diode as its primary circuit is connected to the transistor 25b and the like in the same manner as the light emitting diode of the photocoupler 26, and the FET pair as its secondary circuit connects the wiring W1. And connected to the main body circuit unit 3.

  As shown in FIG. 1, the main body circuit unit 3 includes, as an example, a main power supply circuit 31, a DC / DC converter (hereinafter also simply referred to as “converter”) 32, a resistor 33 for current / voltage conversion, a voltage generation circuit 34, and A voltmeter 35 is provided. The main power supply circuit 31 includes, for example, a battery, and is generated with reference to the positive voltage Vdd and the negative voltage Vss (the potential of the ground G1) for operating the components 32 and 34 of the main body circuit unit 3. DC voltages having the same absolute value but different polarities are generated from the DC voltage of the battery and output. For example, the converter 32 is induced in an isolated transformer having a primary winding and a secondary winding that are electrically insulated from each other, a drive circuit that drives the primary winding of the transformer, and a secondary winding of the transformer. And a DC converter (not shown) that rectifies and smoothes the AC voltage that is applied, and is configured as an insulated power source in which the secondary side is electrically insulated from the primary side. In this converter 32, the drive circuit operates based on the input positive voltage Vdd and negative voltage Vss, and drives the primary winding of the transformer in a state where the positive voltage Vdd is applied to the secondary winding with an AC voltage. Induces. The direct current converter rectifies and smoothes the alternating voltage. As a result, with the internal reference potential (internal ground) as a reference, the voltages (positive voltage Vf + and negative voltage Vf−) are in a floating state (electrically separated from ground G1, positive voltage Vdd and negative voltage Vss). Generated. The positive voltage Vf + and the negative voltage Vf− generated in this way are supplied to the floating circuit unit 2 in a state where the internal ground is electrically connected to the guard electrode 21. The positive voltage Vf + and the negative voltage Vf− are generated as direct current voltages having substantially the same absolute value and different polarities.

  The resistor 33 has one end connected to the positive voltage Vdd and the other end connected to the collector terminal of the phototransistor in the photocoupler 26. As a result, the resistor 33 and the phototransistor are connected in series between the positive voltage Vdd and the negative voltage Vss. For this reason, when the resistance value of the phototransistor changes according to the voltage value of the integration signal V3, the potential difference (Vdd−Vss) between the positive voltage Vdd and the negative voltage Vss is the resistance value of the resistor 33 and the resistance value of the phototransistor. By dividing the voltage, the integration signal V3a described above is generated at the collector terminal of the phototransistor.

  The voltage generation circuit 34 receives and amplifies the integration signal V3a to generate a voltage signal V4 (that is, a reference voltage) and applies it to the guard electrode 21. In this case, the voltage generation circuit 34 forms a feedback loop together with the guard electrode 21, the detection electrode 22, the current-voltage conversion circuit 23, the integration circuit 24, the drive circuit 25, and the photocoupler 26 of the floating circuit unit 2, thereby generating the potential difference Vdi. The voltage signal V4 is generated by performing an amplification operation to amplify the integration signal V3a so as to decrease. In this example, as an example, the voltage generation circuit 34 includes an AC amplifier circuit 34a, a phase compensation circuit 34b, and a booster circuit 34c. Here, the AC amplification circuit 34a generates the voltage signal V4a by inputting and amplifying the integration signal V3a. In this case, the AC amplifier circuit 34a generates a voltage signal V4a in which the absolute value of the voltage value changes in accordance with the increase / decrease of the absolute value of the voltage value of the integration signal V3a by an amplification operation. The phase compensation circuit 34b receives the voltage signal V4a, adjusts its phase, and outputs it as the voltage signal V4b in order to stabilize the feedback control operation (prevent oscillation). The booster circuit 34c is configured by using a booster transformer as an example, and generates a voltage signal V4 and guards it by boosting the voltage signal V4b by a predetermined magnification (by increasing the absolute without changing the polarity). Applied to the electrode 21. The voltmeter 35 detects (measures) the effective value of the voltage signal V4 and outputs it (displayed on its own display unit (not shown) as an example).

  Next, the detection operation (measurement operation) for the AC voltage V1 of the detection target body 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 22 faces the detection target body 4 in a non-contact state. Thereby, as shown in FIG. 1, the capacitance C <b> 0 is formed between the detection electrode 22 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 22 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 them 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 of the guard electrode 21 (voltage of the voltage signal V4) are greatly different (when the potential difference Vdi is large), the current-voltage conversion circuit. An inexpensive product with a low input withstand voltage can be used for the first operational amplifier 23c constituting the circuit 23. Also in this configuration, the destruction of the first operational amplifier 23c due to the potential difference Vdi is avoided.

  Next, in the activated state of the voltage detection device 1, when the potential difference Vdi between the AC voltage V1 of the detection object 4 and the voltage of the guard electrode 21 (reference voltage, voltage of the voltage signal V4) increases (for example, AC When the potential difference Vdi is increased due to the rise of the voltage V1, the amount of current of the current signal I flowing (inflowing) from the detection object 4 into the current-voltage conversion circuit 23 via the detection electrode 22 increases. To do. In this case, the current-voltage conversion circuit 23 reduces the voltage value of the output detection voltage signal V2. In the integrating circuit 24, the current flowing from the output terminal of the second operational amplifier 24d to the inverting input terminal via the capacitor 24c increases due to the decrease in the detection voltage signal V2. For this reason, the integration circuit 24 increases the voltage of the integration signal V3. Further, the transistor 25b of the drive circuit 25 shifts to a deep ON state as the voltage of the integration signal V3 increases. Thereby, in the photocoupler 26, the current flowing through the light emitting diode increases, and the resistance of the phototransistor decreases. Therefore, the voltage value of the integrated signal V3a generated by dividing the potential difference (Vdd−Vss) between the resistance value of the resistor 33 and the resistance value of the phototransistor decreases. The voltage generation circuit 34 increases the voltage value of the generated voltage signal V4 based on the integration signal V3a. In this voltage detection apparatus 1, the current-voltage conversion circuit 23, the integration circuit 24, the drive circuit 25, the photocoupler 26, and the main body circuit unit 3 that form the feedback loop in this way are used to increase the AC voltage V <b> 1 of the detection object 4. Is detected and a feedback control operation for increasing the voltage value of the voltage signal V4 is executed, thereby causing the voltage of the guard electrode 21 (the voltage of the voltage signal V4) to follow the AC voltage V1.

  Further, when the potential difference Vdi increases due to the decrease in the AC voltage V1, the amount of current of the current signal I that flows out (flows out) from the current-voltage conversion circuit 23 to the detection target body 4 through the detection electrode 22 increases. At this time, the current-voltage conversion circuit 23 or the like constituting the feedback loop performs an operation opposite to the above-described feedback control operation, and decreases the voltage of the voltage signal V4, whereby the voltage (voltage) of the guard electrode 21 is reduced. The voltage of the signal V4) is made to follow the AC voltage V1. Thus, in the voltage detection device 1, the feedback control operation for causing the voltage of the guard electrode 21 (the voltage of the voltage signal V4) to follow the AC voltage V1 is executed in a short time, and the voltage of the guard electrode 21 (first calculation). Due to the virtual short-circuit of the amplifier 23c, the voltage of the detection electrode 22) is matched with the AC voltage V1. The voltmeter 35 measures (detects) and displays the effective value (reference voltage, voltage of the guard electrode 21) of the voltage signal V4 in real time. Therefore, by observing the numerical value displayed on the voltmeter 35, the AC voltage V1 of the detection object 4 is detected (measured).

  As described above, in the voltage detection device 1, the capacitance C 0 and the detection formed between the detection target body 4 and the detection electrode 22 in a state where the detection electrode 22 is disposed to face the detection target body 4. Current signal I flowing between detection object 4 and current-voltage conversion circuit 23 at a current value corresponding to the AC potential difference between AC voltage V1 and voltage signal V4 (reference voltage) via electrode 22 is a current-voltage conversion circuit. 23, the detection voltage signal V2 is converted into a detection voltage signal V2 (specifically, a current flowing based on a potential difference between the detection voltage signal V2 and the reference voltage) is integrated by the integration circuit 24, and the detection electrode 22 An integrated signal V3 whose amplitude changes according to the potential difference Vdi between the voltage (voltage of the guard electrode 21) and the AC voltage V1 of the detection object 4 is generated, and the integrated signal V3 is electrically isolated using the photocoupler 26. Was converted to the integrated signal V3a, the voltage generating circuit 34 generates a voltage signal V4 is applied to the guard electrode 21 on the basis of this integrated signal V3a.

  Therefore, according to the voltage detection device 1, since the capacitance value of the capacitance C0 is generally extremely small (for example, about several pF to several tens pF), the impedance between the detection object 4 and the detection electrode 22 is large. Can be set to a sufficiently large value (several MΩ), so that the input impedance of the current-voltage conversion circuit 23 can be set to a relatively small value. Even if an inexpensive product with low input withstand voltage is used for the CV current-voltage conversion circuit 23, specifically, an inexpensive product with low input withstand voltage is used for the first operational amplifier 23c constituting the current-voltage conversion circuit 23. In addition, it is possible to avoid the destruction of the first operational amplifier 23c due to the potential difference Vdi.

  Further, according to the voltage detection device 1, the use of the photocoupler 26 as the insulation circuit makes it possible to easily electrically insulate (separate) the current-voltage conversion circuit 23 and the subsequent circuit from each other at any part. )be able to. Further, since the frequency characteristics of the photocoupler 26 are good over a wide frequency range, the AC voltage V1 of the detection target body 4 over the wide frequency range can be detected (measured) with high accuracy. Note that an insulating circuit can be configured by using a transformer (for example, a pulse transformer) in place of the optical insulating element such as the photocoupler 26, or the insulating circuit can be configured by connecting the photocoupler 26 and the transformer in parallel. You can also. In this configuration, the primary winding of the transformer functions as a primary circuit of the insulation circuit, and the secondary winding functions as a secondary circuit. In this case, in the former configuration, since the transformer generally has good frequency characteristics in a higher frequency range than the photocoupler 26, when the frequency of the AC voltage V1 is limited to a high frequency, the transformer is By using it, the AC voltage V1 can be detected (measured) with high accuracy. In the latter configuration, the photocoupler 26 mainly operates on the low frequency side and the transformer mainly operates on the high frequency side, so that the frequency characteristics of the insulating circuit can be widened, resulting in a wider frequency range. The AC voltage V1 of the detection object 4 over the range can be detected (measured) with high accuracy.

  Further, according to the voltage detection device 1, at least a circuit between the circuit subsequent to the detection electrode 22 and the primary side circuit of the insulation circuit (photocoupler 26), in this example, a current-voltage conversion circuit 23, an integration circuit 24, Since the drive circuit 25 and the photocoupler 26 are accommodated in the guard electrode 21 and covered with the guard electrode 21, the influence of the electric field from the outside can be made less susceptible to the circuit. The detection accuracy (measurement accuracy) of V1 can be improved.

  Further, according to the voltage detection device 1, the detection electrode 22 is in the guard electrode 21 so as not to protrude from the opening 21 a (non-projecting state) at a position facing the opening 21 a formed in the guard electrode 21. Since the detection electrode 22 can be made less susceptible to the influence of an external electric field, the detection accuracy (measurement accuracy) of the AC voltage V1 can be further improved.

  In addition, according to the voltage detection device 1, the entire surface of the detection electrode 22 facing the detection target body 4 is covered with the insulating layer 21 b as an insulator, so that the detection target body 4 and the detection electrode 22 are covered. A short circuit can be reliably prevented.

  In addition, this invention is not limited to said structure. In the voltage detection device 1 described above, a state in the guard electrode 21 that does not protrude from the opening 21a at a position facing the opening 21a formed in the guard electrode 21 (a state in which it is recessed from the surface of the guard electrode 21). However, when the influence of the electric field from the outside is small, the detection electrode 22 is almost flush with the guard electrode 21 or partially protrudes into the opening 21a. It is also possible to adopt a configuration in which the detection electrode 22 is attached to the outer surface of the guard electrode 21 so as to cover the opening 21a. In any configuration, it goes without saying that the detection electrode 22 and the guard electrode 21 are electrically insulated. Further, the configuration in which the entire guard electrode 21 is covered with the insulating layer 21b has been described above, but the configuration in which only the detection electrode 22 that is highly likely to contact the detection target body 4 is covered with the insulating layer 21b and the other portions are not covered is adopted. You can also

  In the case where main power supply circuit 31 is configured to generate positive voltage Vdd and negative voltage Vss by receiving supply of AC voltage from the outside, converter 32 receives positive voltage Vdd and negative voltage Vss and receives positive voltage Vss. Instead of a configuration for generating Vf + and negative voltage Vf− (a configuration for generating DC from DC), a positive voltage Vf + and a negative voltage Vf− are generated by receiving an AC voltage from the outside in the same manner as the main power supply circuit 31. It can also be configured. Even in this configuration (a configuration in which DC is generated from AC), the converter 32 uses an transformer in the same manner as in the above-described example, so that the secondary side is electrically insulated from the primary side. Configure as.

  Further, for example, an example is adopted in which a photocoupler 26 is disposed in the subsequent stage of the integration circuit 24 together with the drive circuit 25 and the integration signal V3 is converted into an integration signal V3a that is electrically insulated from the integration signal V3. As described above, the photocoupler 26 and the drive circuit 25 are disposed in the previous stage of the integration circuit 24, that is, between the current-voltage conversion circuit 23 and the integration circuit 24, and the detection voltage signal V2 is electrically connected to the detection voltage signal V2. It is also possible to adopt a configuration that converts the detected voltage signal into a new insulated detection voltage signal and outputs it to the integrating circuit 24. In addition, a configuration in which circuits other than the drive circuit 25, the photocoupler 26, and the integration circuit 24 are appropriately added between the main body circuit unit 3 and the voltage generation circuit 34 may be employed. However, when this configuration is employed, The isolation circuit (optical isolation element or transformer) inputs a signal generated in any circuit existing between the current-voltage conversion circuit 23 and the voltage generation circuit 34, and electrically isolates the input signal. However, it is inserted in the path of this signal so as to output it. Further, as described above, the portion to be covered by the guard electrode 21 is from the circuit after the detection electrode 22 (current / voltage conversion circuit 23 in this example) to the primary circuit of the photocoupler 26, that is, the primary circuit of the insulation circuit. It becomes a circuit. For this reason, when the position of the insulation circuit is changed as described above, the circuit to be covered with the guard electrode 21 changes according to the arrangement of the insulation circuit. For example, in the configuration in which the photocoupler 26 that is an insulating circuit is disposed in front of the integration circuit 24 together with the drive circuit 25, the primary side circuit of the current-voltage conversion circuit 23, the drive circuit 25, and the photocoupler 26 is covered with the guard electrode 21. And In addition to the configuration in which the effective value of the voltage signal V4 is detected (measured) by the voltmeter 35 and output, or instead of this configuration, for example, a DSP (samples the voltage signal V4 and displays the waveform on the display unit). A configuration including a digital signal processing unit) can also be employed.

  Further, the current-voltage conversion unit CV can be realized by adopting the configuration shown in FIG. 4 or 5 instead of the above configuration. Specifically, in the current-voltage conversion unit CV shown in FIG. 4, the current-voltage conversion circuit 23 includes a first operational amplifier 23c configured as a voltage follower, and a non-inverting input terminal and the guard electrode 21 of the first operational amplifier 23c. It is composed of a resistor 23d disposed between (reference voltage section). As a result, the current signal I can be converted into the voltage V5 by the resistor 23d, and the voltage V5 (voltage generated across the resistor 23d) is used as a buffer (amplifier with a magnification of 1). The amplifier 23c (amplifier) outputs it as the detection voltage signal V2. In the current-voltage conversion unit CV shown in FIG. 5, the current-voltage conversion circuit 23 is arranged between the first operational amplifier 23c, the non-inverting input terminal of the first operational amplifier 23c, and the guard electrode 21 (reference voltage unit). The resistor 23d, the resistor 23e disposed between the inverting input terminal of the first operational amplifier 23c and the guard electrode 21, and the feedback circuit disposed between the output terminal and the inverting input terminal of the first operational amplifier 23c. It comprises a resistor 23b. Thus, the current signal I can be converted into the voltage V5 by the resistor 23d, and this voltage V5 (voltage generated across the resistor 23d) is detected by the first operational amplifier 23c (amplifier) that functions as a non-inverting amplifier. Output as voltage signal V2. Therefore, the voltage detection device 1 that employs the current-voltage conversion unit CV having the configuration shown in FIGS. 4 and 5 also has the same operational effects as the voltage detection device 1 that employs the current-voltage conversion unit CV that has the configuration shown in FIG. be able to.

  Further, the example in which the current-voltage conversion circuit 23 and the integration circuit 24 configure the current-voltage conversion unit CV has been described above, but the current-voltage conversion unit CV may be configured by one integration circuit 27 as shown in FIG. it can. The integration circuit 27 has a function of a current-voltage conversion circuit and a function of an integration circuit. For example, the integration circuit 27 has a configuration of the current-voltage conversion circuit 23 shown in FIG. 1 as a basic configuration, and a capacitor 27a is connected in parallel to the resistor 23b. Configured. In this case, as an example, the capacitor 27a is composed of a capacitor of about 0.01 μF, and the resistor 23b is composed of a resistor having a high resistance value of about 1 MΩ, for example. For this reason, in this integration circuit 27, the current signal I mainly flows through the capacitor 27a, whereby the integration operation is performed simultaneously with the current-voltage conversion operation, and the AC voltage V1 of the detection object 4 and the voltage of the guard electrode 21 (reference). An integrated signal V3 whose voltage value changes in proportion to the potential difference Vdi from the voltage is generated. Therefore, even in the voltage detection device 1 that employs the current-voltage conversion unit CV having the configuration shown in FIG. 6, the same effects as the voltage detection device 1 that employs the current-voltage conversion unit CV that has the configuration shown in FIG. 1 can be achieved. it can. In this integrating circuit 27, the amount of feedback in the vicinity of the direct current is remarkably reduced only by the capacitor 27a, the gain becomes extremely large, and the first operational amplifier 23c may be saturated by the offset due to the bias current. Functions as a suppressor of a decrease in dynamic range. In addition, although the non-inverting input terminal of the first operational amplifier 23c and the guard electrode 21 are connected via the resistor 23a, a configuration in which they are directly connected can also be employed.

  Further, voltage detection adopting a configuration in which the integration signal V3 that is an analog signal generated in the floating circuit portion 2 is output to the main body circuit portion 3 as an integration signal V3a that is an analog signal electrically insulated from the integration signal V3. Although the apparatus 1 has been described above, a configuration in which the integration signal V3 is converted into a digital signal and output to the main body circuit unit 3 may be employed. Hereinafter, voltage detection devices 1A and 1B employing this configuration will be described with reference to FIGS. In addition, about the same structure as the voltage detection apparatus 1 mentioned above, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

  First, the voltage detection apparatus 1A will be described. As shown in FIG. 7, the voltage detection device 1A includes a floating circuit portion 2A and a main body circuit portion 3A, and is configured to be capable of detecting (measurable) the AC voltage V1 generated in the detection target body 4 without contact. Yes. As shown in the figure, the floating circuit unit 2A includes a guard electrode 21, a detection electrode 22, a current-voltage conversion unit CV, a buffer amplifier 28, an A / D conversion circuit 29, and an insulation circuit 26A. The current-voltage conversion unit CV may be configured by any of the circuits shown in FIGS. 1, 4, 5, and 6, but in this example, the integration circuit 27 shown in FIG. 6 is adopted as an example. It is configured. The buffer amplifier 28 is composed of an amplifier having a high input impedance and a low output impedance, and receives the integration signal V3 output from the integration circuit 27 and outputs it with a low impedance. The A / D conversion circuit 29 is composed of an A / D converter, samples the integration signal V3 at a predetermined sampling period (a period sufficiently short with respect to the period of the AC voltage V1), and generates a voltage waveform of the integration signal V3. Is converted to digital data D1 and output. The insulating circuit 26A is configured using a digital isolator (hereinafter also referred to as “digital isolator 26A”). The digital isolator 26A is a device that electrically insulates and transmits a digital signal between input and output. For example, the digital isolator 26A is configured using an optically isolated isolator such as a phototransistor or a photocoupler, or a magnetically coupled isolator. There is something constructed using. In this example, the digital isolator 26A converts the digital data D1 output from the A / D conversion circuit 29 into electrically isolated digital data D1a and outputs the digital data D1a to the main body circuit unit 3A via the wiring W1.

  As shown in FIG. 7, the main body circuit unit 3A includes a main power supply circuit 31, a DC / DC converter 32, a voltage generation circuit 34A, and a voltmeter 35 as an example. The voltage generation circuit 34A includes a processing unit 34d, a D / A conversion circuit 34e, and a booster circuit 34c. The processing unit 34d is composed of a CPU and a DSP (digital signal processing unit), and performs the amplification processing and the phase adjustment processing that are performed in the AC amplification circuit 34a and the phase compensation circuit 34b of the voltage detection device 1 described above. The input digital data D1a is executed by digital processing and output as new digital data D2. The D / A conversion circuit 34e receives the digital data D2 and converts it into an analog signal, thereby generating and outputting the same signal as the voltage signal V4b generated by the phase compensation circuit 34b. The booster circuit 34c boosts the voltage signal V4b at a predetermined magnification to generate the voltage signal V4 and apply it to the guard electrode 21.

  Therefore, the voltage detection device 1A can detect (measure) the AC voltage V1 of the detection target body 4 via the electrostatic capacitance C0 having a generally extremely small capacitance value, similarly to the voltage detection device 1. Therefore, even if an inexpensive product with a low input withstand voltage is used for the first operational amplifier 23c constituting the current-voltage conversion circuit 23 of the current-voltage conversion unit CV, destruction of the first operational amplifier 23c due to the potential difference Vdi is avoided. Can do. In the voltage detection device 1A, the digital isolator 26A is used as an insulation circuit to convert the integration signal V3 output from the integration circuit 27 into digital data D1, and the digital data D1 is electrically insulated. Since the digital data D1a is output to the main body circuit unit 3A, the information (voltage waveform) about the integration signal V3 is changed with respect to the temperature of the transmission line (wiring W1) and changes over time as compared with the configuration in which the integration signal V3 is output as an analog signal. As a result, the detection accuracy (measurement accuracy) of the AC voltage V1 can be improved.

  Although not shown, the voltage generation circuit is configured by a D / A conversion circuit 34e and components of the voltage generation circuit 34 of the voltage detection device 1 (an AC amplification circuit 34a, a phase compensation circuit 34b, and a booster circuit 34c). Then, the D / A conversion circuit 34e directly inputs the digital data D1a and converts it into an analog signal, and the AC amplification circuit 34a, the phase compensation circuit 34b, and the booster circuit 34c are similar to the voltage detection device 1 for this analog signal. It is also possible to adopt a configuration that operates to generate the voltage signal V4.

  Next, the voltage detection apparatus 1B will be described. In addition, about the same structure as the voltage detection apparatuses 1 and 1A, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

  As shown in FIG. 8, the voltage detection device 1B includes a floating circuit portion 2B and a main body circuit portion 3B, and is configured to be able to detect (measure) the AC voltage V1 generated in the detection target body 4 without contact. Yes. As shown in the figure, the floating circuit unit 2B includes a guard electrode 21, a detection electrode 22, a current-voltage conversion unit CV, a buffer amplifier 28, a PWM signal generation circuit 29A, and an insulation circuit 26A (digital isolator 26A). The current-voltage conversion unit CV is configured by using the integration circuit 27 shown in FIG. 6 as an example, similarly to the voltage detection device 1A. The buffer amplifier 28 receives the integration signal V3 and outputs it with a low impedance. The PWM signal generation circuit 29A performs pulse width modulation on the input integration signal V3, thereby changing the pulse width according to the voltage value of the integration signal V3 (binary signal, high level and high level). A signal Sp having a Low level defined at a predetermined voltage value is generated and output. As an example in this example, the PWM signal generation circuit 29A includes a triangular wave generation circuit that generates a triangular wave having a constant period, and a comparator that generates a pulse signal Sp by comparing the triangular wave and the input integration signal V3 (both shown in FIG. (Not shown). In this example, as an example, the PWM signal generation circuit 29A converts the pulse signal Sp, which has a pulse width that decreases when the voltage value of the integration signal V3 increases, and increases when the voltage value of the integration signal V3 decreases, into a triangular wave. Generate in the same cycle. The digital isolator 26A converts the pulse signal Sp into an electrically isolated pulse signal Spa and outputs the pulse signal Spa to the main body circuit unit 3B via the wiring W1.

  As shown in FIG. 8, the main body circuit unit 3B includes a main power supply circuit 31, a DC / DC converter 32, a voltage generation circuit 34B, and a voltmeter 35 as an example. As an example in this example, the voltage generation circuit 34B includes a drive circuit 34f, a primary winding, and a secondary winding, each of which includes a switching element that is controlled to be turned on and off by a pulse signal Spa, as shown in FIG. A step-up transformer 34g having a primary winding driven by a drive circuit 34f, and a DC conversion circuit 34h that generates a voltage signal V4 by rectifying and smoothing an AC voltage induced in the secondary winding of the step-up transformer 34g. And is configured as a booster circuit. With this configuration, when the pulse width of the pulse signal Spa decreases, the voltage generation circuit 34B controls the switching element to have a short ON period, thereby lowering the voltage signal V4 and increasing the pulse width of the pulse signal Spa. The voltage signal V4 is raised by controlling the ON period of the switching element to be long. The voltage generation circuit 34B applies the voltage signal V4 to the guard electrode 21.

  Therefore, this voltage detection device 1B also detects (measures) the AC voltage V1 of the detection object 4 via the electrostatic capacitance C0, which is generally extremely small in capacitance value, in the same manner as the voltage detection devices 1 and 1A. Therefore, even if an inexpensive product with a low input withstand voltage is used for the first operational amplifier 23c constituting the integrating circuit 27 of the current-voltage converter CV, the destruction of the first operational amplifier 23c due to the potential difference Vdi is avoided. Can do. In the voltage detection device 1B, similarly to the voltage detection device 1A, the digital isolator 26A is used as an insulation circuit, and the integration signal V3 output from the integration circuit 27 is converted into a pulse signal Sp that is a binarized signal. In addition to the conversion, the pulse signal Sp is electrically insulated and output to the main body circuit unit 3B as the pulse signal Spa. Therefore, the information about the integration signal V3 (as compared with the configuration in which the integration signal V3 is output as an analog signal ( Voltage waveform) can be transmitted to the main body circuit unit 3B with high accuracy without being affected by the temperature of the transmission line (wiring W1) or changes over time, and as a result, the detection accuracy (measurement accuracy) of the AC voltage V1 is improved. be able to.

  Next, a line voltage detection device 51 using a plurality of the voltage detection device 1, the voltage detection device 1A, or the voltage detection device 1B will be described. Note that the line voltage detection device 51 can be configured by only the voltage detection device 1, only the voltage detection device 1A, or only the voltage detection device 1B, or the voltage detection device 1, the voltage detection device 1A, and the voltage detection device. Although two types of devices selected from 1B and all types of devices can be mixed, an example in which only the voltage detection device 1 is configured will be described below as an example.

  First, the line voltage detection device 51 will be described with reference to the drawings. In the following, an example of detecting (measuring) 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 will be described. .

  For example, as shown in FIG. 9, the line voltage detecting device 51 corresponds to the same number (three) of the electric circuits R, S, T as the number of the electric circuits R, S, T (hereinafter referred to as the electric circuits 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 (measured) in a non-contact manner.

  As shown in FIG. 9, each voltage detection device 1 includes the floating circuit unit 2 and the main body circuit unit 3 and is configured in the same manner, and each AC circuit R, S, T is used as a detection target, and the alternating currents are detected. The voltage signal V4 is made to coincide with the voltages Vr, Vs, and Vt (detection target AC voltage) by performing a feedback control operation. In each of the voltage detection devices 1r, 1s, and 1t of this example, the voltmeter 35 outputs voltage data Dva, Dvb, and Dvc indicating the waveform of the detected (measured) voltage signal V4. Hereinafter, the voltage data Dva, Dvb, and Dvc are also referred to as “voltage data Dv” unless particularly distinguished.

  The calculation unit 52 includes a calculation circuit including a CPU and a memory (both not shown), and calculates (calculates) a line voltage based on the voltage data Dv output from each voltage detection device 1. A line voltage calculation process is executed. 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. In addition, the main body circuit units 3 are connected to each other's grounds G1 as described later. In addition, the calculation unit 52 and the display unit 53 are supplied with the positive voltage Vdd and the negative voltage Vss from the main power supply circuit 31 included in any one of the three main body circuit units 3. Operate. With this configuration, each floating circuit unit 2, each main circuit unit 3, calculation unit 52, and display unit 53 are in a state of floating from the ground.

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

  First, at the time of detection (measurement), as shown in FIG. 9, in order to detect (measure) the AC voltage Vr 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 22 thereof. To the corresponding electric circuit R. Similarly, with respect to the other voltage detection devices 1s and 1t, in order to detect (measure) the AC voltages Vs and Vt of the electric circuits S and T, the detection electrodes 22 of the respective floating circuit portions 2 are connected to the corresponding electric circuits S and T. Make them face each other. As a result, a capacitance C0 (see FIG. 1) is formed between each detection electrode 22 and each of the electric paths R, S, and T. In this case, the capacitance value of each electrostatic capacitance C0 changes in inverse proportion to the distance between each detection electrode 22 and the core wire of the electric circuits R, S, T. It becomes constant (does not change) under certain environmental conditions. Further, since the capacitance value of the capacitance C0 is generally extremely small (for example, about several pF to several tens of pF), the impedance between the electric circuits R, S, T and each detection electrode 22 is a sufficiently large value ( Several MΩ). Thereby, also in the line voltage detection apparatus 51, even if the electric potential difference Vdi between each electric circuit R, S, T and each corresponding detection electrode 22 is large, the alternating voltage of electric circuit R, S, T The situation where the first operational amplifier 23c of each voltage detection device 1 is destroyed is prevented by Vr, Vs, and Vt. Further, by connecting (short-circuiting) the grounds G1 of the respective voltage detection devices 1, the potential of the ground G1 of each voltage detection device 1 is made common.

  Next, in the activated state of the line voltage detection device 51, in the voltage detection device 1r, the current-voltage conversion circuit 23, the integration circuit 24, the drive circuit 25, the photocoupler 26, and the main body circuit unit 3 constituting the feedback loop are connected to the electric circuit R. The voltage of the guard electrode 21 (which is also the voltage of the voltage signal V4 and the voltage of the detection electrode 22) is obtained by executing a feedback control operation that changes the voltage value of the voltage signal V4 in accordance with the change in the AC voltage Vr. Follows the AC voltage Vr. Also in the other voltage detection devices 1s and 1t, the current-voltage conversion circuit 23, the integration circuit 24, the drive circuit 25, the photocoupler 26, and the main circuit unit 3 constituting the feedback loop are connected to the AC voltage Vs of the electric circuits S and T, By executing a feedback control operation that changes the voltage value of the voltage signal V4 in accordance with the change in Vt, the voltage of each guard electrode 21 (which is also the voltage of the voltage signal V4 and the voltage of the detection electrode 22) is AC. Follow the voltages Vs and Vt. In addition, the voltmeter 35 of each voltage detection device 1 is voltage data Dva, Dvb, voltage indicating the voltage of the detected (measured) voltage signal V4, that is, the waveform of the AC voltage Vr, Vs, Vt of each electric circuit R, S, T. Dvc is output continuously.

  The calculation unit 52 inputs each voltage 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 (calculates) a line voltage Vrs between the electric circuits R and S by calculating a differential voltage between the voltage data Dva and Dvb. Similarly, the calculation unit 52 calculates (calculates) the line voltage Vst between the electric circuits S and T by calculating the differential voltage between the voltage data Dvb and Dvc, and the voltage data Dva and Dvc. Is obtained (detected) by calculating the line voltage Vrt between the electric circuits R and T. In this case, as described above, each voltage detection device 1 detects (measures) the AC voltages Vr, Vs, and Vt of the electric circuits R, S, and T with the common ground G1 as a reference. Even if it is such a potential, the line voltages Vrs, Vst, Vrt are accurately obtained (calculated) by calculating the differential voltage of the AC voltages Vr, Vs, Vt. The calculation unit 52 causes the display unit 53 to display the calculated line voltages Vrs, Vst, Vrt.

  As described above, according to the line voltage detection device 51, the use of the voltage detection device 1 allows the first operational amplifier 23c constituting the current-voltage conversion circuit 23 in each voltage detection device 1 to have a low input withstand voltage and is inexpensive. Even if a simple product is used, the destruction of the first operational amplifier 23c due to the potential difference Vdi can be avoided, so that the line voltages Vrs, Vst, Vrt can be detected (measured) while reducing the device cost. it can.

  In addition, this invention is not limited to said structure. For example, the example in which a plurality of the voltage detection devices 1 having the same configuration each including the main power supply circuit 31 and the converter 32 is used has been described above. It is also possible to employ a configuration in which the positive voltage Vdd, the negative voltage Vss, the positive voltage Vf +, and the negative voltage Vf− are supplied from the voltage detection device 1 to the remaining voltage detection devices 1.

1, 1A, 1B, 1r, 1s, 1t Voltage detection device 2, 2A, 2B Floating circuit section 3, 3A, 3B Body circuit section 4 Object to be detected 21 Guard electrode 21a Opening 21b Insulating layer 22 Detection electrode 23 Current-voltage conversion Circuit 23c First operational amplifier 23d Resistance 24 Integration circuit 26 Photocoupler 26A Digital isolator 34, 34A, 34B Voltage generation circuit 51 Line voltage detection device 52 Calculation unit CV Current voltage conversion unit I Current signal R, S, T Electric circuit V1, Vr, Vs, Vt AC voltage V2 Detection voltage signal V3, V3a Integration signal Vdi Potential difference Vrs, Vrt, Vst Line voltage

Claims (9)

A voltage detection device for detecting a detection target alternating voltage generated in a detection target body,
A detection electrode disposed to face the detection object;
A first input terminal defined by a reference voltage, a second input terminal connected directly or indirectly to the detection electrode, and a feedback circuit connected to the detection electrode and the second input terminal. A current-voltage conversion circuit having an operational amplifier for converting a detection current flowing at a current value corresponding to an AC potential difference between the detection target AC voltage and the reference voltage into a detection voltage signal and outputting the detection voltage signal in a path including
An integration circuit that integrates the detection voltage signal and outputs an integration signal whose amplitude changes according to the potential difference;
An isolation circuit that is disposed in a preceding stage or a subsequent stage of the integration circuit, and inputs and electrically insulates and outputs one of the detection voltage signal and the integration signal;
A voltage detection device comprising: a voltage generation circuit that amplifies a signal based on the integration signal so as to reduce the potential difference and generates the reference voltage. A voltage detection device for detecting a detection target alternating voltage generated in a detection target body,
A detection electrode disposed to face the detection object;
A detection unit that is disposed between the detection electrode and a reference voltage portion and converts a detection current flowing at a current value corresponding to an AC potential difference between the detection target AC voltage and the reference voltage into a voltage signal. And a current-voltage conversion circuit having an amplifier that impedance-converts the voltage signal and outputs it as a detection voltage signal;
An integration circuit that integrates the detection voltage signal and outputs an integration signal whose amplitude changes according to the potential difference;
An isolation circuit that is disposed in a preceding stage or a subsequent stage of the integration circuit, and inputs and electrically insulates and outputs one of the detection voltage signal and the integration signal;
A voltage detection device comprising: a voltage generation circuit that amplifies a signal based on the integration signal so as to reduce the potential difference and generates the reference voltage. A voltage detection device for detecting a detection target alternating voltage generated in a detection target body,
A detection electrode disposed to face the detection object;
A first input terminal is defined as a reference voltage, a second input terminal is connected directly or indirectly to the detection electrode, and the detection electrode and a feedback circuit connected to the second input terminal are provided. An operational amplifier that integrates a detection current flowing at a current value corresponding to an AC potential difference between the detection target AC voltage and the reference voltage in a path including the output, and outputs an integration signal whose amplitude changes according to the potential difference An integrating circuit having
An insulating circuit that inputs the integration signal and electrically insulates and outputs the integrated signal;
A voltage detection device comprising: a voltage generation circuit that amplifies a signal based on the integration signal so as to reduce the potential difference and generates the reference voltage.   The voltage detection device according to claim 1, wherein the insulation circuit includes an optical insulation element and / or a transformer.   The voltage detection device according to claim 1, wherein the insulation circuit includes a digital isolator.   6. The device according to claim 1, further comprising a guard electrode defined by the reference voltage, wherein a space from a circuit subsequent to the detection electrode to a primary circuit of the insulating circuit is covered by the guard electrode. Voltage detection device. An opening is formed in the guard electrode;
The voltage detection device according to claim 6, wherein the detection electrode is disposed at a position facing the opening in the guard electrode so as not to protrude from the opening.   The voltage detection apparatus according to claim 1, further comprising an insulator that covers an entire surface of the detection electrode that faces the detection target body. The plurality of corresponding electric circuits as the detection object are configured so 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. A voltage detection device according to any one of the above,
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.

Images