JP2010256125A - Voltage detection apparatus and line voltage detecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wideband voltage detection device capable of also detecting a rapidly changing voltage of a detection object. <P>SOLUTION: The voltage detection device 1 for detecting an AC voltage V1 generated in the detection object 4 includes: a detection electrode 22, disposed opposite to the detection object 4 and coupled capacitively with the detection object 4; a bootstrap circuit 27 operated by a floating power source generated, based on a reference voltage (the voltage of a voltage signal V4) for outputting a detection voltage signal V2, whose amplitude is changed corresponding to an AC potential difference Vdi between an AC voltage V1 and the reference voltage; a photocoupler 26 for electrically insulating the detection voltage signal V2 and outputting it as a detection voltage signal V2a; and a voltage-generating circuit 34 for generating a voltage signal V4, by amplifying the detection voltage signal V2a so that the potential difference Vdi is reduced. <P>COPYRIGHT: (C)2011,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 object to be detected, the voltage applied to the metal needle is controlled by the feedback circuit so that the field emission current or the tunnel current is 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. In this case, this voltage detection device employs a configuration in which a current-voltage converter is used as a part of the Fordback circuit, and a field emission current or a tunnel current is converted into a voltage signal by the current-voltage converter.

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 device, the metal needle to which the output of the feedback circuit is applied is connected to the current-voltage converter, and generally the input impedance of the current-voltage converter is a low value. The load is heavy. Therefore, in this voltage detection device, when the change in the potential of the detection object is slow (when the fluctuation period is long) due to the heavy load on the feedback circuit, the voltage applied to the metal needle Can follow the fluctuation of the potential of the detection object, but when the change of the potential of the detection object is fast (when the fluctuation cycle is short), the voltage applied to the metal needle is There is a problem to be solved that it is difficult to follow the fluctuation.

  The present invention has been made to solve the above-described problems, and has as its main object to provide a wide-band voltage detection device that can detect even a voltage whose detection object changes rapidly. 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 a detection object and a floating power source that is generated with reference voltage as a reference, and that changes in amplitude according to an AC potential difference between the detection object AC voltage and the reference voltage A bootstrap circuit that outputs a signal; an insulation circuit that inputs the detection signal and electrically insulates and outputs it as an insulation detection signal; and amplifies the insulation detection signal so as to reduce the potential difference, and the reference voltage And a voltage generation circuit for generating.

  The voltage detection device according to claim 2 is the voltage detection device according to claim 1, wherein the insulating circuit includes an optical insulating element and / or a transformer.

  The voltage detection device according to claim 3 is the voltage detection device according to claim 1 or 2, further comprising a guard electrode defined by the reference voltage, wherein the bootstrap circuit and the primary circuit of the insulation circuit Covered by a guard electrode.

  The voltage detection device according to claim 4 is the voltage detection device according to claim 3, 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.

  A voltage detection device according to a fifth aspect is the voltage detection device according to any one of the first to fourth aspects, further comprising an insulator that covers the entire surface of the detection electrode facing the detection object.

  The line voltage detection device according to claim 6 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 5, each capable of being 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, the amplitude of the bootstrap circuit changes in accordance with the potential difference based on the potential difference between the AC voltage and the reference voltage in a state where the detection electrode is arranged to face the detection object. The detection signal is output, the insulation circuit electrically insulates this detection signal and outputs it as an insulation detection signal, and the voltage generation circuit amplifies the insulation detection signal to generate a reference voltage. In this voltage detection device, since the circuit connected to the detection electrode is a bootstrap circuit having an extremely high input impedance, the impedance of the detection electrode is maintained at a high impedance, and the entire floating circuit unit that becomes a load of the voltage generation circuit The impedance is also high impedance (the load of the voltage generation circuit is light).

  Therefore, according to this voltage detection device, the voltage generation circuit can satisfactorily follow the output reference voltage even with a detection target AC voltage having a short cycle (high frequency), resulting in a wide frequency band. It is possible to accurately detect the AC voltage to be detected over the entire range.

  According to the voltage detecting device of the second aspect, the bootstrap circuit and the main body circuit unit are easily electrically insulated by configuring the insulating circuit using the optical insulating element and / or the transformer ( Can be separated). In addition, when an optical insulating element is used, since the frequency characteristics are good over a wide frequency range, the AC voltage of the detection object over a wide frequency range can be detected with higher accuracy. 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, so the upper limit of the frequency band in which the detection target AC voltage can be detected. The frequency can be further increased. 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 further increase the detection accuracy of the detection target AC voltage over a wide frequency range.

  According to the voltage detection device of the third aspect, the primary side circuit of the bootstrap circuit and the insulating circuit are accommodated in the guard electrode, and these are covered with the guard electrode. As a result of making it difficult for these circuits to be affected, the detection accuracy of the detection target AC voltage can be improved.

  According to the voltage detection device of claim 4, 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.

  According to the voltage detection device of the fifth aspect, the entire surface of the detection electrode facing the detection target body is covered with the insulating material, thereby reliably preventing a short circuit between the detection target body and the detection electrode. be able to.

  Further, according to the line voltage detecting device of the sixth aspect, the use of the voltage detecting device having the bootstrap circuit makes it possible to accurately measure the AC voltage of each electric circuit over a wide frequency band. Since it can be detected well, each line voltage can be measured with high accuracy over a wide frequency band.

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. 7 is a circuit diagram showing another configuration of the bootstrap circuit 27. FIG. 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 type voltage detection device, and includes a floating circuit portion 2 and a main body circuit portion 3 as shown in FIG. 1, and an AC voltage V1 (detection target) generated in the detection target body 4. AC voltage) can be detected (measured) in a non-contact manner.

  The floating circuit unit 2 includes a guard electrode 21, a detection electrode 22, a bootstrap circuit 27, a drive circuit 25, and an insulation circuit 26, as shown in FIGS. 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). As an example, the boot electrode circuit 27, the drive circuit 25, and the photocoupler 26 are accommodated therein. ing. Thereby, the configuration from the bootstrap circuit 27 to the photocoupler 26 is covered with the guard electrode 21. The part to be covered with the guard electrode 21 may be from the bootstrap circuit 27 to the primary side circuit (light emitting diode described later) of the photocoupler 26. 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 bootstrap circuit 27 includes two operational amplifiers 27 a and two non-inverting input terminals of the operational amplifier 27 a that are connected in series with each other and the guard electrode 21. Resistors 27b and 27c, a capacitor 27d disposed between the inverting input terminal of the operational amplifier 27a and the connection point of the two resistors 27b and 27c, and disposed between the inverting input terminal and the output terminal of the operational amplifier 27a. The resistor 27e is provided. The detection electrode 22 is connected to the non-inverting input terminal of the operational amplifier 27a. In the bootstrap circuit 27, the operational amplifier 27a operates in response to the supply of a positive voltage Vf + and a negative voltage Vf−, which will be described later, and inputs the voltage generated at the detection electrode 22, and the AC voltage V1 of the detection object 4 is input. And a detection voltage signal (detection signal) V2 having a voltage corresponding to a potential difference Vdi between the voltage of the guard electrode 21 (reference voltage). In this case, the amplitude of the detection voltage signal V2 changes in proportion to the amplitude of the potential difference Vdi.

  The drive circuit 25 is arranged at the rear stage of the bootstrap circuit 27 together with the photocoupler 26. For example, the drive circuit 25 has a base terminal connected to the output terminal of the operational amplifier 27a via the input resistor 25a, a collector terminal connected to the photocoupler 26, and an emitter terminal connected to the negative voltage Vf−. A transistor (in this example, an NPN bipolar transistor as an example) 25b is used. 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 detection voltage signal V2 (substantially in proportion). To do. Therefore, the photocoupler 26 is coupled with a resistor 33 of the main body circuit unit 3 to be described later, and the detection voltage signal V2 input from the bootstrap circuit 27 is newly insulated from the detection voltage signal V2. It converts into a detection voltage signal (insulation detection signal) V2a. 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 detection voltage signal V2, 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. As a result of the voltage division, the detection voltage signal V2a described above is generated at the collector terminal of the phototransistor.

  The voltage generation circuit 34 receives and amplifies the detection voltage signal V <b> 2 a to generate a voltage signal V <b> 4 (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 bootstrap circuit 27, the drive circuit 25, and the photocoupler 26 of the floating circuit unit 2 to detect the potential difference Vdi. The voltage signal V4 is generated by performing an amplification operation for amplifying the voltage signal V2a. 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 detection voltage signal V2a. In this case, the AC amplifier circuit 34a generates the 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 detection voltage signal V2a by the 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. The capacitance value of the capacitance C0 is generally about several pF to several tens pF.

  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 increase in the voltage V1, the bootstrap circuit 27 increases the voltage value of the output detection voltage signal V2 in accordance with the increase in the potential difference Vdi. As the detection voltage signal V2 rises, the transistor 25b of the drive circuit 25 shifts to a deep on state. 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 detection voltage signal V2a 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 detection voltage signal V2a. In this voltage detection device 1, the bootstrap circuit 27, the drive circuit 25, the photocoupler 26, and the main body circuit unit 3 that constitute the feedback loop in this way detect an increase in the AC voltage V <b> 1 of the detection object 4, By executing a feedback control operation for increasing the voltage value of the voltage signal V4, the voltage of the guard electrode 21 (the voltage of the voltage signal V4) is made to follow the AC voltage V1.

  Further, when the potential difference Vdi increases due to the decrease in the AC voltage V1, the bootstrap circuit 27 and the like constituting the feedback loop perform an operation opposite to the above feedback control operation, and the voltage of the voltage signal V4 is increased. By reducing the voltage, the voltage of the guard electrode 21 (the voltage of the voltage signal V4) is made to follow the AC voltage V1. In this way, 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 (the operational amplifier 27a). (Which is also the voltage of the detection electrode 22) is made to coincide 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 this voltage detection device 1, the bootstrap circuit 27 is based on the potential difference Vdi between the AC voltage V <b> 1 and the voltage signal V <b> 4 (reference voltage) in a state where the detection electrode 22 is disposed facing the detection target body 4. Thus, a detection voltage signal (detection signal) V2 whose amplitude changes according to the potential difference Vdi is generated, and the photocoupler 26 detects the detection voltage signal (insulation detection signal) V2a electrically insulated from the detection voltage signal V2. The voltage generation circuit 34 generates a voltage signal V4 based on the detection voltage signal V2a and applies it to the guard electrode 21. In this voltage detection device 1, the circuit connected to the detection electrode 22 is the bootstrap circuit 27 having an extremely high input impedance, so that the impedance of the detection electrode 22 is maintained at a high impedance and the load of the voltage generation circuit 34 is increased. The impedance of the entire floating circuit unit 2 is also high (the load of the voltage generation circuit 34 is light).

  Therefore, according to the voltage detection device 1, the voltage generation circuit 34 can favorably follow the voltage value of the output voltage signal V4, even with a short cycle (high frequency) AC voltage V1. As a result, the AC voltage V1 can be accurately detected (measured) over a wide frequency band (in a wide band).

  Further, according to the voltage detection device 1, the use of the photocoupler 26 as an insulation circuit makes it possible to easily electrically insulate (separate) the floating circuit portion 2 and the main body circuit portion 3 from each other. 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, the frequency band in which the AC voltage V1 can be detected can be detected by using the transformer. The upper limit frequency can be further increased. 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 wide frequency range. It is possible to detect (measure) the AC voltage V <b> 1 of the detection target body 4 over more accurately.

  Further, according to the voltage detection device 1, the bootstrap circuit 27, the drive circuit 25, and the photocoupler 26 are accommodated in the guard electrode 21, and these are covered with the guard electrode 21. As a result, the detection accuracy of the AC voltage 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 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 the voltage detection device 1 described above, a state that does not protrude from the opening 21a (indented from the surface of the guard electrode 21) in the guard electrode 21 at a position facing the opening 21a formed in the guard electrode 21. In the state, the configuration in which the detection electrode 22 is arranged is employed. However, when the influence of the electric field from the outside is small, the detection electrode 22 is in a state that is substantially flush with the guard electrode 21 or a part of the detection electrode 22 protrudes into the opening 21a. 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 may be employed. In any configuration, the detection electrode 22 and the guard electrode 21 are of course 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, a DSP (digital signal) that generates the waveform data by sampling, for example, the voltage signal V4 together with the configuration in which the effective value of the voltage signal V4 is detected (measured) by the voltmeter 35 and output. A configuration including a processing unit) may be employed. By adopting this configuration, the waveform data is output to the outside of the voltage detection device 1 or displayed as a waveform of the AC voltage V1 on the display unit provided in the voltage detection device 1 based on the waveform data. Is possible.

  In the bootstrap circuit 27 shown in FIG. 1 described above, the resistor 27e is arranged between the inverting input terminal and the output terminal of the operational amplifier 27a to give a gain. It can also be realized by adopting the configuration shown in FIG. In the bootstrap circuit 27 shown in the figure, the inverting input terminal and the output terminal of the operational amplifier 27a are short-circuited without providing the resistor 27e, thereby functioning as a buffer (amplifier having a magnification of 1).

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

  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. .

  As an example, the line voltage detecting 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 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. 5, 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 way. 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 CPU and a memory (both not shown), and a line voltage for obtaining (calculating) a line voltage based on the voltage 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. 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. 5, in order to detect (measure) the AC voltage Vr of the electric circuit R with the voltage detection device 1r, the floating circuit portion 2 is brought close to the electric circuit R and the detection electrode 22 is used. 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, 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 bootstrap circuit 27, the drive circuit 25, the photocoupler 26, and the main body circuit unit 3 constituting the feedback loop are connected to the AC voltage Vr of the electric circuit R. By executing a feedback control operation that changes the voltage value of the voltage signal V4 in response to the change, 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) follows the AC voltage Vr. Let In the other voltage detection devices 1s and 1t, the bootstrap circuit 27, the integration circuit 24, the drive circuit 25, the photocoupler 26, and the main body circuit unit 3 constituting the feedback loop are also connected to the AC voltages Vs and Vt of the electric circuits S and T 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 changed to an AC voltage by executing a feedback control operation that changes the voltage value of the voltage signal V4 in response to the change in voltage. Follow 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 configured to include the bootstrap circuit 27 allows each AC voltage Vr, Vs, Vt to be spread over a wide frequency band. Therefore, the line voltages Vrs, Vst, and Vrt can be detected (measured) with high accuracy over a wide frequency band.

  In addition, although the example using a plurality of voltage detection devices 1 having the same configuration each including the main power supply circuit 31 and the converter 32 has been described above, the main power supply circuit 31 and the converter 32 are provided in one of the plurality of voltage detection devices 1. 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, 1r, 1s, 1t Voltage detection device 2 Floating circuit part 3 Main body circuit part 4 Detection object 21 Guard electrode 21a Opening part 21b Insulating layer 22 Detection electrode 26 Photocoupler 27 Bootstrap circuit 34 Voltage generation circuit 51 Line voltage detection Device 52 Calculation unit R, S, T Electric circuit V1, Vr, Vs, Vt AC voltage V2 Detection voltage signal Vdi Potential difference Vrs, Vrt, Vst Line voltage

Claims (6)

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 bootstrap circuit that operates with a floating power source generated with reference to a reference voltage, and outputs a detection signal whose amplitude changes according to an AC potential difference between the detection target AC voltage and the reference voltage;
An insulation circuit that inputs the detection signal and electrically insulates it and outputs it as an insulation detection signal;
A voltage detection device comprising: a voltage generation circuit that amplifies the insulation detection signal so as to reduce the potential difference and generates the reference voltage.   The voltage detection apparatus 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, further comprising a guard electrode defined by the reference voltage, wherein a primary side circuit of the bootstrap circuit and the insulating circuit is covered by the guard electrode. An opening is formed in the guard electrode;
The voltage detection device according to claim 3, 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 in any one of Claim 1 to 4 provided with the insulator which covers the whole surface facing the said detection target body in the said detection electrode. The plurality of corresponding electric circuits as the detection object are configured so that the detection electrodes can be opposed to 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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