JP6981711B2 - Non-contact type voltage detector - Google Patents

Description

The present invention relates to a non-contact type voltage detector that non-contactly detects the state of charge of a charging unit charged by a DC voltage.

For some time, a voltage detector has been used to determine whether or not electricity is being supplied to an electric line. Generally, there are two types of voltage detectors for AC electric lines: contact type and non-contact type. On the other hand, it is difficult to detect a DC electric line in a non-contact manner, and a DC voltage detector is generally a contact type.
The present inventors have previously developed a non-contact type voltage detector for detecting a "feeding circuit" of a DC electric railway (see Non-Patent Document 1). A high DC voltage such as 1500V is applied to the feeder circuit. This non-contact type voltage detector includes a detection electrode charged by electrostatic induction, a variable capacitance means connected to the detection electrode via a transmission path, and an oscillator that periodically changes the capacitance of the variable capacitance means. Have. Then, by pointing the detection electrode toward the charging unit (for example, an overhead wire) and periodically changing the capacitance of the variable capacitance means, an AC signal whose amplitude changes according to the charging state of the detection electrode is generated, and this AC is generated. The charging state of the charging unit is determined based on the amplitude of the signal.

Generally, when trying to detect a static charge state generated in a detection electrode, the charge state of the detection electrode diminishes with the passage of time due to a slight charge transfer from the detection electrode to the detection circuit. Therefore, stable detection is hindered. On the other hand, according to the above-mentioned non-contact type voltage detector, even if the voltage of the charging unit does not change, dynamic processing is performed in the voltage detector to connect the detection electrode and the variable capacitance means to the transmission line. Generate an AC signal. This prevents the charged state of the detection electrode from diminishing with the passage of time, and the AC signal having an amplitude corresponding to the charged state of the detection electrode makes the charged state of the charging unit stable and highly sensitive. It is possible to detect with.

Yuji Tanaka Taku Fukuhara Mitsuyuki Shimohara Kazumi Nishimura Nakajima et al. Hiroo Imamura, "Development of a method for non-contact confirmation of DC voltage", Institute of Electrical Engineers of Japan, Materials, Institute of Electrical Engineers of Japan, May 20, 2015, p. .. 7-10

In recent years, an increasing number of facilities are operated by a DC voltage having a lower voltage than the voltage of a "feeder circuit", for example, a battery power supply of 100 V DC. Conventionally, in such equipment, the charging state of a charging unit (for example, an electric line) is detected by using a contact-type voltage detector at the time of maintenance or the like. When a contact-type voltage detector is used, there is a potential risk of causing an electric accident, such as the probe touching the electrode of the charging part and an unintended metal part to short-circuit the charging part.
Therefore, the present inventors use a non-contact type voltage detector for direct current that targets the previously developed "feeder circuit" to detect a charging unit to which a low-voltage DC voltage such as 100 V DC is applied. We verified whether the charging status could be detected in a non-contact manner. However, with such a charging unit, it is difficult to detect the charging state with the desired sensitivity.

In the verification experiment, the detection electrode (also called an electrostatic antenna) is brought close to the charging part (electric line on the anode side, etc.), and the housing of the non-contact type voltage detector is set to the reference potential point (electric line on the cathode side, etc.). It was found that the voltage detection reaction occurred in the voltage detector when the voltage was brought closer. Further, in the verification experiment, when the detection electrode accidentally comes into contact with the charging part to be detected, even if both are insulated and coated, the charging state of the detection electrode and the state of the internal circuit change. After that, it was found that normal circuit operation could not be obtained unless the circuit was initialized. It is presumed that this is due to the slight collision of the insulating coating, which causes a slight charge due to the piezo effect or friction.
An object of the present invention is to provide a non-contact type voltage detector capable of non-contactly and sensitively detecting the charging state of a charging unit to which a low voltage such as DC 100V is applied.

In order to achieve the above object, the present invention
It is a non-contact type voltage detector that detects the charging state of the charging part charged by DC voltage in a non-contact manner.
An electrostatic antenna charged by electrostatic induction and
A detection circuit that detects the charged state of the electrostatic antenna and
A determination unit that determines the charging state of the charging unit to which the electrostatic antenna is brought close to based on the detection result of the detection circuit, and a determination unit.
Equipped with
The electrostatic antenna is characterized by having a first detection electrode conducting to the input portion of the detection circuit and a second detection electrode conducting to the ground potential of the detection circuit.

Here, the "charging unit" is, for example, an electric line or an electrode to which a DC voltage is applied.
According to this configuration, the electrostatic antenna includes, in addition to the first detection electrode conducted to the input portion of the detection circuit, a second detection electrode conducting to the ground potential of the detection circuit. Therefore, by appropriately arranging the first detection electrode and the second detection electrode with respect to the charging unit to be detected and the wiring or electrode on the cathode side thereof, the charging state of the charging unit is detected by the electrostatic antenna. It is possible to generate a charge of a possible magnitude. As a result, the charging state of the charging unit can be detected non-contactly and with high sensitivity. Further, since the detection can be performed with high sensitivity, the distance between the charging unit and the electrostatic antenna can be increased at the time of detection, and it is possible to avoid the problem that the two come into contact with each other and the normal circuit operation is hindered.

Here, both the first detection electrode and the second detection electrode include a long planar shape portion on one side.
The planar shape portion of the first detection electrode and the planar shape portion of the second detection electrode are close to each other so that they have a V-shape when viewed in the longitudinal direction, and they are close to each other. The other long side should be separated.
According to this configuration, when there is an electric line on the anode side as a charging part to be detected and the electric line and the electric line on the cathode side are arranged apart from each other, the second electric line is located between these two electric lines. 1 The detection electrode and the second detection electrode can be arranged so as to be inserted. With such an arrangement, when a DC voltage is applied to the charging unit, the electrostatic antenna can be charged with a detectable magnitude, and the charged state can be detected with high sensitivity.

Further, both the first detection electrode and the second detection electrode include a long planar shape portion on one side.
It is preferable that the planar shape portion of the first detection electrode and the planar shape portion of the second detection electrode are separated so that the charging portion can be inserted between the two.
According to this configuration, there is an electric line on the anode side as a charging part to be detected, and when this electric line and the electric line on the cathode side are arranged close to each other, both sides of these two electric lines are surrounded. As described above, the first detection electrode and the second detection electrode can be arranged. With such an arrangement, when a DC voltage is applied to the charging unit, the electrostatic antenna can be charged with a detectable magnitude, and the charged state can be detected with high sensitivity.

Further, both the first detection electrode and the second detection electrode include one or a plurality of long planar shape portions on one side.
The electrostatic antenna is
The long sides of each other so that the planar shape portion of any of the first detection electrodes and the planar shape portion of any of the second detection electrodes have a V shape when viewed in the longitudinal direction. In the first form, in which they are close to each other and the other long sides of each other are separated from each other.
A second embodiment in which the planar shape portion of any of the first detection electrodes and the planar shape portion of any of the second detection electrodes are separated so that the charging portion can be inserted between the two. When,
It should be configured to be deformable.
According to this configuration, when the form of the detection target is different (for example, parallel lines that are close to each other and parallel lines that are separated from each other), the form of the electrostatic antenna is changed according to the form of the target, so that the charging state of the charging unit is charged. Can be detected with high sensitivity.

Further, the detection circuit is
The first transmission line that guides the electric charge from the input unit,
The first variable capacitance means connected to the first transmission line and
An oscillator that periodically changes the capacitance of the first variable capacitance means,
Have,
An AC signal whose amplitude changes according to the charging state of the electrostatic antenna due to a change in the capacitance of the first variable capacitance means is generated in the first transmission line.
The determination unit may be configured to determine the charging state of the charging unit based on the phase of the signal in which the amplitude change of the AC signal is expanded and converted into the phase change.

In general, when trying to detect a minute charged state generated by electrostatic induction as it is, the charged state of the detection electrode diminishes with the passage of time due to the transfer of charge from the electrostatic antenna to the detection circuit, and is stable. Detection is hindered. However, according to the above configuration, it is possible to avoid generating an AC signal by the action of the oscillator and the first variable capacitance means and diminishing the charged state of the electrostatic antenna. Further, the amplitude and phase of the AC signal generated by periodically changing the capacitance of the first variable capacitance means change according to the charging state of the electrostatic antenna, but these are minute changes. Therefore, according to the above configuration, the determination unit determines the charging state of the charging unit based on the phase of the signal in which the amplitude change of the AC signal is expanded and converted into the phase change. Thereby, the charging state of the charging unit can be correctly determined in the minute charging region, that is, the weak electric field region. In addition, unlike the case of directly detecting the amplitude change, it has a high-resolution AD converter and high-speed processing capability for digital signal processing such as Fourier transform in order to detect the phase of the signal expanded and converted into the phase change. A CPU (central arithmetic processing device) is not required, and component costs can be reduced.

Further, the detection circuit is
A second transmission line connected in parallel with the first transmission line,
A second variable capacitance means connected to the second transmission line and whose capacitance is periodically changed by the oscillator.
A DC blocking filter that is connected to the second transmission path and blocks the transmission of DC component signals.
A differential amplifier that outputs the difference between the AC signal output to the first transmission line and the AC signal output to the second transmission line, and
Have,
The determination unit may determine the charging state of the charging unit to which the electrostatic antenna is brought close to, based on the phase difference between the output of the differential amplifier and the AC signal output to the second transmission line.

According to this configuration, as the AC signal output from the second transmission line, an AC signal that is not affected by the charging state of the electrostatic antenna and is affected by external factors such as the temperature characteristics of the circuit and camera shake is generated. To. Therefore, by performing the determination based on the AC signal of the first transmission line and the AC signal of the second transmission line, it is possible to cancel the phase change due to an external factor and perform an accurate determination.

According to the present invention, it is possible to detect the charging state of the charging unit to which a low voltage such as DC 100V is applied in a non-contact manner and with high sensitivity.

It is a block diagram which shows the non-contact type voltage detector of 1st Embodiment of this invention. It is a circuit diagram which shows a specific example of the detection circuit of FIG. It is a figure explaining the operation principle of the detection circuit of FIG. It is a circuit block diagram which shows the preferable circuit example of the notch filter of FIG. It is a circuit diagram which shows an example of the resistance voltage divider of FIG. It is a circuit diagram which shows an example of the resistance voltage divider and the phase difference zero point adjustment element of FIG. It is a waveform diagram which explains the operation of a phase difference detection circuit, and shows the state when a phase difference is small. It is a waveform diagram which explains the operation of a phase difference detection circuit, and shows the state when a phase difference is large. 6 is a graph showing the first comparison between the simulation result of the circuit of FIG. 2 and the numerical calculation result using the theoretical formula (1b). 6 is a graph showing a second comparison between the simulation result of the circuit of FIG. 2 and the numerical calculation result using the theoretical formula (1e). It is a perspective view (A) and a front view (B) which show the structure of the electrostatic antenna of FIG. It is a perspective view (A) and a front view (B) which show the electrostatic antenna of the 1st modification. It is a front view (A) which shows the 1st form, and the front view (B) which shows the 2nd form of the electrostatic antenna of the 2nd modification. It is a block diagram which shows the detection circuit of the 2nd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First Embodiment)
FIG. 1 is a block diagram showing a non-contact type voltage detector according to the first embodiment of the present invention.
The non-contact type voltage detector 100 according to the first embodiment of the present invention non-contactly detects the charging state of a charging unit (for example, an electric line of a battery power supply) to which a low-voltage DC voltage such as DC 100V is applied. It is a device to do. The non-contact type voltage detector 100 includes an electrostatic antenna 120, a detection circuit 110, a determination unit 130, an output unit 140, and a power supply unit 150 that supplies an operating voltage to each unit.

The electrostatic antenna 120 is an antenna that is charged by electrostatic induction from the charging unit when it is close to the charging unit to be detected. The electrostatic antenna 120 has a first detection electrode 121A conducted to the input portion of the detection circuit 110 and a second detection electrode 121B conducted to the ground potential of the detection circuit 110. The specific structure of the electrostatic antenna 120 will be described later.
The detection circuit 110 periodically changes the capacitance values of the notch filter 115 as a band-stop filter, the pair of variable capacitance elements 116A and 116B provided on the output terminal side of the notch filter 115, and the variable capacitance elements 116A and 116B. The oscillator 117 is provided, and the phase difference detecting unit 118 for detecting the phase difference of the output voltage (AC signal) of the variable capacitance elements 116A and 116B is provided. Further, an AC coupling capacitor (capacitor) 119C is provided between the notch filter 115 and the variable capacitance element 116B to block the DC component and allow only the AC component to pass through. A resistor R5 is connected between the connection node between the storage unit (capacitor) 119C and the variable capacitance element 116B and the ground potential GND1 of the detection circuit 110, and the resistor R5 and the capacitor C form a DC blocking filter. ing.

Further, resistors R4a and R4b having high resistance values (for example, 10 MΩ) are connected between the notch filter 115 and the variable capacitance elements 116A and 116B, respectively. The resistors R4a and R4b are AC-like between the output of the notch filter 115 and the variable capacitance elements 116A and 116B, and further between the variable capacitance elements 116A and 116B in a high frequency region including the frequency of the signal to be detected. It is for separating into.
Further, AC-coupling capacitors 119A and 119B are connected between the variable capacitance elements 116A and 116B and the two input terminals of the phase difference detection unit 118, respectively.

FIG. 2 is a circuit diagram showing a specific example of the detection circuit of FIG.
As shown in FIG. 2, as the variable capacitance elements 116A and 116B, for example, the gate capacitance (capacity between the gate electrode and the semiconductor substrate) of the MOS field effect transistor can be applied. By connecting the source terminal of the MOS field effect transistor to the reference potential point and applying the voltage (sine wave) generated by the oscillator 117 to the drain terminal, the capacitance value of the gate capacitance can be changed. In addition, other elements or circuits such as a varicap diode may be used instead of the MOS field effect transistor.
The oscillator 117 generates a sine wave (sine wave) having a predetermined frequency. As the predetermined frequency, it is desirable to select a frequency that is not easily affected by the frequency of the commercial AC power supply (50 Hz or 60 Hz) or a frequency that is an integral multiple of the frequency (50 Hz or 60 Hz).

Here, the reason for adopting the configuration in which the variable capacitance elements 116A and 116B are provided and the capacitance value is changed by the oscillator 117 will be described.
FIG. 3 shows a diagram illustrating the operating principle of the detection circuit of FIG.
First, an electric field detection type voltage detector that detects the charging state of the charging unit (for example, a power failure / live line of an electric line) by detecting the amount of static charge electrostatically induced in the detection electrode will be described. In this method, immediately after the detection electrode is brought close to the charging unit, an electric charge corresponding to the strength of the electric field is electrostatically induced in the detection electrode. However, the input impedance of the actual amplifier connected to the detection electrode cannot be infinite and has a finite value. Therefore, as time passes, the electric charge is released from the detection electrode due to the leak, and the strength of the electric field cannot be detected accurately.

On the other hand, in the non-contact type voltage detector 100 of the present embodiment, as shown in FIG. 3, variable capacitance elements 116A and 116B connected to the first detection electrode 121A are provided, and their capacitance values change periodically. .. According to this configuration, when the capacitance value of the variable capacitance elements 116A and 116B changes, the electric charge induced in the first detection electrode 121A moves back and forth between the first detection electrode 121A and the variable capacitance elements 116A and 116B. As a result, the variable capacitance elements 116A and 116B and their driving means (oscillator 117) operate as a kind of electrostatic generator, and the amplitude corresponds to the magnitude of the electrostatic induction generated in the electrostatic antenna 120. And an AC signal whose phase changes is generated. In such an operation process, the charge amount of the first detection electrode 121A does not gradually decrease due to the loss of charge, so that an AC signal having an amplitude and a phase corresponding to the magnitude of electrostatic induction is generated even after a lapse of time. It is output. Then, such an AC signal can accurately detect the charging state of the charging unit.

FIG. 4 shows a circuit example of a 2-T type filter suitable as the notch filter 115 of FIG.
In order to generate an AC signal that changes according to the charging state and accurately determine the charging state of the charging unit, it is necessary to suppress the mixing of other AC components that become noise into the detection circuit 110. On the other hand, the DC voltage applied to the charging unit is often generated from, for example, a commercial AC power supply, and therefore, the frequency component of the commercial AC power supply or its harmonic component is mixed as noise in the detection circuit 110. Is likely to occur.

The notch filter 115 is provided to remove or reduce the frequency component and its harmonic component of the commercial AC power supply in order to prevent such noise from being mixed. Specifically, as shown in FIG. 4A, the notch filter 115 is a single-stage notch filter NF composed of three resistance elements R1 to R3 and three capacitive elements C1 to C3. As shown in B), it is configured by connecting three vertically. There are only two types of elements constituting the single-stage notch filter NF of FIG. 4A, a 10 MΩ 1% product and a 100 pF 1% product, and these are connected in series or in parallel to form a filter. By limiting the types of parts to two types in this way, there is an advantage that assembly is easy and it is not necessary to use a resistor exceeding 10 MΩ, which is somewhat uncertain about the quality. Further, the notch filter 115 having such a configuration can widen the attenuation band at the cost of inferior attenuation at the center frequency by intentionally deviating from the regular design value as a 2-T type filter, so that it is a basic commercial AC power supply. In the region from 50 and 60 Hz of the wave to 100 and 120 Hz of the second harmonic, the disturbing wave can be greatly attenuated to 1/3000 to 1/10000. In addition, there is an effect that it is less susceptible to the error of the element.

As shown in FIG. 2, the phase difference detection unit 118 includes a resistance voltage divider 15 that inputs an AC signal from the first transmission path to which one of the variable capacitance elements 116A is connected, and an amplifier that amplifies the output of the resistor voltage divider 15. The output of the resistance voltage divider / phase difference zero point adjusting element 16 and the resistance voltage divider / phase difference zero point adjusting element 16 for inputting an AC signal from the second transmission line to which the 17A and the other variable capacitance element 116B are connected. The amplifier 17B to be amplified, the differential amplifier 17C that extracts the differential voltage between the output of the amplifier 17A and the output of the amplifier 17B, the comparator 18A that inputs the output of the differential amplifier 17C, and the output of the amplifier 17B are input. A comparator 18B, a logic circuit 19, an RC primary low frequency pass filter 21 including a resistor R21 and a capacitor C21 are provided.

FIG. 5 shows a circuit diagram showing an example of the resistance voltage divider of FIG. FIG. 6 shows a circuit diagram showing an example of the resistance voltage divider and phase difference zero point adjusting element of FIG.
The resistance voltage divider 15 is an AC signal output to the first transmission line by the resistor R15 connected in series to the first transmission line and the resistance R16 connected between the first transmission line and the ground potential line. Is divided by a predetermined ratio.
The resistance voltage divider and phase difference zero point adjusting element 16 is a second transmission line due to a resistor R17 connected in series with the second transmission line and a resistance R18 connected between the second transmission line and the ground potential line. The AC signal output to is divided by a predetermined ratio. Further, the resistance voltage divider and phase difference zero point adjusting element 16 is an AC signal output to the second transmission line by the capacitor C17 and the variable resistor R19 connected in series between the second transmission line and the ground potential line. Is given a delay to adjust the phase.

Here, an example of a phase adjusting method using a resistance voltage divider and a phase difference zero point adjusting element 16 will be described.
The phase of the AC signal output to the second transmission line is the same as that of the AC signal output to the first transmission line when the first detection electrode 121A and the second detection electrode 121B are short-circuited and the induced charge is zero. Adjust so that the phase difference φ is a value near zero that is not zero.
At the time of adjustment, first, the first detection electrode 121A and the second detection electrode 121B are short-circuited to keep the induced charge at zero. Further, an AC voltage having the same amplitude and the same phase is applied to the two inputs of the phase difference detection unit 118. Both output terminals of the capacitors 119A and 119B in FIG. 2 may be short-circuited. Here, the voltage gain of one of the amplifiers 17A and 17B is adjusted so that the output Vdiv of the differential amplifier 17C becomes zero. Instead of adjusting the gain, the values of the resistors R16 and R18 constituting the resistance voltage divider 15 or the resistance voltage divider and phase difference zero point adjusting element 16 may be adjusted.

Next, the short circuit of the output terminals of the capacitors 119A and 119B is opened, the value of the variable resistor R19 of the resistance voltage divider and the phase difference zero point adjusting element 16 is adjusted, and the amplitude (inter-peak voltage) of the output Vdiv of the differential amplifier 17C is adjusted. ) Is adjusted to a small voltage such as 10 mVp-p. The smaller the amplitude of the output Vdiv is set, the smaller the phase difference φ becomes and the sensitivity to the amplitude difference Δ improves, but zero is not desirable. The phase difference φ and the amplitude difference Δ indicate the phase difference and the amplitude difference between the AC signal output to the first transmission line and the AC signal output to the second transmission line.
By such an adjustment method, the desired adjustment of the phase difference φ is achieved. The phase adjustment is typically performed, for example, at the adjustment stage before shipment from the factory, but may be performed at the time of circuit reset before voltage detection or at the time of calibration processing. Further, the phase adjustment may be performed automatically by the adjusting device, or may be performed manually.

It is advisable to pay attention to the following points when adjusting the phase. When the variable capacitance element 116A is a field effect transistor, the drain-source capacitance and the gate-source capacitance decrease as the drain-source voltage and the gate-source voltage increase. Therefore, since the capacitance of the variable capacitance element 116A decreases in the charged state than in the uncharged state, the AC signal Vd1 on the detection side (see FIG. 2) becomes the AC signal Vd2 on the correction side (FIG. 2). Compared to (see), it changes to the lead phase. In this case, the AC signal Vd2 is placed on the delayed phase side with respect to the AC signal Vd1 on the detection side by the phase difference adjuster on the correction side (variable resistor R19 in FIG. 6), for example, the voltage gain of the differential amplifier 17C is 100 times larger. In that case, the differential voltage Vdiv, which is the output, is set to, for example, 10 mV. If the capacitance of the variable capacitance element 116A increases due to an increase in charge, the AC signal Vd2 on the correction side is set to the lead phase side with respect to the AC signal Vd1 on the detection side, and the output (difference voltage Vdif) of the differential amplifier 17C is large. To set. When the AC signal Vd2 on the correction side is set to the delayed phase, the amplitudes of the AC signals Vd1 and Vd2 become | Vd1 |> | Vd2 | There is no. In order to advance the AC signal Vd2 on the correction side to the AC signal Vd1 on the detection side and set the phase, a capacitance of about half that of the capacitor C17 is added in parallel with the resistor R16 constituting the resistance voltage divider 15 on the detection side. And so on.

Here, a suitable setting example of the voltage division ratio and the amplification factor is shown. For example, when the output voltage of the oscillator 117 is 0.3 Vp-p and the voltage division ratio between the resistance voltage divider 15 and the resistance voltage divider / phase difference zero point adjusting element 16 is both 11: 1, the voltages of the amplifiers 117A and 117B are used. The gain should be set to 33 times, and the differential voltage gain of the differential amplifier 17C should be set to 100 times. The reason why the differential voltage gain is set to 100 times is that the differential voltage Vdif of the AC signals Vd1 and Vd2, which are the outputs of the amplifiers 17A and 17B, becomes very small, so that the amplitude is increased to operate the comparator 18A normally. be. However, the above setting values are suitable when a predetermined field effect transistor is used for the variable capacitance elements 116A and 116B that operate as sensor elements for detecting the induced charge, and need to be appropriately changed depending on the sensor element to be selected. There is.

7 and 8 show waveform diagrams illustrating the operation of the phase difference detection unit 118. 7 and 8 (A) to 8 (F) show waveforms of the output voltage of each node of the phase difference detection unit 118 shown in FIG. 7 and 8 (G) show an enlarged part X of the waveform diagram of the AC signal Vd1. Here, the polarities of the comparators 18A and 18B are reversed.
As shown in these waveform diagrams, the pair of amplifiers 17A and 17B have an AC signal generated by a periodic change in the capacitance of one variable capacitance element 116A and a periodic capacitance of the other variable capacitance element 116B. The AC signal generated by the change is amplified and output (AC signals Vd1 and Vd2 in FIGS. 7 and 8). The differential amplifier 17C inputs AC signals Vd1 and Vd2 from the amplifiers 17A and 17B and outputs a difference voltage Vdif. The difference voltage Vdef becomes zero when the amplitude and phase of the AC signals Vd1 and Vd2 completely match. On the other hand, if one or both of the amplitudes and phases of the AC signals Vd1 and Vd2 are different, the difference voltage Vdef becomes an AC signal having the same frequency as the AC signals Vd1 and Vd2.

When the phase difference φ of the AC signals Vd1 and Vd2 is small and almost fixed, a slight change in the amplitude difference Δ of the AC signals Vd1 and Vd2 becomes a large change in the phase difference θ between the difference voltage Vdif and the AC signal Vd2. appear. That is, the difference voltage Vdef is a signal in which a minute change in the amplitude difference Δ of the AC signals Vd1 and Vd2 is expanded and converted into a phase change. FIG. 7 shows a case where the amplitude difference Δ is small, and FIG. 8 shows a case where the amplitude difference Δ is large. The change in the amplitude difference Δ is so small that it cannot be visually recognized on the graphs of FIGS. 7 and 8, but when the amplitude difference Δ in FIG. 7 is small, the phase difference θ becomes close to 90 degrees, and the amplitude difference Δ in FIG. 8 When is large, the phase difference θ becomes close to 0 degrees. This operating principle will be described in detail later.

The comparator 18A compares the difference voltage Vdiv output from the differential amplifier 17C with the reference voltage, and outputs a binary level signal Vcdif. The comparator 18B compares the AC signal Vd2 with the reference voltage and outputs a binary level signal Vc2. The logic circuit 19 takes these signals Vcdif and Vc2 as inputs, performs a logical operation shown in the truth table of FIG. 2, and outputs a binary level signal Vxlg indicating the result.

The duty ratio of the output signal Vxlg obtained here is a value that reflects the phase difference θ between the difference voltage Vdif and the AC signal Vd2. In the examples of FIGS. 7 and 8, the duty ratio of the output signal Vxlg is inversely proportional to the phase difference θ, but the duty ratio can be set to a value proportional to the phase difference θ by changing the polarity of the output signal Vxlg. can.
The circuit of FIG. 2 is used in the range of the amount of charge such that the induced charge of the first detection electrode 121A is reflected in the amplitude difference Δ rather than the phase difference φ. Further, by optimizing the element constant, the phase difference φ is set to a value larger than zero but very small. Due to such a range of use and initial settings, when the amplitude difference Δ changes slightly according to the change in the induced charge of the first detection electrode 121A, this minute change in the amplitude difference Δ expands to a large change in the phase difference θ. It is converted and continuously changes the duty ratio of the output signal Vxlg. The output signal Vxlg is converted into a DC voltage Vout proportional to the duty ratio by the RC primary low-pass filter 21, and is output to the determination unit 130.

If a region in which the amplitude difference Δ of the AC signals Vd1 and Vd2 changes significantly can be used, the amplitude of the difference voltage Vdef may be detected to detect the induced charge amount of the first detection electrode 121A. This makes it possible to detect the charging state of the charging unit (for example, a power failure / live line of an electric line). However, when the DC voltage is detected in a non-contact manner, the change in the amplitude difference Δ of the AC signals Vd1 and Vd2 is small, and it becomes difficult to directly detect the change in the amplitude difference Δ. The change of is expanded and converted into a large change of the phase difference θ.

<Explanation of circuit operating principle>
Here, in the operation of the circuit of FIG. 2, when the phase difference φ of the AC signals Vd1 and Vd2 is set to be small and substantially fixed, a slight change in the amplitude difference Δ of the AC signals Vd1 and Vd2 is the difference voltage. The operating principle that is expanded and converted into a large change in the phase difference θ between the Vdef and the AC signal Vd2 will be described. This explanation is also an explanation of the property of a circuit that outputs a change in physical quantity as a phase change using a capacitance change type sensor, and this principle can be applied to a circuit using almost all capacitance change type sensors. It can be said that. Hereinafter, the variable capacitance elements 116A and 116B are referred to as capacitive change type sensors.

In this embodiment, the electrostatic capacity change type sensors (116A, 116B) are electrostatically induced by the electric field E and accumulate the electric charge q. In this state, AC signals Vd1 and Vd2 are obtained by actively driving the capacitance change type sensors (116A, 116B) at a constant frequency f [Hz]. Then, the change in the amplitude difference Δ of the AC signals Vd1 and Vd2 is obtained as the change in the phase difference θ expanded (amplified) from the difference voltage Vdef (= Vd1-Vd2) which is the output of the differential amplifier 17C.
Here, the electric field E is a physical quantity to be detected. Further, since the capacitance change type sensors (116A, 116B) are actively driven by an AC voltage having a constant frequency f [Hz], they can be regarded as an actuator or an electrostatic generator.

It is explained as follows that the change of the amplitude difference Δ is "dilated" to the change of the phase difference θ in the differential amplifier 17C.
First, the differential voltage Vdef, which is the output of the differential amplifier 17C, can be expressed as the following equations (1) and (1b).

here,
f: Drive frequency of the capacitive change type sensor [Hz]
π: Pi t: Time [sec]
Vd2: The AC signal [voltage] on the correction side, and the amplitude | Vd2 | = 1.
Vd1: It is an AC signal [voltage] on the detection side, and the amplitude | Vd1 | = 1 + Δ. Note that Δ can be either a positive value or a negative value, but when Δ is increased, it means an increase in the absolute value | Δ |.
Δ: Amplitude difference of the AC signal Vd1 on the detection side with respect to the AC signal Vd2 on the correction side φ: Phase difference of the AC signal Vd1 on the detection side with respect to the AC signal Vd2 on the correction side [rad]
Vdef: Output (difference voltage) of differential amplifier 17C
A: Voltage gain of differential amplifier 17C α = 2 ・ π ・ f ・ t
β = φ
"・" (Middle black): It is a multiplication symbol.
Further, β = φ << π, and it is assumed that cosφ≈1 and sinφ≈φ can be approximated.

The second term "-sinφ cos (2, π, f, t)" of the equation (1b) has a phase delayed by 90 degrees with φ> 0 or φ <0 with respect to "sin (2, π, f, t)". It means that it is a sine wave with a leading phase.
Since the circuit operates in the region of φ << π [rad], it may be regarded as 1 + Δ−cos φ≈Δ, and the difference voltage Vdiv can be expressed as the following equation (1c).

φ＝０つまり検出側の交流信号Ｖｄ１と補正側の交流信号Ｖｄ２の位相が完全に一致する場合において回路は機能しない。ただし、本実施形態のように静電容量変化型センサー（１１６Ａ、１１６Ｂ）を用いる回路においては静電容量変化型センサーと抵抗との組み合わせが信号に遅延を及ぼして各信号経路の位相特性に影響を及ぼす。このため、物理量Ｅのゼロ点で完全に交流信号Ｖｄ１、Ｖｄ２が同一位相であっても物理量Ｅの変化によって静電容量変化型センサー（１１６Ａ、１１６Ｂ）の静電容量に変化が起これば交流信号Ｖｄ１、Ｖｄ２の位相ずれは発生する。よって位相差φが完全にゼロになることは多く生じない。

The circuit does not function when φ = 0, that is, when the phases of the AC signal Vd1 on the detection side and the AC signal Vd2 on the correction side completely match. However, in a circuit using a capacitance change type sensor (116A, 116B) as in the present embodiment, the combination of the capacitance change type sensor and the resistor delays the signal and affects the phase characteristics of each signal path. To exert. Therefore, even if the AC signals Vd1 and Vd2 are completely in phase at the zero point of the physical quantity E, if the capacitance of the capacitance change type sensor (116A, 116B) changes due to the change of the physical quantity E, the AC signal is AC. Phase shift of the signals Vd1 and Vd2 occurs. Therefore, the phase difference φ does not often become completely zero.

この場合、式（１ｂ）、（１ｃ）は、sin（2・π・f・t）成分が優勢となるので、差電圧Ｖｄｉｆの位相は、交流信号Ｖｄ１、Ｖｄ２の位相に近づく。 Looking at the equations (1b) and (1c), if the amplitude difference Δ between the AC signal Vd1 on the detection side and the AC signal Vd2 on the correction side is zero, the difference voltage Vdef is “cos (2, π, f. It can be seen that the "t)" component becomes dominant. Therefore, the phase of the difference voltage Vdef approaches a phase different from the AC signals Vd1 and Vd2 by 90 degrees. In the case of φ << π [rad], it may be regarded as sin φ≈φ, so that if the amplitude difference Δ is zero, the difference voltage Vdiv has a small amplitude proportional to the phase difference φ.
On the other hand, as the amplitude difference Δ increases, the magnitude of each term of the equation (1b) is determined as in the following equation (3).

In this case, since the sin (2, π, f, t) component is dominant in the equations (1b) and (1c), the phase of the difference voltage Vdif approaches the phase of the AC signals Vd1 and Vd2.

That is, the phase of the output (difference voltage Vdif) of the differential amplifier 17C changes in the range of +90 degrees to 0 degrees or the range of 0 degrees to 90 degrees as the amplitude difference Δ increases from the time when the amplitude difference Δ = 0. do. According to the operating principle of such a circuit, a minute change in the amplitude difference Δ of the AC signals Vd1 and Vd2 is expanded and converted into a large change in the phase difference θ between the difference voltage Vdef and the AC signal Vd2.

Subsequently, the characteristics of this circuit will be described.
First, from the above equation (1b), the relational expression θ (Δ) between the phase difference θ of the difference voltage Vdef and the amplitude difference Δ with respect to the AC signal Vd2 on the correction side of the AC signal Vd1 on the detection side is obtained.
As shown in equation (4-1), the signal U to which the sine wave and cosine wave of the same frequency ω are added becomes a signal of the same frequency ω, and its amplitude | U | and phase δ are the coefficients V of the sine wave. And the coefficient W of the cosine wave, it can be calculated as the following equations (4-2) and (4-3).

If this is applied to the equation (1b) of the differential voltage Vdef, the amplitude | Vdef | and the phase δ of the differential voltage Vdef can be obtained as in the following equations (5-1) and (5-2).

式（１ｄ）、式（５−３）では、振幅差Δ＝０のときに位相差θ（Δ）は９０度となり、振幅差Δの増大に伴い位相差θ（Δ）は０度となり、図７および図８の波形と合致する。 Here, the phase δ indicates a value expressed in a polar coordinate format using a cosine wave as a reference waveform. In the present embodiment, in order to detect the zero crossing point of the signal waveform, the phase difference θ (Δ) is expressed by shifting the phase difference θ (Δ) by π / 2 and using the sine wave as the reference waveform, and further, the direction of change of the phase difference is also Adjust in the opposite direction according to the waveform diagrams of FIGS. 7 and 8. Then, the phase difference θ (Δ) can be expressed as the following equation (5-3), and the difference voltage Vdef can be expressed as the following equation (1d).

In the equations (1d) and (5-3), the phase difference θ (Δ) becomes 90 degrees when the amplitude difference Δ = 0, and the phase difference θ (Δ) becomes 0 degrees as the amplitude difference Δ increases. It matches the waveforms of FIGS. 7 and 8.

As can be seen from the equation (1b), it can be seen from the equation (5-3) that the voltage gain A of the differential amplifier 17C does not affect the detected phase difference θ. Further, since the phase difference φ of the AC signals Vd1 and Vd2 remains fixed once set, it becomes a constant, and the detected phase difference θ is a function of only the amplitude difference Δ of the detection side voltage Vd1.
The inside of the parentheses of the arctangent of the equation (5-3) represents the ratio of the sine wave component of the equation (1b) to the cosine wave component depending on the initial phase difference φ. As can be seen from Eq. (5-3), the smaller the initial setting phase difference φ, the greater the effect of the change in the amplitude difference Δ on the phase difference θ.

Further, since this circuit functions in the region where the amplitude difference Δ and the phase difference φ of the AC signals Vd1 and Vd2 are very small values, as can be seen from the equation (5-1), the output (difference) of the differential amplifier is used. The amplitude | Vdef | of the voltage Vdef) is also very small. Therefore, it is assumed that the voltage gain A of the differential amplifier 17C should be set to a sufficiently large value in consideration of the case where the comparator 18A in the next stage does not perform the desired operation. The voltage gain A of the differential amplifier 17C may be appropriately set according to the amplitude difference Δ and the phase difference φ of the AC signals Vd1 and Vd2. In particular, since the amplitude difference Δ = 0 is set at the zero point of the capacitance change type sensor (116A, 116B), it must be considered that the amplitude | Vdef | of the output voltage of the differential amplifier 17C becomes further smaller.

補正の詳細は次のごとくである。回路シミュレーションでは、差動増幅器１７Ｃより前段の回路の影響と思われるが、位相差φが完全に固定とはならない。具体的には、交流信号Ｖｄ１の振幅差Δが０〜０．１の範囲で変化したときに、初期の位相差φ＝０．５ｄｅｇが０．４６ｄｅｇに減少（初期の８％減）していた。式（１ｅ）では、このような位相差φの変化が反映されるように、位相差φを“φ＋Δσ”と補正した。σは補正定数で、例えば−０．４ｄｅｇである。この補正によれば、振幅差Δが０〜０．１と変化すると、位相差φは”０．５＋０×０．４”〜”０．５−０．１×０．４”となり、回路シミュレーションの実際の動作に近づく。なお、θ（Δ）は、式（１ｅ）から前述の通り求めることができるので、詳細は省略する。 Next, a comparison between the result of the circuit simulation and the numerical calculation result based on the theoretical formula is shown.
In FIGS. 9 and 10, as a result based on the theoretical formula, the phase angle θ at which the difference voltage Vdef (t, Δ) = 0 (zero cross point) is drawn as a function of the amplitude difference Δ with the phase difference φ as a parameter. .. The result of the circuit simulation is, so to speak, close to the experimental result of actually assembling the circuit, and in many cases, it is almost the experimental result itself. The amplitude difference Δ in the circuit simulation is the DC voltage applied to the sensor, and has the effect of indirectly increasing the change in the amplitude difference Δ of the AC voltage Vd1 on the detection side. On the other hand, the difference in amplitude Δ in the theoretical formula is different in that the amplitude of the AC voltage Vd1 on the detection side is directly increased.
Therefore, in the numerical calculation results of FIGS. 9 and 10, instead of θ (Δ) of the equation (5-3) obtained from the equations (1b) and (1d), the correction equation (Δ) closer to the actual circuit is used. The calculation result of 1e) is used.

The details of the correction are as follows. In the circuit simulation, the phase difference φ is not completely fixed, although it seems to be the influence of the circuit in the stage before the differential amplifier 17C. Specifically, when the amplitude difference Δ of the AC signal Vd1 changes in the range of 0 to 0.1, the initial phase difference φ = 0.5 deg is reduced to 0.46 deg (8% reduction at the initial stage). rice field. In the equation (1e), the phase difference φ is corrected to “φ + Δσ” so that such a change in the phase difference φ is reflected. σ is a correction constant, for example, −0.4 deg. According to this correction, when the amplitude difference Δ changes from 0 to 0.1, the phase difference φ becomes “0.5 + 0 × 0.4” to “0.5-0.1 × 0.4”, and the circuit simulation Get closer to the actual operation of. Since θ (Δ) can be obtained from the equation (1e) as described above, the details will be omitted.

First, the graph of FIG. 9 will be described.
The horizontal axis Δ is the voltage applied to the electrode 12A in the circuit simulation.
The plot lines of VxlgN [φ0.1deg] and VxlgN [φ0.5deg] in FIG. 9 are the results obtained by simulating the case (parameter) of the phase difference φ = 0.1 degree and 0.5 degree with a circuit simulator. It is a value obtained by standardizing the maximum value (logic level H) of the output Vxlg of the logic circuit 19 to 1 and the minimum value (logic level L) to 0 and taking an average value. This value varies between 75% and about 100% of the maximum output Vxlg. This indicates that the duty ratio of the output Vxlg has changed from 75% to about 100%, and that the phase difference θ (Δ) has changed from 90 degrees to 0 degrees.

The plot lines of θ (Δ) [φ0.1deg] and θ (Δ) [φ0.5deg] are the equations (2) when the voltage gain A = 1 and φ = 0.1 degrees and 0.5 degrees, respectively. It is a simulation result of plotting the phase angle of the point (zero cross) where the difference voltage Vdiv becomes zero using 1e), and the change of the phase angle of the output voltage of the differential amplifier 17C with respect to the change of the amplitude difference Δ (phase difference θ (phase difference θ). Δ) represents a change).
The plot line of VdefN [φ0.5deg] shows the change Vdef (Δ) of the difference voltage Vdif with respect to the amplitude difference Δ in the case of the initial (or setting) phase difference φ = 0.5 degree, which is in the range of 0 to 1 as in VxlgN. It is standardized and plotted in. This plot line shows the characteristics when the amplitude difference Δ is detected as it is for comparison.

Looking at the characteristic line (plot line of VdefN [φ0.5 deg]) when the amplitude difference Δ is directly detected, there is almost no sensitivity when the amplitude difference Δ = 0.003 or less, and the amplitude difference Δ = 0.003 to 0. It can be seen that low sensitivity (slope is gentle) occurs in the region of 01.
On the other hand, looking at the plot line of VxlgN [φ0.1 or 0.5deg], which is the characteristic line of the circuit of the present embodiment, it has sensitivity even in the region where the amplitude difference Δ = 0.003 or less (gradient). In the region of amplitude difference Δ = 0.003 to 0.01, it can be seen that higher sensitivity than the plot line of VdefN can be obtained.
When the DC voltage is non-contactly detected as in the non-contact type voltage detector of the present embodiment, the amplitude difference Δ is a small value such as 0.003 or less to 0.01 (corresponding to 3 mV or less to 10 mV). Sensitivity is required in a wide area. As can be seen from FIG. 9, in the circuit of the present embodiment, the required sensitivity is obtained in such an amplitude difference Δ.

In FIG. 9, it seems that the plot line of VxlgN and the plot line of θ (Δ) do not match. This is because the left vertical axis indicating the scale of VxlgN and the right vertical axis indicating the scale of θ (Δ) do not correspond to each other. In FIG. 9, in order to compare the sensitivity of VxlgN and the sensitivity of VdefN in the circuit simulation, the plot line of VxlgN is shown on the scale of the left vertical axis.

On the other hand, in FIG. 10, VxlgN is shown on the scale of the phase difference on the right horizontal axis so that VxlgN and θ (Δ) can be compared. As described above, an average value of VxlgN of 75% corresponds to a phase difference of 90 degrees, and 100% corresponds to a phase difference of 0 degrees. Therefore, when VxlgN is converted to the scale of the phase angle, it is converted as shown in FIG. From the graph of FIG. 10, the change of the phase difference θ (Δ) matches in the characteristics of the circuit simulation and the numerical calculation simulation using the theoretical formula (1e), and the characteristics of the theoretical formula and the circuit match. I understand.
Numerical calculation by the formula (1e), which is a theoretical formula created by the present inventor, is only a confirmation of the principle. This is because not all of the circuits are described, but as far as the comparison result of FIG. 10 is seen, the operation of the differential amplifier can be described theoretically.

Subsequently, returning to FIG. 1, the determination unit 130 and the output unit 140 will be described.
The determination unit 130 includes an AD converter 131 and a determination unit 132. The AD converter 131 periodically samples and captures the output Vout of the phase difference detection unit 118. The discriminator 132 discriminates the magnitude of the DC output voltage Vout based on the duty ratio of the output signal Vxlg of the phase difference detection unit 118, and outputs a discriminant signal (determination result) indicating the magnitude of charge of the electrostatic antenna 120. Output to 140. The determination unit 130 having such a function is a single semiconductor integrated circuit such as a single chip microcomputer having an AD conversion circuit, an AD conversion IC, a microprocessor having an arithmetic function, a semiconductor memory (ROM or RAM), or the like. It can be configured by a plurality of semiconductor integrated circuits. In this embodiment, the output voltage Vout is direct current. Therefore, a relatively expensive CPU (central processing unit) that requires processing power becomes unnecessary, and for example, a single-chip microcomputer having a built-in low-priced 8- to 12-bit AD conversion circuit can be used. Therefore, the component cost of the non-contact type voltage detector 100 can be significantly reduced.

The output unit 140 uses a plurality of LED (light emitting diode) lamps to display the determination result of the determination unit 130 at a plurality of levels, a sounding device 142 such as a speaker or a buzzer, and a display 141. A drive circuit 143 or the like for driving the device 142 is provided. The drive circuit 143 drives the display 141 so that the display level changes according to the magnitude of the charge of the electrostatic antenna 120 according to the discrimination signal of the discriminator 132. Further, the drive circuit 143 drives the sounding device 142 so as to output an alarm sound when the discrimination signal indicates an abnormal value. The measurer can determine the charging state of the charging unit by looking at the display level of the display 141.

<Electrostatic antenna>
11 is a perspective view (A) and a front view (B) showing the structure of the electrostatic antenna of FIG. 1. FIG.
The electrostatic antenna 120 includes two substrates 123A and 123B, a first detection electrode 121A and a second detection electrode 121B, and a connector 122 that is electrically connected to the detection circuit 110.
The substrates 123A and 123B both have a rectangular plate surface, and their long sides are close to each other so as to be V-shaped when viewed in the longitudinal direction, and the other long sides are located on the other end side. They are connected by a fixture 124 so as to be separated from each other.
The first detection electrode 121A and the second detection electrode 121B are, for example, rectangular electrodes, and are provided on the substrates 123A and 123B, respectively.

The connector 122 is fixed to any of the boards 123A and 123B and is electrically connected to the detection circuit 110. The connector 122 conducts the input portion of the detection circuit 110 (the input terminal of the notch filter 115 in FIG. 1) to the first detection electrode 121A via the conducting wire 122a, and conducts the ground potential GND1 of the detection circuit 110 for the second detection. Conducting to the electrode 121B.
Here, it is assumed that the pair of electric lines 31A and 31B of the anode and the cathode are arranged apart from each other as the charging unit to be detected (see FIG. 11B). In such a case, according to the electrostatic antenna 120, the first detection electrode 121A and the second detection electrode 121B can be arranged so as to be sandwiched between the two electric lines 31A and 31B. When a DC voltage is applied to the electric lines 31A and 31B, a relatively large electric field is generated between the two electric lines 31A and 31B. Therefore, the electrostatic antenna 120 is arranged as shown in FIG. 11B. Can generate a large charge. Therefore, even in the electric lines 31A and 31B to which a low-voltage DC voltage is applied, this DC voltage can be detected with high sensitivity.

<Electrostatic antenna of the first modification>
12A and 12B are a perspective view (A) and a front view (B) showing an electrostatic antenna of the first modification.
The non-contact type voltage detector 100 of the embodiment may include the electrostatic antenna 220 of the first modification. The electrostatic antenna 220 includes two substrates 223A and 223B, a first detection electrode 221A and a second detection electrode 221B, and a connector 222 for making an electrical connection with the detection circuit 110.
Both the substrates 223A and 223B have a plate shape in which a part is bent, and the flat plate-shaped portion of one substrate 223A and the flat plate-shaped portion of the other substrate 223B are arranged so as to face each other apart from each other. As such, they are connected by a fixture 224.

The first detection electrode 221A and the second detection electrode 221B are both rectangular electrodes, and are provided on the flat plate-shaped portions of the substrates 223A and 223B which are arranged so as to face each other.
The connector 222 conducts the input portion of the detection circuit 110 (the input terminal of the notch filter 115 in FIG. 1) to the first detection electrode 221A, and conducts the ground potential GND1 of the detection circuit 110 to the second detection electrode 221B. ..

Here, it is assumed that a pair of electric lines 31A and 31B of an anode and a cathode are arranged close to each other as a charging unit to be detected (see FIG. 12B). In such a case, according to the electrostatic antenna 220, the electrostatic antenna 220 is arranged so as to sandwich the two electric lines 31A and 31B between the first detection electrode 121A and the second detection electrode 121B. Can be done. At this time, the two electric lines 31A and 31B can be arranged so as to extend along the longitudinal direction of the first detection electrode 121A and the second detection electrode 121B. With such an arrangement, the electric fields of the two electric lines 31A and 31B act on the first detection electrode 121A and the second detection electrode 121B to form the first detection electrode 121A and the second detection electrode 121B. It is possible to generate a charge of a detectable magnitude. This makes it possible to detect this DC voltage with high sensitivity even in the electric lines 31A and 31B to which a low-voltage DC voltage is applied.

<Electrostatic antenna of the second modification>
13A and 13B are a front view (A) showing the first form of the electrostatic antenna of the second modification and a front view (B) showing the second form. 13 (A) and 13 (B) show views of the electrostatic antenna 320 when viewed in the longitudinal direction.
The non-contact type voltage detector 100 of the embodiment may include the electrostatic antenna 320 of the second modification. The electrostatic antenna 320 of the second modification has two substrates 323A and 323B, a first detection electrode 321A and a second detection electrode 321B, and a hinge 324 that connects the two substrates 323A and 323B so that the angles can be changed. The detection circuit 110 is provided with a connector 322 that is electrically connected to the detection circuit 110.

The two substrates 323A and 323B both have a long plate shape while being partially bent, and their long sides are connected to each other via a hinge 324. By rotating the hinge 324, it can be transformed into the first form shown in FIG. 13 (A) and the second form shown in FIG. 13 (B).
The connector 322 conducts the input portion of the detection circuit 110 (the input terminal of the notch filter 115 in FIG. 1) to the first detection electrode 321A, and conducts the ground potential GND1 of the detection circuit 110 to the second detection electrode 321B. ..
The first detection electrode 321A and the second detection electrode 321B are provided along the bent plate surface of the substrates 323A and 323B, and both have a first planar shape portion W1 and a second planar shape portion W2.
In the first embodiment, as shown in FIG. 13A, the first planar shape portion W1 of the first detection electrode 321A and the first planar shape portion W1 of the second detection electrode 321B are viewed in the longitudinal direction. It has a V-shaped arrangement. In such a form, when the two electric lines 31A and 31B are arranged apart from each other, the first detection electrode 321A and the second detection electrode 321B can be arranged so as to be inserted between them. .. As a result, as in the case of FIG. 11B, the state of charge of the DC voltage of the electric lines 31A and 31B can be detected with high sensitivity.

In the second embodiment, as shown in FIG. 13B, the second planar shape portion W2 of the first detection electrode 321A and the second planar shape portion W2 of the second detection electrode 321B face each other apart from each other. It will be an arrangement. In such a form, when the two electric lines 31A and 31B are arranged close to each other, the second planar shape portion W2 of the first detection electrode 321A and the second planar shape of the second detection electrode 321B are formed. The electrostatic antenna 320 can be arranged so as to sandwich the electric lines 31A and 31B with the portion W2. As a result, as in the case of FIG. 12B, the state of charge of the DC voltage of the electric lines 31A and 31B can be detected with high sensitivity.

As described above, according to the non-contact type voltage detector 100 of the present embodiment, the electrostatic antenna 120 has the first detection electrode 121A conducted to the input portion of the detection circuit 110, and the ground potential of the detection circuit 110. A second detection electrode 121B that is conductive with GND1 is provided. Therefore, by appropriately arranging the first detection electrode 121A and the second detection electrode 121B with respect to the charging unit (electric line or the like) to be detected and the wiring or electrode on the cathode side thereof, the low voltage is applied to the charging unit. Even if the DC voltage of the above is applied, a relatively large charge can be generated in the electrostatic antenna 120. Therefore, it is possible to detect the charging state in a non-contact manner and with high sensitivity by using such a charging unit as a detection target.

Further, according to the detection circuit 110 of the present embodiment, the capacitance of the variable capacitance element 116A is periodically changed to send an AC signal to the first transmission line to which the electrostatic antenna 120 and the variable capacitance element 116A are connected. Since it is generated, it is possible to prevent the charged state generated in the electrostatic antenna 120 from diminishing in the detection process. Therefore, the charging state of the charging unit to which the low-voltage DC voltage is applied can be detected with high sensitivity.
Furthermore, since the phase difference of the AC signal of the first transmission line is used for determination based on the AC signal of the second transmission line to which the DC blocking filter and the variable capacitance element 116B are connected, the temperature characteristics and camera shake of the circuit are used. It is possible to cancel the phase change due to an external factor such as, and make an accurate judgment.

(Second Embodiment)
FIG. 14 is a configuration showing a detection circuit of the non-contact type voltage detector of the second embodiment.
In the second embodiment, as shown in FIG. 14, notch filters 115A and 115B are separately provided in front of the variable capacitance elements 116A and 116B, respectively, and between the notch filters 115A and 115B and the variable capacitance elements 116A and 116B. Resistors R4a and R4b having high resistance values are connected to each of them. Further, the storage device (capacitor) 119C as an AC coupling means is provided not in the front stage of the variable capacitance element 116B but in the front stage of the notch filter 115B. Further, as the notch filters 115A and 115B, those having three connections as shown in FIG. 6 are used. Other than that, it is the same as the voltage detector of FIG. As the capacitance value of the capacitor (capacitor) 119C, a value such as 2200 pF can be adopted, and as the resistance value of the resistor R5, a value such as 30 MΩ can be adopted.

The voltage detector shown in FIG. 14 is a third-stage filter of the notch filters 115A and 115B by inserting 10 MΩ resistors R4a and R4b between the inputs of the variable capacitance elements 116A and 116B and the notch filters 115A and 115B. The output of the variable capacitance element 116A, 116B, and further, the variable capacitance elements 116A, 116B are separated from each other in an alternating current manner. By forming an RC primary low-pass filter with the resistors R4a and R4b and the variable capacitance elements 116A and 116B, the pulsating frequency and medium-wave broadcast wave of 6-phase and 12-phase rectification at the substation can be used. It can also have the effect of suppressing interference.
Further, by using the two notch filters 115A and 115B, there is an advantage that the influence of the variable capacitance elements 116A and 116B on the notch filter can be reduced.

Further, if the variable capacitance element 116B side that detects the influence of hand-held fluctuation has sensitivity to direct current, the sensitivity as a voltage detector drops, so that the direct current sensitivity on the variable capacitance element 116B side must be eliminated. In the example of FIG. 14, a resistor R5 is provided between the connection point between the capacitor 119C and the variable capacitance element 116B and the reference potential point inside the circuit, and a DC blocking filter (RC primary height) that makes the DC sensitivity almost zero. A region pass filter) is configured.

Although each embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment. For example, in the above embodiment, a pair of electric lines of an anode and a cathode are shown as a charging unit to be detected, and a form of an electrostatic antenna suitable for such electric lines is shown. However, if the form of the charging unit to be detected is different, the form of the electrostatic antenna can be changed in various ways in accordance with the form. For example, the first detection electrode and the second detection electrode may have different sizes or may be arranged asymmetrically.
Further, in the above embodiment, the determination unit is configured to output a discrimination signal indicating the magnitude of charge of the electrostatic antenna, but the determination unit charges by comparing the detection result of the phase difference detection unit with the threshold value. It may be configured to determine whether or not the unit is charged with a DC voltage.

15 Resistor voltage divider 16 Resistor voltage divider and phase difference zero point adjustment element 17A, 17B Amplifier 17C Differential amplifier 18A, 18B Comparator 19 Logic circuit 21 RC Primary low-pass filter 100 Non-contact type voltage detector 110 Detection circuit 116A, 116B Variable Capacitor 117 Oscillator 118 Phase difference detector 119C Capacitor (DC blocking filter)
R5 resistor (DC blocking filter)
120, 220, 320 Electrostatic antennas 121A, 221A, 321A First detection electrode 121B, 221B, 321B Second detection electrode 122, 222, 322 Connector 123A, 123B, 223A, 223B, 323A, 323B Board 130 Judgment unit 140 Output 324 hinge

Claims (4)

It is a non-contact type voltage detector that detects the charging state of the charging part charged by DC voltage in a non-contact manner.
An electrostatic antenna charged by electrostatic induction and
A detection circuit that detects the charged state of the electrostatic antenna and
A determination unit that determines the charging state of the charging unit to which the electrostatic antenna is brought close to based on the detection result of the detection circuit, and a determination unit.
Equipped with
The electrostatic antenna, possess a first detection electrode which is electrically connected to the input of the detection circuit, and a second detection electrode which are electrically connected to the ground potential of the detection circuit,
Both the first detection electrode and the second detection electrode include a long planar shape portion on one side.
The planar shape portion of the first detection electrode and the planar shape portion of the second detection electrode are close to each other so that they have a V-shape when viewed in the longitudinal direction, and they are close to each other. A non-contact type voltage detector characterized in that the other long side is separated. The first detection electrode and the second detection electrode both include one or more long planar shapes on one side.
The electrostatic antenna is
The long sides of each other so that the planar shape portion of any of the first detection electrodes and the planar shape portion of any of the second detection electrodes have a V shape when viewed in the longitudinal direction. In the first form, in which they are close to each other and the other long sides of each other are separated from each other.
A second embodiment in which the planar shape portion of any of the first detection electrodes and the planar shape portion of any of the second detection electrodes are separated so that the charging portion can be inserted between the two. The non-contact type voltage detector according to claim 1 , wherein the non-contact voltage detector is configured to be deformable. The detection circuit is
The first transmission line that guides the electric charge from the input unit,
The first variable capacitance means connected to the first transmission line and
An oscillator that periodically changes the capacitance of the first variable capacitance means,
Have,
An AC signal whose amplitude changes according to the charging state of the electrostatic antenna due to a change in the capacitance of the first variable capacitance means is generated in the first transmission line.
One of claims 1 to 2 , wherein the determination unit determines the charging state of the charging unit based on the phase of the signal in which the amplitude change of the AC signal is expanded and converted into a phase change. The non-contact type voltage detector described in the section. The detection circuit is
A second transmission line connected in parallel with the first transmission line,
A second variable capacitance means connected to the second transmission line and whose capacitance is periodically changed by the oscillator.
A DC blocking filter that is connected to the second transmission path and blocks the transmission of DC component signals.
A differential amplifier that outputs the difference between the AC signal output to the first transmission line and the AC signal output to the second transmission line, and
Have,
The determination unit determines the charging state of the charging unit to which the electrostatic antenna is brought close to, based on the phase difference between the output of the differential amplifier and the AC signal output to the second transmission line. The non-contact type voltage detector according to claim 3.

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