JP2005221253A - Signal injection and extraction apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a signal injection and extraction apparatus optimum for performing noncontact injection and extraction of a signal current into and from a conductor through which a current other than the signal current flows. <P>SOLUTION: The signal injection and extraction apparatus is provided with: a ferromagnetic body 2 arranged in the outer circumference of the conductor 300 through which a commercial current (a current of a first frequency) flows; a signal injection and extraction winding 3 (a first winding) and a cancel winding 4 (a second winding) arranged in the ferromagnetic body 2; and an amplifier 5 connected to the cancel winding 4 and capable of amplifying the commercial current flowing through the winding 3. The amplifier 5 is provided with: a filter part 6 for passing the commercial current and interrupting the signal current; an amplifying part 7 serially arranged in the filter part 6; and an impedance element 8 arranged in parallel in the filter part 6 and the amplifying part 7. The current of the first frequency flowing through the cancel winding 4 is amplified, and only a magnetic field by the commercial current impressed on the ferromagnetic body 2 is canceled. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a signal injection extraction device that performs injection / extraction of an electric signal (signal current) without contact with a conductor. In particular, even when a current other than the signal current, such as a power supply current, is flowing through the conductor, the signal current can be more reliably injected / extracted from the conductor, thereby reducing deterioration in communication performance. The present invention relates to a signal injection extraction device that can

  2. Description of the Related Art Conventionally, a signal injection extraction device that performs injection / extraction of electrical signals without contact with a conductor has been used. As such a signal injection extraction device, for example, there is one using a ferrite core and a winding as shown in Patent Document 1. FIG. 2 is an explanatory view schematically showing a configuration of a conventional signal injection extraction apparatus. In the drawings, the same reference numerals denote the same items. The signal injection extraction apparatus 100 shown in FIG. 2 includes a ring-shaped ferrite core 101 arranged so as to surround the outer periphery of the conductor 300, two windings wound around the outer periphery of the core 101, a signal injection extraction winding 102, and a cancel. Winding 103 is provided. The signal injection extraction winding 102 has a signal current transmission device, a signal current reception device, or a transmission / reception device (both not shown) attached, and injects a high frequency signal current into the conductor 300 / to the conductor 300. The signal current to be transmitted is extracted. The cancel winding 103 flows a cancel current for canceling the magnetic field generated in the core 101 by a commercial current having a low frequency (usually 50 Hz or 60 Hz) flowing through the conductor 300.

  For example, when a signal current having a frequency higher than the commercial frequency is injected into the conductor 300 while a commercial current is flowing through the conductor 300, a magnetic field A is generated and applied to the ferrite core 101 by the commercial current. Due to this magnetic field A, an induced current having a frequency equivalent to the commercial frequency flows in the cancel winding 103 in a direction that cancels the magnetic field A. Therefore, the ferrite core 101 is not saturated and magnetized by the magnetic field A generated by the commercial current. . Therefore, when a high-frequency signal current is passed through the signal injection and extraction winding 102, the magnetic field B is generated and applied to the ferrite core 101 by the signal current because the magnetic field A is cancelled. Depending on the magnetic permeability of 101, a high-frequency signal current flows through the conductor 300. That is, a high frequency electrical signal is injected into the conductor 300.

  On the other hand, when the signal current is extracted when a high-frequency signal current is flowing along with the commercial current in the conductor 300, the ferrite core 101 generates and applies the magnetic field A due to the commercial current and the magnetic field B due to the signal current. Is done. However, since the magnetic field A is canceled by the induced current flowing through the cancel winding 103, the ferrite core 101 is not saturated by the commercial current. In addition, due to the inductance of the winding 103 and the effective increase of the electrical resistance of the winding 103 due to the skin effect, generation of an induced current in the direction that cancels the magnetic field B in the cancel winding 103 is suppressed. Therefore, a high-frequency signal current flows through the signal injection and extraction winding 102 in accordance with the magnetic field B and the magnetic permeability of the core 101. That is, a high frequency electrical signal is extracted from the conductor 300.

  As described above, the signal injection and extraction apparatus can inject / extract a high-frequency signal current at a stable level regardless of the commercial current flowing through the conductor.

Patent Document 1 discloses a signal injection and extraction device in which a current circuit for causing a current of a specific frequency to flow through a winding is connected to both ends of the winding without making the cancel winding short-circuited. This device actively flows a current I ₁ having a specific frequency through the cancel winding, cancels the magnetic field due to the current I ₂ having the same frequency as the current I ₁ flowing through the conductor, and the ferrite core is saturated and magnetized by the current I _2. It is what suppresses.

JP 2001-319815 A

  However, in the conventional signal injection and extraction apparatus, an induced current in a direction that cancels the magnetic field A applied by the high-frequency signal current is generated in the cancel winding, which may deteriorate the communication performance. The signal injection extraction device shown in FIG. 2 is configured to suppress the generation of an induced current in the direction that cancels out the magnetic field A by the inductance of the cancel winding 103 and the skin effect, so depending on the inductance and the skin effect, Occurrence may not be sufficiently suppressed. Therefore, there is a demand for an apparatus that can more reliably inject / extract signal current by canceling the magnetic field due to commercial current without canceling the magnetic field due to signal current.

  Accordingly, a main object of the present invention is to provide a signal injection extraction apparatus that can perform injection / extraction of a signal current more reliably even when a current having a frequency different from that of the signal current flows through a conductor.

  The present invention includes an amplifier circuit that amplifies a current having a frequency different from that of the signal current, and achieves the above object by canceling out the magnetic field generated by the current having a frequency different from that of the signal current.

  That is, the signal injection extraction device of the present invention includes a ferromagnetic body disposed on the outer periphery of a conductor through which a current of a first frequency flows, and a signal current of a second frequency that is disposed on the ferromagnetic body and is different from the first frequency. A first winding for injecting into the conductor / extracting a signal current of a second frequency from the conductor, a second winding disposed in the ferromagnetic material and through which the current of the first frequency flows, and the second And an amplifier circuit connected to the winding. The amplifying circuit includes a filter unit that allows a first frequency current to pass therethrough and a second frequency signal current to be cut off, an amplifying unit that is arranged in series with the filter unit, and a parallel to the filter unit and the amplifying unit. And an impedance element disposed on the substrate. The present invention will be described in detail below.

  The first frequency and the second frequency are different. In particular, since the second frequency is used as a signal current, it is preferable that the second frequency be higher than the first frequency. That is, it is preferable that the first frequency is a low frequency and the second frequency is a high frequency. In particular, the first frequency includes a commercial frequency. Specifically, 50 Hz or 60 Hz is mentioned, for example. Therefore, a commercial current is mentioned as a current of the first frequency flowing through the conductor. On the other hand, the second frequency is preferably a high frequency excellent in communication characteristics. Specifically, for example, when the conductor is a conductor of a power supply electric wire and performs power line carrier communication for transmitting an electric signal to the electric wire and performing communication, the second frequency is 1.7 MHz to 50 MHz, particularly 1.7 MHz to 30 MHz.

  The ferromagnetic material disposed on the outer periphery of the conductor is preferably a ferrite core having a high magnetic permeability and a low loss characteristic even in a high frequency region. The ferrite core is preferably in a ring shape so that it can be easily placed on the outer periphery of the conductor, and may have an integral structure, but if it is configured by combining a split piece such as a half-cracked piece into a ring shape, it will be easier to place. preferable. The ring shape may be any ring shape having a hole at the center, and is not limited to a circle.

  The first winding and the second winding only have to have a conductor portion through which a current can flow. For example, a commonly used coated wire, enameled wire, bare wire, copper plate, etc. May be used. The cross-sectional area, the number of turns, the length, and the like may be appropriately selected according to the magnitude of the current at the first frequency and the second frequency, the size of the conductor, and the like.

  The most characteristic feature of the present invention is that it includes an amplifier circuit connected to the second winding. This amplifying circuit cancels the first magnetic field applied to the ferromagnet by the first frequency current and hardly cancels (or does not cancel) the second magnetic field applied to the ferromagnet by the second frequency signal current. Thus, the current of the first frequency flowing in the direction to cancel the first magnetic field is specifically amplified. In order to perform such a function, a filter unit and an amplification unit are provided in series, and an impedance element is provided in parallel thereto. In the present invention, the term “amplification” does not only mean increasing a value such as a current value, but also includes a function as a so-called buffer that can pass the input of the amplifier circuit one-to-one. However, it means that the function of the amplifier circuit is widely used.

  The filter unit is connected to the second winding to cut off the signal current of the second frequency and pass the current of the first frequency. As such a filter unit, for example, when the first frequency is a low frequency and the second frequency is a high frequency, a low-pass filter that allows a low-frequency current to pass through, or a band elimination that blocks a current in a specific frequency band. For example, a nation filter. Examples of the low-pass filter include an RC filter that combines a resistor and a capacitor. In the case of an RC filter, R (resistance value) is set so that the current value of the first frequency passing through the filter section is sufficiently smaller than the current value of the first frequency passing through the impedance element provided in parallel with the filter section. ) Is preferably sufficiently large.

  The impedance element has a large impedance for the signal current of the second frequency, that is, a small impedance for the current of the first frequency. By providing such an element, the current of the first frequency is easily passed through the amplifier circuit, and the signal current of the second frequency is less likely to flow through the amplifier circuit. Examples of the impedance element include a resistor, an inductor, and a combination of a resistor and an inductor.

  The amplifying unit amplifies the current of the first frequency that has passed through the impedance element according to the amplification factor, in order to increase the input resistance on the input side (filter unit side), the output resistance on the output side, and the amplification factor. There are things that have a power source. A general operational amplifier may be used. The filter unit and the amplification unit are arranged in the order of the filter unit and the amplification unit when viewed from the ferromagnetic material side.

  With the above configuration, the output voltage generated at both ends of the filter section with respect to the current of the first frequency flowing through the second winding appears as it is, so the current of the first frequency that has passed through the impedance element is amplified. It can be amplified in the part. That is, the current of the first frequency input to the amplifier circuit flows directly into the amplifier, passes through the amplifier, and flows to the second winding. On the other hand, the current of the second frequency is made difficult to flow through the amplifier circuit by the impedance element and is blocked by the filter unit. With this configuration, the output voltage generated at both ends of the filter unit becomes very small compared to the input voltage, and the current of the second frequency that has passed through the impedance element is hardly amplified in the amplification unit.

  The present invention having the above configuration efficiently cancels the magnetic field caused by the current of the first frequency applied to the conductor by the amplifier circuit, but hardly cancels the magnetic field caused by the current of the second frequency. Therefore, the present invention can more reliably inject / extract the signal current of the second frequency with respect to the conductor through which the current of the first frequency flows, and can reduce the deterioration of the communication performance.

  Embodiments of the present invention will be described below.

  FIG. 1A is a schematic configuration diagram schematically showing a signal injection extraction device of the present invention, FIG. 1B is a circuit diagram of a filter unit of the device, and FIG. 1C is an amplifier circuit diagram of the device. The signal injection extraction device 1 of the present invention performs injection / extraction of electrical signals in a non-contact manner with respect to the conductor 300, and includes a ferromagnetic body 2 disposed on the outer periphery of the conductor 300 and a signal disposed on the ferromagnetic body 2. An injection extraction winding (first winding) 3 and a cancellation winding (second winding) 4 and an amplification circuit 5 connected to the cancellation winding 4 are provided. In this example, the first frequency is a commercial frequency (usually 50 Hz or 60 Hz), the second frequency is 1.7 MHz, the commercial frequency current is called a commercial current, and the 1.7 MHz current is simply called a signal current. This will be described in detail below.

(Ferromagnetic material)
In this example, the ferromagnetic body 2 is a ferrite core that is formed into a ring shape by combining half-arc pieces.

(Signal injection extraction winding)
The signal injection extraction winding 3 extracts a signal current flowing through the conductor 300 and injects a signal current from a signal transmission device (not shown) attached separately into the conductor 300. In this example, a commonly used covered electric wire was used, and two-turn winding was used. The extraction of the signal current by the winding 3 is performed as follows. A magnetic field is generated and applied to the ferromagnetic material 2 by the signal current flowing through the conductor 300, and a high-frequency (1.7 MHz) current (inductive current) is applied to the winding 3 according to the magnetic field and the magnetic permeability of the ferromagnetic material 2. Flows. That is, an electrical signal is extracted. On the other hand, the signal current is injected by the winding 3 as follows. By applying a signal current from a signal transmission device (not shown) separately attached to the winding 3 to the winding 3, a magnetic field is generated and applied to the ferromagnetic body 2. A high frequency (1.7 MHz) current (inductive current) flows through the conductor 300 according to the magnetic field and the magnetic permeability of the ferromagnetic body 2. That is, an electrical signal is injected.

(Cancel winding)
When a current having a frequency different from the signal current (current of the first frequency; in this example, a commercial current) flows through the conductor 300, a magnetic field is generated in the ferromagnetic body 2 by the commercial current and applied. When the ferromagnetic material 2 is saturated by this magnetic field, it becomes difficult or impossible to inject / extract the signal current. Therefore, in order to prevent the ferromagnetic material 2 from being saturated and magnetized by the commercial current flowing through the conductor 300, a cancel current is passed in a direction to cancel the magnetic field generated by the commercial current. In the present invention, the cancel winding 4 is provided as a member for passing the cancel current. In this example, a commonly used covered electric wire was used, and one turn was used.

(Amplifier circuit)
<Overall configuration>
The present invention particularly cancels the magnetic field (first magnetic field) caused by the commercial current applied to the conductor and cancels the magnetic field caused by the signal current applied to the conductor (second magnetic field). An amplifying circuit 5 for amplifying a commercial frequency current flowing through the wire 4 and canceling the first magnetic field more reliably is connected to the cancel winding 4. The amplifier circuit 5 includes a filter unit 6, an amplifier unit 7 arranged in series with the filter unit 6, and an impedance element 8 arranged in parallel with the filter unit 6 and the amplifier unit 7.

<Filter section>
The filter unit 6 allows an induced current (current of commercial frequency) generated by the first magnetic field generated by the commercial current flowing in the conductor 300 to pass, and an induced current (1.7 MHz or higher) generated by the signal current flowing in the conductor 300. Current). In this example, a low-pass filter that allows a low-frequency current to pass and blocks a high-frequency current is used. Specifically, the resistor R ₁ and the capacitor C are provided. With this configuration, as shown in FIG. 1 (B), the input voltage is V _i , the voltage appearing across the capacitor C is V _A , the capacitance C _A of the capacitor C, the angular frequency is ω, and the resistance value of the resistor R ₁ is R Then, the amplification degree V _A / V _i of the input voltage V _i is expressed as follows.

Therefore, for example, if R = 1 kΩ, C _A = 0.1 μF, and the commercial frequency is 50 Hz, the amplification factor is V _1A / V _i ≈1.0 with respect to the commercial frequency. Therefore, V _1A ≈V _i , and when a commercial frequency current flows through the filter unit 6, the voltage V _1A across the capacitor C appears as the input voltage V _i is almost as it is. On the other hand, when the signal frequency is 1.7 MHz, the amplification degree is V _2A / V _i ≈0.0009 with respect to this frequency. Therefore, when V _2A ≈0 and a 1.7 MHz current flows through the filter unit 6, the voltage V _2A across the capacitor C hardly occurs. That is, at a current having a low frequency, a voltage is generated at both ends of the filter unit 6 (capacitor C), and at a current having a high frequency, a voltage is hardly generated at both ends of the filter unit 6 (capacitor C).

<Amplification unit>
The amplifying unit 7 amplifies an induced current (current of commercial frequency) due to the first magnetic field generated by the commercial current flowing through the conductor 300, and is aligned with the filter unit 6 and the amplifying unit 7 when viewed from the ferromagnetic material 2 side. In addition, the filter unit 6 is provided in series. In this example, the amplifying unit 7 includes an input resistor R ₂ on the input side (filter unit 6 side), an output resistor R ₃ on the output side, and a power source 7a for increasing the amplification degree. With this configuration, assuming that the voltage generated at the input resistor R ₂ is V _A , the amplification factor of the power supply 7a is A, and the voltage (output voltage) appearing at both ends of the amplifier 7 is V _o , the output voltage V _o is V _o = -A * V _A That is, the output voltage V _o changes according to the voltage (V _A ) generated at the input resistor R ₂ . For example, similarly to the _{R = 1kΩ, C A = 0.1μF} , the commercial frequency is 50Hz, V _1A ≒ V _i from the output voltage due to the commercial frequency current _{V 1o = (- A) *} V 1A = (- A) * V _i On the other hand, when the signal frequency is 1.7 MHz, the output voltage V _2o = 0 due to the current of 1.7 MHz is obtained from V _{2A ≈0} .

<Impedance element>
The impedance element 8 is provided in parallel with the filter unit 6 and the amplification unit 7. Although the impedance element 8 is a resistor in this example, it may be an inductor or a combination of a resistor and an inductor. That is, the impedance element 8 has a large resistance to the induced current (current of 1.7 MHz or more) caused by the second magnetic field generated by the signal current flowing through the conductor 300, and is induced by the first magnetic field generated by the commercial current flowing through the conductor 300. What has low resistance to current (current at commercial frequency) is preferable.

A behavior when a commercial frequency current I ₁ and a 1.7 MHz current I ₂ pass through an amplifier circuit having the above configuration will be described. First, when an induced current (current I ₁ ) due to the first magnetic field applied by the commercial current flowing in the conductor 300 flows in the cancel winding 4, this current I ₁ is generated by the impedance element by the resistor R ₁ of the filter unit 6. It is divided into a current I _1a flowing on the 8 side and a current I _1b flowing on the filter unit 6 side. At this time, when the input voltage is V _i , the output voltage is V _o , the impedance of the impedance element 8 is Z, the amplification degree of the amplification unit 7 is A, and V _1o = (− A) * V _i is used, the current I _1a is expressed as follows. Further, the input impedance Z _1i is expressed as follows. In this example, a resistor R ₁ having a resistance value R such that I _1a >> I _1b is used.

From the above equation, with respect to the current I ₁ of the commercial frequency, it is smaller input impedance Z _1i, current I ₁ is likely to flow to the amplifier circuit. Also, most of the current I ₁ (current I _1a) is passed through the impedance element 8. Then, the current I _{1a that} has passed through the impedance element 8 flows to the cancel winding 4 by the amplification function of the amplification unit 7 as described above. That is, the current I ₁ flows through the cancel winding 4 almost as it is by the amplifier circuit. With this current I _1a , the magnetic field due to the commercial current flowing through the conductor 300 can be canceled out.

On the other hand, when a 1.7 MHz current (current I ₂ ) due to the second magnetic field generated by the signal current flowing in the conductor 300 flows in the cancel winding 4, the current I _2a flowing in the impedance element 8 side in the same manner as the current I ₁ described above. And current I _2b flowing to the filter unit 6 side. At this time, the current I _2a is expressed as follows using the above V _2o = 0. Further, the input impedance Z _2i = Z.

As described above, since the input impedance Z _2i is large with respect to the high-frequency current I ₂ , the current I ₂ is difficult to flow through the amplifier circuit 5. That is, the current I ₂ hardly flows to the cancel winding 4 by the amplifier circuit. Therefore, the current I ₂ hardly cancels out the magnetic field due to the 1.7 MHz current flowing through the conductor 300 or not at all.

  As described above, the present invention can cancel the magnetic field caused by the current other than the signal frequency flowing through the conductor in the amplifier circuit and can suppress the magnetic field caused by the signal current from being canceled by the amplifier circuit. Therefore, according to the present invention, signal current can be injected / extracted more reliably, and deterioration of communication characteristics can be effectively suppressed.

  The present invention is optimal for injecting / extracting a signal current to / from a conductor when a current having a frequency different from that of the signal current flows through the conductor, for example, when performing power line carrier communication.

It is an explanatory diagram showing an outline of the signal injection extraction device of the present invention, (A) is an overall configuration diagram, (B) is a circuit diagram of a filter portion of the device, (C) is an amplifier circuit diagram of the device is there. It is explanatory drawing which shows typically the structure of the conventional signal injection apparatus.

Explanation of symbols

1 Signal injection extraction device 2 Ferromagnetic material 3 Signal injection extraction winding 4 Canceling winding
5 Amplifier 6 Filter 7 Amplifier 7a Power supply 8 Impedance element
100 Signal injection extraction device 101 Ferrite core 102 Signal injection extraction winding
103 Cancel winding 104 Current generation circuit 300 Conductor

Claims (3)

A ferromagnetic body disposed on the outer periphery of a conductor through which a current of a first frequency flows;
A first winding disposed in the ferromagnetic body for injecting a signal current of a second frequency different from the first frequency into the conductor / extracting a signal current of a second frequency from the conductor;
A second winding disposed in the ferromagnetic body and through which the current of the first frequency flows;
An amplification circuit connected to the second winding,
The amplifier circuit is
A filter section for passing a current at a first frequency and blocking a signal current at a second frequency;
An amplification unit arranged in series with the filter unit;
An apparatus for extracting and injecting signals, comprising: an impedance element arranged in parallel with the filter unit and the amplification unit.   2. The signal injection extraction apparatus according to claim 1, wherein the current of the first frequency is a commercial current, and the second frequency is a frequency higher than the commercial frequency.   2. The signal injection extraction apparatus according to claim 1, wherein the second frequency is 1.7 MHz to 50 MHz.

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