JP2013157708A - Interface circuit for power line communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the following problem that in connecting pieces of wiring with different balancing, a part of a high frequency signal is converted from a normal mode to a common mode due to the difference in balancing, so that an in-phase component in proportion to a differential component of the high frequency signal is generated and hence radiation noise originally increases in a wiring with high balancing as well.SOLUTION: Pieces of Wiring with different balancing are connected by an interface circuit constructed by connecting a low-frequency power cut-off circuit in which a capacitor is connected with each terminals on the primary and secondary sides of a transformer in parallel to a high-frequency signal cut-off circuit including an inductance.

Description

  The present invention relates to a power line communication interface circuit for connecting wiring in power line communication in which a high frequency signal is superimposed on a distribution line for communication.

  In recent years, power line communication that performs communication by superimposing a high-frequency signal on a distribution line has been put into practical use. Power line communication is expected to spread further in the future because a communication network can be constructed without newly laying dedicated wiring. However, in general, power distribution systems are not designed to be used for communication. Therefore, when communication is performed by superimposing high-frequency signals on the distribution lines, some of the high-frequency signals that are originally transmitted in normal mode are in common mode. There is a case where it is converted into a signal component, and there is a concern about the radio wave interference to the outside due to radiation noise caused by the common mode signal component.

  In order to solve the above problem, conventionally, an interface circuit for the purpose of suppressing a common mode signal component in a wiring connection portion such as an outlet plug has been disclosed (for example, see Patent Document 1). Further, Patent Document 2 discloses a wiring method further including an impedance matching circuit.

  FIG. 7 is a diagram illustrating a conventional cable for a power line communication device described in Patent Document 2. In FIG. In FIG. 7, the outlet plug has a common mode choke circuit having a high impedance with respect to the common mode of the transmission line, and a differential impedance matching circuit in which the differential impedance is matched.

  With this configuration, the differential component of the high-frequency signal in the normal mode transmitted from the power line communication device passes through the outlet plug and is induced on the power line communication device and the wiring because impedance matching is maintained. The common-mode component of the high-frequency signal, which is a common mode, is suppressed because it has a high impedance. As a result, the conventional power line communication device cable described in Patent Document 2 does not affect the differential component of the high-frequency signal that is the original communication signal, and does not affect the differential component of the high-frequency signal. Can be reduced.

JP 2004-266634 A JP 2008-5082 A

  However, if the balance between the distribution lines is different at the connection part of the distribution line, the high-frequency signal is converted from the normal mode to the common mode due to this difference, which is proportional to the voltage of the differential component of the high-frequency signal. Thus, the in-phase component of the high frequency signal is generated. The common-mode component generated here has the same wide bandwidth as the differential component, and if the differential component is large, the common-mode component also becomes large. A mode filter circuit is required.

  In the present invention, in order to solve the above-mentioned problem, even in a connection portion where the balance between the distribution lines is different, by maintaining the balance between the two connected, the balance is poor with respect to the wiring having a good balance. An object of the present invention is to provide an interface circuit for power line communication that can suppress the influence of wiring and reduce the generation of radiation noise in wiring that is originally well balanced.

  In order to solve the above problems, an interface circuit for power line communication according to the present invention includes a low-frequency power cutoff circuit in which capacitors are connected to primary and secondary terminals of a transformer circuit, and a high-frequency signal cutoff circuit including an inductance, Are connected in parallel.

  By providing the power line communication interface circuit of the present invention in a power distribution device such as an outlet plug, it is possible to distribute a well balanced distribution line to a poorly balanced distribution line without performing special construction or setting in consideration of power line communication during installation. Even when wires are connected, conversion from the normal mode to the common mode due to the deterioration of the balance at the connection point can be suppressed, so that generation of radiation noise due to the in-phase component of the high-frequency signal can be suppressed. .

The figure which shows the basic composition of the interface circuit for power line communication in Embodiment 1 The figure which shows the structure of the low frequency electric power cutoff circuit in Embodiment 1. The figure which shows the structure of the high frequency signal cutoff circuit in Embodiment 1 and 2 The figure which shows another structure of the high frequency signal cutoff circuit in Embodiment 1 and 2 The figure which shows the basic composition of the interface circuit for electric power communication lines in Embodiment 2. The figure which shows the structure of the low frequency electric power cutoff circuit in Embodiment 2. The figure which shows the structure of the cable for conventional power line communication apparatuses

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a diagram showing an example of a basic configuration of a power line communication interface circuit 101 according to the first embodiment of the present invention. The power line communication interface circuit 101 shown in FIG. 1 is a two-terminal pair circuit having four terminals 102 to 105, and is parallel to the low frequency power cutoff circuit 106 and the low frequency power cutoff circuit 106. A high-frequency signal cutoff circuit 107 connected is provided. The low-frequency power cut-off circuit 106 is a two-terminal pair circuit that cuts off the in-phase component of the low-frequency power and the high-frequency signal and passes the differential component of the high-frequency signal. The high-frequency signal cut-off circuit 107 is a two-terminal pair circuit, cuts off the high-frequency signal, and passes low-frequency power.

  FIG. 2 is a diagram showing an example of the configuration of the low-frequency power cutoff circuit 106 according to Embodiment 1 of the present invention. The low frequency power cutoff circuit 106 shown in FIG. 2 includes a transformer circuit 205 and capacitors 201 to 204. The primary side terminal pair of the transformer circuit 205 is connected to the terminals 102 and 103 via capacitors 201 and 202, respectively, and the secondary side terminal pair is connected to the terminals 104 and 105 via capacitors 203 and 204, respectively. It is connected.

  FIG. 3 is a diagram showing an example of the configuration of the high-frequency signal cutoff circuit 107 according to Embodiment 1 of the present invention. A high frequency signal cutoff circuit 107 shown in FIG. 3 includes coils 301 and 302. The terminals 102 and 104 are connected via a coil 301, and the terminals 103 and 105 are connected via a coil 302. In the following, referring to FIG. 1C, the power line communication signal in which the low frequency power and the high frequency signal are superimposed is input to the terminals 102 and 103 of the power line communication interface circuit 101 and passes through the power line communication interface circuit 101. The operation when output from the terminals 104 and 105 will be described.

  The power line communication signal is input to both the low frequency power cutoff circuit 106 and the high frequency signal cutoff circuit 107 connected in parallel.

  Since the low-frequency power cutoff circuit 106 has a high-pass filter circuit configuration by the capacitors 201-204, the high-frequency signal passes through the power line communication signal, but the low-frequency power is cut off. Of the high-frequency signal input to the transformer circuit 205 from the terminals 102 and 103 via the capacitors 201 and 202, the differential component passes through the transformer circuit 205 according to the coupling coefficient of the transformer, but the in-phase components cancel each other out with the transformer. Is cut off. The high-frequency signal that has passed through the transformer circuit 205 is output to the terminals 104 and 105 via the capacitors 203 and 204.

  As a result, the balance between the high-frequency signals output from the terminals 104 and 105 is improved as compared with the high-frequency signals included in the power line communication signals input to the terminals 102 and 103. Here, the improvement of the balance means that the ratio of the in-phase component to the differential component of the high-frequency signal is reduced.

  The coils 301 and 302 of the high-frequency signal cut-off circuit 107 have a property that the impedance is low for a component having a low frequency and the impedance is high for a component having a high frequency. Therefore, the high frequency signal cutoff circuit 107 cuts off the input high frequency signal and transmits low frequency power.

  Thereafter, the differential component of the high-frequency signal that has passed through the low-frequency power cutoff circuit 106 and the low-frequency power that has passed through the high-frequency signal cutoff circuit 107 are superimposed.

  In this way, only the in-phase component of the high-frequency signal is removed from the power line communication signal passing through the power line communication interface circuit. When the power line communication interface circuit of the present invention is used, the in-phase component of the high-frequency signal that causes radiation noise can be cut off. Therefore, a distribution line with good balance is connected to a distribution line with poor balance. Even in this case, it is possible to construct a power line communication system that can prevent deterioration of the balance of the distribution lines and suppress radio wave interference due to generation of radiation noise.

  In the example of the configuration of the low-frequency power cutoff circuit 106 and the high-frequency signal cutoff circuit 107 according to the present embodiment, the respective configurations are symmetrical on the input side and the output side, and the interface circuit for power line communication is also used. The configuration is symmetrical. Therefore, even if a power line communication signal is input from either of the two terminal pairs, the same effect as described above can be obtained.

  3 shows an example of the high-frequency signal cutoff circuit 107 according to the present embodiment. As shown in FIG. 4, the high-frequency signal cutoff circuit 107 includes coils 401-404 and a capacitor 405, and the terminal 102 And the terminal 104 are connected via coils 401 and 403 connected in series, and the terminal 103 and the terminal 105 are connected via coils 402 and 404 connected in series. The connection portion and the connection portion between the coil 402 and the coil 404 may be configured to be connected by the capacitor 405, and are not limited thereto as long as the configuration can block the high-frequency signal and transmit the low-frequency power.

(Embodiment 2)
FIG. 5 is a diagram illustrating an example of a basic configuration of the power line communication interface circuit 101 according to the second embodiment of the present invention. This configuration shows the second configuration of the low-frequency power cutoff circuit in the power line communication interface circuit of the first embodiment, and only the difference in configuration from the first embodiment will be described. The power line communication interface circuit 101 shown in FIG. 5 includes terminals 102 and 103 on the input terminal side, and terminals 104, 105, and 502 on the output terminal side, and the low frequency power cutoff circuit 501 and the low frequency power cutoff circuit A high-frequency signal cutoff circuit 107 connected in parallel is provided. Here, the terminal 502 is a ground wire grounded to the ground, and with this configuration, three power lines including the ground wire can be connected on the output terminal side.

  FIG. 6 is a diagram showing an example of the configuration of the low-frequency power cutoff circuit 501 according to the second embodiment of the present invention. A low-frequency power cutoff circuit 501 shown in FIG. 6 uses a transformer circuit 605 provided with a midpoint terminal on the secondary side of the transformer, instead of the transformer circuit 205 in the first embodiment. This midpoint terminal is connected to a terminal 502 which is a ground wire.

  With this configuration, the operation is the same as that of the first embodiment in that the differential component of the high-frequency signal that has passed through the low-frequency power cutoff circuit and the low-frequency power that has passed through the high-frequency signal cutoff circuit 107 are superimposed. However, in this embodiment, since the midpoint terminal provided on the secondary side of the transformer circuit 605 is grounded, the low-frequency power cutoff circuit 501 has a configuration in which a ground terminal is provided on the output terminal pair side of the two-terminal pair circuit. Three power lines including a ground line can be connected on the output terminal side.

  In the second embodiment, when the power line to be connected is a three-line power line including a ground line, it is possible to suppress unbalance caused by the ground line. If the two power lines for communication and the ground line are in an electrically asymmetric relationship, they are unbalanced, which causes an in-phase component and causes radiation noise. By adopting a configuration in which the communication signal is superimposed and grounded at the midpoint of the two lines as in the present embodiment, the two power lines and the ground line for communication are in an electrically symmetrical relationship. It becomes possible to suppress radiation noise by making it difficult for the unbalance to occur.

  In addition, the combination of each element, such as a capacitor | condenser, a coil, and a transformer, which the power line communication interface circuit in the embodiment has is appropriately set depending on the implementation environment.

  Here, the implementation environment includes the frequency and voltage of the low frequency power, the frequency of the high frequency signal, and the like. In carrying out the present invention, the frequency of the low frequency power may be 50 Hz, 60 Hz, 0 Hz (direct current) or the like supplied as a commercial power source. Moreover, the voltage of the low frequency electric power can consider the value below several hundred volts supplied as commercial power. Furthermore, the frequency of the high frequency signal may be, for example, a band of 10 kHz or higher, a band of 2 MHz or higher, and the like. All of these values can be determined by the environment in which the present invention is implemented.

  That is, the combination of each element considers the frequency of the low frequency power and the frequency of the high frequency signal, satisfies the cutoff frequency value for separating the low frequency power and the high frequency signal, and determines the voltage, current value, etc. of the commercial power supply. It may be set taking into consideration, and depends on the environment in which the present invention is implemented.

  The interface circuit for power line communication according to the present invention reduces radiation noise caused by deterioration of balance when connecting a power line communication device and its cable at a connection point of a power line such as an outlet terminal or a distribution board. Therefore, it is useful for a power distribution system using power line communication.

DESCRIPTION OF SYMBOLS 101 Power line communication interface circuit 102-105,502 Terminal 106,501 Low frequency power cutoff circuit 107 High frequency signal cutoff circuit 201-204,405 Capacitor 205,605 Transformer circuit 301,302,401-404 Coil

Claims (4)

In power line communication that performs communication by superimposing high-frequency signals and power, an interface circuit for power line communication that connects wiring,
A low-frequency power cutoff circuit that cuts off low-frequency power and passes high-frequency signals;
A high-frequency signal cut-off circuit connected in parallel with the low-frequency power cut-off circuit to cut off the high-frequency signal and pass the low-frequency power;
The low-frequency power cutoff circuit includes a transformer circuit of a two-terminal pair, and a capacitor connected in series to each of a primary side terminal pair and a secondary side terminal pair of the transformer circuit of the two-terminal pair,
Interface circuit for power line communication. The high-frequency signal cutoff circuit is
A first high frequency blocking circuit and a second high frequency blocking circuit each having at least one coil;
The power line communication interface circuit according to claim 1. The high-frequency signal cutoff circuit is
A first high-frequency blocking circuit and a second high-frequency blocking circuit each having two coils connected in series; a connection between the two coils of the first high-frequency blocking circuit; and the second high-frequency blocking circuit A capacitor connecting a connection between the two coils of the blocking circuit;
The power line communication interface circuit according to claim 1. The transformer circuit includes a midpoint terminal on the secondary side of the transformer,
The midpoint terminal is a ground terminal.
The power line communication interface circuit according to claim 1.

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