JP2020077961A - Power line communication filter circuit, power line communication device, and power meter - Google Patents

Abstract

To suppress spurious emission in a power line communication device.SOLUTION: A power line communication filter circuit interposed between a commercial AC power line and a power line communication circuit that performs communication by switching between transmission and reception in time division includes a coupling transformer in which the power line is connected to a primary coil and the power line communication circuit is connected to a secondary coil, a capacitor that is provided in at least one electric path connected to both ends of the primary coil and that blocks the intrusion of commercial AC, an inductor that is connected in parallel to the secondary coil and that attenuates noise of a frequency lower than a frequency band of a communication signal of power line communication propagating through the coupling transformer, and a first resistor connected in series with the inductor.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a power line communication filter circuit, a power line communication device, and a power meter.

Power line communication (PLC: Power Line Communication) is a communication method for transmitting a communication signal using a power line. For example, by plugging PLC modems into outlets at a plurality of locations inside a house, a network can be easily configured between information processing devices such as personal computers connected to the PLC modems.
Therefore, the power line communication may be used for meter reading of the amount of electric power via the network by combining with the smart meter or the like.

  A PLC modem (power line communication device) used for power line communication as described above includes a circuit (hereinafter referred to as a filter circuit) having a filter function for transmitting and receiving a communication signal using the power line while being insulated from the AC voltage of the power line. It is provided (for example, refer to Patent Document 1).

  This filter circuit includes a coupling transformer having a primary coil connected to a power line and a secondary coil connected to a communication circuit, a capacitor connected in series to the primary coil side, the capacitor and the primary coil. And an impedance circuit connected in parallel with the primary coil.

The impedance circuit includes an inductor and the like, and is configured to have a small impedance in a frequency band of noise generated from home electric appliances.
As a result, this filter circuit has, for example, a characteristic of removing noise of several tens of kHz generated from home electric appliances and passing signals in the frequency band (several hundred kHz) used in power line communication. Noise can be suppressed, and appropriate signal transmission / reception can be realized in power line communication.

JP, 2003-134003, A

The power line communication may employ time division duplex (TDD) in which transmission and reception are switched in time division for communication.
As shown in FIG. 6, the PLC modem used in the power line communication adopting the TDD includes a transmission circuit 100, a reception circuit 102, and a filter circuit 108 connected between the transmission / reception circuits 100 and 102 and the power line 106. A switch 104 for switching between transmission and reception is provided. The transmission circuit 100, the reception circuit 102, and the filter circuit 108 are connected to the switch 104. The switch 104 has a function as a switch that switches the connection destination of the filter circuit 108 to either the transmission circuit 100 or the reception circuit 102. The switching unit 104 switches the connection destination of the filter circuit 108 to switch between transmission and reception.

Here, when the switching device 104 switches between transmission and reception, there is a period in which the switching device 104 is not connected to either the transmission circuit 100 or the reception circuit 102.
The impedance of the switch 104 seen from the filter circuit 108 is extremely high during the period in which the switching circuit 104 is not connected to any circuit. Therefore, the energy stored in the inductor of the filter circuit 108 is released, and the energy further propagates to the power line side as a spurious (unwanted wave), and the spurious propagated to the power line may be radiated from the power line.
Such spurious may be a frequency outside the frequency band defined by the standard, and it is not preferable to emit it.
Therefore, in the power line communication by TDD, a measure for suppressing the generation of spurious is desired.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a technique capable of suppressing the generation of spurious.

  A power line communication filter circuit according to an embodiment is a power line communication filter circuit that is interposed between a commercial AC power line and a power line communication circuit that performs communication by switching transmission and reception in time division, A coupling transformer in which the power line is connected to a primary coil and the power line communication circuit is connected to a secondary coil, and at least one electric path connected to both ends of the primary coil are provided, and commercial AC current invades. And a capacitor connected in parallel to the secondary coil for attenuating noise having a frequency lower than a frequency band of a communication signal of power line communication propagating through the coupling transformer, and a inductor connected in series to the inductor. A first resistor connected to.

  A power line communication device according to another embodiment is a power line communication device that uses a commercial AC power line as a signal transmission path, and a power line communication circuit that performs communication by switching transmission and reception in time division. A coupling transformer having a coil connected to the power line and a secondary coil connected to the communication circuit and at least one electric path connected to both ends of the primary coil are provided to prevent intrusion of commercial alternating current. A capacitor, an inductor connected in parallel to the secondary coil, and an inductor for attenuating noise having a frequency lower than a frequency band of a communication signal of power line communication propagating through the coupling transformer, and connected in series to the inductor. And a first resistor.

  A power line communication device according to another embodiment is a power meter equipped with the above power line communication device.

  According to the present invention, generation of spurious can be suppressed.

FIG. 1 is a single-line connection diagram showing, as an example, a connection form of an electric power meter provided in each house of an apartment house. FIG. 2 is a circuit diagram focusing on one power meter. FIG. 3 is a diagram showing an internal circuit configuration of the PLC modem. FIG. 4A is a graph showing the output of the comparative example product in the time domain. FIG. 4B is a graph showing the output of the example product in the time domain. FIG. 5 is a graph showing the outputs of the example product and the comparative example product in the frequency domain. FIG. 6 is a diagram showing a main part of a conventional PLC modem.

First, the contents of the embodiment will be listed and described.
[Outline of Embodiment]
(1) A power line communication filter circuit according to one embodiment is a power line communication filter circuit that is interposed between a commercial AC power line and a power line communication circuit that performs communication by switching between transmission and reception in time division. And a commercial transformer provided with a coupling transformer in which the power line is connected to a primary coil and the power line communication circuit is connected to a secondary coil, and at least one electric path connected to both ends of the primary coil. A capacitor for blocking current intrusion; an inductor connected in parallel to the secondary coil for attenuating noise of a frequency lower than a frequency band of a communication signal of power line communication propagating through the coupling transformer; A first resistor connected in series with the inductor.

According to the power line communication filter circuit having the above configuration, when the energy stored in the inductor is released from the inductor when the power line communication circuit switches between transmission and reception, the first line connected to the inductor in series The energy can be consumed by the resistance.
As a result, it is possible to suppress the energy that propagates to the power line side and causes spurious, and it is possible to suppress the generation of spurious.

(2) In the power line communication filter circuit, it is preferable that a second resistor connected in parallel to the secondary coil is further provided between the inductor and the power line communication circuit.
In this case, the impedance of the line connecting the secondary coil and the power line communication circuit can be stabilized, and the energy released from the inductor can be consumed by the second resistor, so that the spurious emission is effectively suppressed. be able to.

(3) In the above power line communication filter circuit, the inductance of the inductor is preferably in the range of 10 μH to 100 μH.
In this case, an excellent noise suppressing effect was obtained with respect to noise of about 20 kHz which is often generated from home appliances such as electromagnetic induction heating cookware.
Further, by setting the frequency within this range, it is possible to suppress the signal attenuation of the power line communication due to the presence of the inductor. That is, if the inductance is less than 10 μH, the identification of communication signals in power line communication is affected. When the inductance exceeds 100 μH, the noise suppressing effect is reduced. Within this range, 33 μH and its vicinity are particularly preferable.

(4) In the power line communication filter circuit, the resistance value of the first resistor is preferably in the range of 1Ω to 5Ω.
When the resistance value of the first resistor is less than 1Ω, the effect of consuming the energy emitted from the inductor becomes low and the spurious suppression effect is affected. In addition, when the resistance value of the first resistor exceeds 5Ω, the noise reduction effect of the inductor decreases. By setting the resistance value of the first resistor in the range of 1Ω to 5Ω, the energy emitted from the inductor can be appropriately consumed.

(5) A power line communication device according to another embodiment is a power line communication device using a commercial AC power line as a signal transmission path, and a power line communication circuit that performs communication by switching transmission and reception in time division. A coupling transformer in which the power line is connected to a secondary coil and the communication circuit is connected to a secondary coil, and at least one electric path connected to both ends of the primary coil are provided to prevent intrusion of commercial alternating current. Connected in parallel to the secondary coil, an inductor for attenuating noise of a frequency lower than a frequency band of a communication signal of power line communication propagating through the coupling transformer, and connected in series to the inductor. And a first resistance that is set.

(6) A power meter according to another embodiment is a power meter equipped with the power line communication device according to (5) above.

[Details of Embodiment]
Hereinafter, preferred embodiments will be described with reference to the drawings.
It should be noted that at least a part of the embodiments described below may be arbitrarily combined.

<< Example of network configuration using power line communication >>
First, a configuration example of a network using power line communication will be described. Here, the frequency band of the communication signal of the power line communication is 150 kHz to 400 kHz.

  FIG. 1 is a single line connection diagram showing, as an example, a connection form of a power meter 2 with a communication function provided in each house of an apartment house 1. This electric power meter 2 is a so-called smart meter, and is referred to as SM in the figure. In the figure, a 6.6 kV high-voltage cable 3 is drawn into the electric room of the housing complex 1. The transformer 4 transforms 6.6 kV into a low voltage of 200/100 V (single-phase three-wire). The electric power meters 2 (only part of which is shown) for the total number of units are connected to the distribution lines 5a, 5b, 5c of the low-voltage multiple systems. A concentrator 6 incorporating a power line communication device (hereinafter, referred to as PLC modem) is connected to the low voltage side of the transformer 4.

  The power meter 2 has a built-in PLC modem and can perform power line communication with the concentrator 6. The concentrator 6 and each power meter 2 constitute a local network for power line communication under the umbrella of the transformer 4, using the low-voltage distribution line 5 (5a, 5b, 5c) as a signal transmission path. Utilizing this network, meter reading data of the amount of power from each power meter 2 can be collected in the concentrator 6. The concentrator 6 can further transmit meter-reading data to a power supply source (electric power company) by optical communication or wireless communication.

On the other hand, the area beyond the power meter 2 is the customer 7 or the indoor wiring of each house. A distribution board 71 is connected to the power meter 2, and indoor power lines are wired from the distribution board 71 to a large number (only three shown) of outlets 72, 73, 74.
Here, for example, it is assumed that the outlet 72 is connected with an IH cooking appliance (electromagnetic induction heating cooking appliance) 76.

  Further, a HEMS (Home Energy Management System) gateway 75 may be connected to the distribution board 71 or an outlet (for example, 73, 74) as an energy management device in the customer 7. The HEMS gateway 75 can perform wired or wireless communication with the power meter 2 for the consumer. Here, for example, the HEMS gateway 75 has a built-in PLC modem and can perform power line communication with the power meter 2. That is, the power meter 2 can communicate with the concentrator 6 and also with the HEMS gateway 75.

  FIG. 2 is a circuit diagram focusing on one power meter 2. The same applies to the other power meters 2. The parts corresponding to those in FIG. 1 are designated by the same reference numerals. In FIG. 2, the power meter 2 includes a weighing unit 2A, a storage unit 2B, and a PLC modem 2C. It should be noted that the weighing unit 2A, the storage unit 2B, and the PLC modem 2C need only be present as functional units, and need not be physically separated in this way. For example, they may be integrated with each other arbitrarily.

The voltage lines L1 and L2 of the distribution line 5 and the neutral line N are connected to the metering unit 2A. The voltage lines L1 and L2 and the neutral line N pass through the metering unit 2A and become the indoor wiring 5x. 2 A of measurement parts measure electric energy based on the electric current and voltage which pass.
The metering unit 2A stores information on the measured power amount in the storage unit 2B.
The PLC modem 2C acquires, from the storage unit 2B, information necessary for communication in addition to the information on the power amount. The PLC modem 2C is connected to, for example, the voltage lines L1 and L2 by the electric path 2D, and can transmit and receive a communication signal for power line communication via the distribution line 5 and the indoor wiring 5x.
The PLC modem 2C can send a communication signal including power amount information and necessary information to the concentrator 6. The concentrator 6 receives the communication signal transmitted via the distribution line 5, and acquires the information of the electric energy from each electric power meter 2.

For example, by performing the process of polling a specific electric power meter 2 from the concentrator 6 and transmitting the electric energy information to the concentrator 6 for each electric power meter 2, the electric power information is collected. It can be performed.
The concentrator 6 can communicate with the power supply source 8 via a WAN (Wide Area Network) 9 using, for example, an optical fiber or a mobile radio (3G).

Here, returning to FIG. 1, as described above, it is known that the IH cooking appliance 76 generally generates noise of about 20 kHz. Since this noise propagates along the power line, there is a possibility that good power line communication may be hindered by the PLC modem built in the HEMS gateway 75 and the PLC modem 2C of the power meter 2. It may also affect the PLC modem built in the concentrator 6.
Note that the PLC modem includes, for example, a circuit mounted on a board, an independent finished product unit, and various forms.

<< Circuit configuration of PLC modem >>
FIG. 3 is a diagram showing an internal circuit configuration of the PLC modem 2C described above. The HEMS gateway 75 and the PLC modem built in the concentrator 6 have the same internal circuit configuration.

In FIG. 3, the PLC modem 2C mainly includes a filter circuit 30 and a communication circuit 32. Note that other known details of the PLC modem 2C will be omitted.
The filter circuit 30 is provided between the distribution line 5 (voltage lines L1 and L2) and the communication circuit 32. Therefore, the communication circuit 32 transmits and receives a communication signal via the filter circuit 30.

The communication circuit 32 performs power line communication with the concentrator 6 by TDD that performs transmission by switching between transmission and reception in time division. Therefore, the transmission period and the reception period in the communication circuit 32 are alternately assigned in advance on the time axis.
The communication circuit 32 includes a transmission circuit 48, a reception circuit 50, and a switch 52.
The transmission circuit 48 has a function of transmitting a communication signal to the concentrator 6. The receiving circuit 50 has a function of receiving a communication signal transmitted to the own modem 2C.

The filter circuit 30 is connected to the switch 52 via a signal line 54. Further, the transmission circuit 48 and the reception circuit 50 are connected to the switch 52.
The switch 52 has a function as a switch that switches the connection destination of the filter circuit 30 to either the transmission circuit 48 or the reception circuit 50.
The switch 52 connects the filter circuit 30 and the transmission circuit 48 and disconnects the reception circuit 50 during the transmission period. Further, the switch 52 connects the filter circuit 30 and the reception circuit 50 and disconnects the transmission circuit 48 during the reception period.

  The filter circuit 30 includes capacitors 34 and 36 and a coupling transformer 38. The coupling transformer 38 includes a primary coil 38p and a secondary coil 38s. The coupling transformer 38 transforms the voltage (200V) on the primary coil 38p side into several volts. The communication circuit 32 is connected to the secondary coil 38s side.

Power lines (here, voltage lines L1 and L2) are connected to both ends of the primary coil 38p of the coupling transformer 38 via capacitors 34 and 36, respectively. That is, the capacitors 34 and 36 are inserted in series with respect to each of the two power lines. Note that one of the capacitors 34 and 36 can be omitted.
The inductance of the primary coil 38p is, for example, about 600 μH.

The filter circuit 30 further includes an inductor 40, a first resistor 42, a second resistor 44, and a transient voltage suppression element 46 on the secondary coil 38s side.
The inductor 40 is connected in parallel with the secondary coil 38s.
The first resistor 42 is connected to the inductor 40 in series. The resistance value of the first resistor 42 is set according to the inductance of the inductor 40, but is set to 2Ω in the present embodiment.
In this embodiment, the inductance of the inductor 40 is set to 33 μH.

  The second resistor 44 is closer to the communication circuit 32 than the inductor 40 and the first resistor 42, and is connected in parallel to the secondary coil 38s. The second resistor 44 stabilizes the impedance of the line connecting the secondary coil 38s and the communication circuit 32. The resistance value of the second resistor 44 is set to, for example, 100Ω and its vicinity.

  The transient voltage suppressor 46 (hereinafter also referred to as TVS (Transient Voltage Suppressor) 46) is closer to the communication circuit 32 than the second resistor 44 and is connected in parallel to the secondary coil 38s. The TVS 46 has a function of suppressing a transient voltage, and is configured by, for example, a pair of Zener diodes connected in series with their polarities facing each other.

In the filter circuit 30, the capacitors 34 and 36 function as a high-pass filter and prevent intrusion of commercial alternating current of 50 Hz or 60 Hz from the power line side. On the other hand, a communication signal (frequency band: 150 kHz to 400 kHz) of power line communication having a much higher frequency than that of commercial alternating current and other noises pass through the capacitors 34 and 36. The capacitance of the capacitors 34 and 36 is preferably 0.1 μF to 0.5 μF, for example.
The communication signal and other noises that have passed through the capacitors 34 and 36 are given to the coupling transformer 38.

The inductor 40 functions as a relative high pass filter in the high frequency region.
Of the signals and noise transmitted from the primary coil 38p side of the coupling transformer 38 to the secondary coil 38s side, noise of about 20 kHz generated from the IH cooking appliance 76 is cut off (or greatly attenuated) by the inductor 40. On the other hand, on the other hand, the communication signal of the power line communication whose frequency is higher than the noise is guided to the communication circuit 32 without being affected.
By appropriately setting the cutoff frequency, the frequency band to be attenuated can be widened to some extent, so that even noise of 30 kHz can be sufficiently attenuated.

  As the inductance of the inductor 40 that exerts such a filter function, 33 μH and its vicinity (for example, ± 10%) were particularly suitable. When the allowable range of the inductance is specified from the viewpoint of not affecting the identification of the communication signal of the power line communication, it is 10 μH to 100 μH. That is, if the inductance is less than 10 μH, the identification of communication signals is affected. Further, if the inductance exceeds 100 μH, the noise suppressing effect decreases.

  As described above, according to the PLC modem 2C including the filter circuit 30, noise having a frequency lower than the frequency band of the communication signal, for example, noise of electromagnetic induction heating and cooking equipment is blocked by the inductor 40 as a filter. The inflow of the noise into the communication circuit 32 is suppressed. Therefore, the influence of the noise on the PLC modem 2C can be suppressed.

  Further, by setting the inductance of the inductor 40 within the range of 10 μH to 100 μH, an excellent noise suppressing effect was obtained with respect to the noise of about 20 kHz which is often generated by the IH cooking utensil 76. Further, by setting the frequency within this range, it is possible to suppress the attenuation of the communication signal of the power line communication due to the presence of the inductor 40. As described above, 33 μH and its vicinity are particularly preferable within this range.

  Moreover, even if the electric power meter 2 equipped with such a PLC modem 2C receives noise from the IH cooking utensil in the consumer 7, the influence thereof can be suppressed, so that communication with the concentrator 6 and demand Communication with the HEMS gateway 75 in the house 7 is not hindered.

<< About spurious (unwanted wave) >>
The PLC modem 2C (the communication circuit 32 thereof) of the present embodiment performs power line communication by TDD as described above.
The switching device 52 in FIG. 3 switches the connection destination of the filter circuit 30 to either the transmission circuit 48 or the reception circuit 50 each time the transmission period and the reception period are switched. Therefore, at the timing when the switch 52 switches the connection destination of the filter circuit 30, there is a period in which the filter circuit 30 is not connected to either the transmission circuit 48 or the reception circuit 50.

The impedance of the switch 52 seen from the filter circuit 30 is extremely high during the period in which the switching circuit 52 is not connected to any circuit. Therefore, the energy stored in the inductor 40 is released.
At this time, the first resistor 42 connected in series with the inductor 40 consumes the energy emitted from the inductor 40.

For example, if the energy released from the inductor 40 is not consumed by the first resistor 42 due to a short circuit of the first resistor 42, the energy is filtered by the capacitance component of the filter circuit 30 such as the TVS 46. The energy is accumulated in the circuit 30, and the energy further propagates to the power line side as spurious.
The spurious propagated to the power line side may be radiated from the power line or the like.

On the other hand, according to the present embodiment, when the energy stored in the inductor 40 is released from the inductor 40 when the communication circuit 32 switches between the transmission and the reception, the inductor connected in series to the inductor 40. The energy can be consumed by one resistor 42.
As a result, it is possible to suppress the energy that propagates to the power line side and causes spurious, and it is possible to suppress the generation of spurious.

In the present embodiment, the resistance value of the first resistor 42 is set to 2Ω, but the resistance value of the first resistor 42 may be in the range of 1Ω to 5Ω.
When the resistance value of the first resistor 42 is less than 1Ω, the effect of consuming the energy emitted from the inductor 40 is reduced, and the spurious suppression effect is affected. If the resistance value of the first resistor 42 exceeds 5Ω, the noise reduction effect of the inductor 40 is reduced. By setting the resistance value of the first resistor 42 in the range of 1Ω to 5Ω, the energy emitted from the inductor 40 can be appropriately consumed. Within this range, 2Ω and its vicinity are particularly preferable.

  In addition, in the present embodiment, a second resistor 44 connected in parallel to the secondary coil 38s is further provided between the inductor 40 and the communication circuit 32, and the inductor 40 is also provided in the second resistor 44. It is possible to consume the energy emitted from the device and effectively suppress the generation of spurious.

  Further, in the present embodiment, since the inductor 40, the first resistor 42, the second resistor 44, and the TVS 46, which are the main elements configuring the filter circuit 30, are provided on the side of the secondary coil 38s, the primary coil 38p. As compared with the case where these elements are provided on the side, the requirement for withstanding voltage is reduced. Therefore, the degree of freedom in design is high, which is advantageous for cost reduction.

Next, the test results performed for verifying the spurious suppression effect in the PLC modem 2C according to the above embodiment will be described.
The verification test was performed by modeling a PLC modem and performing computer simulation using the model.

  The model of the example product in the verification test is the model of the PLC modem 2C shown in FIG. 3, and the model of the comparative example does not include the first resistor 42 and the second resistor 44 (the first resistor 42 is A model of a PLC modem having the same configuration as the PLC modem 2C shown in FIG. 3 is used except that the short circuit is removed and the second resistor 44 is opened and removed.

As the test method, transmission and reception were switched for each of the model of the example product and the model of the comparative example, the output at that time was obtained by computer simulation, and the spurious suppression effect was verified from the output.
The outputs of both models are extracted from points P1 and P2 in the PLC modem 2C shown in FIG.

FIG. 4A is a graph showing the output of the comparative example product in the time domain. In FIG. 4A, the horizontal axis represents time and the vertical axis represents voltage.
As shown in FIG. 4A, a period K in which the filter circuit 30 is not connected to either the transmission circuit 48 or the reception circuit 50 exists between the transmission period and the reception period, which is the timing at which the switch 52 switches. ..

The transmission period in FIG. 4A includes a period in which the communication signal output by the transmission circuit 48 appears as a change in voltage, and a period in which the transmission circuit 48 has a substantially constant voltage because the communication signal does not output. Has been.
Since there is no communication signal transmitted from the concentrator 6 during the reception period in FIG. 4A, the reception period is substantially constant, as in the case where the transmission period is constant.

  Further, it can be seen that the voltage slightly changes during the period K in FIG. 4A. This is the energy emitted from the inductor 40, and when it propagates to the power line side, it becomes a spurious.

FIG. 4B is a graph showing the output of the example product in the time domain.
As shown in FIG. 4B, during the period K in the output of the example product, the voltage is constant as in the constant voltage period and the reception period in the transmission period, and the voltage change in the period K is the output of the example product. Does not appear in.
From this, it is understood that in the example product, the energy released from the inductor 40 is consumed by the first resistor 42 and the second resistor 44, and the energy is suppressed.

  FIG. 5 is a graph showing the outputs of the example product and the comparative example product in the frequency domain. In FIG. 5, the horizontal axis represents frequency and the vertical axis represents power. In FIG. 5, the graph showing the output of the example product and the graph showing the output of the comparative example product are shown in an overlapping manner.

The signal band in FIG. 5 indicates the frequency band of the communication signal and is 150 kHz to 400 kHz.
Within the signal band, the component of the communication signal of power line communication appears as an increase in power. There is no difference in the component of the communication signal between the example product and the comparative example product.

Looking at the adjacent band outside the signal band and adjacent to the high frequency side of the signal band in FIG. 5, the power of the comparative example product appears larger than the power of the example product.
In this adjacent band, the power of the comparative example product, which appears relatively higher than the power of the example product, is the energy emitted from the inductor 40. That is, the voltage change appearing in the period K in FIG. 4A appears as a signal wave having a frequency higher than the frequency band of the communication signal in the frequency domain.

As described above, also from FIG. 5, it is understood that in the example product, the energy emitted from the inductor 40 is consumed by the first resistor 42 and the second resistor 44.
In the comparative example product, energy with a frequency higher than the frequency band of the communication signal is emitted from the inductor 40, and when this energy propagates to the power line side, spurious with a frequency higher than the frequency band of the communication signal is generated.
On the other hand, in the example product, since the energy emitted from the inductor 40 is suppressed by being consumed, the generation of spurious is suppressed.

  As described above, as a result of the verification test, it was confirmed that the PLC modem of the example product can effectively suppress the generation of spurious.

<Other forms>
Although the filter circuit 30 is a part of the PLC modem 2C in the above-described embodiment, the filter circuit 30 may also exist as a power line communication filter that is separate and independent from the PLC modem 2C.
Further, the preferable range of the inductance of the inductor 40 is assumed to be about 20 kHz specific noise generated from the current IH cooker 76, and when the noise frequency changes greatly in the future, the inductance is preferable. The range will change accordingly.
Further, the resistance value of the first resistor 42 and the resistance value of the second resistor 44 are also the same, and the preferable range can be changed according to the inductance of the inductor 40.

《Supplementary note》
It should be understood that the embodiments disclosed this time are exemplifications in all points and not restrictive. The scope of the present invention is defined by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.

1 Apartment 2 Power meter 2A Metering section 2B Storage section 2C PLC modem 2D Electric circuit 3 High voltage cable 4 Transformer 5, 5a, 5b, 5c Distribution line 5x Indoor wiring 6 Concentrator 7 Consumer 8 Power source 9 WAN
30 Filter Circuit 32 Communication Circuit 34, 36 Capacitor 38 Coupling Transformer 38p Primary Coil 38s Secondary Coil 40 Inductor 42 First Resistor 44 Second Resistor 46 Transient Voltage Suppression Element 48 Transmitter Circuit 50 Receiver Circuit 52 Switcher 54 Signal Line 71 Distribution board 72, 73, 74 Outlet 75 HEMS gateway 76 IH cooking appliance 100 Transmission circuit 102 Reception circuit 104 Switcher 106 Power line 108 Filter circuit L1, L2 Voltage line N Neutral line P1, P2 points

Claims (6)

A power line communication filter circuit interposed between a commercial AC power line and a power line communication circuit that performs communication by switching transmission and reception in a time division manner,
A coupling transformer in which the power line is connected to a primary coil and the power line communication circuit is connected to a secondary coil;
A capacitor which is provided in at least one electric path connected to both ends of the primary coil, and which blocks a commercial AC current from entering;
An inductor connected in parallel to the secondary coil for attenuating noise having a frequency lower than a frequency band of a communication signal of power line communication propagating through the coupling transformer;
A filter circuit for power line communication, comprising: a first resistor connected in series to the inductor. The filter circuit for power line communication according to claim 1, further comprising a second resistor connected in parallel to the secondary coil between the inductor and the power line communication circuit. 3. The power line communication filter circuit according to claim 1, wherein the inductance of the inductor is in the range of 10 μH to 100 μH. The power line communication filter circuit according to claim 1, wherein the resistance value of the first resistor is in the range of 1Ω to 5Ω. A power line communication device using a commercial AC power line as a signal transmission path,
A power line communication circuit that performs communication by switching between transmission and reception in time division,
A coupling transformer in which the power line is connected to a primary coil and the communication circuit is connected to a secondary coil;
A capacitor which is provided in at least one electric path connected to both ends of the primary coil, and which blocks a commercial AC current from entering;
An inductor connected in parallel to the secondary coil for attenuating noise having a frequency lower than a frequency band of a communication signal of power line communication propagating through the coupling transformer;
A power line communication device comprising: a first resistor connected in series to the inductor.   A power meter equipped with the power line communication device according to claim 5.

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