JP2007104205A - Power line communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve further excellent characteristics near a passband and in a high-pass stopband while suppressing increase of the number of components due to increase of the number of poles of a balanced filter. <P>SOLUTION: A filter circuit in a power line communication device is composed of the balanced filter 3 connected to two power lines 2a, 2b in a power line and allowing a prescribed band to pass through, a first imbalanced filter 21 provided between one power line 2a and ground and cutting signals in bands other than the prescribed band, and a second imbalanced filter 22 provided between the other power line 2b and the ground and cutting signals in the bands other than the prescribed band. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power line communication apparatus that uses a power line as a signal transmission line, and particularly relates to a power line communication apparatus including a filter for suppressing unnecessary radiation.

  In recent years, by installing a communication adapter (PLC modem) in an electrical outlet and connecting a data communication device such as a personal computer, a power line communication (PLC) that enables data communication of several Mbps to several hundred Mbps is possible. Power Line Communication) has been proposed. Many buildings have electrical wiring, so you can easily build a local communication network without installing new cables.

  Since the power line is not originally supposed to pass an electric signal of high frequency, there is a problem of leakage radio waves. In view of this, a power line communication device having a filter that suppresses unnecessary radiation by cutting higher harmonic components exceeding a desired frequency band (for example, 4 MHz to 20 MHz) used for power line communication has been considered.

  FIG. 6 is a configuration example of a balanced filter developed for the purpose of suppressing unnecessary radiation in power line communication. In the figure, a balance type filter 3 is connected to a pair of power lines 2a, 2b connected to a commercial power source 1, and a PLC modem 4 is connected via the balance type filter 3, followed by a data communication device. A configuration in which 5 is connected is shown.

  The balanced filter 3 shown in the figure has a three-pole structure in which an LC parallel resonance circuit 6, an LC series resonance circuit 7, and an LC parallel resonance circuit 8 are combined, and a desired frequency band (for example, 4 MHz to 20 MHz) passes therethrough. Realizes the characteristics of a band. Damping resistors 11 and 12 are connected to the power supply side and the modem side of the balanced filter 3 to reduce the Q and secure the band. The power source side of the balanced filter 3 is connected to the secondary side of the signal superimposing transformer 20 via DC cut capacitors 13 and 14 and protective diodes 19a and 19b provided on the power lines 2a and 2b, respectively. The primary side of the power transformer 20 is connected to the commercial power source 1. A capacitor C <b> 1 for preventing a short circuit is inserted between one end on the primary side of the signal superimposing transformer 20 and the commercial power supply 1. The modem side of the balanced filter 3 is connected to the PLC modem 4 via DC cut capacitors 15 and 16 provided on the power lines 2a and 2b, respectively.

FIG. 7 is a filter characteristic diagram of the balanced filter 3 configured as described above. By adjusting the constants of the elements constituting the balanced filter 3, it was possible to obtain the characteristics shown in FIG. The characteristic obtained by the balanced filter 3 having the three-pole structure was a passing characteristic in which the lower frequency side than 4 MHz falls sharply and the higher frequency side than 20 MHz falls gently.
JP 07-245576 A

  However, in order to achieve better characteristics in the vicinity of the pass band and in the high stop band using the balanced filter, the number of poles must be increased. There is a problem that increases and leads to cost increase. Further, since ripple noise in the vicinity of 50 Hz or 60 Hz from the commercial power supply 1 is input to the power lines 2a and 2b, it is desirable to have a blocking characteristic even in such a low frequency band, but this further increases the number of parts.

  The present invention has been made in view of the above points, and can suppress an increase in the number of parts due to an increase in the number of poles of a balanced filter, and achieve better characteristics in the vicinity of the pass band and in the high stop band. An object of the present invention is to provide a power line communication device including a possible filter.

  The power line communication device of the present invention is a first filter that is connected between two electric wires of a power line and passes a predetermined band, and is provided between the one electric wire and the ground and cuts a signal outside the predetermined band. And a second unbalanced filter that is provided between the other electric wire and the ground and cuts a signal outside the predetermined band.

  According to this configuration, the number of elements can be reduced compared to a combination of a plurality of balanced filters by fusing a balanced filter and an unbalanced filter so as to achieve a filter characteristic that achieves a desired passband. Cost can be reduced. In addition, since an unbalanced filter is provided for each of the two wires with respect to the balanced filter, the filter circuit can be designed more easily than when an unbalanced filter is provided for only one of the wires. Also has a stabilizing effect.

  The first and second unbalanced filters can be constituted by bandpass filters having the predetermined band as a pass band. Thereby, the filter characteristics of the high-band stop band and the low-band stop band can be improved.

  The first and second unbalanced filters can be constituted by low-pass filters having a high band side outside the predetermined band as a stop band. As a result, the filter characteristics of the high-band stop band can be improved with a simpler configuration.

  According to the present invention, by integrating the balanced filter and the unbalanced filter, an increase in the number of parts due to an increase in the number of poles of the balanced filter can be suppressed, and further, in the vicinity of the passband and in the high stopband. Good characteristics can be realized.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a configuration diagram of a power line communication apparatus according to an embodiment of the present invention, and mainly shows a filter circuit portion. In addition, the same code | symbol is attached | subjected to the same part as each part of the balance type filter shown in FIG. That is, the power source side of the balanced filter 3 is connected to the secondary side of the signal superimposing transformer 20 via the DC cut capacitors 13 and 14 and the protection diodes 19a and 19b provided on the power lines 2a and 2b, respectively. The primary side of the signal superimposing transformer 20 is connected to the commercial power source 1. The modem side of the unbalanced filters 21 and 22 provided on the modem side of the balanced filter 3 is connected to the PLC modem 4 via DC cut capacitors 15 and 16 provided on the power lines 2a and 2b, respectively. Yes.

  The power line communication apparatus according to the present embodiment has a filter configuration in which the balanced filter 3 and the unbalanced filter shown in FIG. 6 are combined. Since the circuit configuration of the balanced filter 3 has already been described, the description thereof is omitted here, and the configuration of the unbalanced filters 21 and 22 will be mainly described.

  The power line communication apparatus according to the present embodiment has a configuration in which unbalanced filters 21 and 22 are connected to both ends of the power lines 2a and 2b with respect to the PLC modem side end of the balanced filter 3. In other words, the balanced filter 3 and the unbalanced filters 21 and 22 are fused to achieve desired characteristics.

  The unbalanced filter 21 is a so-called π-type bandpass filter. Specifically, both ends of the inductor 43 are connected to the ground via capacitors 44 and 45, and one end of the inductor 43 on the PLC modem side is connected to one end of the DC cut capacitor 15 via a capacitor 46. Both ends of the capacitor 46 are connected to the ground via inductors 48 and 49, respectively.

  The unbalanced filter 22 connected to the other power line 2b is also configured in the same manner as the unbalanced filter 21. That is, both ends of the inductor 51 are connected to the ground via the capacitors 52 and 53, and one end of the inductor 51 on the PLC modem side is connected to one end of the DC cut capacitor 16 via the capacitor 54. Both ends of the capacitor 54 are connected to the ground via inductors 55 and 56.

  FIG. 2 is a schematic diagram of the passband characteristics of the unbalanced filters 21 and 22. As shown in the figure, the stop band is higher than 20 MHz which is the upper limit of the low frequency side and the high frequency side than 4 MHz which is the lower limit of the low frequency side in the desired pass band.

  The filter characteristics shown in FIG. 3 can be realized by adjusting the respective constants by combining the unbalanced filters 21 and 22 having such passband characteristics and the balanced filter 3 having the filter characteristics shown in FIG. It was. Compared with the filter characteristic of only the balanced filter 3 shown in FIG. 6, the high-frequency side is steeper than 20 MHz, and it can be seen that even better characteristics can be realized in the high stop band. Further, a flatter filter characteristic can be realized in a desired band of 4 MHz to 20 MHz. The lower frequency side than 4 MHz shows a steep fall, and the ripple noise existing in the low frequency region caused by the commercial power source 1 can be surely prevented.

  As described above, according to the present embodiment, the unbalanced filters 21 and 22 are connected to both the power lines 2a and 2b, and the desired balance is obtained by combining the balanced filter 3 and the unbalanced filters 21 and 22. Since the passband characteristics have been realized, the number of elements can be greatly reduced compared to the case of combining a number of balanced filters to obtain the same characteristics, and the cost can be reduced. Can do. Further, since the unbalanced filters 21 and 22 are provided for the two power lines 2a and 2b, respectively, with respect to the balanced filter 3, the design of the filter circuit can be made in comparison with the case where the unbalanced filter is provided only for one of the power lines. It is easy and has the effect of stabilizing the filter characteristics.

  In addition, since BPFs that match the desired passband characteristics are used as the unbalanced filters 21 and 22, it is possible to achieve even better characteristics in the high stopband and to reduce the low frequency range generated from the commercial power source 1. Ripple noise can be cut effectively.

  In the above description, π-type BPF is adopted as the unbalanced filters 21 and 22, but the present invention is not limited to π-type BPF. In addition to the π-type, a general T-type BPF can also be used.

  FIG. 4 is a configuration diagram of a modified example in which a T-type BPF is employed as an unbalanced filter. The same filter part as FIG. 1 is mainly shown. An unbalanced filter 41 is connected to one power line 2a, and an unbalanced filter 42 is connected to the other power line 2b.

  The unbalanced filter 41 is a so-called T-type bandpass filter. Specifically, two inductors 23 and 24 are connected in series, and an intermediate point thereof is connected to the ground via a capacitor 25. Two capacitors 26 and 27 are connected in series, and an intermediate point thereof is connected to the ground via an inductor 28. One end of one inductor 24 and one end of one capacitor 26 are connected to form a series circuit including inductors 23 and 24 and capacitors 26 and 27. One end of the inductor 23 is connected to the power line 2 a side of the LC resonance circuit 8 via the resistance element 17. One end of the other capacitor 27 on the PLC modem side is connected to one end of the DC cut capacitor 15.

  Similar to the unbalanced filter 41, the unbalanced filter 42 connected to the other power line 2b is a T-type bandpass filter. That is, the two inductors 31 and 32 are connected in series, and an intermediate point thereof is connected to the ground via the capacitor 33. Two capacitors 34 and 35 are connected in series, and an intermediate point thereof is connected to the ground via an inductor 36. One end of one inductor 32 and one end of one capacitor 34 are connected to form a series circuit including inductors 31 and 32 and capacitors 34 and 35. One end of the inductor 31 is connected to the power line 2 b side of the LC resonance circuit 8 via the resistance element 18. One end of the other capacitor 35 on the PLC modem side is connected to one end of the DC cut capacitor 16.

  As described above, even when the filter is configured by combining the unbalanced filters 41 and 42 made of T-type BPF and the balanced filter 3, when a desired characteristic is realized by combining several balanced filters. In comparison, the number of elements can be reduced. Also, good characteristics can be realized in the vicinity of the pass band and in the high stop band with a small number of parts.

  Further, even if a π-type LPF or a T-type LPF is used as the unbalanced filter (21, 22 or 41, 42), good characteristics can be realized in the vicinity of the pass band and in the high stop band. FIG. 5 shows a characteristic simulation result when a π-type LPF is used as the unbalanced filter. Further, the BPF or LPF that can be used as the unbalanced filter is not limited to the above-described one, and various forms can be applied.

  The present invention is applicable to a power line communication device provided with a filter for suppressing unnecessary radiation from a power line in power line communication.

The block diagram of the filter part of the electric power communication line apparatus which concerns on one embodiment of this invention Characteristics diagram of unbalanced filter shown in FIG. Characteristic diagram of entire filter in power communication line device shown in FIG. Configuration diagram of filter portion of power communication line device according to modification Characteristics of the entire filter when using a π-type unbalanced filter Configuration diagram of a conventional power communication line device Characteristic diagram of entire filter of power communication line device shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Commercial power supply 2a, 2b Power line 3 Balance type filter 4 PLC modem 5 Data communication apparatus 6 LC parallel resonance circuit 7 LC series resonance circuit 8 LC parallel resonance circuit 21, 22, 41, 42 Unbalance type filter 23, 24, 28, 31, 32, 36 Inductor 25, 26, 27, 33, 34, 35 Capacitor

Claims (3)

A balanced filter connected to the two electric wires of the power line and passing a predetermined band;
A first unbalanced filter provided between the one electric wire and the ground for cutting a signal outside the predetermined band;
A second unbalanced filter provided between the other electric wire and ground for cutting a signal outside the predetermined band;
A power line communication apparatus comprising:   The power line communication apparatus according to claim 1, wherein the first and second unbalanced filters are bandpass filters having the predetermined band as a pass band.   2. The power line communication apparatus according to claim 1, wherein the first and second unbalanced filters are low-pass filters having a high band side outside the predetermined band as a stop band.

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