JP2010283737A - Power line communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power line communication system capable of maintaining a degree of balancing of communication wiring in a high state. <P>SOLUTION: Power lines 4A and 4B connect a battery 2 and an electric device 3. Furthermore, a branching part 5 branches from the plus-side power line 4A to communication combined power lines 7A, 7B. The communication combined power lines 7A, 7B are connected to a communication section 9 of a communication device 8 and connected to a plus-side power supply terminal 10A via a connection part 11. Thus, differential signals are superimposed on the communication combined power lines 7A, 7B and communication can be performed among a plurality of communication devices 8. Furthermore, power from the battery 2 can be supplied to the communication device 8 using the communication combined power lines 7A, 7B. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a power line communication system that performs communication by superimposing a differential signal on a power line connected to a DC power source such as a battery.

  Generally, as a power line communication system, for example, a power line communication system is known in which communication wirings connected to a pair of power lines connected to an in-vehicle battery are provided, and communication is performed by superimposing a high frequency signal of 1 MHz or more on the communication wiring. (For example, refer to Patent Document 1). Here, Patent Document 1 discloses a configuration in which a balanced filter having a balanced circuit configuration is provided between a communication wiring and a vehicle-mounted communication device. The balanced filter and each communication device are connected using a pair of balanced lines. Each communication device is configured to receive power from the in-vehicle battery using a balanced line and to transmit a differential signal for communication between the plurality of communication devices.

JP 2008-244701 A

  By the way, in the power line communication system according to Patent Document 1, when the ground terminal of the communication device is connected to the body ground of the vehicle body, only one balanced line is connected to the body ground. The degree will decrease. For this reason, there is a problem that the differential signal cannot be canceled by the balanced line, unnecessary radiation from the balanced line increases, and characteristic deterioration occurs.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a power line communication system capable of maintaining a high degree of balance of communication wiring.

  In order to solve the above-mentioned problem, the invention of claim 1 is connected to a positive terminal of a DC power source in a power line communication system in which a differential signal is superimposed on a power line connected to the DC power source. A branching portion for branching the positive power line into a pair of communication power lines, supplying power to the communication device using at least one of the pair of communication power lines, and connecting the pair of communication power lines. And performing communication using a differential signal between the communication devices.

  According to a second aspect of the present invention, the pair of power lines for communication is provided with a power supply side blocking unit that blocks the leakage power of the differential signal that is located on the branching unit side and that is directed to the positive power line.

  According to a third aspect of the present invention, the power supply side cutoff section is constituted by a coil having both ends connected to the pair of communication and power lines, and an intermediate tap connected to the positive power line.

  According to a fourth aspect of the present invention, the power-supply-side cutoff unit is connected at both ends to the pair of communication-use power lines, and the intermediate tap is connected to the positive-side power line, and the positive-side power line from the intermediate tap. A leakage power detector that detects the leakage power of the differential signal going to the control circuit, and a control unit that variably controls the coil so that the leakage power is reduced by using a detection signal from the leakage power detector. Yes.

  In the invention of claim 5, at least one of the pair of power lines for communication is provided with a connection portion connected to a power supply terminal on the positive side of the communication device, and the connection portion is provided with the positive side power supply terminal. A device-side blocking unit that blocks the leakage power of the differential signal directed to the power supply terminal is provided.

  According to a sixth aspect of the present invention, the connecting portion is configured such that one end side is connected to the power supply terminal on the positive side of the communication device and the other end side is connected to the pair of power lines for communication, respectively. Is constituted by a coil having both ends connected to the pair of communication power lines and an intermediate tap connected to the power supply terminal on the positive side of the communication device.

  According to the first aspect of the present invention, the positive power line connected to the positive terminal of the DC power source is branched to the pair of communication power lines using the branching unit. For this reason, since the positive voltage of the DC power source is supplied to both of the pair of communication power lines, power can be supplied to the communication device using at least one of the pair of communication power lines. . On the other hand, by superimposing a differential signal on a pair of communication / power lines, communication using a differential signal between a plurality of communication devices can be performed using the pair of communication / power lines.

  Further, since the pair of power lines for communication is connected to the positive terminal of the DC power source, it is not affected by the negative side. For this reason, even when the negative power supply terminal of the communication device is connected to the body ground, for example, the balance between the pair of communication power lines does not decrease, and the differential signal is canceled by the pair of communication power lines. be able to. Thereby, increase of the unnecessary radiation from the power line for communication can be suppressed.

  According to the second aspect of the present invention, since the pair of power lines for communication is provided with the power source side cut-off part, leakage of differential signals from the pair of power lines for communication to the positive power line is performed using the power source side cut off part. Power can be cut off. This prevents leakage power from being supplied to electrical devices connected to the power line, prevents communication performance between communication devices from being deteriorated, and prevents malfunctions and performance degradation of the electrical devices due to leakage power. be able to.

  According to the third aspect of the present invention, since the power supply side cutoff portion is constituted by the coils having both ends connected to the pair of power lines for communication and the intermediate tap connected to the power line on the positive side, the difference in transmitting each power line for communication is transmitted. The motion signal is combined at the intermediate tap and canceled. Thereby, the leakage power of the differential signal from the power line for communication to the positive power line can be cut off.

  In addition, since the power supply side cutoff unit can be configured using a single coil, the number of parts can be reduced compared to a case where a pair of communication power lines are provided with a coil that cuts off differential signals. Manufacturing cost can be reduced.

  According to the invention of claim 4, since the power supply side cutoff unit is constituted by the coil, the leakage power detector and the control unit, the control unit uses the detection signal from the leakage power detector so that the leakage power is reduced. The coil is variably controlled. Specifically, the difference between the differential signals in each communication / power line can be reduced by changing the inductor between the intermediate tap and each communication / power line by the control unit. Thereby, for example, even when the balance of the power line for communication decreases due to the influence of the communication device or the like, the leakage power can be reliably reduced.

  According to the invention of claim 5, since at least one of the pair of communication power lines is provided with the connection portion that connects to the power supply terminal on the positive side of the communication device, the communication power line is connected to the positive side of the communication device. Power can be supplied to the power supply terminal using the connection portion.

  In addition, since the device side blocking unit that blocks the leakage power of the differential signal directed to the positive power supply terminal is provided in the connection unit, the positive side of the communication device is connected from the pair of communication power lines using the device side blocking unit. The leakage power of the differential signal toward the power supply terminal can be cut off. Thereby, leakage power is not supplied to the communication device, communication performance between the communication devices can be prevented from being deteriorated, and malfunctions and performance deterioration of the communication device due to the leakage power can be prevented.

  According to the invention of claim 6, since the device-side blocking section is constituted by a coil having both ends connected to a pair of communication-use power lines and an intermediate tap connected to the power supply terminal on the positive side of the communication device, The differential signal transmitted through the power line is combined and canceled by the intermediate tap. In addition, since the device-side blocking unit can be configured using a single coil, the number of parts can be reduced compared to the case where a coil or the like for blocking a differential signal is provided for each pair of communication power lines. Manufacturing cost can be reduced.

1 is a perspective view showing an automobile equipped with a power line communication system according to a first embodiment of the present invention. It is a circuit diagram which shows the power line communication system in FIG. It is a circuit diagram which shows the power line communication system by 2nd Embodiment. It is a circuit diagram which shows the power line communication system by 3rd Embodiment.

  Hereinafter, a case where a power line communication system according to an embodiment of the present invention is mounted on an automobile will be described in detail with reference to the accompanying drawings.

  First, FIG. 1 and FIG. 2 show a power line communication system 1 according to the first embodiment. This power line communication system 1 is mounted on an automobile V, and a pair of power lines 4A and 4B for connecting a battery 2 and an electric device 3 and a pair of power lines 4A and 4B for communication (described later), plus a power line 4A on the plus side (positive side). It is set as the structure provided with the branch part 5 branched to 7A, 7B.

  The power line 4 </ b> A is connected to the plus terminal 2 </ b> A (positive side terminal) of the battery 2. On the other hand, the power line 4 </ b> B is connected to a negative terminal 2 </ b> B (negative terminal) of the battery 2 and is also connected to a body ground G formed of a chassis of the automobile V or the like. And power line 4A, 4B comprises the electric power supply path for supplying electric power, and supplies the electric power from the battery 2 toward the electric equipment 3 which consists of a motor etc., for example.

  The branching unit 5 branches the pair of power lines for communication 7A and 7B from the power line 4A on the plus side. Here, the branching unit 5 is configured by a T-shaped wiring in which both ends are connected to the communication / power lines 7A and 7B and the intermediate point 5A is connected to the power line 4A.

  The power supply side cut-off unit 6 is provided in the branch unit 5 and is configured by an impedance upper 6A (hereinafter referred to as a Z upper 6A) provided between the intermediate point 5A and each of the communication / power lines 7A and 7B. At this time, the Z upper 6A is constituted by a low-pass filter made of, for example, a coil or the like, has a high impedance in the frequency band of the differential signal, and has an impedance for a DC voltage or current that is supplied with power from the battery 2. It has a low configuration. As a result, the power supply side cutoff unit 6 separates the transmission region (signal transmission path) through which the differential signal is transmitted from the power line 4A, and leaks the differential signal from the communication power lines 7A and 7B toward the positive power line 4A. The power is cut off.

  The communication power lines 7A and 7B are composed of, for example, two balanced lines such as twisted pair wiring and shield wiring. In addition to constituting a power supply path for supplying power, a signal transmission path for transmitting a differential signal for communication Is configured. That is, the communication / power lines 7A and 7B constitute a signal transmission path / communication device power supply path. Here, one end side of the communication / power lines 7 </ b> A and 7 </ b> B is connected to the power line 4 </ b> A through the branching unit 5. For this reason, the plus side voltage of the battery 2 is applied to both the power lines for communication 7A and 7B. The communication power lines 7A and 7B are connected to a plurality of communication devices 8 such as various control circuits for controlling the engine and suspension, car navigation, car audio, and the like. Then, high-frequency signals with opposite phases from the communication device 8 are superimposed as differential signals on the communication power lines 7A and 7B, and these differential signals propagate through the communication power lines 7A and 7B.

  The communication device 8 includes a communication unit 9 that transmits or receives a differential signal composed of a high-frequency signal of 1 MHz to several GHz, for example. Further, the communication unit 9 of the communication device 8 is connected to the communication power lines 7A and 7B, respectively. The communication unit 9 transmits or receives a differential signal to the communication power lines 7A and 7B, and performs, for example, serial data communication with the other communication unit 9. Thus, each communication device 8 can communicate various data, control signals, and the like with the other communication device 8 using the communication unit 9.

  The communication device 8 includes positive and negative power supply terminals 10A and 10B. Here, the plus-side power supply terminal 10A of the communication device 8 is connected to both or one of the communication power lines 7A and 7B through the connection portion 11 described later. Further, the minus-side power supply terminal 10B of the communication device 8 is connected to the minus-side power line 4B and / or the body ground G of the automobile V. Thereby, the communication apparatus 8 can receive the power supply from the battery 2 through the communication combined power lines 7A and 7B.

  The connection unit 11 is provided in the communication device 8 and is configured by wiring in which one end side is connected to the plus-side power supply terminal 10A and the other end side is connected to both or one of the communication power lines 7A and 7B. ing. Thereby, the connection part 11 supplies the electric power from the battery 2 to the communication apparatus 8 through the communication combined power lines 7A and 7B.

  The device-side cutoff unit 12 is provided in the connection unit 11 and is configured by an impedance upper 12A (hereinafter referred to as Z-upper 12A) provided between the plus-side power supply terminal 10A and the communication power lines 7A and 7B. ing. At this time, the Z upper 12A is configured in substantially the same manner as the Z upper 6A. As a result, the device-side cutoff unit 12 separates the transmission region in which the differential signal is transmitted from the plus-side power supply terminal 10A, and the leakage power of the differential signal from the communication power lines 7A and 7B toward the power supply terminal 10A. Is shut off.

  The power line communication system 1 according to the present embodiment is configured as described above. Next, the operation of the power line communication system 1 will be described.

  First, the electric device 3 is connected to the power lines 4A and 4B. For this reason, when the electric device 3 is driven, power is supplied from the battery 2 through the power lines 4A and 4B.

  On the other hand, in the communication device 8, the plus-side power supply terminal 10A is connected to the communication power lines 7A and 7B, and the minus-side power supply terminal 10B is the minus-side power line 4B and / or the body ground G of the vehicle V. Connected to one side. Thereby, when the communication device 8 is driven, power is supplied from the battery 2 through the communication power lines 7A and 7B.

  Moreover, when communicating between the some communication apparatuses 8, the communication part 9 of each communication apparatus 8 transmits or receives a differential signal with respect to communication power line 7A, 7B. Thus, each communication device 8 can communicate various data, control signals, and the like with the other communication device 8 using the communication unit 9.

  Thus, in the present embodiment, the plus power line 4A connected to the plus terminal 2A of the battery 2 is branched to the pair of power / communication power lines 7A and 7B using the branching unit 5. For this reason, since the voltage on the plus side of the battery 2 is supplied to both of the pair of communication / power lines 7A and 7B, power is supplied to the communication device 8 using at least one of the pair of communication / power lines 7A and 7B. Supply can be made. On the other hand, by using a pair of communication power lines 7A and 7B to superimpose a differential signal on the pair of communication power lines 7A and 7B, communication using the differential signal between the plurality of communication devices 8 can be performed. .

  Further, since the pair of communication / power lines 7A and 7B are connected to the plus terminal 2A of the battery 2, they are not affected by the minus side. For this reason, for example, even when the negative power supply terminal 10B of the communication device 8 is connected to the body ground G, the balance between the pair of communication power lines 7A and 7B does not decrease, and the pair of communication power lines The differential signal can be canceled by 7A and 7B. Thereby, it is possible to suppress an increase in unnecessary radiation from the communication-use power lines 7A and 7B due to the negative side effect.

  Further, since the pair of power / communication power lines 7A and 7B are provided with the power supply-side cutoff unit 6, the differential signal from the pair of power / communication power lines 7A and 7B to the plus-side power line 4A is used. The leakage power can be cut off. As a result, leakage power is not supplied to the electrical equipment 3 connected to the power line 4A, the communication performance between the communication equipments 8 can be prevented from being deteriorated, and malfunction and performance of the electrical equipment 3 due to the leakage power can be prevented. Deterioration can be prevented.

  Further, since at least one of the pair of communication power lines 7A and 7B is provided with the connecting portion 11 connected to the power supply terminal 10A on the plus side of the communication apparatus 8, the communication power lines 7A and 7B to the communication apparatus 8 are provided. Power can be supplied to the plus-side power supply terminal 10 </ b> A using the connection portion 11.

  Here, in the power line communication system disclosed in Patent Document 1, since the communication balanced line is connected to a pair of power lines consisting of a plus side and a minus side, respectively, a communication line is connected to each of the power lines on both sides. A circuit for attenuating the differential signal is required. On the other hand, in the present embodiment, both of the communication power lines 7A and 7B are connected to the positive power line 4A, so that the communication power line 10A is connected to the positive power supply terminal 10A of the communication device 8. It is sufficient to connect one of 7A and 7B. In this case, since the apparatus side interruption | blocking part 12 is enough for the single Z upper 12A, manufacturing cost can be reduced.

  In addition, since the device-side blocking unit 12 that blocks the leakage power of the differential signal directed to the plus-side power supply terminal 10A is provided in the connecting unit 11, the pair of power / communication power lines 7A, The leakage power of the differential signal from 7B toward the power supply terminal 10A on the plus side of the communication device 8 can be cut off. As a result, leakage power is not supplied to the communication device 8, so that communication performance can be prevented from being deteriorated, and malfunction and performance deterioration of the communication device 8 due to leakage power can be prevented.

  In the first embodiment, the power supply side blocking section 6 including the Z upper 6A is provided in the branch section 5. However, the present invention is not limited to this, and the power supply-side blocking unit 6 may be provided in the middle of the communication power lines 7A and 7B separately from the branch unit 5.

  Next, FIG. 3 shows a second embodiment according to the present invention. The feature of the present embodiment is that a coil having both ends connected to a pair of communication / power lines and an intermediate tap connected to a plus-side power line. This is because the power supply side cutoff unit is configured. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The power line communication system 21 according to the second embodiment is configured by power lines 4A and 4B, communication-use power lines 7A and 7B, a branching unit 22 and the like, almost the same as the power line communication system 1 according to the first embodiment. .

  The branching unit 22 branches the pair of power / communication power lines 7A and 7B from the power line 4A on the plus side. Here, the branching unit 22 has one end connected to the communication / power lines 7A and 7B, the other end connected to the plus power line 4A, and a power source described later between the communication / power lines 7A and 7B and the power line 4A. A side blocking part 23 is provided.

  The power supply side cut-off part 23 is formed using a single coil 23 </ b> A provided in the branch part 22. Here, both ends of the coil 23A are connected to the communication / power lines 7A and 7B, respectively. On the other hand, the intermediate tap 23B of the coil 23A is connected to the power line 4A on the plus side. At this time, in the coil 23A, for example, the inductances at both ends with the intermediate tap 23B interposed therebetween are set to substantially the same value.

  The coil 23A constitutes a low-pass filter like the Z upper 6A according to the first embodiment, has a high impedance in the frequency band of the differential signal, and receives a DC voltage or current that is supplied with power from the battery 2. In contrast, the impedance is low. As a result, the power supply side cutoff unit 23 separates the transmission region (signal transmission path) through which the differential signal is transmitted from the power line 4A, and leaks the differential signal from the communication power lines 7A and 7B toward the positive power line 4A. The power is cut off.

  The connection unit 24 is provided in the communication device 8 and is configured by a T-shaped wiring in which one end side is connected to the plus-side power supply terminal 10A and the other end side is connected to both of the communication power lines 7A and 7B. ing. Thereby, the connection part 24 supplies the electric power from the battery 2 to the communication apparatus 8 through the communication combined power lines 7A and 7B.

  The device-side blocking unit 25 is formed using a single coil 25 </ b> A provided in the connection unit 24. Here, both ends of the coil 25 </ b> A are connected to communication / power lines 7 </ b> A and 7 </ b> B, respectively. On the other hand, the intermediate tap 25B of the coil 25A is connected to the plus-side power supply terminal 10A. At this time, the coil 25A is configured in substantially the same manner as the coil 23A. As a result, the device-side blocking unit 25 separates the transmission region in which the differential signal is transmitted from the plus-side power supply terminal 10A, and the leakage power of the differential signal from the communication power lines 7A and 7B toward the power supply terminal 10A. Is shut off.

  Thus, in the present embodiment configured as described above, it is possible to obtain substantially the same operational effects as those of the first embodiment. In particular, in the present embodiment, the power supply side cutoff unit 23 is configured by the coil 23A having both ends connected to the communication power lines 7A and 7B and the intermediate tap 23B connected to the plus power line 4A. And the intermediate tap 23B, the differential signals transmitted through the communication power lines 7A and 7B can be attenuated. As a result, the differential signals transmitted through the communication power lines 7A and 7B are combined and canceled by the intermediate tap 23B, so that the leakage power of the differential signal from the communication power lines 7A and 7B toward the positive power line 4A is cut off. can do.

  Moreover, since the power supply side cutoff part 23 can be comprised using the single coil 23A, compared with the case where the impedance upper etc. which interrupt | block a differential signal are each provided in a pair of communication power line 7A, 7B, The manufacturing cost can be reduced by reducing the number of parts.

  Similarly, since the device-side blocking unit 25 is configured by the coil 25A having both ends connected to the communication power lines 7A and 7B and the intermediate tap 25B connected to the plus-side power supply terminal 10A of the communication device 8, the manufacturing cost is reduced. A differential signal composed of a high-frequency signal can be blocked using the low single coil 25A.

  Further, the connection portion 24 is configured such that one end side is connected to the plus-side power supply terminal 10A of the communication device 8 and the other end side is connected to the communication / power lines 7A and 7B. For this reason, compared with the case where either one of the communication power lines 7A and 7B is connected to the power supply terminal 10A, the power from the battery 2 is supplied to the power supply terminal 10A using both the communication power lines 7A and 7B. Can be supplied. For this reason, since the electric current which flows into each communication power line 7A, 7B can be reduced, a thin line | wire can be used as each communication power line 7A, 7B, the reduction of the weight of communication power line 7A, 7B, The degree of design freedom can be improved and the manufacturing cost can be reduced.

  Next, FIG. 4 shows a third embodiment according to the present invention. The feature of the present embodiment is that a power supply side cutoff unit is constituted by a coil, a detection circuit and a control circuit. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The power line communication system 31 according to the third embodiment is configured by power lines 4A and 4B, communication-use power lines 7A and 7B, a branching unit 32, and the like in substantially the same manner as the power line communication system 1 according to the first embodiment. .

  The branching unit 32 branches the pair of power lines for communication 7A and 7B from the power line 4A on the plus side. Here, one end side of the branching unit 32 is connected to the communication / power lines 7A and 7B, the other end side is connected to the plus-side power line 4A, and a power source described later between the communication / power lines 7A and 7B and the power line 4A. A side blocking part 33 is provided.

  The power supply side cut-off unit 33 includes a coil 34 </ b> A, a detection circuit 35, and a control circuit 36. Here, both ends of the coil 34 </ b> A are connected to communication / power lines 7 </ b> A and 7 </ b> B, respectively. On the other hand, the intermediate tap 34B of the coil 34A is connected to the power line 4A on the plus side. At this time, in the coil 34A, for example, the position of the intermediate tap 34B can be changed. Thereby, the inductance of both ends of the coil 34A can be changed with the intermediate tap 34B interposed therebetween.

  The detection circuit 35 is provided between the intermediate tap 34B and the plus-side power line 4A, and detects current, voltage, and the like therebetween. The detection circuit 35 configures a leakage power detector that detects the leakage power of the differential signal from the intermediate tap 34B toward the power line 4A, and outputs a detection signal corresponding to the leakage power to the control circuit 36.

  The control circuit 36 constitutes a control unit that variably controls the coil 34A using the detection signal from the detection circuit 35 so that the leakage power is reduced. Specifically, when leakage power larger than a predetermined threshold is detected by the detection circuit 35, the position of the intermediate tap 34B is moved toward either one of both ends of the coil 34A. As a result, the inductance on both ends changes with the intermediate tap 34B interposed therebetween. For example, the inductance on one end side increases while the inductance on the other end side decreases. Therefore, by adjusting the inductances at both ends of the coil 34A, the attenuation amount of the differential signal for each of the communication power lines 7A and 7B is adjusted, and the difference between the differential signals in the communication power lines 7A and 7B is reduced. Can be made.

  Therefore, when the leakage power decreases, the control circuit 36 moves the intermediate tap 34B in the same direction until the leakage power decreases below the threshold value. On the other hand, when the leakage power increases, the control circuit 36 moves the intermediate tap 34B in the direction opposite to the direction moved so far. Thereby, the power supply side interruption | blocking part 33 feedback-controls the inductance of coil 34A based on leakage power, and reduces leakage power to a predetermined threshold value. As a result, the power supply side cutoff unit 33 can reliably cut off the leakage power of the differential signal from the communication power lines 7A and 7B toward the plus side power line 4A.

  In the present embodiment, the connection position of the intermediate tap 34B is moved as a method of controlling the inductance of the coil 34A. However, for example, by moving the core portion forward and backward in the coil 34A, the inductances at both ends of the coil 34A are reduced. It is good also as a structure to adjust.

  The connection unit 37 is configured in substantially the same manner as the connection unit 24 according to the second embodiment, and is provided in the communication device 8. One end side is connected to the plus-side power supply terminal 10 </ b> A and the other end side is a power line for communication. It is connected to both 7A and 7B. Further, the connection unit 37 is provided with a device-side blocking unit 38 that is substantially the same as the device-side blocking unit 25 according to the second embodiment. At this time, the device-side blocking unit 38 is formed by using coils 38A whose both ends are connected to the communication power lines 7A and 7B, respectively, and the intermediate tap 38B of the coil 38A is connected to the plus-side power supply terminal 10A. Yes.

  Thus, in the present embodiment configured as described above, it is possible to obtain substantially the same operational effects as those of the first embodiment. In particular, in the present embodiment, since the power supply side cutoff unit 33 is configured by the coil 34A, the detection circuit 35, and the control circuit 36, the control circuit 36 uses the detection signal from the detection circuit 35 to reduce the leakage power. The inductance of the coil 34A is variably controlled. Thereby, for example, even when the balance of the communication power lines 7A and 7B is reduced due to the influence of the communication device 8 or the like, the leakage power can be reliably reduced.

  In each of the above embodiments, the communication devices 8 are provided with the connecting portions 11, 24, 37 and the device-side blocking portions 12, 25, 38. However, the present invention is not limited to this, and connection units 11, 24, 37 and device side blocking units 12, 25, 38 are provided separately from the communication device 8, and these connection units 11, 24, 37, etc. are also used for communication. It is good also as a structure connected to power line 7A, 7B.

  In each of the above-described embodiments, the case where the power line communication systems 1, 21, 31 are mounted on the automobile V has been described as an example. However, the present invention can be widely applied to various devices driven by a DC voltage source. It is.

1,21,31 Power line communication system 2 Battery (DC voltage source)
4A, 4B Power line 5, 22, 32 Branching unit 6, 23, 33 Power supply side blocking unit 7A, 7B Power line for communication 8 Communication device 10A, 10B Power supply terminal 11, 24, 37 Connection unit 12, 25, 38 Device side blocking Part 23A, 25A, 34A, 38A Coil 23B, 25B, 34B, 38A Intermediate tap 35 Detection circuit (leakage power detector)
36 Control circuit (control unit)

Claims (6)

  In a power line communication system that communicates by superposing a differential signal on a power line connected to a DC power source, a branching unit that branches the positive power line connected to the positive terminal of the DC power source into a pair of communication power lines And supplying power to the communication device using at least one of the pair of communication power lines, and performing communication using the differential signal between the communication devices using the pair of communication power lines. A power line communication system.   2. The power line communication according to claim 1, wherein the pair of power lines for communication is provided with a power supply side cut-off unit that is located on the branching unit side and cuts off leakage power of a differential signal directed to the positive power line. system.   3. The power line communication system according to claim 2, wherein the power supply side cutoff unit is configured by a coil having both ends connected to the pair of communication power lines and an intermediate tap connected to the positive power line.   The power supply side cut-off unit is connected to the pair of communication power lines at both ends, a coil in which the intermediate tap is connected to the positive power line, and leakage of differential signals from the intermediate tap to the positive power line. The leakage power detector that detects electric power, and a control unit that variably controls the coil so that the leakage power is reduced by using a detection signal from the leakage power detector. Power line communication system. At least one of the pair of communication power lines is provided with a connection portion that is connected to a power supply terminal on the positive side of the communication device,
5. The power line communication system according to claim 1, 2, 3, or 4, wherein the connection unit is provided with a device-side blocking unit that blocks leakage power of a differential signal toward the positive power supply terminal. The connection part has a configuration in which one end side is connected to a power supply terminal on the positive side of the communication device and the other end side is connected to the pair of communication power lines,
6. The power line communication according to claim 5, wherein the device-side blocking unit is configured by a coil having both ends connected to the pair of communication power lines and an intermediate tap connected to a power supply terminal on the positive side of the communication device. system.

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