JP2017175530A - Power supply line communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To implement a satisfactory communication without providing an impedance increase part for each device connected to a power supply line in a power supply line communication system.SOLUTION: A power supply line communication system comprises: a power supply line (12) for supplying power from a DC power source (10) to multiple devices (2A, 2B, ...) including bypass capacitors (4A, 4B, ...); and communication parts (6A, 6B, ...) provided in the devices respectively. A communication frequency of the communication part is set in such a manner that a signal level of a communication signal is prevented from being reduced by impedance reduction of the bypass capacitor in that communication frequency. The DC power source includes impedance increase parts (20 and 22) for increasing impedance at a DC power source side in that communication frequency and suppressing level reduction of the communication signal.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a power line communication system that performs communication via a power line connected to a DC power source.

  The power line communication system includes a plurality of communication units (for example, modems) provided for a plurality of devices that operate by receiving power supply from the power line, and each device communicates with other devices via the communication unit. Send and receive communication signals between them.

  Moreover, in the power line communication system, the impedance of the device viewed from the power line is lowered by the noise reducing bypass capacitor provided in the connection part of the device to the power line, and the communication signal transmitted / received via the communication unit is reduced. The signal level may decrease.

  Therefore, in the power line communication system, as described in Patent Document 1, for example, an impedance increasing unit (impedance upper) for increasing the impedance of the power line is provided between the communication unit and the power line, so that the communication signal It has been proposed to suppress a decrease in signal level.

JP 2008-199094 A

  However, in the proposed power line communication system, although it is possible to suppress a decrease in the signal level of the communication signal, it is necessary to provide an impedance increasing unit for each device connected to the power line.

  For this reason, in a power line communication system in which a large number of devices are connected to the power line, there are problems that the number of impedance increasing portions increases, resulting in an increase in cost or an increase in the size of the entire system.

  An object of one aspect of the present disclosure is to enable good communication to be performed without providing an impedance increasing unit for each device connected to a power line in a power line communication system.

  A power line communication system according to one aspect of the present disclosure includes a power supply voltage from a DC power supply (10) with respect to a plurality of devices (2A, 2B,...) Provided with bypass capacitors (4A, 4B,...) For noise reduction. , And a plurality of communication units (6A, 6B,..., 8A, 8B,...) Respectively provided in the plurality of devices.

  The plurality of communication units are configured to transmit or receive a communication signal via a power line, and the communication frequency at the time of transmission / reception may cause a communication failure due to the impedance of the bypass capacitor at the communication frequency. There is no frequency range set.

  Accordingly, each communication unit performs communication using a communication signal having a frequency lower than that of the above-described conventional device, and power line communication can be performed without being affected by the bypass capacitor.

On the other hand, when the communication frequency in the communication unit is set in this way, the impedance of the DC power supply at the communication frequency is lowered, and the signal level of the communication signal may be lowered.
That is, the DC power supply is usually constituted by a battery or a power supply circuit provided with a capacitor for stabilizing the output voltage. The capacity of the DC power supply (that is, the capacity of the battery or the capacity of the output voltage stabilizing capacitor) is larger than the capacity of the bypass capacitor. For this reason, when the communication frequency in the communication unit is set to a low frequency as described above, good communication may not be performed due to the impedance of the power supply circuit.

  Therefore, in the power line communication system according to the present disclosure, an impedance increasing unit that increases the impedance of the DC power supply side at the communication frequency with respect to the DC power supply and suppresses the reduction in the level of the communication signal due to the impedance reduction of the DC power supply ( 20 and 22).

As a result, according to the power line communication system of the present disclosure, power communication by the communication unit can be satisfactorily performed only by providing the DC power source with the impedance increasing unit.
Therefore, according to the present disclosure, it is possible to reduce the number of impedance increasing portions as compared with the conventional device, and it is possible to implement good communication at low cost and without causing an increase in the size of the system. Can be realized.

  In addition, the code | symbol in the parenthesis described in this column and a claim shows the correspondence with the specific means as described in embodiment mentioned later as one aspect, Comprising: The technical scope of this invention is shown. It is not limited.

It is a block diagram showing the whole structure of the power line communication system of 1st Embodiment. FIG. 3 is a circuit diagram illustrating a configuration of an impedance increasing unit in FIG. 2. It is explanatory drawing showing the change of the impedance which arises by inserting the impedance increase part of FIG. It is a block diagram showing the structure of the whole power line communication system of 2nd Embodiment. FIG. 5 is a circuit diagram illustrating a configuration of an impedance increasing unit in FIG. 4 and its peripheral circuits. It is explanatory drawing showing the change of the impedance which arises by inserting the impedance increase part of FIG. It is a flowchart showing operation | movement of the communication signal detection part of FIG. It is a block diagram showing the structure of the whole power line communication system of 3rd Embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
As shown in FIG. 1, the power line communication system of the present embodiment is provided in each of a plurality of electronic control devices (hereinafter referred to as ECUs) 2A, 2B, 2C,... That control various in-vehicle devices mounted on the vehicle. A plurality of communication units 6A, 6B, 6C,.

  The communication units 6A, 6B, 6C,... Are for performing communication via the power line 12 that supplies power from the battery 10 to the ECUs 2A, 2B, 2C,. In the present embodiment, for example, when one of the ECUs 2A, 2B, 2C,... Is activated by a driver's operation or the like, the other ECUs 2A, 2B, 2C,.

  That is, when the communication units 6A, 6B, 6C,... Receive transmission commands from the corresponding ECUs 2A, 2B, 2C,. When received, the corresponding ECUs 2A, 2B, 2C,.

  Further, each of the ECUs 2A, 2B, 2C,... Reduces noise input from the power line 12 to the ECUs 2A, 2B, 2C,... And noise output from the ECUs 2A, 2B, 2C,. For this purpose, bypass capacitors 4A, 4B, 4C,... Are provided.

The capacities of the bypass capacitors 4A, 4B, 4C,... Are set corresponding to the frequency of noise to be removed.
And the communication units 6A, 6B, 6C,... Do not cause a communication failure due to a decrease in signal level of the communication signal due to the impedance of the bypass capacitors 4A, 4B, 4C,. The communication frequency is set.

  Specifically, the communication frequency of the communication units 6A, 6B, 6C,... Is several kHz or less (this is sufficiently lower than the noise frequency so that the impedance of the bypass capacitors 4A, 4B, 4C,. In the embodiment, it is set to 100 Hz band).

  Therefore, the communication speed of the communication units 6A, 6B, 6C,... Is several kbps or less. This communication speed is lower than the communication speed (several tens of kbps) in a general in-vehicle LAN constructed using a dedicated communication line, and the communication amount per unit time is reduced, but the wake-up signal It is enough for transmission and reception.

  Further, if the communication frequencies of the communication units 6A, 6B, 6C,... Are set in this way, it is possible to prevent communication failure due to the impedance of the bypass capacitors 4A, 4B, 4C,. May drop to several ohms.

  That is, as shown in FIG. 2, the equivalent circuit of the battery 10 can be represented as a series circuit of a capacitor C0, a coil L0, and a resistor R0, and since the capacity thereof is large, the battery 10 can be used even in a frequency region of several kHz or less. Impedance decreases.

And if the impedance of the battery 10 falls in this way, the signal level of the communication signal transmitted / received in communication part 6A, 6B, 6C, ... will fall, and communication failure will generate | occur | produce.
Therefore, in the present embodiment, an impedance increasing unit 20 that increases the impedance on the battery 10 side is provided between the battery 10 and the power supply line 12 so that communication can be normally performed without being affected by the battery 10. ing.

  Since the impedance increasing unit 20 is provided between the power supply line 12 and the battery 10, the impedance increasing unit 20 is configured by an LC parallel resonance circuit in which a capacitor C1 and a coil L1 are connected in parallel. The resonance frequency is a communication frequency (this embodiment). Is set to 100 Hz).

  Therefore, as shown in FIG. 3, the impedance on the battery 10 side viewed from the power supply line 12 becomes maximum (about 1 kΩ in the figure) at the communication frequency of the communication units 6A, 6B, 6C,. It can suppress that a signal level falls.

Therefore, according to the power line communication system of the present embodiment, it is only necessary to provide the battery 10 with the impedance increasing unit 20. Therefore, according to the present embodiment, a power line communication system capable of performing good communication can be realized at a low cost without increasing the size of the system.
[Second Embodiment]
As shown in FIG. 4, the power line communication system of the present embodiment has the same configuration on the ECU 2A, 2B, 2C,..., Which is an in-vehicle device as the first embodiment, and the configuration on the battery 10 side is the first implementation. Different from form.

Therefore, in the following description, the description of the configuration of the ECUs 2A, 2B, 2C,... Will be omitted, and the configuration of the battery 10 side that is different from the first embodiment will be described.
In the present embodiment, the impedance increasing unit 22 is arranged in parallel with the battery 10 when viewed from the power supply line 12. Further, a communication signal detection unit 24 and a control unit 26 are connected to a connection portion between the battery 10 and the power supply line 12, and the impedance increase unit 22 is connected in parallel to the battery 10 via the control unit 26. .

  The communication signal detection unit 24 is for detecting a wake-up signal transmitted from any of the communication units 6A, 6B, 6C,..., And includes a coil L3 and a capacitor C3 as shown in FIG. A series resonant circuit.

  One end of this series resonant circuit is connected to the power supply line 12, and the other end is grounded to the ground which is a negative power supply line via a resistor R3. Further, the resonance frequency of the series resonance circuit is set to the communication frequency of the communication units 6A, 6B, 6C,... (In other words, the communication speed of the wake-up signal). Therefore, in the communication signal detection unit 24, when a wake-up signal is transmitted from any of the communication units 6A, 6B, 6C,..., A current flows through the resistor R3, and a voltage is generated across the resistor R3.

  The control unit 26 is for connecting the impedance increasing unit 22 to the power supply line 12 when the communication signal detecting unit 24 detects the wake-up signal. As shown in FIG. A switching element Q1 made of a channel MOSFET is provided.

  The switching element Q1 has a gate connected to a connection portion between the series resonance circuit of the communication signal detection unit 24 and the resistor R3, a drain connected to the power supply line 12, and a source connected to the impedance increasing unit 22. Yes.

  Therefore, in the control unit 26, the switching element Q1 is turned on by the voltage generated in the resistor R3 when the communication signal detection unit 24 detects the wake-up signal, and the impedance increasing unit 22 with respect to the battery 10 is turned on. Will be connected in parallel.

  The impedance increasing unit 22 is configured by a series circuit of a capacitor C2 and a coil L2. One end of the series circuit on the capacitor C2 side is connected to the source of the switching element Q1, and one end on the coil L2 side is grounded. Has been.

  The capacitance of the capacitor C2 and the inductance of the coil L2 are set so as to resonate in parallel with the battery 10 at the frequency of the wake-up signal (that is, the communication frequency) when these series circuits are connected in parallel to the battery 10. Has been.

  Therefore, according to the power line communication system of the present embodiment, as shown in FIG. 6, when the wake-up signal is transmitted to the power line 12, the impedance increasing unit 22 resonates in parallel with the battery 10, The impedance on the battery 10 side is increased.

  Therefore, also in the power line communication system of the present embodiment, each communication unit 6A, 6B, 6C,... Can transmit and receive a communication signal (wake-up signal) satisfactorily without being affected by the impedance of the battery 10. It becomes possible.

  Moreover, in this embodiment, since the impedance increase part 22 is connected to the battery 10 using the communication signal detection part 24 and the control part 26, a structure becomes complicated rather than the power line communication system of 1st Embodiment.

  However, the power line communication system according to the present embodiment does not need to provide the impedance increasing unit 20 between the battery 10 and the power line 12 (in other words, in series with the battery 10) as in the first embodiment.

  For this reason, the power line communication system of the present embodiment can be realized by retrofitting the existing power line 12 with the impedance increasing unit 22, the communication signal detecting unit 24, and the control unit 26, and the impedance increasing unit 20 is provided. Therefore, it is not necessary to change the specification of the battery 10.

  In the first embodiment, since the impedance increasing unit 20 is always connected between the power supply line 12 and the battery 10, the impedance may be increased with respect to low frequency noise.

  However, in this embodiment, since the impedance is increased only in the frequency region of the wakeup signal only when the wakeup signal is flowing through the power supply line 12, it is possible to suppress the impedance from being increased with respect to the low frequency noise. The power line communication can be carried out satisfactorily.

  In the present embodiment, the communication signal detection unit 24 is described as being configured by an analog circuit including the coil L3, the capacitor C3, and the resistor R3. For example, the communication signal detection unit 24 captures a wakeup signal via a filter. A signal processing circuit that turns on the control unit 26 may be used.

In this case, the communication signal detection unit 24 may be configured to turn the control unit 26 on and off according to the control procedure shown in the flowchart of FIG.
That is, the communication signal detection unit 24 first receives a wake-up signal by determining whether or not a wake-up signal (WU signal) is received through a filter in S110 (S represents a step). Wait to be done.

  When it is determined in S110 that the wake-up signal has been received, in S120, the control unit 26 is turned on, and the impedance increasing unit 22 is connected in parallel to the battery 10.

Thereafter, in S130, it is determined whether or not a wake-up signal is being received. If the wake-up signal is being received, the process proceeds to S120. If not, the process proceeds to S140. Then, the control unit 26 is turned off, and the control process is ended once. Note that after the completion of the control process, the process returns to S110 again, and the control process is repeatedly executed.
[Third Embodiment]
Since the basic configuration of the power line communication system according to the present embodiment is the same as that of the power line communication system according to the second embodiment shown in FIG. 4, this embodiment will explain differences from the second embodiment. The description of the same configuration as that of the second embodiment is omitted.

  As shown in FIG. 8, in the power line communication system of the present embodiment, a transmission unit 30 that transmits a wake-up signal is provided on the battery 10 side instead of the communication signal detection unit 24 of the second embodiment. Yes. The transmission unit 30 sends a wake-up signal to the power supply line 12 in accordance with a command from a user or a command transmitted from another ECU using a communication line.

  In addition, the ECUs 2A, 2B, 2C,..., Which are in-vehicle devices, receive a wakeup signal transmitted from the transmission unit 30 instead of the communication units 6A, 6B, 6C,. Portions 8A, 8B, 8C,... Are provided. And each receiving part 8A, 8B, 8C, ... will start corresponding ECU2A, 2B, 2C, ..., if a wakeup signal is received.

  Also, the transmission unit 30 turns on the control unit 26 simultaneously with the start of transmission of the wakeup signal, connects the impedance increasing unit 22 to the battery 10 in parallel, and stops transmission of the wakeup signal. Turn off.

  Therefore, according to the power line communication system of the present embodiment, transmission of the wake-up signal from the transmission unit 30 to each of the reception units 8A, 8B, 8C,... Is favorably performed without being affected by the impedance of the battery 10. Can be implemented.

  Further, in this embodiment, unlike the power line communication system of the second embodiment, it is not necessary to detect a communication signal (wake-up signal) using the communication signal detector 24. It is possible to prevent the increase unit 22 from being connected to the battery 10.

Although the three embodiments have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present disclosure.
For example, in the above-described embodiment, the power line 12 has been described as being used for transmitting and receiving a wake-up signal for activating a device (that is, an ECU) that is a communication terminal. However, if the communication signal is a communication frequency (low frequency) that does not cause communication failure due to the impedance of the bypass capacitors 4A, 4B, 4C,. Various information may be transmitted and received.

  Further, in the above-described embodiment, a description has been given of performing communication via the power line 12 that receives power from the battery 10. However, even if the power supply circuit is provided with a power supply circuit that converts an AC voltage such as a commercial power supply into a DC voltage and outputs it as a DC power supply, and communicates via a power supply line that receives power supply from the power supply circuit, the above implementation It can be applied in the same way as the form.

  In the above embodiment, the power line communication system is described as being mounted on a vehicle. However, the power line communication system is not limited to a vehicle, and various devices are connected from a DC power source via the power line 12. Any system that supplies power can be applied in the same manner as described above.

  In addition, a plurality of functions of one constituent element in the above embodiment may be realized by a plurality of constituent elements, or a single function of one constituent element may be realized by a plurality of constituent elements. Further, a plurality of functions possessed by a plurality of constituent elements may be realized by one constituent element, or one function realized by a plurality of constituent elements may be realized by one constituent element. Moreover, you may abbreviate | omit a part of structure of the said embodiment. In addition, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment. In addition, all the aspects included in the technical idea specified only by the wording described in the claim are embodiment of this invention.

  2A, 2B, 2C ... ECU, 4A, 4B, 4C ... bypass capacitor, 6A, 6B, 6C ... communication unit, 8A, 8B, 8C ... receiving unit, 10 ... battery, 12 ... power line, 20, 22 ... impedance increase Part, C1, C2 ... capacitor, L1, L2 ... coil, 24 ... communication signal detection part, L3 ... coil, C3 ... capacitor, R3 ... resistance. 26: control unit, Q1: switching element, 30: transmission unit.

Claims (4)

A power supply line (12) for supplying a power supply voltage from a DC power supply (10) to a plurality of devices (2A, 2B,...) Provided with bypass capacitors (4A, 4B,...) For noise reduction;
Each of the plurality of devices is configured to transmit or receive a communication signal via the power line, and a communication frequency at the time of transmission or reception is communicated by an impedance of the bypass capacitor at the communication frequency. A plurality of communication units (6A, 6B,..., 8A, 8B,...) Set in a frequency region where no defect occurs,
An impedance increasing section (20, 22) provided in the DC power supply, for increasing the impedance of the DC power supply side at the communication frequency and suppressing a decrease in the level of the communication signal due to a decrease in impedance of the DC power supply;
A power line communication system.   2. The power line communication system according to claim 1, wherein the impedance increasing unit is provided between the DC power supply and the power supply line and configured to increase the impedance by parallel resonance at the communication frequency. . The impedance increasing unit is configured to increase impedance on the DC power supply side by being connected in parallel to the DC power supply,
The DC power supply further includes
A communication signal detector (24) for detecting the communication signal transmitted from at least one of the plurality of communication units via the power line;
A control unit (26) for increasing the impedance by connecting the impedance increasing unit in parallel to the DC power source when the communication signal is detected by the communication signal detecting unit;
The power line communication system according to claim 1, comprising: The communication unit provided in each of the plurality of devices includes a receiving unit (8A, 8B,...) That receives the communication signal.
The impedance increasing unit is configured to increase impedance on the DC power supply side by being connected in parallel to the DC power supply,
The DC power supply further includes
A transmission unit (30) for transmitting the communication signal to each of the reception units via the power line;
A control unit (26) for increasing the impedance by connecting the impedance increasing unit in parallel to the DC power source when the transmitting unit is transmitting the communication signal;
The power line communication system according to claim 1, comprising:

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