Power line communication system

Abstract

To suppress deterioration in communication quality.SOLUTION: A power line communication system 100 includes a master terminal 1 and a plurality of slave terminals, and has a communication mode for performing power line communication between the master terminal 1 and each of the plurality of slave terminals and between the plurality of slave terminals. In the power line communication system 100, the first timing at which the first communication signal is transmitted to the first wireless terminal, the second timing at which the second communication signal is transmitted to the second wireless terminal, and the third timing at which the third communication signal is transmitted to the third wireless terminal are different from one another.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a power line communication system, and more particularly to a power line communication system that performs power line communication between a master terminal and each of a plurality of slave terminals, and between the plurality of slave terminals. [Background technology]

[0002] Patent Document 1 describes a control system including a plurality of power line communication devices. The plurality of power line communication devices include a power line communication device (hereinafter referred to as a "first power line communication device") connected to a three-phase 200V power wiring, and a power line communication device (hereinafter referred to as a "second power line communication device") connected to a single-phase power wiring via a distribution board. In the control system described in Patent Document 1, power line communication can be performed between the first power line communication device (parent terminal) and the second power line communication device (child terminal) via a capacitor connected between the three-phase power wiring and the single-phase power wiring. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-20197 Summary of the Invention [Problem to be solved by the invention]

[0004] In a control system (power line communication system) such as that described in Patent Document 1, communication quality may be degraded by leakage signals due to stray capacitance occurring between phases.

[0005] An object of the present disclosure is to provide a power line communication system capable of suppressing degradation in communication quality. [Means for solving the problem]

[0006] A power line communication system according to one embodiment of the present disclosure includes a master terminal and a plurality of slave terminals and has a communication mode. The master terminal is connected to three phases of a three-phase power supply. Each of the slave terminals is connected to any two of the three phases of the three-phase power supply. In the communication mode, power line communication is performed between the master terminal and each of the slave terminals, and among the slave terminals. The slave terminals include a first slave terminal whose two phases are the R phase and the S phase, a second slave terminal whose two phases are the S phase and the T phase, and a third slave terminal whose two phases are the T phase and the R phase. The master terminal transmits a communication signal to each of the slave terminals, the communication signal including identification information for identifying the two phases. In the power line communication system, a first timing, a second timing, and a third timing are different from one another. The first timing is a timing for transmitting a first communication signal, which is the communication signal for the first handset terminal, to the first handset terminal. The second timing is a timing for transmitting a second communication signal, which is the communication signal for the second handset terminal, to the second handset terminal. The third timing is a timing for transmitting a third communication signal, which is the communication signal for the third handset terminal, to the third handset terminal. [Effects of the Invention]

[0007] According to a power line communication system according to an aspect of the present disclosure, it is possible to suppress a decrease in communication quality. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram of a master terminal in a power line communication system according to an embodiment. [Figure 2] FIG. 2 is a block diagram of a slave terminal in the power line communication system. [Figure 3] FIG. 3 is a timing chart of a communication signal transmitted from a master terminal to each slave terminal in the power line communication system. [Figure 4]FIG. 4 is a block diagram of a slave terminal in a power line communication system according to the first modification of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Embodiment) Hereinafter, a power line communication system according to an embodiment will be described with reference to the drawings. The drawings referred to in the following embodiments are schematic diagrams, and the sizes and thicknesses of the components in the drawings do not necessarily reflect the actual dimensions, and the ratios of the sizes and thicknesses between the components do not necessarily reflect the actual dimensional ratios.

[0010] (1) Overview First, an overview of a power line communication system 100 according to an embodiment will be described with reference to FIGS.

[0011] As shown in FIGS. 1 and 2 , a power line communication system 100 according to the embodiment includes a master terminal 1 and a plurality of slave terminals 2. In the power line communication system 100, the master terminal 1 and each of the plurality of slave terminals 2 are electrically connected via a multi-core cable CA1. In the example of FIGS. 1 and 2 , the multi-core cable CA1 includes three electric wires L1, L2, and L3. The power line communication system 100 has a communication mode and a sensitivity test mode. In the communication mode, the power line communication system 100 performs power line communication between the master terminal 1 and each of the plurality of slave terminals 2, and between the plurality of slave terminals 2. In addition, in the sensitivity test mode, the power line communication system 100 tests the receiving sensitivity of a communication signal in each of the plurality of slave terminals 2.

[0012] As shown in FIG. 1, the master terminal 1 is connected to three phases (R phase, S phase, and T phase) of a three-phase power source PS1. As shown in FIG. 2, each of the multiple slave terminals 2 is connected to any two of the three phases of the three-phase power source PS1. In the example of FIG. 2, a first slave terminal 2A is connected to the R phase and the S phase. A second slave terminal 2B is connected to the S phase and the T phase. A third slave terminal 2C is connected to the T phase and the R phase. That is, the multiple slave terminals 2 include a first slave terminal 2A whose two phases are the R phase and the S phase, a second slave terminal 2B whose two phases are the S phase and the T phase, and a third slave terminal 2C whose two phases are the T phase and the R phase. Here, the R phase, the S phase, and the T phase refer to phases that are shifted from each other by 120 degrees. More specifically, the S phase is delayed by 120 degrees from the R phase, the T phase is delayed by 120 degrees from the S phase, and the R phase is delayed by 120 degrees from the T phase.

[0013] The master terminal 1 transmits to each of the slave terminals 2 a communication signal including identification information for identifying the two phases.

[0014] In the power line communication system 100 according to the embodiment, the first timing, the second timing, and the third timing are different from one another. The first timing is the timing at which a first communication signal, which is a communication signal for the first child terminal 2A, is transmitted from the master terminal 1 to the first child terminal 2A. The second timing is the timing at which a second communication signal, which is a communication signal for the second child terminal 2B, is transmitted from the master terminal 1 to the second child terminal 2B. The third timing is the timing at which a third communication signal, which is a communication signal for the third child terminal 2C, is transmitted from the master terminal 1 to the third child terminal 2C.

[0015] In the power line communication system 100 according to the embodiment, as described above, the first timing, the second timing, and the third timing are different from one another, which makes it possible to prevent a deterioration in communication quality due to a leakage signal caused by stray capacitance occurring between phases.

[0016] (2)Details Next, each component of the power line communication system 100 according to the embodiment will be described with reference to FIGS.

[0017] 1 and 2, a power line communication system 100 according to the embodiment includes a master terminal 1 and a plurality of slave terminals 2. The power line communication system 100 has a communication mode. In the communication mode, the power line communication system 100 performs power line communication between the master terminal 1 and each of the plurality of slave terminals 2, and between the plurality of slave terminals 2.

[0018] In a three-phase, three-wire power supply, if the power consumed between each phase is equal, the current flowing through the wires of each phase will cancel each other out, and ideally, no current will flow through the wires at all. As a result, loss in the wires will decrease, and the voltage drop due to wire impedance will also decrease. For this reason, it is common to perform wiring work for the handset terminals 2 so that the number of handset terminals 2 connected between each phase is balanced evenly.

[0019] As described above, the power line communication system 100 according to the embodiment has a communication mode and a sensitivity test mode. As an example, in the present embodiment, during a test period, the operation mode of the power line communication system 100 is automatically switched from the communication mode to the sensitivity test mode. The test period is preferably, for example, during the night when dimming control based on brightness information from the external device 3 described below is not required. The sensitivity test mode will be described in the section "(3) Sensitivity Test Mode."

[0020] (2.1) Parent terminal As shown in Fig. 1, the parent terminal 1 is connected to three phases of a three-phase power source PS1. More specifically, the parent terminal 1 is connected to the R phase, S phase, and T phase of the three-phase power source PS1. In this embodiment, as an example, the three-phase power source PS1 is a three-phase, three-wire power distribution system. In this embodiment, the three-phase power source PS1 is delta-connected. In the three-phase power source PS1 shown in Fig. 1, the S phase of the R phase, S phase, and T phase is grounded.

[0021] The base terminal 1 can be realized, for example, by a computer system having one or more processors and one or more memories. That is, the base terminal 1 functions as a computer system by having one or more processors execute a program recorded in one or more memories of the computer system. Here, the program is pre-recorded in the memory of the computer system, but it may also be provided via a telecommunications line such as the Internet, or may be provided by recording it on a non-transitory recording medium such as a memory card.

[0022] As shown in FIG. 1, the base terminal 1 includes a control unit 11, a power supply unit 12, a communication unit 13, and a display unit .

[0023] (2.1.1) Control Unit The control unit 11 controls each unit of the parent terminal 1. The control unit 11 is electrically connected to each of the power supply unit 12, the communication unit 13, and the display unit 14. The control unit 11 receives operating power from the power supply unit 12. The control unit 11 outputs a control signal to the communication unit 13 and controls the communication unit 13 to perform power line communication with each of the multiple child terminals 2. The control unit 11 also outputs a control signal to the display unit 14 and controls the display unit 14 to display the display content included in the control signal.

[0024] Here, it is assumed that the master terminal 1 transmits a communication signal to each slave terminal 2 at the same timing. In this case, the master terminal 1 superimposes a communication signal (hereinafter also referred to as a "first communication signal") on the AC power supplied via the R phase and S phase for the first slave terminal 2A. The master terminal 1 also superimposes a communication signal (hereinafter also referred to as a "second communication signal") on the AC power supplied via the S phase and T phase for the second slave terminal 2B. The master terminal 1 also superimposes a communication signal (hereinafter also referred to as a "third communication signal") on the AC power supplied via the T phase and R phase for the third slave terminal 2C.

[0025] The electric wire L1 corresponding to the R phase, the electric wire L2 corresponding to the S phase, and the electric wire L3 corresponding to the T phase are housed in a single sheath and form a multi-core cable CA1. In this multi-core cable CA1, the distance between the electric wires L1, L2, and L3 is short. Therefore, as the cable length of the multi-core cable CA1 increases, stray capacitance SC1 occurs between the electric wires L1, L2, and L3 (see FIG. 1). For example, when the first handset terminal 2A receives a first communication signal, the second communication signal may leak to the electric wire L2 via the stray capacitance SC1 generated between the electric wires L2 and L3, or the third communication signal may leak to the electric wire L1 via the stray capacitance SC1 generated between the electric wires L1 and L3. This causes fluctuations in the signal waveform of the first communication signal, resulting in a degradation in communication quality.

[0026] Therefore, in the power line communication system 100 according to the embodiment, the control unit 11 of the master terminal 1 differentiates the first timing for transmitting the first communication signal to the first slave terminal 2A, the second timing for transmitting the second communication signal to the second slave terminal 2B, and the third timing for transmitting the third communication signal to the third slave terminal 2C. This prevents leakage signals from being transmitted via the other two phases, thereby preventing degradation of communication quality. Details will be described in the section "(4) Operation."

[0027] Furthermore, in the power line communication system 100 according to the embodiment, the control unit 11 of the master terminal 1 makes the first transmission frequency, which is the transmission frequency of the first communication signal, the second transmission frequency, which is the transmission frequency of the second communication signal, and the third transmission frequency, which is the transmission frequency of the third communication signal, different from one another. More specifically, the control unit 11 sets the transmission frequency of the first communication signal to 25 MHz to 30 MHz, the transmission frequency of the second communication signal to 15 MHz to 20 MHz, and the transmission frequency of the third communication signal to 5 MHz to 10 MHz, for example. In this way, by using different transmission frequencies for each communication signal, it is possible to further suppress degradation of communication quality.

[0028] (2.1.2) Power supply section The power supply unit 12 generates operating power from AC power supplied from the three-phase power supply PS1 to be supplied to each of the control unit 11, the communication unit 13, and the display unit 14. The power supply unit 12 includes, for example, an AC / DC converter. The power supply unit 12 generates DC power from the AC power as operating power for each of the control unit 11, the communication unit 13, and the display unit 14. The power supply unit 12 supplies the generated operating power (DC power) to each of the control unit 11, the communication unit 13, and the display unit 14.

[0029] (2.1.3) Communications Department The communication unit 13 includes a communication interface for communicating with each slave terminal 2. More specifically, the communication unit 13 performs power line communication with each slave terminal 2. Specifically, the communication unit 13 superimposes a communication signal on the AC power supplied via the two phases to which each slave terminal 2 is connected. The communication signal includes address information and identification information. The address information is information individually assigned to each slave terminal 2 and includes a different value. The identification information is information for identifying the two phases to which each slave terminal 2 is connected and includes a different value. In other words, the master terminal 1 transmits, to each of the multiple slave terminals 2, a communication signal including identification information for identifying the two phases to which each slave terminal 2 is connected, out of the three phases of the three-phase power supply PS1. The communication signal also includes a control command. The control command includes a dimming level of a light source 25 of the slave terminal 2, which will be described later.

[0030] (2.1.4) Display section The display unit 14 is, for example, a liquid crystal display. The display unit 14 displays, for example, the display content included in the control signal transmitted from the control unit 11. Note that the display unit 14 may be omitted.

[0031] (2.2) Child terminal Each of the multiple slave terminals 2 is connected to any two of the three phases of the three-phase power supply PS1. In this embodiment, the multiple slave terminals 2 include a first slave terminal 2A, a second slave terminal 2B, and a third slave terminal 2C, as shown in FIG. 2 . The first slave terminal 2A is connected to the R phase and the S phase as the two phases. The second slave terminal 2B is connected to the S phase and the T phase as the two phases. The third slave terminal 2C is connected to the T phase and the R phase as the two phases. That is, the multiple slave terminals 2 include the first slave terminal 2A whose two phases are the R phase and the S phase, the second slave terminal 2B whose two phases are the S phase and the T phase, and the third slave terminal 2C whose two phases are the T phase and the R phase. In this embodiment, there is one each of the first child terminal 2A, the second child terminal 2B, and the third child terminal 2C, but there may be two or more each of the first child terminal 2A, the second child terminal 2B, and the third child terminal 2C.

[0032] Each slave terminal 2 can be realized, for example, by a computer system having one or more processors and one or more memories. That is, each slave terminal 2 functions as a computer system by one or more processors executing a program recorded in one or more memories of the computer system. Here, the program is pre-recorded in the memory of the computer system, but it may also be provided via a telecommunications line such as the Internet, or may be provided by recording it on a non-transitory recording medium such as a memory card.

[0033] As shown in Fig. 2, each slave terminal 2 includes a control unit 21, a power supply unit 22, a communication unit 23, a lighting circuit unit 24, and a light source 25. That is, in this embodiment, each slave terminal 2 is a lighting fixture 20 that illuminates a target space. The target space is, for example, a highway, and the lighting fixture 20 is, for example, a road light or a tunnel light. Note that, in the example of Fig. 2, the components of the second slave terminal 2B and the third slave terminal 2C are not shown, but they include the same components as the first slave terminal 2A.

[0034] (2.2.1) Control Unit The control unit 21 controls each unit of the slave terminal 2. The control unit 21 is electrically connected to each of the power supply unit 22, the communication unit 23, and the lighting circuit unit 24. The control unit 21 receives operating power from the power supply unit 22. The control unit 21 outputs a control signal to the communication unit 23 and controls the communication unit 23 to perform power line communication with the master terminal 1. The control unit 21 also outputs a control signal to the lighting circuit unit 24 and controls the lighting circuit unit 24 to light the light source 25 at the dimming level included in the control signal.

[0035] Here, it is preferable that the control unit 21 change the bandwidth of the transmission frequency of the specific communication signal, which is a communication signal to the base terminal 1, depending on the communication volume of the specific communication signal. For example, assume that the slave terminal 2 is equipped with a camera and transmits an image captured by the camera to the base terminal 1. In this case, the amount of information of the image transmitted from the slave terminal 2 to the base terminal 1 is large, and the time required for transmission is long. Therefore, when transmitting a communication signal including the image, the control unit 21 widens the bandwidth of the transmission frequency of this communication signal. This makes it possible to transmit the communication signal to the base terminal 1 even if the amount of information of the communication signal transmitted from the slave terminal 2 to the base terminal 1 is large.

[0036] (2.2.2) Power supply section The power supply unit 22 generates operating power from AC power supplied from the three-phase power supply PS1 to be supplied to each of the control unit 21, the communication unit 23, and the lighting circuit unit 24. The power supply unit 22 includes, for example, an AC / DC converter. The power supply unit 22 generates DC power from the AC power as operating power for each of the control unit 21, the communication unit 23, and the lighting circuit unit 24. The power supply unit 22 supplies the generated operating power (DC power) to each of the control unit 21, the communication unit 23, and the lighting circuit unit 24. The lighting power for the light source 25 is supplied to the light source 25 via the lighting circuit unit 24.

[0037] (2.2.3) Communications section Communication unit 23 includes a communication interface for communicating with master terminal 1. More specifically, communication unit 23 performs power line communication with master terminal 1. Specifically, communication unit 23 superimposes a communication signal on AC power supplied via two of the three phases of three-phase power supply PS1 that are connected. The communication signal includes the address information and maintenance information described above. The maintenance information includes the cumulative lighting time of lighting device 20 (light source 25). That is, each of multiple slave terminals 2 transmits a communication signal including maintenance information, including the cumulative lighting time of lighting device 20, to master terminal 1.

[0038] (2.2.4) Lighting circuit section The lighting circuit unit 24 controls at least one of dimming and color adjustment of the light source 25. More specifically, the lighting circuit unit 24 controls at least one of dimming and color adjustment of the light source 25 in accordance with a control signal from the control unit 21. The control signal from the control unit 21 includes a control command included in the communication signal received from the parent terminal 1.

[0039] Here, assume that lighting fixture 20 serving as slave terminal 2 is a tunnel light installed near the entrance of a tunnel, and a passenger vehicle is entering the tunnel. In this case, if lighting fixture 20 is too dim, the so-called black hole phenomenon may prevent the driver of the passenger vehicle from seeing the road ahead. Therefore, tunnel lights installed near the entrance of a tunnel must be lit at an illuminance that corresponds to the distance from the entrance. For this reason, in this embodiment, control unit 11 of master terminal 1 controls the dimming of lighting fixture 20 based on information obtained from external device 3.

[0040] External device 3 is, for example, camera 30 installed near the entrance of a tunnel. Camera 30 captures images of the inside of the tunnel in accordance with a control signal from control unit 11 of master terminal 1 and calculates the luminance of the area near the entrance of the tunnel from the captured image. External device 3 then transmits a communication signal containing luminance information about the calculated luminance to master terminal 1. Control unit 11 of master terminal 1 calculates a dimming level for lighting device 20 based on the luminance information obtained from external device 3, and transmits a communication signal containing a control command (dimming command) to lighting device 20 to achieve the calculated dimming level to slave terminal 2.

[0041] (2.2.5) Light source The light source 25 has one or more light-emitting elements. The one or more light-emitting elements are, for example, LEDs (Light-Emitting Diodes). The light source 25 lights up the one or more light-emitting elements at a dimming level according to a control command (dimming command) from the master terminal 1. That is, in the power line communication system 100 according to the embodiment, each of the multiple slave terminals 2 dims the light of the light source 25 according to the control command included in the communication signal from the master terminal 1.

[0042] (3) Sensitivity test mode Next, a sensitivity test mode of the power line communication system 100 according to the embodiment will be described.

[0043] In the power line communication system 100 according to the embodiment, as described above, the operation mode is automatically switched from the communication mode to the sensitivity test mode during the test period (for example, at night). The sensitivity test mode is a mode for testing the reception sensitivity of the communication signal in each of the multiple slave terminals 2. A series of operations in the sensitivity test mode will be described below.

[0044] In the sensitivity test mode, the control unit 11 of the master terminal 1 outputs (superimposes) a test signal to the two phases to which each of the multiple slave terminals 2 is connected. More specifically, in the sensitivity test mode, the control unit 11 outputs the test signal between the corresponding two phases in the order of the first slave terminal 2A, the second slave terminal 2B, the third slave terminal 2C, and so on.

[0045] The following describes a case where a test signal is output to the first handset terminal 2A, the second handset terminal 2B, and the third handset terminal 2C.

[0046] First, in a sensitivity test mode, the control unit 11 of the master terminal 1 superimposes a test signal on the two phases (R phase and S phase) to which the first slave terminal 2A is connected. Meanwhile, in the sensitivity test mode, the control units 21 of the second slave terminal 2B and the third slave terminal 2C each detect the receiving sensitivity of the test signal (leakage signal) transmitted to the R phase or S phase via the stray capacitance SC1.

[0047] Next, in the sensitivity test mode, the control unit 11 of the master terminal 1 superimposes a test signal on the two phases (S phase and T phase) to which the second slave terminal 2B is connected. Meanwhile, in the sensitivity test mode, the control units 21 of the first slave terminal 2A and the third slave terminal 2C each detect the receiving sensitivity of the test signal (leakage signal) transmitted to the S phase or T phase via the stray capacitance SC1.

[0048] Next, in the sensitivity test mode, the control unit 11 of the master terminal 1 superimposes a test signal on the two phases (T phase and R phase) to which the third slave terminal 2C is connected. Meanwhile, in the sensitivity test mode, the control units 21 of the first slave terminal 2A and the second slave terminal 2B each detect the receiving sensitivity of the test signal (leakage signal) transmitted to the T phase or R phase via the stray capacitance SC1.

[0049] In the sensitivity test mode, the control unit 11 of the master terminal 1 changes the communication conditions in the communication mode when the reception sensitivity of the test signal (leakage signal) detected in at least one of the multiple slave terminals 2 exceeds a threshold. The communication conditions include, for example, the transmission frequency of the communication signal transmitted from the master terminal 1 to each slave terminal 2.

[0050] In the sensitivity test mode, the control unit 11 of the base terminal 1 changes the transmission frequency of the communication signal to each of the slave terminals 2 when the receiving sensitivity of the test signal exceeds a threshold. More specifically, in the sensitivity test mode, when the receiving sensitivity of the test signal exceeds a threshold, the control unit 11 sets the transmission frequency of the first communication signal to the first transmission frequency, the transmission frequency of the second communication signal to the second transmission frequency, and the transmission frequency of the third communication signal to the third transmission frequency. The first transmission frequency, the second transmission frequency, and the third transmission frequency are different from one another. In other words, when the receiving sensitivity of the test signal exceeds a threshold, the base terminal 1 sets the first transmission frequency of the first communication signal, the second transmission frequency of the second communication signal, and the third transmission frequency of the third communication signal to be different from one another.

[0051] The communication conditions may also include the receiving sensitivity of the communication signal in the communication mode. In this case, when the receiving sensitivity of the test signal exceeds a threshold, the control unit 11 of the master terminal 1 sets the receiving sensitivity of the communication signal in the communication mode to be higher than the first sensitivity and lower than the second sensitivity. The first sensitivity is, for example, the signal strength of the test signal (leakage signal) received via stray capacitance SC1 in the other two phases in the sensitivity test mode. The second sensitivity is, for example, the signal strength of the communication signal in the communication mode. This makes it possible for each slave terminal 2 to receive only the communication signal in the communication mode. In other words, it is possible to reduce the influence of the leakage signal received via stray capacitance SC1.

[0052] (4) Operation Next, the operation of the power line communication system 100 according to the embodiment will be described with reference to Fig. 3. In the example of Fig. 3, the master terminal 1 transmits a communication signal to each slave terminal 2 at a predetermined timing. This will be described in detail below.

[0053] The parent terminal 1 transmits a first communication signal to the first child terminal 2A during a first period T1 from time t1 to time t2. The first child terminal 2A receives the first communication signal transmitted from the parent terminal 1 during the first period T1.

[0054] Next, the base terminal 1 transmits a second communication signal to the second child terminal 2B during a second period T2 from time t3 to time t4. The second child terminal 2B receives the second communication signal transmitted from the base terminal 1 during the second period T2. The second period T2 is the period after the first period T1 and the fourth period T4 have elapsed. The fourth period T4 is the period from time t2 to time t3. In other words, the base terminal 1 transmits the second communication signal to the second child terminal 2B after the fourth period T4 has elapsed since transmitting the first communication signal to the first child terminal 2A.

[0055] Next, the base terminal 1 transmits a third communication signal to the third child terminal 2C during a third period T3 from time t5 to time t6. The third child terminal 2C receives the third communication signal transmitted from the base terminal 1 during the third period T3. The third period T3 is the period after the first period T1, the fourth period T4, and the second period T2 have elapsed. The fifth period T5 is the period from time t4 to time t5. In other words, the base terminal 1 transmits the third communication signal to the third child terminal 2C after the fifth period T5 has elapsed since transmitting the second communication signal to the second child terminal 2B.

[0056] In this embodiment, the time t1 when the first communication signal is transmitted is the first timing, the time t3 when the second communication signal is transmitted is the second timing, and the time t5 when the third communication signal is transmitted is the third timing. The interval between any two adjacent timings in time series among the first timing, second timing, and third timing is longer than the transmission time of the communication signals (first communication signal, second communication signal, third communication signal). In the example of FIG. 3, the interval between the first timing and the second timing is the sum of the first period T1 and the fourth period T4, and the transmission time of the first communication signal is the first period T1. The interval between the second timing and the third timing is the sum of the second period T2 and the fifth period T5, and the transmission time of the second communication signal is the second period T2. Therefore, as described above, the interval between any two adjacent timings in time series is longer than the transmission time of the communication signals.

[0057] (5) Effects In the power line communication system 100 according to the embodiment, as described above, the first timing for transmitting the first communication signal to the first child terminal 2A, the second timing for transmitting the second communication signal to the second child terminal 2B, and the third timing for transmitting the third communication signal to the third child terminal 2C are different from one another. This prevents leakage of signals from other phases when each child terminal 2 receives a communication signal from the parent terminal 1, making it possible to suppress degradation of communication quality.

[0058] In the power line communication system 100 according to the embodiment, the first transmission frequency of the first communication signal transmitted to the first child terminal 2A, the second transmission frequency of the second communication signal transmitted to the second child terminal 2B, and the third transmission frequency of the third communication signal transmitted to the third child terminal 2C are different from one another, which makes it possible to further suppress degradation of communication quality.

[0059] Furthermore, in the power line communication system 100 according to the embodiment, the interval between any two adjacent timings in time series among the first timing, the second timing, and the third timing is longer than the transmission time of the communication signal, so that it is possible to further suppress degradation of communication quality.

[0060] Furthermore, in the power line communication system 100 according to the embodiment, the specific slave terminal 2 transmits a secondary communication signal to the remaining slave terminals 2 excluding the master terminal 1 and the specific slave terminal 2, and then transmits a main communication signal to the master terminal 1 after a certain period of time has elapsed. This makes it possible to reduce the problem of collision between the communication signal transmitted from the specific slave terminal 2 and the communication signal transmitted from the remaining slave terminals 2 excluding the specific slave terminal 2.

[0061] Furthermore, the power line communication system 100 according to the embodiment has a sensitivity test mode for testing the reception sensitivity of the test signal (leakage signal) in each of the multiple slave terminals 2, and therefore it is possible to change the communication conditions in the communication mode depending on the test results of the sensitivity test mode.

[0062] Furthermore, in the power line communication system 100 according to the embodiment, when the receiving sensitivity of the test signal exceeds a threshold in the sensitivity test mode, the first transmission frequency, the second transmission frequency, and the third transmission frequency are made different from one another, thereby making it possible to reduce the influence of the leakage signal due to the stray capacitance SC1 between the phases.

[0063] Furthermore, in the power line communication system 100 according to the embodiment, the receiving sensitivity of the communication signal transmitted through the two phases to which each slave terminal 2 is connected is set to be greater than the signal strength of the leakage signal transmitted through the other two phases, and smaller than the signal strength of the communication signal transmitted through the above two phases, so that each slave terminal 2 can receive only the communication signal transmitted through the above two phases.

[0064] Furthermore, according to the power line communication system 100 according to the embodiment, it is possible to switch from the communication mode to the sensitivity test mode manually by operating a switch, or automatically during the test period.

[0065] Furthermore, in the power line communication system 100 according to the embodiment, each of the multiple slave terminals 2 changes the bandwidth of the transmission frequency of the communication signal according to the traffic volume of the communication signal to the master terminal 1, so that even if the traffic volume of the communication signal to the master terminal 1 is large, it is possible to transmit the communication signal to the master terminal 1.

[0066] Furthermore, according to the power line communication system 100 according to the embodiment, it is possible to dim each slave terminal 2, which is a lighting fixture 20, in accordance with a control command included in a communication signal.

[0067] Furthermore, according to the power line communication system 100 according to the embodiment, it is possible to transmit at least one of maintenance information and detection information to the master terminal 1.

[0068] (6) Variations The above-described embodiment is merely one of various embodiments of the present disclosure. The above-described embodiment can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. Modifications of the above-described embodiment are listed below. The modifications described below can be applied in appropriate combinations.

[0069] (6.1) Variation 1 Each of the multiple slave terminals 2 may further include a detection unit 26, as shown in Fig. 4. The slave terminal 2 according to Modification 1 will be described below with reference to Fig. 4. Note that, with regard to the slave terminal 2 according to Modification 1, the same components as those of the slave terminal 2 according to the embodiment will be denoted by the same reference numerals, and description thereof will be omitted.

[0070] As shown in FIG. 4, the slave terminal 2 according to the first modification includes a control unit 21, a power supply unit 22, a communication unit 23, a lighting circuit unit 24, a light source 25, and a detection unit 26.

[0071] The detection unit 26 is, for example, an ultrasonic sensor. The detection unit 26 is attached to, for example, the ceiling surface of the tunnel and detects passenger vehicles entering the tunnel. The detection unit 26 outputs detection information including the detection result to the control unit 21.

[0072] The control unit 21 generates a communication signal including the detection information acquired from the detection unit 26 and transmits the signal to the master terminal 1 via the communication unit 23. That is, in the power line communication system 100 according to the first modification, each of the multiple slave terminals 2 transmits to the master terminal 1 a communication signal including detection information including a detection result from the detection unit 26 that detects an object (passenger car) in the target space (tunnel). Here, each of the multiple slave terminals 2 may transmit to the master terminal 1 a communication signal including the detection information instead of the above-mentioned maintenance information, or may transmit to the master terminal 1 a communication signal including the detection information together with the above-mentioned maintenance information. That is, each of the multiple slave terminals 2 may transmit to the master terminal 1 a communication signal including at least one of the above-mentioned maintenance information and the above-mentioned detection information.

[0073] In the power line communication system 100 according to the first modification, it is possible to suppress a decrease in communication quality, similar to the power line communication system 100 according to the above embodiment.

[0074] (6.2) Variation 2 Before transmitting a communication signal to the master terminal 1, each of the slave terminals 2 may transmit a communication signal including information indicating that the communication signal will be transmitted to the master terminal 1. Hereinafter, a power line communication system 100 according to the second modification will be described.

[0075] In the power line communication system 100 according to the second modification, a specific slave terminal 2, which is one of the multiple slave terminals 2, transmits a secondary communication signal to the master terminal 1 and the remaining slave terminals 2 among the multiple slave terminals 2 excluding the specific slave terminal 2. Then, when a certain time has elapsed since transmitting the secondary communication signal, the specific slave terminal 2 transmits a main communication signal to the master terminal 1. The secondary communication signal is a communication signal including information indicating that the main communication signal will be transmitted to the master terminal 1. In other words, the secondary communication signal is a notification signal that notifies the master terminal 1 in advance that a main communication signal will be transmitted. The main communication signal is also a communication signal including information to be transmitted to the master terminal 1. Therefore, the data length of the secondary communication signal is shorter than the data length of the main communication signal.

[0076] Below, a case where the first child terminal 2A is the specific child terminal 2 out of the first child terminal 2A, the second child terminal 2B, and the third child terminal 2C will be described.

[0077] The first handset terminal 2A, which is the specific handset terminal 2, transmits a secondary communication signal to the base terminal 1, the second handset terminal 2B, and the third handset terminal 2C. By receiving the secondary communication signal, the base terminal 1, the second handset terminal 2B, and the third handset terminal 2C each recognize that the first handset terminal 2A plans to transmit a primary communication signal to the base terminal 1. The second handset terminal 2B and the third handset terminal 2C, which have received the secondary communication signal from the first handset terminal 2A, stop transmitting communication signals to the base terminal 1. Then, when a certain time has elapsed since the first handset terminal 2A transmitted the secondary communication signal, the first handset terminal 2A transmits a primary communication signal to the base terminal 1. On the other hand, the second handset terminal 2B and the third handset terminal 2C do not transmit communication signals to the base terminal 1 until the time when the first handset terminal 2A transmits the secondary communication signal and until the certain time has elapsed. That is, the remaining child terminals 2 (the second child terminal 2B and the third child terminal 2C) stop signal transmission until a certain time has elapsed since receiving the sub-communication signal.

[0078] The power line communication system 100 according to the second modification can reduce the problem of collision of communication signals from each slave terminal 2 to the master terminal 1. Also, the power line communication system 100 according to the second modification can suppress degradation of communication quality, similar to the power line communication system 100 according to the above-described embodiment.

[0079] (6.3) Other Modifications Other variations are listed below.

[0080] In the above-described embodiment, the three-phase power supply PS1 is a three-phase, three-wire delta connection, but may also be, for example, a three-phase, four-wire star connection.

[0081] In the above embodiment, the light emitting element of the light source 25 is an LED, but the light emitting element is not limited to an LED and may be, for example, an organic EL (Organic Electro-Luminescence).

[0082] In the above-described embodiment, each slave terminal 2 performs dimming in accordance with a control command included in the communication signal from the master terminal 1, but, for example, color adjustment may be performed instead of dimming, or color adjustment may be performed in addition to dimming. That is, in the power line communication system 100 according to the embodiment, it is sufficient that each of the multiple slave terminals 2 performs at least one of dimming and color adjustment in accordance with a control command included in the communication signal from the master terminal 1.

[0083] In the above-described embodiment, the operation mode of the power line communication system 100 is automatically switched from the communication mode to the sensitivity test mode during an inspection period (e.g., at night), but it may also be switched from the communication mode to the sensitivity test mode manually by operating a manual switch, for example. For example, immediately after the power line communication system 100 is installed or when the wiring situation changes, the operation mode of the power line communication system 100 is switched from the communication mode to the sensitivity test mode by a manual switch. That is, it is sufficient if the operation mode of the power line communication system 100 is switched from the communication mode to the sensitivity test mode manually by operating a switch, or automatically during an inspection period.

[0084] In the above embodiment, lighting fixture 20 is a tunnel light, but lighting fixture 20 may also be, for example, a street light. In this case, in power line communication system 100, for example, a timer is connected to master terminal 1, and when the time counted by the timer reaches a preset time, light source 25 of slave terminal 2 is turned on at a predetermined dimming level.

[0085] In the above-described first modification, the detection target of the detection unit 26 is a passenger car, but the detection target of the detection unit 26 is not limited to a passenger car, and may be, for example, a person walking in a tunnel.

[0086] In the above-described embodiment, the inspection period is nighttime, but the inspection period is not limited to nighttime and may be, for example, the period from the completion of construction to the start of operation.

[0087] Furthermore, the power line communication system 100 may be automatically switched to the sensitivity test mode when it is powered on, or may be manually switched to the sensitivity test mode.

[0088] As in the above-described embodiment, when lighting fixture 20 is a street light or a tunnel light, the wiring length of electric wires L1, L2, and L3 may be long, and therefore each slave terminal 2 may have a relay function. For example, in the first period T1 in FIG. 3 described above, when a first slave terminal 2A, among a plurality of first slave terminals 2A, that is located farthest from the master terminal 1, performs power line communication with the master terminal 1, one or more other first slave terminals 2A located between this first slave terminal 2A and the master terminal 1 relay the power line communication using the relay function. Similarly, in the second period T2 in FIG. 3 described above, when a second slave terminal 2B, among a plurality of second slave terminals 2B, that is located farthest from the master terminal 1, performs power line communication with the master terminal 1, one or more other second slave terminals 2B located between this second slave terminal 2B and the master terminal 1 relay the power line communication using the relay function. Similarly, in the third period T3 in Figure 3 described above, when the third child terminal 2C among the multiple third child terminals 2C that is located farthest from the parent terminal 1 performs power line communication with the parent terminal 1, one or more other third child terminals 2C located between this third child terminal 2C and the parent terminal 1 relay the power line communication using a relay function.

[0089] (Aspect) The present specification discloses the following aspects.

[0090] A power line communication system (100) according to a first aspect includes a master terminal (1) and a plurality of slave terminals (2) and has a communication mode. The master terminal (1) is connected to three phases of a three-phase power supply (PS1). The plurality of slave terminals (2) are each connected to any two of the three phases of the three-phase power supply (PS1). In the communication mode, power line communication is performed between the master terminal (1) and each of the plurality of slave terminals (2) and among the plurality of slave terminals (2). The plurality of slave terminals (2) include a first slave terminal (2A) having two phases of R and S, a second slave terminal (2B) having two phases of S and T, and a third slave terminal (2C) having two phases of T and R. The master terminal (1) transmits a communication signal including identification information for identifying the two phases to each of the plurality of slave terminals (2). In the power line communication system 100, the first timing, the second timing, and the third timing are different from one another. The first timing is the timing at which a first communication signal, which is a communication signal for the first handset terminal 2A, is transmitted to the first handset terminal 2A. The second timing is the timing at which a second communication signal, which is a communication signal for the second handset terminal 2B, is transmitted to the second handset terminal 2B. The third timing is the timing at which a third communication signal, which is a communication signal for the third handset terminal 2C, is transmitted to the third handset terminal 2C.

[0091] According to this aspect, it is possible to suppress a decrease in communication quality.

[0092] In the power line communication system (100) according to the second aspect, in the first aspect, the first transmission frequency which is the transmission frequency of the first communication signal, the second transmission frequency which is the transmission frequency of the second communication signal, and the third transmission frequency which is the transmission frequency of the third communication signal are different from each other.

[0093] According to this aspect, it is possible to further suppress the deterioration of communication quality.

[0094] In the power line communication system (100) according to the third aspect, in the first or second aspect, the interval between two timings adjacent in time series among the first timing, the second timing, and the third timing is longer than the transmission time of the communication signal.

[0095] According to this aspect, it is possible to further suppress the deterioration of communication quality.

[0096] In a power line communication system (100) according to a fourth aspect, in any one of the first to third aspects, a specific slave terminal (2) that is one of the multiple slave terminals (2) transmits a secondary communication signal including information indicating that a primary communication signal is to be transmitted to the master terminal (1), to the master terminal (1) and the remaining slave terminals (2) excluding the specific slave terminal (2). Furthermore, the specific slave terminal (2) transmits the primary communication signal to the master terminal (1) after a predetermined time has elapsed since transmitting the secondary communication signal. The remaining slave terminals (2) stop transmitting signals until a predetermined time has elapsed since receiving the secondary communication signal.

[0097] According to this aspect, it is possible to reduce the problem of collision between a communication signal transmitted from a specific slave terminal (2) and a communication signal transmitted from the remaining slave terminals (2) excluding the specific slave terminal (2).

[0098] A power line communication system (100) according to a fifth aspect is the same as that of the first aspect, but further includes a sensitivity test mode. In the sensitivity test mode, the reception sensitivity of a communication signal in each of the plurality of slave terminals (2) is tested. In the sensitivity test mode, the master terminal (1) outputs a test signal as a communication signal to two phases to which each of the plurality of slave terminals (2) is connected. In the sensitivity test mode, each of the plurality of slave terminals (2) detects the reception sensitivity of the test signal in two phases other than the corresponding two phases out of the three phases. When the reception sensitivity of the test signal detected in at least one of the plurality of slave terminals (2) exceeds a threshold, the master terminal (1) changes the communication conditions in the communication mode.

[0099] According to this aspect, it is possible to change the communication conditions in the communication mode in accordance with the test results in the sensitivity test mode.

[0100] In a power line communication system (100) according to a sixth aspect, in the fifth aspect, the communication conditions include a transmission frequency of the communication signal. When the receiving sensitivity of the test signal exceeds a threshold, the master terminal (1) makes a first transmission frequency, which is the transmission frequency of the first communication signal, a second transmission frequency, which is the transmission frequency of the second communication signal, and a third transmission frequency, which is the transmission frequency of the third communication signal, different from one another.

[0101] According to this aspect, by making the first transmission frequency, the second transmission frequency, and the third transmission frequency different from one another, it is possible to reduce the influence of leakage signals due to stray capacitance (SC1) between phases.

[0102] In a power line communication system (100) according to a seventh aspect, in the fifth or sixth aspect, the communication conditions include a receiving sensitivity of the communication signal. When the receiving sensitivity of the test signal exceeds a threshold, the master terminal (1) sets the receiving sensitivity of the communication signal lower than the signal strength of the communication signal in two phases to which each of the multiple slave terminals (2) is connected, and higher than the signal strength of the communication signal in the other two phases.

[0103] According to this aspect, it is possible for each slave terminal (2) to receive only the communication signals transmitted via the two phases to which the slave terminal (2) is connected.

[0104] In the power line communication system (100) according to the eighth aspect, in any one of the fifth to seventh aspects, the operation mode of the power line communication system (100) is switched from the communication mode to the sensitivity test mode manually by operating a switch or automatically during a test period.

[0105] According to this aspect, the operation mode of the power line communication system (100) can be switched manually or automatically from the communication mode to the sensitivity test mode.

[0106] In a power line communication system (100) according to a ninth aspect, in any one of the first to eighth aspects, each of the multiple slave terminals (2) changes the bandwidth of the transmission frequency of a specific communication signal, which is a communication signal to the master terminal (1), depending on the communication volume of the specific communication signal.

[0107] According to this aspect, even if the traffic of communication signals to the base terminal (1) is large, the communication signals can be transmitted to the base terminal (1).

[0108] In a power line communication system (100) according to a tenth aspect, in any one of the first to ninth aspects, each of the plurality of slave terminals (2) is a lighting fixture (20) that illuminates a target space. Each of the plurality of slave terminals (2) performs at least one of dimming and color adjustment in accordance with a control command included in the communication signal.

[0109] According to this aspect, it is possible to adjust at least one of the brightness and color of the lighting fixture (20) installed in the target space.

[0110] In a power line communication system (100) according to an eleventh aspect, in any one of the first to tenth aspects, each of the plurality of slave terminals (2) is a lighting fixture (20) that illuminates a target space. Each of the plurality of slave terminals (2) transmits a communication signal to the master terminal (1). The communication signal includes at least one of maintenance information including a cumulative lighting time of the lighting fixture (20) and detection information including a detection result of a detection unit (26) that detects an object in the target space.

[0111] According to this aspect, it is possible to transmit at least one of the maintenance information and the detection information to the base terminal (1).

[0112] The configurations according to the second to eleventh aspects are not essential for the power line communication system (100) and can be omitted as appropriate. [Explanation of symbols]

[0113] 1. Parent terminal 2. Sub-device terminal 2A First handset terminal 2B Second handset terminal 2C 3rd handset terminal 20 Lighting fixtures 26 Detection unit 100 Power Line Communication System PS1 three phase power supply SC1 Stray capacitance

Claims

1. A power line communication system comprising: a master terminal connected to three phases of a three-phase power supply; and a plurality of slave terminals, each connected to any two of the three phases of the three-phase power supply; and a communication mode for performing power line communication between the master terminal and each of the plurality of slave terminals, and between the plurality of slave terminals, The plurality of slave terminals include: a first slave terminal, the two phases of which are an R phase and an S phase; a second slave terminal, the two phases of which are the S phase and the T phase; a third child terminal, wherein the two phases are the T phase and the R phase; the master terminal transmits a communication signal including identification information for identifying the two phases to each of the plurality of slave terminals; a first timing that is a timing at which a first communication signal that is the communication signal for the first slave terminal is transmitted to the first slave terminal; a second timing at which a second communication signal, which is the communication signal for the second terminal, is transmitted to the second terminal; and a third timing which is a timing at which a third communication signal which is the communication signal for the third handset terminal is transmitted to the third handset terminal, which are different from each other. Power line communication system.

2. a first transmission frequency that is a transmission frequency of the first communication signal; a second transmission frequency that is a transmission frequency of the second communication signal; and a third transmission frequency which is a transmission frequency of the third communication signal, which are different from each other. The power line communication system according to claim 1 .

3. an interval between two timings adjacent in time series among the first timing, the second timing, and the third timing is longer than a transmission time of the communication signal; 3. The power line communication system according to claim 1 or 2.

4. a specific terminal among the plurality of terminals transmits a secondary communication signal to the base terminal and the remaining terminals among the plurality of terminals excluding the specific terminal, the secondary communication signal including information indicating that a main communication signal will be transmitted to the base terminal, and transmits the main communication signal to the base terminal after a predetermined time has elapsed since transmitting the secondary communication signal; the remaining slave terminals stop transmitting signals until the predetermined time has elapsed since receiving the sub-communication signal; 3. The power line communication system according to claim 1 or 2.

5. a sensitivity test mode for testing the reception sensitivity of the communication signal at each of the plurality of slave terminals; In the sensitivity test mode, the parent terminal outputs a test signal as the communication signal to the two phases to which each of the plurality of child terminals is connected; each of the plurality of slave terminals detects, in the sensitivity test mode, a reception sensitivity of the test signal in two phases other than the corresponding two phases among the three phases; the master terminal changes a communication condition in the communication mode when the reception sensitivity of the test signal detected by at least one of the plurality of slave terminals exceeds a threshold. The power line communication system according to claim 1 .

6. the communication conditions include a transmission frequency of the communication signal; when the receiving sensitivity of the test signal exceeds the threshold, the base terminal makes a first transmission frequency that is a transmission frequency of the first communication signal, a second transmission frequency that is a transmission frequency of the second communication signal, and a third transmission frequency that is a transmission frequency of the third communication signal different from one another; 6. The power line communication system according to claim 5.

7. the communication conditions include a receiving sensitivity of the communication signal; When the receiving sensitivity of the test signal exceeds the threshold, the parent terminal sets the receiving sensitivity of the communication signal lower than the signal strength of the communication signal in the two phases to which each of the plurality of child terminals is connected, and higher than the signal strength of the communication signal in the other two phases.

6. The power line communication system according to claim 5.

8. The operation mode of the power line communication system is switched from the communication mode to the sensitivity test mode manually by a switch operation or automatically during a test period. The power line communication system according to any one of claims 5 to 7.

9. each of the plurality of slave terminals changes a bandwidth of a transmission frequency of a specific communication signal, which is a communication signal to the master terminal, in accordance with a communication volume of the specific communication signal; 3. The power line communication system according to claim 1 or 2.

10. Each of the plurality of slave terminals A lighting fixture that illuminates a target space, At least one of dimming and color adjustment is performed in accordance with the control command included in the communication signal.

3. The power line communication system according to claim 1 or 2.

11. each of the plurality of slave terminals is a lighting fixture that illuminates a target space; each of the plurality of slave terminals transmits to the master terminal a communication signal including at least one of maintenance information including an accumulated lighting time of the lighting device and detection information including a detection result of a detection unit that detects an object in the target space; 3. The power line communication system according to claim 1 or 2.

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