Interface circuit, communication device, interface system, and communication system

Abstract

To provide a technology capable of improving the quality of communication signals.SOLUTION: An interface circuit includes a first coupler and a first low-pass filter. The first coupler superimposes a first communication signal onto a first power line that transmits a rectangular wave first power supply voltage, or extracts the first communication signal from the first power line that transmits the rectangular wave first power supply voltage with the first communication signal superimposed. The first low-pass filter is inserted into the first power line and connected to the first coupler. The first low-pass filter has a first inductor at each end of the first low-pass filter.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to an interface circuit for processing communication signals. [Background technology]

[0002] Patent Document 1 discloses a technology relating to power line communication. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-150621 Summary of the Invention [Problem to be solved by the invention]

[0004] There is room for improvement in the interface circuitry that processes communication signals.

[0005] Therefore, the present disclosure has been made in consideration of the above points, and aims to provide a technology that can improve the quality of communication signals. [Means for solving the problem]

[0006] One aspect of the interface circuit includes a first coupler and a first low-pass filter. The first coupler superimposes a first communication signal onto a first power line transmitting a first power supply voltage having a square wave, or extracts the first communication signal from the first power line transmitting the first power supply voltage having the first communication signal superimposed thereon. The first low-pass filter is inserted into the first power line and connected to the first coupler. The first low-pass filter has a first inductor on each end of the first low-pass filter.

[0007] A communication device according to one aspect includes the interface circuit described above and a communication unit that transmits a first communication signal to a first coupler. The first coupler superimposes the first communication signal transmitted from the communication unit onto a first power line.

[0008] Also, one aspect of a communication device includes the above-described interface circuit and a communication unit that receives a first communication signal extracted by a first coupler from a first power line on which the first communication signal is superimposed.

[0009] Another aspect of the interface system includes a first interface circuit, which is the above-described interface circuit, and a second interface circuit connected to the first interface circuit via a first power line. The first coupler superimposes a first communication signal on the first power line and is connected to a first inductor on the second interface circuit side of the first low-pass filter. The second interface circuit has a third coupler and a third low-pass filter. The third coupler extracts the first communication signal from the first power line on which the first communication signal is superimposed. The third low-pass filter is inserted into the first power line and connected to the third coupler. The third low-pass filter has third inductors on both ends of the third low-pass filter. The third coupler is connected to the third inductor on the first interface circuit side of the third low-pass filter.

[0010] Another aspect of a communication system includes the above-described interface system, a first communication unit, and a second communication unit. The first communication unit transmits a first communication signal to the first coupler. The second communication unit receives the first communication signal extracted by the third coupler from the first power line on which the first communication signal is superimposed.

[0011] Another aspect of the interface circuit includes a coupler and a low-pass filter. The coupler superimposes a communication signal onto a power line transmitting a DC power supply voltage, or extracts the communication signal from the power line transmitting the DC power supply voltage and having the communication signal superimposed thereon. The low-pass filter is inserted into the power line and electrically connected to the coupler. The low-pass filter has an inductor on each end of the low-pass filter. [Effects of the Invention]

[0012] The quality of the communication signal can be improved. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of the configuration of a processing system. [Figure 2] FIG. 2 is a schematic diagram illustrating an example of the configuration of a communication unit. [Figure 3] FIG. 1 is a schematic diagram illustrating an example of the configuration of a processing system. [Figure 4] 3A and 3B are schematic diagrams illustrating an example of gain frequency characteristics of a low-pass filter and a high-pass filter. [Figure 5] 3A and 3B are schematic diagrams illustrating an example of gain frequency characteristics of a low-pass filter and a high-pass filter. [Figure 6] FIG. 1 is a schematic diagram illustrating an example of the configuration of a processing system. [Figure 7] FIG. 1 is a schematic diagram illustrating an example of the configuration of a processing system. [Figure 8] FIG. 1 is a schematic diagram illustrating an example of the configuration of a processing system. [Figure 9] FIG. 1 is a schematic diagram illustrating an example of the configuration of a processing system. [Figure 10] FIG. 1 is a schematic diagram illustrating an example of the configuration of a processing system. [Figure 11] FIG. 1 is a schematic diagram illustrating an example of the configuration of a processing system. DETAILED DESCRIPTION OF THE INVENTION

[0014] Fig. 1 is a schematic diagram showing an example of a processing system 1. As shown in Fig. 1, the processing system 1 includes, for example, a load-side system 20 having a load 21, a power supply-side system 10 that outputs a power supply voltage to be supplied to the load 21, and a cable 60 that connects the load-side system 20 and the power supply-side system 10. The power supply voltage output by the power supply-side system 10 is supplied to the load-side system 20 through the cable 60. The power supply-side system 10 and the load-side system 20 can communicate with each other through the cable 60.

[0015] The power supply side system 10 includes, for example, a power supply unit 11 that outputs a power supply voltage to be supplied to a load 21. The power supply unit 11 and the load 21 are connected to each other by a power line 50 that transmits the power supply voltage output by the power supply unit 11. The power line 50 can transmit power to be supplied to the load 21. A cable 60 constitutes a part of the power line 50. The power line 50 is made up of a power supply side power line that transmits the power supply voltage within the power supply side system 10, the cable 60, and a load side power line that transmits the power supply voltage within the load side system 20.

[0016] The power supply side system 10 includes, for example, a power supply side communication device 12 (also simply referred to as communication device 12) in addition to the power supply unit 11. The load side system 20 includes, for example, a load side communication device 22 (also simply referred to as communication device 22) in addition to the load 21. The power supply side communication device 12 and the load side communication device 22 form a communication system 32.

[0017] The power supply side communication device 12 and the load side communication device 22 can perform power line communication (PLC) with each other, for example, via a power line 50. The communication method between the power supply side communication device 12 and the load side communication device 22 may be HD-PLC or another method. HD-PLC is a registered trademark and is an abbreviation for High Definition Power Line Communication.

[0018] The power supply side communication device 12 includes, for example, a power supply side communication unit 13 (also simply referred to as communication unit 13) and a power supply side interface circuit 14 (also simply referred to as interface circuit 14). The power supply side interface circuit 14 is inserted into the power line 50. The power supply voltage output by the power supply unit 11 is input to a cable 60 via the interface circuit 14.

[0019] The interface circuit 14 is capable of, for example, performing low-pass filtering on the power supply voltage output by the power supply unit 11. The power supply voltage that has been subjected to low-pass filtering by the interface circuit 14 is input to the cable 60.

[0020] The load-side communication device 22 includes, for example, a load-side communication unit 23 (also simply referred to as the communication unit 23) and a load-side interface circuit 24 (also simply referred to as the interface circuit 24). The load-side interface circuit 24 is inserted into the power line 50. The power supply voltage transmitted to the load-side system 20 by the cable 60 is supplied to the load 21 through the interface circuit 24.

[0021] The interface circuit 24 is capable of, for example, performing low-pass filtering on the input power supply voltage, and supplies the power supply voltage after the low-pass filtering to the load 21.

[0022] The power supply side communication unit 13 and the load side communication unit 23 can communicate with each other via the power line 50, the power supply side interface circuit 14, and the load side interface circuit 24. The power supply side interface circuit 14 and the load side interface circuit 24 constitute an interface system 34. The power supply side communication unit 13 and the load side communication unit 23 can communicate with each other via the power line 50 and the interface system 34.

[0023] The communication units 13 and 23 may perform two-way communication or one-way communication. In the former case, the communication units 13 and 23 each function as a transmitting / receiving unit, and the communication devices 12 and 22 each function as a transmitting / receiving device. On the other hand, in the latter case, the communication units 13 and 23 may each function as a transmitting unit and a receiving unit, and the communication devices 12 and 22 may each function as a transmitting device and a receiving device. Alternatively, the communication units 13 and 23 may each function as a receiving unit and a transmitting unit, and the communication devices 12 and 22 may each function as a receiving device and a transmitting device.

[0024] For example, consider a case where communication unit 13 transmits a communication signal and communication unit 23 receives the communication signal from communication unit 13. In this case, interface circuit 14 superimposes the communication signal transmitted by communication unit 13 onto power line 50. In other words, interface circuit 14 superimposes the communication signal transmitted by communication unit 13 on the power supply voltage transmitted by power line 50. Meanwhile, interface circuit 24 extracts the communication signal from power line 50 on which the communication signal is superimposed. Communication unit 23 receives the communication signal extracted by interface circuit 24.

[0025] Also consider a case where communication unit 23 transmits a communication signal and communication unit 13 receives the communication signal from communication unit 23. In this case, interface circuit 24 superimposes the communication signal transmitted by communication unit 23 onto power line 50. In other words, interface circuit 24 superimposes the communication signal transmitted by communication unit 23 on the power supply voltage transmitted by power line 50. Meanwhile, interface circuit 14 extracts the communication signal from power line 50 on which the communication signal is superimposed. Communication unit 13 receives the communication signal extracted by interface circuit 14.

[0026] 2 is a schematic diagram showing an example of the configuration of the power supply side communication unit 13 and the load side communication unit 23. In this example, the configuration of the power supply side communication unit 13 and the configuration of the load side communication unit 23 are the same, but they may be different. Hereinafter, when there is no need to distinguish between the power supply side communication unit 13 and the load side communication unit 23, they may be simply referred to as communication units. Furthermore, the power supply side interface circuit 14 or the load side interface circuit 24 connected to the communication units may be simply referred to as interface circuits.

[0027] 2, the communication unit includes, for example, a control unit 40, a storage unit 41, and an RF front-end circuit 42. RF is an abbreviation for Radio Frequency. The communication unit can also be referred to as, for example, a communication circuit.

[0028] The control unit 40 can comprehensively manage the operation of the communication unit by controlling the other components of the communication unit. The control unit 40 can also be called, for example, a control circuit. The control unit 40 includes, for example, at least one processor. The at least one processor may include, for example, a CPU (Central Processing Unit).

[0029] The storage unit 41 may include a non-transitory recording medium readable by the CPU of the control unit 40, such as a read-only memory (ROM) and a random access memory (RAM). The storage unit 41 stores, for example, a program 41a for controlling the communication unit. Various functions of the control unit 40 are realized, for example, by the CPU of the control unit 40 executing the program 41a in the storage unit 41.

[0030] When the communication unit transmits a communication signal to the interface circuit, the control unit 40 generates the communication signal (also referred to as a transmission signal) and inputs it to the RF front-end circuit 42. The control unit 40 generates the communication signal by, for example, performing digital modulation processing using information to be transmitted. The communication signal can also be referred to as a modulated signal. The modulation method used by the control unit 40 may be, for example, FSK, QPSK, or another method. The control unit 40 may use MSK, which is a type of FSK. FSK is an abbreviation for Frequency Shift Keying, MSK is an abbreviation for Minimum Shift Keying, and QPSK is an abbreviation for Quadrature Phase Shift Keying.

[0031] When the communication unit transmits a communication signal to the interface circuit, the RF front-end circuit 42 converts, for example, a digital communication signal input from the control unit 40 into an analog format. Then, the RF front-end circuit 42 transmits the analog communication signal to the interface circuit. At this time, the RF front-end circuit 42 may amplify the analog communication signal and transmit the amplified communication signal to the interface circuit. The RF front-end circuit 42 may also convert a single-ended communication signal generated by the control unit 40 into a differential format and transmit the signal, or may transmit the communication signal generated by the control unit 40 in its single-ended format. The control unit 40 may also convert the generated digital communication signal into an analog format and input the analog communication signal to the RF front-end circuit 42.

[0032] When the communication unit receives a communication signal, the RF front-end circuit 42 receives the communication signal extracted by the interface circuit from the power line 50 and performs, for example, attenuation and filtering on the received communication signal. The RF front-end circuit 42 then converts the attenuated and filtered communication signal from analog to digital format and inputs the digital communication signal to the control unit 40. When receiving a differential communication signal, the RF front-end circuit 42 may convert the communication signal from differential format to single-ended format and input it to the control unit 40. The control unit 40 performs demodulation processing and the like on the communication signal (also referred to as a received signal) input from the RF front-end circuit 42 to obtain information contained in the communication signal. Note that the RF front-end circuit 42 may input the analog communication signal to the control unit 40, and the control unit 40 may convert the input communication signal from analog format to digital format.

[0033] The configuration of the communication unit is not limited to the above example. For example, the control unit 40 may include multiple CPUs. The control unit 40 may also include at least one DSP (Digital Signal Processor). All or some of the functions of the control unit 40 may be realized by a hardware circuit that does not require software to realize the function. The storage unit 41 may also include a computer-readable non-transitory recording medium other than ROM and RAM. The communication unit may also include a microcomputer having the control unit 40 and the storage unit 41.

[0034] The load 21 included in the load-side system 20 may be any type. For example, the load 21 may be an actuator. In this case, the load 21 may be a motor, a hydraulic actuator, a pneumatic actuator, or an electric actuator that does not use a motor.

[0035] <Example of processing system> A specific example of the processing system 1 will be described below. FIG. 3 is a schematic diagram showing an example of the processing system 1 when the load 21 is a brushless DC motor or an AC servo motor driven by three-phase power. DC is an abbreviation for Direct Current. AC is an abbreviation for Alternating Current. Hereinafter, when there is no need to particularly distinguish between the brushless DC motor and the AC servo motor, they will each be simply referred to as a motor.

[0036] The motor is also called a three-phase motor and has three coils. The three coils may be connected in a star or delta configuration. The motor serving as the load 21 may be used to drive a robot, a belt conveyor, or any other application. Hereinafter, the term "motor" will refer to the motor serving as the load 21.

[0037] In the processing system 1 (also referred to as processing system 1A) shown in FIG. 3 , a power supply unit 11 outputs a power supply voltage to a motor. A power line 50 transmits the power supply voltage output from the power supply unit 11 to the motor. The power line 50 is a three-phase power line and is composed of a U-phase power line 51, a V-phase power line 52, and a W-phase power line 53. The U-phase power line 51, the V-phase power line 52, and the W-phase power line 53 each extend from the power supply unit 11 to the motor. A cable 60 connecting the power supply side system 10 and the load side system 20 constitutes a part of each of the U-phase power line 51, the V-phase power line 52, and the W-phase power line 53.

[0038] The power supply unit 11 includes, for example, an inverter circuit. The power supply unit 11 can also be referred to as, for example, a power supply circuit. The inverter circuit generates and outputs a U-phase voltage, a V-phase voltage, and a W-phase voltage. A U-phase power line 51 transmits the U-phase voltage output by the power supply unit 11 to the motor. A V-phase power line 52 transmits the V-phase voltage output by the power supply unit 11 to the motor. A W-phase power line 53 transmits the W-phase voltage output by the power supply unit 11 to the motor. Each of the U-phase voltage, V-phase voltage, and W-phase voltage is a rectangular wave voltage, and can be referred to as a rectangular wave power supply voltage for the motor. The rectangular wave voltage includes a fundamental wave component and a harmonic component. The brushless motor is PWM-controlled by supplying the rectangular wave U-phase voltage, V-phase voltage, and W-phase voltage to the motor. PWM stands for Pulse Width Modulation. The maximum values ​​of the U-phase voltage, V-phase voltage, and W-phase voltage are, for example, several hundred volts.

[0039] The power supply side interface circuit 14 is inserted into the U-phase power line 51, the V-phase power line 52, and the W-phase power line 53. The interface circuit 14 is capable of performing low-pass filtering on the U-phase voltage, the V-phase voltage, and the W-phase voltage output from the power supply unit 11. The U-phase voltage, the V-phase voltage, and the W-phase voltage that have been low-pass filtered by the interface circuit 14 are input to the cable 60.

[0040] The interface circuit 14 performs low-pass filtering on the U-phase voltage, passing the fundamental component of the U-phase voltage and attenuating the harmonic components of the U-phase voltage. The interface circuit 14 performs low-pass filtering on the V-phase voltage, passing the fundamental component of the V-phase voltage and attenuating the harmonic components of the V-phase voltage. The interface circuit 14 performs low-pass filtering on the W-phase voltage, passing the fundamental component of the W-phase voltage and attenuating the harmonic components of the W-phase voltage. The cable 60 receives the U-phase voltage, which includes a fundamental component and harmonic components attenuated by the interface circuit 14; the V-phase voltage, which includes a fundamental component and harmonic components attenuated by the interface circuit 14; and the W-phase voltage, which includes a fundamental component and harmonic components attenuated by the interface circuit 14. The fundamental components of the U-phase voltage, V-phase voltage, and W-phase voltage have the same frequency, e.g., several kHz. Note that the frequencies of the fundamental components of the U-phase voltage, V-phase voltage, and W-phase voltage are not limited to this.

[0041] The load-side interface circuit 24 is inserted into the U-phase power line 51, the V-phase power line 52, and the W-phase power line 53. The interface circuit 24 is capable of performing low-pass filtering on the U-phase voltage, the V-phase voltage, and the W-phase voltage transmitted to the load-side system 20 via the cable 60. The U-phase voltage, the V-phase voltage, and the W-phase voltage that have been low-pass filtered by the interface circuit 24 are supplied to the load 21, i.e., the motor.

[0042] The interface circuit 24 performs low-pass filtering on the U-phase voltage, passing the fundamental component of the U-phase voltage and attenuating the harmonic components of the U-phase voltage. The interface circuit 24 performs low-pass filtering on the V-phase voltage, passing the fundamental component of the V-phase voltage and attenuating the harmonic components of the V-phase voltage. The interface circuit 24 performs low-pass filtering on the W-phase voltage, passing the fundamental component of the W-phase voltage and attenuating the harmonic components of the W-phase voltage. The motor receives the U-phase voltage, which includes the fundamental component and harmonic components attenuated by the interface circuit 24; the V-phase voltage, which includes the fundamental component and harmonic components attenuated by the interface circuit 24; and the W-phase voltage, which includes the fundamental component and harmonic components attenuated by the interface circuit 24.

[0043] As described above, in the processing system 1A, the U-phase voltage, V-phase voltage, and W-phase voltage output by the power supply unit 11 are supplied to the motor after being low-pass filtered by the interface circuits 14 and 24. This reduces high-frequency noise contained in the power supply voltage of the motor.

[0044] In the processing system 1A, the power supply side communication device 12 and the load side communication device 22 can perform, for example, bidirectional communication. Furthermore, the power supply side communication device 12 and the load side communication device 22 can perform, for example, differential communication. The power supply side communication unit 13 transmits a differential communication signal (also called a differential signal), and the load side communication unit 23 can receive the differential signal transmitted by the power supply side communication unit 13. Furthermore, the load side communication unit 23 transmits a differential signal, and the power supply side communication unit 13 can receive the differential signal transmitted by the load side communication unit 23. The maximum voltage of the differential signal is, for example, several volts.

[0045] Hereinafter, the differential signal transmitted by the communication unit 13 may be referred to as the power supply side differential signal, and the differential signal transmitted by the communication unit 23 may be referred to as the load side differential signal. Furthermore, each of the two paired communication signals constituting the power supply side differential signal may be referred to as the power supply side communication signal. Furthermore, each of the two paired communication signals constituting the load side differential signal may be referred to as the load side communication signal.

[0046] The power supply side interface circuit 14 superimposes the power supply side differential signals transmitted by the communication unit 13 onto two of the U-phase power line 51, the V-phase power line 52, and the W-phase power line 53. Specifically, the power supply side interface circuit 14 superimposes a pair of power supply side communication signals transmitted by the communication unit 13 onto two of the U-phase power line 51, the V-phase power line 52, and the W-phase power line 53, respectively.

[0047] 3 , the power supply side differential signal is superimposed on the U-phase power line 51 and the V-phase power line 52. The interface circuit 14 superimposes one power supply side communication signal on the U-phase voltage (i.e., square wave voltage) transmitted by the U-phase power line 51, and superimposes the other power supply side communication signal on the V-phase voltage (i.e., square wave voltage) transmitted by the V-phase power line 52. The U-phase power line 51 transmits the superimposed power supply side communication signal to the load side interface circuit 24, and the V-phase power line 52 transmits the superimposed power supply side communication signal to the load side interface circuit 24. The power supply side differential signal may be superimposed on the U-phase power line 51 and the W-phase power line 53, or on the V-phase power line 52 and the W-phase power line 53.

[0048] The load-side interface circuit 24 superimposes the load-side differential signal transmitted by the communication unit 23 onto two of the U-phase power line 51, the V-phase power line 52, and the W-phase power line 53. In the example of FIG. 3 , the load-side differential signal is superimposed onto the U-phase power line 51 and the V-phase power line 52. The interface circuit 24 superimposes one load-side communication signal onto the U-phase power line 51 and the other load-side communication signal onto the V-phase power line 52. The U-phase power line 51 transmits the superimposed load-side communication signal to the interface circuit 14, and the V-phase power line 52 transmits the superimposed load-side communication signal to the interface circuit 14. The load-side differential signal may be superimposed onto the U-phase power line 51 and the W-phase power line 53, or onto the V-phase power line 52 and the W-phase power line 53.

[0049] The power supply side interface circuit 14 extracts the load side differential signals from the U-phase power line 51 and the V-phase power line 52 on which the load side differential signals are superimposed, and outputs the extracted load side differential signals to the power supply side communication unit 13. The communication unit 13 receives the load side differential signals extracted by the interface circuit 14. The interface circuit 14 extracts one of the load side communication signals from the U-phase power line 51 on which the load side communication signal is superimposed, and outputs the extracted load side communication signal to the communication unit 13. The interface circuit 14 also extracts the other of the load side communication signals from the V-phase power line 52 on which the other load side communication signal is superimposed, and outputs the extracted load side communication signal to the communication unit 13.

[0050] The load-side interface circuit 24 extracts the power supply-side differential signals from the U-phase power line 51 and the V-phase power line 52 on which the power supply-side differential signals are superimposed, and outputs the power supply-side differential signals to the load-side communication unit 23. The communication unit 23 receives the power supply-side differential signals extracted by the interface circuit 24. The interface circuit 24 extracts one of the power supply-side communication signals from the U-phase power line 51 on which the power supply-side communication signal is superimposed, and outputs the same to the communication unit 23. The interface circuit 24 also extracts the other power supply-side communication signal from the V-phase power line 52 on which the other power supply-side communication signal is superimposed, and outputs the same to the communication unit 23.

[0051] In the processing system 1, as shown in FIG. 3, the load side system 20 may be provided with a sensor 29 that detects the state of the load 21, and the power supply side system 10 may be provided with a control device 19 that controls the power supply unit 11 based on the detection results of the sensor 29.

[0052] If the load 21 is a brushless DC motor, the sensor 29 has, for example, a Hall sensor that detects the rotational position of the brushless DC motor. The sensor 29 outputs sensor information indicating the detection result of the Hall sensor to the load-side communication unit 23. The sensor 29 may also include a Hall sensor and an encoder that detects the rotational speed of the brushless DC motor. In this case, the sensor 29 outputs sensor information indicating the detection result of the Hall sensor and the detection result of the encoder to the load-side communication unit 23. If the load 21 is an AC servo motor, the sensor 29 has, for example, an encoder that detects the rotational speed of the AC servo motor. The sensor 29 outputs sensor information indicating the detection result of the encoder to the load-side communication unit 23.

[0053] The load-side communication unit 23 transmits a load-side differential signal including sensor information from the sensor 29. The power-supply-side communication unit 13 receives the load-side differential signal including the sensor information. In the power-supply-side communication unit 13, the control unit 40 acquires the sensor information included in the load-side differential signal received by the RF front-end circuit 42. The sensor information acquired by the control unit 40 is input to the control device 19.

[0054] The control device 19 controls the inverter circuit of the power supply unit 11 based on the sensor information from the power supply side communication unit 13. The control device 19 controls the inverter circuit of the power supply unit 11 based on the sensor information, for example, so that the rotational position or rotational speed of the motor reaches a target value. The control device 19 can control the rotation of the motor through the power supply unit 11.

[0055] The sensor 29 outputs sensor information in response to an output request from, for example, the control device 19. The control device 19 transmits output request information indicating an output request for sensor information to the power supply side communication unit 13. The power supply side communication unit 13 transmits a power supply side differential signal including the output request information from the control device 19. The load side communication unit 23 receives the power supply side differential signal including the output request information. In the load side communication unit 23, the control unit 40 acquires the output request information included in the power supply side differential signal received by the RF front-end circuit 42. The load side communication unit 23 outputs the acquired output request information to the sensor 29. The sensor 29 outputs sensor information in response to receiving the output request information. The sensor information output from the sensor 29 is input to the control device 19.

[0056] 3 can be considered to be, for example, a servo system that controls a motor. The power supply side system 10 can be considered to be, for example, a servo amplifier, and the load side system 20 can be considered to be, for example, a servo motor or a servo actuator.

[0057] <Configuration example of power supply side interface circuit> The power supply side interface circuit 14 includes, for example, a low-pass filter section LPG1 having a plurality of low-pass filters LP11, LP12, and LP13, and a coupler section CPG1 having a plurality of couplers CP11 and CP12.

[0058] The low-pass filter unit LPG1 is inserted into the U-phase power line 51, the V-phase power line 52, and the W-phase power line 53. The low-pass filter unit LPG1 performs low-pass filtering on the U-phase voltage, the V-phase voltage, and the W-phase voltage output from the power supply unit 11.

[0059] The coupler unit CPG1 is connected to the end of the low-pass filter unit LPG1 on the interface circuit 24 side. The coupler unit CPG1 superimposes the power supply side differential signals transmitted by the communication unit 13 onto the U-phase power line 51 and the V-phase power line 52 on the interface circuit 24 side (in other words, the cable 60 side) of the low-pass filter unit LPG1. The coupler unit CPG1 superimposes a pair of power supply side communication signals on the U-phase voltage and the V-phase voltage that have been low-pass filtered by the low-pass filter unit LPG1. The coupler unit CPG1 also extracts the load side differential signals from the U-phase power line 51 and the V-phase power line 52 on which the load side differential signals are superimposed, and outputs them to the communication unit 13.

[0060] <Coupler section configuration example> The coupler unit CPG1 includes, for example, capacitors C15 and C16, an isolation transformer T11, and resistors R11 and R12. The isolation transformer T11 has a primary coil L17 and a secondary coil L18. The primary coil L17 is connected to the communication unit 13. One end of the resistor R11 is connected to one end of the primary coil L17. One end of the resistor R12 is connected to the other end of the primary coil L17. The other end of the resistor R11 is connected to the other end of the resistor R12. A bias voltage Vb1 is applied to the other end of the resistor R11 and the other end of the resistor R12. The bias voltage Vb1 is applied to one end of the primary coil L17 via the resistor R11. The bias voltage Vb1 is applied to the other end of the primary coil L17 via the resistor R12. Both ends of the secondary coil L18 are connected to one end of the capacitors C15 and C16, respectively. The other ends of the capacitors C15 and C16 are connected to the U-phase power line 51 and the V-phase power line 52, respectively.

[0061] The primary coil L17 receives a power supply differential signal transmitted by the communication unit 13. One power supply communication signal of the power supply differential signals output from the secondary coil L18 is input to one end of the capacitor C15. The other power supply communication signal of the power supply differential signals output from the secondary coil L18 is input to one end of the capacitor C16.

[0062] When the load side differential signals are superimposed on the U-phase power line 51 and the V-phase power line 52, one of the load side communication signals superimposed on the U-phase power line 51 is input to the other end of the capacitor C15, and the other load side communication signal superimposed on the V-phase power line 52 is input to the other end of the capacitor C16.

[0063] Capacitor C15, isolation transformer T11, and resistor R11 form coupler CP11 that superimposes one power supply side communication signal transmitted by communication unit 13 onto U-phase power line 51. One power supply side communication signal of the power supply side differential signals output from secondary coil L18 is superimposed onto U-phase power line 51 via capacitor C15.

[0064] The coupler CP11 can extract one of the load-side communication signals superimposed on the load-side differential signal from the U-phase power line 51. The one of the load-side communication signals extracted from the U-phase power line 51 through the capacitor C15 is input to the communication unit 13 through the isolation transformer T11.

[0065] Capacitor C16, isolation transformer T11, and resistor R12 form coupler CP12 that superimposes the other power supply side communication signal transmitted by communication unit 13 onto V-phase power line 52. The other power supply side communication signal of the power supply side differential signals output from secondary coil L18 is superimposed onto V-phase power line 52 via capacitor C16.

[0066] The coupler CP12 can extract the other load-side communication signal from the V-phase power line 52 on which the other load-side communication signal of the load-side differential signal is superimposed. The other load-side communication signal extracted from the V-phase power line 52 through the capacitor C16 is input to the communication unit 13 through the isolation transformer T11.

[0067] The coupler CP11 constitutes a high-pass filter HP11. That is, the capacitor C15, the isolation transformer T11, and the resistor R11 constitute the high-pass filter HP11. The order of the high-pass filter HP11 is, for example, even. Specifically, the order of the high-pass filter HP11 is second. The high-pass filter HP11 performs high-pass filtering on one of the power supply side communication signals transmitted by the communication unit 13. The one of the power supply side communication signals that has been high-pass filtered by the high-pass filter HP11 is superimposed on the U-phase power line 51. The high-pass filter HP11 also performs high-pass filtering on one of the load side communication signals extracted from the U-phase power line 51. The one of the load side communication signals that has been high-pass filtered by the high-pass filter HP11 is received by the communication unit 13.

[0068] The coupler CP12 constitutes a high-pass filter HP12. That is, the capacitor C16, the isolation transformer T11, and the resistor R12 constitute the high-pass filter HP12. The order of the high-pass filter HP12 is, for example, even. Specifically, the order of the high-pass filter HP12 is second. The high-pass filter HP12 performs high-pass filtering on the other power supply side communication signal transmitted by the communication unit 13. The other power supply side communication signal that has been high-pass filtered by the high-pass filter HP12 is superimposed on the V-phase power line 52. The high-pass filter HP12 also performs high-pass filtering on the other load side communication signal extracted from the V-phase power line 52. The other load side communication signal that has been high-pass filtered by the high-pass filter HP12 is received by the communication unit 13.

[0069] <Example of low-pass filter configuration> The low-pass filter unit LPG1 includes, for example, inductors L11, L12, L13, L14, L15, and L16, and capacitors C11, C12, and C13. The inductors L11 and L12 are connected in series to each other and inserted into the U-phase power line 51. One end of the inductor L11 is connected to the power supply unit 11, and the other end of the inductor L11 is connected to one end of the inductor L12. The other end of the inductor L12 is connected to the other end of the capacitor C15 of the coupler CP11 and the cable 60. The U-phase voltage output by the power supply unit 11 is input to one end of the inductor L11.

[0070] Inductors L13 and L14 are connected in series to each other and inserted into the V-phase power line 52. One end of inductor L13 is connected to the power supply unit 11, and the other end of inductor L13 is connected to one end of inductor L14. The other end of inductor L14 is connected to the other end of capacitor C16 of coupler CP12 and to the cable 60. The V-phase voltage output by the power supply unit 11 is input to one end of inductor L13.

[0071] Inductors L15 and L16 are connected in series to each other and inserted into the W-phase power line 53. One end of inductor L15 is connected to the power supply unit 11, and the other end of inductor L15 is connected to one end of inductor L16. The other end of inductor L16 is connected to the cable 60. The W-phase voltage output by the power supply unit 11 is input to one end of inductor L15.

[0072] One end of capacitor C11 is connected to the other end of inductor L11 and one end of inductor L12. The other end of capacitor C11 is connected to the other end of inductor L13 and one end of inductor L14. One end of capacitor C12 is connected to the other end of inductor L13 and one end of inductor L14. The other end of capacitor C12 is connected to the other end of inductor L15 and one end of inductor L16. One end of capacitor C13 is connected to the other end of inductor L15 and one end of inductor L16. The other end of capacitor C13 is connected to the other end of inductor L11 and one end of inductor L12.

[0073] In the low-pass filter unit LPG1, inductors L11 and L12 and capacitors C11, C12, and C13 form a low-pass filter LP11 that performs low-pass filtering on the U-phase voltage transmitted by the U-phase power line 51 (in other words, the U-phase voltage output by the power supply unit 11). The U-phase voltage that has been low-pass filtered by the low-pass filter LP11 is transmitted to the load-side system 20 via a cable 60. The U-phase voltage that has been low-pass filtered by the low-pass filter LP11 is not a sinusoidal voltage but a square-wave voltage that includes a fundamental component and harmonic components (more specifically, harmonic components that are attenuated compared to before being low-pass filtered). The order of the low-pass filter LP11 is, for example, an odd order. Specifically, the order of the low-pass filter LP11 is third order.

[0074] In addition, in the low-pass filter unit LPG1, inductors L13 and L14 and capacitors C11, C12, and C13 form a low-pass filter LP12 that performs low-pass filtering on the V-phase voltage transmitted by the V-phase power line 52 (in other words, the V-phase voltage output by the power supply unit 11). The V-phase voltage that has been low-pass filtered by the low-pass filter LP12 is transmitted to the load-side system 20 via a cable 60. The V-phase voltage that has been low-pass filtered by the low-pass filter LP12 is not a sinusoidal voltage but a rectangular wave voltage that includes a fundamental wave component and harmonic components. The order of the low-pass filter LP12 is, for example, an odd order. Specifically, the order of the low-pass filter LP12 is third order.

[0075] In addition, in the low-pass filter unit LPG1, inductors L15 and L16 and capacitors C11, C12, and C13 form a low-pass filter LP13 that performs low-pass filtering on the W-phase voltage transmitted by the W-phase power line 53 (in other words, the W-phase voltage output by the power supply unit 11). The W-phase voltage that has been low-pass filtered by the low-pass filter LP13 is transmitted to the load-side system 20 via a cable 60. The W-phase voltage that has been low-pass filtered by the low-pass filter LP13 is not a sinusoidal voltage but a rectangular wave voltage that includes a fundamental wave component and harmonic components. The order of the low-pass filter LP13 is, for example, an odd order. Specifically, the order of the low-pass filter LP13 is third order.

[0076] As described above, in the interface circuit 14, the low-pass filters LP11, LP12, and LP13 perform low-pass filtering on the U-phase voltage, the V-phase voltage, and the W-phase voltage, thereby attenuating harmonic components contained in the U-phase voltage, the V-phase voltage, and the W-phase voltage. Therefore, high-frequency noise caused by the U-phase voltage, the V-phase voltage, and the W-phase voltage is less likely to be transmitted to the power supply-side communication unit 13, thereby improving the communication quality (also simply referred to as communication quality) between the power supply-side communication unit 13 and the load-side communication unit 23. Furthermore, high-frequency noise caused by the U-phase voltage, the V-phase voltage, and the W-phase voltage is less likely to be transmitted to the load-side system 20. For example, high-frequency noise is less likely to be transmitted to the load 21. Furthermore, high-frequency noise caused by the U-phase voltage, the V-phase voltage, and the W-phase voltage is less likely to be transmitted to the load-side communication unit 23, thereby improving the communication quality. The high-frequency noise caused by the U-phase voltage, the V-phase voltage, and the W-phase voltage can also be considered to be high-frequency noise generated in the power supply unit 11.

[0077] Furthermore, even if high frequency noise occurs in at least one of the power supply side communication unit 13 and the load side system 20, the high frequency noise is less likely to be transmitted to the power supply unit 11 by the low pass filters LP11, LP12, and LP13.

[0078] Furthermore, in this example, since the couplers CP11 and CP12 of the coupler unit CPG1 function as high-pass filters HP11 and HP12, even if low-frequency noise occurs in the power supply side communication unit 13, the low-frequency noise is less likely to be superimposed on the U-phase power line 51 and the V-phase power line 52. Therefore, the low-frequency noise is less likely to be transmitted to the power supply unit 11 and the load side system 20. Since the low-frequency noise is less likely to be transmitted to the load side communication unit 23 of the load side system 20, communication quality can be improved. Furthermore, even if low-frequency noise occurs in at least one of the power supply unit 11 and the load side system 20, the low-frequency noise is less likely to be transmitted to the power supply side communication unit 13, so communication quality can be improved.

[0079] In this example, the low-pass filter LP11 inserted in the U-phase power line 51 has inductors L11 and L12 on both ends thereof. The inductor L12 on the coupler CP11 side functions as an impedance upper for the power supply communication signal that the coupler CP11 superimposes on the U-phase power line 51, making it difficult for the power supply communication signal superimposed on the U-phase power line 51 to propagate toward the power supply unit 11. This makes it difficult for the signal level of the power supply communication signal that is transmitted through the U-phase power line 51 and input to the load communication unit 23 to decrease, thereby improving communication quality. In addition, the inductor L12 functions as an impedance upper for the load communication signal that the coupler CP21 superimposes on the U-phase power line 51, making it difficult for the load communication signal that is superimposed on the U-phase power line 51 to propagate toward the power supply unit 11. This makes it difficult for the signal level of the load communication signal that is transmitted through the U-phase power line 51 and input to the power supply communication unit 13 to decrease, thereby improving communication quality. On the other hand, since the inductor L11 is present on the power supply unit 11 side, even if the output impedance of the power supply unit 11 (in other words, the impedance seen from the low-pass filter LP11 side of the power supply unit 11) is low, the low-pass filter LP11 can appropriately attenuate the harmonic components contained in the U-phase voltage output from the power supply unit 11.

[0080] In this example, the low-pass filter LP12 inserted in the V-phase power line 52 has inductors L13 and L14 on both ends thereof. The inductor L14 on the coupler CP12 side functions as an impedance upper for the power-supply communication signal that the coupler CP12 superimposes on the V-phase power line 52, making it difficult for the power-supply communication signal superimposed on the V-phase power line 52 to propagate toward the power supply unit 11. This makes it difficult for the signal level of the power-supply communication signal that is transmitted through the V-phase power line 52 and input to the load-side communication unit 23 to decrease, thereby improving communication quality. Inductor L14 also functions as an impedance upper for the load-side communication signal that the coupler CP22 superimposes on the V-phase power line 52, making it difficult for the load-side communication signal that is superimposed on the V-phase power line 52 to propagate toward the power supply unit 11. This makes it difficult for the signal level of the load-side communication signal that is transmitted through the V-phase power line 52 and input to the power-supply communication unit 13 to decrease, thereby improving communication quality. On the other hand, since the inductor L13 is present on the power supply unit 11 side, even if the output impedance of the power supply unit 11 is low, the low-pass filter LP12 can appropriately attenuate the harmonic components contained in the V-phase voltage output from the power supply unit 11.

[0081] <Example of load source side interface circuit configuration> The load-side interface circuit 24 has, for example, the same configuration as the power-supply-side interface circuit 14. The interface circuit 24 includes, for example, a low-pass filter unit LPG2 having a plurality of low-pass filters LP21, LP22, and LP23, and a coupler unit CPG2 having a plurality of couplers CP21 and CP22.

[0082] The low-pass filter unit LPG2 is inserted into the U-phase power line 51, the V-phase power line 52, and the W-phase power line 53. The low-pass filter unit LPG2 performs low-pass filtering on the U-phase voltage, the V-phase voltage, and the W-phase voltage transmitted to the load-side system 20 via the cable 60.

[0083] The coupler unit CPG2 is connected to the end of the low-pass filter unit LPG2 on the interface circuit 14 side. The coupler unit CPG2 superimposes the load-side differential signal transmitted by the communication unit 23 onto the U-phase power line 51 and the V-phase power line 52 on the interface circuit 24 side (in other words, the cable 60 side) of the low-pass filter unit LPG2. The coupler unit CPG2 also extracts the power-supply-side differential signal from the U-phase power line 51 and the V-phase power line 52 on which the power-supply-side differential signal is superimposed, and outputs the power-supply-side differential signal to the communication unit 23.

[0084] <Coupler section configuration example> The coupler unit CPG2 includes, for example, capacitors C25 and C26, an isolation transformer T21, and resistors R21 and R22. The isolation transformer T21 has a primary coil L27 and a secondary coil L28. The primary coil L27 is connected to the communication unit 23. One end of the resistor R21 is connected to one end of the primary coil L27. One end of the resistor R22 is connected to the other end of the primary coil L27. The other end of the resistor R21 is connected to the other end of the resistor R22. A bias voltage Vb2 is applied to the other end of the resistor R21 and the other end of the resistor R22. A bias voltage Vb2 is applied to one end of the primary coil L17 via a resistor R11. A bias voltage Vb2 is applied to the other end of the primary coil L17 via a resistor R12. Both ends of the secondary coil L28 are connected to one end of the capacitors C25 and C26, respectively. The other ends of the capacitors C25 and C26 are connected to the U-phase power line 51 and the V-phase power line 52, respectively.

[0085] The primary coil L27 receives a load side differential signal transmitted by the communication unit 23. One load side communication signal of the load side differential signals output from the secondary coil L28 is input to one end of the capacitor C25. The other load side communication signal of the load side differential signals output from the secondary coil L28 is input to one end of the capacitor C26.

[0086] When the power supply side differential signals are superimposed on the U-phase power line 51 and the V-phase power line 52, one of the power supply side communication signals superimposed on the U-phase power line 51 is input to the other end of capacitor C25, and the other power supply side communication signal superimposed on the V-phase power line 52 is input to the other end of capacitor C26.

[0087] Capacitor C25, isolation transformer T21, and resistor R21 constitute coupler CP21 that superimposes one load side communication signal transmitted by communication unit 23 onto U-phase power line 51. One load side communication signal of the load side differential signals output from secondary coil L28 is superimposed onto U-phase power line 51 via capacitor C25.

[0088] The coupler CP21 can extract one of the power supply side communication signals superimposed on the U-phase power line 51 of the power supply side differential signals. The one of the power supply side communication signals extracted from the U-phase power line 51 through the capacitor C25 is input to the communication unit 23 through the isolation transformer T21.

[0089] Capacitor C26, isolation transformer T21, and resistor R22 form coupler CP22 that superimposes the other load side communication signal transmitted by communication unit 23 onto V-phase power line 52. The other load side communication signal of the load side differential signals output from secondary coil L28 is superimposed onto V-phase power line 52 via capacitor C26.

[0090] Coupler CP22 can extract the other power supply side communication signal from V-phase power line 52 on which the other power supply side communication signal of the power supply side differential signal is superimposed. The other power supply side communication signal extracted from V-phase power line 52 through capacitor C26 is input to communication unit 23 through isolation transformer T21.

[0091] The coupler CP21 constitutes a high-pass filter HP21. The order of the high-pass filter HP21 is, for example, even. Specifically, the order of the high-pass filter HP21 is second. The high-pass filter HP21 performs high-pass filtering on one of the load-side communication signals transmitted by the communication unit 23. The one of the load-side communication signals that has been high-pass filtered by the high-pass filter HP21 is superimposed on the U-phase power line 51. The high-pass filter HP21 also performs high-pass filtering on one of the power-supply-side communication signals extracted from the U-phase power line 51. The one of the power-supply-side communication signals that has been high-pass filtered by the high-pass filter HP21 is received by the communication unit 23.

[0092] The coupler CP22 constitutes a high-pass filter HP22. The order of the high-pass filter HP22 is, for example, even. Specifically, the order of the high-pass filter HP22 is second. The high-pass filter HP22 performs high-pass filtering on the other load side communication signal transmitted by the communication unit 23. The other load side communication signal that has been high-pass filtered by the high-pass filter HP22 is superimposed on the V-phase power line 52. The high-pass filter HP22 also performs high-pass filtering on the other power supply side communication signal extracted from the V-phase power line 52. The other power supply side communication signal that has been high-pass filtered by the high-pass filter HP22 is received by the communication unit 23.

[0093] <Example of low-pass filter configuration> The low-pass filter unit LPG2 includes, for example, inductors L21, L22, L23, L24, L25, and L26, and capacitors C21, C22, and C23. The inductors L21 and L22 are connected in series to each other and inserted into the U-phase power line 51. One end of the inductor L21 is connected to the motor, and the other end of the inductor L21 is connected to one end of the inductor L22. The other end of the inductor L22 is connected to the other end of the capacitor C25 of the coupler CP21 and the cable 60. The U-phase voltage transmitted to the load-side system 20 via the U-phase power line 51 is input to the other end of the inductor L22.

[0094] Inductors L23 and L24 are connected in series to each other and inserted into the V-phase power line 52. One end of inductor L23 is connected to the motor, and the other end of inductor L23 is connected to one end of inductor L24. The other end of inductor L24 is connected to the other end of capacitor C26 of coupler CP22 and to cable 60. The V-phase voltage transmitted to the load-side system 20 via the V-phase power line 52 is input to the other end of inductor L24.

[0095] Inductors L25 and L26 are connected in series to each other and inserted into the W-phase power line 53. One end of inductor L25 is connected to the motor, and the other end of inductor L25 is connected to one end of inductor L26. The other end of inductor L26 is connected to cable 60. The W-phase voltage transmitted to the load-side system 20 by the W-phase power line 53 is input to the other end of inductor L26.

[0096] One end of capacitor C21 is connected to the other end of inductor L21 and one end of inductor L22. The other end of capacitor C21 is connected to the other end of inductor L23 and one end of inductor L24. One end of capacitor C22 is connected to the other end of inductor L23 and one end of inductor L24. The other end of capacitor C22 is connected to the other end of inductor L25 and one end of inductor L26. One end of capacitor C23 is connected to the other end of inductor L25 and one end of inductor L26. The other end of capacitor C23 is connected to the other end of inductor L21 and one end of inductor L22.

[0097] In the low-pass filter unit LPG2, inductors L21 and L22 and capacitors C21, C22, and C23 form a low-pass filter LP21 that performs low-pass filtering on the U-phase voltage transmitted through the U-phase power line 51. The U-phase voltage that has been low-pass filtered by the low-pass filter LP21 is supplied to the brushless motor. The U-phase voltage that has been low-pass filtered by the low-pass filter LP21 is not a sinusoidal voltage, but a square-wave voltage that includes a fundamental component and harmonic components (more specifically, harmonic components that are attenuated compared to before being low-pass filtered). The order of the low-pass filter LP21 is, for example, an odd order. Specifically, the order of the low-pass filter LP21 is third order.

[0098] In addition, in the low-pass filter unit LPG2, inductors L23 and L24 and capacitors C21, C22, and C23 form a low-pass filter LP22 that performs low-pass filtering on the V-phase voltage transmitted through the V-phase power line 52. The V-phase voltage that has been low-pass filtered by the low-pass filter LP22 is supplied to the brushless motor. The V-phase voltage that has been low-pass filtered by the low-pass filter LP22 is not a sinusoidal voltage, but a rectangular wave voltage that includes a fundamental wave component and harmonic components. The order of the low-pass filter LP22 is, for example, an odd order. Specifically, the order of the low-pass filter LP22 is third order.

[0099] In addition, in the low-pass filter unit LPG2, inductors L25 and L26 and capacitors C21, C22, and C23 form a low-pass filter LP23 that performs low-pass filtering on the W-phase voltage transmitted through the W-phase power line 53. The W-phase voltage that has been low-pass filtered by the low-pass filter LP23 is supplied to the motor. The W-phase voltage that has been low-pass filtered by the low-pass filter LP22 is not a sinusoidal voltage, but a rectangular wave voltage that includes a fundamental wave component and harmonic components. The order of the low-pass filter LP23 is, for example, an odd order. Specifically, the order of the low-pass filter LP23 is third order.

[0100] As described above, in interface circuit 24, low-pass filters LP21, LP22, and LP23 perform low-pass filtering on the U-phase voltage, V-phase voltage, and W-phase voltage, thereby attenuating harmonic components contained in the U-phase voltage, V-phase voltage, and W-phase voltage. This makes it difficult for high-frequency noise caused by the U-phase voltage, V-phase voltage, and W-phase voltage to be transmitted to load 21.

[0101] Furthermore, even if high frequency noise occurs in at least one of the load side communication unit 23 and the power supply side communication unit 13, the high frequency noise is less likely to be transmitted to the load 21 by the low pass filters LP21 and LP22.

[0102] Furthermore, even if high-frequency noise occurs in the load 21, the low-pass filters LP21 and LP22 make it difficult for the high-frequency noise to be transmitted to the load-side communication unit 23, thereby improving communication quality. Furthermore, even if high-frequency noise occurs in the load 21, the low-pass filters LP21, LP22, and LP23 make it difficult for the high-frequency noise to be transmitted to the power supply-side system 10. For example, the high-frequency noise becomes difficult to be transmitted to the power supply unit 11. Furthermore, the high-frequency noise becomes difficult to be transmitted to the power supply-side communication unit 13, thereby improving communication quality.

[0103] Furthermore, in this example, because couplers CP21 and CP22 of coupler unit CPG2 function as high-pass filters HP21 and HP22, even if low-frequency noise occurs in load-side communication unit 23, the low-frequency noise is less likely to be superimposed on U-phase power line 51 and V-phase power line 52. Therefore, low-frequency noise is less likely to be transmitted to load 21 and power supply-side system 10. Since low-frequency noise is less likely to be transmitted to power supply-side communication unit 13 of power supply-side system 10, communication quality can be improved. Furthermore, even if low-frequency noise occurs in at least one of load 21 and power supply-side system 10, the low-frequency noise is less likely to be transmitted to load-side communication unit 23, so communication quality can be improved.

[0104] In this example, the low-pass filter LP21 inserted in the U-phase power line 51 has inductors L21 and L22 on both ends thereof. The inductor L22 on the coupler CP21 side functions as an impedance upper for the load-side communication signal that the coupler CP21 superimposes on the U-phase power line 51, making it difficult for the load-side communication signal superimposed on the U-phase power line 51 to propagate toward the load 21. This makes it difficult for the signal level of the load-side communication signal that is input to the power-source communication unit 23 via the U-phase power line 51 to decrease, thereby improving communication quality. Inductor L22 also makes it difficult for the power-source communication signal superimposed on the U-phase power line 51 to propagate toward the load 21. This makes it difficult for the signal level of the power-source communication signal that is input to the load-source communication unit 23 via the U-phase power line 51 to decrease, thereby improving communication quality. On the other hand, since the inductor L21 is present on the load 21 side, even if the impedance of the load 21 as seen from the low-pass filter LP21 side is low, the low-pass filter LP21 can appropriately attenuate the high-frequency noise output from the load 21.

[0105] In this example, the low-pass filter LP22 inserted in the V-phase power line 52 has inductors L23 and L24 on both ends thereof. The inductor L24 on the coupler CP22 side functions as an impedance upper for the load-side communication signal that the coupler CP22 superimposes on the V-phase power line 52, making it difficult for the load-side communication signal superimposed on the V-phase power line 52 to propagate toward the load 21. This makes it difficult for the signal level of the load-side communication signal that is transmitted through the V-phase power line 52 and input to the power-source communication unit 13 to decrease, thereby improving communication quality. Inductor L24 also makes it difficult for the power-source communication signal superimposed on the V-phase power line 52 to propagate toward the load 21. This makes it difficult for the signal level of the power-source communication signal that is transmitted through the V-phase power line 52 and input to the load-source communication unit 23 to decrease, thereby improving communication quality. On the other hand, since the inductor L23 is present on the load 21 side, even if the impedance of the load 21 as seen from the low-pass filter LP22 side is low, the low-pass filter LP22 can appropriately attenuate the high-frequency noise output from the load 21.

[0106] <Example of gain frequency characteristics of low-pass and high-pass filters> FIG. 4 is a schematic diagram showing an example of the gain frequency characteristics of low-pass filters LP11, LP12, LP13, LP21, LP22, and LP23, and an example of the gain frequency characteristics of high-pass filters HP11, HP12, HP21, and HP22. The gain frequency characteristics are also called amplitude frequency characteristics. The gain frequency characteristics of low-pass filters LP11, LP12, LP13, LP21, LP22, and LP23 are, for example, the same as each other. The gain frequency characteristics of high-pass filters HP11, HP12, HP21, and HP22 are, for example, the same as each other. In FIG. 4, an example of the gain frequency characteristics of low-pass filters LP11, LP12, LP13, LP21, LP22, and LP23 is shown by a dashed dotted line, and an example of the gain frequency characteristics of high-pass filters HP11, HP12, HP21, and HP22 is shown by a solid line.

[0107] The cutoff frequency fc2 (also referred to as the HPF cutoff frequency fc2) of the high-pass filters HP11, HP12, HP21, and HP22 is set to be equal to or lower than the lower limit value fmin of the frequency band FB of the power supply side differential signal and the load side differential signal (in other words, the frequency band of the power supply side communication signal and the load side communication signal). In the example of Fig. 4, the HPF cutoff frequency fc2 is set to be lower than the lower limit value fmin of the frequency band FB (also referred to as the communication frequency band FB) of the power supply side differential signal and the load side differential signal.

[0108] The lower limit value fmin of the communication frequency band FB is set to be higher than the frequency (e.g., several kHz) of the fundamental wave components of the U-phase voltage, V-phase voltage, and W-phase voltage. The lower limit value fmin may be set to, for example, 1,000 times or more, 5,000 times or more, 10,000 times or more, or 50,000 times or more the frequency of the fundamental wave components (also simply referred to as fundamental wave components) of the U-phase voltage, V-phase voltage, and W-phase voltage. The communication frequency band FB is set to, for example, 50 MHz or more and 90 MHz or less. In this case, the HPF cutoff frequency fc2 is set to 50 MHz or less. The HPF cutoff frequency fc2 may be set to, for example, 45 MHz.

[0109] The cutoff frequency fc1 (also referred to as LPF cutoff frequency fc1) of the low-pass filters LP11, LP12, LP13, LP21, LP22, and LP23 is set to, for example, a frequency equal to or higher than the frequency of the fundamental wave component (for example, several kHz). Furthermore, the LPF cutoff frequency fc1 is set to, for example, a lower limit value fmin of the communication frequency band FB or lower. For example, the LPF cutoff frequency fc1 may be set to a value equal to or lower than the HPF cutoff frequency fc2. In the example of FIG. 4, the LPF cutoff frequency fc1 is set to be lower than the HPF cutoff frequency fc2. The LPF cutoff frequency fc1 may be set to, for example, 20 MHz.

[0110] The LPF cutoff frequency fc1 may be equal to or less than one-third, one-fourth, or one-fifth of the lower limit value fmin (for example, 50 MHz) of the communication frequency band FB.

[0111] Furthermore, the difference between the HPF cutoff frequency fc2 and the LPF cutoff frequency fc1 may be at least half, at least one-third, or at least one-fourth of the width of the communication frequency band FB (i.e., the frequency bandwidth of the power supply side differential signal and the load side differential signal). For example, if the HPF cutoff frequency fc2 is 45 MHz, the LPF cutoff frequency fc1 is 20 MHz, and the width of the communication frequency band FB is 40 MHz, the difference between the HPF cutoff frequency fc2 and the LPF cutoff frequency fc1 will be at least one-half of the width of the communication frequency band FB.

[0112] The difference between the HPF cutoff frequency fc2 and the LPF cutoff frequency fc1 may be two-thirds or more of the width of the communication frequency band FB, or may be three-quarters or more, or may be equal to or greater than the width of the communication frequency band FB. By increasing the difference between the HPF cutoff frequency fc2 and the LPF cutoff frequency fc1, it is possible to reduce noise input to the communication unit 13, the communication unit 23, the power supply unit 11, and the load 21.

[0113] In this way, when the LPF cutoff frequency fc1 is set to be equal to or lower than the lower limit value fmin of the communication frequency band FB, noise having a frequency within the communication frequency band FB, which is generated in at least one of the power supply unit 11 and the load 21, is less likely to be input to the communication unit 13 and the communication unit 23. Therefore, the communication quality can be improved.

[0114] Furthermore, when the LPF cutoff frequency fc1 is equal to or less than one-third of the lower limit value fmin of the communication frequency band FB, noise having a frequency within the communication frequency band FB that is generated in at least one of the power supply unit 11 and the load 21 is less likely to be input to the communication unit 13 and the communication unit 23, thereby further improving communication quality.

[0115] 4, when the LPF cutoff frequency fc1 is smaller than the HPF cutoff frequency fc2, which is equal to or smaller than the lower limit fmin of the communication frequency band FB, noise having a frequency within the communication frequency band FB, which is generated in at least one of the power supply unit 11 and the load 21, is less likely to be input to the communication units 13 and 23. This makes it possible to further improve the communication quality.

[0116] Furthermore, when the difference between the HPF cutoff frequency fc2 and the LPF cutoff frequency fc1 is equal to or greater than half the width of the communication frequency band FB, noise having a frequency within the communication frequency band FB, which is generated in at least one of the power supply unit 11 and the load 21, is less likely to be input to the communication units 13 and 23. This further improves the communication quality.

[0117] In this example, the orders (also referred to as LPF orders) of the low-pass filters LP11, LP12, LP13, LP21, LP22, and LP23 are set larger than the orders (also referred to as HPF orders) of the high-pass filters HP11, HP12, HP21, and HP22. By setting the LPF orders larger than the HPF orders, the attenuation slopes of the low-pass filters LP11, LP12, LP13, LP21, LP22, and LP23 become larger. Therefore, for example, even if the communication frequency band FB is lowered, communication quality can be maintained. Therefore, the communication frequency band FB can be lowered. Furthermore, by lowering the communication frequency band FB, the cable 60 can be lengthened, thereby increasing the communication distance between the power supply-side communication unit 13 and the load-side communication unit 23. Furthermore, by increasing the LPF orders, noise is reduced, thereby reducing radiation noise of the processing system 1A.

[0118] 5, the HPF cutoff frequency fc2 may be set to be greater than the lower limit value fmin of the communication frequency band FB. In this case, the absolute value df of the difference between the gain in the passband (i.e., 0 dB) and the gain at the lower limit value fmin of the communication frequency band FB in the gain-frequency characteristics of the high-pass filters HP11, HP12, HP21, and HP22 is set to a predetermined value or less, thereby improving the communication quality between the power supply-side communication unit 13 and the load-side communication unit 23. Alternatively, the absolute value of the difference between the gain at the HPF cutoff frequency fc2 (i.e., −3 dB) and the gain at the lower limit value fmin of the communication frequency band FB in the gain-frequency characteristics of the high-pass filters HP11, HP12, HP21, and HP22 is set to a predetermined value or less, thereby improving the communication quality. When the modulation method used in the power supply-side communication unit 13 and the load-side communication unit 23 is QPSK or FSK, the predetermined value may be set to, for example, 20 dB.

[0119] 6, the other ends of the capacitors C11, C12, and C13 may be connected to ground (for example, the ground of the power supply unit 11) or may be earthed. Also, the other ends of the capacitors C21, C22, and C23 may be connected to ground (for example, the ground of the load 21) or may be earthed.

[0120] In the above example, the LPF order was third, but it may be fifth or an odd number. If the LPF order is third or an odd number, inductors can be provided at both ends of each of the low-pass filters LP11, LP12, LP13, LP21, LP22, and LP23. The LPF order may also be even.

[0121] In the above example, the HPF order was second, but it may be third or higher odd order, or fourth or higher even order. The HPF order may be the same as or greater than the LPF order.

[0122] In the above example, the low-pass filters LP11, LP12, LP13, LP21, LP22, and LP23 have the same gain-frequency characteristics, but the gain-frequency characteristics of at least two of the low-pass filters LP11, LP12, LP13, LP21, LP22, and LP23 may be different from each other.Furthermore, the cutoff frequencies of at least two of the low-pass filters LP11, LP12, LP13, LP21, LP22, and LP23 may be different from each other.

[0123] Furthermore, in the above example, the orders of the low-pass filters LP11, LP12, LP13, LP21, LP22, and LP23 are the same, but the orders of at least two of the low-pass filters LP11, LP12, LP13, LP21, LP22, and LP23 may be different from each other.

[0124] In the above example, the high-pass filters HP11, HP12, HP21, and HP22 have the same gain frequency characteristics, but the gain frequency characteristics of at least two of the high-pass filters HP11, HP12, HP21, and HP22 may be different from each other. Also, the cutoff frequencies of at least two of the high-pass filters HP11, HP12, HP21, and HP22 may be different from each other.

[0125] In the above example, the orders of the high-pass filters HP11, HP12, HP21, and HP22 are the same, but the orders of at least two of the high-pass filters HP11, HP12, HP21, and HP22 may be different from each other.

[0126] The constant of inductor L12 of power supply side interface circuit 14 and the constant of inductor L22 of load side interface circuit 24 may be different from each other. For example, the constant of inductor L12 may be set larger than the constant of inductor L22. In this case, high-frequency noise caused by the U-phase voltage output by power supply unit 11 can be made less likely to be transmitted to load side system 20. On the other hand, when the constant of inductor L22 is set larger than the constant of inductor L12, high-frequency noise generated in load 21 can be made less likely to be transmitted to power supply side system 10 through U-phase power line 51.

[0127] Similarly, the constant of the inductor L14 of the power supply side interface circuit 14 may be different from the constant of the inductor L24 of the load side interface circuit 24. Furthermore, the constant of the inductor L16 of the power supply side interface circuit 14 may be different from the constant of the inductor L26 of the load side interface circuit 24.

[0128] The load side interface circuit 24 may not be provided with the low-pass filter unit LPG2, and the power supply side interface circuit 14 may not be provided with the low-pass filter unit LPG1.

[0129] The power supply side communication unit 13 and the load side communication unit 23 may perform single-ended communication. In this case, a single-ended communication signal (also referred to as a power supply side single-ended signal) output by the power supply side communication unit 13 is superimposed on one of the U-phase power line 51, the V-phase power line 52, and the W-phase power line 53. Furthermore, a single-ended communication signal (also referred to as a load side single-ended signal) output by the load side communication unit 23 is superimposed on one of the U-phase power line 51, the V-phase power line 52, and the W-phase power line 53.

[0130] When the power supply side single-ended communication signal is superimposed on, for example, the U-phase power line 51, the capacitor C16 is not required in the coupler unit CPG1, and one end of the primary side coil L17 and one end of the secondary side coil L18 are connected to ground. Also, when the load side single-ended signal is superimposed on, for example, the U-phase power line 51, the capacitor C26 is not required in the coupler unit CPG2, and one end of the primary side coil L27 and one end of the secondary side coil L28 are connected to ground.

[0131] The coupler unit CPG1 may not include the isolation transformer T11. In this case, one end of the capacitor C15 is connected to the power supply side communication unit 13 and one end of the resistor R11, and one end of the capacitor C16 is connected to the power supply side communication unit 13 and one end of the resistor R12. Furthermore, the coupler unit CPG2 may not include the isolation transformer T21. In this case, one end of the capacitor C25 is connected to the load side communication unit 23 and one end of the resistor R21, and one end of the capacitor C26 is connected to the load side communication unit 23 and one end of the resistor R22.

[0132] <Other examples of processing systems> 7 is a schematic diagram showing an example of the processing system 1 when the load 21 is a brushed DC motor. Hereinafter, the term "brushed DC motor" or "brushed motor" refers to the brushed DC motor as the load 21.

[0133] In the processing system 1 (also referred to as processing system 1B) shown in FIG. 7, a power supply unit 11 outputs a power supply voltage to a brushed DC motor. The brushed DC motor is, for example, PWM controlled. The brushed DC motor can rotate in both directions by the power supply voltage supplied from the power supply unit 11. Hereinafter, the two directions in which the brushed DC motor can rotate are referred to as the first direction and the second direction.

[0134] The power line 50 transmits the power supply voltage output from the power supply unit 11 to the brushed DC motor. The power line 50 is composed of a first power line 55a and a second power line 55b. The first power line 55a extends from the power supply unit 11 to one electrode (also referred to as one brush) of the brushed DC motor. The second power line 55b extends from the power supply unit 11 to the other electrode (also referred to as the other brush) of the brushed DC motor.

[0135] The power supply unit 11 includes, for example, an H-bridge circuit (also called a half-bridge circuit). The H-bridge circuit is capable of outputting a square-wave power supply voltage to each of a first power line 55a and a second power line 55b. When the brushed motor is rotated in a first direction, the H-bridge circuit outputs a square-wave first power supply voltage to the first power line 55a and connects the second power line 55b to the ground of the power supply unit 11. On the other hand, when the brushed motor is rotated in a second direction, the H-bridge circuit outputs a square-wave second power supply voltage to the second power line 55b and connects the first power line 55a to the ground of the power supply unit 11. The maximum values ​​of the first power supply voltage and the second power supply voltage are, for example, several hundred volts.

[0136] The first power line 55a transmits the first power supply voltage output by the power supply unit 11 to one electrode of the brushed motor. When the square-wave first power supply voltage is supplied to one electrode of the brushed DC motor, the other electrode of the brushed motor, connected to the second power line 55b, is connected to ground. The second power line 55b transmits the second power supply voltage output by the power supply unit 11 to the other electrode of the brushed motor. When the square-wave second power supply voltage is supplied to the other electrode of the brushed DC motor, the one electrode of the brushed motor, connected to the first power line 55a, is connected to ground.

[0137] The power supply side interface circuit 14 included in the processing system 1B includes, for example, a low-pass filter unit LPG3 having low-pass filters LP31 and LP32, and the above-mentioned coupler unit CPG1. The load side interface circuit 24 included in the processing system 1B includes, for example, a low-pass filter unit LPG4 having low-pass filters LP41 and LP42, and the above-mentioned coupler unit CPG2.

[0138] The other ends of the capacitors C15 and C16 of the coupler section CPG1 are connected to the first power line 55a and the second power line 55b, respectively. The coupler section CPG1 superimposes the power supply side differential signals output by the power supply side communication section 13 onto the first power line 55a and the second power line 55b. One power supply side communication signal of the power supply side differential signals output from the secondary side coil L18 is superimposed on the first power line 55a through the capacitor C15 of the coupler CP11. Furthermore, the other power supply side communication signal of the power supply side differential signals output from the secondary side coil L18 is superimposed on the second power line 55b through the capacitor C16 of the coupler CP12.

[0139] The other ends of the capacitors C25 and C26 of the coupler section CPG2 are connected to the first power line 55a and the second power line 55b, respectively. The coupler section CPG2 superimposes the load side differential signals output by the load side communication section 23 onto the first power line 55a and the second power line 55b. One load side communication signal of the load side differential signals output from the secondary side coil L28 is superimposed on the first power line 55a through the capacitor C25 of the coupler CP21. Furthermore, the other load side communication signal of the load side differential signals output from the secondary side coil L28 is superimposed on the second power line 55b through the capacitor C26 of the coupler CP22.

[0140] The coupler section CPG1 extracts the load side differential signals from the first power line 55a and the second power line 55b on which the load side differential signals are superimposed, and outputs them to the power supply side communication section 13. One of the load side communication signals superimposed on the first power line 55a is input to the other end of the capacitor C15 of the coupler CP11, and the other load side communication signal superimposed on the second power line 55b is input to the other end of the capacitor C16 of the coupler CP12.

[0141] The coupler section CPG2 extracts the power supply side differential signals from the first power line 55a and the second power line 55b on which the power supply side differential signals are superimposed, and outputs them to the load side communication section 23. One of the power supply side communication signals superimposed on the first power line 55a is input to the other end of the capacitor C25 of the coupler CP21, and the other power supply side communication signal superimposed on the second power line 55b is input to the other end of the capacitor C26 of the coupler CP22.

[0142] One power supply side communication signal that has been high-pass filtered by the high-pass filter HP11 configured by the coupler CP11 is superimposed on the first power line 55a. The high-pass filter HP11 also performs high-pass filtering on one load side communication signal extracted from the first power line 55a and outputs the signal to the power supply side communication unit 13.

[0143] The other power supply side communication signal that has been high-pass filtered by the high-pass filter HP12 configured by the coupler CP12 is superimposed on the second power line 55b. The high-pass filter HP12 also performs high-pass filtering on the other load side communication signal extracted from the second power line 55b and outputs the result to the power supply side communication unit 13.

[0144] The load-side communication signal is subjected to high-pass filtering by the high-pass filter HP21 included in the coupler CP21 and is superimposed on the first power line 55a. The high-pass filter HP21 also performs high-pass filtering on the power-supply-side communication signal extracted from the first power line 55a and outputs the signal to the load-side communication unit 23.

[0145] The other load-side communication signal that has been high-pass filtered by the high-pass filter HP22 configured by the coupler CP22 is superimposed on the second power line 55b. The high-pass filter HP22 also performs high-pass filtering on the other power supply-side communication signal extracted from the second power line 55b and outputs the result to the load-side communication unit 23.

[0146] The low-pass filter unit LPG3 includes, for example, inductors L31, L32, L33, and L34 and a capacitor C31. The inductors L31 and L32 are connected in series to each other and inserted into the first power line 55a. One end of the inductor L31 is connected to the power supply unit 11, and the other end of the inductor L31 is connected to one end of the inductor L32. The other end of the inductor L32 is connected to the other end of the capacitor C15 of the coupler CP11 and the cable 60. The first power supply voltage output by the power supply unit 11 is input to one end of the inductor L31.

[0147] Inductors L33 and L34 are connected in series to each other and inserted into the second power line 55b. One end of the inductor L33 is connected to the power supply unit 11, and the other end of the inductor L33 is connected to one end of the inductor L34. The other end of the inductor L34 is connected to the other end of the capacitor C16 of the coupler CP12 and to the cable 60. The second power supply voltage output by the power supply unit 11 is input to one end of the inductor L33.

[0148] One end of the capacitor C31 is connected to the other end of the inductor L31 and one end of the inductor L32, and the other end of the capacitor C31 is connected to the other end of the inductor L33 and one end of the inductor L34.

[0149] In the low-pass filter unit LPG3, inductors L31 and L32 and a capacitor C31 form a low-pass filter LP31 that performs low-pass filtering on the first power supply voltage transmitted through the first power line 55a. The first power supply voltage that has been low-pass filtered by the low-pass filter LP31 is transmitted to the load-side system 20 via a cable 60. The order of the low-pass filter LP31 is, for example, third order.

[0150] In the low-pass filter unit LPG3, inductors L33 and L34 and capacitor C31 form a low-pass filter LP32 that performs low-pass filtering on the second power supply voltage transmitted through the second power line 55b. The second power supply voltage that has been low-pass filtered by the low-pass filter LP32 is transmitted to the load-side system 20 through a cable 60. The order of the low-pass filter LP32 is, for example, third order.

[0151] The low-pass filter unit LPG4 includes, for example, inductors L41, L42, L43, and L44 and a capacitor C41. The inductors L41 and L42 are connected in series to each other and inserted into the first power line 55a. One end of the inductor L41 is connected to one electrode of the brushed motor, and the other end of the inductor L41 is connected to one end of the inductor L42. The other end of the inductor L42 is connected to the other end of the capacitor C25 of the coupler CP21 and to the cable 60. The first power supply voltage transmitted to the load-side system 20 via the cable 60 is input to the other end of the inductor L42.

[0152] Inductors L43 and L44 are connected in series to each other and inserted into the second power line 55b. One end of the inductor L43 is connected to the other electrode of the brushed motor, and the other end of the inductor L43 is connected to one end of the inductor L44. The other end of the inductor L44 is connected to the other end of the capacitor C26 of the coupler CP22 and to the cable 60. The second power supply voltage transmitted to the load-side system 20 via the cable 60 is input to the other end of the inductor L44.

[0153] One end of the capacitor C41 is connected to the other end of the inductor L41 and one end of the inductor L42, and the other end of the capacitor C41 is connected to the other end of the inductor L43 and one end of the inductor L44.

[0154] In the low-pass filter unit LPG4, inductors L41 and L42 and a capacitor C41 form a low-pass filter LP41 that performs low-pass filtering on the first power supply voltage transmitted through the first power line 55a. The first power supply voltage that has been low-pass filtered by the low-pass filter LP41 is supplied to one electrode of the brushed motor. The order of the low-pass filter LP41 is, for example, third order.

[0155] In the low-pass filter unit LPG4, inductors L43 and L44 and a capacitor C41 form a low-pass filter LP42 that performs low-pass filtering on the second power supply voltage transmitted through the second power line 55b. The second power supply voltage that has been low-pass filtered by the low-pass filter LP42 is supplied to the other electrode of the brushed motor. The order of the low-pass filter LP42 is, for example, third order.

[0156] As described above, in the power supply side interface circuit 14 of the processing system 1B, the low-pass filters LP31 and LP32 perform low-pass filtering on the square-wave first power supply voltage and second power supply voltage, thereby attenuating the harmonic components contained in the first power supply voltage and second power supply voltage. Therefore, high-frequency noise caused by the first power supply voltage and second power supply voltage is less likely to be transmitted to the power supply side communication unit 13 and the load side system 20.

[0157] Furthermore, even if high frequency noise occurs in at least one of the power supply side communication unit 13 and the load side system 20, the high frequency noise is less likely to be transmitted to the power supply unit 11 by the low pass filter unit LPG3.

[0158] Furthermore, in this example, since the couplers CP11 and CP12 function as high-pass filters HP11 and HP12, even if low-frequency noise occurs in the power supply side communication unit 13, the low-frequency noise is less likely to be superimposed on the first power line 55a and the second power line 55b. Therefore, the low-frequency noise is less likely to be transmitted to the power supply unit 11 and the load side system 20. Furthermore, even if low-frequency noise occurs in at least one of the power supply unit 11 and the load side system 20, the low-frequency noise is less likely to be transmitted to the power supply side communication unit 13.

[0159] In this example, the low-pass filter LP31 inserted in the first power line 55a has inductors L31 and L32 on both ends thereof. The inductor L32 on the coupler CP11 side functions as an impedance upper for the power-supply-side communication signal that the coupler CP11 superimposes on the first power line 55a, making it difficult for the power-supply-side communication signal superimposed on the first power line 55a to propagate toward the power supply unit 11. This makes it difficult for the signal level of the power-supply-side communication signal that is input to the load-side communication unit 23 via the first power line 55a to decrease. In addition, the inductor L32 functions as an impedance upper for the load-side communication signal that the coupler CP21 superimposes on the first power line 55a, making it difficult for the load-side communication signal that is superimposed on the first power line 55a to propagate toward the power supply unit 11. This makes it difficult for the signal level of the load-side communication signal that is input to the power-supply-side communication unit 13 via the first power line 55a to decrease. On the other hand, since the inductor L31 is present on the side of the power supply unit 11, even if the output impedance of the power supply unit 11 is low, the low-pass filter LP31 can appropriately attenuate harmonic components contained in the first power supply voltage output from the power supply unit 11. The same can be said for the low-pass filter LP32 inserted in the second power line 55b.

[0160] Furthermore, in the load-side interface circuit 24, the low-pass filters LP41 and L42 perform low-pass filtering on the rectangular waves of the first power supply voltage and the second power supply voltage, thereby attenuating harmonic components contained in the first power supply voltage and the second power supply voltage, thereby making it difficult for high-frequency noise caused by the first power supply voltage and the second power supply voltage to be transmitted to the load 21.

[0161] Furthermore, even if high frequency noise occurs in at least one of the load side communication unit 23 and the power supply side communication unit 13, the low pass filters LP41 and LP42 make it difficult for the high frequency noise to be transmitted to the load 21.

[0162] Furthermore, even if high-frequency noise occurs in the load 21, the low-pass filter unit LPG4 makes it difficult for the high-frequency noise to be transmitted to the load-side communication unit 23 and the power supply-side system 10.

[0163] Furthermore, in this example, since the couplers CP21 and CP22 function as high-pass filters HP21 and HP22, even if low-frequency noise occurs in the load-side communication unit 23, the low-frequency noise is less likely to be superimposed on the first power line 55a and the second power line 55b. Therefore, the low-frequency noise is less likely to be transmitted to the load 21 and the power supply side system 10. Furthermore, even if low-frequency noise occurs in at least one of the load 21 and the power supply side system 10, the low-frequency noise is less likely to be transmitted to the load-side communication unit 23.

[0164] In this example, the low-pass filter LP41 inserted in the first power line 55a has inductors L41 and L42 on both ends thereof. The inductor L42 on the coupler CP21 side functions as an impedance upper for the load-side communication signal that the coupler CP21 superimposes on the first power line 55a, making it difficult for the load-side communication signal superimposed on the first power line 55a to propagate toward the load 21. This makes it difficult for the signal level of the load-side communication signal that is transmitted through the first power line 55a and input to the power-source-side communication unit 13 to decrease. In addition, the inductor L42 functions as an impedance upper for the power-source-side communication signal that the coupler CP11 superimposes on the first power line 55a, making it difficult for the power-source-side communication signal that is superimposed on the first power line 55a to propagate toward the load 21. This makes it difficult for the signal level of the power-source-side communication signal that is transmitted through the first power line 55a and input to the load-side communication unit 23 to decrease. On the other hand, because the inductor L41 is present on the load 21 side, even if the impedance seen from the low-pass filter LP41 side of the load 21 is low, the low-pass filter LP41 can appropriately attenuate high-frequency noise output from the load 21. The same can be said for the low-pass filter LP42 inserted in the second power line 55b.

[0165] The low-pass filters LP31, LP32, LP41, and LP42 may have the same gain frequency characteristics, and the low-pass filters LP31, LP32, LP41, and LP42 may have the same cutoff frequencies.

[0166] In the processing system 1B, the lower limit value fmin of the communication frequency band FB is set to be higher than the frequency (e.g., several kHz) of the fundamental wave components included in the first power supply voltage and the second power supply voltage, which are square waves. The lower limit value fmin may be set to, for example, 1000 times or more, 5000 times or more, 10000 times or more, or 50000 times or more the frequency of the fundamental wave components included in the first power supply voltage and the second power supply voltage.

[0167] The cutoff frequencies of the low-pass filters LP31, LP32, LP41, and LP42 (also referred to as second LPF cutoff frequencies) are set to be equal to or higher than the frequencies of the fundamental components included in the first and second power supply voltages. The relationship between the second LPF cutoff frequency and the lower limit value fmin of the communication frequency band FB may be the same as the relationship between the LPF cutoff frequency fc1 and the lower limit value fmin of the communication frequency band FB described above. The relationship between the second LPF cutoff frequency and the HPF cutoff frequency fc2 (i.e., the cutoff frequencies of the high-pass filters HP11, HP12, HP21, and HP22) may be the same as the relationship between the LPF cutoff frequency fc1 and the HPF cutoff frequency fc2 described above. The relationship between the HPF cutoff frequency fc2 and the lower limit value fmin of the communication frequency band FB in the processing system 1B may be the same as the relationship between the HPF cutoff frequency fc2 and the lower limit value fmin of the communication frequency band FB in the processing system 1A (e.g., FIG. 4 or 5).

[0168] The other end of capacitor C31 may be connected to ground or may be earthed. In this case, an additional capacitor may be provided connected to the connection point between inductors L33 and L34. One end of the additional capacitor is connected to the connection point between inductors L33 and L34, and the other end of the additional capacitor may be connected to ground or may be earthed.

[0169] Similarly, the other end of capacitor C41 may be connected to ground or may be connected to earth. In this case, an additional capacitor may be provided connected to the connection point of inductor L43 and inductor L44. One end of the additional capacitor is connected to the connection point of inductor L43 and inductor L44, and the other end of the additional capacitor may be connected to ground or may be connected to earth.

[0170] The orders of the low-pass filters LP31, LP32, LP41, and LP42 may be odd orders (fifth or greater), or may be even orders. At least two of the low-pass filters LP31, LP32, LP41, and LP42 may have different gain-frequency characteristics. At least two of the low-pass filters LP31, LP32, LP41, and LP42 may have different cutoff frequencies. At least two of the low-pass filters LP31, LP32, LP41, and LP42 may have different orders.

[0171] The constant of inductor L32 of the power supply side interface circuit 14 and the constant of inductor L42 of the load side interface circuit 24 may be different from each other. The constant of inductor L32 may be set larger than the constant of inductor L42, or the constant of inductor L42 may be set larger than the constant of inductor L32. Similarly, the constant of inductor L34 of the power supply side interface circuit 14 and the constant of inductor L44 of the load side interface circuit 24 may be different from each other.

[0172] The load side interface circuit 24 does not necessarily have to be provided with the low-pass filter unit LPG4, and the power supply side interface circuit 14 does not necessarily have to be provided with the low-pass filter unit LPG3.

[0173] The power supply side communication unit 13 and the load side communication unit 23 may perform single-ended communication. In this case, the power supply side single-ended signal output by the power supply side communication unit 13 is superimposed on either the first power line 55a or the second power line 55b. Furthermore, the load side single-ended signal output by the load side communication unit 23 is superimposed on either the first power line 55a or the second power line 55b. When the power supply side single-ended signal is superimposed on, for example, the first power line 55a, the capacitor C16 is not required in the coupler unit CPG1, and one ends of the primary side coil L17 and the secondary side coil L18 are connected to ground. Furthermore, when the load side single-ended signal is superimposed on, for example, the first power line 55a, the capacitor C26 is not required in the coupler unit CPG2, and one ends of the primary side coil L27 and the secondary side coil L28 are connected to ground.

[0174] In the processing system 1B, the coupler unit CPG1 may not include the isolation transformer T11. In this case, one end of the capacitor C15 is connected to the power supply side communication unit 13 and one end of the resistor R11, and one end of the capacitor C16 is connected to the power supply side communication unit 13 and one end of the resistor R12. In addition, the coupler unit CPG2 may not include the isolation transformer T21. In this case, one end of the capacitor C25 is connected to the load side communication unit 23 and one end of the resistor R21, and one end of the capacitor C26 is connected to the load side communication unit 23 and one end of the resistor R22.

[0175] 8 is a schematic diagram showing another example of the processing system 1 when the load 21 is a brushed DC motor. In the processing system 1 shown in FIG. 8 (also referred to as processing system 1C), the power line 50 is composed of a single power line 56.

[0176] 8 (also referred to as processing system 1C), a power line 56 transmits a power supply voltage output from a power supply unit 11 to a brushed DC motor. The power line 56 extends from the power supply unit 11 to one electrode of the brushed DC motor. The other electrode of the brushed DC motor is connected to ground.

[0177] In the processing system 1C, the brushed DC motor serving as the load 21 is also controlled, for example, by PWM. The power supply unit 11 includes, for example, a T-bridge circuit. The T-bridge circuit is capable of outputting a square-wave power supply voltage to the power line 56. When rotating the brushed motor in a first direction, the T-bridge circuit outputs a square-wave positive power supply voltage to the power line 56. The power line 56 transmits the positive power supply voltage output by the power supply unit 11 to one electrode of the brushed motor. On the other hand, when rotating the brushed motor in a second direction, the H-bridge circuit outputs a square-wave negative power supply voltage to the power line 56. The power line 56 transmits the negative power supply voltage output by the power supply unit 11 to one electrode of the brushed motor. The absolute values ​​of the maximum positive and negative power supply voltages are, for example, several hundred volts.

[0178] The power supply side interface circuit 14 included in the processing system 1C includes, for example, a low-pass filter LP51 and a coupler CP51. The load side interface circuit 24 included in the processing system 1C includes, for example, a low-pass filter LP61 and a coupler CP61.

[0179] In the processing system 1C, the power supply side communication unit 13 and the load side communication unit 23 perform, for example, single-ended communication. The coupler CP51 superimposes the power supply side single-ended signal transmitted by the communication unit 13 onto the power line 56. The coupler CP61 superimposes the load side single-ended signal transmitted by the communication unit 23 onto the power line 56.

[0180] The coupler CP51 is composed of, for example, a capacitor C53 and a resistor R51. One end of the capacitor C53 is connected to the communication unit 13 and one end of the resistor R51. A bias voltage Vb51 is applied to the other end of the resistor R51. The bias voltage Vb51 is applied to one end of the capacitor C53 via the resistor R51. The other end of the capacitor C53 is connected to the power line 56. The power supply side single-ended signal transmitted by the communication unit 13 is superimposed on the power line 56 via the capacitor C53.

[0181] The coupler CP61 is composed of, for example, a capacitor C63 and a resistor R61. One end of the capacitor C63 is connected to the communication unit 23 and one end of the resistor R61. A bias voltage Vb61 is applied to the other end of the resistor R61. The bias voltage Vb61 is applied to one end of the capacitor C63 via the resistor R61. The other end of the capacitor C63 is connected to the power line 56. The load-side single-ended signal transmitted by the communication unit 23 is superimposed on the power line 56 via the capacitor C63.

[0182] Coupler CP51 extracts the load side single-ended signal from power line 56 on which the load side single-ended signal is superimposed, and outputs it to communication unit 13. The load side single-ended signal superimposed on power line 56 is input to the other end of capacitor C53 of coupler CP51. The load side single-ended signal output from one end of capacitor C53 is input to communication unit 13.

[0183] Coupler CP61 extracts the power supply side single-ended signal from power line 56 on which the power supply side single-ended signal is superimposed, and outputs the power supply side single-ended signal to communication unit 23. The power supply side single-ended signal superimposed on power line 56 is input to the other end of capacitor C63 of coupler CP61. The power supply side single-ended signal output from one end of capacitor C63 is input to communication unit 23.

[0184] The coupler CP51 constitutes a high-pass filter HP51. That is, the capacitor C53 and the resistor R51 constitute the high-pass filter HP51. The high-pass filter HP51 performs high-pass filtering on the power supply side single-ended signal transmitted by the communication unit 13. The power supply side single-ended signal that has been high-pass filtered by the high-pass filter HP51 is superimposed on the power line 56. The high-pass filter HP51 also performs high-pass filtering on the load side single-ended signal extracted from the power line 56. The load side single-ended signal that has been high-pass filtered by the high-pass filter HP51 is received by the communication unit 13.

[0185] The coupler CP61 constitutes a high-pass filter HP61. The high-pass filter HP61 performs high-pass filtering on the load-side single-ended signal transmitted by the communication unit 23. The load-side single-ended signal that has been high-pass filtered by the high-pass filter HP61 is superimposed on the power line 56. The high-pass filter HP61 also performs high-pass filtering on the power-supply-side single-ended signal extracted from the power line 56. The power-supply-side single-ended signal that has been high-pass filtered by the high-pass filter HP61 is received by the communication unit 23.

[0186] The orders of the high-pass filters HP51 and HP61 are, for example, odd orders. Specifically, the orders of the high-pass filters HP51 and HP61 are first orders. The gain frequency characteristics of the high-pass filters HP51 and HP61 may be the same. Furthermore, the cutoff frequencies of the high-pass filters HP51 and HP61 may be the same.

[0187] The low-pass filter LP51 performs low-pass filtering on the power supply voltage (more specifically, the positive power supply voltage and the negative power supply voltage output by the power supply unit 11) transmitted through the power line 56. The power supply voltage that has been low-pass filtered by the low-pass filter LP51 is transmitted to the load-side system 20 through a cable 60. The order of the low-pass filter LP51 is, for example, third order.

[0188] The low-pass filter LP51 includes, for example, inductors L51 and L52 and a capacitor C51. The inductors L51 and L52 are connected in series to each other and inserted into the power line 56. One end of the inductor L51 is connected to the power supply unit 11, and the other end of the inductor L51 is connected to one end of the inductor L52. The other end of the inductor L52 is connected to the other end of the capacitor C53 of the coupler CP51 and to the cable 60. One end of the capacitor C51 is connected to the other end of the inductor L51 and one end of the inductor L52. The other end of the capacitor C51 is connected to the ground. The power supply voltage output by the power supply unit 11 is input to one end of the inductor L51.

[0189] The low-pass filter LP61 performs low-pass filtering on the power supply voltage transmitted through the power line 56 (more specifically, the positive and negative power supply voltages transmitted to the load-side system 20 via the cable 60). The power supply voltage that has been low-pass filtered by the low-pass filter LP61 is supplied to one electrode of the brushed motor. The order of the low-pass filter LP61 is, for example, third order.

[0190] The low-pass filter LP61 includes, for example, inductors L61 and L62 and a capacitor C61. The inductors L61 and L62 are connected in series and inserted into the power line 56. One end of the inductor L61 is connected to one electrode of the brushed motor, and the other end of the inductor L61 is connected to one end of the inductor L62. The other end of the inductor L62 is connected to the other end of the capacitor C63 of the coupler CP61 and the cable 60. One end of the capacitor C61 is connected to the other end of the inductor L61 and one end of the inductor L62. The other end of the capacitor C61 is connected to the ground. The power supply voltage transmitted to the load-side system 20 via the cable 60 is input to the other end of the inductor L62.

[0191] As described above, in the power supply side interface circuit 14 of the processing system 1C, the low-pass filter LP51 performs low-pass filtering on the square-wave power supply voltage, thereby attenuating the harmonic components contained in the power supply voltage. As a result, high-frequency noise caused by the power supply voltage is less likely to be transmitted to the power supply side communication unit 13 and the load side system 20.

[0192] Furthermore, even if high frequency noise occurs in at least one of the power supply side communication unit 13 and the load side system 20, the low pass filter LP51 makes it difficult for the high frequency noise to be transmitted to the power supply unit 11.

[0193] Furthermore, in this example, since the coupler CP51 functions as a high-pass filter HP51, even if low-frequency noise occurs in the power supply side communication unit 13, the low-frequency noise is less likely to be superimposed on the power line 56. Therefore, the low-frequency noise is less likely to be transmitted to the power supply unit 11 and the load side system 20. Furthermore, even if low-frequency noise occurs in at least one of the power supply unit 11 and the load side system 20, the low-frequency noise is less likely to be transmitted to the power supply side communication unit 13.

[0194] In this example, the low-pass filter LP51 inserted in the power line 56 has inductors L51 and L52 on both ends thereof. The inductor L52 on the coupler CP51 side functions as an impedance upper for the power supply side single-ended signal that the coupler CP51 superimposes on the power line 56, making it difficult for the power supply side single-ended signal superimposed on the power line 56 to propagate toward the power supply unit 11. This makes it difficult for the signal level of the power supply side single-ended signal that is input to the load side communication unit 23 via the power line 56 to decrease. In addition, the inductor L52 functions as an impedance upper for the load side single-ended signal that the coupler CP51 superimposes on the power line 56, making it difficult for the load side single-ended signal that is superimposed on the power line 56 to propagate toward the power supply unit 11. This makes it difficult for the signal level of the load side single-ended signal that is input to the power supply side communication unit 13 via the power line 56 to decrease. On the other hand, since the inductor L51 is present on the power supply unit 11 side, even if the output impedance of the power supply unit 11 is low, the low-pass filter LP51 can appropriately attenuate the harmonic components contained in the power supply voltage output from the power supply unit 11.

[0195] Furthermore, in the load-side interface circuit 24, the low-pass filter LP61 performs low-pass filtering on the rectangular wave power supply voltage, thereby attenuating the harmonic components contained in the power supply voltage. As a result, high-frequency noise caused by the power supply voltage is less likely to be transmitted to the load 21.

[0196] Furthermore, even if high frequency noise occurs in at least one of the load side communication unit 23 and the power supply side communication unit 13, the low pass filter LP61 makes it difficult for the high frequency noise to be transmitted to the load 21.

[0197] Furthermore, even if high-frequency noise occurs in the load 21, the low-pass filter LP61 makes it difficult for the high-frequency noise to be transmitted to the load-side communication unit 23 and the power supply-side system 10.

[0198] Furthermore, in this example, since the coupler CP61 functions as a high-pass filter HP61, even if low-frequency noise occurs in the load-side communication unit 23, the low-frequency noise is less likely to be superimposed on the power line 56. Therefore, the low-frequency noise is less likely to be transmitted to the load 21 and the power supply-side system 10. Furthermore, even if low-frequency noise occurs in at least one of the load 21 and the power supply-side system 10, the low-frequency noise is less likely to be transmitted to the load-side communication unit 23.

[0199] In this example, the low-pass filter LP61 inserted in the power line 56 has inductors L61 and L62 on both ends thereof. The inductor L62 on the coupler CP61 side functions as an impedance upper for the load-side single-ended signal that the coupler CP61 superimposes on the power line 56, making it difficult for the load-side single-ended signal superimposed on the power line 56 to propagate toward the load 21. This makes it difficult for the signal level of the load-side single-ended signal that is input to the power supply-side communication unit 13 via the power line 56 to decrease. In addition, the inductor L62 functions as an impedance upper for the power supply-side single-ended signal that the coupler CP61 superimposes on the power line 56, making it difficult for the power supply-side single-ended signal that is superimposed on the power line 56 to propagate toward the load 21. This makes it difficult for the signal level of the power supply-side single-ended signal that is input to the load-side communication unit 23 via the power line 56 to decrease. On the other hand, since the inductor L61 is present on the load 21 side, even if the impedance seen from the low-pass filter LP61 side of the load 21 is low, the low-pass filter LP61 can appropriately attenuate the high-frequency noise output from the load 21.

[0200] The low-pass filters LP51 and LP61 may have the same gain frequency characteristics, and the low-pass filters LP51 and LP61 may have the same cutoff frequencies.

[0201] In the processing system 1C, the lower limit of the frequency band (also referred to as the second communication frequency band) of the power supply side single-ended signal and the load side single-ended signal is set to be higher than the frequency (e.g., several kHz) of the fundamental wave component included in the square wave power supply voltage output by the power supply unit 11. The lower limit of the second communication frequency band may be set to, for example, 1000 times or more, 5000 times or more, 10000 times or more, or 50000 times or more the frequency of the fundamental wave component included in the power supply voltage.

[0202] The cutoff frequency of the low-pass filters LP51 and LP61 (also referred to as the third LPF cutoff frequency) is set to, for example, a frequency equal to or higher than the frequency of the fundamental wave component included in the power supply voltage. The relationship between the third LPF cutoff frequency and the cutoff frequency of the high-pass filters HP51 and HP61 (also referred to as the third HPF cutoff frequency) may be the same as the relationship between the LPF cutoff frequency fc1 and the HPF cutoff frequency fc2 described above. The relationship between the third LPF cutoff frequency and the lower limit of the second communication frequency band may be the same as the relationship between the LPF cutoff frequency fc1 and the lower limit fmin of the communication frequency band FB described above. The relationship between the third HPF cutoff frequency and the lower limit of the second communication frequency band may be the same as the relationship between the HPF cutoff frequency fc2 and the lower limit fmin of the communication frequency band FB described above (for example, FIG. 4 or FIG. 5).

[0203] The orders of the low-pass filters LP51 and LP61 may be odd orders (five or more), or may be even orders. The gain frequency characteristics of the low-pass filters LP51 and LP61 may be different from each other. The cutoff frequencies of the low-pass filters LP51 and LP61 may be different from each other. The orders of the low-pass filters LP51 and LP61 may be different from each other.

[0204] The high-pass filters HP51 and HP61 may have different gain frequency characteristics, different cutoff frequencies, and different orders.

[0205] The constant of the inductor L52 of the power supply side interface circuit 14 may be different from the constant of the inductor L62 of the load side interface circuit 24. The constant of the inductor L52 may be set larger than the constant of the inductor L62, or the constant of the inductor L62 may be set larger than the constant of the inductor L52.

[0206] The load side interface circuit 24 does not necessarily have to be provided with the low-pass filter LP61. Moreover, the power supply side interface circuit 14 does not necessarily have to be provided with the low-pass filter LP51.

[0207] In the processing system 1C, the coupler CP51 may include an insulating transformer. In this case, one end of a primary coil of the insulating transformer is connected to the communication unit 13 and one end of a resistor R51, and the other end of the primary coil is connected to ground. Also, one end of a secondary coil of the insulating transformer is connected to one end of a capacitor C53, and the other end of the secondary coil is connected to ground.

[0208] The coupler CP61 may also include an isolation transformer. In this case, one end of a primary coil of the isolation transformer is connected to the communication unit 23 and one end of a resistor R61, and the other end of the primary coil is connected to ground. Also, one end of a secondary coil of the isolation transformer is connected to one end of a capacitor C63, and the other end of the secondary coil is connected to ground.

[0209] Furthermore, the power supply unit 11 may output only the positive power supply voltage out of the positive and negative power supply voltages, or may output only the negative power supply voltage out of the positive and negative power supply voltages, in which case the brushed motor can rotate in only one direction.

[0210] FIG. 9 is a schematic diagram showing an example of a processing system 1 in which the power supply unit 11 is a DC power supply unit that outputs a DC power supply voltage to be supplied to the load 21. In the processing system 1 shown in FIG. 7 (also referred to as processing system 1D), the power line 50 is composed of a first power line 57a and a second power line 57b. The first power line 57a transmits the DC power supply voltage output by the power supply unit 11. The second power line 57b is connected to the ground of the power supply unit 11. The second power line 57b can also be referred to as, for example, a ground wire. The power supply unit 11 outputs, for example, a positive DC power supply voltage. The DC power supply voltage output by the power supply unit 11 may be several volts.

[0211] The load 21 may be a brushed motor that operates at a low voltage, or may be other equipment that operates on a DC power supply voltage. When the load 21 is a brushed motor, a first power line 57a may be connected to one electrode of the brushed motor, and a second power line 57b may be connected to the other electrode of the brushed motor. In this case, the brushed motor is supplied with a DC power supply voltage.

[0212] The power supply side interface circuit 14 included in the processing system 1D includes, for example, a low-pass filter unit LPG7 having low-pass filters LP71 and LP72, and a coupler unit CPG7. The load side interface circuit 24 included in the processing system 1D includes, for example, a low-pass filter unit LPG8 having low-pass filters LP81 and LP82, and a coupler unit CPG8.

[0213] The coupler unit CPG7 has couplers CP71 and CP72. The coupler CP71 superimposes one power supply side communication signal of the power supply side differential signals transmitted by the communication unit 13 onto the first power line 57a. The coupler CP72 superimposes the other power supply side communication signal of the power supply side differential signals transmitted by the communication unit 13 onto the second power line 57b.

[0214] The coupler unit CPG8 has couplers CP81 and CP82. The coupler CP81 superimposes one power supply side communication signal of the power supply side differential signals transmitted by the communication unit 23 onto the first power line 57a. The coupler CP82 superimposes the other power supply side communication signal of the power supply side differential signals transmitted by the communication unit 23 onto the second power line 57b.

[0215] The coupler CP71 extracts one load side communication signal from the first power line 57a on which the one load side communication signal is superimposed, and outputs the signal to the communication unit 13. The coupler CP72 extracts the other load side communication signal from the second power line 57b on which the other load side communication signal is superimposed, and outputs the other load side communication signal to the communication unit 13.

[0216] The coupler CP81 extracts one power supply side communication signal from the first power line 57a on which the one power supply side communication signal is superimposed, and outputs the signal to the communication unit 23. The coupler CP82 extracts the other power supply side communication signal from the second power line 57b on which the other power supply side communication signal is superimposed, and outputs the other power supply side communication signal to the communication unit 23.

[0217] The coupler CP71 is composed of, for example, a capacitor C75 and a resistor R71. One end of the capacitor C75 is connected to the communication unit 13 and one end of the resistor R71, and the other end of the capacitor C75 is connected to the first power line 57a. The coupler CP72 is composed of, for example, a capacitor C76 and a resistor R72. One end of the capacitor C76 is connected to the communication unit 13 and one end of the resistor R72, and the other end of the capacitor C76 is connected to the second power line 57b. The other end of the resistor R72 is connected to the other end of the resistor R71. A bias voltage Vb71 is applied to the other end of the resistor R72 and the other end of the resistor R71.

[0218] The coupler CP81 is composed of, for example, a capacitor C85 and a resistor R81. One end of the capacitor C85 is connected to the communication unit 23 and one end of the resistor R81, and the other end of the capacitor C85 is connected to the first power line 57a. The coupler CP82 is composed of, for example, a capacitor C86 and a resistor R82. One end of the capacitor C86 is connected to the communication unit 23 and one end of the resistor R82, and the other end of the capacitor C86 is connected to the second power line 57b. The other end of the resistor R82 is connected to the other end of the resistor R81. A bias voltage Vb81 is applied to the other end of the resistor R82 and the other end of the resistor R81.

[0219] The coupler CP71 constitutes a high-pass filter HP71. That is, the capacitor C75 and the resistor R71 constitute the high-pass filter HP71. The high-pass filter HP71 performs high-pass filtering on one of the power supply side communication signals transmitted by the communication unit 13. The one of the power supply side communication signals that has been high-pass filtered by the high-pass filter HP71 is superimposed on the first power line 57a. The high-pass filter HP71 also performs high-pass filtering on one of the load side communication signals extracted from the first power line 57a. The one of the load side communication signals that has been high-pass filtered by the high-pass filter HP71 is received by the communication unit 13.

[0220] The coupler CP72 constitutes a high-pass filter HP72. The high-pass filter HP72 performs high-pass filtering on the other power supply side communication signal transmitted by the communication unit 13. The other power supply side communication signal that has been high-pass filtered by the high-pass filter HP72 is superimposed on the second power line 57b. The high-pass filter HP72 also performs high-pass filtering on the other load side communication signal extracted from the second power line 57b. The other load side communication signal that has been high-pass filtered by the high-pass filter HP72 is received by the communication unit 13.

[0221] The coupler CP81 constitutes a high-pass filter HP81. The high-pass filter HP81 performs high-pass filtering on one of the load-side communication signals transmitted by the communication unit 23. The one of the load-side communication signals that has been high-pass filtered by the high-pass filter HP81 is superimposed on the first power line 57a. The high-pass filter HP81 also performs high-pass filtering on one of the power-supply-side communication signals extracted from the first power line 57a. The one of the power-supply-side communication signals that has been high-pass filtered by the high-pass filter HP81 is received by the communication unit 23.

[0222] The coupler CP82 constitutes a high-pass filter HP82. The high-pass filter HP82 performs high-pass filtering on the other load side communication signal transmitted by the communication unit 23. The other load side communication signal that has been high-pass filtered by the high-pass filter HP82 is superimposed on the second power line 57b. The high-pass filter HP82 also performs high-pass filtering on the other power supply side communication signal extracted from the second power line 57b. The other power supply side communication signal that has been high-pass filtered by the high-pass filter HP82 is received by the communication unit 23.

[0223] The orders of the high-pass filters HP71, HP72, HP81, and HP82 are, for example, second order. The gain frequency characteristics of the high-pass filters HP71, HP72, HP81, and HP82 may be the same. Furthermore, the cutoff frequencies of the high-pass filters HP71, HP72, HP81, and HP82 may be the same.

[0224] The low-pass filter unit LPG7 includes, for example, inductors L71, L72, L73, and L74 and a capacitor C71. The inductors L71 and L72 are connected in series to each other and inserted into the first power line 57a. One end of the inductor L71 is connected to the power supply unit 11, and the other end of the inductor L71 is connected to one end of the inductor L72. The other end of the inductor L72 is connected to the other end of the capacitor C75 of the coupler CP71 and the cable 60. The DC power supply voltage output by the power supply unit 11 is input to one end of the inductor L71.

[0225] Inductors L73 and L74 are connected in series to each other and inserted into the second power line 57b. One end of inductor L73 is connected to the power supply unit 11, and the other end of inductor L73 is connected to one end of inductor L74. The other end of inductor L74 is connected to the other end of capacitor C76 of coupler CP72 and to the cable 60. One end of inductor L73 is connected to the ground of the power supply unit 11.

[0226] One end of the capacitor C71 is connected to the other end of the inductor L71 and one end of the inductor L72, and the other end of the capacitor C71 is connected to the other end of the inductor L73 and one end of the inductor L74.

[0227] In the low-pass filter unit LPG7, inductors L71 and L72 and a capacitor C71 form a low-pass filter LP71. The low-pass filter LP71 is inserted in the first power line 57a. In addition, in the low-pass filter unit LPG7, inductors L73 and L74 and a capacitor C71 form a low-pass filter LP72. The low-pass filter LP72 is inserted in the second power line 57b. The orders of the low-pass filters LP71 and LP72 are, for example, third order.

[0228] In the low-pass filter unit LPG8, inductors L81 and L82 and a capacitor C81 form a low-pass filter LP81. The low-pass filter LP81 is inserted in the first power line 57a. In the low-pass filter unit LPG8, inductors L83 and L84 and a capacitor C81 form a low-pass filter LP82. The low-pass filter LP82 is inserted in the second power line 57b. The orders of the low-pass filters LP81 and LP82 are, for example, third order.

[0229] The DC power supply voltage output from the power supply unit 11 is supplied to the load 21 via a low-pass filter LP71 and a low-pass filter LP81.

[0230] As described above, in the power supply side interface circuit 14 of the processing system 1D, the low-pass filters LP71 and LP72 are inserted in the first power line 57a and the second power line 57b connected to the power supply unit 11. Therefore, even if high-frequency noise occurs in the power supply unit 11, the high-frequency noise is less likely to be transmitted to the power supply side communication unit 13 and the load side system 20.

[0231] Furthermore, even if high frequency noise occurs in at least one of the power supply side communication unit 13 and the load side system 20, the high frequency noise is less likely to be transmitted to the power supply unit 11 by the low pass filter unit LPG7.

[0232] Furthermore, in this example, since the couplers CP71 and CP72 function as high-pass filters HP71 and HP72, even if low-frequency noise occurs in the power supply side communication unit 13, the low-frequency noise is less likely to be superimposed on the first power line 57a and the second power line 57b. Therefore, the low-frequency noise is less likely to be transmitted to the power supply unit 11 and the load side system 20. Furthermore, even if low-frequency noise occurs in at least one of the power supply unit 11 and the load side system 20, the low-frequency noise is less likely to be transmitted to the power supply side communication unit 13.

[0233] In this example, the low-pass filter LP71 inserted in the first power line 57a has inductors L71 and L72 on both ends thereof. The inductor L72 on the coupler CP71 side functions as an impedance upper for the power-supply-side communication signal that the coupler CP71 superimposes on the first power line 57a, making it difficult for the power-supply-side communication signal superimposed on the first power line 57a to propagate toward the power supply unit 11. This makes it difficult for the signal level of the power-supply-side communication signal that is input to the load-side communication unit 23 via the first power line 57a to decrease. In addition, the inductor L72 functions as an impedance upper for the load-side communication signal that the coupler CP71 superimposes on the first power line 57a, making it difficult for the load-side communication signal that is superimposed on the first power line 57a to propagate toward the power supply unit 11. This makes it difficult for the signal level of the load-side communication signal that is input to the power-supply-side communication unit 13 via the first power line 57a to decrease. On the other hand, since the inductor L71 is present on the side of the power supply unit 11, even if the output impedance of the power supply unit 11 is low, the low-pass filter LP71 can appropriately attenuate high-frequency noise generated in the power supply unit 11. The same can be said for the low-pass filter LP72 inserted in the second power line 57b.

[0234] Furthermore, in the load-side interface circuit 24, low-pass filters LP81 and LP82 are inserted in the first power line 57a and the second power line 57b connected to the power supply unit 11. Therefore, even if high-frequency noise occurs in the power supply unit 11, the high-frequency noise is less likely to be transmitted to the load 21.

[0235] Furthermore, even if high-frequency noise occurs in at least one of the load-side communication unit 23 and the power-supply-side communication unit 13, the low-pass filters LP81 and LP82 make it difficult for the high-frequency noise to be transmitted to the load 21. Furthermore, even if high-frequency noise occurs in the load 21, the low-pass filter unit LPG8 makes it difficult for the high-frequency noise to be transmitted to the load-side communication unit 23 and the power-supply-side system 10.

[0236] Furthermore, in this example, since the couplers CP81 and CP82 function as high-pass filters HP81 and HP82, respectively, even if low-frequency noise occurs in the load-side communication unit 23, the low-frequency noise is less likely to be superimposed on the first power line 57a and the second power line 57b. Therefore, the low-frequency noise is less likely to be transmitted to the load 21 and the power supply-side system 10. Furthermore, even if low-frequency noise occurs in at least one of the load 21 and the power supply-side system 10, the low-frequency noise is less likely to be transmitted to the load-side communication unit 23.

[0237] In this example, the low-pass filter LP81 inserted in the first power line 57a has inductors L81 and L82 on both ends thereof. The inductor L82 on the coupler CP81 side functions as an impedance upper for the load-side communication signal that the coupler CP81 superimposes on the first power line 57a, making it difficult for the load-side communication signal superimposed on the first power line 57a to propagate toward the load 21. This makes it difficult for the signal level of the load-side communication signal that is transmitted through the first power line 57a and input to the power-source-side communication unit 13 to decrease. In addition, the inductor L82 functions as an impedance upper for the power-source-side communication signal that the coupler CP81 superimposes on the first power line 57a, making it difficult for the power-source-side communication signal that is superimposed on the first power line 57a to propagate toward the load 21. This makes it difficult for the signal level of the power-source-side communication signal that is transmitted through the first power line 57a and input to the load-side communication unit 23 to decrease. On the other hand, because the inductor L81 is present on the load 21 side, even if the impedance seen from the low-pass filter LP81 side of the load 21 is low, the low-pass filter LP81 can appropriately attenuate high-frequency noise output from the load 21. The same can be said for the low-pass filter LP82 inserted in the second power line 57b.

[0238] The low-pass filters LP71, LP72, LP81, and LP82 may have the same gain frequency characteristics. The low-pass filters LP71, LP72, LP81, and LP82 may have the same cutoff frequencies. The relationship between the cutoff frequencies of the low-pass filters LP71, LP72, LP81, and LP82 and the lower limit value fmin of the communication frequency band FB may be the same as the relationship between the LPF cutoff frequency fc1 and the lower limit value fmin of the communication frequency band FB described above.

[0239] The relationship between the cutoff frequencies of the low-pass filters LP71, LP72, LP81, and LP82 and the cutoff frequencies of the high-pass filters HP71, HP72, HP81, and HP82 may be the same as the relationship between the LPF cutoff frequency fc1 and the HPF cutoff frequency fc2 described above. The relationship between the cutoff frequencies of the high-pass filters HP71, HP72, HP81, and HP82 and the lower limit value fmin of the communication frequency band FB may be the same as the relationship between the HPF cutoff frequency fc2 and the lower limit value fmin of the communication frequency band FB described above.

[0240] In the processing system 1D, as shown in FIG. 10, the coupler CP71 may include an isolation transformer T71. In this case, one end of a primary coil L77 of the isolation transformer T71 is connected to the communication unit 13 and one end of a resistor R71. The other end of the primary coil L77 is connected to the communication unit 13 and one end of a resistor R72. One end and the other end of a secondary coil L78 of the isolation transformer T71 are connected to one ends of capacitors C75 and C76, respectively. In the example of FIG. 10, the capacitor C75, the isolation transformer T71, and the resistor R71 form a high-pass filter HP71. The capacitor C76, the isolation transformer T71, and the resistor R72 form the high-pass filter HP71.

[0241] 10, the coupler CP81 may also include an isolation transformer T81. In this case, one end of a primary coil L87 of the isolation transformer T81 is connected to the communication unit 23 and one end of a resistor R81. The other end of the primary coil L87 is connected to the communication unit 23 and one end of a resistor R82. One end and the other end of a secondary coil L88 of the isolation transformer T81 are connected to one end of capacitors C85 and C86, respectively. In the example of FIG. 10, the capacitor C85, the isolation transformer T81, and the resistor R81 form a high-pass filter HP81. The capacitor C86, the isolation transformer T81, and the resistor R82 form a high-pass filter HP82.

[0242] The orders of the low-pass filters LP71, LP72, LP81, and LP82 may be odd orders (five or more), or may be even orders. At least two of the low-pass filters LP71, LP72, LP81, and LP82 may have different gain-frequency characteristics. At least two of the low-pass filters LP71, LP72, LP81, and LP82 may have different cutoff frequencies. At least two of the low-pass filters LP71, LP72, LP81, and LP82 may have different orders.

[0243] At least two of the high-pass filters HP71, HP72, HP81, and HP82 may have different gain-frequency characteristics. At least two of the high-pass filters HP71, HP72, HP81, and HP82 may have different cutoff frequencies. At least two of the high-pass filters HP71, HP72, HP81, and HP82 may have different orders.

[0244] The constant of inductor L72 of the power supply side interface circuit 14 and the constant of inductor L82 of the load side interface circuit 24 may be different from each other. The constant of inductor L72 may be set larger than the constant of inductor L82, or the constant of inductor L82 may be set larger than the constant of inductor L72. Similarly, the constant of inductor L74 of the power supply side interface circuit 14 and the constant of inductor L84 of the load side interface circuit 24 may be different from each other.

[0245] The load side interface circuit 24 does not necessarily have to be provided with the low-pass filter unit LPG8, and the power supply side interface circuit 14 does not necessarily have to be provided with the low-pass filter unit LPG7.

[0246] The power supply side communication unit 13 and the load side communication unit 23 may perform single-ended communication. In this case, the power supply side single-ended signal output by the power supply side communication unit 13 is superimposed on either the first power line 57a or the second power line 57b. Also, the load side single-ended signal output by the load side communication unit 23 is superimposed on either the first power line 57a or the second power line 57b. In the example of FIG. 9, if the power supply side single-ended signal is superimposed on, for example, the first power line 57a, the capacitor C76 and the resistor R72 are unnecessary in the coupler unit CPG7. Also, in the example of FIG. 9, if the load side single-ended signal is superimposed on, for example, the first power line 57a, the capacitor C86 and the resistor R82 are unnecessary in the coupler unit CPG8. 10, when the power supply side single-ended signal is superimposed on, for example, the first power line 57a, the capacitor C76 and the resistor R72 are not required in the coupler unit CPG7, and one end of the primary side coil L77 and the secondary side coil L78 are connected to ground. Also, in the example of Fig. 10, when the load side single-ended signal is superimposed on, for example, the first power line 57a, the capacitor C86 and the resistor R82 are not required in the coupler unit CPG8, and one end of the primary side coil L87 and the secondary side coil L88 are connected to ground.

[0247] The low-pass filter unit LPG7 does not need to include the inductors L71 and L73. For example, when no AC component flows through the first power line 57a and the second power line 57b, or when the AC component is very small even if it flows through the first power line 57a and the second power line 57b, the low-pass filter unit LPG7 does not need to include the inductors L71 and L73.

[0248] Furthermore, the low-pass filter unit LPG8 does not need to include the inductors L81 and L83. For example, when no AC component flows through the first power line 57a and the second power line 57b, or when the AC component is very small even if it flows through the first power line 57a and the second power line 57b, the low-pass filter unit LPG8 does not need to include the inductors L81 and L83.

[0249] Fig. 11 is a schematic diagram showing the configuration shown in Fig. 9 in which the low-pass filter unit LPG7 does not include inductors L71 and L73, and the low-pass filter unit LPG8 does not include inductors L81 and L83. In the configuration shown in Fig. 10, the low-pass filter unit LPG7 does not have to include inductors L71 and L73. In the configuration shown in Fig. 10, the low-pass filter unit LPG8 does not have to include inductors L81 and L83.

[0250] The functions of the elements disclosed herein may be implemented using circuitry or processing circuitry, including general-purpose processors, special-purpose processors, integrated circuits, ASICs ("application-specific integrated circuits"), conventional circuitry, and / or combinations thereof, configured to perform the disclosed elements or programmed to perform the disclosed functions. A processor is considered to be processing circuitry or circuitry when it includes transistors and other circuitry therein. In this disclosure, a circuitry, unit, or means is hardware that performs the recited function or hardware programmed to perform the function. The hardware may be any hardware disclosed herein or other known hardware that is programmed to perform or configured to perform the recited function. When the hardware is a processor, which may be considered as a type of circuitry, the circuitry, means, or unit is a combination of hardware and software, software used to configure the hardware, and / or processor.

[0251] Although the processing system has been described in detail above, the above description is merely an example in all respects, and the present disclosure is not limited thereto. Furthermore, the various modifications described above can be combined and applied as long as they are not mutually inconsistent. It is understood that countless modifications not illustrated can be envisioned without departing from the scope of the present disclosure.

[0252] The present disclosure includes the following aspects.

[0253] An interface circuit according to a first aspect includes a first coupler that superimposes a first communication signal on a first power line that transmits a square-wave first power supply voltage, or that extracts the first communication signal from the first power line that transmits the square-wave first power supply voltage and on which the first communication signal is superimposed, and a first low-pass filter that is inserted into the first power line and connected to the first coupler, and the first low-pass filter has a first inductor on each end of the first low-pass filter.

[0254] An interface circuit according to a second aspect is the interface circuit according to the first aspect, wherein the cutoff frequency of the first low-pass filter is equal to or lower than the lower limit of the frequency band of the first communication signal.

[0255] An interface circuit according to a third aspect is the interface circuit according to the second aspect, wherein the cutoff frequency of the first low-pass filter is equal to or less than one-third of the lower limit value.

[0256] An interface circuit according to a fourth aspect is the interface circuit according to the second or third aspect, wherein the first coupler forms a high-pass filter, the cutoff frequency of the high-pass filter is equal to or lower than the lower limit value, and the cutoff frequency of the first low-pass filter is lower than the cutoff frequency of the high-pass filter.

[0257] An interface circuit according to a fifth aspect is the interface circuit according to the fourth aspect, wherein the difference between the cutoff frequency of the high-pass filter and the cutoff frequency of the first low-pass filter is equal to or greater than half the frequency bandwidth of the communication signal.

[0258] An interface circuit according to a sixth aspect is an interface circuit according to any one of the first to fifth aspects, wherein the first coupler forms a high-pass filter, and the order of the first low-pass filter is greater than the order of the high-pass filter.

[0259] An interface circuit according to a seventh aspect is the interface circuit according to any one of the first to sixth aspects, wherein the order of the first low-pass filter is odd.

[0260] An interface circuit according to an eighth aspect is an interface circuit according to any one of the first to seventh aspects, and includes a second coupler that superimposes a second communication signal, which constitutes a differential signal with the first communication signal, onto a second power line that transmits a square-wave second power supply voltage, or extracts the second communication signal from the second power line that transmits the square-wave second power supply voltage and on which the second communication signal, which constitutes a differential signal with the first communication signal, is superimposed, and a second low-pass filter that is inserted into the second power line and connected to the second coupler, and the second low-pass filter has a second inductor on each end of the second low-pass filter.

[0261] A communication device according to a ninth aspect includes an interface circuit according to any one of the first to eighth aspects and a communication unit that transmits the first communication signal to the first coupler, and the first coupler superimposes the first communication signal transmitted from the communication unit onto the first power line.

[0262] A communication device according to a tenth aspect includes an interface circuit according to any one of the first to eighth aspects, and a communication unit that receives the first communication signal extracted by the first coupler from the first power line on which the first communication signal is superimposed.

[0263] An interface system according to an eleventh aspect includes a first interface circuit that is the interface circuit according to any one of the first to eighth aspects, and a second interface circuit connected to the first interface circuit via the first power line, wherein the first coupler superimposes the first communication signal on the first power line and is connected to the first inductor on the second interface circuit side of the first low-pass filter, the second interface circuit includes a third coupler that extracts the first communication signal from the first power line on which the first communication signal is superimposed, and a third low-pass filter that is inserted into the first power line and connected to the third coupler, the third low-pass filter having a third inductor on each end of the third low-pass filter, and the third coupler is connected to the third inductor on the first interface circuit side of the third low-pass filter.

[0264] The interface system according to the twelfth aspect is the interface system according to the eleventh aspect, wherein the constant of the first inductor on the second interface circuit side of the first low-pass filter and the constant of the third inductor on the first interface circuit side of the third low-pass filter are different from each other.

[0265] An interface system according to a thirteenth aspect is an interface system according to the eleventh or twelfth aspect, wherein the third coupler superimposes a third communication signal onto the first power line, and the first coupler extracts the third communication signal from the first power line on which the third communication signal is superimposed.

[0266] An interface system according to a fourteenth aspect is an interface system according to any one of the eleventh to thirteenth aspects, wherein the first power supply voltage, which is a square wave, is input to the first inductor on the opposite side of the first low-pass filter from the second interface circuit side, the first power line transmits the first power supply voltage output from the first low-pass filter to the second interface circuit, the first power supply voltage transmitted by the first power line is input to the third inductor on the first interface circuit side of the third low-pass filter, and the third inductor on the opposite side of the third low-pass filter from the first interface circuit side is connected to a load.

[0267] An interface system according to a 15th aspect is an interface system according to any one of the 11th to 13th aspects, wherein the first power supply voltage, which is a square wave, is input to the third inductor on the opposite side of the third low-pass filter from the first interface circuit side, the first power line transmits the first power supply voltage output from the third low-pass filter to the first interface circuit, the first inductor on the second interface circuit side of the first low-pass filter is input to the first power supply voltage transmitted by the first power line, and the first inductor on the opposite side of the first low-pass filter from the second interface circuit side is connected to a load.

[0268] A communication system according to a 16th aspect includes an interface system according to any one of the 11th to 15th aspects, a first communication unit that transmits the first communication signal to the first coupler, and a second communication unit that receives the first communication signal extracted by the third coupler from the first power line on which the first communication signal is superimposed.

[0269] An interface circuit according to a seventeenth aspect includes a coupler that superimposes a communication signal onto a power line that transmits a DC power supply voltage, or extracts the communication signal from a power line that transmits a DC power supply voltage and on which the communication signal is superimposed, and a low-pass filter that is inserted into the power line and electrically connected to the coupler, the low-pass filter having an inductor located at one end of the low-pass filter and electrically connected to the coupler. [Explanation of symbols]

[0270] 12 Power supply side communication device 13 Power supply communication section 14 Power supply side interface circuit 22 Load side communication device 23 Load side communication section 24 Load side interface circuit 32 Communication Systems 34 Interface System 51 U phase power line 52 V phase power line 53 W phase power line 55a, 57a 1st power line 55b, 57b 2nd power line 56 Power Lines CP11, CP12, CP21, CP22, CP51, CP61, CP71, CP72, CP81, CP82 Couplers FB frequency band fc1, fc2 cutoff frequencies fmin lower limit HP11, HP12, HP21, HP22, HP51, HP61, HP71, HP72, HP81, HP82 high-pass filters LP11, LP12, LP13, LP21, LP22, LP23, LP31, LP32, LP41, LP42, LP51, LP61, LP71, LP72, LP81, LP82 low-pass filters L12, L14, L22, L24, L32, L34, L42, L44, L52, L62, L72, L82 inductors

Claims

1. a first coupler that superimposes a first communication signal on a first power line that transmits a first power supply voltage having a rectangular wave, or that extracts the first communication signal from the first power line that transmits the first power supply voltage having a rectangular wave and on which the first communication signal is superimposed; a first low-pass filter inserted in the first power line and connected to the first coupler; Equipped with The first low pass filter includes a first inductor on each end of the first low pass filter.

2. 2. The interface circuit of claim 1, an interface circuit, wherein the cutoff frequency of the first low-pass filter is equal to or lower than a lower limit of a frequency band of the first communication signal;

3. 3. An interface circuit according to claim 2, An interface circuit, wherein the cutoff frequency of the first low-pass filter is equal to or less than one-third of the lower limit value.

4. 4. The interface circuit according to claim 2, wherein: the first coupler constitutes a high-pass filter; the cutoff frequency of the high-pass filter is equal to or less than the lower limit; An interface circuit, wherein the cutoff frequency of the first low-pass filter is lower than the cutoff frequency of the high-pass filter.

5. 5. An interface circuit according to claim 4, an interface circuit, wherein a difference between the cutoff frequency of the high-pass filter and the cutoff frequency of the first low-pass filter is equal to or greater than half the frequency bandwidth of the communication signal;

6. 4. The interface circuit according to claim 1, the first coupler constitutes a high-pass filter; The interface circuit, wherein the order of the first low-pass filter is greater than the order of the high-pass filter.

7. 4. The interface circuit according to claim 1, The interface circuit, wherein the first low-pass filter has an odd order.

8. 4. The interface circuit according to claim 1, a second coupler that superimposes a second communication signal, which constitutes a differential signal with the first communication signal, on a second power line that transmits a square-wave second power supply voltage, or extracts the second communication signal from the second power line that transmits the square-wave second power supply voltage and on which the second communication signal, which constitutes a differential signal with the first communication signal, is superimposed; a second low-pass filter inserted in the second power line and connected to the second coupler; Equipped with The second low pass filter has a second inductor on each end of the second low pass filter.

9. an interface circuit according to any one of claims 1 to 3; a communication unit that transmits the first communication signal to the first coupler; Equipped with The first coupler superimposes the first communication signal transmitted from the communication unit onto the first power line.

10. an interface circuit according to any one of claims 1 to 3; a communication unit that receives the first communication signal extracted by the first coupler from the first power line on which the first communication signal is superimposed; A communication device comprising:

11. a first interface circuit that is the interface circuit according to any one of claims 1 to 3; a second interface circuit connected to the first interface circuit through the first power line; Equipped with the first coupler superimposes the first communication signal on the first power line and is connected to the first inductor on the second interface circuit side of the first low-pass filter; The second interface circuit a third coupler that extracts the first communication signal from the first power line on which the first communication signal is superimposed; a third low-pass filter inserted in the first power line and connected to the third coupler; and the third low-pass filter has a third inductor at each end of the third low-pass filter, The third coupler is connected to the third inductor on the first interface circuit side of the third low-pass filter.

12. 12. The interface system of claim 11, an interface system in which the constant of the first inductor on the second interface circuit side of the first low-pass filter and the constant of the third inductor on the first interface circuit side of the third low-pass filter are different from each other.

13. 12. The interface system of claim 11, the third coupler superimposes a third communication signal on the first power line; The first coupler extracts the third communication signal from the first power line on which the third communication signal is superimposed.

14. 12. The interface system of claim 11, the first power supply voltage having a square wave is input to the first inductor on the opposite side of the first low-pass filter from the second interface circuit side; the first power line transmits the first power supply voltage output from the first low-pass filter to the second interface circuit; the first power supply voltage transmitted through a first power line is input to the third inductor on the first interface circuit side of the third low-pass filter; The third inductor on the opposite side of the third low-pass filter from the first interface circuit is connected to a load.

15. 12. The interface system of claim 11, the first power supply voltage having a square wave is input to the third inductor on the opposite side of the third low-pass filter from the first interface circuit side, the first power line transmits the first power supply voltage output from the third low-pass filter to the first interface circuit; the first power supply voltage transmitted through the first power line is input to the first inductor on the second interface circuit side of the first low-pass filter; The first inductor on the opposite side of the first low-pass filter from the second interface circuit is connected to a load.

16. An interface system according to claim 11; a first communication unit that transmits the first communication signal to the first coupler; a second communication unit that receives the first communication signal extracted by the third coupler from the first power line on which the first communication signal is superimposed; A communication system comprising:

17. a coupler for superimposing a communication signal onto a power line transmitting a DC power supply voltage, or for extracting the communication signal from a power line transmitting a DC power supply voltage and on which the communication signal is superimposed; a low-pass filter inserted in the power line and electrically connected to the coupler; Equipped with The low-pass filter includes an inductor located at one end of the low-pass filter and electrically connected to the coupler.

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