JP2019047165A - Differential communication device - Google Patents

Abstract

To allow for superposition of DC power on a differential signal, while maintaining immunity performance, in a differential communication device performing communication by using the differential signal superposed with the DC power.SOLUTION: A differential communication device performing communication by using a differential signal superposed with DC power has a connector for connection with an external signal line transmitting the differential signal, a common mode choke coil provided on a pair of signal lines connecting a communication circuit performing communication and the connector, a power circuit for supplying or receiving the DC power superposed on the differential signal, a capacitive element provided between the communication circuit and the common mode choke coil corresponding to each of the pair of signal lines, and connected between the communication circuit and the common mode choke coil, and a pair of regulator circuits including an inductive element for connection between the power circuit and the common mode choke coil.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a differential communication device.

  In communication systems that communicate using differential signals, communication systems called Power over Data Lines (PoDL), Power over Ethernet (PoE), etc. are known that supply power by superimposing DC power on the differential signals. There is.

  In addition, a transformer including two feed winding portions connected to the feed circuit, a signal winding portion connected to the signal transmission circuit, and a common mode choke coil connected between the transformer and the cable There is known a two-wire power feeding communication device having the same (for example, see Patent Document 1).

JP 2003-46655

  In the technique disclosed in Patent Document 1, two feed winding portions are connected in series via a capacitor, and one terminal of the capacitor is connected to, for example, a circuit ground potential. As described above, when only power is supplied to the differential communication path, a circuit element such as a capacitor can be added between the differential communication paths in order to prevent the differential communication paths from becoming unbalanced. .

  On the other hand, for example, in a differential communication device that transmits high-speed signals of several tens of Mbps to several hundreds of Mbps, such as in-vehicle Ethernet (Ethernet: registered trademark), DC power is superimposed on each of the differential communication paths. A circuit (regulator circuit) is provided. In this case, there is a problem that the differential communication path becomes unbalanced and the immunity performance (anti-noise performance) is lowered due to the variation of the circuit elements included in the regulator circuit.

  The embodiment of the present invention has been made in view of the above problems, and in a differential communication apparatus that performs communication using a differential signal on which direct current power is superimposed, maintaining immunity performance. It is possible to superimpose DC power on the differential signal.

  In order to solve the above problems, a differential communication device according to an embodiment of the present invention is a differential communication device which performs communication using a differential signal on which direct current power is superimposed, and the differential signal is A connector connected to an external signal line to be transmitted, a common mode choke coil provided on a pair of signal lines connecting between the communication circuit for performing communication and the connector, and the DC superimposed on the differential signal It is provided between the communication circuit and the common mode choke coil corresponding to each of the pair of signal lines and a power circuit for supplying or receiving power, and between the communication circuit and the common mode choke coil. And a pair of regulator circuits including an inductive element connected between the power circuit and the common mode choke coil.

  In a differential communication device that communicates using differential signals, it is important that the differential signals be well balanced, and if unbalanced, common noise components are converted to differential signal components, causing communication errors It becomes a factor.

  Therefore, in the present invention, noting that the cause of the differential communication error is that common mode noise is mode converted to a differential signal, the common component is removed by the common mode choke coil and the signal component is stabilized. Provide a regulator circuit at the place where As a result, the differential communication device can stabilize (balance) the differential communication path, so that it is possible to superimpose DC power on the differential signal while maintaining the immunity performance.

  According to the embodiment of the present invention, in a differential communication device that performs communication using a differential signal on which direct current power is superimposed, direct current power can be superimposed on the differential signal while maintaining the immunity performance. It will be.

FIG. 1 is a diagram showing an example of the configuration of a differential communication system according to an embodiment. It is a figure which shows an example of the characteristic of the common mode choke coil which concerns on one Embodiment. It is a figure which shows an example of the influence by the addition of the regulator circuit which concerns on one Embodiment. It is a figure which shows an example of improvement of the immunity performance which concerns on one Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Configuration of Differential Communication System>
FIG. 1 is a diagram showing an example of the configuration of a differential communication system according to an embodiment. The differential communication system 100 is a communication system that performs high-speed communication such as on-vehicle Ethernet between the first communication device 110 and the second communication device 120 using a differential signal on which direct current power is superimposed. It is. Here, as an example, the following description will be made on the assumption that the differential communication system 100 is a communication system conforming to PoDL (Power over Data Lines) which is being standardized by IEEE 802.3bu.

  The PoDL is a communication in which differential signals for transmitting data and DC power are transmitted between the first communication device 110 and the second communication device 120 via, for example, a pair of signal lines such as the cable 130. It is a system. Since this eliminates the need for a power line for supplying power, it is expected, for example, to become a general technology as a communication system in a vehicle such as a car.

  In the example of FIG. 1, the first communication device 110 can function as a power supply device (PSE: Power Sourcing Equipment), and can supply DC power to the second communication device 120 via the cable 130. The second communication device 120 functions as a power receiving device (PD: Powered Device), and can receive and use DC power supplied from the first communication device 110 via the cable 130.

(Configuration of first communication device)
The first communication device 110 is an example of a differential communication device that performs communication using a differential signal on which direct current power is superimposed, and the connector 111, the communication circuit 112, the common mode choke coil 113, and the regulator circuits 114a and 114b. , A feed circuit 115, a DC power supply 116, and the like.

  The connector 111 is an interface used to connect the first communication device 110 to a cable 130 which is an example of an external signal line for transmitting a differential signal on which direct current power is superimposed.

  The communication circuit 112 is a circuit that communicates with the second communication device 120 using a differential signal, and is realized by, for example, an IC (Integrated Circuit) for communication. The communication circuit 112 includes, for example, a transmission / reception unit that transmits / receives data by differential signals, a communication control unit that controls communication, and the like, and communicates with the second communication device 120 at a communication speed of several tens of Mbps to several hundreds of Mbps. I do. The communication circuit 112 is connected to the connector 111 via the pair of signal lines 131a and 131b.

  The common mode choke coil 113 is provided on a pair of signal lines 131a and 131b connecting the communication circuit 112 and the connector 111, and generates common mode noise of differential signals transmitted by the pair of signal lines 131a and 131b. It has a suppressing function. The common mode choke coil 113 may be called a common mode filter or the like.

  Communication using differential signals (hereinafter referred to as differential communication) is less susceptible to external noise, ground, etc., and the magnetic field around the pair of signal lines is canceled, so there is an advantage of less unnecessary radiation. Are used in many high-speed data communications.

  However, even in such differential communication, for example, the asymmetry of the pair of signal lines transmitting the differential signal, the variation of the circuit elements of the pair of regulator circuits 114a and 114b supplying DC power to the differential signal, etc. , Common mode noise (common mode noise) may occur.

  The common mode noise generated in such a case is also generated in the same frequency band as the communication signal transmitted as a differential signal, and therefore can not be removed by a frequency separation type low pass filter or the like. The common mode choke coil 113 has a function of separating a communication signal transmitted as a differential signal and common mode noise according to the difference in transmission mode, and selectively suppressing common mode noise.

  The common mode choke coil 113 has, for example, a structure in which a pair of coils connected to a pair of signal lines 131a and 131b transmitting differential signals is wound around a core and magnetically coupled. Further, the winding directions of the pair of coils are opposite to each other.

  Thus, when common mode noise is input to common mode choke coil 113, the magnetic fluxes generated in the pair of coils intensify each other, and common mode choke coil 113 generates a high impedance to block the passage of common mode noise. . On the other hand, when the differential signal is input to the common mode choke coil 113, the magnetic flux generated in the pair of coils is canceled, and the common mode choke coil 113 does not generate high impedance and passes the differential signal.

  The feed circuit (an example of a power circuit) 115 is a circuit that feeds DC power superimposed on the pair of signal lines 131 a and 131 b. The feed circuit 115 supplies DC power to the pair of signal lines 131a and 131b via the pair of regulator circuits 114a and 114b using the DC voltage output from the DC power supply 116.

  The regulator circuits 114a and 114b are provided between the communication circuit 112 and the connector 111 corresponding to each of the pair of signal lines 131a and 131b transmitting differential signals, and the power supply circuit 115 corresponds to the pair of signal lines 131a and 131b. It is used to supply DC power to 131b.

  The pair of regulator circuits 114 a and 114 b respectively include a capacitor 117 connected between the communication circuit 112 and the common mode choke coil 113, and an inductor 118 connected between the feed circuit 115 and the common mode choke coil 113. Have.

  The capacitor (capacitive element) 117 passes the communication signal used by the communication circuit 112 for communication, and cuts off the DC power supplied by the power supply circuit 115. Further, the inductor (induction element) 118 passes the DC power supplied by the power feeding circuit 115 and blocks the communication signal used by the communication circuit 112 for communication.

  For example, in the differential communication system 100 performing high-speed communication of several tens of Mbps to several hundreds of Mbps, such as in-vehicle Ethernet, it is desirable that the capacitance value of the capacitor 117 be small. Parts are used. This is because when the stray capacitance of the capacitor 117 of the regulator circuits 114a and 114b is large, the signal quality is inferior and the immunity characteristic is degraded.

  As described above, in the first communication device 110, the connector 111 and the communication circuit 112 are connected via the common mode choke coil 113 and the pair of regulator circuits 114a and 114b.

  Further, according to the above configuration, the first communication device 110 communicates with the second communication device 120 using the differential signal through the cable 130 and supplies DC power to the second communication device 120. can do.

(Configuration of second communication device)
The second communication device 120 is another example of a differential communication device that performs communication using a differential signal on which direct current power is superimposed, and the connector 121, the communication circuit 122, the common mode choke coil 123, and the regulator circuit 124a. , 124b, and the power receiving circuit 125 and the like. In addition, since the second communication device 120 basically has the same configuration as the first communication device 110, the detailed description of the same configuration will be omitted here.

  The connector 121 corresponds to the connector 111 of the first communication device 110, and is an interface used to connect the second communication device 120 to the cable 130.

  The communication circuit 122 corresponds to the communication circuit 112 of the first communication device 110, and is a circuit that communicates with the first communication device 110 using a differential signal. The communication circuit 122 is connected to the connector 121 via the pair of signal lines 132a and 132b.

  The common mode choke coil 123 corresponds to the common mode choke coil 113 of the first communication device 110, and is provided on a pair of signal lines 132a and 132b connecting the communication circuit 122 and the connector 121. .

  The power receiving circuit (another example of the power circuit) 125 is a circuit that receives DC power superimposed on the pair of signal lines 131a and 131b. The power receiving circuit 125 receives DC power supplied to the cable 130 by the first communication device 110 and makes the power available to the second communication device 120.

  The regulator circuits 124 a and 124 b correspond to the regulator circuits 114 a and 114 b of the first communication device 110. The regulator circuits 124a and 124b are provided between the communication circuit 122 and the connector 121 corresponding to each of the pair of signal lines 132a and 132b transmitting differential signals, and the power receiving circuit 125 corresponds to the pair of signal lines 132a and 132b. It is used to receive DC power superimposed on 132b. Similar to the regulator circuits 114 a and 114 b of the first communication device 110, the pair of regulator circuits 124 a and 124 b includes a capacitor 117 and an inductor 118.

  Thus, in the second communication device 120, the connector 121 and the communication circuit 122 are connected via the common mode choke coil 123 and the pair of regulator circuits 124a and 124b.

  Further, according to the above configuration, the second communication device 120 communicates with the first communication device 110 using the differential signal via the cable 130, and the direct current supplied from the first communication device 110. Power can be used.

  As described above, in the differential communication system 100 according to the present embodiment, since DC power is superimposed on the differential signal, the power line between the first communication device 110 and the second communication device 120 may be omitted. Can.

  On the other hand, it is important for differential signals on which DC power is superimposed to be balanced. For example, when the circuit elements of the pair of regulator circuits 114a and 114b have variations, common mode noise is a differential signal component. And cause communication errors.

  Therefore, in the differential communication device (110, 120) according to the present embodiment, the common component is removed by the common mode choke coil (113, 123), and the regulator circuit (114a, 114b, 124a) is disposed in the place where the signal component is stabilized. , 124b). As a result, the differential communication device (110, 120) can achieve stabilization (balance) of the differential communication path, and can improve communication performance.

  As described above, according to the differential communication device (110, 120) according to the present embodiment, the immunity performance is maintained in the differential communication device (110, 120) performing communication using a differential signal on which direct current power is superimposed. While this, it becomes possible to superimpose DC power on the differential signal.

(Example of immunity characteristic)
Next, the immunity performance of the differential communication device according to the present embodiment will be described. Although the differential communication device is described here as the first communication device 110, the same applies to the second communication device 120.

  FIG. 2 is a diagram showing an example of the characteristics of the common mode choke coil according to an embodiment. This figure shows an image of an example of the performance of the common mode choke coil 113 using the Mix Mode S parameter.

  The Mix Mode S parameter is a parameter that indicates the pass / reflection characteristics of the common component / differential component, and Sdc21 converts the common component into a differential component when a differential signal is transmitted from one port to the other port. Indicates the amount of

  In the example of FIG. 2, it is shown that the amount by which the common component is converted to the differential component is reduced by about 30 dB to 40 dB by passing the common mode choke coil 113 in the frequency range of 10 MHz to 200 MHz. ing.

  FIG. 3 is a diagram illustrating an example of the influence of the addition of the regulator circuit according to an embodiment. FIG. 3A shows an example of Mix Mode S parameter Sdc (S11) in the case where there is no regulator circuit in the differential communication device for comparison in which the common mode choke coil 113 is not mounted, for example.

  Further, FIG. 3B shows an example of Mix Mode S parameter Sdc (S11) in the case of mounting a regulator circuit in a differential communication device for comparison in which the common mode choke coil 113 is not mounted, for example. .

  As described above, when the regulator circuit is mounted in the communication device, it is understood that the noise component in which the common component is converted into the differential component is increased as compared with the case where the regulator circuit is not mounted. This is because if there is a difference in impedance between each of the pair of communication paths performing differential communication and the ground potential, a difference occurs in the common mode voltage received on the receiving side, and the pair of communication performing differential communication This is because a voltage of noise is generated between the paths.

  FIG. 4 is a diagram illustrating an example of improvement of immunity performance according to an embodiment. FIG. 4 (a) shows, as in FIG. 3 (a), for example, the Mix Mode S parameter Sdc (S11) in the case where the regulator circuit is not provided in the comparative differential communication device in which the common mode choke coil 113 is not mounted. An example is shown.

  Further, FIG. 4 (b) is a block diagram of the first communication device 110 according to the present embodiment shown in FIG. 1, in which the pair of regulator circuits 114a and 114b are provided downstream of the common mode choke coil 113. An example of the Mode S parameter Sdc (S11) is shown.

  As described above, according to the first communication device 110 according to the present embodiment, the increase in the noise component converted from the common component to the differential component caused by mounting the regulator circuit is suppressed, and the regulator circuit It can be seen that the same immunity characteristics can be obtained as in the case without.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment, In the range of the summary of this invention described in the claim, various deformation | transformation and change are possible It is possible.

100 differential communication system 110 first communication device (an example of differential communication device)
120 Second Communication Device (Another Example of Differential Communication Device)
130 cable (external signal line)
111 connector 112 communication circuit 117 capacitor (capacitive element)
118 Inductor (Inductive element)
131a and 131b a pair of signal lines 132a and 132b a pair of signal lines 113 and 123 common mode choke coil 115 a feeder circuit (an example of a power circuit)
125 Power receiving circuit (another example of power circuit)
114a, 114b a pair of regulator circuits 124a, 124b a pair of regulator circuits

Claims (1)

A differential communication device that performs communication using a differential signal on which direct current power is superimposed,
A connector connected to an external signal line for transmitting the differential signal;
A common mode choke coil provided on a pair of signal lines connecting between the communication circuit performing the communication and the connector;
A power circuit for feeding or receiving the DC power superimposed on the differential signal;
A capacitive element provided between the communication circuit and the common mode choke coil corresponding to each of the pair of signal lines and connected between the communication circuit and the common mode choke coil, and the power circuit A pair of regulator circuits including an inductive element connected between the and the common mode choke coil;
, A differential communication device.

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