Patent Publication Number: US-2015061584-A1

Title: Communication system, charging control device, vehicle and power supply device

Description:
TECHNICAL FIELD 
     The present invention relates to: a communication system in which a control line for transmitting a control signal used for control of charging of an object to be charged and a reference potential line connected to a reference potential are used as media, and a communication signal different from the control signal is transmitted via the media to perform communication; a charging control device used in the communication system; a vehicle including the charging control device; and a power supply device including the charging control device. 
     BACKGROUND ART 
     In recent years, electric vehicles and hybrid vehicles are beginning to prevail, which include devices such as motors and batteries, and travel by driving the motors with power stored in the batteries. The electric vehicles charge their batteries with power supplied from external power supply devices. As for the hybrid vehicles, plug-in hybrid vehicles have been practically used, which allow their batteries to be charged by external power supply devices. The external power supply devices are power supply devices installed in ordinary houses or facilities such as commercial charging stations. When a power supply device supplies power to a vehicle, a plug at an end of a charging cable connected to the power supply device is connected to a power supply port which is provided in the vehicle as a power receiving connector. Then, power is supplied from the power supply device to the vehicle via a power supply line contained in the charging cable, and thereby the battery is charged. 
     Not only the power supply line but also other lines such as a grounding line, a control line, and the like are contained in the charging cable. The control line is a line used for transmission of a control signal such as a control pilot signal or the like used for control of power supply to the power storage device. By transmitting and receiving the control signal between the power supply device and the vehicle via the control line, various states are detected such as the connection state of the charging cable, whether charging is possible or not, the state of charging, and the like, and charging control is performed according to the detected states. 
     Further, for practical use of vehicles that need external power supply, such as electric vehicles and hybrid vehicles, a communication function is required, which allows a vehicle and a power supply device to transmit and receive information for power supply control, and communication information for management of the amount of power, accounting, or the like. 
     Thus, standardization of communication such as inband communication has been progressed, in which a communication signal is superposed on a control signal to be transmitted and received between a vehicle and a power supply device (refer to Non-Patent Literature 1, for example). 
       FIG. 6  is an illustrative diagram showing an exemplary configuration of a system standardization of which is in progress. In  FIG. 6 , reference numeral  1000  denotes a vehicle. When the vehicle  1000  is supplied with power from a power supply device  2000 , the vehicle  1000  is connected to the power supply device  2000  via a charging cable  3000 . The charging cable  3000  contains a pair of power supply lines  3001  and  3002  used for power supply, a grounding line  3003  which is a conducting wire for grounding, and a control line  3004  for transmitting a control signal such as a control pilot signal (CPLT) used for charging control. 
     An end of the charging cable  3000  is connected to the power supply device  2000  side, and a plug  3005  is provided on the other end of the charging cable  3000 . The plug  3005  is connected to a power receiving connector  1001  provided as a connection part at a power supply port on the vehicle  1000  side, and thereby power supply is enabled. 
     The power supply device  2000  includes a power supply section  2001  that supplies AC power, a charging control device  2002  that performs communication regarding charging control, a communication device  2003  that transmits and receives a communication signal, and a superposition/separation unit  2004  that performs superposition and separation of the communication signal on and from the grounding line  3003  and the control line  3004 . 
     The charging control device  2002  includes various elements such as a capacitor C 2 , a resistor R 2 , and the like and various circuits such as an oscillation circuit O and the like. The capacitor C 2  and the oscillation circuit O are connected to a ground potential. 
     The superposition/separation unit  2004  includes a first coil  2004   a  having both ends connected to the grounding line  3003  and the control line  3004 , and a second coil  2004   b  having both ends connected to the communication device  1005 . The first coil  2004   a  and the second coil  2004   b  are electromagnetically coupled to each other. 
     The superposition/separation unit  2004  superposes various communication signals on the grounding line  3003  and the control line  3004 , and separates superposed various communication signals. When the superposition/separation unit  2004  superposes various communication signals output from the communication device  2003 , and inputs separated various communication signals to the communication device  2003 , the communication device  2003  is allowed to perform communication. 
     The vehicle  1000  includes the power receiving connector  1001 , a battery  1002 , a charging device  1003  that charges the battery  1002 , a charging control device  1004  that performs communication regarding charging control, a communication device  1005  that transmits and receives communication signals, and a superposition/separation unit  1006  that performs superposition and separation of the communication signals on and from the grounding line  3003  and the control line  3004 . 
     The charging control device  1004  includes various elements such as a capacitor C 1 , a resistor R 1 , a diode Vd, and the like. The capacitor C 1  and the resistor R 2  are connected to the grounding potential. 
     The superposition/separation unit  1006  includes a first coil  1006   a  having both ends connected to the grounding line  3003  and the control line  3004 , and a second coil  1006   b  having both ends connected to the communication device  1005 . The first coil  1006   a  and the second coil  1006   b  are electromagnetically coupled to each other. 
     The superposition/separation unit  1006  superposes various communication signals on the grounding line  3003  and the control line  3004 , and separates superposed various communication signals. When the superposition/separation unit  1006  superposes various communication signals output from the communication device  1005 , and inputs separated various communication signals to the communication device  1005 , the communication device  1005  is allowed to perform communication. 
     CITATION LIST 
     Non Patent Literature 
     
         
         NON PATENT LITERATURE 1: “SURFACE VEHICLE RECOMMENDED PRACTICE”, J1772 JAN2010, Society of Automotive Engineers, Inc., October, 1996 (revised in January, 2010) 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     In the conventional system exemplified in  FIG. 6 , however, common mode noise generated in the grounding line  3003  and the control line  3004  may flow into the communication device  1005  or the communication device  2003  and cause abnormality such as false operation. 
       FIG. 7  is a circuit diagram showing an example of a simulation of common mode noise.  FIG. 7  shows an equivalent circuit for a BCI test executed as an evaluation test for common mode noise on the vehicle  1000  side of the system shown in  FIG. 6 . In the evaluation test such as the BCI test, common mode noise is applied from a probe as a noise generation source to the grounding line  3003  and the control line  3004 . In  FIG. 7 , reference numeral  4000  denotes a simulation noise source which is an equivalent circuit of a noise generation source using a probe. The simulation noise source  4000  applies in-phase common mode noises to the grounding line  3003  and the control line  3004 . 
     Voltages Vgnd and Vcplt applied as the common mode noises from the simulation noise source  4000  to the grounding line  3003  and the control line  3004  are originally in-phase signals having the same amplitude, and therefore, cancel out each other in the first coil  1006   a  of the superposition/separation unit  1006  and do not flow into the communication device  1005 . 
     However, in the charging control device  1004 , a difference occurs between the voltage Vgnd on the grounding line  3003  side and the voltage Vcplt on the control line  3004  due to the noise that flows out via the ground (GND), resulting in an imbalance state. The imbalance between the grounding line  3003  side and the control line  3004  side based on the circuit structure in the charging control device  1004  also leads to a difference in line impedance. As a result, the common mode noises applied to the grounding line  3003  and the control line  3004  change into normal mode noises. The normal mode noises do not cancel out each other in the first coil  1006   a  of the superposition/separation unit  1006 , and flows into the communication device  1005 , which may cause abnormality such as false operation. A similar situation may occur in the communication device  2003  on the power supply device  2000  side. 
     The present invention has been made in view of the above situation. A major object of the present invention is to provide a communication system, a charging control device, a vehicle, and a power supply device which suppress common mode noise by interposing a pair of induction elements in the control line and the grounding line. 
     Furthermore, another object of the present invention is to provide a communication system, a charging control device, a vehicle, and a power supply device which prevent common mode noise from changing into normal mode noise to eliminate adverse effects on a communication device and the like, by providing a pair of induction elements in front of the charging control device. 
     Solution to Problem 
     A communication system according to the present invention is a communication system in which a control line for transmitting a control signal used for control of charging of an object to be charged and a reference potential line connected to a reference potential are used as media, and a communication signal different from the control signal is transmitted via the media to perform communication. The communication system includes: a charging control device connected to the control line and the reference potential line, and configured to control charging in accordance with the control signal; a communication device connected to two branch lines branched from the control line and the reference potential line, respectively, and configured to perform communication by the communication signal; and a pair of induction elements interposed in the control line and the reference potential line. 
     In the communication system according to the present invention, the pair of induction elements is located between the charging control device and branch portions of the two branch lines. 
     In the communication system according to the present invention, the pair of induction elements is a common mode choke coil. 
     In the communication system according to the present invention, a power storage device as the object to be charged, the charging control device, the communication device, and the pair of induction elements are provided in a vehicle. 
     In the communication system according to the present invention, the vehicle includes a connector for connecting an external line to the control line and the reference potential line, and the pair of induction elements is provided in the connector. 
     In the communication system according to the present invention, the charging control device, the communication device, and the pair of induction elements are provided in a power supply device configured to supply power to the object to be charged. 
     A charging control device according to the present invention is a charging control device connected to a control line for transmitting a control signal used for control of charging of an object to be charged and to a reference potential line connected to a reference potential, and configured to control charging in accordance with the control signal. The charging control device includes a pair of induction elements connected to the control line and the reference potential line. 
     A vehicle according to the present invention includes: a power storage device; a charging control device connected to a control line for transmitting a control signal used for control of charging of the power storage device and to a reference potential line connected to a reference potential, and configured to control charging in accordance with the control signal; a communication device connected to two branch lines branched from the control line and the reference potential line, respectively, and configured to perform communication by transmitting a communication signal different from the control signal; and a pair of induction elements interposed in the control line and the reference potential line. 
     The vehicle according to the present invention includes a connector for connecting an external line to the control line and the reference potential line, and the pair of induction elements is provided in the connector. 
     A power supply device according to the present invention is configured to supply power to an object to be charged, and includes: a charging control device connected to a control line for transmitting a control signal used for control of charging of the object to be charged and to a reference potential line connected to a reference potential, and configured to control charging in accordance with the control signal; a communication device connected to two branch lines branched from the control line and the reference potential line, respectively, and configured to perform communication by transmitting a communication signal different from the control signal; and a pair of induction elements interposed in the control line and the reference potential line. 
     In the present invention, common mode noise is suppressed by providing the pair of induction elements having a high impedance for the common mode noise. 
     Particularly when the pair of induction elements is provided between the charging control device and branch portions of the two branch lines, common mode noise is prevented from changing into normal mode noise due to influence of a device such as the charging control device. 
     Advantageous Effects of Invention 
     In the present invention, the pair of induction elements has a high impedance for common mode noise, and therefore, prevents entry of the common mode noise, resulting in advantageous effects such as that the common mode noise can be suppressed. 
     Further, in the present invention, since the pair of induction elements has a high impedance for common mode noise, a voltage applied to the grounding line and a voltage applied to the control line are balanced. Therefore, the common mode noise is not changed into normal mode noise, and the voltages of signals applied as the common mode noise to the both ends of the coil cancel out each other. Accordingly, advantageous effects are obtained such as that the noise can be prevented from flowing into the communication device. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram showing an exemplary configuration of a communication system according to Embodiment 1 of the present invention. 
         FIG. 2  is a circuit diagram showing examples of a common mode choke coil and a low-pass filter used in the communication system according to Embodiment 1 of the present invention. 
         FIG. 3  is a circuit diagram showing an example of a simulation of common mode noise in the communication system according to Embodiment 1 of the present invention. 
         FIG. 4  is a diagram showing an exemplary configuration of a communication system according to Embodiment 2 of the present invention. 
         FIG. 5  is a diagram showing an exemplary configuration of a communication system according to Embodiment 3 of the present invention. 
         FIG. 6  is a diagram showing an exemplary configuration of a system, standardization of which is in progress. 
         FIG. 7  is a circuit diagram showing an example of a simulation of common mode noise. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, the present invention will be described in detail with reference to the drawings showing embodiments thereof. 
     Embodiment 1 
       FIG. 1  is a diagram showing an exemplary configuration of a communication system according to Embodiment 1 of the present invention.  FIG. 1  shows an example in which the communication system of the present invention is applied to a case in which a battery (power storage device)  10  included in a vehicle  1  such as an electric vehicle, a plug-in hybrid vehicle, or the like is supplied with power from a power supply device  2  such as a charging station. 
     The vehicle  1  and the power supply device  2  can be connected to each other by a charging cable  3 . The charging cable  3  contains a pair of power supply lines  31  and  32  used for power supply, a grounding line (reference potential line)  33  connected to a reference potential such as a ground potential, and a control line  34  for transmitting a control signal such as a control pilot signal (CPLT) used for charging control. An end of the charging cable  3  is connected to the power supply device  2  side, and a plug  30  is provided on the other end of the charging cable  3 . The plug  30  can be connected to a power receiving connector  11  provided as an in-vehicle power supply port serving as a connection site on the vehicle  1  side. When the plug  30  at the other end of the charging cable  3  is connected to the power receiving connector  11 , connection terminals provided at end portions of the power supply lines  31  and  32 , the grounding line  33 , and the control line  34  in the charging cable  3  come into contact with connection terminals provided in the power receiving connector  11 , whereby the circuit structure exemplarily shown in  FIG. 1  is realized. 
     The power supply lines  31  and  32  are AC lines to which AC voltage is applied. The control line  34  is a signal line through which a control signal such as a control pilot signal is transmitted and received, and charging control is performed based on a control signal transmitted and received when the power supply device  2  and a charging control device  13  are connected to each other. In addition, the grounding line  33  and the control line  34  can be also used as media for transmitting information for performing vehicle authentication, charging management, accounting management, and the like, and other various kinds of information. That is, the vehicle  1  and the power supply device  2  can communicate with each other by superposing and separating a communication signal on and from the grounding line  33  and the control line  34  as media. 
     The power supply device  2  includes a power supply device  20  that supplies AC power, a charging control device  21  that performs communication regarding charging control, a communication device  22  that transmits and receives a communication signal, a superposition/separation unit  23  that superposes and separates the communication signal on and from the grounding line  33  and the control line  34 , a common mode choke coil  24  using a pair of induction elements, and a low-pass filter  25  that blocks the communication signal. 
     One ends of the power supply lines  31  and  32  and the grounding line  33  are connected to the power supply section  20 . One end of the control line  34  and the grounding line  33  are connected to the charging control device  21 . Lines inside the power supply device  2  are internal conducting wires that act as extended lines connected to the power supply lines  31  and  32 , the grounding line  33 , and the control line  34  which are contained in the charging cable  3  provided outside the power supply device  2 . However, in the following description, for convenience sake, the lines inside the power supply device  2 , including the extended line portions provided as the internal conducting wires, will be described as the power supply lines  31  and  32 , the grounding line  33 , and the control line  34 . 
     The charging control device  21  is, for example, an output-side circuit complying with the international standard regarding charging control, and performs charging control in various states such as confirmation of connection, start of energization, and the like by transmitting and receiving a control signal such as a control pilot signal. 
     The charging control device  21  includes various elements such as a capacitor C 2 , a resistor R 2 , and the like, and various circuits such as an oscillation circuit O and the like. The parameters of the various elements such as the capacitor C 2  and the resistor R 2  are appropriately designed in view of the frequency band of the control signal to be transmitted and received, and the like. For example, when a control pilot signal having a rectangular wave of 1 kHz is used as a control signal, a capacitor C 2  of 2.2 nF and a resistor R 2  of 1.0 kΩ are used. 
     The communication device  22  is connected to a branch line  35   a  branched from the grounding line  33  and a branch line  35   b  branched from the control line  34  via the superposition/separation unit  23 , and transmits and receives the communication signal by using the grounding line  33  and the control line  34  as media. 
     The superposition/separation unit  23  is connected to the branch line  35   a  branched from the grounding line  33  and the branch line  35   b  branched from the control line  34  via coupling capacitors. Each coupling capacitor has a high impedance for the control signal, and a low impedance for the communication signal. As an example of the coupling capacitor, a capacitor having a capacitance of 1 nF is used. 
     The superposition/separation unit  23  is a circuit such as a coupling transformer (an electromagnetic guidance type signal converter) including a first coil  231  having both ends connected to the grounding line  33  and the control line  34  via the respective branch lines  35   a  and  35   b , and a second coil  232  electromagnetically coupled to the first coil  231 . The second coil  232  is connected to the communication device  22 . 
     The superposition/separation unit  23  superposes various communication signals on the grounding line  33  and the control line  34 , and separates superposed various communication signals. When the superposition/separation unit  23  superposes various communication signals output from the communication device  22 , and inputs separated various communication signals to the communication device  22 , the communication device  22  is allowed to perform communication. 
     Each communication signal is transmitted and received as an electromagnetic wave superposed on carriers (subcarriers). As for the frequency bands used for the carriers regarding the communication signal, a frequency band ranging from several 10 kHz to several 100 kHz, e.g., from 30 kHz to 450 kHz, is used for low-speed communication, and a frequency band ranging from several MHz to several 10 MHz, e.g., from 2 MHz to 30 MHz, is used for high-speed communication. Since the control signal is output from an oscillator of 1 kHz, the control signal is a signal of a lower frequency than the communication signal. 
     The common mode choke coil  24  is interposed in the grounding line  33  and the control line  34 , and is located between the charging control device  21 , and branch portions  35   a   1  and  35   b   1  of the two branch lines  35   a  and  35   b  connected to the communication device  22  via the superposition/separation unit  23 . The common mode choke coil  24  has a high impedance for common mode noise generated in the grounding line  33  and the control line  34 . 
     The low-pass filter  25  is interposed in the control line  34 . The low-pass filter  25  acts as a blocking section that transmits signals in a frequency band lower than a predetermined frequency, e.g., a signal in a frequency band used for the control signal, and blocks high-frequency communication signals. 
     In  FIG. 1 , the low-pass filter  25  is located between the charging control device  21  and the common mode choke coil  24 . However, the common mode choke coil  24  may be located between the charging control device  21  and the low-pass filter  25 . 
     Further, in  FIG. 1 , the charging control device  21 , the common mode choke coil  24 , and the low-pass filter  25  are shown as separated components. However, the charging control device  21  may include the common mode choke coil  24  and the low-pass filter  25 . For example, the common mode choke coil  24  and the low-pass filter  25  may be integrated with each other inside or outside the charging control device  21 . 
     The vehicle  1  includes, in addition to the battery  10  and the power receiving connector  11 , a charging device  12  that charges the battery, the charging control device  13  that performs communication regarding charging control, a communication device  14  that transmits and receives a communication signal, a superposition/separation unit  15  that superposes and separates the communication signal on and from the grounding line  33  and the control line  34 , a common mode choke coil  16  using a pair of induction elements, and a low-pass filter  17  that blocks the communication signal. 
     When the plug of the charging cable  3  is connected to the power receiving connector  11  of the vehicle  1 , connection terminals provided at the other ends of the power supply lines  31  and  32 , the other end of the grounding line  33 , and the other end of the control line  34 , which are contained in the charging cable  3 , are connected to the connection terminals provided in the power receiving connector  11 . 
     The power receiving connector  11  includes internal lines connected to the power supply lines  31  and  32 , the grounding line  33 , and the control line  34  via the connection terminals. The other ends of the internal lines connected to the power supply lines  31  and  32  are connected to the charging device  12  via AC lines provided inside the vehicle  1 , whereby the battery  10  is charged by the charging device  12 . The other end of the internal line connected to the grounding line  33  is connected to the charging device  12 , the charging control device  13 , and the battery  10  via an internal line in the vehicle  1  or a body earth. The other end of the internal line connected to the control line  34  is connected to the charging control device  13  via an extended line provided as an internal line in the vehicle  1 . In the following description, the respective internal lines, including the AC lines and the extended lines, will be described as the power supply lines  31  and  32 , the grounding line  33 , and the control line  34 . 
     The charging control device  13  is, for example, an input-side circuit complying with the international standard regarding charging control, and performs charging control in various states such as confirmation of connection, start of energization, and the like, by transmitting and receiving a control signal such as a control pilot signal, when the charging control device  13  becomes communicable with the charging control device  21  of the power supply device  2 . 
     The charging control device  13  includes various elements such as a capacitor C 1 , a resistor R 1 , a diode Vd, and the like. The parameters of the various elements such as the capacitor C 1  and the resistor R 1  are appropriately designed in view of the frequency band regarding the control signal to be transmitted and received, or the like. For example, when a control pilot signal having a rectangular wave of 1 kHz is used as a control signal, a capacitor C 2  of 1.8 nF and a resistor R 2  of 2.74 kΩ are used. 
     The communication device  14  is connected to a branch line  36   a  branched from the grounding line  33  and a branch line  36   b  branched from the control line  34  via the superposition/separation unit  15 , and transmits and receives the communication signal by using the grounding line  33  and the control line  34  as media. 
     The superposition/separation unit  15  is connected to the branch line  36   a  branched from the grounding line  33  and the branch line  36   b  branched from the control line  34  via coupling capacitors. Each coupling capacitor has a high impedance for the control signal, and a low impedance for the communication signal. As an example of the coupling capacitor, a capacitor having a capacitance of 1 nF is used. 
     The superposition/separation unit  15  is a circuit such as a coupling transformer including a first coil  151  having both ends connected to the grounding line  33  and the control line  34  via the respective branch lines  36   a  and  36   b , and a second coil  152  electromagnetically coupled to the first coil  151 . The second coil  152  is connected to the communication device  14 . 
     The superposition/separation unit  15  superposes various communication signals on the grounding line  33  and the control line  34 , and separates superposed various communication signals. When the superposition/separation unit  15  superposes various communication signals output from the communication device  14 , and inputs separated various communication signals to the communication device  14 , the communication device  14  is allowed to perform communication. 
     The common mode choke coil  16  is interposed in the grounding line  33  and the control line  34 , and is located between the charging control device  13 , and branch portions  36   a   1  and  36   b   1  of the two branch lines  36   a  and  36   b  connected to the communication device  14  via the superposition/separation unit  16 . The common mode choke coil  16  has a high impedance for common mode noise generated in the grounding line  33  and the control line  34 . 
     The low-pass filter  17  is interposed in the control line  34 . The low-pass filter  17  acts as a blocking section that transmits signals in a frequency band lower than a predetermined frequency, e.g., a signal in a frequency band used for the control signal, and blocks high-frequency communication signals. 
     In  FIG. 1 , the low-pass filter  17  is positioned between the charging control device  13  and the common mode choke coil  16 . However, the common mode choke coil  16  may be located between the charging control device  13  and the low-pass filter  17 . 
     Further, in  FIG. 1 , the charging control device  13 , the common mode choke coil  16 , and the low-pass filter  17  are shown as separated components. However, the charging control device  13  may include the common mode choke coil  16  and the low-pass filter  17 . For example, the common mode choke coil  16  and the low-pass filter  17  may be integrated with each other inside or outside the charging control device  13 . 
     By configuring the communication system of the present invention as shown in  FIG. 1 , a loop circuit for transmitting a communication signal is formed by the superposition/separation unit  15 , the grounding line  33 , the control line  34 , the superposition/separation unit  23 , and other lines, elements, and circuits. Thereby, inband communication in which a communication signal is superposed on the grounding line  33  and the control line  34  is realized between the communication device  14  in the vehicle  1  and the communication device  22  in the power supply device  2 . 
       FIG. 2  is a circuit diagram showing examples of the common mode choke coils  16  and  24  and the low-pass filters  17  and  25  used in the communication system according to Embodiment 1 of the present invention.  FIG. 2  shows the common mode choke coil  16 , the low-pass filter  17 , and the charging control device  13  included in the vehicle  1  shown in  FIG. 1 . Since the arrangement of the common mode choke coil  24 , the low-pass filter  25 , and the charging control device  21  included in the power supply device  2  is similar to the arrangement shown in  FIG. 2 , these components will also be described with reference to  FIG. 2  in which the reference numerals thereof are also shown. 
     The common mode choke coil  16  ( 24 ) is configured using a pair of induction elements or an equivalent circuit thereof, and has a high impedance for common mode noise while having a low impedance for signals such as the communication signal, the control signal, and the like. 
     The low-pass filter  17  ( 25 ) is, as shown in  FIG. 2 , configured as a circuit in which, for example, a coil having an inductance of 1.5 mH and a resistor of 1.0 kΩ are arranged in parallel, or as an equivalent circuit thereof. The low-pass filter may be configured using another circuit as long as similar characteristics can be achieved. In addition, the values of the elements used in the low-pass filter are merely examples, and elements of other values may be used. 
       FIG. 3  is a circuit diagram showing an example of a simulation of common mode noise in the communication system according to Embodiment 1 of the present invention.  FIG. 3  shows an equivalent circuit for a BCI test executed as an evaluation test for common mode noise on the vehicle  1  side of the communication system shown in  FIG. 1 . In the evaluation test such as the BCI test, common mode noise is applied from a probe as a noise generation source to the grounding line  33  and the control line  34 . In  FIG. 3 , reference numeral  4  denotes a simulation noise source which is an equivalent circuit of a noise generation source using a probe, and the simulation noise source  4  applies in-phase common mode noises to the grounding line  33  and the control line  34 . 
     Voltages Vgnd and Vcplt applied as the common mode noises from the simulation noise source  4  to the grounding line  33  and the control line  34  are in-phase signals having the same amplitude. Since the common mode choke coil  16  has a high impedance for the common mode noises, the voltages Vgnd and Vcplt applied to the grounding line  33  and the control line  34  are not likely to be adversely affected by a line impedance due to the circuit in the charging control device  13 . Then, the common mode noises do not flow into the charging control device  13 , but flow from the both ends of the first coil  151  into the superposition/separation unit  15 , as in-phase signals having substantially the same amplitude. In other words, the common mode noises are applied to the superposition/separation unit  15  without being changed into normal mode noises. The common mode noises flowing from the both ends of the first coil  151  are the in-phase signals having substantially the same amplitude, and therefore, cancel out each other in the first coil  151  and do not flow into the communication device  14 . Accordingly, it is possible to prevent occurrence of abnormality such as false operation due to flow of noise into the communication device  14 . 
     A situation similar to above occurs on the power supply device  2  side, and it is possible to prevent occurrence of abnormality such as false operation due to flow of noise into the communication device  22 . 
     Embodiment 2 
     In Embodiment 2, a common mode choke coil is added to the power receiving connector of Embodiment 1. In the following description, as for the components identical to those of Embodiment 1, Embodiment 1 is supposed to be referred to, and therefore, description thereof will be omitted. 
       FIG. 4  is a diagram showing an exemplary configuration of a communication system according to Embodiment 2 of the present invention.  FIG. 4  shows a configuration obtained by adding a common mode choke coil  18  to the communication system according to Embodiment 1 shown in  FIG. 1 . In the exemplary configuration shown in  FIG. 4 , the common mode choke coil  18  using a pair of induction elements is incorporated in a casing of the power receiving connector  11 . In the power receiving connector  11 , the common mode choke coil  18  is interposed in the internal lines connected to the grounding line  33  and the control line  34 . 
     The common mode choke coil  18  incorporated in the power receiving connector  11  has a high impedance for common mode noise generated in the grounding line  33  and the control line  34 , and therefore, resistance to the common mode noise can be enhanced as compared to Embodiment 1. The common mode choke coil  18  may be provided outside the casing of the power receiving connector  11  as long as it is integrated with the power receiving connector  11 . 
     By configuring the communication system of the present invention as shown in  FIG. 4 , a loop circuit for transmitting a communication signal is formed by the superposition/separation unit  15 , the grounding line  33 , the control line  34 , the superposition/separation unit  23 , and other lines, elements, and circuits. Thereby, inband communication in which the communication signal is superposed on the grounding line  33  and the control line  34  is realized between the communication device  14  in the vehicle  1  and the communication device  22  in the power supply device  2 . 
     Embodiment 3 
     Embodiment 3 provides a configuration in which the common mode choke coil located between the charging control device and the branch portions  36   a   1  and  36   b   1  of the two branch lines  36   a  and  36   b  connected to the communication device via the superposition/separation unit, is omitted from Embodiment 2. In the following description, as for the components identical to those of Embodiment 1 or 2, Embodiment 1 or 2 is supposed to be referred to, and therefore, description thereof will be omitted. 
       FIG. 5  is a diagram showing an exemplary configuration of a communication system according to Embodiment 3 of the present invention.  FIG. 5  shows a configuration obtained by omitting the common mode choke coil  16  in the communication system of Embodiment 2 shown in  FIG. 4 . In the exemplary configuration of  FIG. 5 , a common mode choke coil  18  using a pair of induction elements is incorporated in the casing of the power receiving connector  11 . In the power receiving connector  11 , the common mode choke coil  18  is interposed in the internal lines connected to the grounding line  33  and the control line  34 . 
     The common mode choke coil  18  incorporated in the power receiving connector  11  has a high impedance for common mode noise generated in the grounding line  33  and the control line  34 , and therefore, suppresses the common mode noise that flows into the vehicle  1 . In addition, the common mode choke coil  18  prevents the common mode noise generated in the device in the vehicle  1  from flowing out of the vehicle  1 . The common mode choke coil  18  may be provided outside the casing of the power receiving connector  11  as long as it is integrated with the power receiving connector  11 . In addition, the low-pass filter  17  may be integrated with the power receiving connector  11 . 
     By configuring the communication system of the present invention as shown in  FIG. 5 , a loop circuit for transmitting a communication signal is formed by the superposition/separation unit  15 , the grounding line  33 , the control line  34 , the superposition/separation unit  23 , and other lines, elements, and circuits. Thereby, inband communication in which the communication signal is superposed on the grounding line  33  and the control line  34  is realized between the communication device  14  in the vehicle  1  and the communication device  22  in the power supply device  2 . 
     Embodiments 1 to 3 are merely disclosure of part of infinite number of examples of the present invention, and can be appropriately designed by adding various factors such as the purpose, usage, mode, and the like. For example, in the above embodiments, the communication device is connected to the branch lines branched from the control line and the grounding line via the superposition/separation unit. However, the superposition/separation unit or the like may be interposed in the control line or the like, and the communication device or the like may be connected to the interposed superposition/separation unit or the like. Further, in the embodiments of the present invention, the common mode choke coil is provided on both the power supply device side and the vehicle side. However, the common mode choke coil may be provided on one of the power supply device side and the vehicle side. Further, the superposition/separation unit and/or the coupling capacitors provided on the respective branch lines may be incorporated in the communication device. 
     Further, the present invention is also applicable to, for example, a system regarding charging of an object to be charged other than batteries included in vehicles. Thus, the present invention can be developed into various modes. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  vehicle 
               10  battery (power storage device) 
               11  power receiving connector 
               12  charging device 
               13  charging control device 
               14  communication device 
               15  superposition/separation unit 
               151  first coil 
               152  second coil 
               16  common mode choke coil (a pair of dielectric elements) 
               17  low-pass filter 
               18  common mode choke coil (a pair of induction elements) 
               2  power supply device 
               20  power supply device 
               21  charging control device 
               22  communication device 
               23  superposition/separation unit 
               24  common mode choke coil (a pair of dielectric elements) 
               25  low-pass filter 
               3  charging cable 
               31 ,  32  power supply line 
               33  grounding line 
               34  control line