Abstract:
It is an object of the present invention to provide a power supplying apparatus, a power receiving apparatus, an electrical vehicle, a charging system, and a charging method, the power feeding apparatus improving reliability by suppressing any decrease in charging efficiency and making charging control communication more resistant to high-frequency noise of a switching element. A power supplying apparatus for feeding power to an external apparatus, wherein the power supplying apparatus is characterized in having a power conversion unit, a power supplying unit, a control unit, and a communication unit. The power conversion unit includes a for power conversion switching element capable of changing the switching waveform. The power supplying unit supplies power to the external apparatus, the power being generated in the power conversion unit. The communication unit communicates with the external apparatus. The control unit conducts a control so as to adjust the switching waveform of the switching element in the power conversion unit during a period in which the communication unit communicates with the external apparatus.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a power feeding apparatus, a power receiving apparatus, an electrical vehicle, a charging system, and a charging method. 
       BACKGROUND ART 
       [0002]    As a background art of the present technical field, JP-A-6-343205 (Patent Literature 1) is known. JP-A-6-343205 describes “a battery controller that determines whether communication of charging information is necessary or unnecessary and a charger controller that stops charging when it is determined that the communication of the charging information is necessary and performs the charging when it is determined that the communication is unnecessary are included in a charging apparatus of an electrical vehicle charging a vehicle-mounted battery on the basis of the charging information exchanged between a charger and the vehicle-mounted battery, to prevent erroneous transmission of information at the time of communicating the charging information between the battery and the charger,” (refer to Abstract). 
       CITATION LIST 
     Patent Literature 
       [0003]    Patent Literature 1: JP-A-6-343205 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0004]    In Patent Literature 1, a structure of the charging apparatus of the electrical vehicle to prevent the erroneous transmission of the information at the time of communicating the charging information between the battery and the charger is described. However, the charging apparatus of the electrical vehicle of Patent Literature 1 needs to stop the charging when it is determined that the communication of the charging information is necessary. In addition, charging efficiency is degraded by stopping the charging to suppress communication interference and a time needed until the charging ends increases, which results in decreasing convenience to a user. 
         [0005]    Accordingly, an object of the present invention is to provide a power feeding apparatus, a power receiving apparatus, an electrical vehicle, a charging system, and a charging method that can suppress charging efficiency from being degraded, improve tolerance of communication for charging control against harmonic noise of a switching element, and improve reliability. 
       Solution to Problem 
       [0006]    In order to resolve the above problems, configurations described in CLAIMS are adopted. 
         [0007]    The present application includes a plurality of means for resolving the above problems. For example, there is provided a power feeding apparatus for feeding power to an external apparatus. The power feeding apparatus includes a power converting unit that has a switching element for power conversion capable of changing a switching waveform; a power feeding unit that supplies power generated by the power converting unit to the external apparatus; a control unit; and a communication unit that performs communication with the external apparatus. Control is performed by the control unit such that the switching waveform of the switching element in the power converting unit is adjusted, in a period in which the communication unit performs communication with the external apparatus. 
       Advantageous Effects of Invention 
       [0008]    According to the present invention, a power feeding apparatus, a power receiving apparatus, an electrical vehicle, a charging system, and a charging method that can suppress charging efficiency from being degraded, improve tolerance of communication for charging control against harmonic noise of a switching element, and improve reliability can be provided. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0009]      FIG. 1  is an exemplary configuration diagram of a wireless charging system on which a power feeding apparatus and a power receiving apparatus according to an embodiment of the present invention are mounted. 
           [0010]      FIG. 2  is an exemplary configuration diagram of a power converting unit in the power feeding apparatus according to the embodiment of the present invention. 
           [0011]      FIG. 3  is a diagram illustrating a relation of a PWM control signal and a transition time of a time waveform of a switching signal in a DC-AC inverter. 
           [0012]      FIG. 4  is an exemplary configuration diagram of a power converting unit in the power receiving apparatus according to the embodiment of the present invention. 
           [0013]      FIG. 5  is an operation sequence diagram of the wireless charging system. 
           [0014]      FIG. 6  is an operation sequence diagram to search switching signal transition time setting to suppress occurrence of interference to communication for charging control. 
           [0015]      FIG. 7  is an operation sequence diagram to change switching transition time setting to suppress occurrence of interference to communication for charging control. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0016]    Hereinafter, embodiments will be described using the drawings. In the drawings, the same reference numeral denotes the same or equivalent portion. In addition, the present invention is not limited to examples illustrated in the drawings. 
       First Embodiment 
       [0017]    In this embodiment, an example of a wireless charging system that performs charging for a storage battery mounted on an electrical vehicle by wireless power feeding capable of feeding power from a charging device to the electrical vehicle without connection by a connector will be described. 
         [0018]      FIG. 1  is an exemplary configuration diagram of a wireless charging system on which a power converting device according to an embodiment of the present invention is mounted. In  FIG. 1 , a wireless charging system  1  includes a power feeding apparatus  10  that supplies power to the outside and an electrical vehicle  2  having a power receiving apparatus  20  that receives power from the outside. In this embodiment, the charging system having the power feeding apparatus and the power receiving apparatus will be described using an operation of the case in which the power feeding apparatus  10  for the electrical vehicle is arranged in a charging station or a parking lot of a public facility and the power receiving apparatus  20  receives power supply from the power feeding apparatus  10  and charges the electrical vehicle  2  as an example. 
         [0019]    The power feeding apparatus  10  includes a power feeding side power converting unit  11  including a power converting device, a wireless power feeding unit  12 , a power feeding control unit  13 , a power feeding side communication unit  14 , an antenna  15 , and a storage unit  16 . In addition, the power feeding control unit  13  includes a communication period determining unit  131  and an error rate determining unit  132 . 
         [0020]    Meanwhile, the electrical vehicle  2  includes the power receiving apparatus  20 , a driving system power converting unit  30 , a motor  40 , a driver  50 , and a storage battery  60 . 
         [0021]    In addition, the power receiving apparatus  20  includes a wireless power receiving unit  21 , a power receiving side power converting unit  22  including a power converting device, a power receiving side communication unit  23 , an antenna  24 , a power receiving control unit  25 , and a storage unit  26 . In addition, the power receiving control unit  25  includes a communication period determining unit  251  and an error rate determining unit  252   
         [0022]    Each of the wireless power feeding unit  12  in the power feeding apparatus  10  and the wireless power receiving unit  21  in the power receiving apparatus  20  of the electrical vehicle  2  is formed by a coil and power is transmitted by mutual induction when the individual coils face in an axial direction. Hereinafter, an operation of the case of using wireless power transmission of an electromagnetic induction method will be described. 
         [0023]    First, the power feeding side power converting unit  11  in the power feeding apparatus  10  converts a frequency for alternating-current power of system power supplied from the outside, for example, three-phase alternating-current power 200 V by power conversion using a switching element, generates a high frequency signal, and supplies the high frequency signal to the wireless power feeding unit  12 . 
         [0024]    Next, the wireless power feeding unit  12  in the power feeding apparatus  10  generates a magnetic flux in the axial direction of the coil by the high frequency signal supplied from the power feeding side power converting unit  11 . Meanwhile, in the wireless power receiving unit  21  in the power receiving apparatus  20  of the electrical vehicle  2 , a high frequency signal is generated in the power receiving coil by induced electromotive force based on mutual induction with the magnetic flux generated by the power feeding coil of the wireless power feeding unit  12  and the high frequency signal is supplied to the power receiving side power converting unit  22 . 
         [0025]    The power receiving side power converting unit  22  generates direct-current power from the supplied high frequency signal by the power conversion using the switching element and supplies the direct-current power to the storage battery  60 . The storage battery  60  holds the direct-current power supplied from the power receiving side power converting unit  22  in the storage battery. Meanwhile, when the electrical vehicle  2  travels, a motor driving signal is generated by the driving system power converting unit  30  using the direct-current power held in the storage battery  60  and the motor  40  is driven. In addition, the motor  40  rotates the driver  50  such as wheels and travels the electrical vehicle. 
         [0026]    The power feeding control unit  13  generates a current command value of the high frequency signal output from the power feeding side power converting unit  11  in the power feeding apparatus  10  and transition time setting regarding an internal operation, supplies the current command value and the transition time setting to the power feeding side power converting unit  11 , and performs control. In addition, the power receiving control unit  25  sets an voltage command value of the direct-current power output from the power receiving side power converting unit  22  in the power receiving apparatus  20  of the electrical vehicle  2  and transition time setting regarding an internal operation, supplies the voltage command value and the transition time setting to the power receiving side power converting unit  22 , and performs control. Here, the transition time is a rising or falling time of a time waveform of a control signal. 
         [0027]    Next, a communication interface of the power feeding apparatus  10  to control an operation from a charging start to a charging end and the power receiving apparatus  20  of the electrical vehicle  2  will be described. In  FIG. 1 , the power feeding control unit  13  of the power feeding apparatus  10  and the power receiving control unit  25  of the power receiving apparatus  20  transmit and receive a start request or a stop request of a charging operation, storage battery information of the electrical vehicle  2  (a battery capacity, a maximum charging time, and a current command value at the time of charging based on a battery state), and information of charger information (a maximum current) of the power feeding apparatus  10  by wireless communication through the power feeding side communication unit  14  and the power receiving side communication unit  23 . 
         [0028]    When information is transmitted from the power feeding apparatus  10  to the power receiving apparatus  20  of the electrical vehicle  2 , the power feeding control unit  13  of the power feeding apparatus  10  generates data to be transmitted to the power receiving apparatus  20  of the electrical vehicle  2  and supplies the data to the power feeding side communication unit  14 . The power feeding side communication unit  14  executes encoding and modulation processing on the supplied data and transmits a high frequency signal (RF signal) from the antenna  15 . 
         [0029]    Meanwhile, the power receiving side communication unit  23  of the power receiving apparatus  20  amplifies or attenuates the RF signal received by the antenna  24  of the power receiving apparatus  20  such that a signal level of the RF signal becomes a desired signal level, executes frequency conversion and demodulation and decoding processing, and supplies the received data to the power receiving control unit  25 . At this time, in the power receiving side communication unit  23  of the power receiving apparatus  20 , auto gain control (AGC) is performed such that the signal level of the RF signal received by the antenna  24  becomes the desired signal level and it can be determined whether the RF signal is transmitted from the antenna  15  of the power feeding apparatus  10  and is received by the antenna  24  of the power receiving apparatus  20 , by a voltage value change of an AGC control signal. The power receiving control unit  25  supplies the AGC control signal to the communication period determining unit  251  and it is determined by the communication period determining unit  251  whether communication is performed. 
         [0030]    In addition, the power receiving side communication unit  23  detects an error bit number of the demodulated and decoded received data in one data packet and supplies the error bit number to the error rate determining unit  252  of the power receiving control unit  25 . The error rate determining unit  252  calculates a received data error rate from the supplied error bit number and the reception number of times of data managed by the power receiving control unit  25 . 
         [0031]    Next, the case in which information is transmitted from the power receiving control unit  25  of the power receiving apparatus  20  to the power feeding apparatus  10  will be described At this time, the power receiving control unit  25  of the power receiving apparatus  20  generates data to be transmitted to the power feeding apparatus  10  and supplies the data to the power receiving side communication unit  23  The power receiving side communication unit  23  executes encoding and modulation processing on the supplied data and transmits an RE signal from the antenna  24 . 
         [0032]    Meanwhile, the power feeding side communication unit  14  of the power feeding apparatus  10  amplifies or attenuates the RF signal received by the antenna  15  of the power feeding apparatus  1   0  such that a signal level of the RE signal becomes a desired signal level, executes frequency conversion and demodulation and decoding processing, and supplies the received data to the power feeding control unit  13 . At this time, in the power feeding side communication unit  14  of the power feeding apparatus  10 , the auto gain control (AGC) is performed such that the signal level of the RE signal received by the antenna  15  becomes the desired signal level and it can be determined whether the RF signal is transmitted from the antenna  24  of the power receiving apparatus  20  and is received by the antenna  15  of the power feeding apparatus  10 , by a voltage value change of an AGC control signal. The power feeding control unit  13  supplies the AGC control signal to the communication period determining unit  131  of the power feeding control unit  13  and it is determined by the communication period determining unit  251  whether communication is performed. 
         [0033]    In addition, the power feeding side communication unit  14  detects an error bit number of the demodulated and decoded received data in one data packet and supplies the error bit number to the error rate determining unit  132  of the power feeding control unit  13 . The error rate determining unit  132  calculates a received data error rate from the supplied error bit number and the reception number of times of data managed by the power feeding control unit  13 . 
         [0034]    The power feeding control unit  13  of the power feeding apparatus  10  of  FIG. 1  can store information such as the current command value and the transition time setting set to the power feeding side power converting unit  11 , the error bit number or the reception error rate acquired by the error rate determining unit  132 , and a mid-communication transition time fixation flag in the storage unit  16  and call the information. The storage unit  16  is a non-volatile storage unit and holds the information even when power is not supplied. 
         [0035]    The power receiving control unit  25  of the power receiving apparatus  20  of  FIG. 1  can store information such as the current command value and the transition time setting set to the power receiving side power converting unit  22 , the error bit number or the reception error rate acquired by the error rate determining unit  252 , and a mid-communication transition time fixation flag in the storage unit  26  and call the information. The storage unit  26  is a non-volatile storage unit and holds the information even when power is not supplied. 
         [0036]    Next, a configuration of the power feeding side power converting unit  11  in the power feeding apparatus  10  will be described using  FIG. 2 .  FIG. 2  is an exemplary configuration diagram of the power converting unit in the power feeding apparatus according to the embodiment of the present invention. In  FIG. 2 , the power feeding side power converting unit  11  includes a rectifier  111 , a DC-AC inverter  112 , a current detecting unit  113 , a gate driver  114 , and a PWM control signal generating unit  115 . 
         [0037]    In  FIG. 2 , the rectifier  111  of the power feeding side power converting unit  11  generates direct-current power from alternating-current power of system power supplied from the outside, for example, three-phase alternating-current power 200 V by rectification and smoothing by a diode and supplies the direct-current power to the DC-AC inverter  112 . The DC-AC inverter  112  is a switching element for power conversion and converts the supplied direct-current power into an alternating-current signal of a frequency suitable for wireless power transmission, for example, 10 kHz to 100 kHz by an inverter circuit and supplies the alternating-current signal to the wireless power feeding unit  12  through the current detecting unit  113  In the current detecting unit  113 , a current value of a signal used for the wireless power transmission is detected and the detected current value is supplied to the PWM control signal generating unit  115 . 
         [0038]    The alternating-current power of the system power supplied from the outside is not limited to the three-phase alternating-current power 200 V and various alternating-current powers such as single-phase alternating-current power 200 V and single-phase alternating-current power 100 V are assumed. A rectification circuit used by the rectifier  111  is configured according to a type of the alternating-current power. As the frequency of the alternating-current signal generated by the DC-AC inverter  112 , 10 kHz to 100 kHz are exemplified. However, the frequency is not limited thereto. 
         [0039]    In  FIG. 2 , the PWM control signal generating unit  115  compares the current command value supplied from the power feeding control unit  13  and the current value supplied from the current detecting unit  113 , generates a PWM control signal such that the current value supplied from the current detecting unit  113  is matched with the current command value supplied from the power feeding control unit  13 , and supplies the PWM control signal to the gate driver  114 . 
         [0040]    The gate driver  114  switches gate resistance of the switching element, on the basis of the transition time setting supplied from the power feeding control unit  13 , and controls a transition time of a rising waveform and a falling waveform of a time waveform of a switching signal in the DC-AC inverter  112   
         [0041]    A relation of the PWM control signal generated by the PWM control signal generating unit  115  and the time waveform of the switching signal output from the DC-AC inverter  112  to be switched by the transition time setting will be described using  FIG. 3 . 
         [0042]      FIG. 3  is a diagram illustrating the relation of the PWM control signal and the transition time of the switching waveform in the DC-AC inverter. In  FIG. 3 , (a) illustrates an example of a waveform of the PWM control signal generated in the PWM control signal generating unit  115  in  FIG. 2  and a pulse width is controlled according to a waveform of an alternating-current signal to be output by the power feeding side power converting unit  1  ON-OFF of the switching element of the DC-AC converter  112  is controlled on the basis of the PWM control signal and switching waveforms illustrated in (b) to (d) are generated. 
         [0043]    Here, the transition time setting has command values (τ[0], τ[1] . . . τ[Nmax]) of (Nmax+1) types and a transition time of a rising waveform and a falling waveform is shortest in the case of τ[0], the transition time increases in order of τ[1] and τ[2], and the transition time is longest in the case of τ[Nmax]. In  FIG. 3 , (b) illustrates a time waveform in the case in which the transition time setting is τ[0], (c) illustrates a time waveform in the case in which the transition time setting is τ[1], and (d) illustrates a time waveform in the case in which the transition time setting is τ[Nmax]. 
         [0044]    In a period in which communication for charging control is not performed, τ[0] having the shortest transition time among the transition times that can be set is designated as standard transition time setting. In addition, in a period in which the communication for the charging control is performed, the shortest transition time in the transition time settings in which communication interference does not occur due to harmonic noise is designated as optimal mid-communication transition time setting τ[k]. That is, as illustrated in the drawing, when the communication for the charging control is performed, the transition time is set long as compared with when the communication for the charging control is not performed. If the transition time of the switching waveform in the switching element increases, conversion loss of power increases and heat radiation increases. For this reason, the shortest transition time among the transition times that can be set is set as described above, so that harmonic components of the switching element can be suppressed. 
         [0045]    Next, a configuration of the power receiving side power converting unit  22  in the power receiving apparatus  20  will be described using  FIG. 4 .  FIG. 4  is an exemplary configuration diagram of the power converting unit in the power receiving apparatus according to the embodiment or the present invention. In  FIG. 4 , the power receiving side power converting unit  22  includes a rectifier  221 , a DC-DC converter  222 , a voltage detecting unit  223 , a gate driver  224 , and a PWM control signal generating unit  225 . 
         [0046]    In  FIG. 4 , the rectifier  221  of the power receiving side power converting unit  22  generates direct-current power from a high frequency signal supplied from the wireless power receiving unit  21  by rectification and smoothing by a diode and supplies the direct-current power to the DC-DC converter  222  The DC-DC converter  222  is a switching element for power conversion and converts the supplied direct-current power into direct-current power of a voltage suitable for charging of the storage battery  60 , for example, 240 V by an inverter circuit and supplies the direct-current power to the storage battery  60  through the voltage detecting unit  223 . In the voltage detecting unit  223 , a voltage value of the direct-current power used for the charging of the storage battery  60  is detected and the detected voltage value is supplied to the PWM control signal generating unit  225 . 
         [0047]    The frequency of the high frequency signal supplied from the wireless power receiving unit  21  is assumed as about 10 kHz to 100 kHz, but the frequency is not limited thereto. In addition, the voltage of the direct-current power generated by the DC-DC converter  222  is exemplified by 240 V, but various voltage values can be assumed according to a type of the connected storage battery  60 . 
         [0048]    In  FIG. 4 , the PWM control signal generating unit  225  compares the current command value supplied from the power receiving control unit  25  and the voltage value supplied from the voltage detecting unit  223 , generates a PWM control signal such that the voltage value supplied from the voltage detecting unit  223  is matched with the voltage command value supplied from the power receiving control unit  25 , and supplies the PWM control signal to the gate driver  224 . The gate driver  224  switches gate resistance of the switching element, on the basis of the transition time setting supplied from the power receiving control unit  25 , and controls a transition time of a rising waveform and a falling waveform of a time waveform of a switching signal in the DC-DC converter  222 . 
         [0049]    A relation of the PWM control signal generated by the PWM control signal generating unit  225  and the time waveform of the switching signal output from the DC-DC converter  222  to be switched by the transition time setting is the same as the relation of the PWM control signal and the transition time of the time waveform of the switching signal in the DC-AC inverter, described using  FIG. 3 , and explanation thereof is omitted. 
         [0050]    In the wireless charging system  1  configured as described above, an operation for performing charging form the power feeding apparatus  10  arranged on a road to the electrical vehicle  2  will be described using  FIGS. 5 to 7 . 
         [0051]      FIG. 5  is a diagram of an entire operation sequence of the wireless charging system. In  FIG. 5 , a system for supplying power between a power feeding apparatus arranged on a road and a power receiving apparatus included in an electrical vehicle is assumed as an example of the wireless charging system. However, installation locations of the power feeding apparatus and the power receiving apparatus are not limited to a form illustrated in  FIG. 5 . 
         [0052]    In  FIG. 5 , a left side shows an entire operation sequence in the power feeding apparatus  10  and a right side shows an operation sequence in the power receiving apparatus  20  of the electrical vehicle  2 . First, a user of the electrical vehicle stops the electrical vehicle in a predetermined place (step S 601 ) and operates the power feeding apparatus  10  arranged on the road and starts charging (S 501 ). 
         [0053]    Next, in steps  502  and S 602 , the power feeding control unit  13  of the power feeding apparatus  10  and the power receiving control unit  25  of the power receiving apparatus  20  exchange information (a maximum voltage and a maximum current) of the charging apparatus side and battery information (a maximum voltage, a battery capacity, a maximum charging time, and a charged battery capacity) of the electrical vehicle side through a communication interface and execute initialization processing such as mutual compatibility confirmation and proceed to steps S 503  and S 603 . 
         [0054]    During the initialization processing, the power conversion processing is not executed in both the power feeding side power converting unit  11  of the power feeding apparatus  10  and the power receiving side power converting unit  22  of the power receiving apparatus  20  and interference to communication for the charging control does not occur due to the harmonic noise components of the switching element. In steps S 502  and S 602 , a current command value regarding charging is transmitted from the power receiving control unit  25  of the power receiving apparatus  20  to the power feeding control unit  13  of the power feeding apparatus  10 . In step S 503 , the power feeding control unit  13  of the power feeding apparatus  10  starts power feeding on the basis of the current command value and proceeds to step S 504 . In step S 603 , the power receiving control unit  25  of the power receiving apparatus  20  receives power in the wireless power receiving unit  21  and starts charging for the storage battery  60  and proceeds to step S 604 . 
         [0055]    In step S 503 , the power feeding control unit  13  of the power feeding apparatus  10  designates τ[0] to be the standard setting as the transition time setting to the power feeding side power converting unit  11 . In step S 603 , the power receiving control unit  25  of the power receiving apparatus  20  designates τ[0] to be the standard setting as the transition time setting to the power receiving side power converting unit  22 . 
         [0056]    Next, in step S 605 , the power receiving control unit  25  of the power receiving apparatus  20  calculates a current command value suitable for charging on the basis of a charging state of the storage battery  60  and proceeds to step S 605 . 
         [0057]    Next, in step S 605 , the power receiving control unit  25  of the power receiving apparatus  20  transmits the current command value to the power feeding control unit  13  of the power feeding apparatus  10  and proceeds to step S 606 . 
         [0058]    Next, in step S 606 , the power receiving control unit  25  of the power receiving apparatus  20  determines whether a battery capacity charged in the storage battery  60  reached the prescribed value. When the battery capacity reached the prescribed value, that is, charging is completed, the power receiving control unit  25  proceeds to step S 607  and when the battery capacity did not reach the prescribed value, that is, charging is not completed, the power receiving control unit  25  returns to step S 604 . Here, a loop of steps S 604  to S 606  is continued until charging for the storage battery  60  is completed and is executed at an interval of 100 ms. An execution time interval of the loop of steps S 604  to S 606  can be freely set. 
         [0059]    Next, in step S 607 , after charging of the storage battery  60  is completed, the power receiving control unit  25  of the power receiving apparatus  20  transmits a charging stop request to the power feeding control unit  13  of the power feeding apparatus  10  and proceeds to step S 608 . Next, in step S 608 , the power receiving control unit  25  of the power receiving apparatus  20  determines whether power feeding for the storage battery  60  is stopped. When it cannot be confirmed that power feeding is stopped, the power receiving control unit  25  returns to step S 607  and retransmits the charging stop request and when it can be confirmed that charging processing is stopped, the power receiving control unit  25  proceeds to step S 609  and completes the charging processing. 
         [0060]    As described above, if communication timing from the power receiving control unit  25  of the power receiving apparatus  20  to the power feeding control unit  13  of the power feeding apparatus  10  is limited to during charging, the timing becomes the transmission of the current command value in step S 605  and the transmission of the charging stop request in step S 607 . 
         [0061]    Hereinafter, an operation of the case will be described in which communication of the current command value or the charging stop request is received from the power receiving apparatus  20  to the power feeding apparatus  10  during feeding of the power. 
         [0062]    First, in step S 504 , the power feeding control unit  13  of the power feeding apparatus  10  detects that the communication of the current command value or the charging stop request has been received from the power receiving apparatus  20  through the communication interface, by a voltage change of the AGC control signal in the communication period determining unit  131 , and proceeds to step SS 505 . 
         [0063]    In step S 505 , the power feeding control unit  13  of the power feeding apparatus  10  determines the mid-communication transition time fixation flag held in the storage unit  16 . In the case of “ON”, the power feeding control unit  13  proceeds to step S 510  and in the ease of “OFF”, the power feeding control unit  13  proceeds to step S 520 . The mid-communication transition time fixation flag is a flag set in a transition time search sequence of step S 520  to be described below. The mid-communication transition time fixation flag shows whether transition time setting of a switching signal to suppress occurrence of interference to the communication for the charging control is fixed and shows fixation of the transition time setting in the case of “ON”. 
         [0064]    When the transition time setting is fixed during the communication, in step S 510 , the transition time of the switching signal waveform during the communication between the power feeding apparatus  10  and the power receiving apparatus  20  is made to be longer than the transition time of the switching signal waveform during non-communication, a sequence to suppress the interference to the communication for the charging control is executed, and the process proceeds to step S 530 . Meanwhile, in step S 520 , a sequence to search the transition time setting to be set by step S 510  is executed and the process proceeds to step S 530 . 
         [0065]    Next, in step S 530 , the power feeding control unit  13  of the power feeding apparatus  10  determines a type of the received data. When the type is the current command value, the power feeding control unit  13  proceeds to step S 531  and when the type is the charging stop request, the power feeding control unit  13  proceeds to step S 532 . 
         [0066]    Next, in step S 531 , the power feeding control unit  13  of the power feeding apparatus  10  supplies the received current command value to the power feeding side power converting unit  11 , controls a current output to be fed, and returns to step S 504 . Meanwhile, in step S 530 , the power feeding control unit  13  of the power feeding apparatus  10  stops the conversion processing in the power feeding side power converting unit  11 , stops the current output to be fed, proceeds to step S 532 , and ends the charging processing. 
         [0067]    Here, a search operation of the transition time setting of the switching signal to suppress occurrence of the interference to the communication for the charging control in step S 520  of  FIG. 5  will be described using  FIG. 6 .  FIG. 6  is a diagram of an operation sequence to search the transition time setting of the switching signal to suppress occurrence of the interference to the communication for the charging control. 
         [0068]    In step S 521  of  FIG. 6 , the power feeding control unit  13  of the power feeding apparatus  10  designates the transition time setting as n-th τ[n], supplies the transition time setting to the power feeding side power converting unit  11 , and proceeds to step S 522 . Here, n is an integer and n is 0 when charging starts. In step S 526  to be described below, n is incremented. 
         [0069]    Next, in step S 522 , the power feeding control unit  13  of the power feeding apparatus  10  detects that the communication of the current command value or the charging stop request transmitted from the power receiving apparatus  20  through the communication interface has ended, by a voltage change of the AGC control signal in the communication period determining unit  131 , and proceeds to step S 523 . In step SS 523 , the power feeding control unit  13  of the power feeding apparatus  10  designates the transition time setting as the standard τ[0], supplies the transition time setting to the power feeding side power converting unit  11 , and proceeds to step S 524 . 
         [0070]    Next, in step S 524 , the power feeding control unit  13  of the power feeding apparatus  10  acquires a received data error rate from the error rate determining unit  132  and proceeds to step S 525 . 
         [0071]    In step S 525 , the power feeding control unit  13  of the power feeding apparatus  10  stores the transition time setting set in step S 521  and the received data error rate acquired in step S 524  in the storage unit  16  and proceeds to step S 526 . 
         [0072]    In step S 526 , the integer n to designate the transition time setting to be set by step S 521  is incremented and the process proceeds to step S 527 . 
         [0073]    In step S 527 , the power feeding control unit  13  of the power feeding apparatus  10  determines whether the integer n is larger than Nmax or not. When the integer n is larger than Nmax, the power feeding control unit  13  proceeds to step S 528  and when the integer n is smaller than Nmax, the power feeding control unit  13  skips the search sequence and proceeds to step S 530 . In step S 527 , this corresponds to determine whether received data error rates for the transition time settings (τ[0], τ[1] . . . τ[Nmax]) of (Nmax+1) types have been acquired. 
         [0074]    Next, in step S 528 , the power feeding control unit  13  of the power feeding apparatus  10  selects the transition time setting of the shortest transition time in the transition time settings in which the received data error rate is lower than a preset error rate, from received data error rate information for the transition time settings (τ[0], τ[1] . . . τ[Nmax]) of (Nmax+1) types stored in the storage unit  16 , stores the transition time setting as an optimal mid-communication transition time setting value τ[k] in the storage unit  16 , and proceeds to step S 529 . 
         [0075]    In step S 529 , the power feeding control unit  13  of the power feeding apparatus  10  changes the mid-communication transition time fixation flag stored in the storage unit  16  to “ON”, stores the mid-communication transition time fixation flag, skips the search sequence, and proceeds to step S 530 . 
         [0076]    The transition time search sequence in step S 520  to be described above is repeated (Nmax+1) times, so that a switching signal transition time setting value to suppress occurrence of interference to the communication for the charging control during the communication for the charging control in the wireless charging system can be acquired. 
         [0077]    Here, an operation for changing the transition time during the communication for the charging control in step S 510  of  FIG. 5  will be described using  FIG. 7 .  FIG. 7  is a diagram of an operation sequence to change switching transition time setting to suppress occurrence of the interference to the communication for the charging control. 
         [0078]    In step S 511  of  FIG. 7 , the power feeding control unit  13  of the power feeding apparatus  10  sets the mid-communication transition time setting τ[k] searched by step S 520  to the power feeding side power converting unit  11  and proceeds to step S 512 . In step S 512 , the power feeding control unit  13  of the power feeding apparatus  10  detects that the communication of the current command value or the charging stop request transmitted from the power receiving apparatus  20  through the communication interface has ended, by a voltage change of the AGC control signal in the communication period determining unit  131 , and proceeds to step S 513 . In step SS 513 , the power feeding control unit  13  of the power feeding apparatus  10  sets the transition time setting as the standard τ[0] to the power feeding side power converting unit  11  and proceeds to step S 514 . 
         [0079]    Next, in step S 514 , the power feeding control unit  13  of the power feeding apparatus  10  determines whether the received data error rate acquired by the error rate determining unit  132  is equal to or more than the prescribed value. When the received data error rate is equal to or more than the prescribed value, the power feeding control unit  13  determines that the interference to the communication for the charging control was suppressed in the transition time setting τ[k] set by step S 511  and proceeds to step S 515 . When the received data error rate is smaller than the prescribed value, the power feeding control unit  13  skips the change sequence S 510  and proceeds to step S 530 . Here, the prescribed value is 1%, for example. However, the prescribed value may be a value other than 0. 
         [0080]    Next, in step S 515 , the power feeding control unit  13  of the power feeding apparatus  10  changes the mid-communication transition time fixation flag to “OFF”, stores the mid-communication transition time fixation flag in the storage unit  16 , and proceeds to step S 516 . In step S 516 , the power feeding control unit  13  of the power feeding apparatus  10  resets the integer n to designate the transition time setting to be set by step S 521 , skips the change sequence S 510 , and proceeds to step S 530 . 
         [0081]    As described above, in the power converting device according to this embodiment, the reception error rate of the wireless communication for the charging control is evaluated for each transition time setting of the switching waveform immediately after starting charging and the transition time in which the harmonic noise is suppressed and the transition time in which the switching loss is small are set during only the transmission/reception period of the wireless communication for the charging control. Therefore, a power feeding apparatus, a power receiving apparatus, an electrical vehicle, a charging system, and a charging method that can suppress charging efficiency from being degraded, improve tolerance of communication for charging control against harmonic noise of an switching element, and improve reliability can be provided. 
         [0082]    In addition, because the period in which the transition time of the switching waveform is increased is only the transmission/reception period of the wireless communication for the charging control, the heat radiation according to the increase in the switching loss can be suppressed as compared with the case in which the transition time is increased at all times. Therefore, a heat radiation design cost can be decreased. 
         [0083]    The search of the transition time is performed immediately after starting the charging and the search of the transition time is performed again when the interference occurs in the wireless communication for the charging control during the normal charging operation. Therefore, it is possible to correspond to a change of a transmission/reception environment. 
         [0084]    In this embodiment, the method of controlling the transition time by switching the gate resistance has been described as a means for changing the transition time in the switching waveform of the switching element. However, even when a method of controlling the transition time by connecting a variable capacitor to an output terminal of the switching element in parallel and a method of controlling the transition time by connecting a reactor and an auxiliary circuit including a capacitor and a power semiconductor, changing constants, and suppressing a resonance characteristic are used, the same effects can be obtained. 
         [0085]    In addition, in this embodiment, even when the change of the AGC voltage has been used as a method of detecting the transmission/reception period of the communication for the charging control, but even when a synchronization method with periodic transmission of the current command value from the electrical vehicle and a method using a synchronization detection signal of the communication unit are used, the same effects can be obtained. 
         [0086]    The present invention is not limited to the embodiments described above and various modifications are included in the present invention. For example, the embodiments are described in detail to facilitate the description of the present invention and are not limited to embodiments in which all of the described configurations are included. In addition, a part of the configurations of the certain embodiment can be replaced by the configurations of another embodiment or the configurations of another embodiment can be added to the configurations of the certain embodiment. In addition, for a part of the configurations of the individual embodiments, other configurations can be added, removed, or replaced. 
         [0087]    In addition, a part or all of the individual configurations, functions, processing units, and processing means may be designed by integrated circuits and may be realized by hardware. In addition, the individual configurations and functions may be realized by software by analyzing programs for realizing the functions by a processor and executing the programs by the processor. Information such as the programs, the table, and the files for realizing the individual functions may be stored in a recording device such as a memory, a hard disk, and a solid state drive (SSD) or a recording medium such as an IC card, an SD card; and a DVD. 
         [0088]    In addition, control lines or information lines that are necessary for explanation are illustrated and the control lines or information lines do not mean that all control lines or information lines are necessary for a product. In actuality, almost all configurations may be conceived to be connected to each other. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1 : wireless charging system 
           2 : electrical vehicle 
           10 : power feeding apparatus 
           11 : power feeding side power converting unit 
           111 : rectifier 
           112 : DC-AC inverter 
           113 : current detecting unit 
           114 ,  224 : gate driver 
           115 ,  225 : PWM control signal generating unit 
           12 : wireless power feeding unit 
           13 : power feeding control unit 
           131 ,  251 : communication period determining unit 
           132 ,  252 : error rate determining unit 
           14 : power feeding side communication unit 
           15 ,  24 : antenna 
           16 ,  26 : storage unit 
           21 : wireless power receiving unit 
           22 : power receiving side power converting unit 
           222 : DC-DC converter 
           223 : voltage detecting unit 
           23 : power receiving side communication unit 
           24 : power receiving control unit 
           30 : driving system power converting unit 
           40 : motor 
           50 : driver 
           60 : storage battery