Patent Publication Number: US-2016236576-A1

Title: Contactless charging system, vehicle, and power supply device

Description:
TECHNICAL FIELD 
     This invention relates to a contactless charging system for a battery-carrying vehicle. 
     BACKGROUND ART 
     Electric vehicles (EVs) that travel using an electric motor and plug-in hybrid vehicles (PHVs) that travel using both an electric motor and a gasoline engine are increasing in popularity. A battery is installed in an EV and a PHV, and the vehicle is made to travel by driving the motor using electric energy stored in the battery. 
     At present, a charging system for an EV or a PHV is typically realized by disposing charging stations in each of a plurality of parking spaces provided in a parking area so that the vehicle can be charged while parked in the parking space. Further, power may be supplied to the vehicle from the charging station using either a contact charging system in which the charging station is connected to the vehicle by a dedicated charging cable, or a contactless charging system in which power is supplied using the principle of electromagnetic induction or the like while a state of contactless is maintained between the charging station and the vehicle. 
     Furthermore, when a vehicle is charged from a charging station, various control commands have to be exchanged between the charging station and the vehicle. In the contact charging system in which the charging station is connected to the vehicle by a charging cable, the various control commands can be exchanged by wired communication using a communication line in the charging cable, but in the case of a contactless charging system in which a charging cable is not used, the various control commands have to be exchanged between the charging station and the vehicle by contactless communication such as wireless communication. At this time, when there are a plurality of charging stations disposed in the parking area, there is a need for the vehicle by some means to specify which charging station it should establish wireless communication connection with. 
     Patent Document 1 discloses a device that performs contactless communication between a vehicle and power supply devices provided at a plurality of parking positions of charging stations. This contactless communication device comprises a charging device and a power receiving coil provided on the vehicle and power supply devices and power supply coils provided at the charging stations. A wireless communication unit of the charging device and an antenna of the charging device, and wireless communication units of the charging stations and antennas of the charging stations are provided to be used for wireless communication between the charging device of the vehicle and the charging stations. Validation power is output in order from the power supply coils provided at each power supply device of the charging stations in order to specify the charging station where the vehicle is parked, among the plurality of charging stations. Where the validation power is received by the power receiving coil, a wireless signal is transmitted from the wireless communication unit of the charging device of the vehicle through the antenna of the charging device, and the wireless signal is received by the wireless communication units of the charging stations through the antennas of the charging stations. Where a wireless signal is not received by the wireless communication unit of the charging station within a predetermined interval of time after the output of the validation power, it is determined that the vehicle is not present at the parking position of this particular power supply device. Meanwhile, where the wireless signal has been received by the wireless communication unit of the charging station within the predetermined interval of time after the output of the validation power, it is determined that the vehicle is present at the parking position of this power supply device. As a result, it is determined at which charging device the vehicle is parked. 
     [Patent Document 1] 
     Japanese Patent Application Laid Open No. 2011-223657. 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     However, the problem associated with the contactless communication system disclosed in Patent Document  1  is that it is necessary to wait for a certain time until it is determined whether or not the wireless signal is received by the wireless communication unit of the charging station within the predetermined interval of time after the output of the validation power for each charging device, and therefore it takes time to specify the parking position of the vehicle. 
     The present invention has been created to resolve the aforementioned problem, and it is an object of the present invention to provide a contactless charging system, a vehicle, and a power supply device that can easily and reliably specify a charging station with which wireless communication connection is to be established by the vehicle. 
     Means for Solving the Problems 
     The present invention provides a contactless charging system that comprises a charging device installed in a vehicle, and at least one charging station and performs contactless charging, wherein the at least one charging station includes: a power supply device that supplies power to the charging device; a power supply device wireless communication unit that is provided at the power supply device and performs wireless communication; and a power supply coil that is provided at the power supply device and performs contactless output of validation power and supply contactless of charging power, wherein the charging device includes: a wireless communication unit of the charging device for performing the wireless communication; a power receiving coil to which the validation power is contactlessly input and which contactlessly receives the charging power; and a validation power detector for detecting the validation power received by the power receiving coil, and wherein, in the wireless communication, communication is possible between the charging device and at least one power supply device, the power supply device holds in advance a pattern of the power to be supplied to the power supply coil for generating the validation power on the basis of different types of identification information, the pattern of power to be supplied to the power supply coil for generating the validation power is generated such that the validation power detector can detect the identification information when the validation power is detected by the validation power detector, the charging device sends a request for starting the power supply device to the power supply device, the power supply device which has received the request for starting the power supply device outputs the validation power from the power supply coil, the validation power is input to the power receiving coil, the validation power detector detects the validation power, the charging device sends a wireless connection request including information based on the identification information, the at least one power supply device validates each piece of identification information with the information based on the identification information, and a power supply device for which the identification information has matched the information based on the identification information responds to the charging device, thereby specifying the power supply device which is to perform the wireless communication with the charging device, among the at least one or more power supply devices, and establishing the wireless communication between the power supply device and the charging device. 
     The invention also provides a vehicle equipped with a charging device, which is contactlessly charged by at least one charging station including: a power supply device that supplies power to the charging device; a wireless communication unit of the power supply device that is provided at the power supply device and performs wireless communication; and a power supply coil that is provided at the power supply device and performs contactless output of validation power and contactless supply of charging power, wherein the charging device includes: a wireless communication unit of the charging device for performing the wireless communication; a power receiving coil which is provided in the charging device, to which the validation power is contactlessly input and which contactlessly receives the charging power; and a validation power detector for detecting the validation power received by the power receiving coil, and wherein, in the wireless communication, communication is possible between the charging device and at least one power supply device, the power supply device holds in advance a pattern of the power to be supplied to the power supply coil for generating the validation power on the basis of different types of identification information, the pattern of power to be supplied to the power supply coil for generating the validation power is generated such that the validation power detector can detect the identification information when the validation power is detected by the validation power detector, the charging device sends a request for starting the power supply device to the power supply device, the power supply device which has received the request for starting the power supply device outputs the validation power from the power supply coil, the validation power is input to the power receiving coil, the validation power detector detects the validation power, the charging device sends a wireless connection request including information based on the identification information, the at least one power supply device validates each piece of identification information with the information based on the identification information, and a power supply device for which the identification information has matched the information based on the identification information responds to the charging device, thereby specifying the power supply device which is to perform the wireless communication with the charging device, among the at least one or more power supply devices, and establishing the wireless communication between the power supply device and the charging device. 
     The invention also provides a power supply device including: a wireless communication unit of the power supply device for performing wireless communication; and a power supply coil that performs contactless output of validation power and supply of charging power, the power supply device being provided at at least one charging station and supplying power to a charging device installed in a vehicle, wherein the charging device includes: a wireless communication unit of the charging device for performing the wireless communication; a power receiving coil to which the validation power is input contactlessly and which contactlessly receives the charging power; and a validation power detector for detecting the validation power received by the power receiving coil, and wherein, in the wireless communication, communication is possible between the charging device and at least one power supply device, the power supply device holds in advance a pattern of the power to be supplied to the power supply coil for generating the validation power on the basis of different types of identification information, the pattern of the power to be supplied to the power supply coil for generating the validation power is generated such that the validation power detector can detect the identification information when the validation power is detected by the validation power detector, the charging device sends a request for starting the power supply device to the power supply device, the power supply device which has received the request for starting the power supply device outputs the validation power from the power supply coil, the validation power is input to the power receiving coil, the validation power detector detects the validation power, the charging device sends a wireless connection request including information based on the identification information, the at least one power supply device validates each piece of identification information with the information based on the identification information, and a power supply device for which the identification information have matched the information based on the identification information responds to the charging device, thereby specifying the power supply device which is to perform the wireless communication with the charging device, among the at least one or more power supply devices, and establishing the wireless communication between the power supply device and the charging device. 
     EFFECTS OF INVENTION 
     In accordance with the present invention, the power supply device holds in advance a pattern of the power to be supplied to the power supply coil for generating the validation power on the basis of different types of identification information, the pattern of the power to be supplied to the power supply coil for generating the validation power is generated such that the validation power detector can detect the identification information when the validation power is detected by the validation power detector, the charging device sends a request for starting the power supply device to the power supply device, the power supply device which has received the request for starting the power supply device outputs the validation power from the power supply coil, the validation power is input to the power receiving coil, the validation power detector detects the validation power, the charging device sends a wireless connection request including information based on the identification information, the at least one power supply device validates each piece of identification information with the information based on the identification information, and a power supply device for which the identification information has matched the information based on the identification information responds to the charging device, thereby making it possible to easily and reliably specify the charging station with which the wireless communication connection is to be established by the vehicle. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic diagram of the contactless charging system according to Embodiment 1 of the invention; 
         FIG. 2  is a schematic diagram of the power supply device and charging device provided in the contactless charging system according to Embodiment 1 of the invention; 
         FIG. 3  is a sequence diagram of the contactless charging system according to Embodiment 1 of the invention; 
         FIG. 4  is a schematic diagram illustrating the detection timing of the validation power in the validation power detector of the contactless charging system according to Embodiment 1 of the invention; 
         FIG. 5  illustrates an operation for comparing the detection timing of the validation power in the validation power detector of the contactless charging system according to Embodiment 1 of the invention with the validation power output time assigned in advance to each charging device; 
         FIG. 6  is a sequence diagram of the contactless charging system according to Embodiment 2 of the invention; 
         FIG. 7  is a schematic diagram illustrating the detection timing of the validation power in the validation power detector of the contactless charging system according to Embodiment 2 of the invention; 
         FIG. 8  illustrates an operation for comparing the detection of the validation power in the validation power detector of the contactless charging system according to Embodiment 2 of the invention with the validation power output value assigned in advance to each charging device. 
         FIG. 9  is a sequence diagram of the contactless charging system according to Embodiment 3 of the invention. 
         FIG. 10  is a schematic diagram illustrating the detection timing of the validation power in the validation power detector of the contactless charging system according to Embodiment 3 of the invention. 
         FIG. 11  illustrates an operation of comparing the detection timing of the validation power in the validation power detector of the contactless charging system according to Embodiment 3 of the invention with the validation power output value assigned in advance to each charging device. 
     
    
    
     EMBODIMENTS FOR CARRYING OUT THE INVENTION 
     The embodiments of the invention will be explained hereinbelow with reference to the appended drawings. 
     Embodiment 1 
     The configuration of the contactless charging system according to Embodiment 1 of the invention is shown in  FIG. 1 . 
     A contactless charging system  1  is constituted by a plurality of charging stations and a charging device  5  provided in a vehicle  3 . In Embodiment 1, three charging stations, namely, a charging station  2   a  and charging stations  2   b,    2   c,  which have the same configuration as the charging station  2   a,  are provided. The charging station  2   a  is provided with a power supply device  4   a.  The power supply device  4   a  is provided with a power supply coil  6   a,  and the charging device  5  is provided with a power receiving coil  7 . The power supply coil  6   a  of the charging station  2   a  is appropriately disposed, for example, on the floor surface of the charging station  2   a , and the power receiving coil  7  is appropriately disposed, for example, on the bottom surface of the vehicle  3 , so that the power supply coil  6   a  and the power receiving coil  7  face each other, with a predetermined air gap being present therebetween, when the vehicle  3  is parked at a predetermined parking position of the charging station  2   a.  The other two charging stations  2   b,    2   c  (see  FIG. 1 ) also have the same configuration as the charging station  2   a.    
     The configuration of the power supply device  4   a  is shown in  FIG. 2( a ) . The power supply coil  6   a  is electrically connected to a matching unit  8   a  of the power supply device. The matching unit  8   a  of the power supply device is electrically connected to a power source conversion unit  9   a . The power source conversion unit  9   a  is electrically connected to an AC power source  10   a.  The AC power source  10   a  is, for example, a 200-V AC power source. A power supply device controller  11   a  is electrically connected to the matching unit  8   a  of the power supply device, the power source conversion unit  9   a,  and a wireless communication unit  12   a  of the power supply device. A antenna  13   a  of the power supply device is electrically connected to the wireless communication unit  12   a  of the power supply device. The other two charging stations  2   b,    2   c  (see  FIG. 1 ) have power supply devices  4   b,    4   c , respectively, which have the same configuration as the power supply device  4   a.  The power supply device controller  11   a  of the power supply device  4   a  and the power supply device controllers (not shown) of the power supply devices  4   b,    4   c  store different validation power output times ta, tb, tc respectively which are identification information for identifying the power supply devices  4   a,    4   b,    4   c,  that have been assigned in advance to the power supply devices  4   a,    4   b ,  4   c.    
     The configuration of the charging device  5  is shown in  FIG. 2( b ) . The power receiving coil  7  is electrically connected to a matching unit  14  of the charging device. The matching unit  14  of the charging device is electrically connected to a rectifier  15 . The rectifier  15  is electrically connected to a detector  16  located outside of the charging device  5 . The detector  16  is electrically connected to a battery unit  17  located outside of the charging device  5 . Further, a validation power detector  21  for detecting the validation power is electrically connected to the power receiving coil  7 . The charging device controller  18  is electrically connected to the matching unit  14  of the charging device, the rectifier  15 , the detector  16 , the battery unit  17 , a wireless communication unit  19  of the charging device, and a validation power detector  21 . An antenna  20  of the charging device is electrically connected to the wireless communication unit  19  of the charging device. 
     Next, an operation of the contactless charging system according to Embodiment 1 of the present invention will be described with reference to  FIGS. 2 to 5 . 
       FIG. 3  shows an example of the sequence of operation of the contactless charging system. When the vehicle  3  is parked in the predetermined parking position of the charging station  2   a,  the charging device controller  18  detects that the vehicle  3  has been parked (A). Any desired means, such as means for detecting an operation of a parking brake of the vehicle  3  or means for detecting that a motive power supply switch of the vehicle  3  has been switched off, may be used as means for detecting the parking at this time. 
     Once the charging device controller  18  detects that the vehicle  3  has been parked, the charging device controller  18  starts the wireless communication unit  19  of the charging device (B), and the charging device controller  18  sends an instruction for starting the power supply device to the wireless communication unit  19  of the charging device (C). The wireless communication unit  19  of the charging device which has received the instruction for starting the power supply device outputs a request for starting the power supply device to the power supply devices  4   a,    4   b,    4   c  by broadcasting through the antenna  20  of the charging device (D). The signal of the request for starting the power supply device which is transmitted at this time includes a MAC address of the wireless communication unit  19  of the charging device. Where the wireless communication unit  12   a  of the power supply device receives the request for starting the power supply device through the antenna  13   a  of the power supply device  4   a,  the wireless communication unit  12   a  of the power supply device transmits a notification of the request for starting the power supply device to the power supply device controller  11   a  (E). The power supply device controller  11   a  verifies the state of the power supply device  4   a,  and where the power supply is possible, the power supplied from the AC power source  10   a  is converted in voltage and frequency by the power source conversion unit  9   a,  then converted into the power for generating the validation power, and supplied as the output power for the validation power to the power supply coil  6   a  through the matching unit  8   a  of the power supply device (F). In this case, the power which is, for example, from 10 W to about several tens of watts and sufficiently small by comparison with the charging power of several kilowatts may be the output power for the validation power for generating the validation power. As for the power supply devices  4   b,    4   c , likewise, the wireless communication units (not shown) of the power supply devices  4   b,    4   c  which have received the request for starting the power supply device transmit a notification of the request for starting the power supply device to the power supply device controllers (not shown) of the power supply devices  4   b,    4   c,  the power supply device controllers (not shown) of the power supply devices  4   b,    4   c  verify the state of the power supply devices  4   b,    4   c,  and where the power supply is possible, the power supplied from the AC power sources (not shown) of the power supply devices  4   b,    4   c  is converted in voltage and frequency by the power source conversion units (not shown) of the power supply devices  4   b ,  4   c  and then converted into power for generating the validation power and supplied as the output power for the validation power to the power supply coils (not shown) of the power supply devices  4   b,    4   c  through the matching units (not shown) of the power supply devices  4   b,    4   c.  Therefore, the instruction for starting the power supply device (C) and the request for starting the power supply device (D) are the instruction for outputting the validation power and request for outputting the validation power for outputting the validation power from the power supply coil  6   a  and the power supply coils (not shown) of the power supply devices  4   b,    4   c  as will be described. 
     In Embodiment 1, the vehicle  3  is parked at a predetermined parking position of the charging station  2   a  (see  FIG. 1 ). Thus, where the validation power is output from the power supply coil  6   a  as a result of supplying the output power for the validation power (Ga), the validation power is generated by the electromagnetic induction interaction in the power receiving coil  7  facing the power supply coil  6   a  with a predetermined air gap being present therebetween (H). The validation power generated in the power receiving coil  7  is detected by the validation power detector  21  (I). As shown in  FIG. 4 , in the validation power detector  21 , a time t for detecting the output time of the validation power within the range in which the detected value exceeds a threshold Th is detected. This time t for detecting the output time of the validation power is information based on identification information. In this case, the detected value may be a current value or a voltage value. Further, as shown in  FIG. 3 , the power for generating the validation power in the power supply coil  6   a  of the power supply device  4   a  and the power supply coils (not shown) of the power supply devices  4   b,    4   c  is controlled on the basis of the pattern of the power created by the power supply device controller  11   a  of the power supply device  4   a  and the power supply device controllers (not shown) of the power supply devices  4   b,    4   c  such that the time t for detecting the output time of the validation power matches the output times ta, tb, tc of the validation power. The validation power detector  21  notifies the charging device controller  18  of the time t for detecting the output time of the validation power (J). The validation power is also supplied to the power supply coils (not shown) of the power supply devices  4   b,    4   c  and the validation power is output (Gb, Gc). However, since the vehicle  3  performing the operations of the sequence of Embodiment 1 is not at the parking position of the charging stations  2   b,    2   c,  the power receiving coil  7  does not face the power supply coil with a predetermined air gap being present therebetween, and no electromagnetic induction is generated. Therefore, the validation power is not transmitted to the vehicle  3 . 
     The charging device controller  18  transmits a instruction for searching the power supply device along with the time t for detecting the output time of the validation power to the wireless communication unit  19  of the charging device (K). The wireless communication unit  19  of the charging device outputs a request for searching the power supply device along with the time t for detecting the output time of the validation power by broadcasting through the antenna  20  of the charging device (L). 
     Where the wireless communication unit  12   a  of the power supply device receives the request for searching the power supply device through the antenna  13   a  of the power supply device, the wireless communication unit  12   a  of the power supply device transmits the notification of the request for searching the power supply device along with the time t for detecting the output time of the validation power to the power supply device controller  11   a  (M). As shown in  FIG. 5 , the power supply device controller  11   a  validates the time t for detecting the output time of the validation power with the output time to of the validation power (Na in  FIG. 3 ). Likewise, in the power supply controllers (not shown) of the power supply devices  4   b,    4   c  which have received the request for searching the power supply device also validate the time t for detecting the output time of the validation power with the output times tb, tc of the validation power (Nb, Nc in  FIG. 3 ). In Embodiment 1, the time t for detecting the output time of the validation power matches the output time to of the validation power. Therefore, as shown in  FIG. 3 , the power supply device controller  11   a  transmits a response instruction for the search to the power supply device wireless communication unit  12   a  (O). Since the time t for detecting the output time of the validation power does not match the output times tb, tc of the validation power, no operation is performed in the power supply device controllers (not shown) of the power supply devices  4   b,    4   c.    
     The wireless communication unit  12   a  of the power supply device that has received the response instruction for the search transmits a response for the search by unicasting to the wireless communication unit  19  of the charging device through the antenna  13   a  of the power supply device by using the MAC address of the wireless communication unit of the charging device (P). The wireless communication unit  19  of the charging device receives the response for the search through the antenna  20  of the charging device. The wireless communication unit  19  of the charging device transmits a reception notification to the response for the search to the charging device controller  18  (Q). The charging device controller  18  transmits an instruction for requesting the connection to the wireless communication unit  19  of the charging device (R). The wireless communication unit  19  of the charging device transmits the connection request to the wireless communication unit  12   a  of the power supply device by unicasting through the antenna  20  of the charging device (S). The wireless communication unit  12   a  of the power supply device receives the connection request through the antenna  13   a  of the power supply device. The wireless communication unit  12   a  of the power supply device transmits the response for the connection to the wireless communication unit  19  of the charging device through the antenna  13   a  of the power supply device (T). The wireless communication unit  19  of the charging device receives the response for the connection through the antenna  20  of the charging device. As a result, wireless communication is established between the wireless communication unit  12   a  of the power supply device and the wireless communication unit  19  of the charging device. 
     As shown in  FIGS. 2( a ) and 2( b ) , after wireless communication is established, the voltage and frequency of the power supplied from the alternating current power supply  10   a  is converted by the power supply conversion unit  9   a,  impedance matching between the matching unit  8   a  of the power supply device and the matching unit  14  of the charging device is performed, and then the power is supplied to the power supply coil  6   a.  Charging power is generated in the power receiving coil  7  which is opposite the power supply coil  6   a,  while maintaining a predetermined air gap by an electromagnetic induction interaction. The charging power is rectified by the rectifier  15  via the matching unit  14  of the charging device, and then charged to the battery unit  17  via the detection unit  16  that is used to detect a voltage and a current. 
     Thus, the power supply devices  4   a,    4   b,    4   c  hold in advance the pattern of the power to be supplied to the power supply coil  6   a  and the power supply coils (not shown) of the power supply devices  4   b,    4   c  for generating the validation power on the basis of respectively different output times ta, tb, tc of the validation power, the pattern of power to be supplied to the power supply coil  6   a  and the power supply coils (not shown) of the power supply devices  4   b,    4   c  for generating the validation power is generated such that the validation power detector  21  can detect the output times ta, tb, tc of the validation power when the validation power is detected by the validation power detector  21  the charging device  5  sends the request for starting the power supply device to the power supply devices  4   a,    4   b,    4   c,  the power supply devices  4   a,    4   b,    4   c  which have received the request for starting the power supply device output the validation power from the power supply coil  6   a  and the power supply coils (not shown) of the power supply devices  4   b,    4   c,  the validation power is input to the power receiving coil  7 , the validation power detector  21  detects the validation power, the charging device  5  sends a wireless connection request including the time t for detecting the output time of the validation power, the power supply devices  4   a,    4   b,    4   c  validate each output time ta, tb, tc of the validation power with the time t for detecting the output time of the validation power, and the power supply device  4   a  for which the output time ta, tb, tc of the validation power have matched the time t for detecting the output time of the validation power responds to the charging device  5 , thereby making it possible to specify easily and reliably the charging station  2   a  which is to establish the wireless communication connection with the vehicle  3 . 
     Embodiment 2 
     The configuration of the contactless charging system according to Embodiment 2 of the invention is described hereinbelow. Because the same reference numerals and symbols as those in  FIGS. 1 to 5  represent the same or similar constitutional elements in the below-described embodiment, the detailed explanations thereof are herein omitted. 
     In the contactless charging system according to Embodiment 2 of the invention, an output power value is used as the measurement value in Embodiment 1 for specifying the parking position of the vehicle. The different output power values LVa, LVb, LVc of the validation power which are pieces of identification information for identifying the power supply devices  4   a,    4   b,    4   c  that has been assigned in advance to the power supply devices  4   a,    4   b,    4   c,  are stored in the power supply device controller  11   a  of the power supply device  4   a  and power supply device controllers (not shown) of the power supply devices  4   b,    4   c,  respectively. Other features of the contactless charging system are the same as those in Embodiment 1. 
     The operation of the contactless charging system according to Embodiment 2 of the invention is explained hereinbelow. 
       FIG. 6  shows the example of the sequence of Embodiment 2. In  FIG. 6 , the same letters as those in  FIG. 3  represent the same operations, and the operations denoted by the letters of  FIG. 3  which are marked with [′] are modified from the corresponding operations shown in  FIG. 3 . The operations from (A) to (I) which are performed until the validation power generated by the power receiving coil  7  is detected by the validation power detector  21  are the same as those in Embodiment 1. As shown in  FIG. 7 , a detected power value LV of the output power value of the validation power, for which the detected value exceeds a threshold Th, is detected in the validation power detector  21 . This detected power value LV of the output power value of the validation power is information based on the identification information. In this case, the detected value may be a current value or a voltage value. Further, as shown in  FIG. 6 , the power for generating the validation power in the power supply coil  6   a  of the power supply device  4   a  and the power supply coils (not shown) of the power supply devices  4   b,    4   c  is controlled on the basis of the pattern of power created in the power supply device controller  11   a  of the power supply device  4   a  and the power supply device controllers (not shown) of the power supply devices  4   b,    4   c , such that the detected power value LV of the output power value of the validation power matches the output power values LVa, LVb, LVc of the validation power. The validation power detector  21  notifies the charging device controller  18  of the detected power value LV of the output power value of the validation power (J′). The validation power is also supplied to the power supply coils (not shown) of the power supply devices  4   b,    4   c,  and the validation power is output. However, since the vehicle  3  in which the charging preparation sequence has been implemented is not at the parking position of the charging stations  2   b,    2   c,  the power receiving coil  7  does not face the power supply coil with a predetermined air gap being present therebetween, and no electromagnetic induction is generated. Therefore, the validation power is not transmitted to the vehicle  3 . 
     The charging device controller  18  transmits the instruction for searching the power supply device along with the detected power value LV of the output power value of the validation power to the wireless communication unit  19  of the charging device (K′). The wireless communication unit  19  of the charging device outputs the request for searching the power supply device along with the detected power value LV of the output power value of the validation power by broadcasting through the antenna  20  of the charging device (L′). 
     Where the wireless communication unit  12   a  of the power supply device receives the request for searching the power supply device through the antenna  13   a  of the power supply device, the wireless communication unit  12   a  of the power supply device transmits the notification of the request for searching the power supply device along with the detected power value LV of the output power value of the validation power to the power supply device controller  11   a  (M′). As shown in  FIG. 8 , the power supply device controller  11   a  validates the detected power value LV of the output power value of the validation power with the output power value LVa of the validation power (Na′ in  FIG. 6 ). Likewise, the power supply device controllers (not shown) of the power supply devices  4   b,    4   c  which have received the request for searching the power supply device also validate the detected power value LV of the output power value of the validation power with the output power valued LVb, LVc of the validation power (Nb′, Nc′ in  FIG. 6 ). In Embodiment 2, the detected power value LV of the output power value of the validation power matches the output power value LVa of the validation power. Therefore, the power supply device controller  11   a  transmits a response instruction for the search to the wireless communication unit  12   a  of the power supply device (O′). Since the detected power value LV of the output power value of the validation power does not match the output power values LVb, LVc of the validation power, no operation is performed in the power supply device controllers (not shown) of the power supply devices  4   b,    4   c.  Subsequent operations are the same as those in Embodiment 1. 
     Thus, the power supply devices  4   a,    4   b,    4   c  hold in advance the patterns of the power to be supplied to the power supply coil  6   a  and the power supply coils (not shown) of the power supply devices  4   b,    4   c  for generating the validation power on the basis of respectively different output power values LVa, LVb, LVc of the validation power, and the patterns of the power to be supplied to the power supply coil  6   a  and the power supply coils (not shown) of the power supply devices  4   b,    4   c  for generating the validation power are generated such that the output power values LVa, LVb, LVc of the validation power can be detected by the validation power detector  21  when the validation power is detected by the validation power detector  21 . The charging device  5  sends a request for starting the power supply device to the power supply devices  4   a,    4   b,    4   c,  the power supply devices  4   a,    4   b,    4   c  which have received the request for starting the power supply device output the validation power from the power supply coil  6   a  and the power supply coils (not shown) of the power supply devices  4   b,    4   c,  the validation power is input to the power receiving coil  7 , the validation power detector  21  detects the validation power, the charging device  5  sends a wireless connection request including the detected power value LV of the output power value of the validation power, the power supply devices  4   a,    4   b,    4   c  validate the output power values LVa, LVb, LVc of the validation power with the detected power value LV of the output power value of the validation power, and the power supply device  4   a  for which the output power value LVa, LVb, LVc of the validation power matches the detected power value LV of the output power value of the validation power responds to the charging device  5 , thereby making it possible to obtain the same effect as in Embodiment 1. 
     Embodiment 3 
     The configuration of the contactless charging system according to Embodiment 3 of the invention is described hereinbelow. 
     In the contactless charging system according to Embodiment 3 of the invention, a delay time from the reception of the output request to the output is used as the measurement value in Embodiment 1 for specifying the parking position of the vehicle. The different output delay times Dta, Dtb, Dtc of the validation power, which are pieces of identification information for identifying the power supply devices  4   a,    4   b ,  4   c  that have been assigned in advance to the power supply devices  4   a,    4   b,    4   c,  are stored in the power supply device controller  11   a  of the power supply device  4   a  and power supply device controllers (not shown) of the power supply devices  4   b ,  4   c.  Other features of the contactless charging system are the same as those in Embodiment 1. 
     The operation of the contactless charging system according to Embodiment 3 of the invention is explained hereinbelow. 
       FIG. 9  shows the example of the sequence of Embodiment 3. In  FIG. 9 , the same letters as those in  FIG. 3  represent the same operations, and the operations denoted by the letters of  FIG. 3  which are marked with [″] are modified from the corresponding operations shown in  FIG. 3 . The operations from (A) to (I) in which the validation power generated by the power receiving coil  7  is detected by the validation power detector  21  are the same as those in Embodiment 1. As shown in  FIG. 10 , the time Dt for detecting the output delay time of the validation power, for which the detected value exceeds a threshold Th, is detected in the validation power detector  21 . This detected time Dt of the output delay time of the validation power is information based on the identification information. For example, in the case of the output delay time Dta of the validation power of the power supply device  4   a,  this is the delay time from when the output request from the wireless communication unit  19  of the charging device is received by the power supply device controller  11   a  until when the validation power is output from the power supply coil  6   a . Likewise, with respect to the power supply devices  4   b,    4   c,  the output delay times Dtb, Dtc of the validation power are the delay times from when the output request from the wireless communication unit  19  of the charging device is received by the power supply controllers (not shown in the figure) until when the validation power is output from the power supply coils (not shown in the figure). In this case, the detected value may be a current value or a voltage value. Further, the power for generating the validation power in the power supply coil  6   a  of the power supply device  4   a  and the power supply coils (not shown) of the power supply devices  4   b,    4   c  is controlled on the basis of the pattern of the power created in the power supply device controller  11   a  of the power supply device  4   a  and the power supply device controllers (not shown) of the power supply devices  4   b,    4   c,  such that the time Dt for detecting the output delay time of the validation power matches the output delay times Dta, Dtb, Dtc of the validation power. The validation power detector  21  notifies the charging device controller  18  of the time Dt for detecting the output delay time of the validation power (J″). The validation power is also supplied to the power supply coils (not shown) of the power supply devices  4   b,    4   c,  and the validation power is output. However, since the vehicle  3  in which the charging preparation sequence has been implemented is not at the parking position of the charging stations  2   b,    2   c,  the power receiving coil  7  does not face the power supply coil with a predetermined air gap being present therebetween, and no electromagnetic induction is generated. Therefore, the validation power is not transmitted to the vehicle  3 . 
     The charging device controller  18  transmits the instruction for searching the power supply device along with the time Dt for detecting the output delay time of the validation power to the wireless communication unit  19  of the charging device (K″). The wireless communication unit  19  of the charging device outputs the request for searching the power supply device along with the time Dt for detecting the output delay time of the validation power by broadcasting through the antenna  20  of the charging device (L″). 
     Where the wireless communication unit  12   a  of the power supply device receives the request for searching the power supply device through the antenna  13   a  of the power supply device, the wireless communication unit  12   a  of the power supply device transmits the notification of the request for searching the power supply device along with the detected power value LV of the output power value of the validation power to the power supply device controller  11   a  (M″). As shown in  FIG. 11 , the power supply device controller  11   a  validates the time Dt for detecting the output delay time of the validation power with the output delay time Dta of the validation power (Na″ in  FIG. 9 ). Likewise, the power supply device controllers (not shown) of the power supply devices  4   b ,  4   c  which have received the request for searching the power supply device also validate the time Dt for detecting the output delay time of the validation power with the output delay times Dtb, Dtc of the validation power (Nb″, Nc″ in  FIG. 9 ). In Embodiment 2, the time Dt for detecting the output delay time of the validation power matches the output delay time Dta of the validation power. Therefore, the power supply device controller  11   a  transmits a response instruction for the search to the wireless communication unit  12   a  of the power supply device (O″). Since the time Dt for detecting the output delay time of the validation power does not match the output delay times Dtb, Dtc of the validation power, no operation is performed in the power supply device controllers (not shown) of the power supply devices  4   b,    4   c.  Subsequent operations are the same as those in Embodiment 1. 
     Thus, the power supply devices  4   a,    4   b,    4   c  hold in advance the patterns of power to be supplied to the power supply coil  6   a  and the power supply coils (not shown) of the power supply devices  4   b,    4   c  for generating the validation power on the basis of respectively different output delay times Dta, Dtb, Dtc of the validation power, and the patterns of power to be supplied to the power supply coil  6   a  and the power supply coils (not shown) of the power supply devices  4   b ,  4   c  for generating the validation power are generated such that the output delay times Dta, Dtb, Dtc of the validation power can be detected by the validation power detector  21  when the validation power is detected by the validation power detector  21 . The charging device  5  sends a request for starting the power supply device to the power supply devices  4   a,    4   b,    4   c , the power supply devices  4   a,    4   b,    4   c  which have received the request for starting the power supply device output the validation power from the power supply coil  6   a  and the power supply coils (not shown) of the power supply devices  4   b,    4   c , the validation power is input to the power receiving coil  7 , the validation power detector  21  detects the validation power, the charging device  5  sends a wireless connection request including the time Dt for detecting the output delay time of the validation power, the power supply devices  4   a,    4   b,    4   c  validate the output delay times Dta, Dtb, Dtc of the validation power with the time Dt for detecting the output delay time of the validation power, and the power supply device  4   a  for which the output delay time Dta, Dtb, Dtc of the validation power matches the time Dt for detecting the output delay time of the validation power responds to the charging device  5 , thereby making it possible to obtain the same effect as in Embodiment 1. 
     In Embodiments 1 to 3, the number of the charging stations provided in the contactless charging system  1  is 3 which are the charging stations  2   a,    2   b,    2   c,  but the number of the charging stations may be 1, 2, 4, or more. 
     In Embodiments 1 to 3, the operations (Q) and (R) and then the operation (S) are performed after the wireless communication unit  19  of the charging device  5  of the vehicle  3  has received the response for the search through the antenna  20  of the charging device, as shown in  FIGS. 3, 6, and 9 , but the operation (S) may be performed after the response for the search has been received without performing the operations (Q) and (R).