Non-contact power supply system, non-contact power transmission device, non-contact power reception device, and method therefor

Abstract

In order to improve the safety of non-contact power supply, a power receiving device (30) outputs a power transmission request signal requesting power transmission, and a power transmission device (50) that receives the power transmission request signal performs power transmission using magnetic field coupling with respect to the power receiving device during a predetermined power transmission period. After the power transmission period ends, the power transmission device switches to a power transmission state in which the amount of power transmission is less than the amount of power transmission during the power transmission period. Such a power transmission state may be a state in which power transmission is cut off, or a state in which power transmission is performed by reducing the amount of power transmission than during the power transmission period.

Description

Reference to Related Applications

[0001] This application is based on Patent Application No. 2023-033500 filed in Japan on March 6, 2023, the priority of which is claimed, and the entire contents of which are incorporated by reference herein. TECHNICAL FIELD

[0002] The present disclosure relates to a non-contact power supply. BACKGROUND

[0003] In a non-contact power supply system, in order to simplify the system structure, a structure in which a power transmission device and a power receiving device perform transmission of signals via electromagnetic coupling for power supply is sometimes adopted. For example, in Patent Document International Publication No. WO2020 / 183819, in a case where it is desired to stop the power supply operation of the power transmission device on the power receiving device side, the amount of current supplied from the direct current power supply on the power transmission device side is changed by controlling the impedance of the power receiving circuit of the power receiving device, and a power transmission stop signal is demodulated in accordance with the change, and the operation of the inverter of the power transmission device is stopped.

[0004] However, this method of controlling the impedance of the power receiving circuit is easily affected by the position of the power receiving coil of the power receiving device with respect to the power transmission coil of the power transmission device, the characteristics of the capacitor, the coil, and the filter circuit, and the like that constitute the resonance circuit for power supply, and thus, there is a possibility that the power transmission stop signal will not be demodulated. In a case where the power supply stop request from the power receiving device to the power transmission device side cannot be properly transmitted, the power transmission device continues the power supply operation, and thus, in a case where some kind of abnormality occurs in the power receiving device, the power supply from the power transmission device can possibly expand the undesirable situation. SUMMARY

[0005] The present disclosure can be implemented in the following modes or application examples.

[0006] A first mode of the present disclosure is a mode of a non-contact power supply system in which power is supplied from a power transmission device to a power receiving device through magnetic field coupling. In this non-contact power supply system, the power receiving device outputs a power transmission request signal requesting power transmission, and the power transmission device, upon receiving the power transmission request signal, switches to a standby state in which the amount of power transmission is less than that during a predetermined power transmission period after power transmission using the magnetic field coupling with the power receiving device during the power transmission period.

[0007] A second aspect of the present disclosure is a power transmission device that transmits power to a power receiving device by magnetic field coupling. The power transmission device, upon receiving a power transmission request signal from the power receiving device, performs first power transmission using the magnetic field coupling with the power receiving device during a predetermined power transmission period, and after the power transmission period, switches to a power transmission state in which the amount of power transmission is less than that of the first power transmission. The power transmission device, upon receiving the power transmission request signal, switches to a standby state in which the amount of power transmission is less than that of the first power transmission after the first power transmission is performed during a predetermined period, and thus, the undesired power transmission is not continued.

[0008] A third aspect of the present disclosure is a power receiving device that receives power transmitted from a power transmission device by magnetic field coupling. The power receiving device outputs a power transmission request signal that requests power transmission to the power transmission device, and the power transmission device, upon receiving the power transmission request signal, performs first power transmission using the magnetic field coupling with the power receiving device during a predetermined power transmission period, and after the power transmission period, switches to a power transmission state in which the amount of power transmission is less than that of the first power transmission, and after the switch, outputs the power transmission request signal again if a predetermined condition is satisfied. Thus, it is possible to avoid or suppress the continuation of undesired power reception, and if the predetermined condition is satisfied, the power transmission request signal is output again, and thus, if there is no factor that should interrupt the power reception, the power reception can be continued.

[0009] A fourth aspect of the present disclosure is a non-contact power supply method that supplies power from a power transmission device to a power receiving device by magnetic field coupling. In the non-contact power supply method, the power receiving device outputs a power transmission request signal that requests power transmission, and the power transmission device, upon receiving the power transmission request signal, performs power transmission using the magnetic field coupling with the power receiving device during a predetermined power transmission period, and after the end of the power transmission period, switches to a power transmission state in which the amount of power transmission is less than that of the power transmission during the power transmission period. In the non-contact power supply method, it is possible to avoid or suppress the continuation of undesired power transmission. BRIEF DESCRIPTION OF DRAWINGS

[0010] The above objects, other objects, features, and advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: Figure 1 is a schematic configuration diagram of a non-contact power supply system according to an embodiment. Figure 2 is a schematic configuration diagram of a power transmission device and a power receiving device that constitute a non-contact power supply system. Figure 3 is an explanatory diagram illustrating an example of standby current and resonance current in a power transmission circuit of a power transmission device. Figure 4It is an explanatory diagram showing the positional relationship between the receiving coil and the transmitting coil and the relationship of the current flowing through the transmitting coil. Figure 5 It is a flowchart that compares and illustrates the processing outlines of the power receiving side and the power transmitting side. Figure 6 This is an explanatory diagram showing an example of the structure of the power supply circuit of the power supply device including the switching unit. Figure 7 This is an explanatory diagram showing an example of the circuit structure of a power receiving device. Figure 8 It is a timing diagram showing the operation of the power receiving device and the power transmitting device. Figure 9 This is an explanatory diagram showing a structural example of the power receiving device side in the second embodiment. Figure 10 This is a flowchart illustrating an example of the processing on the power receiving device side in the second embodiment. Figure 11 This is a flowchart illustrating an example of the processing on the power transmission device side in the second embodiment. Figure 12 This is a schematic structural diagram of the power supply device and the power receiving device constituting the contactless power supply system of the third embodiment. Figure 13 This is a flowchart illustrating an example of the power supply side processing routine as a first variation. Figure 14 This is a flowchart illustrating an example of the power supply side processing routine as a second variation. Figure 15 This is a flowchart illustrating an example of the power supply side processing routine as a third variation. Detailed Implementation

[0011] A. First implementation method: (A1) Overall structure of the contactless power supply system: Figure 1A schematic configuration of a non-contact power feeding system 100 including the first embodiment of the power feeding device 50 and the power receiving device is shown. As shown in the figure, the non-contact power feeding system 100 is configured of a plurality of power feeding devices 50 buried in a road surface SF, a ground, and a power receiving device 30 installed in a mobile body 20 that travels autonomously on the road surface SF. The mobile body 20 includes a drive wheel 21 driven by a not-shown motor included in a load device 45, a driven wheel 22 that supports the mobile body 20 together with the drive wheel 21 so as to be movable on the road surface SF, a power receiving coil 31 disposed under a floor of the mobile body 20, and the like. The power receiving coil 31 is coupled to a magnetic field of a power feeding coil 51 of the power feeding device 50 prepared on the road surface SF side to receive supply of alternating-current power, and supplies electric power to the load device 45. In addition, the power feeding device 50 and the non-contact power feeding system 100 including the power feeding device 50 are not limited to a system that supplies electric power to the power receiving device 30 of the mobile body 20, but are a device and a system that perform power feeding in a non-contact manner. The power receiving device can also be a device and a system that perform power feeding and power supply to a device other than the mobile body, such as a portable terminal. The mobile body 20 is not limited to one that travels on a road outside a building, but also includes a transport vehicle and the like used inside a factory, a hospital, and the like. The number of wheels of the mobile body 20 can be plural, or the mobile body 20 can be moved by a method other than wheels, such as by magnetic levitation.

[0012] The power feeding device 50 can be disposed on a road surface, or on a wall surface, a ceiling, in addition to the configuration of being buried in the road surface SF. In this case, the power receiving device 30 is disposed at a prescribed position in the mobile body 20 in correspondence with the disposition position of the power feeding device 50. For example, if the power feeding device 50 is laid on a wall surface, the power receiving device 30 can be disposed at a side surface of the mobile body 20. In addition, the power receiving device 30 can be moved inside the mobile body 20 in cooperation with the laying position of the power feeding device 50, or a plurality of power receiving devices 30 can be prepared in advance and used by switching.

[0013] The plurality of power feeding devices 50 that supply electric power to the power receiving device 30 of the mobile body 20 each include the same configuration in the present embodiment, and are arranged along a movement path of the mobile body 20. Of course, the power feeding devices 50 are not limited to the movement path of the mobile body 20, but can be arranged two-dimensionally on the road surface SF. Each of the power feeding devices 50 is connected to a common main electric power line RFP. The main electric power line RFP is supplied with alternating-current power of a high frequency (for example, 85 KHz) of a frequency fl from a main power source device 60. In the present embodiment, each of the power feeding devices 50 has the same configuration, but for example, power feeding coils 51 and the like of different sizes can be alternately disposed, as long as power feeding is possible, and the configurations do not need to be the same. Of course, the power feeding device 50 can be one.

[0014] The main power supply device 60 receives a supply of low-frequency (e.g., 60 Hz) alternating current from the main power supply 65 and converts it to high-frequency alternating current. It is known that the side of the main power supply device 60 that receives power from the main power supply 65 includes a noise filter, a PFC circuit, an inverter, and a filter for alternating current output. The power supplied from the main power supply 65 is converted to alternating current of the above-described frequency by the inverter and output to the main power line RFP.

[0015] Figure 2 The schematic structure of the power feeding device 50 and the power receiving device 30 is shown. In the drawing, the state in which one of the plurality of power feeding devices 50 supplies power to the power receiving device 30 of the mobile body 20 is shown. At this time, the power feeding coil 51 of the power feeding device 50 is magnetically coupled with the power receiving coil 31 of the power receiving device 30, and an induced current (alternating current) flows in the power receiving coil 31. The power receiving device 30 includes a power receiving circuit 35 that receives power using the power receiving coil 31, a load device 45 that operates using the received power, a power receiving control section 40 that is constituted by a CPU or a memory, and a power feeding request output section 70 that outputs a power feeding request in accordance with an instruction from the power receiving control section 40. The power receiving coil 31 receives power from the power feeding coil 51 through magnetic coupling, and in order to apply a direct-current voltage to the load device 45, a power receiving circuit and a rectifying circuit are provided in the power receiving circuit 35, and the structures of these circuits will be described later in detail. In addition, the power receiving circuit refers to a circuit connected to the power receiving coil 31, but various circuit elements such as a current sensor are sometimes connected in the power receiving circuit, and the broad "power receiving circuit" refers to a closed circuit through which a current flows when power is received using the power receiving coil 31. In the present embodiment, the load device 45 includes a device that uses main power used in the mobile body, such as a mobile motor of the mobile body 20, but sometimes includes a battery that temporarily stores power.

[0016] The power feeding device 50 that feeds power to this power receiving device 30 has, in addition to the power feeding coil 51, a power feeding control section 80 that controls a power feeding current. The power feeding control section 80 includes a CPU and a memory, executes a program necessary for processing on the power feeding side, and performs control of the entire power feeding device 50 including detection of a power feeding request that requests the start of power feeding. The power feeding control section 80, in the case where a power feeding request is received from the power receiving device 30, after a predetermined power feeding period has elapsed, switches power feeding using magnetic coupling with the power receiving device 30 to a standby state in which the amount of power feeding is less than the amount of power feeding during the power feeding period.

[0017] The output of the power transmission request from the power receiving device 30 and the detection of the power transmission request by the power transmission device 50 can be performed in various ways. For example, the power transmission request output section 70 of the power receiving device 30 is configured as a transmitter that performs near field wireless communication such as Bluetooth (registered trademark) or the like, and the power transmission control section 80 is provided with the function of a receiver that detects the wireless communication from the power transmission request output section 70 to perform the transmission and reception of the power transmission request. Alternatively, near field communication using an RFID or the like can be used, and wireless communication using WiFi or the like can also be used. The communication can also be performed by optical communication or the like. Such communication is not limited to a non-contact method, and can also be performed by wired communication by contacting the contactor on the power receiving device 30 side to the contact terminal prepared on the power transmission device 50 side. In addition, the power transmission request can also be transmitted using the magnetic field coupling of the power receiving coil 31 and the power transmission coil 51. In this case, a coil other than the power receiving coil 31 can also be used to change the strength of the magnetic field coupling, as a result of which the magnitude of the current flowing through the power transmission coil 51 is changed to the power transmission request, and an alternating voltage of a frequency f2 different from the frequency fl of the alternating voltage used in the power transmission can also be applied to the power receiving coil 31, and the frequency f2 is modulated and processed as the power transmission request.

[0018] In the case where the power transmission request from the power receiving device 30 is received, the power transmission control section 80 switches the power transmission using the magnetic field coupling for the power receiving device 30 to the standby state in which the power transmission amount is less than that in the predetermined power transmission period after the power transmission period elapses. If this operation can be performed, the power transmission control section 80 can be an arbitrary circuit configuration. For example, a switching section that performs switching of the impedance of the closed circuit passing through the power transmission coil 51 is provided, and after the power transmission request from the power receiving device 30 is received, the impedance of the closed circuit is reduced, the power transmission is performed, and after the predetermined power transmission period elapses, the impedance is switched to the standby state in which the impedance is larger than that in the power transmission period. The switching of the impedance can be performed using a resistor inserted into the closed circuit, and in view of the fact that the current flowing through the closed circuit is alternating current, the capacity (capacitance) of a capacitor inserted into the closed circuit can also be switched. Of course, the inductance of the power transmission coil 51 can also be switched. These switches can be easily realized by switching the connection of capacitors having different capacities or switching the connection of taps provided to the power transmission coil 51 having different numbers of windings. Of course, a component that can change the capacity or inductance such as a variable capacity capacitor can also be used.

[0019] In the present embodiment, the power transmission coil 51 and the power transmission control section 80 constitute a primary side resonant circuit. When power transmission is performed, the impedance of the closed circuit including the power transmission coil 51 is switched so that the resonant frequency of the circuit becomes a resonant state in which it coincides with or approaches the frequency fl of the main electric power line RFP, and in a state in which power transmission is not performed, that is, in a standby state, the resonant frequency of the circuit is made to deviate from the frequency fl. As a result, the resonant current Ir flowing through the power transmission coil 51 in the resonant state is significantly larger than the standby current Is flowing through the power transmission coil 51 in the standby state. In Figure 3 This is exemplified in the graph. In the graph, the relationship between the frequency at which the impedance of the power transmission circuit is a value that makes the resonant frequency of the circuit fl (here, 85 kHz) and the current flowing through the power transmission coil 51 is shown as Is, and the relationship between the frequency at which the resonant frequency of the circuit is a value different from fl (here, a frequency higher than the frequency fl) and the current flowing through the power transmission coil 51 is shown as Ir. Since the voltage of 85 kHz of the main electric power line RFP is applied to the power transmission circuit, the current Is flowing through the power transmission coil 51 in the standby state is significantly reduced compared to the current Ir flowing through the power transmission coil 51 in the resonant state. Here, the power transmission circuit refers to the circuit constituted by the power transmission coil 51 and the power transmission control section 80, but various circuit elements such as a current sensor are sometimes connected in the power transmission circuit, and the broad "power transmission circuit" refers to a closed circuit through which current flows when power transmission is performed using the power transmission coil 51.

[0020] The principle of using such switching of the impedance, the standby current being small, and performing power transmission on a large electric power at the time of power transmission will be explained using Figure 4 This graph exemplifies how the current flowing through the power transmission coil 51 is converted depending on the position of the power reception coil 31 with respect to the power transmission coil 51. Also, in this example, the power transmission circuit constitutes an LC series resonant circuit. A parallel resonant circuit can also be used, in which case the characteristics are reversed from those illustrated. In the case of using an LC series resonant circuit, even in the case in which the impedance of the power transmission circuit is high and the standby current Is flows through the power transmission coil 51, even in the case in which the impedance of the power transmission circuit is low and the resonant current Ir larger than the standby current Is flows through the power transmission coil 51, and in the case in which the center of the power reception coil 31 overlaps the center of the power transmission coil 51, the current value is the largest, and in the case in which the power reception coil 31 deviates from the center of the power transmission coil 51, it becomes small. This is shown in the upper part (A) of the graph.

[0021] Utilizing this characteristic, conventionally, in a standby state where the power supply circuit has a high impedance (default), when the standby current Is flowing in the standby state exceeds a predetermined conduction threshold Th1, the impedance of the power supply circuit is reduced, and the power supply circuit is brought into a resonant state. In this state, the resonant current Ir flows between the two coils, enabling the transmission of a larger amount of power. Furthermore, when the receiving coil 31 deviates from the center of the power supply coil 51, the resonant current Ir is compared with a predetermined disconnection threshold Th2. If it falls below this threshold, the impedance of the power supply circuit is increased, and the circuit switches to standby mode. Thus, power consumption in the standby state without the receiving coil 31 can be suppressed to a lower level. This situation... Figure 4 It is shown in the lower part (B).

[0022] (A2) Non-contact power supply process: Based on the aforementioned impedance switching, the power supply device 50 and the power receiving device 30 perform... Figure 5 The power supply process is shown. In Figure 5 In, with Figure 2 Corresponding to the structure, the left side represents the processing on the power supply device 50 side, and the right side represents the processing on the power receiving device 30 side. The processing shown in the figure is repeatedly executed by the power supply control unit 80 or the power receiving control unit 40 when the power supply device 50 or the power receiving device 30 is started.

[0023] When the power supply device 50 is started, the power supply control unit 80 sets the power receiving circuit to a standby state (step S110). Specifically, as described above, the circuit impedance is increased, and a standby current Is flows through the circuit. In this state, the power supply control unit 80 determines whether a power supply request has been output from the power receiving device 30 (step S130), and repeats the processing of steps S110 and S130 until a power supply request is received. Of course, if there is no power supply request, this routine can be temporarily terminated, and the processing can be repeated from step S110 after a predetermined time interval.

[0024] An instruction for a power supply request from the power supply device 50 is output from the power receiving device 30 side. When the power receiving device 30 is started, the power receiving control unit 40 repeatedly executes the power receiving side processing shown in the figure. When the power receiving side processing begins, the power receiving control unit 40 first determines whether power is needed (step S210). It determines whether power is needed based on whether there is a request from the load. If a battery is provided and is used as a power source to supply power to the load device 45 such as the drive motor, it can determine whether there is a request from the load based on whether the battery's SOC is below a predetermined threshold. If it is below the threshold, it is determined that power is needed. Of course, regardless of whether there is a battery, it can be determined based on whether the load device 45 requests power. If power is not needed (step S210: "No"), the processing can be repeated, or the routine can be temporarily terminated and the processing can be executed again from step S210 after a predetermined time interval.

[0025] If it is determined that power is needed (step S210: "Yes"), then an instruction to request power supply is output (step S230). At this time, the presence or absence of the power supply device 50 can be detected in advance (step S220), or the power supply request can be output without detecting the presence or absence of the power supply device 50. Detecting the power supply device 50 means detecting whether the power supply coil 51 of the power supply device 50 exists near the power receiving coil 31. For example, using... Figure 4 As shown, when the receiving coil 31 and the supply coil 51 are close together, the current increases even in standby mode. Therefore, the presence of the supply device 50 can be detected based on this increase in current, or by using short-range communication such as Bluetooth (registered trademark) or RFID. However, detecting the supply device 50 is not always necessary. This is because, in response to a power supply request from the receiving device 30, if the supply device 50 is present within the range of the receiving device 30's power supply capability, the supply device 50 will perform the processing described below; otherwise, there will simply be no response to the power supply request. If the presence of the supply device 50 is detected, the reliability of the operation of the contactless power supply system 100 can be verified by judging the action of the supply device 50 in response to the power supply request.

[0026] The power transmission request is output from the power receiving device 30 side, for example, by communication. At this time, if the power transmission device 50 exists in the vicinity of the power receiving device 30 from which the power transmission request is output, the power transmission device 50 judges that the power transmission request exists (step S130: YES). Specifically, the impedance of the power transmission circuit is lowered, and the power transmission processing is performed (step S140). Next, before the time Tt elapses (step S160), the power transmission processing (step S140) is repeated. If the time Tt elapses, the power transmission is ended, the impedance of the power transmission circuit is raised, and the standby state is switched (step S170). Here, the time Tt can be easily detected using a real-time clock or the like. In addition, the total amount of power transmission using the power transmission coil 51, that is, the total amount of power, can be counted, and the power transmission is ended at the earlier one of when the time Tt elapses or when the total amount of power reaches a predetermined value.

[0027] During the power transmission processing performed on the power transmission device 50 side, the power reception processing is performed on the power receiving device 30 side (step S240). The power reception processing can be performed only for the time Tt of the power reception processing of the power transmission device 50, or can be performed until the current of the power reception is lower than a predetermined value. It is assumed that during this period, even if the power reception coil 31 opposes the power transmission coil 51, the power transmission processing on the power transmission device 50 side is ended when the time Tt elapses, and thus the power reception processing does not continue all the time. In addition, the power transmission from the power transmission coil 51 to the power reception coil 31 can be performed using only the magnetic field coupling between the two coils, and can be simple power transmission based on electromagnetic induction, or the resonance frequency of the power transmission circuit or the power reception circuit can be matched with the frequency of the power supplied to the main power line RFP, and power transmission using resonance can be used.

[0028] After the power transmission processing on the power transmission device 50 side is ended, the processing of the reliability check of the power transmission side circuit can be performed (step S190), but can not be performed. Of course, the number of power transmissions or the cumulative power transmission time or the like can be determined in advance, and when the number of power transmissions or the cumulative power transmission time becomes that, it is used as a trigger to perform the reliability check. Of course, in the case where the temperature or the like exceeding a predetermined temperature range is detected by a temperature sensor or the like provided in the power transmission circuit, or the case where a certain phenomenon is detected by a sensor or the like, it is also effective to use it as a trigger to perform the reliability check. Alternatively, these triggers can be combined and the reliability check can be performed. Similarly, on the power receiving device 30 side, the reliability check of the power reception circuit can be performed after the power reception processing (step S240) is ended. The reliability check can be performed or can not be performed, and when it is performed, the timing or the like is the same as the judgment on the power transmission device side, and it is performed by any one trigger or a combination of several triggers.

[0029] A specific circuit structure example of the power transmission device 50 and the power receiving device 30 performing this process will be described. As already explained, the power transmission device 50 includes a power transmission coil 51 and a power transmission control unit 80, and forms a primary resonant circuit. Figure 6 As shown, the power supply control unit 80 includes: a switching unit 53 for switching impedance; a detection unit 55 for detecting the magnitude of the current flowing through the power supply coil 51; and a power supply request detection unit 85 for detecting power supply requests. The switching unit 53 includes two capacitors Cs and Cr connected in series and a switch SW connected in parallel with the capacitors Cs. The switch SW includes two switching elements SW1 and SW2 connected in series and diodes D1 and D2 connected in parallel with each switching element SW1 and SW2. Signal lines from the power supply request detection unit 85 are connected to the gates of the switching elements SW1 and SW2.

[0030] If the start signal SS from the power supply request detection unit 85 is in an off (inactive) state, the switching unit 53 with the above circuit structure sets the switch SW to an off (non-conducting) state. Therefore, the two capacitors Cs and Cr are connected in series. As the switching unit 53, Cts becomes: Cts = 1 / (1 / Cs + 1 / Cr). On the other hand, when the start signal SS from the power supply request detection unit 85 is turned on (activated), the two switching elements SW1 and SW2 become capable of conducting in one direction, and cooperate with the parallel-connected diodes D1 and D2 to achieve a state where current can flow bidirectionally when an AC voltage is applied, i.e., a conducting state. Therefore, if the start signal SS is in the conducting state, there is no effect from the capacitor Cs, and the overall capacitance Ct of the switching unit 53 becomes: Ctr = Cr. That is, the switching unit 53 switches the capacitance of the resonant capacitor connected to the power transmission coil 51, thus functioning as a switching unit that switches the impedance of the circuit through which current flows through the power transmission coil 51 according to the frequency of the AC voltage applied from the main power line RFP. Since the capacitor is connected in series via the switch SW, the relationship between the capacitances Ctr and Cts is: Ctr > Cts.

[0031] In this embodiment, the capacitance Ctr when the start signal SS is turned on, together with the reactance Lr of the power supply coil 51, is set to the resonant frequency fr of the resonant circuit, which is the frequency of the main power line RFP, 85kHz. On the other hand, the capacitance Cts when the start signal SS is turned off causes the resonant frequency fr of the resonant circuit to deviate significantly from 85kHz. In this case, although no resonance occurs, a certain amount of alternating current will still flow because the impedance of the circuit is not infinite. This is the standby current Is. The current when the start signal SS is turned on and resonance occurs is the resonant current Ir. An example of the standby current Is and the resonant current Ir is shown in... Figure 3 As shown in the diagram. In any case, the magnitude of the current is detected by the detection unit 55.

[0032] The function of the power supply request detection unit 85 in the power supply control unit 80 will be explained below along with the structure of the power receiving device 30. An example of the structure of the power receiving device 30 is shown below. Figure 7 As shown in the figure, the power receiving device 30, in addition to the already described power receiving coil 31, power receiving circuit 35, power receiving control unit 40, and load device 45, also includes a power supply request output unit 70. As shown, the power receiving coil 31 and capacitor CC1 form a series resonant circuit. The alternating current generated in the resonant circuit is rectified by a diode bridge consisting of four diodes RD1-RD4 provided in the power receiving circuit 35 and output to the load device 45. The load of the load device 45, such as the state of charge (SOC), is monitored by the power receiving control unit 40.

[0033] The power receiving request output section 70 of the power receiving device 30 includes a sub-coil 71 that forms a magnetic field coupling in the case where the power transmission coil 51 is in the vicinity, a resonance capacitor CC2, a solid state relay 74 operated by the power receiving control section 40, and the like. In the figure, only the contacts of the solid state relay 74 are shown. The contacts of the solid state relay 74 are in an open state by default, in which state a current does not flow through the circuit of the power receiving request output section 70. When the power receiving control section 40 that detects the state of the load device 45 determines that power reception should be performed, outputs a power reception request signal RS to the power receiving request output section 70, drives the solid state relay 74, and closes the contacts thereof, the circuit of the power receiving request output section 70 becomes a closed circuit. The resonance frequency of the series resonance circuit composed of the sub-coil 71 and the resonance capacitor CC2 is 85 kHz. In this state, if the power transmission coil 51 is present in the vicinity of the sub-coil 71, a current flows through the closed circuit of the power receiving request output section 70 due to the magnetic field coupling of the power transmission coil 51 and the sub-coil 71, as a result of which the current flowing through the power transmission coil 51 also increases. In the power transmission device 50, the magnitude of the current flowing through the power transmission coil 51 is detected by the detection section 55, and therefore the power reception request detection section 85 judges an increase in the current from the standby current Is, outputs a start signal SS to the switching section 53, thereby switching the impedance of the switching section 53 to a low value and causing a resonance current Ir to flow, and power transmission via the power transmission coil 51 and the power receiving coil 31 is performed for a prescribed time Tt, after which the power transmission is ended.

[0034] This situation is shown in Figure 8 Fig. 6. As shown in the figure, in the state where the power transmission coil 51 and the power receiving coil 31 are in magnetic field coupling, when the power reception request signal RS is turned on at the power receiving device 30 side, the current Is flowing through the power transmission coil 51 increases, and as a result of the power reception request detection section 85 detecting this state, the switching section 53 is switched from the standby state in which the impedance is high to the resonance state in which the impedance is low, and the current Ir flowing through the power transmission coil 51 rapidly increases. As a result, the power transmission device 50 side becomes a state in which the power transmission process is performed (step S140), and the power receiving device 30 side becomes a state in which the power reception process is performed (step S240). Figure 5 Figure 5

[0035] The power transmission process at the power transmission device 50 side is ended after the time Tt elapses, regardless of the magnitude of the current Ir. As a result, the switching section 53 of the power transmission device 50 is switched to a high impedance, the power transmission circuit becomes the standby state, and the current flowing through the power transmission coil 51 also becomes the standby current Is. Subsequently, this state continues until the power reception request signal is output from the power receiving device 30 side. During this period, the power receiving device 30 and the power transmission device 50 can also perform a process for checking reliability. After this, if the power reception request is output from the power receiving device 30 side in view of the state of the load device 45 or the like, the above-described operation and the power transmission and power reception processes are performed again.​​

[0036] In the power transmitting device 50 and the power receiving device 30 described above, the power transmission request signal RS is turned off after a predetermined time after being turned on temporarily. This is because the power transmission request signal RS is turned on by the power receiving control section 40 determining the pulse width of the power transmission request signal RS, and the power transmission request signal RS is turned off by the power receiving control section 40. In contrast, the power receiving control section 40 can also be controlled to turn off the power transmission request signal RS after turning on the power transmission request signal RS temporarily, and after confirming that the power receiving process is started and the power transmission of the power of the threshold value or more is started. Such a process has the following advantage: in the case where the mobile body 20 moves, and the output of the power transmission request signal RS is performed without detecting whether the power receiving coil 31 approaches the power transmitting coil 51, it is not necessary to output the power transmission request signal RS multiple times in order to start the power transmission.

[0037] In the non-contact power feeding system 100 of the first embodiment described above, the power transmitting device 50 does not start the power transmission in accordance with the size of the current flowing through the power transmitting coil 51 to detect the presence of the power receiving coil 31, but starts the power transmission by accepting the power transmission request from the power receiving device 30 side, and ends the power transmission after a predetermined time Tt elapses. Therefore, even in the case where the current flowing through the power transmitting coil 51 is larger than the value at the time of design due to a deviation of the power transmission circuit or the power receiving circuit, or the like, and the state where the magnetic field coupling of the power receiving coil 31 and the power transmitting coil 51 is released cannot be detected, the power transmitting device 50 does not continue the power transmission, and the unnecessary current does not flow. In addition, even in the case where a certain failure occurs on the power receiving device 30 side, and the state where the power transmission is not desired to be continued is caused, the power transmission is continued. This is because the power transmitting device 50 ends the power transmission if the predetermined time Tt elapses. Therefore, even in the case where an operation other than the transmission and reception of the power transmission request is performed between the power receiving device 30, the power transmission of the power that should not be transmitted can be avoided. As a result, the small power can be assisted, and the failure on the power receiving device 30 side can be coped with. As the failure on the power receiving device 30 side, for example, a case where a battery becomes overcharged in the case where the battery is installed, a temperature rise exceeding the rated temperature on the power receiving device 30 side, and the like can be considered.

[0038] In the present embodiment, if the power transmission request signal RS is outputted, the power transmitting device 50 starts the power transmission. In the case where the power transmission request signal RS is not outputted, the power transmitting device 50 does not start the power transmission. In the case where the power transmission request signal RS is outputted, the power transmitting device 50 starts the power transmission. In the case where the power transmission request signal RS is not outputted, the power transmitting device 50 does not start the power transmission. Figure 5The power supply device detection process in step S220 of the illustrated process prevents unnecessary power supply requests from being output when the power receiving device 30 is not in a position close to the power supply device 50. Furthermore, if a reliability check process (step S290) is performed after the power receiving process (step S240) ends, the reliability of the device can be confirmed during periods when no power receiving process is performed. Therefore, the reliability of the device receiving power is easily ensured. Similarly, if a reliability check process (step S190) is performed after the power supply process (step S170) ends, the reliability of the device can be confirmed during periods when no power supply process is performed, and the reliability of the device supplying power is easily ensured.

[0039] In the above embodiment, since the power supply request is output by magnetic coupling with the power supply coil 51, no communication device or other equipment is required, which simplifies the structure of the power supply device 50 and the power receiving device 30. Furthermore, there is no need to prepare a power supply specifically for the power supply request output section 70, which further simplifies the structure.

[0040] B. Second implementation method: Next, the contactless power supply system 100 of the second embodiment will be described. The overall structure of the contactless power supply system 100 of the second embodiment is similar to... Figure 1 The first embodiment is the same. In the contactless power supply system 100 of the second embodiment, the power supply device 50 has the same structure as the first embodiment. Figure 9 The structure of the power receiving device 30A according to the second embodiment is shown. As shown, the power receiving circuit of this power receiving device 30A is the same as that of the first embodiment, except for three aspects: the current sensor 37 that detects the current value Ii flowing through the power receiving circuit, the power supply coil detection unit 90, and the power supply request output unit 70A. In this embodiment, the power receiving control unit 40A also reads the state of the load device 45 and outputs a power supply request signal RS.

[0041] The power supply coil detection unit 90, installed in the power receiving device 30A, is for detecting the presence of the power supply coil 51. The power supply coil detection unit 90 includes a detection coil 91, a detection circuit 92, a determination circuit 93, and a drive circuit 95. The detection circuit 92 detects the current flowing through the detection coil 91. Furthermore, the determination circuit 93 determines the presence of the power supply coil 51 near the detection coil 91 based on the magnitude of the current detected by the detection circuit 92. When the determination circuit 93 determines that the power supply coil 51 is near and present, the drive circuit 95, upon receiving a power supply request signal RS from the power receiving control unit 40A, outputs a drive signal to the inverter 75 within a predetermined period.

[0042] The power-receiving request output section 70A in the power-receiving device 30A includes a resonance circuit composed of the sub-coil 71 and the resonance capacitor CC2, and includes an inverter 75 between the resonance circuit and a direct-current power supply 77. Four switching transistors Tr1-Tr4 that constitute the inverter 75 form a bridge, and an output signal from a drive circuit 95 of a power-coil detection section 90 described later is connected to the gate terminals thereof. Of the four switching transistors Tr1-Tr4, two switching transistors Tr1 and Tr4, Tr2 and Tr3 that are diagonally arranged are exclusively turned on and off, and an alternating-current voltage of 85 kHz is applied to the resonance circuit. At this time, if the power-coil 51 of the power-receiving device 50 exists in the proximity, the sub-coil 71 is magnetically coupled thereto, and thus the current flowing through the power-coil 51 is increased. This functions as a power-receiving request to the power-receiving device 50.

[0043] The power-receiving control section 40A in the power-receiving device 30 in the second embodiment performs the power-receiving-side processing using the flowchart shown in Figure 10 The power-transmitting control section 80 of the power-transmitting device 50 performs the power-transmitting-side processing using the flowchart shown in Figure 11 The power-receiving control section 40A repeatedly performs the processing routine shown in Figure 10 First, the power-receiving control section 40A acquires the load request in the load device 45 (step S310), and judges whether or not power reception from the power-transmitting device 50 should be performed in accordance with the state of the load (step S315). When it is judged that power reception is required (step S315: YES), the current value Ii flowing through the power-receiving circuit is then acquired from the current sensor 37 (step S320), and it is judged whether or not power reception from the power-transmitting device 50 has been performed based on the current value Ii (step S325). If it cannot be judged that the current value Ii is small and that power reception is in progress, the power-receiving control section 40A sets the power-transmitting request signal RS to on (step S340). Thereafter, the output of the current sensor 37 is read, and the current value Ii flowing through the power-receiving circuit is acquired (step S350), it is judged whether or not the current value Ii is larger than a judgment threshold value Thr that is set in advance (step S355), and these processes (steps S350, S355) are repeated until Ii > Thr.

[0044] With respect to the above-described operation of the power-receiving device 30, the power-transmitting device 50 performs the following processing and judgment. The power-transmitting device 50 performs the following processing and judgment after startup, as shown in Figure 11As shown, the switching section 53 is switched and becomes a state in which the impedance of the power transmission circuit is high, i.e., a standby state (step S410), and the current value It flowing through the power transmission coil 51 is acquired from the detection section 55 (step S420). On the basis of this, it is judged whether or not the current value It is greater than a predetermined judgment threshold Ths (step S430), and if it is not greater than the judgment threshold Ths, the processing returns to step S410 and the above-described processing is repeated. During this period, when the power reception control section 40A of the power reception device 30A sets the power transmission request signal RS to ON and increases the standby current flowing through the power transmission coil 51 via the power transmission request output section 70A, the current value It exceeds the judgment threshold Ths (step S430: "Yes").

[0045] Upon receiving this judgment, the power transmission control section 80 reduces the impedance of the switching section 53, and switches to a power transmission state in which the resonance current Ir can flow (step S440). As a result of this, the magnetic field coupling using the power transmission coil 51 and the power reception coil 31 is used, and power transmission by resonance is started, and the currents flowing through the power transmission coil 51 and the power reception coil 31 both increase. The power transmission control section 80 of the power transmission device 50 repeats this state until the elapse of time Tt (step S450). At the elapse of time Tt, the power transmission control section 80 returns to step S410, increases the impedance of the switching section 53, and switches to the standby state.

[0046] At the point in time at which the power transmission request signal RS is output, if the power transmission coil 51 of the power transmission device 50 approaches the power reception coil 31, as described above, the drive circuit 95 of the power transmission request detection section 90 drives the inverter 75 of the power transmission request output section 70A, and therefore, the power transmission control section 80 of the power transmission device 50 detects the power transmission request from the fact that the current value It flowing through the power transmission coil 51 exceeds the judgment threshold Ths, reduces the impedance of the switching section 53, and switches the resonance frequency to 85 kHz. As a result of this, the impedance of the power transmission circuit becomes small, and the resonance current Ir flows, and therefore, the current value Ii detected by the current sensor 37 also increases.

[0047] Therefore, if the power reception control section 40A of the power reception device 30A repeats steps S350 and S355, the current value Ii will eventually become greater than the judgment threshold Thr (step S355: "Yes"), and the power reception control section 40A sets the power transmission request signal RS to OFF (step S360). In addition, it is also conceivable that the situation in which the current value Ii does not exceed the judgment threshold Thr continues even if the mobile body 20 moves due to some reason, but in this case, as long as the time during which the loop of steps S350 to S355 continues is measured, the power transmission request signal RS is set to OFF by timeout, and the present processing routine ends.

[0048] After the power request signal RS is set to off, power receiving processing is performed (step S370), and this processing routine is temporarily terminated. Since this processing routine is executed repeatedly at predetermined time intervals, if power receiving is required based on the load request, processing and judgment are performed in the order of steps S310, S315, S320, S325, and S370, and power receiving processing continues. On the other hand, if power receiving is not required based on the load request (step S315: "No"), nothing is performed, the process stops, and this processing routine ends. In this embodiment, no special action is taken if there is no power receiving request midway through the power receiving process; however, even in this case, if a predetermined time Tt has elapsed since power supply began through the power supply device 50 that received the power request, the power supply implemented by the power supply device 50 is stopped. Of course, the diodes constituting one arm of the power receiving circuit 35, such as diodes RD1 and RD3, can also be replaced with switching elements. If power is not required from the perspective of load demand, the switching elements are set to open, and the power receiving process is terminated.

[0049] In the contactless power supply system 100 of the second embodiment described above, while achieving the same functional effects as the first embodiment, since a power supply coil detection unit 90 is provided in the power receiving device 30, it is possible to request power supply to the power supply device 50 after confirming that the power supply device 50 is approaching. Furthermore, after the power receiving control unit 40 sets the power supply request signal RS to be turned on, it sets the power supply request signal RS to be turned off after confirming the start of power supply from the power supply device 50 to the power receiving device 30A by measuring the current value Ii flowing through the power receiving coil 31. Therefore, it is possible to reliably send a power supply request to the power supply device 50.

[0050] C. Third implementation method: Next, the contactless power supply system 100 of the third embodiment will be described. For example... Figure 12 As shown, the contactless power supply system 100 of the third embodiment includes a power supply device 50B and a power receiving device 30B. The power supply device 50B and the power receiving device 30B have the same structure as in the first embodiment; however, in order to notify the power supply device 50B of a power supply request from the power receiving device 30B, magnetic field coupling between the power supply coil 51 and the power receiving coil 31 is not utilized, but rather a notification implemented through communication. For such communication, the power receiving device 30B includes a power supply request transmitting unit 79, and the power supply device 50B includes a receiving unit 89. The power supply request transmitting unit 79 and the receiving unit 89 communicate using Bluetooth (registered trademark). The communication method is not limited to this; other methods such as optical communication or WiFi can also be used.

[0051] The power transmission request transmitting section 79 outputs a signal requesting power transmission when it receives the power transmission request signal RS output from the power reception control section 40. If the power transmission device 50B exists within the output range of this signal, the receiving section 89 of the power transmission device 50B receives the signal requesting power transmission and passes it to the power transmission control section 80. The power transmission control section 80 lowers the impedance of the power transmission circuit for a prescribed time Tt and performs power transmission using resonance between the power transmission coil 51 and the power reception coil 31. If the prescribed time Tt elapses, the power transmission control section 80 raises the impedance of the power transmission circuit regardless of the presence or absence of resonance current and ends power transmission using resonance. If a request for power transmission exists in the power reception device 30B, the signal requesting power transmission is again sent to the power transmission device 50B side via the power transmission request transmitting section 79, and if the receiving section 89 receives this signal, power transmission is performed in the same manner.

[0052] In the non-contact power transmission system 100 of the third embodiment having this structure, the same effects as being able to perform non-contact power transmission and the like are achieved as in the first and second embodiments. Moreover, in the third embodiment, since the power transmission coil 51 and the power reception coil 31 are not used in the transmission and reception of the power transmission request, the timing of transmission and reception of the power transmission request signal using resonance does not need to be considered, and the design freedom of the two coils 51 and 31 can be improved. In addition, the possibility of erroneously determining noise between the two coils as a power transmission request can be eliminated.

[0053] In each of the above embodiments, if a situation exists in which power transmission is requested from the power reception device 30 side, such as a situation in which the SOC of the battery decreases, the power transmission request is repeatedly output, but the time interval during which the power transmission request can be output can be limited. For example, the time interval during which the power transmission request can be output can be made longer than the prescribed time Tt during which the power transmission device 50 continues power transmission, and the time during which power transmission using resonance is not performed can be ensured to be a certain time or more. In this way, the temperature rise accompanying power transmission of the two coils 51 and the power reception coil 31 can be moderated. In addition, the time required for processing for confirming the reliability of each device and the like can be easily ensured. In addition, from the viewpoint of temperature rise and the like, a condition can be set for the number of times the power transmission request is repeated. For example, it can be configured such that if the power reception device 30 side outputs the power transmission request ten times or more within a prescribed time interval, the next power transmission request is not allowed to be output for a time longer than this time interval, or even if the power transmission request is output from the power reception device 30, the power transmission device 50 does not accept the power transmission request for a certain time.

[0054] D. Modified Example: In the above embodiments, the time Tt from receiving a power supply request from the power receiving device 30 side to the power supply device 50 side terminating power supply is set to a predetermined time, but this time Tt can also vary depending on the power supply conditions. Such variations 1 to 3 are described below. In each variation, the processing routine on the power supply device 50 side of the second embodiment ( Figure 11 In ), time Tt is determined in the following way.

[0055] In variation example 1, such as Figure 13 As shown, between steps S430 and S440, a process is performed to set the time Tt until the power supply is terminated based on the current value It flowing through the power supply coil 51. Specifically, if the determination in step S430 is "yes", the impedance of the switching unit 53 is first reduced to enter the power supply state (step S510). Then, the current value It flowing through the power supply coil 51 in the power supply state is obtained (step S511). Based on this, a predetermined time Tt until the power supply state ends is set based on this current value It (step S512). By performing this process, the predetermined time Tt is determined based on the current value It when the power supply state is entered. Here, the larger the current value It flowing through the power supply coil 51 when the power supply state is entered, the larger the time Tt is. However, the predetermined time Tt must be set to a finite value. The relationship between the current value It and the predetermined time Tt can be obtained by mathematical formula, or it can be prepared in advance in the form of a table and obtained by looking up the table.

[0056] According to this modified example 1, when the current value It flowing through the power supply coil 51 is large when it is in the power supply state, the time Tt until the power supply ends is set to be long, and when it is small, it is set to be short. Therefore, the specified time Tt can be set to an appropriate length. That is, when power supply begins when the power supply coil 51 and the receiving coil 31 are facing each other, the power supply duration Tt can be extended, and the decrease in average power supply can be suppressed. On the other hand, when power supply begins when the power supply coil 51 and the receiving coil 31 can supply power but are relatively far apart, since the power supply duration Tt is shortened, the time for continuous magnetic flux emission from the power supply coil 51 when the receiving coil 31 is far away can be shortened.

[0057] In variation example 2, such as Figure 14As shown, between step S430 and step S440, the process of setting the time Tt until termination of power transmission based on the output current value Im supplied from the main power supply device 60 to the power transmission device 50 is performed. Specifically, in the case where the determination in step S430 is "Yes", first, the impedance of the switching section 53 is reduced to become the power transmission state (step S510), and thereafter, the output current value Im output from the main power supply device 60 to the power transmission device 50 in the power transmission state is acquired (step S515). The output current value Im can use the detection value of the current sensor for overcurrent detection provided in the inverter of the main power supply device 60. The prescribed time Tt until the end of the power transmission state is set based on the output current value Im (step S516). By performing this process, the prescribed time Tt is determined in accordance with the output current value Im when becoming the power transmission state. Here, the greater the output current value Im output to the power transmission device 50 when becoming the power transmission state, the greater the time Tt. The time Tt is set to a finite value, the relationship between the output current value Im and the prescribed time Tt is found using a mathematical expression or a table, and the like are the same as in Modification 1.

[0058] According to this Modification 2, in the case where the output current value Im output to the power transmission device 50 when becoming the power transmission state is greater, the time Tt until termination of power transmission is set to be long, and in the case where it is smaller, it is set to be short, and thus, it is possible to set the prescribed time Tt to an appropriate length. Since there is a strong correlation between the output current value Im and the current value flowing through the power transmission coil 51, in this Modification 2, the same effects of suppressing reduction of the average power supply, suppressing unnecessary radiation of the magnetic flux from the power transmission coil 51 in the state where the power reception coil 31 is distanced, and the like as in Modification 1 are exerted.

[0059] In Modification 3, as shown, Figure 15 between step S430 and step S440, the process of setting the time Tt until termination of power transmission based on the moving speed v of the moving body 20 is performed. Specifically, in the case where the determination in step S430 is "Yes", first, the moving speed v of the moving body 20 is detected (step S520), and thereafter, the prescribed time Tt until the end of the power transmission state is set based on the moving speed v of the moving body 20 (step S521). By performing such a process, the prescribed time Tt is determined in accordance with the time when the power reception coil 31 of the moving body 20 is assumed to be opposed to the power transmission coil 51. Here, the smaller the moving speed v of the moving body 20, the longer the time when the two coils are in the state of magnetic field coupling can be considered, and thus, the greater the time Tt. The time Tt is set to a finite value, the relationship between the moving speed v and the prescribed time Tt is found using a mathematical expression or a table, and the like are the same as in Modifications 1 and 2.

[0060] According to this modification 3, the time Tt until the power feeding ends is set to be long in the case where the moving speed is small, and is set to be short in the case where the moving speed is large, so that the prescribed time Tt can be set to an appropriate length. In this modification 3, it is presumed that the time during which the power feeding coil 51 and the power receiving coil 31 are in the aligned or power-supplyable arrangement is longer when the moving speed v is small, so that the decrease in the average power supply amount can be suppressed. On the other hand, when the moving speed v is large, it is presumed that the power feeding device 50 and the power receiving coil 31 are separated in a short time, so that the unnecessary emission of the magnetic flux from the power feeding coil 51 in the state where the power receiving coil 31 is far away can be suppressed.

[0061] E. Other Embodiments (1) The present application can also be implemented by the following method. The first method is a structure of a non-contact power feeding system that performs power feeding from a power feeding device to a power receiving device by magnetic field coupling. In this non-contact power feeding system, the power receiving device outputs a power feeding request signal that requests power feeding, and the power feeding device, upon receiving the power feeding request signal, switches to a standby state in which the power feeding amount is less than that in a power feeding period after performing power feeding using the magnetic field coupling for the power receiving device during the power feeding period. In this way, the power feeding from the power feeding device is performed in response to the power feeding request signal from the power receiving device, and after the lapse of the predetermined power feeding period, the power feeding device switches to the standby state in which the power feeding amount is less than that in the power feeding period. Therefore, the power feeding from the power feeding device to the power receiving device using the magnetic field coupling does not continue beyond the power feeding period, and it is possible to avoid or suppress a situation in which power feeding continues with a large power feeding amount despite the fact that it is not desirable to continue power feeding for some reason.

[0062] Here, the power feeding from the power feeding device to the power receiving device can be power feeding using magnetic field coupling, and can be power feeding using resonance or power feeding not using resonance. Also, the power feeding amount in the standby state can be less than that in the power feeding period, or power feeding can not be performed in the standby state. The state in which it is not desirable to continue power feeding can include a state in which the magnetic field coupling is insufficient, a state in which it is not desirable to continue power receiving on the power receiving device side, and the like. The latter can include a case where an electric storage device such as a secondary battery or a capacitor charged by power received by the power receiving device is in a state where it cannot store power any more, a case where an abnormality occurs in a circuit for power receiving, and the like. As such an abnormality, there are a case where overheating of a prescribed temperature or more is detected, a case where overcurrent of a prescribed value or more is detected, a case where a power receiving stop instruction is issued from a diagnosis system on the power receiving device side, and the like.

[0063] (2) In the structure of (1) described above, it can also be that the power transmitting device does not perform power transmission using the magnetic field coupling in the standby state described above. In this case, since power transmission is stopped, it is possible to further suppress the occurrence of failures accompanying power transmission. Failures accompanying power transmission include an undesirable temperature rise on the power receiving device side, undesirable overcharging, unnecessary power consumption on the power transmitting device side, and the like.

[0064] (3) In the structure of (1) or (2) described above, it can also be that the power receiving device outputs the power transmission request signal to the power transmitting device using the magnetic field coupling. In this case, since it is possible to output the power transmission request signal using the magnetic field coupling, it is possible to simplify at least a part of the structure for outputting the power transmission request signal. The power transmission request signal using the magnetic field coupling can be output by changing the magnitude of the current flowing through the magnetic field coupling. The change in the magnitude of the current can be determined by detecting the current value, but is not limited to the current value, and can also be determined by detecting a change in the voltage generated in a portion through which the current flows, such as a power transmission coil or the like, the voltage across a capacitor forming a resonance circuit in the case where a resonance circuit is formed, the current flowing through the capacitor constituting the resonance circuit, or the like. Alternatively, it can also be determined by detecting a change in the magnetic flux generated by the flowing current.

[0065] (4) In the structure of (1) to (3) described above, it can also be that the power transmitting device includes a primary side resonance circuit constituted by a power transmission coil and a first capacitor, and an alternating current power supply device that applies an alternating voltage of a prescribed frequency to the primary side resonance circuit to supply power, and the power receiving device includes a secondary side resonance circuit constituted by a power receiving coil and a second capacitor, and a rectification circuit that rectifies an alternating current induced in the secondary side resonance circuit to a direct current, and the power transmission coil and the power receiving coil form the magnetic field coupling. In this case, it is possible to achieve wireless power supply with high efficiency with a simple structure. The primary side resonance circuit or the secondary side resonance circuit can adopt any one of various structures well known as a series resonance circuit constituted by a coil and a capacitor, or any one of various structures well known as a parallel resonance circuit.

[0066] (5) In the structure of (4) described above, it can also be that the power receiving device has a signal output portion that outputs the power transmission request signal via the power receiving coil and the power transmission coil of the magnetic field coupling, and the power transmitting device has a power transmission request detection portion that detects the power transmission request signal based on a change in the amount of electricity in the power transmission coil. In this case, it is possible to output the power transmission request signal from the power receiving device to the power transmitting device with a simple structure. The change in the amount of electricity can be detected by a change in the magnitude of the current flowing through the power transmission coil, a change in the voltage of the power transmission coil, or the like.

[0067] (6) In the structure of (4) or (5) described above, the power transmitting device can have a switching section that switches the power transmission amount between the power transmission coil and the AC power supply device. This makes it possible to easily switch the amount of power that can be transmitted during power transmission and the amount of power that can be transmitted in the standby state. The switching of the power transmission amount can be achieved by switching a contact that connects or disconnects a circuit that performs power transmission, switching the magnitude of the impedance of the circuit, or the like. The switching can be achieved by fixedly switching the state from on to off, from off to on, or by changing the ratio of the on time and the off time, that is, the duty ratio of the on and off.

[0068] (7) In the structure of (4) to (6) described above, the switching section can include a switching circuit that switches the capacity of the first capacitor from a first value to a second value, and the resonance frequency of the primary-side resonance circuit when the capacity of the first capacitor is the second value is farther from the prescribed frequency of the AC voltage than when the capacity of the first capacitor is the first value. This makes it possible to easily switch whether the resonance frequency of the primary-side resonance circuit is close to or far from the frequency of the AC voltage, and to change the degree of power transmission that utilizes resonance. The change in the capacity of the capacitor can be easily achieved by switching a plurality of capacitors, switching the parallel or series connection, or the like. If the resonance frequency of the primary-side resonance circuit coincides with the frequency of the AC voltage during power transmission, it is advantageous in terms of improving the efficiency of power transmission, but it can also be slightly different, as long as it is close to the frequency of the AC voltage compared to the standby state. In addition, the resonance frequency of the primary-side resonance circuit can be switched by changing the inductance of the power transmission coil, rather than changing the capacity of the capacitor. Such switching of the inductance can be easily achieved by providing a tap in the middle of the power transmission coil, switching the tap, or changing the number of windings. Of course, it can also be achieved by providing the power transmission coil with a core portion and changing the permeability of the power transmission coil by changing the overlap of the core portion and the winding.

[0069] (8) In the structure of (1) to (7) described above, the power transmitting device can include a parameter detection section that detects a parameter that reflects the power transmission amount during the power transmission period, and sets the power transmission period based on the parameter. This makes it possible to set the power transmission period based on a parameter that reflects the power transmission amount, and to achieve, for example, suppression of a decrease in the average power supply, suppression of unnecessary radiation of magnetic flux, or the like. As the parameter, there are the power transmission amount at the start of the power transmission period, for example, the current value flowing through the power transmission coil, the amount of power supplied to the power transmission device by the power supply circuit, or the like.

[0070] (9) In the structure of (1) to (8) described above, it can also be that the power receiving device repeatedly outputs the power transmission request signal at a predetermined time interval in a case where a predetermined condition is satisfied. In this way, even if a period of interruption is sandwiched, non-contact power feeding can be continued in a state in which power feeding is possible. The predetermined condition refers to a condition in which power transmission is requested from the power receiving side and there is no obstacle to power reception.

[0071] (10) In the structure of (9) described above, it can also be that, in a case where an abnormality is present in the power receiving device, the power receiving device determines that the predetermined condition is not satisfied. In this way, even if an abnormality is present in the power receiving device, it is possible to suppress the possibility of implementing power transmission.

[0072] (11) In the structure of (1) to (10) described above, it can also be that at least one of the power receiving device and the power transmission device implements a check related to the safety of the device in a period from when the power transmission period ends until a next power transmission request signal is output from the power receiving device. In this way, it is possible to satisfy the requirements of the safety of the device and the continuation of power feeding.

[0073] (12) In the structure of (1) to (11) described above, it can also be that the power receiving device is installed in a moving body that moves relative to the power transmission device, and the length of the power transmission period is determined in advance based on an average time of receiving power transmission from the power transmission device while the moving body is moving. In this way, it is possible to implement power transmission based on the average time required for the moving body to pass the power transmission device to determine the amount of power transmission that is possible, and it is possible to achieve, for example, suppression of a decrease in average power feeding, suppression of unnecessary radiation of magnetic flux, and the like.

[0074] (13) Another aspect of the present disclosure is a non-contact power transmission device that transmits power to a power receiving device by magnetic field coupling. The non-contact power transmission device, upon receiving a power transmission request signal from the power receiving device, performs first power transmission using the magnetic field coupling with the power receiving device for a predetermined power transmission period, and after the power transmission period, switches to a power transmission state in which the amount of power transmission is less than the first power transmission. In this way, the non-contact power transmission device, after the power transmission period, becomes a power transmission state in which the amount of power transmission is less than the first power transmission, and does not continue non-desired power transmission in which the amount of power transmission is large without purpose.

[0075] (14) Another aspect of the present application is a non-contact power receiving device that receives power transmitted from a power transmitting device by magnetic field coupling. The non-contact power receiving device outputs a power transmission request signal requesting power transmission to the power transmitting device described above, and the power transmitting device that receives the power transmission request signal described above performs first power transmission using the magnetic field coupling described above with respect to the power receiving device in a predetermined power transmission period, and after the power transmission period, after switching to a power transmission state in which the amount of power transmission is less than that of the first power transmission, outputs the power transmission request signal again in a case where a prescribed condition is satisfied. In this way, as long as the non-contact power receiving device does not output the power transmission request signal, the power transmission period ends at the predetermined period, and thus the non-contact power receiving device does not continue power reception aimlessly, and if power reception is required, power reception can be continued even with an interruption period sandwiched in between.

[0076] (15) Another aspect of the present application is a non-contact power transmission method that transmits power from a power transmitting device to a power receiving device by magnetic field coupling. In the non-contact power transmission method, the power receiving device outputs a power transmission request signal requesting power transmission, and in a case where the power transmission request signal is received by the power transmitting device, power transmission using the magnetic field coupling described above with respect to the power receiving device is performed in a predetermined power transmission period, and after the end of the power transmission period, the power transmitting device switches to a power transmission state in which the amount of power transmission is less than that of the power transmission period. In this way, power transmission from the power transmitting device is performed in response to the power transmission request signal from the power receiving device, and after the predetermined power transmission period, switching is performed to a standby state in which the amount of power transmission is less than that of the power transmission period. Thus, power transmission from the power transmitting device to the power receiving device using the magnetic field coupling is not performed beyond the power transmission period, and it is possible to avoid or suppress a situation in which power transmission continues with a large amount of power transmission despite the fact that it is not desirable to continue power transmission for some reason.

[0077] The control section and the method thereof according to the present disclosure can also be realized by a special-purpose computer provided by a processor programmed to execute one or more functions embodied by a computer program, or a special-purpose computer provided by a processor composed of one or more special-purpose hardware logic circuits. Alternatively, the control section and the method thereof according to the present disclosure can be realized by a special-purpose computer provided by a processor composed of one or more special-purpose hardware logic circuits, or a special-purpose computer provided by a processor composed of one or more special-purpose hardware logic circuits and a processor programmed to execute one or more functions. Further, the computer program can be stored in a computer-readable non-transitory tangible recording medium as instructions to be executed by a computer. The "computer-readable non-transitory tangible recording medium" is not limited to a portable recording medium such as a floppy disk or a CD-ROM, but also includes various RAMs or ROMs or the like in a computer system, and a hard disk or the like as an external storage device of a computer. That is, the "computer-readable non-transitory tangible recording medium" has a broad meaning including any recording medium that can fix data packets, not a temporary arbitrary recording medium.

[0078] The present disclosure is not limited to the above-described embodiments, and can be realized by various structures without departing from the scope of the above-described gist. For example, the technical features in the embodiments corresponding to the technical features in each of the modes described in the summary of the application can be appropriately replaced or combined to solve part or all of the above-described technical problems or achieve part or all of the above-described effects. Further, the above-described technical features can be appropriately deleted as long as they are not described as essential structures in the present specification.

Claims

1. A non-contact power feeding system that performs power feeding from a power feeding device (50, 50B) to a power receiving device (30, 30A, 30B) through magnetic field coupling, the power receiving device outputs a power feeding request signal that requests power feeding, the power feeding device switches to a stand-by state in which the amount of power feeding is less than that in a power feeding period (Tt) after power feeding using the magnetic field coupling with the power receiving device is performed for the predetermined power feeding period upon receiving the power feeding request signal.

2. The non-contact power feeding system according to claim 1, wherein the power feeding device does not perform power feeding using the magnetic field coupling in the stand-by state.

3. The non-contact power feeding system according to claim 1, wherein the power receiving device outputs the power feeding request signal to the power feeding device using the magnetic field coupling.

4. The non-contact power feeding system according to claim 1, wherein the power feeding device includes: a primary side resonant circuit that has a power feeding coil (51) and a first capacitor (Cs, Cr); and an alternating current power supply device (60) that applies an alternating current voltage of a prescribed frequency to the primary side resonant circuit to supply power, the power receiving device includes: a secondary side resonant circuit that has a power receiving coil (31) and a second capacitor (CC1); and a rectification circuit (35) that rectifies an alternating current induced in the secondary side resonant circuit to a direct current, the power feeding coil and the power receiving coil form the magnetic field coupling.

5. The non-contact power feeding system according to claim 4, wherein the power receiving device includes a signal output section (70) that outputs the power feeding request signal via the power receiving coil and the power feeding coil of the magnetic field coupling, the power feeding device includes a power feeding request detection section (85) that detects the power feeding request signal based on a change in the amount of power in the power feeding coil.

6. The non-contact power feeding system according to claim 4, wherein the power feeding device includes a switching section (80) that switches the amount of power between the power feeding coil and the alternating current power supply device.

7. The non-contact power feeding system according to claim 6, wherein the switching section includes a switching circuit (53) that switches the capacity of the first capacitor from a first value to a second value, the resonant frequency of the primary side resonant circuit when the capacity of the first capacitor is the second value being further away from the prescribed frequency of the alternating current voltage than when the capacity of the first capacitor is the first value.

8. The non-contact power feeding system according to claim 1, wherein the power feeding device includes a parameter detection section (55) that detects a parameter that reflects the amount of power in the power feeding period, the power feeding period is set based on the parameter.

9. The non-contact power feeding system according to claim 1, wherein The power receiving device repeatedly outputs the power transmission request signal at a predetermined time interval if a predetermined condition is satisfied.

10. The contactless power transmission system according to claim 9, wherein The power receiving device determines that the predetermined condition is not satisfied if an abnormality is present in the power receiving device.

11. The contactless power transmission system according to claim 1, wherein At least one of the power receiving device and the power transmission device performs a check related to the safety of the device during a period from after the end of the power transmission to until a next power transmission request signal is output from the power receiving device.

12. The contactless power transmission system according to claim 1, wherein The power receiving device is provided to a moving body (20) that moves relative to the power transmission device, The length of the power transmission period is predetermined in accordance with an average time of receiving power transmission from the power transmission device while the moving body is moving.

13. A contactless power transmission device that performs power transmission to a power receiving device through magnetic field coupling, Upon receiving a power transmission request signal from the power receiving device, performs first power transmission using the magnetic field coupling for the power receiving device for a predetermined power transmission period, After the power transmission period, switches to a power transmission state in which the amount of power transmission is less than the first power transmission.

14. A contactless power receiving device that performs power reception of power transmitted from a power transmission device through magnetic field coupling, Outputs a power transmission request signal that requests power transmission to the power transmission device, The power transmission device that receives the power transmission request signal performs first power transmission using the magnetic field coupling for the contactless power receiving device for a predetermined power transmission period, after the power transmission period, switches to a power transmission state in which the amount of power transmission is less than the first power transmission, and after the switch, outputs the power transmission request signal again if a prescribed condition is satisfied.

15. A contactless power transmission method that performs power transmission from a power transmission device to a power receiving device through magnetic field coupling, The power receiving device outputs a power transmission request signal that requests power transmission, The power transmission device performs power transmission using the magnetic field coupling for the power receiving device for a predetermined power transmission period upon receiving the power transmission request signal, After the end of the power transmission period, the power transmission device switches to a power transmission state in which the amount of power transmission is less than the amount of power transmission during the power transmission period.

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