Contactless power supply system, contactless power transmission device, contactless power receiving device, and methods thereof.

Abstract

To enhance safety in contactless power supply. [Solution] The power receiving device 30 outputs a power transmission request signal, and the power transmission device 50, upon receiving this power transmission request signal, transmits power to the power receiving device using magnetic field coupling within a predetermined power transmission period. After the end of this power transmission period, the power transmission device switches to a power transmission state with a power transmission amount less than the power transmission amount during the power transmission period. This power transmission state may be a state in which power transmission is cut off, or a state in which power is transmitted with a reduced power transmission amount compared to the power transmission period.

Description

Technical Field

[0001] The present disclosure relates to wireless power transfer.

Background Art

[0002] In a wireless power transfer system, in order to simplify the system configuration, the power transmitting device and the power receiving device may adopt a configuration in which signals are exchanged through electromagnetic coupling for power transfer. For example, in Patent Document 1 below, when the power receiving device wants to stop the power supply operation of the power transmitting device, by controlling the impedance of the power receiving circuit of the power receiving device, the amount of current supplied from the DC power supply on the power transmitting device side is changed, and a power supply stop signal is demodulated from this change to stop the operation of the inverter of the power transmitting device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, such a 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 transmitting coil of the power transmitting device, the characteristics of capacitors, coils, and filter circuits that form a resonance circuit for power transfer, etc., so there may be cases where the power supply stop signal cannot be demodulated. If the power supply stop request from the power receiving device to the power transmitting device side cannot be normally transmitted, the power transmitting device continues the power supply operation. Therefore, when there is some abnormality in the power receiving device, the power supply from the power transmitting device may exacerbate the problem.

Means for Solving the Problems

[0005] The present disclosure can be realized in the following forms or application examples.

[0006] (1) A first embodiment of the present disclosure is a contactless power supply system (100) that supplies power from a power transmission device (50, 50B) to a power receiving device (30, 30A, 30B) by magnetic field coupling. In this contactless power supply system, a power transmission coil provided in the power transmission device and a power receiving coil provided in the power receiving device come into close proximity to form the magnetic field coupling, the power receiving device outputs a power transmission request signal to request power transmission, and when the power transmission device receives the power transmission request signal, it starts power transmission to the power receiving device using the magnetic field coupling, and after a predetermined power transmission period (Tt) has elapsed, even if it can be determined that the power transmission coil and the power receiving coil are magnetically coupled, it switches to a standby state in which the impedance of the circuit including the power transmission coil is greater than the impedance during the power transmission period. In this contactless power supply system, it is possible to avoid or suppress the continuation of unwanted power transmission.

[0007] (2) A second embodiment of the present disclosure is a power transmission device that transmits power to a power receiving device by magnetic field coupling. In this non-contact power transmission device, a power transmission coil provided in the power transmission device and a power receiving coil provided in the power receiving device are brought close together to form the magnetic field coupling, and when a power transmission request signal is received from the power receiving device, a first power transmission using the magnetic field coupling to the power receiving device is initiated, and after a predetermined power transmission period has elapsed, even if it can be determined that the power transmission coil and the power receiving coil are magnetically coupled, the device switches to a standby state in which the impedance of the circuit including the power transmission coil is greater than the impedance during the power transmission period. In this non-contact power transmission device, when a power transmission request signal is received, a first power transmission is performed for a predetermined period, and then the device switches to a standby state in which the amount of power transmitted is smaller than that of the first power transmission, so that unwanted power transmission does not continue.

[0008] (3) A third embodiment of the present disclosure is a contactless power receiving device that receives power transmitted from a power transmission device by magnetic field coupling. In this contactless power receiving device, a power transmission coil provided in the power transmission device and a power receiving coil provided in the contactless power receiving device are brought close together to form the magnetic field coupling, and the contactless power receiving device outputs a power transmission request signal to the power transmission device to request power transmission, and the contactless power receiving device is in a state where it can receive a first power transmission using the magnetic field coupling from the power transmission device that has received the power transmission request signal, and even if it can be determined that the power transmission coil and the power receiving coil are magnetically coupled after a predetermined power transmission period has elapsed, the contactless power receiving device outputs the power transmission request signal to the power transmission device again if predetermined conditions are met, after the power transmission device has switched the impedance of the circuit including the power transmission coil to a standby state that is greater than the impedance during the power transmission period.

[0009] (4) A fourth embodiment of the present disclosure is a contactless power supply method that supplies power from a power transmission device to a power receiving device by magnetic field coupling. In this contactless power supply method, a power transmission coil provided in the power transmission device and a power receiving coil provided in the power receiving device come into close proximity to form the magnetic field coupling, the power receiving device outputs a power transmission request signal requesting power transmission, and when the power transmission device receives the power transmission request signal, it starts power transmission to the power receiving device using the magnetic field coupling, and after a predetermined power transmission period has elapsed, even if it can be determined that the power transmission coil and the power receiving coil are magnetically coupled, it switches to a standby state in which the impedance of the circuit including the power transmission coil is greater than the impedance during the power transmission period. This contactless power supply method can avoid or suppress the continuation of unwanted power transmission. [Brief explanation of the drawing]

[0010] [Figure 1] A schematic diagram showing a contactless power supply system according to an embodiment. [Figure 2]A schematic diagram of the power transmission and receiving equipment that constitute a contactless power supply system. [Figure 3] An explanatory diagram showing an example of standby current and resonant current in the power transmission circuit of a power transmission device. [Figure 4] An explanatory diagram showing the positional relationship between the receiving coil and the transmitting coil, and the relationship between these and the current flowing through the transmitting coil. [Figure 5] A flowchart illustrating the overview of the processes at the power receiving and power transmitting sides. [Figure 6] An explanatory diagram showing an example configuration of a power transmission circuit in a power transmission device, including a switching section. [Figure 7] An explanatory diagram showing an example of the circuit configuration of a power receiving device. [Figure 8] A timing chart showing the operation of the power receiving device and the power transmitting device. [Figure 9] An explanatory diagram showing an example of the configuration of the power receiving device side in the second embodiment. [Figure 10] A flowchart showing an example of the processing on the power receiving device side in the second embodiment. [Figure 11] A flowchart showing an example of the processing on the power transmission device side in the second embodiment. [Figure 12] A schematic diagram of the power transmission device and power receiving device that constitute the contactless power supply system of the third embodiment. [Figure 13] A flowchart showing an example of a power transmission side processing routine as the first variation. [Figure 14] A flowchart showing an example of a transmission-side processing routine as a second variation. [Figure 15] A flowchart showing an example of a transmission-side processing routine as a third variation. [Modes for carrying out the invention]

[0011] A. First Embodiment: (A1) Overall configuration of the contactless power supply system: The schematic configuration of a non-contact power supply system 100 including a power transmission device 50 and a power reception device according to the first embodiment is shown in FIG. 1. As shown in the figure, this non-contact power supply system 100 is composed of a plurality of power transmission devices 50 buried in the ground under the road surface SF and a power reception device 30 mounted on a moving body 20 that moves on the road surface SF. The moving body 20 includes drive wheels 21 driven by a motor (not shown) included in the load device 45, driven wheels 22 that support the moving body 20 on the road surface SF together with the drive wheels 21, a power reception coil 31 disposed under the floor of the moving body 20, and the like. The power reception coil 31 is magnetically coupled with the power transmission coil 51 of the power transmission device 50 prepared on the road surface SF side to receive AC power supply and supplies power to the load device 45. Note that the power transmission device 50 and the non-contact power supply system 100 including the same are not limited to those that supply power to the power reception device 30 of the moving body 20. As long as they are devices that perform non-contact power transmission and power supply systems, the power reception device may be a device or system that performs power transmission or power supply to something other than a moving body, such as a portable terminal. The moving body 20 is not limited to those that travel on outdoor roads and includes transport vehicles used indoors such as factories and hospitals. The number of wheels of the moving body 20 may be any number, and it may move by a method other than wheels, such as magnetic levitation.

[0012] In addition to the configuration of being buried under the road surface SF, the power transmission device 50 can also be installed on the road surface or on a wall surface or ceiling. In such cases, the power reception device 30 may be arranged at a predetermined position within the moving body 20 corresponding to the installation location of the power transmission device 50. For example, if the power transmission device 50 is laid on a wall surface, the power reception device 30 may be arranged on the side surface of the moving body 20. Further, in accordance with the laying position of the power transmission device 50, the power reception device 30 may be moved inside the moving body 20, or a plurality of power reception devices 30 may be prepared in advance and switched for use.

[0013] In this embodiment, the multiple power transmission devices 50 that supply power to the power receiving device 30 of the mobile body 20 each have the same configuration and are arranged along the movement path of the mobile body 20. Of course, the power transmission devices 50 are not limited to the movement path of the mobile body 20, but may also be arranged two-dimensionally on the road surface SF. Each power transmission device 50 is connected to a common main power line RFP. The main power line RFP is supplied with AC power of high frequency f1 (e.g., 85 kHz) from the main power supply device 60. In this embodiment, each power transmission device 50 has the same configuration, but the configuration does not have to be the same as long as power transmission is possible, for example, by arranging power transmission coils 51 of different sizes alternately. Of course, there may be only one power transmission device 50.

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

[0015] The schematic configuration of the power transmission device 50 and the power reception device 30 is shown in FIG. 2. The figure shows a state in which one of the plurality of power transmission devices 50 is transmitting power to the power reception device 30 of the moving body 20. At this time, the power transmission coil 51 of the power transmission device 50 is magnetically coupled to the power reception coil 31 of the power reception device 30, and an induced current (alternating current) flows through the power reception coil 31. The power reception device 30 includes a power reception circuit 35 that performs power reception using the power reception coil 31, a load device 45 that operates using the received power, a power reception control unit 40 composed of a CPU and a memory, and a power transmission request output unit 70 that outputs a power transmission request in response to an instruction from the power reception control unit 40. In order for the power reception coil 31 to receive power from the power transmission coil 51 by magnetic coupling and apply a DC voltage to the load device 45, the power reception circuit 35 is provided with a power reception circuit and a rectifier circuit, but these circuit configurations will be described in detail later. The power reception circuit means a circuit connected to the power reception coil 31, but various circuit elements such as a current sensor may be connected to the power reception circuit, and the “power reception circuit” in a broad sense means a closed circuit through which a current for receiving power using the power reception coil 31 flows. The load device 45 includes, in this embodiment, those that use the main power used in the moving body, such as the moving motor of the moving body 20, and may also include a battery that temporarily stores power.

[0016] The power transmission device 50 that transmits power to this power reception device 30 includes, in addition to the power transmission coil 51, a power transmission control unit 80 that controls the power transmission current. The power transmission control unit 80 includes a CPU and a memory, executes a program necessary for the power transmission side processing, and controls the entire power transmission device 50 including detecting a power transmission request for requesting the start of power transmission. When the power transmission control unit 80 receives a power transmission request from the power reception device 30, it performs power transmission using magnetic coupling to the power reception device 30 for a predetermined power transmission period, and then switches to a standby state where the power transmission amount is less than the power transmission amount of this power transmission period.

[0017] Various methods can be employed for the output of a power transmission request from the power receiving device 30 and the detection of the power transmission request by the power transmission device 50. For example, it is easy to configure the power transmission request output unit 70 of the power receiving device 30 as a transmitter that performs short-range wireless communication such as Bluetooth®, and to give the power transmission control unit 80 the function of a receiver that detects wireless communication from the power transmission request output unit 70 to send and receive power transmission requests. Alternatively, short-range communication using RFID or other methods may be used, or wireless communication such as WiFi may be used. Communication may also be performed by optical communication or the like. Such communication is not limited to contactless methods, but may also be performed by wired communication in which a contactor on the power receiving device 30 side makes contact with a contact terminal provided on the power transmission device 50 side. Furthermore, the power transmission request may be transmitted using the magnetic field coupling between the power receiving coil 31 and the power transmitting coil 51. In this case, the strength of the magnetic field coupling may be changed using a coil other than the receiving coil 31, thereby changing the magnitude of the current flowing through the transmitting coil 51 and treating it as a power transmission request. Alternatively, an AC voltage with a frequency f2 different from the frequency f1 of the AC voltage used for power transmission may be applied to the receiving coil 31, and this frequency f2 may be modulated and treated as a power transmission request.

[0018] When the power transmission control unit 80 receives a power transmission request from the power receiving device 30, it transmits power to the power receiving device 30 using magnetic field coupling for a predetermined power transmission period, and then switches to a standby state where the amount of power transmitted is less than the amount of power transmitted during this period. The power transmission control unit 80 can have any circuit configuration as long as it can perform this operation. For example, a switching unit can be provided to switch the impedance of the closed circuit passing through the power transmission coil 51. When a power transmission request is received from the power receiving device 30, the impedance of the closed circuit can be reduced to transmit power, and after a predetermined power transmission period has elapsed, the impedance can be switched to a standby state where it is greater than the impedance during the power transmission period. The impedance can be switched using a resistor inserted in the closed circuit, or, considering that the current flowing through the closed circuit is alternating current, the capacitance of a capacitor inserted in the closed circuit can be switched. Of course, the inductance of the power transmission coil 51 can also be switched. These switching operations can be easily achieved by switching the connections of capacitors with different capacitances or by switching the connections to taps with different numbers of windings provided on the power transmission coil 51. Of course, components that can change capacitance or inductance, such as variable capacitance capacitors, may also be used.

[0019] In this embodiment, the power transmission coil 51 and the power transmission control unit 80 constitute a primary side resonant circuit. When transmitting power, the impedance of the closed circuit equipped with the power transmission coil 51 is switched to set the resonant frequency of the circuit to a resonant state that matches or is close to the frequency f1 of the main power line RFP. When power is not being transmitted, i.e., in the standby state, the resonant frequency of the circuit is deviated from frequency f1. As a result, the resonant current Ir flowing through the power transmission coil 51 in the resonant state is significantly greater than the standby current Is flowing through the power transmission coil 51 in the standby state. This is illustrated in Figure 3. In the figure, Ir is shown as the relationship between the frequency and the current flowing through the power transmission coil 51 when the impedance of the power transmission circuit is a value that sets the resonant frequency of the circuit to f1 (85 kHz in this case), and Is is shown as the relationship between the frequency and the current flowing through the power transmission coil 51 when the resonant frequency of the circuit is a value different from f1 (a frequency higher than f1 in this case). Since the 85kHz voltage of the main 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 less than the current Ir flowing through the power transmission coil 51 in the resonant state. Here, the power transmission circuit refers to a circuit consisting of the power transmission coil 51 and the power transmission control unit 80, but various circuit elements such as current sensors may be connected to the power transmission circuit, and in a broader sense, the "power transmission circuit" refers to a closed circuit through which the current transmitted using the power transmission coil 51 flows.

[0020] The principle of transmitting low standby current and high power during transmission using this impedance switching will be explained with reference to Figure 4. The figure illustrates how the current flowing through the transmitting coil 51 is transformed depending on the position of the receiving coil 31 relative to the transmitting coil 51. In this example, the transmission circuit is assumed to be an LC series resonant circuit. A parallel resonant circuit can also be used, in which case the characteristics will be the opposite of those shown. When using an LC series resonant circuit, whether the impedance of the transmission circuit is high and a standby current Is flows through the transmitting coil 51, or whether the impedance of the transmission circuit is low and a resonant current Ir larger than the standby current Is flows through the transmitting coil 51, the current value is largest when the center of the receiving coil 31 coincides with the center of the transmitting coil 51, and small when the receiving coil 31 is off-center from the center of the transmitting coil 51. This is shown in the upper part (A) of the figure.

[0021] Utilizing this characteristic, conventionally, the transmission circuit is initially in a standby state with high impedance. When the standby current Is flowing in the standby state exceeds a predetermined ON judgment threshold Th1, the impedance of the transmission circuit is lowered, putting the transmission circuit into a resonant state. In this state, a resonant current Ir flows between the two coils, enabling the transmission of large amounts of power. Furthermore, as the receiving coil 31 moves away from the center of the transmitting coil 51, the resonant current Ir is compared with a predetermined OFF judgment threshold Th2. When it falls below this threshold, the impedance of the transmission circuit is increased, switching to the standby state. This makes it possible to keep power consumption low in the standby state where the receiving coil 31 is absent. This is illustrated in the lower part (B) of Figure 4.

[0022] (A2) Contactless power supply processing: Assuming the impedance switching described above, the power transmission device 50 and the power receiving device 30 perform the power supply process shown in Figure 5. In Figure 5, corresponding to the configuration in Figure 2, the processing on the power transmission device 50 side is shown on the left and the processing on the power receiving device 30 side is shown on the right. The illustrated processing is repeatedly executed by the power transmission control unit 80 and the power receiving control unit 40 when the power transmission device 50 and the power receiving device 30 are started up.

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

[0024] The power receiving device 30 outputs an instruction to the power transmission device 50 for a power transmission request. When the power receiving device 30 starts up, the power receiving control unit 40 repeatedly executes the power receiving side processing shown in the figure. When the power receiving side processing starts, the power receiving control unit 40 first determines whether or not power needs to be received (step S210). Whether or not power needs to be received is determined according to whether or not there is a request from the load. If a battery is provided and power is supplied to the load device 45, such as a drive motor, from the battery, whether or not there is a request from the load can be determined by whether or not the battery's SOC is below a predetermined threshold. If it is below the threshold, it is determined that power needs to be received. Alternatively, the determination may be made regardless of whether or not there is a battery, by whether or not the load device 45 is requesting power. If power does not need to be received (step S210: "NO"), this process may be repeated, or the routine may be terminated and the process may be executed again from step S210 at a predetermined interval.

[0025] If it is determined that power needs to be received (step S210: "YES"), the next step is to output a power transmission request instruction (step S230). At this time, a process to detect the presence or absence of the power transmission device 50 in advance (step S220) may be performed, or the power transmission request may be output without detecting the presence or absence of the power transmission device 50. Detecting the power transmission device 50 means detecting whether the power transmission coil 51 of the power transmission device 50 is in the vicinity of the power receiving coil 31. As shown in Figure 4, when the power receiving coil 31 and the power transmission coil 51 are close together, the current increases even in the standby state. The presence of the power transmission device 50 may be detected from this increase in current, or the presence of the power transmission device 50 may be detected by short-range communication using Bluetooth® or RFID. Note that detection of the power transmission device 50 is not necessarily required. In response to a power transmission request from the power receiving device 30, if the power transmission device 50 is within range of the power receiving device 30, the power transmission device 50 will perform the process described below. If it is not nearby, there will simply be no response to the power transmission request. By detecting the presence of the power transmission device 50, the reliability of the operation of the contactless power supply system 100 can be verified by determining the operation of the power transmission device 50 in response to the power transmission request.

[0026] A power transmission request is output from the power receiving device 30, for example, by communication. At this time, if a power transmission device 50 is located near the power receiving device 30 that output the power transmission request, the power transmission device 50 determines that there is a power transmission request (step S130: "YES"). Specifically, it lowers the impedance of the power transmission circuit and performs the power transmission process (step S140). Subsequently, this power transmission process (step S140) is repeated until time Tt has elapsed (step S160). Once time Tt has elapsed, power transmission is terminated, the impedance of the power receiving circuit is increased, and the device switches to a standby state (step S170). Here, the elapsed time Tt can be easily detected using a real-time clock or the like. Alternatively, the total amount of power transmitted using the power transmission coil 51 may be counted, and power transmission may be terminated when time Tt has elapsed or when the total amount of power reaches a predetermined value, whichever comes first.

[0027] While the power transmission device 50 is performing this power transmission process, the power receiving device 30 performs the power receiving process (step S240). The power receiving process may be performed for a time Tt, matching the power receiving process time Tt in the power transmission device 50, or it may be performed until the received current falls below a predetermined value. Even if the power receiving coil 31 is facing the power transmission coil 51 during this time, the power transmission process on the power transmission device 50 will end once time Tt has elapsed, so the power receiving process will not continue indefinitely. Power transmission from the power transmission coil 51 to the power receiving coil 31 can be performed using the magnetic field coupling between the two coils, and may be performed simply by electromagnetic induction, or the resonant frequency of the power transmission circuit and power receiving circuit may be matched to the frequency of the power supplied to the main power line RFP, and power transmission utilizing resonance may be used.

[0028] On the power transmission device 50 side, after completing the power transmission process, a reliability check of the power transmission circuit (step S190) may be performed, but it is not required. Alternatively, the number of power transmissions and the cumulative power transmission time may be predetermined, and the reliability check may be triggered when these predetermined numbers of transmissions or cumulative transmission times are reached. Furthermore, it is also effective to trigger the reliability check when some phenomenon is detected by a sensor, such as when a temperature sensor installed in the power transmission circuit detects a temperature rise exceeding a predetermined temperature range. Alternatively, a combination of these triggers may be used to perform the reliability check. Similarly, on the power receiving device 30 side, a reliability check of the power receiving circuit may be performed after the completion of the power receiving process (step S240). The reliability check may or may not be performed, and if performed, the timing may be determined by one of the triggers, or a combination of several triggers, similar to the decision made on the power transmission device side described above.

[0029] A specific circuit configuration example of the power transmission device 50 and power receiving device 30 that perform such processing will be described. As already explained, the power transmission device 50 includes a power transmission coil 51 and a power transmission control unit 80, forming a primary side resonant circuit. As shown in Figure 6, the power transmission control unit 80 includes a switching unit 53 that switches impedances, a detection unit 55 that detects the magnitude of the current flowing through the power transmission coil 51, and a power transmission request detection unit 85 that detects power transmission requests. The switching unit 53 includes two capacitors Cs and Cr connected in series, and a switch SW connected in parallel to the capacitor Cs. The switch SW includes two switching elements SW1 and SW2 connected in series, and diodes D1 and D2 connected in parallel to each switching element SW1 and SW2. Signal lines from the power transmission request detection unit 85 are connected to the gates of the switching elements SW1 and SW2.

[0030] In the switching unit 53 having the above circuit configuration, if the start signal SS from the power transmission request detection unit 85 is off (non-active), the switch SW will be off (non-conductive), so the two capacitors Cs and Cr will be connected in series, and as the switching unit 53, Cts will be... Cts = 1 / (1 / Cs + 1 / Cr) This is the result. On the other hand, when the start signal SS from the power transmission request detection unit 85 turns on (active), the two switching elements SW1 and SW2 each become capable of conducting in one direction, and in cooperation with the diodes D1 and D2 connected in parallel, when an AC voltage is applied, they become capable of conducting, meaning that current can flow in both directions. Therefore, when the start signal SS is on, there is no effect from the capacitor Cs, and the total capacitance Ct of the switching unit 53 is, Ctr=Cr This means that the switching unit 53 functions as a switching unit that switches the impedance of the circuit through which current flows to the power transmission coil 51 in relation to the frequency of the AC voltage applied from the main power line RFP, by switching the capacitance of the resonant capacitor connected to the power transmission coil 51. Since the capacitor is connected in series by the switch SW, the relationship between the magnitudes of capacitances Ctr and Cts is, Ctr>Cts This is the result.

[0031] In this embodiment, when the start signal SS is ON, the capacitance Ctr, together with the reactance Lr of the transmission coil 51, is set so that the resonant frequency fr of the resonant circuit becomes 85 kHz, the frequency of the main power line RFP. On the other hand, when the start signal SS is OFF, the capacitance Cts causes the resonant frequency fr of the resonant circuit to deviate significantly from 85 kHz. In this case, resonance does not occur, but since the impedance of the circuit is not infinite, a constant AC current flows. This is the standby current Is. The current that occurs when the start signal SS is 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. In either case, the magnitude of the current is detected by the detection unit 55.

[0032] The function of the power transmission request detection unit 85 in the power transmission control unit 80 will be explained below along with the configuration of the power receiving device 30. An example of the configuration of the power receiving device 30 is shown in Figure 7. The power receiving device 30 includes the power receiving coil 31, power receiving circuit 35, power receiving control unit 40, load device 45, and power transmission request output unit 70, as described above. As shown in the figure, the power receiving coil 31 forms a series resonant circuit together with the capacitor CC1. 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, for example, the State of Charge (SOC) indicating the charge state, is monitored by the power receiving control unit 40.

[0033] The power transmission request output unit 70 of the power receiving device 30 includes a sub-coil 71 that forms a magnetic field coupling when the power transmission coil 51 is in close proximity, a resonant capacitor CC2, and a solid-state relay 74 operated by the power receiving control unit 40. In the figure, only the contacts of the solid-state relay 74 are shown. The contacts of the solid-state relay 74 are open by default, and in this state, no current flows through the circuit of the power transmission request output unit 70. When the power receiving control unit 40 detects the status of the load device 45 and determines that power should be received, it outputs a power transmission request signal RS to the power transmission request output unit 70, drives the solid-state relay 74 to close its contacts, and the circuit of the power transmission request output unit 70 becomes a closed circuit. The resonant frequency of the series resonant circuit formed by the sub-coil 71 and the resonant capacitor CC2 is set to 85 kHz. In this state, if the transmission coil 51 is in the vicinity of the sub-coil 71, the magnetic field coupling between the transmission coil 51 and the sub-coil 71 causes current to flow through the closed circuit of the power transmission request output unit 70, and as a result, the current flowing through the transmission coil 51 also increases. In the power transmission device 50, the magnitude of the current flowing through the transmission coil 51 is detected by the detection unit 55. The power transmission request detection unit 85 determines that the standby current Is has increased and outputs a start signal SS to the switching unit 53. This switches the impedance of the switching unit 53 to a lower value, causing a resonant current Ir to flow, and power transmission via the transmission coil 51 and the receiving coil 31 is performed for a predetermined time Tt, after which power transmission is terminated.

[0034] This is shown in Figure 8. As illustrated, when the power transmission coil 51 and the power receiving coil 31 are magnetically coupled, and the power receiving device 30 turns on the power transmission request signal RS, the current Is flowing through the power transmission coil 51 increases. The power transmission request detection unit 85 detects this, and as a result, the switching unit 53 switches from a high-impedance standby state to a low-impedance resonant state, and the current Ir flowing through the power transmission coil 51 increases rapidly. As a result, the power transmission device 50 enters a state for power transmission processing (Figure 5, step S140), and the power receiving device 30 enters a state for power reception processing (Figure 5, step S240).

[0035] The power transmission process on the power transmission device 50 ends after time Tt has elapsed, regardless of the magnitude of the current Ir. As a result, the switching unit 53 of the power transmission device 50 switches to high impedance, the power transmission circuit enters a standby state, and the current flowing through the power transmission coil 51 becomes the standby current Is. This state continues until a power transmission request signal is output from the power receiving device 30. During this time, the power receiving device 30 and the power transmission device 50 may perform reliability checks. After that, if the power receiving device 30 outputs a power transmission request in consideration of the status of the load device 45, etc., the above-described operations and power transmission / receiving processes are performed again.

[0036] In the power transmission device 50 and power receiving device 30 described above, the power transmission request signal RS is initially turned on and then turned off after a predetermined time. This is because the power receiving control unit 40 determines the pulse width of the power transmission request signal RS and turns the power transmission request signal RS on. Alternatively, the power receiving control unit 40 may be controlled to turn off the power transmission request signal RS after initially turning on the power transmission request signal RS, once the power receiving process has started and it has been confirmed that power transmission of a power level above a predetermined threshold has begun. This type of processing has the advantage that, if the control is performed in such a way that the power transmission request signal RS is output without detecting whether the mobile body 20 is moving and whether the power receiving coil 31 is close to the power transmission coil 51, it is not necessary to output the power transmission request signal RS multiple times to start power transmission.

[0037] In the first embodiment of the contactless power supply system 100 described above, the power transmission device 50 does not start power transmission by detecting the presence of the power receiving coil 31 from the magnitude of the current flowing through the power transmission coil 51, but rather starts power transmission in response to a power transmission request from the power receiving device 30, and moreover, stops power transmission after a predetermined time Tt has elapsed. For this reason, even if the current flowing through the power transmission coil 51 becomes larger than the design value due to variations in the power transmission circuit or power receiving circuit, and the power transmission device 50 is unable to detect that the power receiving coil 31 has released the magnetic field coupling with the power transmission coil 51, the power transmission device 50 will not send unnecessary current in an attempt to continue power transmission. Furthermore, power transmission will not continue even if some kind of malfunction occurs on the power receiving device 30 side and it is undesirable to continue receiving power. This is because the power transmission device 50 will stop power transmission after a predetermined time Tt has elapsed. For this reason, it is possible to avoid transmitting power that should not be transmitted without any communication with the power receiving device 30 other than the exchange of power transmission requests. As a result, it is possible to reduce power consumption and address malfunctions on the power receiving device 30 side. Various malfunctions on the power receiving device 30 side can be anticipated, such as the battery being overcharged if a battery is installed, or the temperature rising to a level exceeding the rated capacity of the power receiving device 30.

[0038] In this embodiment, if the power transmission device detection process in step S220 of the process shown in Figure 5 is performed, the power transmission request will not be unnecessarily output if the power receiving device 30 is not in close proximity to the power transmission device 50. Furthermore, if the reliability check process (step S290) is performed after the power receiving process (step S240) is completed, the reliability of the device can be confirmed during the period when power receiving is not being performed. This makes it easier to ensure the reliability of the equipment receiving power. Similarly, if the reliability check process (step S190) is performed after the power transmission process (step S170) is completed, the reliability of the device can be confirmed during the period when power transmission is not being performed, making it easier to ensure the reliability of the equipment transmitting power.

[0039] In the above embodiment, since the power transmission request is output using magnetic field coupling with the power transmission coil 51, there is no need for equipment such as communication devices, and the configuration of the power transmission device 50 and the power receiving device 30 can be simplified. Furthermore, there is no need to prepare a separate power supply for the power transmission request output unit 70, which can further simplify the configuration.

[0040] B. Second Embodiment: Next, the contactless power supply system 100 of the second embodiment will be described. The overall configuration of the contactless power supply system 100 of the second embodiment is the same as that of the first embodiment shown in Figure 1. In the contactless power supply system 100 of the second embodiment, the power transmission device 50 has the same configuration as that of the first embodiment. The configuration of the power receiving device 30A of the second embodiment is shown in Figure 9. As shown in the figure, this power receiving device 30A differs in three points: the power receiving circuit is the same as that of the first embodiment, it is equipped with a current sensor 37 that detects the current value Ii flowing through the power receiving circuit, it is equipped with a power transmission coil detection unit 90, and the configuration of the power transmission request output unit 70A is different. In this embodiment as well, the power receiving control unit 40A reads the state of the load device 45 and outputs a power transmission request signal RS.

[0041] The power transmission coil detection unit 90 provided in the power receiving device 30A is provided to detect the presence of the power transmission coil 51. The power transmission coil detection unit 90 comprises 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. The determination circuit 93 determines the presence of a power transmission coil 51 adjacent to the detection coil 91 based on the magnitude of the current detected by the detection circuit 92. When the determination circuit 93 has determined that a power transmission coil 51 is nearby, and the drive circuit 95 receives a power transmission request signal RS from the power receiving control unit 40A, it outputs a drive signal to the inverter 75 for a predetermined period of time.

[0042] The power transmission request output unit 70A in the power receiving device 30A includes a resonant circuit consisting of a sub-coil 71 and a resonant capacitor CC2, and an inverter 75 is provided between this resonant circuit and the DC power supply 77. The four switching transistors Tr1-Tr4 that make up the inverter 75 form a bridge, and the output signal from the drive circuit 95 of the power transmission coil detection unit 90, which will be described later, is connected to its gate terminal. The four switching transistors Tr1-Tr4, with two switching transistors Tr1 and TR4 and Tr2 and Tr3 arranged diagonally opposite each other, are switched on and off exclusively, applying an 85kHz AC voltage to the resonant circuit. At this time, if the power transmission coil 51 of the power transmission device 50 is in close proximity, the sub-coil 71 magnetically couples with it, increasing the current flowing through the power transmission coil 51. This functions as a power transmission request to the power transmission device 50.

[0043] The power receiving side processing performed by the power receiving control unit 40A of the power receiving device 30 in the second embodiment will be explained using Figure 10, and the power transmitting side processing performed by the power transmitting control unit 80 of the power transmitting device 50 will be explained using Figure 11. When the power receiving device 30 is started up, the power receiving control unit 40A repeatedly executes the processing routine shown in Figure 10 at predetermined intervals. First, the power receiving control unit 40A obtains a load request from the load device 45 (step S310) and determines whether or not to receive power from the power transmitting device 50 based on the load conditions (step S315). If it is determined that power needs to be received (step S315: "YES"), the power receiving control unit 40A then obtains the current value Ii flowing through the power receiving circuit from the current sensor 37 (step S320), and determines whether or not power has already been received from the power transmitting device 50 based on this current value Ii (step S325). If the current value Ii is small and it cannot be determined that power is being received, the power receiving control unit 40A turns on the power transmission request signal RS (step S340). Then, it reads the output of the current sensor 37 to obtain the current value Ii flowing through the power receiving circuit (step S350), and determines whether this current value Ii is greater than or equal to a preset determination threshold Thr (step S355). These processes (steps S350, S355) are repeated until Ii > Thr.

[0044] In response to the above operation of the power receiving device 30, the power transmitting device 50 performs the following processing and makes the following decisions. After startup, as shown in Figure 11, the power transmitting device 50 switches the switching unit 53 to a standby state in which the impedance of the power transmission circuit is high (step S410), and obtains the current value It flowing through the power transmission coil 51 from the detection unit 55 (step S420). Then, it determines whether this current value It is greater than a predetermined judgment threshold Ths (step S430), and if it is not greater than the judgment threshold Ths, it returns to step S410 and repeats the above processing. During this time, the power receiving control unit 40A of the power receiving device 30A turns on the power transmission request signal RS, and the standby current flowing through the power transmission coil 51 increases due to the power transmission request output unit 70A, at which point the current value It exceeds the judgment threshold Ths (step S430: "YES").

[0045] Based on this determination, the power transmission control unit 80 reduces the impedance of the switching unit 53 and switches to a power transmission state in which a resonant current Ir can flow (step S440). As a result, power transmission by resonance begins using the magnetic field coupling between the power transmission coil 51 and the power receiving coil 31, and the currents flowing through both the power transmission coil 51 and the power receiving coil 31 increase. The power transmission control unit 80 of the power transmission device 50 repeats this state until time Tt has elapsed (step S450). Once time Tt has elapsed, the power transmission control unit 80 returns to step S410, increases the impedance of the switching unit 53, and switches to the standby state.

[0046] When the power transmission request signal RS is output, if the power transmission coil 51 of the power transmission device 50 is close to the power receiving coil 31, as described above, the drive circuit 95 of the power transmission coil detection unit 90 drives the inverter 75 of the power transmission request output unit 70A. As a result, the power transmission control unit 80 of the power transmission device 50 detects a power transmission request when the current value It flowing through the power transmission coil 51 exceeds the judgment threshold Ths, and reduces the impedance of the switching unit 53 to switch the resonant frequency to 85kHz. Consequently, the impedance of the power transmission circuit decreases, a resonant current Ir flows, and consequently, the current value Ii detected by the current sensor 37 again also increases.

[0047] Therefore, if the power receiving control unit 40A of the power receiving device 30A repeats steps S350 and S355, eventually the current value Ii will become greater than the judgment threshold Thr (step S355: "YES"), and the power receiving control unit 40A will turn off the power transmission request signal RS (step S360). However, there may be cases where, for some reason, even if the mobile body 20 moves, it cannot get close to the power transmission device 50, and the situation where the current value Ii cannot exceed the judgment threshold Thr continues. In such cases, the time spent in the loop of steps S350-S355 can be measured, and the power transmission request signal RS can be turned off due to a timeout, thereby terminating this processing routine.

[0048] After turning off the power transmission request signal RS, the power receiving process (step S370) is performed, and the main processing routine is terminated. This processing routine is executed repeatedly at predetermined intervals, so if power receiving is necessary from the perspective of the load request, the process and decision are performed in the order of steps S310, S315, S320, S325, and S370, and the power receiving process continues. On the other hand, if power receiving is no longer necessary from the perspective of the load request (step S315: "NO"), nothing is done, and the process routine is terminated by exiting to "NEXT". In this embodiment, if the power receiving request is terminated in the middle of the power receiving process, nothing is done in particular, but even in that case, if a predetermined time Tt has elapsed since the power transmission device 50 that received the power transmission request started transmitting power, the power transmission by the power transmission device 50 will stop. Alternatively, one of the diodes constituting one arm of the power receiving circuit 35, for example diodes RD1 and RD3, may be replaced with switching elements, and when there is no longer a need for power receiving in light of the load requirements, the switching elements may be turned off to terminate the power receiving process.

[0049] In the second embodiment of the non-contact power supply system 100 described above, the same effects and advantages as in the first embodiment are achieved, and furthermore, since the power receiving device 30 is provided with a power transmission coil detection unit 90, it is possible to request power transmission from the power transmission device 50 after confirming that the power transmission device 50 is nearby. In addition, after the power receiving control unit 40 turns on the power transmission request signal RS, it detects from the power receiving coil 31 that power transmission from the power transmission device 50 to the power receiving device 30A has started. The power transmission request signal RS is turned off after confirmation based on the current value Ii, ensuring that the power transmission request is reliably communicated to the power transmission device 50.

[0050] C. Third Embodiment: Next, a contactless power supply system 100 of the third embodiment will be described. As shown in Figure 12, the contactless power supply system 100 of the third embodiment comprises a power transmission device 50B and a power receiving device 30B. The power transmission device 50B and the power receiving device 30B have the same configuration as in the first embodiment, but instead of using magnetic field coupling between the power transmission coil 51 and the power receiving coil 31 to notify the power transmission device 50B of a power transmission request from the power receiving device 30B, notification by communication is used. For this communication, the power receiving device 30B comprises a power transmission request transmission unit 79, and the power transmission device 50B comprises a receiving unit 89. The power transmission request transmission unit 79 and the receiving unit 89 communicate using Bluetooth®. The communication method is not limited to this, and other methods such as optical communication or WiFi may also be used.

[0051] When the power transmission request transmission unit 79 receives the power transmission request signal RS output by the power receiving control unit 40, it outputs a signal requesting power transmission. If the power transmission device 50B is within the output range of this signal, the receiving unit 89 of the power transmission device 50B receives this power transmission request signal and transmits it to the power transmission control unit 80. For a predetermined time Tt, the power transmission control unit 80 lowers the impedance of the power transmission circuit and performs power transmission using resonance between the power transmission coil 51 and the power receiving coil 31. After the predetermined time Tt has elapsed, regardless of whether there is a resonant current, the power transmission control unit 80 increases the impedance of the power transmission circuit and terminates power transmission using resonance. If the power receiving device 30B requests power transmission, it again transmits a signal requesting power transmission to the power transmission device 50B via the power transmission request transmission unit 79, and if the receiving unit 89 receives this signal, power transmission is performed in the same manner.

[0052] The third embodiment of the contactless power supply system 100, which has the above configuration, also provides similar effects and advantages as the first and second embodiments, such as being able to perform contactless power transmission. Moreover, in the third embodiment, since the transmitting coil 51 and receiving coil 31 are not used for sending and receiving power transmission requests, there is no need to consider the timing of sending and receiving power transmission request signals using resonance, and the design freedom of both coils 51 and 31 can be increased. In addition, the possibility of misinterpreting noise between the two coils as a power transmission request can be eliminated.

[0053] In each of the embodiments described above, if there is a situation that requires power transmission to the power receiving device 30, such as a decrease in the battery's SOC, the power transmission request will be repeatedly output. However, there may be a limit on the interval at which a power transmission request can be output. For example, the interval at which a power transmission request can be output may be made longer than the predetermined time Tt during which the power transmission device 50 continues to transmit power, thereby ensuring a certain period of time during which power transmission using resonance does not occur. This will mitigate the temperature rise associated with power transmission in both coils 51 and the power receiving coil 31. It will also be easier to secure the time necessary for reliability checks and other processes in each device. Furthermore, from the viewpoint of temperature rise, conditions may be set on the number of times a power transmission request is repeated. For example, if the power receiving device 30 outputs 10 power transmission requests within a predetermined interval or less, it may not allow the output of the next power transmission request for a period longer than this interval, or even if a power transmission request is output from the power receiving device 30, the power transmission device 50 may not accept it for a certain period of time.

[0054] D. Variations: In some of the embodiments described above, the time Tt from the power receiving device 30 to the power transmission device 50 terminating power transmission was set to a predetermined time, but this time Tt may be variable depending on the power transmission conditions. Modifications 1 to 3 of these modifications are described below. In each modification, the time Tt is set as follows in the processing routine of the power transmission device 50 in the second embodiment (Figure 11).

[0055] In Modification 1, as shown in Figure 13, the process of setting the time Tt until power transmission is terminated based on the current value It flowing through the power transmission coil 51 is performed between steps S430 and S440. Specifically, if the judgment in step S430 is "YES", first the impedance of the switching unit 53 is reduced to put the system into a power transmission state (step S510), and then the current value It flowing through the power transmission coil 51 in the power transmission state is obtained (step S511). Then, based on this current value It, a predetermined time Tt until the power transmission state is terminated is set (step S512). By performing this process, the predetermined time Tt is determined according to the current value It when the system was put into a power transmission state. Here, the larger the current value It that flowed through the power transmission coil 51 when the system was put into a power transmission state, the larger the time Tt is set. However, the predetermined time Tt is always set to a finite value. The relationship between the current value It and the predetermined time Tt may be determined by a mathematical formula, or it may be determined by looking up the relationship in a table that has been prepared in advance.

[0056] According to this modified example 1, when the current value It flowing through the transmitting coil 51 is large when the power transmission state is activated, the time Tt until power transmission ends is set to be long, and when it is small, it is set to be short, so that the predetermined time Tt can be set to an appropriate length. In other words, when power transmission is started with the transmitting coil 51 and the receiving coil 31 facing each other, the time Tt during which power transmission continues is extended, and the decrease in average power supply can be suppressed. On the other hand, when power transmission is started with the transmitting coil 51 and the receiving coil 31 in a state where power can be supplied but they are relatively far apart, the time Tt during which power transmission continues is shortened, so that the time during which magnetic flux continues to be emitted from the transmitting coil 51 while the receiving coil 31 is far away can be shortened.

[0057] In the modified example 2, as shown in Figure 14, the process of setting the time Tt until power transmission is terminated based on the output current value Im supplied from the main power supply unit 60 to the power transmission unit 50 is performed between steps S430 and S440. Specifically, if the determination in step S430 is "YES", first the impedance of the switching unit 53 is reduced to put it into a power transmission state (step S510), and then the output current value Im output from the main power supply unit 60 to the power transmission unit 50 in the power transmission state is obtained (step S515). The output current value Im can be the detected value of the overcurrent detection current sensor provided in the inverter of the main power supply unit 60. Based on this output current value Im, a predetermined time Tt until the power transmission state is terminated is set (step S516). By performing this process, the predetermined time Tt is determined according to the output current value Im when the power transmission state is put into place. Here, the larger the output current value Im output to the power transmission device 50 when it is set to power transmission, the larger the time Tt is set. The same aspects as in Modification 1 include setting the time Tt to a finite value and determining the relationship between the output current value Im and the predetermined time Tt using a formula or table.

[0058] According to this modified version 2, when the power transmission state is activated, if the output current value Im output to the power transmission device 50 is large, the time Tt until power transmission is completed is set to be long, and if it is small, it is set to be short, so that the predetermined time Tt can be set 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, this modified version 2 also produces the same effects as modified version 1, such as suppressing the decrease in average power supply and suppressing the unnecessary radiation of magnetic flux from the power transmission coil 51 when the receiving coil 31 is far away.

[0059] In Modification 3, as shown in Figure 15, the process of setting the time Tt until power transmission is terminated based on the moving speed v of the mobile body 20 is performed between steps S430 and S440. Specifically, if the judgment in step S430 is "YES", the moving speed v of the mobile body 20 is first detected (step S520), and then a predetermined time Tt until the power transmission state is terminated is set based on the moving speed v of the mobile body 20 (step S521). By performing this process, the predetermined time Tt is determined according to the time for which the receiving coil 31 of the mobile body 20 is assumed to be facing the transmitting coil 51. Here, the smaller the moving speed v of the mobile body 20 and the longer the time for which both coils are considered to be magnetically coupled, the larger the time Tt is made. The fact that the time Tt is a finite value and that the relationship between the moving speed v and the predetermined time Tt is determined by a formula or table is the same as in Modifications 1 and 2.

[0060] According to this modified version 3, the time Tt until power transmission is completed is set to be longer when the moving speed is small, and shorter when the moving speed is large, so that the predetermined time Ti can be set to an appropriate length. In this modified version 3, when the moving speed v is small, it is assumed that the time spent with the transmitting coil 51 and the receiving coil 31 facing each other or in a position where power can be supplied is often long, so the decrease in average power supply can be suppressed. On the other hand, when the moving speed v is large, it is assumed that the transmitting device 50 and the receiving coil 31 separate in a short time, so the wasted radiation of magnetic flux from the transmitting coil 51 when the receiving coil 31 is separated can be suppressed.

[0061] E. Other embodiments: (1) The disclosure can also be implemented in the following embodiments. The first embodiment is a contactless power supply system configured to supply power from a power transmission device to a power receiving device by magnetic field coupling. In this contactless power supply system, the power receiving device outputs a power transmission request signal to request power transmission, and when the power transmission device receives the power transmission request signal, it transmits power to the power receiving device using the magnetic field coupling for a predetermined power transmission period, and then switches to a standby state in which the amount of power transmitted is less than the amount of power transmitted during the power transmission period. In this way, power transmission from the power transmission device is performed in response to a power transmission request signal from the power receiving device, and after the predetermined power transmission period has elapsed, it switches to a standby state in which the amount of power transmitted is less than the amount of power transmitted during the power transmission period. Therefore, power transmission from the power transmission device to the power receiving device using magnetic field coupling is not performed beyond the power transmission period, and a situation in which power transmission continues at a large amount even though it is undesirable for the power transmission to continue for some reason can be avoided or suppressed.

[0062] Here, the power transmission from the power transmission device to the power receiving device can be any method that uses magnetic field coupling, and may or may not use resonance. Furthermore, the amount of power transmitted in the standby state should be less than the amount of power transmitted during the power transmission period, and power may not be transmitted at all in the standby state. Situations in which it is undesirable for power transmission to continue include situations where the magnetic field coupling is insufficient, or situations in which it is undesirable for the power receiving device to continue receiving power. The latter may include cases where the power receiving device is equipped with energy storage devices such as secondary batteries or capacitors that are charged with the received power, and the energy storage devices are in a state where they can no longer store any more power, or where there is some kind of abnormality in the power receiving circuit. Such abnormalities include detection of overheating above a predetermined temperature, detection of overcurrents exceeding a predetermined value, and a power reception stop instruction issued from the power receiving device's diagnostic system.

[0063] (2) In the configuration of (1) above, the power transmission device may not perform power transmission using the magnetic field coupling in the standby state. This will stop power transmission, and the occurrence of problems associated with power transmission can be further suppressed. Problems associated with power transmission include unwanted temperature rise on the power receiving device side, unwanted overcharging, and wasted power consumption on the power transmission device side.

[0064] (3) In the configuration of (1) or (2) above, the power receiving device may output the power transmission request signal to the power transmission device using the magnetic field coupling. This allows the power transmission request signal to be output using magnetic field coupling, thus simplifying at least a part of the configuration for outputting the power transmission request signal. The power transmission request signal using magnetic field coupling can be output by changing the magnitude of the current flowing due to the magnetic field coupling. The change in the magnitude of the current can be determined by detecting the current value, but it is not limited to the current value; it may also be determined by detecting changes in the part through which the current flows, such as the voltage generated in the power transmission coil, the voltage across the capacitor forming the resonant circuit if a resonant circuit is formed, or the current flowing through the capacitor constituting the resonant circuit. Alternatively, it may be determined by detecting changes in the magnetic flux generated by the flowing current.

[0065] (4) In the configurations of (1) to (3) above, the power transmission device comprises a primary resonant circuit composed of a power transmission coil and a first capacitor, and an AC power supply device that supplies power by applying an AC voltage of a predetermined frequency to the primary resonant circuit, and the power receiving device comprises a secondary resonant circuit composed of a power receiving coil and a second capacitor, and a rectifier circuit that rectifies the AC induced in the secondary resonant circuit into DC, and the power transmission coil and the power receiving coil may form the magnetic field coupling. In this way, efficient wireless power transmission can be realized with a simple configuration. The primary resonant circuit and the secondary resonant circuit may be any one of the various configurations known as series resonant circuits consisting of a coil and a capacitor, or any one of the various configurations known as parallel resonant circuits.

[0066] (5) In the configuration of (4) above, the power receiving device may be provided with a signal output unit that outputs the power transmission request signal via the magnetically coupled power receiving coil and power transmission coil, and the power transmission device may be provided with a power transmission request detection unit that detects the power transmission request signal by a change in the amount of electricity in the power transmission coil. In this way, the power transmission request signal can be output from the power receiving device to the power transmission device with a simple configuration. Changes 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, etc.

[0067] (6) In the configuration of (4) or (5) above, the power transmission device may be provided with a switching unit between the power transmission coil and the AC power supply device for switching the amount of power transmitted. This makes it easy to switch between the amount of power that can be transmitted during the power transmission period and the amount of power that can be transmitted in the standby state. Switching the amount of power transmitted can be achieved by switching contacts that turn the power transmission circuit on and off, switching the magnitude of the circuit impedance, etc. The switching may be achieved by fixing the state as a switch from on to off, off to on, or by changing the ratio of on time to off time, that is, the on / off duty cycle.

[0068] (7) In the configurations of (4) to (6) above, the switching unit includes a switching circuit that switches the capacitance of the first capacitor from a first value to a second value, and the resonant frequency of the primary side resonant circuit when the capacitance of the first capacitor is the second value may be further from the predetermined frequency of the AC voltage than when the capacitance of the first capacitor is the first value. In this way, it is possible to easily switch the resonant frequency of the primary side resonant circuit closer to or further away from the frequency of the AC voltage, and the degree of power transmission using resonance can be changed. Changing the capacitance of the capacitor can be easily achieved by switching multiple capacitors, switching parallel or series connections, etc. Matching the resonant frequency of the primary side resonant circuit to the frequency of the AC voltage during the power transmission period is advantageous for increasing power transmission efficiency, but it does not have to match perfectly, and it is sufficient if it is closer to the frequency of the AC voltage than in the standby state. Note that the resonant frequency of the primary side resonant circuit may be switched by changing the inductance of the power transmission coil instead of changing the capacitance of the capacitor. This inductance switching can be easily achieved by adding a tap in the transmission coil and changing the number of windings by switching the tap. Alternatively, it can be achieved by using a transmission coil with a core and changing the overlap between the core and the windings to change the permeability of the transmission coil.

[0069] (8) In the configurations of (1) to (7) above, the power transmission device may include a parameter detection unit that detects parameters reflecting the amount of power transmitted during the power transmission period, and set the power transmission period according to the parameters. In this way, the power transmission period can be set by parameters that reflect the amount of power transmitted, thereby suppressing a decrease in average power supply and suppressing the wasteful radiation of magnetic flux. The parameters include the amount of power transmitted at the start of the power transmission period, for example, the current value flowing through the power transmission coil, and the amount of power in the power supply circuit that supplies power to the power transmission device.

[0070] (9) In the configurations of (1) to (8) above, the power receiving device may repeatedly output the power transmission request signal at predetermined intervals when predetermined conditions are met. In this way, contactless power supply can be continued even if there is an interruption period, as long as power supply is possible. It can be continued with interruptions. The predetermined conditions are that the receiving party is requesting power transmission and that there are no obstacles to receiving power.

[0071] (10) In the configuration of (9) above, the power receiving device may determine that the predetermined conditions are not met if there is an abnormality in the power receiving device. This reduces the possibility that power transmission will be carried out even if there is an abnormality in the power receiving device.

[0072] (11) In the configurations of (1) to (10) above, at least one of the power receiving device and the power transmitting device may perform safety checks of the device after the end of the power transmission period and before the next power transmission request signal is output from the power receiving device. This will satisfy the requirements of device safety and continuity of power supply.

[0073] (12) In the configurations of (1) to (11) above, the power receiving device is mounted on a mobile body that moves relative to the power transmitting device, and the length of the power transmission period may be predetermined according to the average time that the mobile body receives power from the power transmitting device while moving. In this way, the amount of power that can be transmitted can be determined from the average time required for the mobile body to pass the power transmitting device and power transmission can be carried out, thereby suppressing a decrease in average power supply and suppressing the wasteful radiation of magnetic flux.

[0074] (13) Another aspect of the present disclosure is a contactless power transmission device that transmits power to a power receiving device by magnetic field coupling. When this contactless power transmission device receives a power transmission request signal from the power receiving device, it performs a first power transmission to the power receiving device using the magnetic field coupling for a predetermined power transmission period, and after the power transmission period, it switches to a power transmission state with a lower power transmission amount than the first power transmission. In this way, the contactless power transmission device enters a power transmission state with a lower power transmission amount than the first power transmission after the power transmission period has elapsed, and does not continue to transmit unwanted power with a high power transmission amount indiscriminately.

[0075] (14) Another aspect of the present disclosure is a contactless power receiving device that receives power transmitted from a power transmission device by magnetic field coupling. This contactless power receiving device outputs a power transmission request signal to the power transmission device requesting power transmission, and the power transmission device, upon receiving the power transmission request signal, performs a first power transmission to the power receiving device using the magnetic field coupling for a predetermined power transmission period, and after the power transmission period, switches to a power transmission state with a power transmission amount less than the first power transmission, and if predetermined conditions are met, outputs the power transmission request signal again. In this way, unless the contactless power receiving device outputs a power transmission request signal, the power transmission period ends after a predetermined period, so that the contactless power receiving device does not continue receiving power indiscriminately, and if it is necessary to receive power, it can continue receiving power even if there is an interruption period.

[0076] (15) Another aspect of the present disclosure is a contactless power supply method in which power is supplied from a power transmission device to a power receiving device by magnetic field coupling. In this contactless power supply method, when the power receiving device outputs a power transmission request signal requesting power transmission, and the power transmission device receives the power transmission request signal, it transmits power to the power receiving device using the magnetic field coupling for a predetermined power transmission period, and after the end of the power transmission period, the power transmission device switches to a power transmission state with a power transmission amount less than the power transmission amount during the power transmission period. In this way, power transmission from the power transmission device is performed in response to a power transmission request signal from the power receiving device, and after the predetermined power transmission period has elapsed, it switches to a standby state with a power transmission amount less than the power transmission amount during the power transmission period. Accordingly, power transmission from the power transmission device to the power receiving device using magnetic field coupling is not performed beyond the power transmission period, and a situation in which power transmission continues at a large amount even when it is undesirable for power transmission to continue for some reason can be avoided or suppressed.

[0077] (16) In each of the above embodiments, some of the configurations implemented by hardware may be replaced with software. At least some of the configurations implemented by software can also be implemented by discrete circuit configurations. Furthermore, if some or all of the functions of this disclosure are implemented by software, the software (computer program) may be provided in the form of being stored on a computer-readable recording medium. "Computer-readable recording medium" is not limited to portable recording media such as flexible disks and CD-ROMs, but also includes various internal storage devices in a computer such as RAM and ROM, and external storage devices fixed to a computer such as hard disks. In other words, "computer-readable recording medium" has a broad meaning that includes any recording medium on which data packets can be fixed rather than temporary.

[0078] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features in the embodiments corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of Symbols]

[0079] 20...Moving body, 21...Drive wheel, 22...Driven wheel, 30...Power receiving device, 30A...Power receiving device, 30B...Power receiving device, 31...Power receiving coil, 35...Power receiving circuit, 37...Current sensor, 40...Power receiving control unit, 40A...Power receiving control unit, 45...Load device, 50...Power transmitting device, 50B...Power transmitting device, 51...Power transmitting coil, 53...Switching unit, 55...Detection unit, 60...Main power supply unit, 65...Main power supply, 70 ...Power transmission request output unit, 70A...Power transmission request output unit, 71...Sub-coil, 74...Solid state relay, 75...Inverter, 77...DC power supply, 79...Power transmission request transmission unit, 80...Power transmission control unit, 85...Power transmission request detection unit, 89...Receiver, 90...Power transmission coil detection unit, 91...Detection coil, 92...Detection circuit, 93...Determination circuit, 95...Drive circuit, 100...Contactless power supply system

Claims

1. A contactless power supply system (100) that supplies power from a power transmission device (50, 50B) to a power receiving device (30, 30A, 30B) by magnetic field coupling, The power transmission coil provided in the power transmission device and the power receiving coil provided in the power receiving device come into close proximity to form the magnetic field coupling. The power receiving device outputs a power transmission request signal to request power transmission, When the power transmission device receives the power transmission request signal, it starts transmitting power to the power receiving device using the magnetic field coupling, and after a predetermined power transmission period (Tt) has elapsed, even if it can be determined that the power transmission coil and the power receiving coil are magnetically coupled, it switches to a standby state in which the impedance of the circuit including the power transmission coil is greater than the impedance during the power transmission period. Contactless power supply system.

2. The contactless power supply system according to claim 1, wherein the power transmission device does not perform power transmission using the magnetic field coupling in the standby state.

3. The contactless power supply system according to claim 1, wherein the power receiving device outputs the power transmission request signal to the power transmission device using the magnetic field coupling.

4. The aforementioned power transmission device is A primary resonant circuit consisting of a power transmission coil (51) and a first capacitor (Cs, Cr), An AC power supply device (60) that supplies power by applying an AC voltage of a predetermined frequency to the primary side resonant circuit, Equipped with, The power receiving device is A secondary resonant circuit consisting of a power receiving coil (31) and a second capacitor (CC1), A rectifier circuit (35) that rectifies the alternating current induced in the secondary resonant circuit into direct current, Equipped with, The transmitting coil and the receiving coil form the magnetic field coupling. The contactless power supply system according to claim 1.

5. The power receiving device includes a signal output unit (70) that outputs the power transmission request signal via the magnetically coupled power receiving coil and power transmission coil, The power transmission device includes a power transmission request detection unit (85) that detects the power transmission request signal based on a change in the amount of electricity in the power transmission coil. The contactless power supply system according to claim 4.

6. The contactless power supply device according to claim 4, wherein the power transmission device includes a switching unit (80) for switching the amount of power transmitted between the power transmission coil and the AC power supply device.

7. The non-contact power supply system according to claim 6, wherein the switching unit includes a switching circuit (53) that switches the capacitance of the first capacitor from a first value to a second value, and the resonant frequency of the primary side resonant circuit when the capacitance of the first capacitor is the second value is farther from the predetermined frequency of the AC voltage than when the capacitance of the first capacitor is the first value.

8. The aforementioned power transmission device is The system includes a parameter detection unit (55) that detects parameters that reflect the amount of power transmitted during the power transmission period, The power transmission period is set according to the aforementioned parameters. A contactless power supply system according to claim 1, comprising:

9. The contactless power supply system according to claim 1, wherein the power receiving device repeatedly outputs the power transmission request signal at predetermined intervals when predetermined conditions are met.

10. The contactless power supply system according to claim 9, wherein the power receiving device determines that the predetermined conditions are not met if there is an abnormality in the power receiving device.

11. The contactless power supply system according to claim 1, wherein at least one of the power receiving device and the power transmitting device performs safety checks of the device after the end of the power transmission period and before the power receiving device outputs the next power transmission request signal.

12. The power receiving device is mounted on a mobile body (20) that moves relative to the power transmitting device. The contactless power supply system according to claim 1, wherein the length of the power transmission period is predetermined according to the average time that the mobile body receives power from the power transmission device while moving.

13. A non-contact power transmission device that transmits power to a power receiving device by magnetic field coupling, The power transmission coil provided in the power transmission device and the power receiving coil provided in the power receiving device come into close proximity to form the magnetic field coupling. When a power transmission request signal is received from the power receiving device, the first power transmission using the magnetic field coupling to the power receiving device is initiated. Even if it can be determined that the transmitting coil and the receiving coil are magnetically coupled after a predetermined power transmission period has elapsed, the circuit including the transmitting coil is switched to a standby state where the impedance is greater than the impedance during the power transmission period. Non-contact power transmission device.

14. A non-contact power receiving device that receives power transmitted from a power transmission device by magnetic field coupling, The power transmission coil provided in the power transmission device and the power receiving coil provided in the non-contact power receiving device come into close proximity to form the magnetic field coupling. The power transmission device is given a power transmission request signal to request power transmission, The power transmission device that received the power transmission request signal is put into a state where it can receive the first power transmission using the magnetic field coupling. Even if it can be determined that the transmitting coil and the receiving coil are magnetically coupled after a predetermined power transmission period has elapsed, the power transmission device will switch the impedance of the circuit including the transmitting coil to a standby state where the impedance is greater than the impedance during the power transmission period, and if predetermined conditions are met, it will again output the power transmission request signal to the power transmission device. Non-contact power receiving device.

15. A contactless power supply method that supplies power from a power transmission device to a power receiving device by magnetic field coupling, The power transmission coil provided in the power transmission device and the power receiving coil provided in the power receiving device come into close proximity to form the magnetic field coupling. The power receiving device outputs a power transmission request signal requesting power transmission, When the power transmission device receives the power transmission request signal, it starts transmitting power to the power receiving device using the magnetic field coupling, and after a predetermined power transmission period has elapsed, even if it can be determined that the power transmission coil and the power receiving coil are magnetically coupled, it switches to a standby state in which the impedance of the circuit including the power transmission coil is greater than the impedance during the power transmission period. A contactless power supply method.

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