Wireless power supply system and method, and wireless power receiving system

Abstract

To provide a wireless power feed system, a method therefor, and a wireless power reception system in which, even when the impedance of a load-side circuit changes, impedance matching can be easily performed.SOLUTION: A wireless power feed system 1 performs power exchange between a power transmission coil 32 and a power reception coil 41 by a magnetic field resonance method. In the power reception coil 41, a plurality of coil regions 41A, 41B, and 41C which have different numbers of coil turns are selectable according to a connection position of a plurality of terminals disposed on the power reception coil 41. A controller 92 changes the inductance of the power reception coil 41 by switching among the plurality of terminals such that the difference between a load-side impedance of a circuit on a load 8 side from an input end IE of a power transmission device 3 and an input-side impedance of a circuit on an AC power source 5 side from the input end IE of the power transmission device 3 is relieved.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a wireless power supply system and method, and a wireless power receiving system. [Background technology]

[0002] In recent years, research and development of wireless power transfer systems using magnetic fields has been progressing. Known power transfer methods using such magnetism include an electromagnetic coupling (electromagnetic induction) method and a magnetic resonance method. The magnetic resonance method transmits power via a state in which magnetic fields generated by the coils of the resonant circuits are tightly coupled (magnetic resonance coupling) by transmitting magnetic field vibrations generated by the flow of AC current through a resonant circuit of a power transmitting device to a resonant circuit of a power receiving device, causing resonance. Wireless power transfer using the magnetic resonance method has the advantage of a longer power transfer distance compared to wireless power transfer using electromagnetic coupling (see, for example, Patent Document 1). While the magnetic resonance method also uses magnetic coupling, the method using resonance is referred to as the magnetic resonance method in this invention for ease of understanding.

[0003] In such a wireless power supply system, in order to transmit power efficiently, it is necessary to set the impedance of the load side circuit, including the power receiving device and load, as viewed from the input end (IE) of the power transmitting device to be equivalent to the impedance of the power source side as viewed from the input end (IE) of the power transmitting device.

[0004] Typically, various parameters of the resonant circuit of the power transmitting device and the resonant circuit of the power receiving device are set in advance so that impedance matching is achieved when the power transmitting coil of the power transmitting device and the power transmitting coil of the power receiving device are located at a predetermined relative position. Possible causes of such impedance mismatch include, for example, a change in the relative positional relationship between the power transmitting coil and the power receiving coil, and a change in the charging status of a load to be supplied with power, such as a battery or a motor.

[0005] Patent Document 2 discloses a configuration in which a resonant element and an excitation element are coupled by electromagnetic induction, and at the receiving side (power supply destination) where AC power is supplied from the resonant element through the excitation element and automatic matching device to a rectifier circuit, the automatic matching device and the excitation element form an impedance converter, and the automatic matching device adjusts the impedance of the resonant circuit having the resonant element according to a coupling coefficient that varies depending on the transmission distance, and the excitation element matches the impedance between the resonant element and the rectifier circuit. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-505369 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-50140 Summary of the Invention [Problem to be solved by the invention]

[0007] However, when achieving impedance matching by providing a resonant circuit separate from the power receiving coil as in the past, it is necessary to operate a variable inductor or variable capacitor while maintaining a resonant state in response to changes in impedance. Considering their responsiveness, the conditions for maintaining a resonant state and the conditions for impedance matching cannot be met simultaneously, resulting in a problem of difficulty in matching impedance in response to changes in the positional relationship between the power transmitting coil and the power receiving coil. There is also a problem of difficulty in matching impedance in response to changes in impedance caused by load fluctuations. Furthermore, power receiving devices with such impedance matching functionality tend to be expensive because they require high-performance components, etc. Furthermore, when the power receiving device is a mobile object or portable device, incorporating a complex mechanism in such a power receiving device is not practical due to factors such as weight, size, and heat generation.

[0008] Therefore, a technical problem arises that must be solved in order to easily perform impedance matching even when the impedance of the load side circuit fluctuates, and the present invention aims to solve this problem. [Means for solving the problem]

[0009] In order to achieve the above object, the wireless power supply system of the present invention comprises a power transmitting device having a power transmitting side resonant circuit including a power transmitting coil, a power receiving unit having a power receiving side resonant circuit including a power receiving coil and connectable to a load to which power received by the power receiving coil is supplied, and a control device that controls the power receiving unit, and is a wireless power supply system that transmits and receives power between the power transmitting coil and the power receiving coil using a magnetic field resonance method, wherein the power receiving coil is configured to be able to select multiple coil regions having different numbers of coil turns depending on the connection positions of multiple terminals provided on the power receiving coil, and the control device changes the inductance of the power receiving coil by switching the multiple terminals, thereby reducing the difference between the load side impedance, which is the impedance of the circuit from the input end of the power transmitting device to the load side, and the input side impedance, which is the impedance of the circuit from the input end of the power transmitting device to the power supply device side.

[0010] In addition, in order to achieve the above-mentioned object, the wireless power receiving system of the present invention is a wireless power receiving system that receives power transmitted using a magnetic field resonance method from a power transmitting device having a power transmitting side resonant circuit including a power transmitting coil, and includes a power receiving unit having a power receiving side resonant circuit including a power receiving coil, and is connectable to a load to which the power received by the power receiving coil is supplied, and the power receiving coil is configured to be able to select multiple coil areas having different numbers of coil turns depending on the connection positions of multiple terminals provided on the power receiving coil, and a control device that controls the power receiving unit changes the inductance of the power receiving coil by switching the multiple terminals, thereby reducing the difference between the load side impedance, which is the impedance of the circuit from the input end of the power transmitting device to the load side, and the input side impedance, which is the impedance of the circuit from the input end of the power transmitting device to the power supply device side.

[0011] Furthermore, in order to achieve the above-mentioned object, the wireless power supply method of the present invention is a wireless power supply method using a wireless power supply system that uses a magnetic field resonance method to transmit and receive power between the transmitting coil and the receiving coil, the wireless power supply system comprising: a power transmitting device having a transmitting-side resonant circuit including a transmitting coil; a power receiving unit having a receiving-side resonant circuit including a receiving coil, the power receiving device being connectable to a load to which power received by the receiving coil is supplied; and a control device that controls the power receiving unit, wherein the receiving coil is configured to be able to select from a plurality of coil regions having different numbers of coil turns depending on the connection positions of a plurality of terminals provided on the receiving coil, and the control device changes the inductance of the receiving coil by switching between the plurality of terminals, thereby reducing the difference between the load-side impedance, which is the impedance of the circuit from the input end of the power transmitting device to the load side, and the input-side impedance, which is the impedance of the circuit from the input end of the power transmitting device to the power supply device side. [Effects of the Invention]

[0012] Even if the impedance of the load side circuit fluctuates, the present invention selects an appropriate coil area from multiple coil areas with different numbers of coil turns and changes the strength of the magnetic field coupling (dense or dense magnetic field coupling) between the transmitting coil and the receiving coil, thereby mitigating the difference between the input side impedance and the load side impedance, thereby suppressing the generation of reflected waves at the input end and avoiding a decrease in power transmission efficiency and the resulting risk of system failure. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram illustrating a configuration of a wireless power supply system according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing the configuration of a drive coil. [Figure 3] 10 is a schematic diagram showing the positional relationship between a power transmission coil and three drive coil sections that are arranged offset in the axial direction of the coil axis. FIG. [Figure 4] FIG. 2 is a schematic diagram showing the configuration of a receiving coil. [Figure 5] FIG. 2 is a schematic diagram showing the positional relationship between a power transmitting coil and three coil regions of a power receiving coil. [Figure 6] FIG. 2 is a schematic diagram showing electrical wiring of a receiving coil. [Figure 7] FIG. 2 is a circuit diagram corresponding to the wireless power supply system. [Figure 8] FIG. 8 is an equivalent circuit diagram corresponding to the circuit diagram shown in FIG. [Figure 9] FIG. 2 is a schematic diagram showing a configuration of a first modified example of the wireless power supply system according to the first embodiment. [Figure 10] FIG. 10 is a schematic diagram showing the configuration of a second modified example of the wireless power supply system according to the first embodiment. [Figure 11] 10 is a schematic diagram showing the positional relationship between a power transmission coil and eight power supply coil sections that are arranged in a substantially spherical shape and inclined relative to the power transmission coil. FIG. [Figure 12] FIG. 10 is a schematic diagram illustrating a configuration of a wireless power supply system according to a second embodiment of the present invention. [Figure 13] FIG. 10 is a schematic diagram illustrating a configuration of a wireless power supply system according to a third embodiment of the present invention. [Figure 14] 1 is a schematic diagram showing the configurations of a drive coil, a power transmission coil, and a power receiving coil used in Examples 1 and 2. FIG. [Figure 15] 1 is a graph showing the experimental results of Example 1. [Figure 16] 10 is a graph showing the experimental results of Example 2. [Figure 17] 10 is a table showing combinations of drive coils and power receiving coils at various distances between the power transmitting coil and the power receiving coil when the load resistance is set to 50Ω in Example 2. [Figure 18] 10 is a table showing combinations of drive coils and power receiving coils at various distances between the power transmitting coil and the power receiving coil when the load resistance is set to 200Ω in Example 2. [Figure 19] 10 is a table showing combinations of drive coils and power receiving coils at various distances between the power transmitting coil and the power receiving coil when the load resistance is set to 500Ω in Example 2. [Figure 20] 10 is a graph showing power transmission efficiency in Example 2. [Figure 21] 10 is a graph showing the experimental results of Example 3 when the load resistance was set to 50 Ω. [Figure 22] 10 is a graph showing the experimental results of Example 3 when the load resistance was set to 500 Ω. [Figure 23] 10 is a graph showing the experimental results of Example 3 when the load resistance was set to 3079 Ω. [Figure 24] 11 is a table showing combinations of drive coils and power receiving coils at various distances between the power transmitting coil and the power receiving coil when the load resistance is set to 50Ω in Example 3. [Figure 25] 11 is a table showing combinations of drive coils and power receiving coils at various distances between the power transmitting coil and the power receiving coil when the load resistance is set to 500Ω in Example 3. [Figure 26] 11 is a table showing combinations of drive coils and power receiving coils at various distances between the power transmitting coil and the power receiving coil when the load resistance is set to 3079 Ω in Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0014] A wireless power supply system 1A according to one embodiment of the present invention and a wireless power supply method using the wireless power supply system 1A will be described with reference to the drawings. Note that, hereinafter, when referring to the number, numerical value, amount, range, etc. of components, unless otherwise specified or when it is clearly limited to a specific number in principle, the number is not limited to that specific number and may be more or less than the specific number.

[0015] Furthermore, when referring to the shape or positional relationship of components, etc., it includes things that are substantially similar or approximate to those shapes, etc., unless otherwise specified or when it is clearly considered otherwise in principle.

[0016] In addition, the drawings may exaggerate characteristic parts to make the features easier to understand, and the dimensional proportions of the components may not be the same as in reality. In addition, in cross-sectional views, hatching of some components may be omitted to make the cross-sectional structure of the components easier to understand.

[0017] <Wireless power supply system configuration> FIG. 1 is a schematic diagram showing the configuration of a wireless power supply system 1A. The wireless power supply system 1A uses magnetic field resonance to supply power to a power supply target 2 in a contactless manner. The power supply target 2 is, for example, a vehicle, a robotic air vehicle, an underwater robot, a capsule endoscope, a cardiac pacemaker, etc., and may be either a mobile device or an immobile device. Furthermore, during power supply, the power supply target 2 may be either moving or stationary. The wireless power supply system 1A includes a power transmitter 3 and a power receiver 4. The wireless power supply system 1A may also include a power supply device 5A including an AC power supply 5.

[0018] <Configuration of power transmission device> The power transmitting device 3 includes a drive coil 31, a power transmitting coil 32, and capacitors 33 and .

[0019] The drive coil 31 and the transmission coil 32 are formed by circularly winding a copper wire or the like having high electrical conductivity. Note that the current flowing through the copper wire flows more near the surface than in the center due to the influence of internal resistance. Therefore, when a litz wire made by twisting together multiple copper wires is used as the wire material for the drive coil 31 and the transmission coil 32, the surface area of ​​the litz wire is larger than that of a single copper wire of the same diameter, allowing for a larger current to flow and suppressing current loss.

[0020] The drive coil 31 is supplied with AC power from the AC power supply 5 of the power supply device 5A. The AC power is set to, for example, a frequency of 150 kHz and a voltage of 10 V, but the frequency and voltage of the AC power supply 5 can be changed as desired. Hereinafter, the contact point of the drive coil 31 on the AC power supply 5 side will be referred to as the "input end IE." In this embodiment, the drive coil 31 and the AC power supply 5 are directly connected via the input end IE. However, the drive coil 31 and the AC power supply 5 may be directly connected via the input end IE or indirectly connected via a coaxial cable or the like provided between the AC power supply 5 and the input end IE. In this case, if the impedance of the power supply matches the impedance of the coaxial cable or the like, the power supply end of the coaxial cable or the like does not cause power reflection or the like, and therefore does not pose a problem. Therefore, the input end IE refers to the load end of the coaxial cable or the like.

[0021] The drive unit 35 includes a power supply-side resonant circuit configured by connecting a drive coil 31 and a capacitor 33 in series. When an AC voltage having a frequency corresponding to a resonant frequency set by the inductance of the drive coil 31 and the capacitance of the capacitor 33 flows through the drive coil 31, an oscillating magnetic field is generated that penetrates the drive coil 31. The detailed configuration of the drive coil 31 will be described later.

[0022] The drive coil 31 and the power transmitting coil 32 are magnetically coupled, and the drive coil 31 supplies power to the power transmitting coil 32 using a magnetic resonance method. That is, the drive coil 31 and the power transmitting coil 32 are designed to resonate at a resonant frequency set according to the inductance of the drive coil 31 and the capacitance of the capacitor 33, which is approximately equal to a resonant frequency set according to the inductance of the power transmitting coil 32 and the capacitance of the capacitor 34. As a result, magnetic field oscillations at a specific frequency (resonant frequency) generated by an AC current flowing through the drive coil 31 are transmitted to the power transmitting coil 32, which resonates at the same specific frequency, generating an electromotive force in the power transmitting coil 32. Note that, although the magnetic resonance method is preferred for supplying power from the drive coil 31 to the power transmitting coil 32, which reduces the influence of the relative positions of the coils, an electromagnetic coupling method may also be used, in which an electromotive force is also generated in the power transmitting coil 32 via a magnetic flux that is generated when an AC current flows through the drive coil 31, penetrating the drive coil 31 in the coil axial direction. Furthermore, the magnetic field resonance method and the electromagnetic coupling method may be used in combination.

[0023] The power transmitting unit 36 ​​includes a power transmitting-side resonant circuit configured by connecting a power transmitting coil 32 and a capacitor 34 in series. When an AC voltage having a frequency corresponding to a resonant frequency set by the inductance of the power transmitting coil 32 and the capacitance of the capacitor 33 flows through the power transmitting coil 32, the power receiving coil 41 (described later) resonates, generating an electromotive force.

[0024] A reflected power detector 37 made up of a directional coupler is provided between the AC power supply 5 and the drive coil 31. The reflected power detector 37 detects the reflected power from the drive coil 31 side.

[0025] <Configuration of power receiving device> The power receiving device 4 is provided inside the power supply target 2. The power receiving device 4 includes a power receiving coil 41 and a capacitor .

[0026] The power receiving coil 41 is provided at a distance from the power transmitting coil 32 in the coil axial direction. The power receiving coil 41 is formed by circularly winding a copper wire or the like having high electrical conductivity. As with the drive coil 31 and the power transmitting coil 32, the power receiving coil 41 also preferably uses Litz wire as the wire material.

[0027] The power receiving unit 43 includes a power receiving-side resonant circuit configured by connecting a power receiving coil 41 and a capacitor 42 in series. The resonant frequency, which is set by the inductance of the power receiving coil 41 and the capacitance of the capacitor 42, is set to approximately match the resonant frequency of the power transmitting coil 32 and the capacitor 33. As a result, an induced current flows in the power receiving coil 41 due to oscillation of a magnetic field that is generated so as to penetrate the power transmitting coil 32 in the coil axial direction, and an oscillating magnetic field is generated so as to penetrate the power receiving coil 41 in the coil axial direction. At this time, the magnetic fields of the power transmitting coil 32 and the power receiving coil 41 resonate and are strongly coupled. The detailed configuration of the power receiving coil 41 will be described later.

[0028] The AC power received by the power receiving coil 41 through resonance is supplied to a load 8 via a rectifier circuit (AC-DC converter) 6 and a DC-DC converter 7. The load 8 is a motor, a battery, or the like that constitutes the power supply target 2.

[0029] The rectifier circuit 6 has four diodes 61 arranged on a bridge, performs full-wave rectification on the AC power received by the power receiving coil 41, and outputs a DC voltage. Reference numeral 62 denotes a capacitor that smoothes the DC voltage output by the rectifier circuit 6.

[0030] DC-DC converter 7 converts the rectified DC voltage into a preset constant voltage (for example, 12 V). The voltage output from DC-DC converter 7 is applied to load 8. Note that DC-DC converter 7 may be provided according to the required voltage, and may be omitted as appropriate.

[0031] <Configuration of impedance matching mechanism> Next, an impedance matching mechanism 9 will be described with reference to the drawings. The impedance matching mechanism 9 performs impedance matching to reduce the difference between the impedance of the circuit (load side circuit) from the input terminal IE to the power receiving device 4 side, i.e., the impedance of the circuit including the power transmitting device 3, the power receiving device 4, the rectifier circuit 6, the DC-DC converter 7, and the load 8 (hereinafter referred to as "load side impedance"), and the impedance of the circuit from the input terminal IE to the AC power source 5 side (hereinafter referred to as "input side impedance"). The power receiving device 4 and the impedance matching mechanism 9 constitute a wireless power receiving system 11.

[0032] 2, the impedance matching mechanism 9 controls the switching of switches 91a to 91d to supply power to at least one of three drive coil sections 31A, 31B, and 31C that make up the drive coil 31. Note that other configurations may be used instead of the switches 91a to 91d as long as they are capable of selectively supplying power to any one of the drive coil sections 31A, 31B, and 31C.

[0033] The drive coil 31 is divided into three drive coil sections 31A, 31B, and 31C. The three drive coil sections 31A, 31B, and 31C divide the drive coil 31 into three sections and are connected substantially in series. The drive coil sections 31A and 31B are connected via wiring 31AB, and the drive coil sections 31B and 31C are connected via wiring 31BC. Note that the wiring 31AB and 31BC may be omitted as necessary. The coil axes 31a, 31b, and 31c of the drive coil sections 31A, 31B, and 31C and the coil axis 32a of the power transmitting coil 32 are positioned approximately coaxially in the normal state. Note that the following description will be given taking the case where the drive coil 31 is divided into three drive coil sections 31A, 31B, and 31C as an example, but the number of drive coil sections may be two, four, or more.

[0034] The drive coil units 31A, 31B, and 31C are arranged such that the drive coil unit 31A is closest to the power transmission coil 32, and the drive coil units 31B, 31C are arranged in this order so that they are further away from the power transmission coil 32. Therefore, the strength of the magnetic field coupling with the power transmission coil 32 is set to be strongest for the drive coil unit 31A and weakest for the drive coil unit 31C. When power is transmitted between the drive coil 31 and the power transmission coil 32 using the magnetic field resonance method, efficient power transmission can be achieved by setting the inductances of the drive coil units 31A, 31B, and 31C to be equal to each other.

[0035] The switches 91a to 91d are switches formed of MOSFETs or the like for supplying current to the drive coil sections 31A, 31B, and 31C. The switches 91a and 91b are connected to an AC power supply 5. The switch 91a is configured to be able to switch between one end of the drive coil section 31C and the switch 91c side. The switch 91c is configured to be able to switch between one end of the drive coil section 31A and one end of the drive coil section 31B. The switch 91b is configured to be able to switch between the other end of the drive coil section 31C and the switch 91d side. The switch 91d is configured to be able to switch between the other end of the drive coil section 31A and the other end of the drive coil section 31B.

[0036] When power is to be supplied to drive coil unit 31A, switch 91a is switched to switch 91c, switch 91c is switched to one end of drive coil unit 31A, switch 91b is switched to switch 91d, and switch 91d is switched to the other end of drive coil unit 31A. When power is to be supplied to drive coil unit 31B, switch 91a is switched to switch 91c, switch 91c is switched to one end of drive coil unit 31B, switch 91b is switched to switch 91d, and switch 91d is switched to the other end of drive coil unit 31B. When power is to be supplied to drive coil unit 31C, switch 91a is switched to drive coil unit 31C, and switch 91b is switched to drive coil unit 31C.

[0037] When power is to be supplied to drive coil units 31A and 31B, switch 91a is switched to switch 91c, switch 91c is switched to one end of drive coil unit 31A, switch 91b is switched to switch 91d, and switch 91d is switched to the other end of drive coil unit 31B. When power is to be supplied to drive coil units 31B and 31C, switch 91a is switched to switch 91c, switch 91c is switched to one end of drive coil unit 31B, and switch 91b is switched to drive coil unit 31C.

[0038] Furthermore, when power is to be supplied to the drive coil sections 31A, 31B, and 31C, the switch 91a is switched to the switch 91c side, the switch 91c is switched to one end side of the drive coil section 31A, and the switch 91b is switched to the drive coil section 31B side.

[0039] The controller 92 controls the switching of the switches 91a to 91d in accordance with the magnitude of the reflected power detected by the reflected power detection unit 37. The controller 92 is configured by, for example, a CPU, a memory, etc. The functions of the controller 92 may be realized by control using software, or may be realized by operation using hardware. The controller 92 is functionally divided into a storage unit 93 and a control unit 94 (see FIG. 1).

[0040] Furthermore, since the strength of the magnetic field coupling between the drive coil sections 31A, 31B, and 31C and the transmission coil 32 weakens in inverse proportion to the distance of the drive coil sections 31A, 31B, and 31C from the transmission coil 32, as shown in Figure 3, the impedance of the circuit within the power transmission device 3 can be increased or decreased by supplying power to any of the drive coil sections 31A, 31B, and 31C which have different magnetic field coupling strengths with the transmission coil 32.

[0041] As shown in FIG. 4, the impedance matching mechanism 9 selects which of the three coil regions 41A, 41B, and 41C of the power receiving coil 41 to pass current to by controlling the switches 91e to 91f, which are connected to a terminal on one end of the power receiving coil 41 and two terminals provided between three power receiving coil sections 41a, each of which is formed by dividing the power receiving coil 41 into sections with approximately the same number of coil turns and connected substantially in series. The terminal on the other end of the power receiving coil 41 and the switch 91e are connected to a rectifier circuit 6. The controller 92 controls the switching of the switches 91e to 91f in accordance with the magnitude of the reflected power detected by the reflected power detector 37. The capacitances C1, C2, and C3 of the capacitor 42 correspond to the capacitances C1, C2, and C3 in FIG. 6, which will be described later. Other configurations may be used in place of the switches 91e to 91f as long as they are capable of selecting one of the coil regions 41A, 41B, and 41C. In the following, an example will be described in which the power receiving coil 41 is divided into three coil regions 41A, 41B, and 41C, but the number of power receiving coil regions may be two, or four or more.

[0042] 5A and 5B are schematic diagrams showing selective use of a part or all of the power receiving coil 41. Fig. 5A illustrates an example in which a coil region 41A corresponding to the total number of coil turns of the power receiving coil 41 is used, Fig. 5B illustrates an example in which a coil region 41B of the power receiving coil 41 that is close to the power transmitting coil 32 and corresponds to two-thirds of the total number of coil turns is used, and Fig. 5C illustrates an example in which a coil region 41C of the power receiving coil 41 that is close to the power transmitting coil 32 and corresponds to one-third of the total number of coil turns is used. The inductance of the power receiving coil 41 increases in proportion to the number of coil turns of the coil regions 41A, 41B, and 41C, so the inductance of coil region 41A is the largest, the inductance of coil region 41B is two-thirds that of coil region 41A, and the inductance of coil region 41C is one-third that of coil region 41A.

[0043] To maintain a resonant state between the power receiving coil 41 and the power transmitting coil 32, the capacitance of the capacitor 42 is adjusted appropriately depending on the selected coil region 41A, 41B, or 41C. Fig. 6 is a schematic diagram showing the electrical wiring of the power receiving coil 41. In Fig. 6, for ease of understanding, the three power receiving coil sections are shown spaced apart from one another, but the three power receiving coil sections do not necessarily need to be spaced apart.

[0044] Two MOSFETs 95a and 95b form switch 91e, and two MOSFETs 95c and 95d form switch 91f. When using coil region 41A of inductance (L1+L2+L3), coil region 41A can be selected by turning MOSFET 95a off, MOSFET 95b on, MOSFET 95c off, and MOSFET 95d on. At this time, capacitance C3 of capacitor 42 functions. The value of capacitance C3 is preset to form a resonant circuit with inductance (L1+L2+L3).

[0045] When using the coil region 41B of the inductance (L1+L2), the coil region 41B can be selected by turning off the MOSFET 95a, turning on the MOSFET 95b, turning on the MOSFET 95c, and turning off the MOSFET 95d. At this time, the capacitance C2 of the capacitor 42 functions. The value of the capacitance C2 is preset to form a resonant circuit with the inductance (L1+L2).

[0046] When using the coil region 41C of the inductance (L1), the coil region 41C can be selected by turning on the MOSFET 95a and turning off the MOSFET 95b (MOSFETs 95c and 95d can be either on or off). At this time, the capacitance C1 of the capacitor 42 functions. The value of the capacitance C1 is preset to form a resonant circuit with the inductance L1.

[0047] The controller 92 controls the switching of the switches 91a to 91d in accordance with the magnitude of the reflected power detected by the reflected power detection unit 37. As a result, regardless of which of the coil regions 41A, 41B, and 41C is selected, the resonant state between the power receiving coil 41 and the power transmitting coil 32 is maintained. Note that, although the switch 91e made up of MOSFETs 95a and 95b and the switch 91f made up of MOSFETs 95c and 95d are used in this embodiment, the configuration of the switches 91e and 91f is not limited to this.

[0048] Next, we will explain the causes of impedance mismatch, which is when the input impedance and the load impedance do not match. The greater the difference between the input impedance and the load impedance, the greater the power reflection and the lower the power transmission efficiency. Impedance mismatch occurs, for example, when the coupling coefficient between the power transmitting coil 32 and the power receiving coil 41 changes due to a change in the relative positions of the power transmitting coil 32 and the power receiving coil 41 or when a foreign object is interposed between the power transmitting coil 32 and the power receiving coil 41, or when the load impedance fluctuates due to a change in the state of the load 8 due to, for example, the battery charge status.

[0049] The impedance mismatch will be specifically described with reference to Figs. 7 and 8. Fig. 7 is a circuit diagram corresponding to the wireless power supply system 1A. In Fig. 7, "V" represents the voltage of the power supply 5, "Z s " is the impedance of the power supply 5 (input side impedance), "R0" is the parasitic resistance of the drive coil 31, "L0" is the inductance of the drive coil 31, "C0" is the capacitance of the capacitor 33, "I0" is the current flowing through the drive coil 31, "R1" is the parasitic resistance of the power transmission coil 32, "L1" is the inductance of the power transmission coil 32, "C1" is the capacitance of the capacitor 34, "I1" is the current flowing through the power transmission coil 32, "k 01 " is the coupling coefficient between the drive coil 31 and the power transmission coil 32, "R2" is the parasitic resistance of the power reception coil 41, and "R L " is the load resistance of the load 8, "L2" is the inductance of the receiving coil 41, "C2" is the capacitance of the capacitor 42, "I2" is the current flowing through the receiving coil 41, and "k 12' is the coupling coefficient between the power transmitting coil 32 and the power receiving coil 41.

[0050] Fig. 8 is an equivalent circuit diagram based on the circuit diagram shown in Fig. 7. The equivalent circuit diagram shown in Fig. 8 shows a state in which the drive coil 31 and the power transmission coil 32 are resonating, and the power transmission coil 32 and the power receiving coil 41 are resonating. The mutual inductance L0 between the drive coil 31 and the power transmission coil 32 is expressed as k 01 √(L0L1), and the mutual inductance L2 between the power transmitting coil 32 and the power receiving coil 41 is k 12 √(L1L2). "Z0" in FIG. 8 is the impedance (load-side impedance) of the circuit between the power supply 5 and the drive coil 31, that is, from the input end IE of the power transmission device 3 to the load 8 side. "Z1" is the impedance of the circuit between the drive coil 31 and the power transmission coil 32 to the load 8 side. "Z2" is the impedance of the circuit from the power receiving coil 41 to the load 8 side. The following formulas 1 to 3 are obtained from the equivalent circuit shown in FIG. 8.

[0051]

number

[0052]

number

[0053]

number

[0054] For example, as the power transmitting coil 32 and the power receiving coil 41 approach each other, the coupling coefficient “k 12 " increases, and it can be seen that, based on Equation 2, the impedance "Z1" increases, and based on Equation 3, the impedance "Z0" decreases.

[0055] Therefore, the impedance matching mechanism 9 has a coupling coefficient "k 12As the inductance "L2" of the power receiving coil 41 increases, the inductance "L2" of the power receiving coil 41 decreases. This suppresses an increase in the impedance "Z1" and a decrease in the impedance "Z0", thereby maintaining impedance matching.

[0056] Specifically, the reflected power detector 37 detects the reflected power from the drive coil 31, and the controller 92 monitors whether the impedance "Z0" falls below a predetermined threshold. That is, the controller 92 monitors whether the power transmitting coil 32 and the power receiving coil 41 have come closer than a predetermined distance based on the magnitude of the reflected power.

[0057] When the impedance "Z0" falls below a predetermined threshold, the controller 92 selects one of the coil regions 41A, 41B, and 41C by switching the switches 91e to 91f shown in FIG. 4, and changes the inductance "L2" of the power receiving coil 41.

[0058] In addition to changing the inductance "L2" of the power receiving coil 41, the coupling coefficient "k 01 In other words, when the impedance "Z0" falls below a predetermined threshold, the control unit 94 may control the power receiving unit 43 and the drive unit 35. Specifically, the inductance "L2" of the power receiving coil 41 may be reduced, and the coupling coefficient "k 01 By increasing "Z0", it is possible to further suppress the decrease in impedance "Z0". This makes it possible to cope with a case where the distance between the power transmitting coil 32 and the power receiving coil 41 changes even further.

[0059] Furthermore, the load-side impedance "Z0" is adjusted by the control unit 94 by selecting the coil regions 41A, 41B, and 41C described above to adjust (coarsely adjust) the inductance "L2" of the power receiving coil 41, and then by switching the switches 91a to 91d shown in FIG. 2, the drive coil sections 31A, 31B, and 31C are selected, and the coupling coefficient "k 01" may be performed by a procedure for adjusting (fine-tuning) ".

[0060] In this way, the wireless power supply system 1A of this embodiment is a wireless power supply system 1A that includes a power transmitting device 3 having a power transmitting side resonant circuit including a power transmitting coil 32, a power receiving unit 43 having a power receiving side resonant circuit including a power receiving coil 41, a power receiving device 4 that is connectable to a load 8 to which power received by the power receiving coil 41 is supplied, and a controller 92 that controls the power receiving unit 43, and that transmits and receives power between the power transmitting coil 32 and the power receiving coil 41 using a magnetic field resonance method, and the power receiving coil 41 is configured to be able to select multiple coil regions 41A, 41B, 41C having different numbers of coil turns depending on the connection positions of multiple terminals provided on the power receiving coil 41, and the controller 92 changes the inductance of the power receiving coil 41 by switching between the multiple terminals, thereby reducing the difference between the load side impedance, which is the impedance of the circuit from the input terminal IE of the power transmitting device 3 to the load 8 side, and the input side impedance, which is the impedance of the circuit from the input terminal IE of the power transmitting device 3 to the AC power source 5 side.

[0061] With this configuration, when the load side impedance does not match the input side impedance, multiple coil regions 41A, 41B, 41C having different numbers of coil turns are appropriately selected, and the strength of the magnetic field coupling between the transmitting coil 32 and the receiving coil 41 (the density of the magnetic field coupling) is changed to alleviate the difference between the input side impedance and the load side impedance, thereby suppressing the generation of reflected waves at the input terminal IE and avoiding system failures due to reduced power transmission efficiency and reduced transmitted power.

[0062] Furthermore, the wireless power supply system 1A according to this embodiment is configured such that the controller 92 switches between multiple terminals to adjust the inductance of the selected coil region 41A, 41B, 41C and the capacitance of the capacitor 42 arranged in series with the selected coil region 41A, 41B, 41C so as to maintain magnetic field resonance between the transmitting coil 32 and the receiving coil 41.

[0063] With this configuration, regardless of which of the coil regions 41A, 41B, and 41C is selected, the capacitance of the capacitor 42 is preset according to the inductance of the selected coil region 41A, 41B, and 41C so that magnetic field resonance between the transmitting coil 32 and the receiving coil 41 can be maintained, thereby making it easy to maintain magnetic field resonance.

[0064] In addition, the wireless power supply system 1A according to this embodiment is configured such that the power transmission device 3 further includes a drive unit 35 having a drive coil 31 that is arranged to be magnetically coupled with the power transmission coil 32 and transmits power to the power transmission coil 32, and the controller 92 controls the drive unit 35 to change the coupling strength of the magnetic field coupling between the power transmission coil 32 and the drive coil 31.

[0065] With this configuration, by changing the strength of the magnetic field coupling between the drive coil 31 and the transmission coil 32, the impedance of the circuit within the drive unit 35 increases or decreases, and the difference between the input side impedance and the load side impedance is alleviated, thereby suppressing the generation of reflected waves at the input terminal IE and avoiding system failures due to reduced power transmission efficiency and reduced transmitted power.

[0066] Furthermore, in the wireless power supply system 1A according to this embodiment, the power transmitting device 3 is arranged between the AC power source 5 and the driving coil 31 and further includes a reflected power detection unit 37 that detects the reflected power at the driving coil 31, and the controller 92 is configured to control the power receiving unit 43 or the driving unit 35 depending on the magnitude of the reflected power detected by the reflected power detection unit 37.

[0067] With this configuration, by changing the coupling strength in the magnetic field coupling between the transmitting coil 32 and the receiving coil 41, or the coupling strength in the magnetic field coupling between the driving coil 31 and the transmitting coil 32, depending on the detection result of the reflected power detection unit 37, the difference between the input side impedance and the load side impedance is alleviated, thereby suppressing the generation of reflected waves at the input terminal IE and avoiding system failures due to reduced power transmission efficiency and reduced transmitted power.

[0068] Furthermore, the wireless power feeding method using the wireless power feeding system 1A according to this embodiment is a wireless power feeding method using the wireless power feeding system 1A, which includes a power transmitting device 3 having a power transmitting side resonant circuit including a power transmitting coil 32, a power receiving unit 43 having a power receiving side resonant circuit including a power receiving coil 41, a power receiving device 4 connectable to a load 8 to which power received by the power receiving coil 41 is supplied, and a controller 92 controlling the power receiving unit 43, and which transmits and receives power between the power transmitting coil 32 and the power receiving coil 41 using a magnetic field resonance method, wherein the power receiving coil 41 is configured to be able to select from multiple coil regions 41A, 41B, 41C having different numbers of coil turns depending on the connection positions of multiple terminals provided on the power receiving coil 41, and the controller 92 changes the inductance of the power receiving coil 41 by switching between the multiple terminals, thereby reducing the difference between the load side impedance, which is the impedance of the circuit from the input terminal IE of the power transmitting device 3 to the load 8 side, and the input side impedance, which is the impedance of the circuit from the input terminal IE of the power transmitting device 3 to the AC power source 5 side.

[0069] With this configuration, when the load side impedance does not match the input side impedance, multiple coil regions 41A, 41B, 41C having different numbers of coil turns are appropriately selected, and the strength of the magnetic field coupling between the transmitting coil 32 and the receiving coil 41 is changed to reduce the difference between the input side impedance and the load side impedance, thereby suppressing the generation of reflected waves at the input terminal IE and avoiding system failures due to reduced power transmission efficiency and reduced transmitted power.

[0070] In addition, in the wireless power supply method according to this embodiment, the power transmission device 3 further includes a drive unit 35 having a drive coil 31 that is arranged to be magnetically coupled with the power transmission coil 32 and transmits power to the power transmission coil 32, and the controller 92 controls the drive unit 35 to change the coupling strength in the magnetic field coupling between the power transmission coil 32 and the drive coil 31.

[0071] With this configuration, by changing the strength of the magnetic field coupling between the drive coil 31 and the transmission coil 32, the impedance of the circuit within the drive unit 35 increases or decreases, and the difference between the input side impedance and the load side impedance is alleviated, thereby suppressing the generation of reflected waves at the input terminal IE and avoiding system failures due to reduced power transmission efficiency and reduced transmitted power.

[0072] Furthermore, the wireless power receiving system 11 of this embodiment is a wireless power receiving system 11 that receives power transmitted using a magnetic field resonance method from a power transmitting device 3 that has a power transmitting side resonant circuit including a power transmitting coil 32, and is equipped with a power receiving unit 43 that has a power receiving side resonant circuit including a power receiving coil 41, and is connectable to a load 8 to which the power received by the power receiving coil 41 is supplied, and the power receiving coil 41 is configured to be able to select multiple coil regions 41A, 41B, 41C having different numbers of coil turns depending on the connection positions of multiple terminals provided on the power receiving coil 41, and a controller 92 changes the inductance of the power receiving coil 41 by switching between the multiple terminals, thereby reducing the difference between the load side impedance, which is the impedance of the circuit from the input terminal IE of the power transmitting device 3 to the load 8 side, and the input side impedance, which is the impedance of the circuit from the input terminal IE of the power transmitting device 3 to the AC power source 5 side.

[0073] With this configuration, when the load side impedance does not match the input side impedance, multiple coil regions 41A, 41B, 41C having different numbers of coil turns are appropriately selected, and the strength of the magnetic field coupling between the transmitting coil 32 and the receiving coil 41 is changed to reduce the difference between the input side impedance and the load side impedance, thereby suppressing the generation of reflected waves at the input terminal IE and avoiding system failures due to reduced power transmission efficiency and reduced transmitted power.

[0074] Furthermore, in the above-described embodiment, the cause of fluctuation in the load side impedance has been described as fluctuation in the load current due to the on / off switching of the DC-DC converter 7, but the cause of fluctuation in the load side impedance is not limited to this.

[0075] For example, in the present embodiment, the input impedance and the load impedance are pre-matched when the DC-DC converter 7 is idling. However, the input impedance and the load impedance may be pre-matched when the DC-DC converter 7 transitions from idling to ON, or when the load impedance stabilizes after the DC-DC converter 7 is turned ON.

[0076] In addition, in the wireless power supply system 1A shown in FIG. 1, the reflected power detection unit 37 is disposed within the power transmission device 3 and is provided between the input terminal IE of the power transmission device 3 and the drive coil 31, but the location at which the reflected power detection unit 37 is disposed is not limited to this.

[0077] For example, as in the wireless power transfer system 1B shown in FIG. 11 , the reflected power detection unit 37 may be disposed within the power supply device 5A, and the reflected power detection unit 37 may be disposed between the AC power supply 5 and the input terminal IE of the power transmitter 3. Furthermore, as in the wireless power transfer system 1C shown in FIG. 26 , the input terminal IE of the power transmitter 3 may be provided within the reflected power detection unit 37, and the reflected power detection unit 37 may be disposed between the power supply device 5A and the power transmitter 3. As in the wireless power transfer system 1A, these wireless power transfer systems 1B and 1C can also mitigate the difference between the load-side impedance and the input-side impedance, suppress the generation of reflected waves at the input terminal IE, and avoid system failures due to reduced power transfer efficiency and reduced transmitted power. The configuration of the wireless power transfer systems 1A, 1B, and 1C to be adopted can be appropriately selected depending on the location and environment where the wireless power transfer system is installed, and the configurations of the power transfer target 2 and the power transmitter 3.

[0078] Furthermore, because the reflected power detection unit 37 has impedance due to a parasitic resistance or a parasitic inductance, an error occurs in the value detected by the reflected power detection unit 37. The magnitude of the error in the detected value is expected to differ depending on the configuration of the power supply target 2 (for example, motor driving or battery charging, which have relatively large impedance fluctuations, or operation of a home appliance, etc., which have relatively small impedance fluctuations). Therefore, wireless power supply systems 1A, 1B, and 1C may be constructed, and an external tester may be used to measure the power at the input terminal IE and the impedances on the power supply side and load side for each system. For example, a configuration that minimizes the error or error fluctuation of the reflected power detection unit 37 may be appropriately selected depending on the configuration of the power supply target 2. Note that the error in the value detected by the reflected power detection unit 37 may be optimally adjusted by offset design at the design stage or by offset adjustment during shipping inspection of each product.

[0079] Next, modified examples of this embodiment will be described. Note that the various modified examples have the same configuration as the above-described embodiment except for the configuration described below.

[0080] <Variation 1> The drive coil 31 according to this modification may include eight drive coil portions 31A to 31H arranged in a spherical shape, as shown in, for example, FIGS. 11(a) to 11(c).

[0081] The drive coil 31 is made up of drive coil sections 31A to 31H that are inclined to each other with their centers aligned. The drive coil sections 31A to 31H are one coil divided into eight sections, and are connected essentially in series. Although details of the connection between the drive coil sections 31A to 31H are omitted, similar to FIG. 2, they are connected by a switch or the like (not shown) so that power from the AC power supply 5 can be supplied to at least one of the drive coil sections 31A to 31H.

[0082] 11(a), drive coil section 31A is housed within power transmission coil 32 with its coil axis 31a substantially aligned with the coil axis 32a of power transmission coil 32, i.e., without tilting relative to power transmission coil 32. As shown in FIG. 11(b), drive coil section 31C is housed within power transmission coil 32 with a portion thereof tilted at approximately 45 degrees relative to power transmission coil 32. As shown in FIG. 11(c), drive coil section 31E is housed within power transmission coil 32 with a portion thereof tilted at approximately 90 degrees relative to power transmission coil 32. Furthermore, drive coil sections 31B, 31D, and 31F to 31H are housed within power transmission coil 32 with a portion thereof tilted at approximately 22.5 degrees, approximately 67.5 degrees, approximately 112.5 degrees, approximately 135 degrees, and approximately 157.5 degrees relative to power transmission coil 32, respectively.

[0083] At this time, the larger the opposing area between the drive coil 31 and the power transmission coil 32, the tighter the magnetic field coupling between them. That is, because the coil axis 31a of the drive coil section 31A and the coil axis 32a of the power transmission coil 32 are positioned coaxially, the magnetic field coupling between the drive coil section 31A and the power transmission coil 32 is the tightest. The magnetic field coupling between the drive coil section 31E and the power transmission coil 32 is the loosest.

[0084] With this configuration, for example, the three drive coil sections 31A, 31C, and 31E can be switched appropriately to perform impedance matching. That is, when the load impedance is large relative to the input impedance, supplying power to the drive coil section 31A as shown in Fig. 11(a) increases the magnetic coupling between the drive coil 31 and the power transmitting coil 32, thereby reducing the impedance of the circuit within the power transmitting device 3. As a result, the load impedance at the input terminal IE decreases, and the difference with the input impedance is alleviated.

[0085] 11(b), when the load impedance is small relative to the input impedance, supplying power to drive coil section 31C, which is inclined relative to power transmission coil 32 compared to drive coil section 31A, reduces the magnetic field coupling between drive coil 31 and power transmission coil 32, increasing the impedance of the circuit within power transmission device 3. As a result, the load impedance at input terminal IE increases, and the difference with the input impedance is alleviated.

[0086] Furthermore, when the load side impedance decreases further, as shown in Figure 11(c), by supplying power to the drive coil section 31E that is perpendicular to the transmission coil 32, the magnetic field coupling between the drive coil 31 and the transmission coil 32 becomes weaker, and the impedance of the circuit within the power transmission device 3 increases further.As a result, the load side impedance at the input terminal IE increases, and the difference with the input side impedance is alleviated.

[0087] With this configuration, power is selectively supplied to at least one of the drive coil sections 31A to 31H, so that the coupling strength between the drive coil 31 and the power transmission coil 32 can be adjusted.

[0088] Furthermore, the number of drive coil sections constituting spherical drive coil 31 according to this modification is not limited to 8, and may be any number equal to or greater than 2. Furthermore, the inclination of drive coil sections 31A to 31H relative to power transmission coil 32 according to this modification is set in the range of 0 to 180 degrees, but may be set in the range of -90 to +90 degrees taking into account the phase of the coils.

[0089] Furthermore, the drive coil 31 is not limited to being housed within the power transmission coil 32, and may be arranged outside the power transmission coil 32. Furthermore, some of the drive coil sections 31A to 31H may be arranged inside the power transmission coil 32, and the other drive coil sections 31A to 31H may be arranged outside the power transmission coil 32. Note that the inclination of the drive coil 31 with respect to the power transmission coil 32 is determined by the coupling coefficient k 01By configuring the impedance adjustment range at the angle of each drive coil 31 to be switchable so that is a geometric progression, the impedance adjustment range at the angle of each drive coil 31 becomes approximately constant, and impedance matching can be performed more stably.

[0090] <Variation 2> The impedance matching mechanism 9 may be a coil moving mechanism that moves the drive coil 31 relative to the power transmission coil 32.

[0091] Such a coil moving mechanism may, for example, be one that slides the drive coil sections 31A, 31B, and 31C in a direction perpendicular to the coil axis 32a so that the coil axes 31a, 31b, and 31c move relatively away from or closer to (align with) the coil axis 32a while maintaining the coil axes 31a, 31b, and 31c in an approximately parallel state to the coil axis 32a.

[0092] When the coil axes 31a, 31b, and 31c are coaxial with the coil axis 32a of the power transmitting coil 32, the magnetic field coupling with the power transmitting coil 32 becomes tight (the coupling strength (coupling coefficient) becomes large). On the other hand, when the coil axes 31a, 31b, and 31c are offset from the coil axis 32a of the power transmitting coil 32 in a direction perpendicular to the coil axis 31a, the magnetic field coupling with the power transmitting coil 32 becomes loose (the coupling strength (coupling coefficient) becomes small).

[0093] The impedance may be optimized by roughly adjusting the impedance by moving the drive coil 31 relative to the power transmission coil 32 using the coil movement mechanism, and then fine-tuning the impedance by controlling the switches 91a to 91d. In this case, the impedance can be finely adjusted at high speed, allowing smooth optimization even when the impedance changes suddenly.

[0094] <Variation 3> In the above-mentioned variant example 2, a coil moving mechanism is exemplified in which the drive coil sections 31A, 31B, and 31C slide in a direction perpendicular to the coil axis 32a while maintaining the coil axes 31a, 31b, and 31c in a substantially parallel state to the coil axis 32a. However, the coil moving mechanism may be configured to move the drive coil sections 31A, 31B, and 31C parallel to the axial directions of the coil axes 31a, 32a, and 33a and the coil axis 32a.

[0095] Here, the closer the drive coil sections 31A, 31B, and 31C are to the power transmission coil 32, the closer the magnetic field coupling with the power transmission coil 32 becomes (the larger the coupling coefficient), and the farther the drive coil sections 31A, 31B, and 31C are from the power transmission coil 32, the looser the magnetic field coupling with the power transmission coil 32 becomes (the smaller the coupling coefficient).

[0096] The impedance may be optimized by roughly adjusting the impedance by moving the drive coil 31 relative to the power transmission coil 32 using the coil movement mechanism, and then fine-tuning the impedance by controlling the switches 91a to 91d. In this case, the impedance can be finely adjusted at high speed, allowing smooth optimization even when the impedance changes suddenly.

[0097] <Variation 4> In the above-described embodiment, the driving coil 31 is exemplified as being composed of driving coil sections 31A, 31B, and 31C in which the coil axes 31a, 31b, and 31c are arranged approximately coaxially, but the configuration of the driving coil 31 is not limited to this.

[0098] For example, the drive coil 31 may include drive coil sections 31A, 31B, and 31C in which the coil axes 31a, 31b, and 31c are arranged substantially parallel to each other and offset from each other.

[0099] At this time, the larger the opposing area is, the tighter the magnetic field coupling between drive coil 31 and power transmission coil 32. Then, by controlling the switching of switches 91a to 91d, power is selectively supplied to at least one of drive coil sections 31A, 31B, and 31C, so that the strength of the magnetic field coupling between drive coil 31 and power transmission coil 32 (the density of the magnetic field coupling) can be adjusted.

[0100] <Variation 5> In the above-described embodiment, the drive coil 31 is made up of drive coil portions 31A, 31B, and 31C formed in substantially the same shape, but the drive coil portions 31A, 31B, and 31C may have different shapes.

[0101] For example, the drive coil 31 may be configured in a spiral shape in which the coil diameter expands and contracts on approximately the same plane, with the coil axes 31a, 31b, and 31c arranged approximately coaxially, and the drive coil sections 31A, 31B, and 31C being set to gradually smaller coil diameters in this order and the coil height increasing.

[0102] At this time, the smaller the difference in coil diameter, the tighter the magnetic field coupling between drive coil 31 and power transmission coil 32. By controlling the switching of switches 91a to 91d, power is selectively supplied to at least one of drive coil sections 31A, 31B, and 31C, so the strength of the coupling between drive coil 31 and power transmission coil 32 can be adjusted.

[0103] <Variation 6> Furthermore, the drive coil 31 may be configured such that the coil axes 31a, 31b, and 31c are arranged approximately coaxially, and the drive coil sections 31A, 31B, and 31C are arranged approximately on the same plane, and further, the coil diameters of the drive coil sections 31A, 31B, and 31C are set to gradually smaller diameters in this order, so that the coil diameter gradually decreases from the outer periphery toward the center on the same plane.

[0104] At this time, the smaller the difference in coil diameter, the tighter the magnetic field coupling between drive coil 31 and power transmission coil 32. Then, by controlling the switching of switches 91a to 91d, power is selectively supplied to at least one of drive coil sections 31A, 31B, and 31C, so that the strength of the magnetic field coupling between drive coil 31 and power transmission coil 32 (the tightness or looseness of the magnetic field coupling) can be adjusted.

[0105] <Second embodiment> Next, a wireless power supply system 1D according to a second embodiment of the present invention will be described with reference to the drawings. Fig. 12 is a schematic diagram showing the configuration of the wireless power supply system 1D according to the second embodiment. The wireless power supply system 1D according to this embodiment differs from the wireless power supply system 1A according to the first embodiment described above in the following respects, but has other configurations in common. Therefore, the same reference numerals are used for the common configurations, and redundant explanations will be omitted.

[0106] The wireless power supply system 1D of this embodiment maintains impedance matching, for example, when the power transmitting device 3 and the power receiving device 4 are fixed so that the distance between the power transmitting coil 32 and the power receiving coil 41 remains approximately constant, and the impedance "Z0" varies as charging of the battery corresponding to the load 8 progresses.

[0107] The power receiving device 4 is provided with a measuring unit 96 that is provided between the DC-DC converter 7 and the load 8 and that measures at least one of the load voltage and the load current supplied to the load 8. For example, when power is supplied to the load 8, the load voltage increases to a constant voltage and the load current increases rapidly. At this time, the load side impedance "Z0" decreases rapidly. On the other hand, the input side impedance "Z s " is fixed at a predetermined value (for example, 50 Ω), and the input impedance "Z s " and the load side impedance "Z0" do not match, and a reflected wave occurs at the input terminal IE, which may reduce the power transmission efficiency or cause a system failure due to insufficient power transmission.

[0108] Therefore, the controller 92 switches the switches 91a to 91d in accordance with the measurement result of the measurement unit 96 to adjust the strength of the magnetic field coupling between the drive coil 31 and the power transmission coil 32, thereby adjusting the coupling coefficient "k 01 " to increase or decrease the impedance of the circuit in the power transmitting device 3. Alternatively, the controller 92 switches the switches 91e to 91f in accordance with fluctuations in the load-side impedance "Z0" to adjust the strength of the magnetic field coupling between the power transmitting coil 32 and the power receiving coil 41, thereby adjusting the coupling coefficient "k 12 " is adjusted to increase or decrease the impedance of the circuit in the power receiving device 4. As a result, the load side impedance "Z0" increases and the input side impedance "Z s " will be reduced.

[0109] With this configuration, the wireless power supply system 1D of this embodiment changes the coupling strength in the magnetic field coupling between the transmitting coil 32 and the receiving coil 41, or the coupling strength in the magnetic field coupling between the driving coil 31 and the transmitting coil 32, depending on the measurement results of the measurement unit 96, thereby reducing the difference between the input side impedance and the load side impedance, thereby suppressing the generation of reflected waves at the input terminal IE and avoiding system failures due to reduced power transmission efficiency and reduced transmitted power.

[0110] <Third embodiment> Next, a wireless power supply system 1E according to a third embodiment of the present invention will be described with reference to the drawings. Fig. 13 is a schematic diagram showing the configuration of the wireless power supply system 1E according to the third embodiment. The wireless power supply system 1E according to this embodiment differs from the wireless power supply system 1A according to the first embodiment described above in the following respects, but has the same configuration as the first embodiment. Therefore, the same reference numerals are used for the common configuration, and redundant description will be omitted.

[0111] For example, when the relative position between the power transmitting coil 32 and the power receiving coil 41 changes as the power supply target 2 moves, specifically, when the power receiving coil 41 approaches the power transmitting coil 32, the strength of the magnetic coupling between the power transmitting coil 32 and the power receiving coil 41 increases, and when the power receiving coil 41 moves away from the power transmitting coil 32, the strength of the magnetic coupling between the power transmitting coil 32 and the power receiving coil 41 decreases, and the state of magnetic coupling between the power transmitting coil 32 and the power receiving coil 41 changes. Therefore, the wireless power supply system 1E according to this embodiment maintains impedance matching when the relative position between the power transmitting coil 32 and the power receiving coil 41 changes.

[0112] The power transmitting device 3 includes a relative position measuring unit 38 that measures the relative position between the power transmitting coil 32 and the power receiving coil 41. The relative position measuring unit 38 is, for example, a laser length measuring device or a three-dimensional camera. The relative position measuring unit 38 may be provided in the power receiving device 4. Preferably, the relative position measuring unit 38 measures not only the distance between the power transmitting coil 32 and the power receiving coil 41 but also the relative tilt of the axes of the respective coils. The controller 92 calculates the load impedance "Z0" based on the measurement result of the relative position measuring unit 38. When the load impedance "Z0" falls below a predetermined threshold, the controller 92 selects one of the coil regions 41A, 41B, and 41C by switching the switches 91e to 91f, and changes the inductance "L2" of the power receiving coil 41.

[0113] Alternatively, in addition to changing the inductance "L2" of the receiving coil 41, the coupling coefficient "k 01 In other words, when the impedance "Z0" falls below a predetermined threshold, the controller 92 may control the power receiving unit 43 and the drive unit 35. Specifically, the controller 92 changes the inductance "L2" of the power receiving coil 41 by selecting the coil regions 41A, 41B, and 41C described above to reduce the inductance "L2" of the power receiving coil 41, and also changes the coupling coefficient "k01 By increasing the impedance "Z0", it is possible to further suppress the decrease in the impedance "Z0". This makes it possible to cope with a case where the distance between the power transmitting coil 32 and the power receiving coil 41 changes even further.

[0114] With this configuration, the wireless power supply system 1E of this embodiment changes the coupling strength in the magnetic field coupling between the transmitting coil 32 and the receiving coil 41, or the coupling strength in the magnetic field coupling between the driving coil 31 and the transmitting coil 32, depending on the measurement results of the relative position measurement unit 38, thereby reducing the difference between the input side impedance and the load side impedance, thereby suppressing the generation of reflected waves at the input terminal IE and making it possible to avoid system failures caused by reduced power transmission efficiency and reduced transmitted power.

[0115] In addition, in the above-described embodiments, the drive coil 31, the power transmitting coil 32, and the power receiving coil 41 are all placed in a resonant state in order to reduce the imaginary part of the impedance to zero and thereby suppress the generation of reactive power. However, even if the capacitor 33 is not connected to the drive coil 31, for example, reactive power occurs in the input impedance, but power transmission itself is possible, so only the power transmitting coil 32 and the power receiving coil 41 may be placed in a resonant state.

[0116] Furthermore, in each of the above-described embodiments, a three-coil system configuration including the drive coil 31, the power transmitting coil 32, and the power receiving coil 41 has been described as an example, but the wireless power transfer system may be a two-coil system including only the power transmitting coil 32 and the power receiving coil 41 without providing the drive coil 31. In this case, the power transmitting coil 32 is divided into multiple power transmitting coil sections, and the relative positions of the power transmitting coil sections and the power receiving coil 41 are changed, thereby enabling control of the load-side impedance.

[0117] In a two-coil system consisting of a transmitting coil 32 and a receiving coil 41, if the position of the transmitting coil 32 is moved to vary the load-side impedance, the coil axis 32a of the transmitting coil 32 and the coil axis of the receiving coil 41 will not be aligned coaxially, which may result in a decrease in power transmission efficiency. In contrast, a three-coil system consisting of a driving coil 31, a transmitting coil 32, and a receiving coil 41 transmits power to the transmitting coil 32 via the driving coil 31, and by adjusting the strength of the magnetic coupling between the driving coil 31 and the transmitting coil 32 without changing the positional relationship between the transmitting coil 32 and the receiving coil 41, the load-side impedance can be controlled and good power transmission efficiency can be maintained.

[0118] Furthermore, in the above-described embodiments, a three-coil system including a drive coil 31, a power transmitting coil 32, and a power receiving coil 41 has been described as an example. However, a wireless power transfer system may also be configured using a four-coil system including a second power receiving coil in addition to the power receiving coil 41. In this case, the power receiving coil 41 is set to a resonant frequency substantially equal to that of the power transmitting coil 32, and power is transmitted by magnetic field resonance. The power receiving coil 41 and the second power receiving coil are arranged in a non-contact manner, and power is transmitted by electromagnetic coupling (electromagnetic induction) or magnetic field resonance. In a four-coil system, the power transmitting coil 32 and the power receiving coil 41 are resonant coils independent of other electrical circuits, and therefore the resonant frequency does not change during operation, making the system easier to design and enabling a longer power transmission distance. [Example]

[0119] Example 1 An experiment (Example 1) will be described below, which was conducted using the wireless power supply system 1A according to the first embodiment to confirm changes in the load-side impedance "Z0" and the impedance "Z1" when the load resistance of the load 8 is changed. The structures of the drive coil 31, the power transmitting coil 32, and the power receiving coil 41 used in this experiment are shown in FIG.

[0120] Drive coil Drive coil 31 is formed to have a diameter of 300 mm and is housed within power transmission coil 32 having a diameter of 350 mm. Drive coil 31 is made up of ten drive coil sections 31A to 31J arranged in a spherical shape with different inclinations. Drive coil section 31A is arranged parallel to power transmission coil 32 (tilt of approximately 0 degrees), drive coil section 31B is arranged tilted by approximately 10 degrees with respect to power transmission coil 32, drive coil section 31C is arranged tilted by approximately 20 degrees with respect to power transmission coil 32, drive coil section 31D is arranged tilted by approximately 30 degrees with respect to power transmission coil 32, drive coil section 31E is arranged tilted by approximately 40 degrees with respect to power transmission coil 32, drive coil section 31F is arranged tilted by approximately 50 degrees with respect to power transmission coil 32, drive coil section 31G is arranged tilted by approximately 60 degrees with respect to power transmission coil 32, drive coil section 31H is arranged tilted by approximately 70 degrees with respect to power transmission coil 32, drive coil section 31I is arranged tilted by approximately 80 degrees with respect to power transmission coil 32, and drive coil section 31J is arranged perpendicular to power transmission coil 32 (tilt of approximately 90 degrees).

[0121] The drive coil sections 31A to 31J use Litz wires with a wire diameter of 0.04 mm and a diameter of 0.9 mm, and the inductance is set to 278 μH and the capacitance is set to 4.05 nF.

[0122] Passive coil The receiving coil 41 is configured to be selectable from four coil regions 41A, 41B, 41C, and 41D. The receiving coil 41 has a diameter of 350 mm and is made of Litz wire with a wire diameter of 0.04 mm and a diameter of 0.9 mm. The number of coil turns, inductance, and capacitor resistance of each coil region 41A, 41B, 41C, and 41D were set as follows: Coil area 41A Coil turns: 56, inductance: 1488 μH, capacitance: 0.756 nF Coil area 41B Coil turns: 28, inductance: 744 μH, capacitance: 1.512 nF Coil area 41C Coil turns: 10, inductance: 266 μH, capacitance: 4.234 nF Coil area 41D Coil turns: 5, inductance: 133 μH, capacitance: 8.367 nF

[0123] The resonant frequencies of the resonant circuit including the drive coil 31, the resonant circuit including the power transmitting coil 32, and the resonant circuit including the power receiving coil 41 are each set to 150 Hz.

[0124] Experimental Procedure First, with receiving coil 41 fixed to coil region 41A and drive coil 31 fixed to drive coil section 31A, transmitting coil 32 and receiving coil 41 were moved closer to each other by 50 mm starting from 350 mm, and the load impedance "Z0" was measured at each distance. The results are shown in Fig. 15.

[0125] 15, it can be seen that the load-side impedance "Z0" decreases as the power transmitting coil 32 and the power receiving coil 41 approach each other. This is because, according to Equation 1 and Equation 2, the coupling coefficient "k 12 This is because as "Z1" increases, the impedance "Z1" increases while the load side impedance "Z0" decreases.

[0126] <Example 2> Next, a description will be given of an experiment (Example 2) conducted to confirm that the load-side impedance "Z0" can be maintained substantially constant in the wireless power supply system 1A by selecting optimal drive coil sections 31A-31J and coil regions 41A-41D in accordance with the value input from the reflected power detection section 37. The drive coil 31 and the power receiving coil 41 used in this example are the same as those in Example 1.

[0127] Experimental Procedure In this embodiment, the load-side impedance "Z0" when any of the drive coil sections 31A to 31J and coil regions 41A to 41D is selected is obtained in advance by experiment or the like and stored in the storage unit 93, and it is possible to select the optimal combination of the drive coil sections 31A to 31J and coil regions 41A to 41D to maintain the load-side impedance "Z0" at approximately 50 Ω. Note that it is also possible to store in advance in the storage unit 93 the numerical values ​​of the inductance, capacitance, resonant frequency, etc. when the drive coil sections 31A to 31J and coil regions 41A to 41D are selected, and to select the optimal drive coil sections 31A to 31J and coil regions 41A to 41D according to the reflected power detected by the reflected power detection unit 37.

[0128] The load resistance of the load 8 was changed to 50 Ω, 200 Ω, and 500 Ω, and the load-side impedance "Z0" was measured when the transmitting coil 32 and the receiving coil 41 were moved closer to each other by 50 mm starting from 350 mm. The results are shown in Fig. 16.

[0129] 17 shows a table illustrating combinations of drive coils 31 and power receiving coils 41 selected for each distance when the load resistance is set to 50 Ω and the power transmitting coil 32 and power receiving coil 41 are moved closer in 50 mm increments starting from 350 mm. 18 shows a table illustrating combinations of drive coils 31 and power receiving coils 41 selected for each distance when the load resistance is set to 200 Ω and the power transmitting coil 32 and power receiving coil 41 are moved closer in 50 mm increments starting from 350 mm. 19 shows a table illustrating combinations of drive coils 31 and power receiving coils 41 selected for each distance when the load resistance is set to 500 Ω and the power transmitting coil 32 and power receiving coil 41 are moved closer in 50 mm increments starting from 350 mm. 17 to 19, the drive coil types "2-1" to "2-10" correspond to the drive coil sections 31A to 31J, respectively, and the power receiving coil types "1-1" to "1-4" correspond to the coil regions 41A to 41D, respectively.

[0130] FIG. 20 shows the transmission efficiency calculated based on Equation 4 at a load resistance of 50 Ω.

[0131]

number

[0132] 16 shows that the load impedance "Z0" is maintained at approximately 50 Ω when the distance between the power transmitting coil 32 and the power receiving coil 41 is 350 mm or less, regardless of whether the load resistance is 50 Ω, 200 Ω, or 500 Ω. Also, FIG. 20 shows that the transmission efficiency at this time is maintained at approximately 90% or more.

[0133] That is, by selecting the optimum coil regions 41A to 41D and adjusting the inductance of the power receiving coil 41, the load impedance "Z0" can be easily controlled and impedance matching can be performed. Also, by selecting the drive coil sections 31A to 31J, the coupling coefficient "k 01 By adjusting ", impedance matching can be performed more easily.

[0134] Example 3 Next, a description will be given of an experiment and a simulation (Example 3) conducted to confirm that the load-side impedance "Z0" falls within a predetermined range even when the load resistance changes and the distance between the power transmitting coil 32 and the power receiving coil 41 changes in the wireless power feeding system 1A. The power receiving coil 41 used in this example is the same as that in Example 1.

[0135] Drive coil This embodiment differs from the first embodiment in that the drive coil 31 is made up of six drive coil sections arranged in a spherical shape with different inclinations, but the other configurations are the same as those of the first embodiment. Each drive coil section has a coupling coefficient "k 01 " are arranged as follows so that the intervals are √(78 / 32), or 1.56 times. Drive coil part No.3-1 Coupling coefficient "k 01 ": Approx. 0.45, Inclination angle: 0° Drive coil part No.3-2 Coupling coefficient "k 01": Approx. 0.41, Inclination angle: 22° Drive coil part No.3-3 Coupling coefficient "k 01 ": Approx. 0.26, Inclination angle: 49° Drive coil part No.3-4 Coupling coefficient "k 01 : Approx. 0.17, Inclination angle: 64° Drive coil part No.3-5 Coupling coefficient "k 01 ": Approx. 0.11, Inclination angle: 73° Drive coil part No.3-6 Coupling coefficient "k 01 : Approx. 0.07, Inclination angle: 79°

[0136] Experimental Procedure The load resistance was set to 50 Ω, 500 Ω, and 3079 Ω, assuming the charging state of the load 8, and the changes in the load-side impedance "Z0" when the transmitting coil 32 and the receiving coil 41 were brought closer in increments of 50 mm starting from 350 mm are shown in Figures 21 to 23. Note that Figure 21 shows the case where the load resistance was set to 50 Ω, Figure 22 shows the case where the load resistance was set to 500 Ω, and Figure 23 shows the case where the load resistance was set to 3079 Ω.

[0137] 24 shows a table illustrating combinations of drive coils 31 and power receiving coils 41 selected for each distance when the load resistance is set to 50 Ω and the power transmitting coil 32 and power receiving coil 41 are moved closer in 50 mm increments starting from 350 mm. FIG. 25 shows a table illustrating combinations of drive coils 31 and power receiving coils 41 selected for each distance when the load resistance is set to 500 Ω and the power transmitting coil 32 and power receiving coil 41 are moved closer in 50 mm increments starting from 350 mm. FIG. 26 shows a table illustrating combinations of drive coils 31 and power receiving coils 41 selected for each distance when the load resistance is set to 3079 Ω and the power transmitting coil 32 and power receiving coil 41 are moved closer in 50 mm increments starting from 350 mm. Note that the power receiving coil types "1-1" to "1-4" in FIGS. 24 to 26 correspond to coil regions 41A to 41D, respectively.

[0138] 21 to 23 show that, regardless of whether the load resistance of the load 8 is 50Ω, 500Ω, or 3079Ω, by appropriately selecting the drive coil 31 and the receiving coil 41, the change in the load-side impedance "Z0" can be kept within a range of 32 to 78Ω with respect to the target value of 50Ω. In other words, a power reflection rate of 5% or less can be achieved, and impedance matching can be achieved regardless of changes in the distance between the transmitting coil 32 and the receiving coil 41 or changes in the load resistance of the load 8.

[0139] Furthermore, the present invention can be modified in various ways other than those described above without departing from the spirit of the present invention, and it goes without saying that the present invention also covers such modifications. [Explanation of symbols]

[0140] 1A, 1B, 1C, 1D, 1E: Wireless power supply system 11: Wireless power receiving system 2: Power supply object 3: Power transmission equipment 31: Drive coil 31A~31H: Drive coil section 31a to 31c: Coil shaft (of the drive coil) 32: Transmission coil 32a: Coil axis (of the transmitting coil) 33, 34: Capacitor 35: Drive unit 36: Power transmission section 37: Reflected power detection section 38: Relative position measurement unit 4: Power receiving device 41: Receiving coil 41A, 41B, 41C, 41D: Coil area 42: Capacitor 43: Power receiving unit 5: AC power supply 5A: Power supply 6: Rectifier circuit 61: Diode 62: Capacitor 7: DC-DC converter 8: Load 9: Impedance matching mechanism 91a~91f: Switch 92: Controller 93: Storage section 94: Control unit 95a, 95b, 95c, 95d: MOSFETs 96: Measuring part IE: Input terminal

Claims

1. a power transmitting device including a power transmitting side resonant circuit including a power transmitting coil; a power receiving device including a power receiving unit having a power receiving-side resonant circuit including a power receiving coil, the power receiving unit being connectable to a load to which power received by the power receiving coil is supplied; a control device that controls the power receiving unit; a wireless power transfer system that transfers and receives power between the power transmitting coil and the power receiving coil using a magnetic field resonance method, the power receiving coil is configured to be able to select from a plurality of coil regions having different numbers of coil turns according to connection positions of a plurality of terminals provided on the power receiving coil; The control device changes the inductance of the receiving coil by switching the multiple terminals, thereby reducing the difference between the load-side impedance, which is the impedance of the circuit from the input end of the power transmitting device to the load side, and the input-side impedance, which is the impedance of the circuit from the input end of the power transmitting device to the power supply device side.

2. 2. The wireless power supply system according to claim 1, wherein the control device adjusts the inductance of the selected coil region and the capacitance of a capacitor arranged in series with the selected coil region by switching the multiple terminals so as to maintain magnetic field resonance between the transmitting coil and the receiving coil.

3. the power transmitting device further includes a power supply unit having a drive coil that is arranged to be magnetically coupled with the power transmitting coil and that transmits power to the power transmitting coil by using a magnetic field resonance method; The wireless power supply system according to claim 1 , wherein the control device controls the power supply unit so as to change a coupling strength of a magnetic field coupling between the power transmitting coil and the drive coil.

4. the power transmitting device further includes a reflected power detecting unit disposed between the power supply device and the drive coil and detecting reflected power at the drive coil; 4. The wireless power supply system according to claim 3, wherein the control device controls the power receiving unit or the power supply unit depending on the magnitude of the reflected power detected by the reflected power detection unit.

5. the power receiving device further includes a measurement unit that measures a load current or a load voltage in the load; The wireless power supply system according to claim 3 , wherein the control device controls the power receiving unit or the power supply unit in accordance with the value detected by the measurement unit.

6. a relative position measurement unit for measuring a relative position between the power transmitting coil and the power receiving coil; The wireless power supply system according to claim 3 , wherein the control device controls the power receiving unit or the power supply unit in accordance with the value measured by the relative position measurement unit.

7. a power supply device having an AC power source; a power transmitting device connected to the power supply device at an input end and including a power transmitting side resonant circuit including a power transmitting coil; a power receiving device including a power receiving unit having a power receiving-side resonant circuit including a power receiving coil, the power receiving unit being connectable to a load to which power received by the power receiving coil is supplied; a control device that controls the power receiving unit; a wireless power transfer system that transfers and receives power between the power transmitting coil and the power receiving coil using a magnetic field resonance method, the power receiving coil is configured to be able to select from a plurality of coil regions having different numbers of coil turns according to connection positions of a plurality of terminals provided on the power receiving coil; the control device changes the inductance of the power receiving coil by switching the plurality of terminals, and reduces a difference between a load-side impedance, which is the impedance of a circuit from the input end of the power transmitting device to the load side, and an input-side impedance, which is the impedance of a circuit from the input end of the power transmitting device to the power supply device side; the power transmitting device further includes a power supply unit having a drive coil that is arranged to be magnetically coupled with the power transmitting coil and that transmits power to the power transmitting coil by using a magnetic field resonance method; The wireless power supply system is characterized in that the control device controls the power supply unit to change the coupling strength of the magnetic field coupling between the power transmission coil and the drive coil.

8. the power supply device includes a reflected power detection unit disposed between the AC power supply and an input terminal of the power transmission device, the reflected power detection unit detecting reflected power from the power transmission device side; The wireless power supply system according to claim 7 , wherein the control device controls the power receiving unit or the power supply unit depending on the magnitude of the reflected power detected by the reflected power detection unit.

9. an input end of the power transmitting device is located inside, and the reflected power detecting unit detects reflected power from the driving coil side; The wireless power supply system according to claim 7 , wherein the control device controls the power receiving unit or the power supply unit depending on the magnitude of the reflected power detected by the reflected power detection unit.

10. A wireless power receiving system that receives power transmitted by a power transmitting device using a magnetic resonance method, the power transmitting device including a power transmitting side resonance circuit including a power transmitting coil, a power receiving unit having a power receiving-side resonant circuit including a power receiving coil, and capable of being connected to a load to which the power received by the power receiving coil is supplied; the power receiving coil is configured to be able to select from a plurality of coil regions having different numbers of coil turns according to connection positions of a plurality of terminals provided on the power receiving coil; A wireless power receiving system characterized in that a control device that controls the power receiving unit changes the inductance of the power receiving coil by switching the multiple terminals, thereby reducing the difference between the load side impedance, which is the impedance of the circuit from the input end of the power transmitting device to the load side, and the input side impedance, which is the impedance of the circuit from the input end of the power transmitting device to the power supply device side.

11. The wireless power receiving system of claim 10, wherein the control device adjusts the inductance of the selected coil region and the capacitance of a capacitor arranged in series with the selected coil region by switching the multiple terminals so as to maintain magnetic field resonance between the transmitting coil and the receiving coil.

12. a power transmitting device including a power transmitting side resonant circuit including a power transmitting coil; a power receiving device including a power receiving unit having a power receiving-side resonant circuit including a power receiving coil, the power receiving unit being connectable to a load to which power received by the power receiving coil is supplied; a control device that controls the power receiving unit; a wireless power feeding method using a wireless power feeding system that transmits and receives power between the power transmitting coil and the power receiving coil using a magnetic field resonance method, the power receiving coil is configured to be able to select from a plurality of coil regions having different numbers of coil turns according to connection positions of a plurality of terminals provided on the power receiving coil; The wireless power supply method is characterized in that the control device changes the inductance of the receiving coil by switching the multiple terminals, thereby reducing the difference between the load side impedance, which is the impedance of the circuit from the input end of the power transmission device to the load side, and the input side impedance, which is the impedance of the circuit from the input end of the power transmission device to the power supply device side.

13. the power transmitting device further includes a power supply unit having a drive coil that is arranged to be magnetically coupled with the power transmitting coil and that transmits power to the power transmitting coil by using a magnetic field resonance method; The wireless power feeding method according to claim 12 , wherein the control device controls the power feeding unit so as to change a coupling strength of a magnetic field coupling between the power transmitting coil and the drive coil.

14. 14. The wireless power supply method according to claim 13, wherein the load side impedance is adjusted by the control device by switching the terminals of the power receiving coil to perform coarse adjustment, and then by controlling the power supply unit to perform fine adjustment.

Images