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

Abstract

To provide a wireless power supply system and method and a wireless power transmission system that mitigate reduction in power transmission efficiency even when impedance of a load side circuit has varied.SOLUTION: A wireless power supply system 1 for transmitting and receiving power using magnetism comprises: a power transmission device 3 comprising a power transmission side resonance circuit 36 including a power transmission coil 32; a power reception device 4 comprising a power reception side resonance circuit 43 including a power reception coil 41; a load 8 to which power received via the power reception coil 41 is supplied; a measurement unit 95 for measuring load current or load voltage at the load 8; and an impedance matching mechanism 9 that depending on a measurement result of the measurement unit 95, performs impedance matching processing of mitigating a difference between load side impedance, impedance of a circuit on the load 8 side from an input end IE of the power transmission device 3, and input side impedance, impedance of a circuit on the AC power supply 5 side from the input end IE of the power transmission device 3.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to a wireless power supply system and method, and a wireless power transmission system. [Background technology]

[0002] In recent years, research and development of wireless power transfer systems utilizing magnetic fields has been progressing. Two known methods of power transfer using magnetism are electromagnetic coupling (electromagnetic induction) and magnetic field resonance. In the magnetic field resonance method, the vibration of the magnetic field generated by the flow of alternating current through the resonant circuit of the power transmission device is transmitted to the resonant circuit of the power receiving device, causing resonance. As a result, power is transmitted through a state in which the magnetic fields generated by the coils of each resonant circuit are strongly coupled (magnetic field resonant coupling). Wireless power transfer using the magnetic field resonance method has the advantage of a longer power transfer distance compared to wireless power transfer using the electromagnetic coupling method (see, for example, Patent Document 1). Although the magnetic field resonance method also utilizes magnetic coupling, in this invention, for the sake of ease of understanding, the method that utilizes resonance is referred to as the magnetic field resonance method.

[0003] In such wireless power supply systems, in order to transmit power efficiently, the impedance of the load-side circuit, including the receiving device and load, as viewed from the power transmission device, must be set to be equivalent to the impedance of the power supply side as viewed from the power transmission device. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-505369 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, the aforementioned load-side circuit is connected to drive components such as batteries and motors, and these batteries and motors become the load. Therefore, the current flowing through the load-side circuit can fluctuate depending on the operating state of the batteries and motors. In wireless power supply systems, the impedance of the load-side circuit fluctuates in accordance with the fluctuations in the current flowing through the load-side circuit. As a result, the impedance of the load-side circuit and the impedance of the power source, as seen from the perspective of the power transmission device, no longer match, leading to a significant decrease in transmission efficiency and a reduction in transmitted power, which in turn can cause system failure.

[0006] Therefore, even if the impedance of the load-side circuit fluctuates, technical challenges arise that need to be addressed in order to mitigate the decrease in power transmission efficiency, and the present invention aims to solve these challenges. [Means for solving the problem]

[0007] To achieve the above objective, the wireless power supply system according to the present invention is a wireless power supply system that transmits and receives power using magnetism, comprising: a power transmission device equipped with a power transmission side resonant circuit including a power transmission coil; a power receiving device equipped with a power receiving side resonant circuit including a power receiving coil; a load to which the power received via the power receiving coil is supplied; a measuring unit for measuring the load current or load voltage at the load; and an impedance matching mechanism that performs impedance matching processing to mitigate the difference between the load side impedance, which is the impedance of the circuit on the load side from the input terminal of the power transmission device, and the input side impedance, which is the impedance of the circuit on the power supply device side from the input terminal of the power transmission device, according to the measurement results of the measuring unit.

[0008] Furthermore, in order to achieve the above objective, the wireless power supply system according to the present invention is a wireless power supply system that transmits and receives power using magnetism, comprising: a power transmission device equipped with a power transmission side resonant circuit including a power transmission coil; a power receiving device equipped with a power receiving side resonant circuit including a power receiving coil; a load to which power received via the power receiving coil is supplied; and an impedance matching mechanism that performs impedance matching processing to mitigate the difference between the load side impedance, which is the impedance of the circuit on the load side from the input terminal of the power transmission device, and the input side impedance, which is the impedance of the circuit on the power supply device side from the input terminal of the power transmission device, wherein the power transmission device is provided so as to be magnetically coupled with the power transmission coil and provides power to the power transmission coil, the power supply coil is divided into a plurality of power supply coil sections with different relative positions to the power transmission coil, and is configured to be able to supply power to at least one of the plurality of power supply coil sections, and the impedance matching mechanism adjusts the coupling strength in the magnetic field coupling between the power transmission coil and the power supply coil by supplying power to at least one of the plurality of power supply coil sections.

[0009] Furthermore, in order to achieve the above objective, the wireless power supply method according to the present invention is a wireless power supply method using a wireless power supply system that transmits and receives power using magnetism, comprising: a power transmission device equipped with a power transmission side resonant circuit including a power transmission coil; a power receiving device equipped with a power receiving side resonant circuit including a power receiving coil; a load to which power received via the power receiving coil is supplied; and a measuring unit for measuring the load current or load voltage at the load, wherein an impedance matching mechanism is used to mitigate the difference between the load side impedance, which is the impedance of the circuit on the load side from the input terminal of the power transmission device, and the input side impedance, which is the impedance of the circuit on the power supply device side from the input terminal of the power transmission device, according to the measurement result of the measuring unit.

[0010] Furthermore, in order to achieve the above objective, the wireless power transmission system according to the present invention is a wireless power transmission system that transmits power to a power receiving device using magnetism, and comprises a power transmission device that includes a power transmission side resonant circuit including a power transmission coil and transmits power to a load via the power receiving device, and an impedance matching mechanism that performs impedance matching processing to mitigate the difference between the load side impedance, which is the impedance of the circuit on the load side from the input terminal of the power transmission device, and the input side impedance, which is the impedance of the circuit on the power supply side from the input terminal of the power transmission device, according to the load current or load voltage at the load. [Effects of the Invention]

[0011] This invention reduces the difference between the input impedance and the load impedance even when the impedance of the load-side circuit fluctuates. As a result, the generation of reflected waves at the input terminal is suppressed, and the risk of decreased power transmission efficiency and associated system failures can be avoided. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram showing the configuration of a wireless power supply system relating to one embodiment of the present invention. [Figure 2] This is a schematic diagram showing the configuration of an impedance matching mechanism. [Figure 3] This is a circuit diagram for a wireless power transfer system. [Figure 4] This is an equivalent circuit diagram corresponding to the circuit diagram shown in Figure 3. [Figure 5] This graph shows the relationship between load voltage and load current. [Figure 6] This graph shows the relationship between load current and load impedance. [Figure 7] This is a schematic diagram showing the positional relationship between the power transmission coil and the three power supply coil sections, which are positioned offset in the axial direction of the coil axis. [Figure 8] This graph shows the relationship between the distance from the power supply coil to the power transmission coil and the load resistance. [Figure 9] FIG. 1 is a schematic view showing how the coil moving mechanism slides the power supply coil in a direction perpendicular to the coil axis. [Figure 10] FIG. 2 is a schematic view showing how the coil moving mechanism slides the power supply coil parallel to the coil axis. [Figure 11] FIG. 3 is a schematic view showing the positional relationship between the power transmission coil and three power supply coil portions arranged offset in a direction perpendicular to the axial direction of the coil axis. [Figure 12] FIG. 4 is a schematic view showing the positional relationship between the power transmission coil and eight power supply coil portions arranged in a substantially spherical shape inclined with respect to the power transmission coil. [Figure 13] FIG. 5 is a schematic view showing the positional relationship between the power transmission coil and three power supply coil portions forming a power supply coil formed in a spiral shape. [Figure 14] FIG. 6 is a schematic view showing the positional relationship between the power transmission coil and three power supply coil portions arranged on the same plane. [[ID=十七]] DETAILED DESCRIPTION OF THE INVENTION

[0013] A wireless power supply system 1 according to an embodiment of the present invention and a wireless power supply method using the wireless power supply system 1 will be described based on the drawings. In the following, when referring to the number of components, numerical values, amounts, ranges, etc., unless otherwise specified or clearly limited to a specific number in principle, it is not limited to that specific number, and it may be more or less than the specific number.

[0014] Also, when referring to the shape and positional relationship of components, etc., unless otherwise specified or clearly not considered to be so in principle, it includes those substantially approximating or similar to the shape, etc.

[0015] Also, the drawings may be exaggerated, such as enlarging characteristic portions for easy understanding of the characteristics, and the dimensional ratios of the components are not necessarily the same as the actual ones. Also, in the cross-sectional view, in order to make the cross-sectional structure of the components easy to understand, the hatching of some components may be omitted.

[0016] <Configuration of the wireless power supply system> Figure 1 is a schematic diagram showing the configuration of the wireless power supply system 1. The wireless power supply system 1 uses magnetic field resonance to supply power to the power supply target object 2 in a non-contact manner. The power supply target object 2 can be, for example, a vehicle, a robotic flying object, an underwater robot, a capsule endoscope, a cardiac pacemaker, etc., and may be either a movable or immovable device. Furthermore, the power supply target object 2 may be moving or stationary at the time of power supply. The wireless power supply system 1 comprises a power transmission device 3 and a power receiving device 4.

[0017] <Configuration of power transmission equipment> The power transmission device 3 includes a power supply coil 31, a power transmission coil 32, and capacitors 33 and 34.

[0018] The power supply coil 31 and the power transmission coil 32 are formed by winding copper wire or the like, which has high electrical conductivity, in a circular shape. Note that the current flowing through the copper wire flows more near the surface than in the center due to the effect of internal resistance. Therefore, when Litz wire, which is made by twisting multiple copper wires together, is used as the wire material for the power supply coil 31 and the power transmission coil 32, the surface area of ​​the Litz wire is larger compared to a single copper wire of the same diameter, allowing more current to flow and suppressing current loss.

[0019] AC power is supplied to the power supply coil 31 from the AC power supply 5. 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 arbitrarily. Hereinafter, the contact on the AC power supply 5 side of the power supply coil 31 will be referred to as the "input terminal IE". In this embodiment, the case in which the power supply coil 31 and the AC power supply 5 are directly connected via the input terminal IE will be explained as an example, but the power supply coil 31 and the AC power supply 5 may be directly connected via the input terminal IE or indirectly connected via a coaxial cable or the like provided between the AC power supply 5 and the input terminal IE. In this case, if the impedance of the power supply matches the impedance of the coaxial cable, etc., the power supply side end of the coaxial cable, etc. will not be affected by power reflection, etc., and the input terminal IE will mean the load side end of the coaxial cable, etc.

[0020] The power supply coil 31 and capacitor 33 are connected in series to form a power supply side resonant circuit 35. When an AC voltage with a frequency corresponding to the resonant frequency set by the inductance of the power supply coil 31 and the capacitance of the capacitor 33 flows through the power supply coil 31, an oscillating magnetic field is generated that penetrates the power supply coil 31. The detailed configuration of the power supply coil 31 will be described later.

[0021] The power supply coil 31 and the power transmission coil 32 are magnetically coupled, and the power supply coil 31 supplies power to the power transmission coil 32 using a magnetic field resonance method. That is, the resonant frequency set according to the inductance of the power supply coil 31 and the capacitance of the capacitor 33 is approximately equal to the resonant frequency set according to the inductance of the power transmission coil 32 and the capacitance of the capacitor 34, and the power supply coil 31 and the power transmission coil 32 are designed to resonate. As a result, the vibration of the magnetic field at a specific frequency (resonant frequency) generated when an alternating current flows through the power supply coil 31 is transmitted to the power transmission coil 32, and an electromotive force is generated in the power transmission coil 32 when it resonates at the same specific frequency. Although a magnetic field resonance method is preferred for supplying power from the power supply coil 31 to the power transmission coil 32 because it reduces the influence of the relative positions of the coils, an electromagnetic coupling method is also acceptable, in which an electromotive force is generated in the power transmission coil 32 via the magnetic flux generated in the direction of the coil axis when an alternating current flows through the power supply coil 31. Furthermore, the magnetic resonance method and the electromagnetic coupling method may be used in combination.

[0022] The transmission coil 32 and capacitor 34 are connected in series to form a transmission-side resonant circuit 36. When an AC voltage with a frequency corresponding to the resonant frequency set by the inductance of the transmission coil 32 and the capacitance of the capacitor 33 flows through the transmission coil 32, the receiving coil 41, described later, resonates and generates an electromotive force.

[0023] <Configuration of the power receiving device> The power receiving device 4 is installed inside the object to be powered 2. The power receiving device 4 includes a power receiving coil 41 and a capacitor 42.

[0024] The receiving coil 41 is provided with a gap in the coil axis direction from the transmitting coil 32. The receiving coil 41 is formed by winding copper wire or the like, which has high electrical conductivity, in a circular shape. It is preferable to use Litz wire for the receiving coil 41, similar to the supply coil 31 and the transmitting coil 32.

[0025] The receiving coil 41 and the capacitor 42 are connected in series to form a receiving-side resonant circuit 43. The resonant frequency set by the inductance of the receiving coil 41 and the capacitance of the capacitor 42 is set to approximately coincide with the resonant frequency of the transmitting coil 32 and the capacitor 33. As a result, vibrations in the magnetic field generated in the direction of the coil axis of the transmitting coil 32 induce a current to flow in the receiving coil 41, and an oscillating magnetic field is generated in the direction of the coil axis of the receiving coil 41. At this time, the magnetic fields of the transmitting coil 32 and the receiving coil 41 resonate and are strongly coupled.

[0026] The AC power received by the resonant receiving coil 41 is supplied to the load 8 via a rectifier circuit (AC-DC converter) 6 and a DC-DC converter 7. The load 8 is a motor, battery, or other component of the powered object 2.

[0027] The rectifier circuit 6 consists of four diodes 61 arranged in a bridge configuration. The receiving coil 41 performs full-wave rectification on the AC power it receives, outputting a DC voltage. Reference numeral 62 denotes a capacitor that smooths the DC voltage output by the rectifier circuit 6.

[0028] The DC-DC converter 7 converts the rectified DC voltage to a preset constant voltage (for example, 12V). The voltage output from the DC-DC converter 7 is applied to the load 8. Note that the DC-DC converter 7 can be placed according to the required voltage and may be omitted as appropriate.

[0029] <Configuration of Impedance Matching Mechanism> Next, an impedance matching mechanism 9, which performs impedance matching processing to mitigate the difference between the impedance of the circuit from the input terminal IE to the power receiving device 4 side, i.e., the circuit including the power transmitting device 3, power receiving device 4, rectifier circuit 6, DC-DC converter 7, and load 8 (load side circuit) (hereinafter referred to as "load side impedance") and the impedance of the circuit from the input terminal IE to the AC power supply 5 side (hereinafter referred to as "input side impedance"), will be explained based on Figure 2. Note that the power transmitting device 3 and the impedance matching mechanism 9 constitute the wireless power transmission system 11.

[0030] The impedance matching mechanism 9 supplies power to at least one of the three power supply coil sections 31A, 31B, and 31C that constitute the power supply coil 31 by switching control of switches 91a to 91d. Note that other configurations may be used instead of switches 91a to 91d, as long as power can be selectively supplied to any of the power supply coil sections 31A, 31B, and 31C.

[0031] The power supply coil 31 is divided into three power supply coil sections 31A, 31B, and 31C. The three power supply coil sections 31A, 31B, and 31C divide the power supply coil 31 into three parts and are essentially connected in series. Power supply coil sections 31A and 31B are connected via wiring 31AB, and power supply coil sections 31B and 31C are connected via wiring 31BC. Wiring 31AB and 31BC may be omitted if necessary. The coil axes 31a, 31b, and 31c of the power supply coil sections 31A, 31B, and 31C and the coil axis 32a of the power transmission coil 32 are normally located approximately coaxially. In the following explanation, the case in which the power supply coil 31 is divided into three power supply coil sections 31A, 31B, and 31C is used as an example, but the number of power supply coil sections may be two, four or more, or any number of sections.

[0032] The power supply coils 31A, 31B, and 31C are arranged such that power supply coil 31A is closest to the power transmission coil 32, and the remaining coils are further away from the power transmission coil 32 in that order. Therefore, the magnetic field coupling strength with the power transmission coil 32 is set to be strongest for power supply coil 31A and weakest for power supply coil 31C. When power is transmitted between the power supply coil 31 and the power transmission coil 32 using a magnetic field resonance method, power can be transmitted efficiently by setting the inductances of power supply coils 31A, 31B, and 31C to be equal.

[0033] Switches 91a to 91d are three-way switches for supplying current to the power supply coils 31A, 31B, and 31C. Switches 91a and 91b are connected to the AC power supply 5. Switch 91a is configured to switch between one end of the power supply coil 31C and the switch 91c side. Switch 91c is configured to switch between one end of the power supply coil 31A and one end of the power supply coil 31B. Switch 91b is configured to switch between the other end of the power supply coil 31C and the switch 91d side. Switch 91d is configured to switch between the other end of the power supply coil 31A and the other end of the power supply coil 31B.

[0034] When supplying power to the power supply coil section 31A, switch 91a is switched to the switch 91c side, switch 91c is switched to one end of the power supply coil section 31A, switch 91b is switched to the switch 91d side, and switch 91d is switched to the other end of the power supply coil section 31A. When supplying power to the power supply coil section 31B, switch 91a is switched to the switch 91c side, switch 91c is switched to one end of the power supply coil section 31B, switch 91b is switched to the switch 91d side, and switch 91d is switched to the other end of the power supply coil section 31B. Furthermore, when supplying power to the power supply coil section 31C, switch 91a is switched to the power supply coil section 31C side, and switch 91b is switched to the power supply coil section 31C side.

[0035] Furthermore, when supplying power to the power supply coils 31A and 31B, switch 91a is switched to switch 91c, switch 91c is switched to one end of the power supply coil 31A, switch 91b is switched to switch 91d, and switch 91d is switched to the other end of the power supply coil 31B. Furthermore, when supplying power to the power supply coils 31B and 31C, switch 91a is switched to switch 91c, switch 91c is switched to one end of the power supply coil 31B, and switch 91b is switched to the power supply coil 31C side.

[0036] Furthermore, when supplying power to the power supply coils 31A, 31B, and 31C, switch 91a is switched to the switch 91c side, switch 91c is switched to one end of the power supply coil 31A side, and switch 91b is switched to the power supply coil 31B side.

[0037] The switching control of switches 91a to 91d is controlled by the controller 92. The controller 92 is composed of, for example, a CPU, memory, etc. The functions of the controller 92 may be implemented by software control or by hardware operation. The controller 92 is functionally divided into a storage unit 93 and a control unit 94 (see Figure 1).

[0038] Furthermore, by supplying power to at least one of the power supply coils 31A, 31B, and 31C, the load-side impedance, which is the circuit impedance on the load side from the input terminal IE of the power transmission device 3, can be adjusted according to the distance from the power transmission coil 32.

[0039] This will be explained in detail based on Figures 3 and 4. Figure 3 is a circuit diagram corresponding to the wireless power supply system 1. In Figure 3, "V" is the voltage of power supply 5, and "Z" is the voltage of power supply 5. s" is the impedance of power supply 5 (input impedance), "R0" is the parasitic resistance of the power supply coil 31, "L0" is the inductance of the power supply coil 31, "C0" is the capacitance of the capacitor 33, "I0" is the current flowing through the power supply 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 of the power supply coil 31 and the power transmission coil 32, "R2" is the parasitic resistance of the power receiving coil 41, "R L " is the load resistance of 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, "k 12 " represents the coupling coefficient between the transmission coil 32 and the receiving coil 41.

[0040] Figure 4 is an equivalent circuit diagram based on the circuit diagram shown in Figure 3. The equivalent circuit diagram shown in Figure 4 shows a state in which the power supply coil 31 and the power transmission coil 32 are in resonance, and the power transmission coil 32 and the power receiving coil 41 are in resonance. The mutual inductance L0 between the power supply coil 31 and the power transmission coil 32 is k 01 √(L0L1), the mutual inductance L2 between the transmitting coil 32 and the receiving coil 41 is k 12 The equation is √(L1L2). In Figure 4, "Z0" is the impedance of the circuit from the input terminal IE of the power transmission device 3 to the load 8 side, i.e., between the power supply 5 and the power supply coil 31 (load-side impedance). "Z1" is the impedance of the circuit from between the power supply coil 31 and the power transmission coil 32 to the load 8 side. "Z2" is the impedance of the circuit from between the power supply coil 31 and the power transmission coil 32 to the load 8 side. From the equivalent circuit shown in Figure 4, the following equations 1 to 3 are obtained.

[0041]

number

[0042]

number

[0043]

Number

[0044] And the impedance matching in the present invention means that when the load resistance R L changes, the load-side impedance Z0 of the circuit when viewed from the load 8 side at the input end IE of the power transmission device 3 is matched with the input-side impedance Z s of the power supply 5 and kept substantially constant.

[0045] Specifically, in the wireless power supply system 1, when the power of the load 8 is large and the impedance of the load 8 is small, as can be seen from Equation (1), the impedance Z2 of the circuit on the load 8 side between the power supply coil 31 and the power transmission coil 32 becomes small. Also at this time, as can be seen from Equation (2), the impedance Z1 of the circuit on the load 8 side between the power supply coil 31 and the power transmission coil 32 becomes large, and as can be seen from Equation (3), the load-side impedance Z0 becomes small. That is, while the load-side impedance Z0 becomes small, the input-side impedance Z s does not change.

[0046] Therefore, by switching control of the switches 91a to 91d, power is supplied to the power supply coil unit 31A closest to the power transmission coil 32, so that the magnetic field coupling with the power transmission coil 32 becomes dense, and the coupling coefficient k 01 becomes large. And by increasing the coupling coefficient k 01 of the power supply coil 31 and the power transmission coil 32 by the same ratio as the ratio at which the impedance Z1 of the circuit on the load 8 side between the power supply coil 31 and the power transmission coil 32 has increased, the load-side impedance Z0 can be kept constant. In this way, by continuously controlling the load-side impedance Z0 to an impedance substantially equal to the input-side impedance Z s , power reflection can be suppressed, and an efficient system driving situation can be realized.

[0047] Furthermore, when the power of load 8 is small and the impedance of load 8 is large, as can be seen from equation (1), the impedance Z2 of the circuit on the load 8 side between the power supply coil 31 and the power transmission coil 32 becomes large. Also, as can be seen from equation (2), the impedance Z1 of the circuit on the load 8 side between the power supply coil 31 and the power transmission coil 32 becomes small, and as can be seen from equation (3), the load side impedance Z0 becomes large. In other words, the load side impedance Z0 becomes large, while the input side impedance Z s It does not change.

[0048] Therefore, by switching the switches 91a to 91d to control the power supply of either the power supply coil section 31B or 31C, the magnetic field coupling with the power transmission coil 32 becomes looser depending on the distance between the power transmission coil 32 and the power supply coil sections 31B and 31C, and the coupling coefficient k 01 The coupling coefficient k between the power supply coil 31 and the power transmission coil 32 decreases by the same rate as the decrease in the impedance Z1 of the circuit on the load 8 side between the power supply coil 31 and the power transmission coil 32. 01 By reducing this, the load side impedance Z0 can be kept constant. In this way, the load side impedance Z0 can be kept constant. s By continuously controlling the impedance to be approximately equal to this value, power reflection is suppressed, and an efficient system drive condition can be achieved.

[0049] The memory unit 93 stores a function showing the relationship between the load voltage and load current output from the DC-DC converter 7 and supplied to the load 8, and a function showing the relationship between the load current and the load-side impedance. The load voltage and load current supplied to the load 8 are measured in real time and continuously by a measurement unit 95 provided between the DC-DC converter 7 and the load 8. The measurement unit 95 is not limited to measuring the load voltage, but may also measure the load current, or both. In this embodiment, the load voltage and load current are the output voltage and output current from the DC-DC converter 7, or in other words, the input voltage and input current of the load 8. The measurement unit 95 can also be placed between the capacitor 62 and the DC-DC converter 7. In this case, the load voltage and load current are the input voltage and input current of the DC-DC converter 7. Furthermore, if the DC-DC converter 7 is not provided, the load voltage and load current are the input voltage and input current of the load 8.

[0050] Specifically, as shown in Figure 5, the function showing the relationship between load voltage and load current includes a function showing the relationship between load voltage and load current in an idling state (converter OFF) where the input voltage to the DC-DC converter 7 (e.g., 15V) is less than or equal to the operating power of the DC-DC converter 7 (e.g., 12V) and the DC-DC converter 7 is not operating, and a function showing the relationship between load voltage and load current in a state where the input voltage to the DC-DC converter 7 exceeds the operating power of the DC-DC converter 7 and the DC-DC converter 7 is operating (converter ON).

[0051] Furthermore, as shown in Figure 6, the function showing the relationship between the load current and the load side impedance includes a function showing the relationship between the load current and the load side impedance when the DC-DC converter 7 is idling (converter OFF) and a function showing the relationship between the load current and the load side impedance when the DC-DC converter 7 is not operating (converter ON).

[0052] Furthermore, the functions showing the relationship between load voltage and load current, and the functions showing the relationship between load current and load-side impedance, may be calculated in advance through experiments or other means, and are not limited to the linear function graphs exemplified in Figures 5 and 6.

[0053] The control unit 94 controls the switching of switches 91a to 91d based on the measured values ​​from the measuring unit 95 and various functions stored in the storage unit 93. Details of the control unit 94's control of the switching of switches 91a to 91d will be described later.

[0054] In this way, the wireless power supply system 1 according to this embodiment can instantly change the positional relationship between the power supply coil 31 and the power transmission coil 32 by the impedance matching mechanism 9 in response to fluctuations in the load-side impedance measured by the measurement unit 95, thereby mitigating the difference between the input-side impedance and the load-side impedance at the input terminal IE in real time.

[0055] <Impedance matching process> Next, the impedance matching process performed by the impedance matching mechanism 9 will be explained based on the diagram.

[0056] First, we will explain why the load-side impedance fluctuates depending on whether the DC-DC converter 7 is turned on or off. In this embodiment, we will explain using the case where the load-side impedance fluctuates depending on whether the DC-DC converter 7 is turned on or off as an example. However, fluctuations in the load-side impedance can occur not only due to the on / off status of the DC-DC converter 7, but also due to changes in the relative position between the transmitting coil 32 and the receiving coil 41, changes in the driving conditions (output) of the load 8, etc. It goes without saying that this can be used to suppress fluctuations in the load-side impedance caused by these various factors.

[0057] As shown in Figure 5, when the DC-DC converter 7 is idling (converter OFF), the output voltage of the DC-DC converter 7 is, for example, 12V or less, which is the operating power, and the load current is also very small. When the measurement unit 95 is placed between the DC-DC converter 7 and the load 8, the load current (output current of the DC-DC converter 7) is almost zero, and when the measurement unit 95 is placed between the capacitor 62 and the DC-DC converter 7, the load current (input current of the DC-DC converter 7) increases slightly until it reaches the operating voltage (for example, 12V). At this time, the load side impedance becomes extremely large, as shown in Figure 6. Also, when the measurement unit 95 is placed between the DC-DC converter 7 and the load 8, the load side impedance is almost constant (a value equivalent to the power of the load intended for the device), and when the measurement unit 95 is placed between the capacitor 62 and the DC-DC converter 7, the load side impedance decreases slightly.

[0058] Next, as shown in Figure 5, when the DC-DC converter 7 starts operating (converter ON) and power is supplied to the load 8, the output voltage of the DC-DC converter 7 (load voltage) increases to, for example, 12V, and the output current of the DC-DC converter 7 (load current) increases sharply. At this time, the load-side impedance decreases sharply, as shown in Figure 6, and asymptotically approaches a predetermined value over time. In order to reliably suppress fluctuations in the load-side impedance from the moment power supply to the load 8 starts, the value of the load-side impedance is adjusted in advance during the idling state before the DC-DC converter 7 starts operating.

[0059] In this way, the load impedance fluctuates according to the operating state of the DC-DC converter 7, while the input impedance is fixed at a predetermined value (e.g., 50Ω). As a result, the input impedance and the load impedance do not match, which can lead to reflected waves at the input terminal IE, reducing transmission efficiency, or causing system failure due to insufficient transmitted power.

[0060] Therefore, the controller 92 increases or decreases the impedance of the circuit within the power transmission device 3 in accordance with the fluctuation of the load-side impedance.

[0061] Specifically, first, the control unit 94 calculates the load current based on the load voltage measured by the measurement unit 95 and the function shown in Figure 5. Then, the control unit 94 calculates the load-side impedance based on the calculated load current and the function shown in Figure 6.

[0062] Next, the control unit 94 switches switches 91a to 91d to determine which of the power supply coils 31A, 31B, or 31C to supply power to, so that the load side impedance matches the input side impedance, and adjusts the impedance of the circuit in the power transmission device 3.

[0063] For example, when the DC-DC converter 7 is idling and the load side impedance is large compared to the input side impedance, supplying power to the power supply coil section 31A, as shown in Figure 7(a), tightens the magnetic field coupling between the power supply coil 31 and the power transmission coil 32, increasing the coupling coefficient. As a result, as mentioned above, the load side impedance at the input terminal IE decreases, and the difference with the input side impedance is mitigated.

[0064] On the other hand, when the DC-DC converter 7 is operating and the load-side impedance is lower than the input-side impedance, as shown in Figure 7(b), supplying power to the power supply coil section 31B, which is further from the power transmission coil 32 than the power supply coil section 31A, loosens the magnetic field coupling between the power supply coil 31 and the power transmission coil 32, and reduces the coupling coefficient. As a result, the load-side impedance at the input terminal IE increases, and the difference with the input-side impedance is mitigated.

[0065] Furthermore, as the load-side impedance decreases further, as shown in Figure 7(c), supplying power to the power supply coil section 31C, which is furthest from the power transmission coil 32, further loosens the magnetic field coupling between the power supply coil 31 and the power transmission coil 32, and the coupling coefficient decreases. As a result, the load-side impedance at the input terminal IE becomes even larger, and the difference with the input-side impedance is mitigated.

[0066] The function between the distance between the power supply coils 31A, 31B, and 31C and the power transmission coil 32, and the change in the coupling coefficient, is determined using a formula obtained in advance through experiments or other means.

[0067] In this way, the wireless power supply system 1 according to this embodiment is a wireless power supply system 1 that transmits and receives power using magnetism, and comprises a power transmission device 3 equipped with a power transmission side resonant circuit 36 ​​including a power transmission coil 32, a power receiving device 4 equipped with a power receiving side resonant circuit 43 including a power receiving coil 41, a load 8 to which power received via the power receiving coil 41 is supplied, a measuring unit 95 for measuring the load current or load voltage at the load 8, and an impedance matching mechanism 9 that performs impedance matching processing to mitigate the difference between the load side impedance, which is the impedance of the circuit from the input terminal IE of the power transmission 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 transmission device 3 to the AC power supply 5 side, according to the measurement results of the measuring unit 95.

[0068] With this configuration, if the load-side impedance and the input-side impedance do not match, the impedance matching mechanism 9 will mitigate the difference between the input-side impedance and the load-side impedance according to the measurement results of the measurement unit 95. This suppresses the generation of reflected waves at the input terminal IE, thereby avoiding a decrease in transmission efficiency and system failures caused by a reduction in transmitted power.

[0069] Furthermore, in the wireless power supply system 1 according to this embodiment, the power transmission device 3 is provided so as to be magnetically coupled with the power transmission coil 32 and further comprises a power supply coil 31 that transmits power to the power transmission coil 32, and the impedance matching mechanism 9 is configured to change the coupling strength in the magnetic field coupling between the power transmission coil 32 and the power supply coil 31.

[0070] This configuration allows the impedance of the circuit within the power transmission device 3 to increase or decrease by changing the strength of the magnetic field coupling between the power supply coil 31 and the power transmission coil 32 (the tightness or looseness of the magnetic field coupling). This reduces the difference between the input impedance and the load impedance, thereby suppressing the generation of reflected waves at the input terminal IE and preventing system failures caused by a decrease in power transmission efficiency or reduced power transmission.

[0071] Furthermore, in the wireless power supply system 1 according to this embodiment, the power supply coil 31 is divided into a plurality of power supply coil sections 31A, 31B, and 31C, each having a different magnetic field coupling strength with respect to the power transmission coil 32, and is configured to supply power to at least one of the plurality of power supply coil sections 31A, 31B, and 31C. The impedance matching mechanism 9 is configured to supply power to at least one of the plurality of power supply coil sections 31A, 31B, and 31C according to the measurement result of the measurement unit 95.

[0072] With this configuration, by supplying power to one of the power supply coil sections 31A, 31B, or 31C, which have different magnetic field coupling strengths with the power transmission coil 32, according to the measurement results of the measurement section 95, the impedance of the circuit within the power transmission device 3 increases or decreases, and the difference between the input side impedance and the load side impedance is mitigated. As a result, the generation of reflected waves at the input terminal IE is suppressed, and a decrease in power transmission efficiency and system failures caused by a decrease in transmitted power can be avoided.

[0073] Furthermore, the wireless power supply system 1 according to this embodiment is configured such that each of the multiple power supply coil sections 31A, 31B, and 31C has a coil shaft 31a, 31b, and 31c arranged substantially coaxially with the others, and the distances from the power transmission coil 32 are set to be different for each section.

[0074] With this configuration, the coupling strength of the magnetic field between the power supply coils 31A, 31B, and 31C and the power transmission coil 32 weakens inversely proportional to the distance of the power supply coils 31A, 31B, and 31C from the power transmission coil 32. Therefore, by supplying power to any of the power supply coils 31A, 31B, and 31C, which have different magnetic field coupling strengths with the power transmission coil 32, the impedance of the circuit within the power transmission device 3 can be increased or decreased.

[0075] Furthermore, in the wireless power supply system 1 according to this embodiment, power is supplied from the power supply coil 31 to the power transmission coil 32 by a magnetic field resonance method, and the inductance values ​​of the power supply coils 31A, 31B, and 31C are set to be approximately equal.

[0076] This configuration allows for efficient power supply to the power transmission coil 32 from power supply coil sections 31A, 31B, and 31C, which are located at different relative positions to the power transmission coil 32, using a magnetic field resonance method.

[0077] Furthermore, in this embodiment, the wireless power supply system 1 is configured to supply power from the transmitting coil 32 to the receiving coil 41 using a magnetic field resonance method.

[0078] This configuration allows for efficient power supply from the transmitting coil 32 to the receiving coil 41.

[0079] Furthermore, the wireless power supply method using the wireless power supply system 1 according to this embodiment comprises a power transmission device 3 equipped with a power transmission side resonant circuit 36 ​​including a power transmission coil 32, a power receiving device 4 equipped with a power receiving side resonant circuit 43 including a power receiving coil 41, a load 8 to which power received via the power receiving coil 41 is supplied, and a measurement unit 95 for measuring the load current or load voltage at the load 8, and is configured to use an impedance matching mechanism 9 to mitigate the difference between the load side impedance, which is the impedance of the circuit from the input terminal IE of the power transmission 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 transmission device 3 to the AC power supply 5 side, according to the measurement result of the measurement unit 95.

[0080] With this configuration, if the load-side impedance and the input-side impedance do not match, the impedance matching mechanism 9 mitigates 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 preventing system failures caused by a decrease in power transmission efficiency and a reduction in transmitted power.

[0081] Furthermore, the wireless power supply system 1 according to this embodiment is a wireless power supply system 1 that transmits and receives power using magnetism, comprising: a power transmission device 3 equipped with a power transmission side resonant circuit 36 ​​including a power transmission coil 32; a power receiving device 4 equipped with a power receiving side resonant circuit 43 including a power receiving coil 41; a load 8 to which power received via the power receiving coil 41 is supplied; and an impedance matching process that reduces the difference between the load side impedance, which is the impedance of the circuit on the load 8 side from the input terminal IE of the power transmission device 3, and the input side impedance, which is the impedance of the circuit on the AC power supply 5 side from the input terminal IE of the power transmission device 3. The power transmission device 3 is equipped with an impedance matching mechanism 9 and a power supply coil 31 which is provided so as to be magnetically coupled with the power transmission coil 32 and transmits power to the power transmission coil 32. The power supply coil 31 is divided into a plurality of power supply coil sections 31A, 31B, and 31C which are in different relative positions to the power transmission coil 32, and is configured to be able to supply power to at least one of the plurality of power supply coil sections 31A, 31B, and 31C. The impedance matching mechanism 9 is configured to adjust the coupling strength in the magnetic field coupling between the power transmission coil 32 and the power supply coil 31 by supplying power to at least one of the plurality of power supply coil sections 31A, 31B, and 31C.

[0082] With this configuration, if the load-side impedance and the input-side impedance do not match, the difference between the input-side impedance and the load-side impedance is mitigated according to the measurement results of the measurement unit 95. This suppresses the generation of reflected waves at the input terminal IE, thereby avoiding a decrease in transmission efficiency and system failures caused by a reduction in transmitted power.

[0083] Furthermore, the wireless power transmission system 11 according to this embodiment is a wireless power transmission system 11 that transmits power to a power receiving device 4 using magnetism, and comprises a power transmission device 3 that includes a power transmission side resonant circuit 36 ​​including a power transmission coil 32 and transmits power to a load 8 via a power receiving device 4, and an impedance matching mechanism 9 that performs impedance matching processing to mitigate the difference between the load side impedance, which is the impedance of the circuit on the load 8 side from the input terminal IE of the power transmission device 3, and the input side impedance, which is the impedance of the circuit on the AC power supply 5 side from the input terminal IE of the power transmission device 3, according to the load current or load voltage at the load 8.

[0084] With this configuration, if the load-side impedance and the input-side impedance do not match, the impedance matching mechanism 9 will mitigate the difference between the input-side impedance and the load-side impedance according to the measurement results of the measurement unit 95. This suppresses the generation of reflected waves at the input terminal IE, thereby avoiding a decrease in transmission efficiency and system failures caused by a reduction in transmitted power.

[0085] Furthermore, in the above-described embodiment, the fluctuation of the load current associated with the on / off switching of the DC-DC converter 7 was explained as an example of a factor causing fluctuations in the load-side impedance, but the factors causing fluctuations in the load-side impedance are not limited to this.

[0086] For example, the load-side impedance may fluctuate as the power-supplied object 2 moves. This is because, as the receiving coil 41 approaches the transmitting coil 32, the coupling strength of the magnetic coupling between the transmitting coil 32 and the receiving coil 41 increases, and as the receiving coil 41 moves away from the transmitting coil 32, the coupling strength of the magnetic coupling between the transmitting coil 32 and the receiving coil 41 decreases, causing a change in the magnetic coupling state between the transmitting coil 32 and the receiving coil 41. Therefore, in such cases, the distance between the transmitting coil 32 and the receiving coil 41 may be monitored, and a decision may be made on which of the power-supplying coils 31A, 31B, or 31C to supply power so that the input-side impedance and the load-side impedance match according to the change in the distance between the transmitting coil 32 and the receiving coil 41.

[0087] Furthermore, in this embodiment, a configuration in which the input impedance and load impedance are pre-matched when the DC-DC converter 7 is idling is illustrated. However, for example, the configuration may be such that the input impedance and load impedance are 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 has been turned ON.

[0088] <Example of experiment> Next, we will describe the simulation performed to confirm the effectiveness and feasibility of the wireless power supply system 1 according to this embodiment. In this simulation, the diameters of the power supply coil 31 and the power transmission coil 32 were set to 700 mm each, and it was assumed that the power supply coil 31 and the power transmission coil 32 maintained a resonant state, and the power transmission coil 32 and the power receiving coil 41 also maintained a resonant state. When the load resistance RL of the load 8 was changed, the axial distance L between the centers of the coil axes 31a (31b, 31c) of the power supply coil 31 and the power transmission coil 32 at which the impedance was matched was calculated. The value of the load resistance RL included the load resistance values ​​of the rectifier circuit 6 and the DC-DC converter 7. In addition, the actual load resistance of the load 8, considering the load resistance of the rectifier circuit 6 and the DC-DC converter 7 when the output voltage of the DC-DC converter 7 was set to 48 V, was also calculated. These results are shown in Table 1 and Figure 8. Figure 8 is a graph in which the horizontal axis represents the load resistance RL and the vertical axis represents the distance L between the centers of the power supply coil 31 and the power transmission coil 32 when the impedances are matched. In Table 1 and Figure 8, when the load 8 is OFF, the load resistance RL is conveniently set to 1000Ω or more (actual load resistance of load 8 is 1000Ω or more), and the distance L between the centers in this case is set to 500mm.

[0089] [Table 1]

[0090] According to Figure 8, when the power supply coil section 31A is positioned 300 mm from the power transmission coil 32, the power supply coil section 31B is positioned 400 mm from the power transmission coil 32, and the power supply coil section 31C is positioned 500 mm from the power transmission coil 32, the load current is measured by the measurement unit 95 to calculate the value of the drive power of the load 8. The power supply coil sections 31A, 31B, and 31C are switched by switching switches 91a to 91d according to the calculated drive power of the load 8. Specifically, power supply coil section 31A is activated when the drive power of the load 8 is 200W or more, power supply coil section 31B is activated when the drive power of the load 8 is 20W or more but less than 200W, and power supply coil section 31C is activated when the load 8 is OFF or the drive power of the load 8 is less than 20W.

[0091] Furthermore, by increasing the number of power supply coils 31, more accurate impedance matching can be achieved. For example, the number of power supply coils 31 can be increased to six, and the installation positions of each power supply coil 31 can be set to 250mm, 300mm, 350mm, 400mm, 450mm, and 500mm from the center-to-center distance L of the power transmission coil 32. In this case, the power supply coil with a center-to-center distance L of 250 mm is activated when the drive power of load 8 is 700 W or more; the power supply coil with a center-to-center distance L of 300 mm is activated when the drive power of load 8 is 350 W or more but less than 700 W; the power supply coil with a center-to-center distance L of 350 mm is activated when the drive power of load 8 is 200 W or more but less than 350 W; the power supply coil with a center-to-center distance L of 400 mm is activated when the drive power of load 8 is 50 W or more but less than 200 W; the power supply coil with a center-to-center distance L of 450 mm is activated when the drive power of load 8 is 10 W or more but less than 50 W; and the power supply coil with a center-to-center distance L of 500 mm is activated when load 8 is OFF or when the drive power of load 8 is less than 10 W.

[0092] Furthermore, the multiple power supply coils 31 do not necessarily need to be placed at equal intervals, and the spacing between the power supply coils 31 can be changed as needed. For example, the number of power supply coils 31 installed in the region where the drive power is small and the drive power increases rapidly when the load 8 is started may be greater than the number of power supply coils 31 installed in the region where the drive power of the load 8 is large and relatively stable. Specifically, when six power supply coils 31 are provided, the installation positions of each power supply coil 31 are placed at distances L from the transmission coil 32 between their centers: 300 mm, 400 mm, 440 mm, 470 mm, 490 mm, and 500 mm. In this case, the power supply coil 31 positioned at a center-to-center distance L of 300 mm operates when the drive power of the load 8 is 500 W or more, the power supply coil 31 positioned at a center-to-center distance L of 400 mm operates when the drive power of the load 8 is 60 W or more but less than 500 W, the power supply coil 31 positioned at a center-to-center distance L of 440 mm operates when the drive power of the load 8 is 30 W or more but less than 60 W, the power supply coil 31 positioned at a center-to-center distance L of 470 mm operates when the drive power of the load 8 is 15 W or more but less than 30 W, the power supply coil 31 positioned at a center-to-center distance L of 490 mm operates when the drive power of the load 8 is 5 W or more but less than 15 W, and the power supply coil 31 positioned at a center-to-center distance L of 500 mm operates when the load 8 is OFF or the drive power of the load 8 is less than 5 W.

[0093] <Example 1> Next, a modified version of this embodiment will be described. Note that, apart from the configuration described below, the modified version is the same as that of the embodiment described above.

[0094] The impedance matching mechanism 9 may also include a coil movement mechanism 96 that moves the power supply coil 31 relative to the power transmission coil 32, as shown in Figures 9(a) and (b).

[0095] The coil movement mechanism 96 is a solenoid comprising a plunger 96a and a case 96b. A power supply coil 31 is connected to the tip of the plunger 96a. As the plunger 96a moves in and out perpendicular to the coil shafts 31a, 31b, and 31c, the power supply coil 31 is slid so that each coil shaft 31a, 31b, and 31c moves relative to or closer to (coincides with) the coil shaft 32a, while the coil shafts 31a, 31b, and 31c and the coil shaft 32a of the power transmission coil 32 are kept approximately parallel.

[0096] Specifically, as shown in Figures 2(a) to 2(c), if we consider the position of the power supply coil 31 when the coil axes 31a, 31b, and 31c are coaxial with the coil axis 32a of the power transmission coil 32 as the original position, then as shown in Figure 9(a), the plunger 96a retracts, causing the power supply coil 31 to move away from the original position in a direction perpendicular to the coil axes 31a, 31b, and 31c, and as shown in Figure 9(b), the plunger 96a advances, causing the power supply coil 31 to move away from the original position in a direction perpendicular to the coil axes 31a, 31b, and 31c.

[0097] Here, when the coil axes 31a, 31b, and 31c are located coaxially with the coil axis 32a of the transmission coil 32, the magnetic field coupling with the transmission 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 relative to the coil axis 32a of the transmission coil 32 in a direction perpendicular to the coil axis 31a, the magnetic field coupling with the transmission coil 32 becomes loose (the coupling strength (coupling coefficient) becomes small).

[0098] The function between the offset amount of the coil shaft 31a of the power supply coil 31 and the coil shaft 32a of the power transmission coil 32 (stroke amount of the plunger 96a) and the change in the impedance of the circuit in the power transmission device 3 is determined in advance through experiments or other means.

[0099] Furthermore, the stroke range (on one side) of the plunger 96a is set to be less than or equal to the radius of the power supply coil 31, for example. This ensures that even when the power supply coil 31 moves to its maximum extent in any direction perpendicular to the coil axes 31a, 31b, and 31c, at least a portion of the power supply coil 31 overlaps with at least a portion of the power transmission coil 32 when viewed from the axial direction of the coil axes 31a, 31b, and 31c.

[0100] The mechanism 96 used to move the power supply coil 31 relative to the power transmission coil 32 has inferior responsiveness compared to a configuration that electrically switches 91a to 91d. For example, the impedance can be roughly adjusted by controlling the switching of switches 91a to 91d, and then fine-tuned by moving the power supply coil 31 relative to the power transmission coil 32 to optimize the impedance smoothly. Alternatively, the impedance can be roughly adjusted by moving the power supply coil 31 relative to the power transmission coil 32, and then fine-tuned by controlling the switching of switches 91a to 91d to optimize the impedance.

[0101] <Modification 2> In the above-described modified example 1, the coil moving mechanism 96 is shown to move the power supply coil 31 so that the coil axis 31a of the power supply coil 31 is offset in a direction perpendicular to the coil axis 32a of the power transmission coil 32. However, the coil moving mechanism 96 may also be configured to move the power supply coil 31 parallel to the axial directions of the coil axes 31a, 31b, 31c and coil axis 32a.

[0102] For example, as shown in Figures 2(a) to 2(c), if the position of the power supply coil 31 when the coil axes 31a, 31b, and 31c are coaxial with the coil axis 32a of the power transmission coil 32 is considered the original position, then, as shown in Figure 10(a), the plunger 96a retracts, moving the power supply coil 31 from its original position in a direction parallel to the coil axes 31a, 31b, and 31c and away from the power transmission coil 32, and as shown in Figure 10(b), the plunger 96a advances, moving the power supply coil 31 from its original position in a direction parallel to the coil axes 31a, 31b, and 31c and closer to the power transmission coil 32, a coil movement mechanism 96 configuration can be considered.

[0103] As mentioned above, the magnetic field coupling between the power supply coils 31A, 31B, and 31C and the power transmission coil 32 becomes tighter (the coupling coefficient increases) as they approach the power transmission coil 32, and the magnetic field coupling between the power supply coils 31A, 31B, and 31C and the power transmission coil 32 becomes looser (the coupling coefficient decreases) as they move away from the power transmission coil 32.

[0104] The function between the amount by which the coil movement mechanism 96 moves the power supply coil 31 (stroke amount of the plunger 96a) and the change in the impedance of the circuit in the power transmission device 3 is determined using a value obtained in advance through experiments or other means.

[0105] The mechanism that moves the power supply coil 31 relative to the power transmission coil 32 using such a coil movement mechanism 96 has inferior responsiveness compared to a configuration that electrically switches switches 91a to 91d. For example, by roughly adjusting the impedance by switching control of switches 91a to 91d, and then fine-tuning the impedance by moving the power supply coil 31 relative to the power transmission coil 32, optimization can be performed smoothly even when the impedance value changes significantly.

[0106] Specifically, first, the power supply coil section 31A is positioned at a center-to-center distance L of 300 mm from the power transmission coil 32, the power supply coil section 31B is positioned at a center-to-center distance L of 400 mm from the power transmission coil 32, and the power supply coil section 31C is positioned at a center-to-center distance L of 500 mm from the power transmission coil 32. The power supply coil sections 31A, 31B, and 31C are configured as a single unit, and the coil movement mechanism 96 is configured to allow the power supply coil sections 31A, 31B, and 31C to move within a range of ±50 mm parallel to the coil axes 31a, 31b, and 31c. That is, the power supply coil section 31A is movable within a center-to-center distance L of 250 to 350 mm, the power supply coil section 31B is movable within a center-to-center distance L of 350 to 450 mm, and the power supply coil section 31C is movable within a center-to-center distance L of 450 to 550 mm.

[0107] For example, when the driving power of load 8 is 300W or more but less than 1000W, the power supply coil section 31A is used; when the driving power of load 8 is 30W or more but less than 300W, the power supply coil section 31B is used; when load 8 is OFF or the driving power of load 8 is less than 50W, the power supply coil section 31C is used; and then the impedance is optimized by moving the power supply coil sections 31A, 31B, and 31C relative to the power transmission coil 32.

[0108] Alternatively, the impedance can be roughly adjusted by moving the power supply coil 31 relative to the power transmission coil 32 using the coil movement mechanism 96, and then fine-tuned by switching control of switches 91a to 91d to optimize the impedance. In this case, since the fine-tuning of the impedance can be done at high speed, optimization can be performed smoothly even in the event of a sudden change in impedance.

[0109] Specifically, the power supply coil 31, which is made up of power supply coil sections 31A, 31B, and 31C arranged 50 mm apart from each other, is treated as a single unit, and the coil moving mechanism 96 is configured to allow the power supply coil sections 31A, 31B, and 31C to move by 100 mm or 200 mm in a direction parallel to the coil axes 31a, 31b, and 31c and away from the power transmission coil 32.

[0110] For example, with the power supply coil section 31A positioned at a center-to-center distance L of 200 mm, the power supply coil section 31B positioned at a center-to-center distance L of 250 mm, and the power supply coil section 31C positioned at a center-to-center distance L of 300 mm, the impedance is optimized by using the power supply coil section 31B when the driving power of the load 8 is 700 W or more, and using the power supply coil section 31C when the driving power of the load 8 is 350 W or more but less than 700 W.

[0111] Furthermore, the coil moving mechanism 96 moves the power supply coils 31A, 31B, and 31C 100 mm away from the power transmission coil 32, so that power supply coil 31A is positioned at a center-to-center distance L of 300 mm, power supply coil 31B is positioned at a center-to-center distance L of 350 mm, and power supply coil 31C is positioned at a center-to-center distance L of 400 mm. In this state, impedance optimization is achieved by using power supply coil 31A when the drive power of the load 8 is 350 W or more and less than 700 W, power supply coil 31B when the drive power of the load 8 is 200 W or more and less than 350 W, and power supply coil 31C when the drive power of the load 8 is 50 W or more and less than 200 W.

[0112] Furthermore, the coil moving mechanism 96 moves the power supply coils 31A, 31B, and 31C 200 mm away from the power transmission coil 32, so that power supply coil 31A is positioned at a center-to-center distance L of 400 mm, power supply coil 31B is positioned at a center-to-center distance L of 450 mm, and power supply coil 31C is positioned at a center-to-center distance L of 500 mm. In this state, impedance optimization is achieved by using power supply coil 31A when the drive power of the load 8 is 50W or more but less than 200W, power supply coil 31B when the drive power of the load 8 is 10W or more but less than 50W, and power supply coil 31C when the load 8 is OFF or the drive power of the load 8 is less than 10W.

[0113] <Variation 3> In the embodiment described above, a power supply coil 31 consisting of power supply coil sections 31A, 31B, and 31C, in which coil shafts 31a, 31b, and 31c are arranged substantially coaxially, was illustrated as an example, but the configuration of the power supply coil 31 is not limited to this.

[0114] For example, the power supply coil 31 may have power supply coil sections 31A, 31B, and 31C arranged offset from each other so that the coil axes 31a, 31b, and 31c are substantially parallel and spaced apart from each other, as shown in Figures 11(a) to (c).

[0115] In this configuration, the magnetic field coupling between the power supply coil 31 and the power transmission coil 32 becomes tighter as the opposing area increases. Therefore, as shown in Figure 11(a), the power supply coil section 31A has the tightest magnetic field coupling with the power transmission coil 32 because the coil shafts 31a and 32a are located coaxially. Furthermore, as shown in Figure 11(b), the power supply coil section 31B has a looser magnetic field coupling with the power transmission coil 32 because the coil shaft 31b is farther away from the coil shaft 32a. And as shown in Figure 11(c), the power supply coil section 31C has the loosest magnetic field coupling with the power transmission coil 32 because the coil shaft 31c is furthest away from the coil shaft 32a. With this configuration, power can be selectively supplied to at least one of the power supply coil sections 31A, 31B, and 31C by switching control of switches 91a to 91d, thereby adjusting the coupling strength (coupling coefficient) between the power supply coil 31 and the power transmission coil 32.

[0116] <Modification 4> The power supply coil 31 may, for example, have eight power supply coil sections 31A to 31H arranged in a spherical shape, as shown in Figures 12(a) to (c).

[0117] The power supply coil 31 consists of power supply coil sections 31A to 31H that are inclined relative to each other while their centers coincide. The power supply coil sections 31A to 31H are formed by dividing a single coil into eight parts and are essentially connected in series. Details of the connection relationships between the power supply coil sections 31A to 31H are omitted, but as in Figure 2, power from the AC power source 5 is connected to at least one of the power supply coil sections 31A to 31H by switches or the like (not shown).

[0118] As shown in Figure 12(a), the power supply coil section 31A is housed within the power transmission coil 32 with its coil axis 31a and the coil axis 32a of the power transmission coil 32 substantially aligned, that is, without being tilted relative to the power transmission coil 32. Also, as shown in Figure 12(b), the power supply coil section 31C is housed within the power transmission coil 32 at an angle of approximately 45 degrees relative to the power transmission coil 32. Furthermore, as shown in Figure 12(c), the power supply coil section 31E is housed within the power transmission coil 32 at an angle of approximately 90 degrees relative to the power transmission coil 32. In addition, the power supply coil sections 31B, 31D, 31F-31H are housed within the power transmission coil 32 at angles of approximately 22.5 degrees, 67.5 degrees, 112.5 degrees, 135 degrees, and 157.5 degrees, respectively, relative to the power transmission coil 32.

[0119] In this case, the magnetic field coupling between the power supply coil 31 and the power transmission coil 32 becomes tighter as the opposing area increases. Specifically, in the power supply coil section 31A, the magnetic field coupling with the power transmission coil 32 is tightest because the coil axis 31a and the coil axis 32a are located coaxially. In the power supply coil section 31E, the magnetic field coupling with the power transmission coil 32 is loosest.

[0120] With this configuration, for example, impedance matching processing can be performed by appropriately switching between the three power supply coil sections 31A, 31C, and 31E. That is, when the DC-DC converter 7 is idling and the load side impedance is large compared to the input side impedance, supplying power to the power supply coil section 31A, as shown in Figure 12(a), tightens the magnetic field coupling between the power supply coil 31 and the power transmission coil 32, and reduces the impedance of the circuit in the power transmission device 3. As a result, the load side impedance at the input terminal IE becomes smaller, and the difference with the input side impedance is mitigated.

[0121] On the other hand, when the DC-DC converter 7 is operating and the load-side impedance is lower than the input-side impedance, as shown in Figure 12(b), supplying power to the power supply coil section 31C, which is inclined relative to the power transmission coil 32 compared to the power supply coil section 31A, loosens the magnetic field coupling between the power supply coil 31 and the power transmission coil 32, increasing the impedance of the circuit within the power transmission device 3. As a result, the load-side impedance at the input terminal IE increases, and the difference with the input-side impedance is mitigated.

[0122] Furthermore, as the load-side impedance decreases further, as shown in Figure 12(c), supplying power to the power supply coil section 31E, which is perpendicular to the power transmission coil 32, further loosens the magnetic field coupling between the power supply coil 31 and the power transmission coil 32. This increases the impedance of the circuit within the power transmission device 3, resulting in a larger negative impedance at the input terminal IE and mitigating the difference with the input-side impedance.

[0123] With this configuration, power is selectively supplied to at least one of the power supply coils 31A to 31H, making it possible to adjust the coupling strength between the power supply coil 31 and the power transmission coil 32.

[0124] Furthermore, the number of power supply coils constituting the spherical power supply coil 31 in this modified example is not limited to eight; any number of two or more is acceptable. Also, while the inclination of the power supply coils 31A to 31H relative to the power transmission coil 32 in this modified example is set in the range of 0 to 180 degrees, it may also be set in the range of -90 to +90 degrees, taking into account the phase of the coils.

[0125] Furthermore, the power supply coil 31 is not limited to being housed within the power transmission coil 32, but may be located outside the power transmission coil 32. Also, some of the power supply coil sections 31A to 31H may be located within the power transmission coil 32, while the remaining power supply coil sections 31A to 31H may be located outside the power transmission coil 32. Note that the inclination of the power supply coil 31 with respect to the power transmission coil 32 is determined by the coupling coefficient k. 01 By configuring the system to be switchable so that it follows a geometric progression, the impedance adjustment range at the angle of each power supply coil 31 becomes approximately constant, allowing for even more stable impedance matching.

[0126] <Modification 5> In the embodiment described above, a power supply coil 31 consisting of power supply coil sections 31A, 31B, and 31C formed in substantially the same shape was illustrated, but the power supply coil sections 31A, 31B, and 31C may have different shapes from each other.

[0127] For example, as shown in Figures 13(a) to (c), the power supply coil 31 may be configured in a spiral shape where the coil diameter expands and contracts on substantially the same plane. In this case, the coil axes 31a, 31b, and 31c are arranged substantially coaxially, and the power supply coil sections 31A, 31B, and 31C are formed such that the coil diameter gradually decreases in this order and the coil height increases. Specifically, the power supply coil section 31A is set to have substantially the same coil diameter as the power transmission coil 32, the power supply coil sections 31B and 31C are arranged on the inner circumference of the power supply coil section 31A, and the power supply coil section 31C is arranged on the inner circumference of the power supply coil section 31B. Furthermore, when power is transmitted between the power supply coil 31 and the power transmission coil 32 using a magnetic field resonance method, it is preferable to gradually increase the number of turns in the power supply coil sections 31A, 31B, and 31C in that order so that the inductances of the power supply coil sections 31A, 31B, and 31C, which have different coil diameters, are equal.

[0128] In this configuration, the magnetic field coupling between the power supply coil 31 and the power transmission coil 32 becomes tighter the smaller the difference in coil diameter. Therefore, as shown in Figure 13(a), the power supply coil section 31A has approximately the same coil diameter as the power transmission coil 32, resulting in the tightest magnetic field coupling with the power transmission coil 32. Furthermore, as shown in Figure 13(b), the power supply coil section 31B has a smaller coil diameter than the power transmission coil 32, resulting in looser magnetic field coupling with the power transmission coil 32. Additionally, as shown in Figure 13(c), the power supply coil section 31C has an even smaller coil diameter than the power transmission coil 32, resulting in the loosest magnetic field coupling with the power transmission coil 32. With this configuration, power can be selectively supplied to at least one of the power supply coil sections 31A, 31B, and 31C by switching control of switches 91a to 91d, thereby adjusting the coupling strength between the power supply coil 31 and the power transmission coil 32.

[0129] <Variation 6> For example, as shown in Figures 14(a) to (c), the power supply coil 31 may be configured such that the coil diameter gradually decreases from the outer circumference towards the center on the same plane. In this case, the coil axes 31a, 31b, and 31c are arranged substantially coaxially, and the power supply coil sections 31A, 31B, and 31C are arranged substantially on the same plane, and furthermore, the coil diameters of the power supply coil sections 31A, 31B, and 31C are set to gradually decrease in this order. Specifically, the power supply coil section 31A is set to have substantially the same coil diameter as the power transmission coil 32, the power supply coil sections 31B and 31C are arranged on the inner circumference of the power supply coil section 31A, and the power supply coil section 31C is arranged on the inner circumference of the power supply coil section 31B. Furthermore, when power is transmitted between the power supply coil 31 and the power transmission coil 32 using a magnetic field resonance method, it is preferable to gradually increase the number of turns in the power supply coil sections 31A, 31B, and 31C in that order so that the inductances of the power supply coil sections 31A, 31B, and 31C, which have different coil diameters, are equal.

[0130] In this configuration, the magnetic field coupling between the power supply coil 31 and the power transmission coil 32 becomes tighter the smaller the difference in coil diameter. Therefore, as shown in Figure 14(a), the power supply coil section 31A has approximately the same coil diameter as the power transmission coil 32, resulting in the tightest magnetic field coupling with the power transmission coil 32. Furthermore, as shown in Figure 14(b), the power supply coil section 31B has a smaller coil diameter than the power transmission coil 32, resulting in looser magnetic field coupling with the power transmission coil 32. Additionally, as shown in Figure 14(c), the power supply coil section 31C has an even smaller coil diameter than the power transmission coil 32, resulting in the loosest magnetic field coupling with the power transmission coil 32. With this configuration, power can be selectively supplied to at least one of the power supply coil sections 31A, 31B, and 31C by switching control of switches 91a to 91d, thereby allowing adjustment of the coupling strength (coupling coefficient) between the power supply coil 31 and the power transmission coil 32.

[0131] Furthermore, in the embodiments described above, the case in which the power supply coil 31, the power transmission coil 32, and the power receiving coil 41 are all in a resonant state was explained as an example in order to suppress the generation of reactive power by making the imaginary part of the impedance zero. However, even if the capacitor 33 is not connected to the power supply coil 31, for example, although reactive power is generated in the input impedance, power transmission itself is still possible, so it is also acceptable to set only the power transmission coil 32 and the power receiving coil 41 in a resonant state.

[0132] Furthermore, in the embodiments described above, the wireless power supply system 1 was explained using a three-coil system configuration comprising a power supply coil 31, a power transmission coil 32, and a power receiving coil 41 as an example. However, a two-coil wireless power supply system may also be used, which omits the power supply coil 31 and has only a power transmission coil 32 and a power receiving coil 41. In this case, the load-side impedance can be controlled by dividing the power transmission coil 32 into multiple power transmission coil sections and changing the relative position between each power transmission coil section and the power receiving coil 41.

[0133] In a two-coil system consisting of a transmitting coil 32 and a receiving coil 41, moving the position of the transmitting coil 32 to change the load-side impedance may cause the coil axis 32a of the transmitting coil 32 and the coil axis of the receiving coil 41 to be out of sync, potentially reducing the power transmission efficiency. In contrast, a three-coil system consisting of a supply coil 31, a transmitting coil 32, and a receiving coil 41 allows for the transmission of power to the transmitting coil 32 via the supply coil 31. By adjusting the coupling strength of the magnetic coupling between the supply coil 31 and the transmitting coil 32 without changing the relative positions of the transmitting coil 32 and the receiving coil 41, the load-side impedance can be controlled, thus maintaining good power transmission efficiency.

[0134] Furthermore, in the embodiments described above, the wireless power supply system 1 was explained using a three-coil system configuration comprising a power supply coil 31, a power transmission coil 32, and a power receiving coil 41 as an example. However, a wireless power supply system configuration employing a four-coil system with a second power receiving coil in addition to the power receiving coil 41 may also be used. In this case, the power receiving coil 41 is set to approximately the same resonant frequency as the power transmission coil 32, and power is transmitted by magnetic resonance. The power receiving coil 41 and the second power receiving coil are arranged non-contact, and power is transmitted by electromagnetic coupling (electromagnetic induction) or magnetic resonance. In addition, the four-coil system is easy to design because the resonant frequency does not change during operation, as the power transmission distance is extended, since the power transmission coil 32 and the power receiving coil 41 are coils for resonance independent of other electrical circuits.

[0135] Furthermore, the present invention can be modified in various ways other than those described above, as long as it does not deviate from the spirit of the invention, and it goes without saying that the present invention extends to such modified forms. [Explanation of symbols]

[0136] 1: Wireless power supply system 11: Wireless power transmission system 2: Objects to be powered 3: Power transmission equipment 31: Power supply coil 31A~31H: Power supply coil section 31a~31c: Coil shaft (of the power supply coil) 32: Power transmission coil 32a: Coil shaft (of a power transmission coil) 33, 34: Capacitors 35: Power supply side resonant circuit 36: Power transmission side resonant circuit 4: Power receiving device 41: Power receiving coil 42: Capacitor 43: Receiving side resonant circuit 5: AC power supply (power supply device) 6: Rectifier circuit 61: Diode 62: Capacitor 7: DC-DC converter 8: Load 9: Impedance matching mechanism 91a~91d: Switch 92: Controller 93: Storage section 94: Control Unit 95: Measuring part 96: Linear motion mechanism 96a: Plunger 96b: Case IE: Input terminal

Claims

1. A wireless power supply system that transmits and receives power using magnetism, A power transmission device comprising: a power transmission side resonant circuit including a power transmission coil; and a power supply coil provided so as to be magnetically coupled with the power transmission coil, which transmits power supplied from the input terminal to the power transmission coil by magnetic field resonance; A power receiving device comprising a power receiving side resonant circuit including a power receiving coil, which supplies the power received by the power receiving coil to a load, An impedance matching mechanism that performs impedance matching processing to mitigate the difference between the load-side impedance, which is the impedance of the circuit on the load side from the input terminal of the power transmission device, and the input-side impedance, which is the impedance of the circuit on the power supply side from the input terminal of the power transmission device. Equipped with, The power supply coil is substantially connected in series and divided into multiple power supply coil sections with different relative positions to the power transmission coil, and is configured to supply power to at least one of the multiple power supply coil sections. The impedance matching mechanism is characterized by adjusting the coupling strength in the magnetic field coupling between the power transmission coil and the power supply coil by supplying power to at least one of the plurality of power supply coil sections.

2. The wireless power supply system according to claim 1, characterized in that each of the multiple power supply coils has a coil shaft arranged substantially coaxially with the others, and the distance from the power transmission coil is set to be different for each of them.

3. The wireless power supply system according to claim 1, characterized in that the plurality of power supply coils are set in different orientations from each other and each has a coil axis at a different angle with respect to the coil axis of the power transmission coil.

4. The wireless power supply system according to claim 1, characterized in that each of the multiple power supply coils has a coil axis that is substantially parallel to the coil axis of the power transmission coil and offset from each other by different distances.

5. Each of the aforementioned power supply coil sections is equipped with a coil shaft arranged substantially coaxially, The wireless power supply system according to claim 1, characterized in that the coil diameter and coil height of each power supply coil section are set to be different.

6. The wireless power supply system according to claim 1, characterized in that the multiple power supply coil sections are arranged on substantially the same plane, and the coil diameter of each power supply coil section is set to be different.

7. The wireless power supply system according to any one of claims 1 to 6, characterized in that the inductance values ​​of each power supply coil section of the power supply coil are set to be approximately equal.

8. The wireless power supply system according to any one of claims 1 to 7, characterized in that the power supply from the transmitting coil to the receiving coil is performed by a magnetic field resonance method.

9. A power transmission device comprising: a power transmission side resonant circuit including a power transmission coil; and a power supply coil provided so as to be magnetically coupled with the power transmission coil, which transmits power supplied from the input terminal to the power transmission coil by magnetic field resonance; A power receiving device comprising a power receiving side resonant circuit including a power receiving coil, which supplies the power received by the power receiving coil to a load, An impedance matching mechanism that performs impedance matching processing to mitigate the difference between the load-side impedance, which is the impedance of the circuit on the load side from the input terminal of the power transmission device, and the input-side impedance, which is the impedance of the circuit on the power supply side from the input terminal of the power transmission device. A wireless power supply method using a wireless power supply system that is equipped with and transmits and receives power using magnetism, The power supply coil is substantially connected in series and divided into multiple power supply coil sections with different relative positions to the power transmission coil, and is configured to supply power to at least one of the multiple power supply coil sections. A wireless power supply method characterized by adjusting the coupling strength in the magnetic field coupling between the power transmission coil and the power supply coil by supplying power to at least one of the plurality of power supply coil sections using the impedance matching mechanism.

10. A wireless power transmission system that transmits power to a power receiving device using magnetism, A power transmission device comprising: a power transmission side resonant circuit including a power transmission coil; and a power supply coil provided so as to be magnetically coupled with the power transmission coil, which transmits power supplied from the input terminal to the power transmission coil by magnetic field resonance; An impedance matching mechanism that performs impedance matching processing to mitigate the difference between the load-side impedance, which is the impedance of the circuit on the load side from the input terminal of the power transmission device, and the input-side impedance, which is the impedance of the circuit on the power supply side from the input terminal of the power transmission device. Equipped with, The power supply coil is substantially connected in series and divided into multiple power supply coil sections with different relative positions to the power transmission coil, and is configured to supply power to at least one of the multiple power supply coil sections. The impedance matching mechanism is characterized by adjusting the coupling strength in the magnetic field coupling between the power transmission coil and the power supply coil by supplying power to at least one of the plurality of power supply coil sections.

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