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

Abstract

To provide a wireless power supply system, a method for wireless power supply, and a wireless power transmission system for reducing reduction of transmission efficiency even after the impedance of a load-side circuit is changed.SOLUTION: A wireless power supply system 1 includes a power transmission device 3, a power reception device 4, and a coil-moving mechanism 9. The power transmission device 3 performs impedance-matching processing to mitigate the difference between a load-side impedance, which is the impedance of a circuit on a load 8 side viewed from an input terminal IE of the power transmission device 3, and an input-side impedance, which is the impedance of a circuit on an AC power supply 5 side viewed from the input terminal of the power transmission device 3, by changing the coupling strength in magnetic coupling between a power supply coil 31 and a power transmission coil 32 in accordance with the operating state of a DC-DC converter 7, the power transmission device 3 including a transmission-side resonance circuit 36 including the power transmission coil 32 and being provided so as to be magnetically coupleable with the power transmission coil 32.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present 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 using magnetic resonance coupling (magnetic resonance) has been progressing. Magnetic resonance coupling refers to a state in which magnetic field oscillations generated by the flow of AC current through a resonant circuit of a power transmitting device are transmitted to the resonant circuit of a power receiving device and resonate, resulting in a strong coupling of the magnetic fields generated by the coils of each resonant circuit. Wireless power transfer using magnetic resonance coupling has the advantage of a longer power transfer distance compared to conventional wireless power transfer using electromagnetic induction (magnetic coupling) (see, for example, Patent Document 1).

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

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-505369 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the load-side circuit described above is connected to a driving member such as a battery or a motor, and the battery or the motor serves as a load. Therefore, the current flowing through the load-side circuit may fluctuate depending on the driving state of the battery or the motor. In a wireless power transfer system, the impedance of the load-side circuit fluctuates in response to fluctuations in the current flowing through the load-side circuit. This causes a mismatch between the impedance of the load-side circuit as seen from the power transmitting device and the impedance of the power source as seen from the power transmitting device, resulting in a significant decrease in power transmission efficiency and a decrease in transmitted power, which may result in a system failure.

[0006] Therefore, even if the impedance of the load side circuit fluctuates, a technical problem arises that must be solved in order to reduce the decrease in power transmission efficiency, and an object of the present invention is to solve this problem. [Means for solving the problem]

[0007] In order to achieve the above object, a wireless power feed system according to the present invention is a wireless power feed system that transmits and receives power using magnetism, and includes a power transmitting device including a power transmitting-side resonant circuit including a power transmitting coil, and a power feeding coil that is arranged to be magnetically coupled with the power transmitting coil and that feeds power supplied from an input end to the power transmitting coil by magnetic field resonance; a power receiving-side resonant circuit including a power receiving coil, and a voltage conversion circuit that converts an output voltage of power received by the power receiving coil to a predetermined voltage, and supplies the power converted by the voltage conversion circuit to a load; and an impedance matching mechanism that performs impedance matching processing to reduce the difference between a load-side impedance, which is the impedance of a circuit from the input end of the power transmitting device to the load side, and an input-side impedance, which is the impedance of a circuit from the input end of the power transmitting device to a power supply device side, by changing the coupling strength of the magnetic field coupling between the power feeding coil and the power transmitting coil according to the operating state of the voltage conversion circuit. [Effects of the Invention]

[0008] The present invention reduces the difference between the input impedance and the load impedance at the input terminal through impedance matching processing, thereby suppressing the generation of reflected waves at the input terminal and avoiding a decrease in power transmission efficiency and the resulting risk of system failure. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating a configuration of a wireless power supply system according to an embodiment of the present invention. [Figure 2] 10 is a schematic diagram illustrating a state in which the coil moving mechanism moves the power supply coil in a direction perpendicular to the coil axis. FIG. [Figure 3] 10A and 10B are schematic diagrams illustrating how a coil moving mechanism swings a power supply coil. [Figure 4] 1 is a graph showing the relationship between a load voltage and a load current. [Figure 5] 1 is a graph showing the relationship between a load current and a load-side impedance. DETAILED DESCRIPTION OF THE INVENTION

[0010] A wireless power supply system 1 according to one embodiment of the present invention will be described with reference to the drawings. Note that, hereinafter, when referring to the number, numerical value, amount, range, etc. of components, unless otherwise specified or when it is clearly limited to a specific number in principle, the number is not limited to that specific number and may be more or less than the specific number.

[0011] Furthermore, when referring to the shape or positional relationship of components, etc., it includes things that are substantially similar or approximate to those shapes, etc., unless otherwise specified or when it is clearly considered otherwise in principle.

[0012] In addition, the drawings may exaggerate characteristic parts to make the features easier to understand, and the dimensional proportions of the components may not be the same as in reality. In addition, in cross-sectional views, hatching of some components may be omitted to make the cross-sectional structure of the components easier to understand.

[0013] <Wireless power supply system configuration> 1 is a schematic diagram showing the configuration of a wireless power supply system 1. The wireless power supply system 1 supplies power to a power supply target 2 in a contactless manner by utilizing magnetic field resonant coupling (magnetic field resonance). The power supply target 2 is, for example, a vehicle, a robotic air vehicle, an underwater robot, a capsule endoscope, a cardiac pacemaker, etc. The wireless power supply system 1 includes a power transmitting device 3 and a power receiving device 4.

[0014] <Configuration of power transmission device> The power transmitting device 3 includes a power feeding coil 31, a power transmitting coil 32, and capacitors 33 and .

[0015] The power supply coil 31 and the power transmission coil 32 are formed by circularly winding a copper wire or the like with high electrical conductivity. Note that the current flowing through the copper wire flows more near the surface than in the center due to the influence of internal resistance. Therefore, when a litz wire made of multiple twisted copper wires 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 than that of a single copper wire of the same diameter, allowing for a larger current to flow and reducing current loss.

[0016] The power feeding coil 31 is supplied with AC power from an AC power source 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 source 5 can be changed as desired. Hereinafter, the contact point of the power feeding coil 31 on the AC power source 5 side will be referred to as the "input end IE." Note that in this embodiment, the power feeding coil 31 and the AC power source 5 are described as being directly connected to each other via the input end IE. However, the power feeding coil 31 and the AC power source 5 may be directly connected to each other via the input end IE or indirectly connected to each other via a coaxial cable or the like provided between the AC power source 5 and the input end IE. In this case, if the impedance of the power source matches the impedance of the coaxial cable or the like, the power source end of the coaxial cable or the like does not cause power reflection or the like and therefore does not pose a problem. Therefore, the input end IE refers to the load end of the coaxial cable or the like.

[0017] The power feeding coil 31 and the capacitor 33 are connected in series to form a power feeding side resonant circuit 35. When an AC voltage having a frequency corresponding to a resonant frequency set by the inductance of the power feeding coil 31 and the capacitance of the capacitor 33 flows through the power feeding coil 31, an oscillating magnetic field is generated that penetrates the power feeding coil 31.

[0018] In a normal state, the coil axis 32a of the power feeding coil 32 is disposed substantially parallel to the coil axis 31a of the power feeding coil 31. The power feeding coil 31 and the power feeding coil 32 are magnetically coupled, and when an AC current flows through the power feeding coil 31, an electromotive force is also generated in the power feeding coil 32 via a magnetic flux that is generated so as to penetrate the power feeding coil 31 in the coil axis direction.

[0019] The power transmitting coil 32 and the capacitor 34 are connected in series to form a power transmitting-side resonant circuit 36. When an AC voltage having a frequency corresponding to a resonant frequency set by the inductance of the power transmitting coil 32 and the capacitance of the capacitor 33 flows through the power transmitting coil 32, an oscillating magnetic field is generated that penetrates the power transmitting coil 32 in the coil axial direction. This oscillating magnetic field generated in the power transmitting coil 32 reaches at least a part of the power receiving device 4.

[0020] <Configuration of power receiving device> The power receiving device 4 is provided inside the power supply target 2. The power receiving device 4 includes a power receiving coil 41 and a capacitor .

[0021] The power receiving coil 41 is provided at a distance from the power transmitting coil 32 in the coil axial direction. The power receiving coil 41 is formed by circularly winding a copper wire or the like having high electrical conductivity. As with the power feeding coil 31 and the power transmitting coil 32, the power receiving coil 41 also preferably uses a Litz wire as the wire material.

[0022] The power receiving coil 41 and capacitor 42 are connected in series to form a power receiving-side resonant circuit 43. The resonant frequency, which is set by the inductance of the power receiving coil 41 and the capacitance of the capacitor 42, is set to match the resonant frequency of the power transmitting coil 32 and capacitor 33. As a result, an induced current flows in the power receiving coil 41 due to oscillations of the magnetic field that are generated so as to penetrate the power transmitting coil 32 in the coil axial direction, and an oscillating magnetic field is generated so as to penetrate the power receiving coil 41 in the coil axial direction. At this time, the magnetic fields of the power transmitting coil 32 and the power receiving coil 41 resonate and are strongly coupled together.

[0023] The AC power received by the power receiving coil 41 through resonance is supplied to the load 8 via the rectifier circuit 6 and the DC-DC converter 7. The load 8 is a motor, a battery, or the like that constitutes the power supply target 2.

[0024] The rectifier circuit 6 has four diodes 61 arranged on a bridge, performs full-wave rectification on the AC power received by the power receiving coil 41, and outputs a DC voltage. Reference numeral 62 denotes a capacitor that smoothes the DC voltage output by the rectifier circuit 6.

[0025] The DC-DC converter 7 converts the rectified DC voltage into a preset constant voltage (for example, 12 V). The voltage output from the DC-DC converter 7 is applied to the load 8.

[0026] <Configuration of impedance matching mechanism> Next, an impedance matching mechanism will be described with reference to the drawings, which performs impedance matching processing to reduce the difference between the impedance of the circuit (load side circuit) from the input terminal IE to the power receiving device 4 side, i.e., the impedance of the circuit including the power transmitting device 3, the power receiving device 4, the rectifier circuit 6, the DC-DC converter 7, and the load 8 (hereinafter referred to as the "load side impedance"), and the impedance of the circuit from the input terminal IE to the AC power source 5 side (hereinafter referred to as the "input side impedance").

[0027] 1, the impedance matching mechanism is a coil moving mechanism 9 that moves the power feeding coil 31 relative to the power transmitting coil 32. The coil moving mechanism 9 includes a linear motion mechanism 91 and a swinging mechanism 92.

[0028] The linear motion mechanism 91 is a solenoid including a plunger 91a and a case 91b. The tip of the plunger 91a is connected to the power supply coil 31. When the plunger 91a moves forward and backward in a direction perpendicular to the coil axis 31a of the power supply coil 31, the coil axis 31a of the power supply coil 31 and the coil axis 32a of the power transmission coil 32 move apart or approach (align) each other while maintaining the coil axes 31a and 32a in a substantially parallel state.

[0029] Specifically, as shown in Fig. 2(a), the position of the power feed coil 31 when the coil axis 31a of the power feed coil 31 is coaxial with the coil axis 32a of the power transmission coil 32 is taken as the original position. As shown in Fig. 2(b), the plunger 91a advances, and the power feed coil 31 moves away from the original position in a direction perpendicular to the coil axis 31a. As shown in Fig. 2(c), the plunger 91a retreats, and the power feed coil 31 moves away from the original position in a direction perpendicular to the coil axis 31a. In this way, the linear motion mechanism 91 slides the power feed coil 31 so that the coil axis 31a of the power feed coil 31 moves parallel to the coil axis 32a of the power transmission coil 32.

[0030] The stroke range (one side) of the plunger 91a is set to, for example, equal to or less than the radius of the power supply coil 31. This allows at least a portion of the power supply coil 31 to remain overlapped with at least a portion of the power transmission coil 32 when viewed from the coil axis 31a of the power supply coil 31, even when the power supply coil 31 moves to its maximum extent in either direction perpendicular to the coil axis 31a.

[0031] As shown in FIG. 3, the swing mechanism 92 supports the case 91b and swings the case 91b around a rotation axis 92a.

[0032] As shown in Fig. 3(a), the position of the plunger 91a when perpendicular to the coil axis 31a of the power feed coil 31 is defined as the original position. As shown in Fig. 3(b), the swing mechanism 92 tilts the power feed coil 31 located at the original position to move it away from the power transmission coil 32, or as shown in Fig. 3(c), the swing mechanism 92 tilts the power feed coil 31 located at the original position to move it closer to the power transmission coil 32. In this way, the swing mechanism 92 tilts the coil axis 31a of the power feed coil 31 relative to the coil axis 32a of the power transmission coil 32, thereby moving the power feed coil 31 toward or away from the power transmission coil 32. Note that if the power feed coil 31 is tilted around its center point, the power feed coil 31 does not move toward or away from the power transmission coil 32, and control can be achieved by tilting only the power feed coil 31.

[0033] In the wireless power feeding system 1, when the coil axis 31a of the feeding coil 31 and the coil axis 32a of the transmitting coil 32 are coaxially positioned, magnetic induction coupling becomes tighter, and the electromotive force generated in the transmitting coil 32 by the current flowing through the feeding coil 31 increases. In other words, the impedance of the feeding coil 31 and the transmitting coil 32 decreases, and the impedance seen from the input terminal IE is directly affected by the impedance downstream of the receiving coil 41 (on the load 8 side).

[0034] On the other hand, when the coil axis 31a of the power feeding coil 31 is offset from the coil axis 32a of the power transmitting coil 32 in a direction perpendicular to the coil axis 31a, the magnetic inductive coupling becomes weaker, and the electromotive force generated in the power transmitting coil 32 by the current flowing through the power feeding coil 31 becomes smaller. In other words, the impedance of the power feeding coil 31 and the power transmitting coil 32 becomes larger, and the impedance seen from the input terminal IE becomes less susceptible to the influence of the impedance downstream of the power receiving coil 41 (on the load 8 side).

[0035] In this way, in the wireless power supply system 1, the impedance matching mechanism controls the impedance at the power supply coil 31 and the power transmission coil 32, thereby controlling the influence of the impedance downstream of the power receiving coil 41 (toward the load 8), and a system can be realized in which the impedance seen from the input terminal IE is less susceptible to impedance changes due to the operating conditions of the load 8.

[0036] Specifically, in the wireless power transfer system 1, when the power of the load 8 is high and the impedance of the load 8 is small, the load-side impedance as seen from the input end IE of the power transfer coil 31 also decreases, while the input-side impedance does not fluctuate. Therefore, to make the load-side impedance equal to or closer to the input-side impedance, it is necessary to increase the load-side impedance. In this case, the coil movement mechanism 9 of the impedance matching mechanism moves the power transfer coil 31 in a direction perpendicular to the coil axis 31a while keeping the coil axis 31a of the power transfer coil 31 and the coil axis 32a of the power transmission coil 32 substantially parallel to each other. This increases the impedance at the power transfer coil 31 and the power transmission coil 32, thereby increasing the load-side impedance. In this case, by controlling the load-side impedance to be substantially equal to the input-side impedance, power reflection is suppressed, enabling efficient system operation.

[0037] On the other hand, in the wireless power transfer system 1, when the power of the load 8 is low and the impedance of the load 8 is high, the load-side impedance as seen from the input end IE of the power transfer coil 31 also increases, while the input-side impedance does not fluctuate. Therefore, to make the load-side impedance equal to or closer to the input-side impedance, it is necessary to reduce the load-side impedance. In this case, the coil movement mechanism 9 of the impedance matching mechanism moves the power transfer coil 31 so that the coil axis 31a of the power transfer coil 31 and the coil axis 32a of the power transmission coil 32 are coaxially positioned. This reduces the impedance at the power transfer coil 31 and the power transmission coil 32, thereby reducing the load-side impedance. In this case, by controlling the load-side impedance to be approximately equal to the input-side impedance, power reflection is suppressed, and an efficient system operating state can be achieved.

[0038] Note that, assuming that the rotation angle of the plunger 91a when the power supply coil 31 swings away from the power transmission coil 32 as shown in FIG. 3(b) is negative (-), and that the rotation angle of the plunger 91a when the power supply coil 31 swings toward the power transmission coil 32 as shown in FIG. 3(c) is positive (+), the rotation range of the swing mechanism 92 is preferably set to, for example, ±30 degrees around the original position of the plunger 91a.

[0039] Returning to Fig. 1, the operation of the coil moving mechanism 9 is controlled by a controller 93. The controller 93 is configured with, for example, a CPU, a memory, etc. The functions of the controller 93 may be realized by control using software, or may be realized by operation using hardware. The controller 93 is functionally divided into a storage unit 94 and a control unit 95.

[0040] The memory unit 94 stores a function indicating 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 indicating the relationship between the load current and load-side impedance. The load voltage and load current supplied to the load 8 are measured continuously in real time by a measuring unit 96 provided between the DC-DC converter 7 and the load 8. Note that the measuring unit 96 is not limited to measuring the load voltage, and may also measure the load current, or both.

[0041] Specifically, as shown in FIG. 4, the function showing the relationship between the load voltage and the load current includes a function showing the relationship between the load voltage and the load current in an idling state (converter OFF) in which the input voltage to the DC-DC converter 7 (e.g., 15 V) is equal to or lower than the operating power (e.g., 12 V) of the DC-DC converter 7 and the DC-DC converter 7 is not operating, and a function showing the relationship between the load voltage and the load current in a state (converter ON) in which 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.

[0042] As shown in FIG. 5, 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).

[0043] The function showing the relationship between the load voltage and the load current and the function showing the relationship between the load current and the load side impedance may be calculated in advance by experiments or the like, and are not limited to the linear function graphs exemplified in Figures 4 and 5.

[0044] The control unit 95 controls the operation of the coil moving mechanism 9 based on the measurement values ​​of the measurement unit 96 and various functions stored in the storage unit 94. Details of the operation control by the control unit 95 will be described later.

[0045] 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 using the impedance matching mechanism in response to fluctuations in the load-side impedance measured by the measurement unit 96, and can reduce the difference between the input-side impedance and the load-side impedance at the input terminal IE in real time.

[0046] <Impedance matching processing> Next, the impedance matching process performed by the coil moving mechanism 9 will be described with reference to the drawings.

[0047] First, we will explain why the load-side impedance varies depending on whether the DC-DC converter 7 is on or off. In this embodiment, we will explain an example in which the load-side impedance varies depending on whether the DC-DC converter 7 is on or off, but the load-side impedance can vary not only due to whether the DC-DC converter 7 is on or off, but also due to, for example, changes in the relative position between the transmitting coil 32 and the receiving coil 41, changes in the driving status (output) of the load 8, etc., and it goes without saying that this can be used to suppress variations in the load impedance due to these various factors.

[0048] As shown in Fig. 4, when the DC-DC converter 7 is idling (converter OFF), the output voltage of the DC-DC converter 7 is almost zero and the load current is also very small. Furthermore, as can be seen from Fig. 5, when the load current is small, the load-side impedance is extremely large.

[0049] On the other hand, as shown in Fig. 4, when the DC-DC converter 7 is operating (converter ON), a load voltage corresponding to the input voltage to the DC-DC converter 7 is output, and the load current increases rapidly in proportion to the load voltage. Furthermore, Fig. 5 shows that when the load current is large, the load-side impedance is extremely small.

[0050] In this way, while the load side impedance varies depending on the operating state of the DC-DC converter 7, the input side impedance is fixed at a predetermined value (for example, 50Ω). As a result, the input side impedance and the load side impedance do not match, and reflected waves are generated at the input terminal IE, which may reduce the transmission efficiency or may cause a system failure due to insufficient transmitted power.

[0051] Therefore, the controller 93 increases or decreases the impedance of the circuit in the power transmitting device 3 in accordance with the fluctuation of the load side impedance.

[0052] Specifically, first, the control unit 95 calculates the load current based on the load voltage measured by the measurement unit 96 and the function shown in Fig. 4. The control unit 95 also calculates the load-side impedance based on the calculated load current and the function shown in Fig. 5.

[0053] Next, the control unit 95 controls the coil moving mechanism 9 to adjust the impedance of the circuit in the power transmitting device 3 so that the load-side impedance matches the input-side impedance.

[0054] 2(b) and 2(c), when the DC-DC converter 7 is idling and the load impedance is large relative to the input impedance, the plunger 91a displaces the power feeding coil 31, causing the coil axis 31a of the power feeding coil 31 to coincide with or approach the coil axis 32a of the power transmitting coil 32, thereby increasing the magnetic inductive coupling between the power feeding coil 31 and the power transmitting coil 32 and reducing the impedance of the circuit within the power transmitting device 3. As a result, the load impedance at the input terminal IE decreases, and the difference with the input impedance is alleviated.

[0055] On the other hand, when the DC-DC converter 7 is operating and the load impedance is smaller than the input impedance, the plunger 91a displaces the power feed coil 31, and the coil axis 31a of the power feed coil 31 moves away from the coil axis 32a of the power transmission coil 32, which weakens the magnetic inductive coupling between the power feed coil 31 and the power transmission coil 32 and increases the impedance of the circuit within the power transmitter 3. As a result, the load impedance at the input terminal IE increases, and the difference with the input impedance is alleviated.

[0056] The function of the offset amount (stroke amount of the plunger 91a) between the coil axis 31a of the power feeding coil 31 and the coil axis 32a of the power transmitting coil 32 and the change amount of impedance of the circuit in the power transmitting device 3 is obtained in advance by an experiment or the like.

[0057] Furthermore, instead of displacing the power supply coil 31 in a direction perpendicular to the coil axis direction, the coil moving mechanism 9 may have the swing mechanism 92 swing the power supply coil 31 based on a function of the inclination of the coil axis 31 a of the power supply coil 31 and the coil axis 32 a of the power transmission coil 32, the distance between the power supply coil 31 and the power transmission coil 32, and the amount of change in impedance of the circuit in the power transmission device 3, which have been obtained in advance through experiments or the like.

[0058] Specifically, when the DC-DC converter 7 is idling, as shown in FIGS. 3(b) and 3(c), the swing mechanism 92 swings the power supply coil 31, so that the coil axis 31a of the power supply coil 31 becomes nearly parallel to the coil axis 32a of the power transmission coil 32 and the power supply coil 31 approaches the power transmission coil 32. As a result, the magnetic inductive coupling between the power supply coil 31 and the power transmission coil 32 becomes closer, the impedance of the circuit in the power transmission device 3 decreases, and the difference between the input impedance and the load impedance at the input terminal IE is alleviated.

[0059] On the other hand, when the DC-DC converter 7 is operating, the swing mechanism 92 swings the power supply coil 31, causing the coil axis 31a of the power supply coil 31 to tilt relative to the coil axis 32a of the power transmission coil 32 and moving the power supply coil 31 away from the power transmission coil 32. As a result, the magnetic inductive coupling between the power supply coil 31 and the power transmission coil 32 becomes weaker, the impedance of the circuit within the power transmission device 3 increases, and the difference between the input impedance and the load impedance at the input terminal IE is alleviated.

[0060] In this way, the wireless power supply system 1 of this embodiment is a wireless power supply system 1 that transmits power by a magnetic field resonance method, and is configured to include a power transmitting device 3 having a power transmitting side resonant circuit 36 ​​including a power transmitting coil 32, a power receiving device 4 having a power receiving side resonant circuit 43 including a power receiving coil 41 and supplying power received via the power receiving coil 41 to a load 8, and an impedance matching mechanism that performs impedance matching processing to alleviate the difference between the load side impedance, which is the impedance of the circuit from the input terminal IE of the power transmitting device 3 to the load 8 side, and the input side impedance, which is the impedance of the circuit from the input terminal IE of the power transmitting device 3 to the AC power source 5 side.

[0061] With this configuration, when the load side impedance and the input side impedance do not match, the difference between the input side impedance and the load side impedance as seen from the input terminal IE is alleviated by the impedance matching process, thereby suppressing the occurrence of reflected waves at the input terminal IE and avoiding system failures caused by reduced power transmission efficiency and reduced transmitted power.

[0062] Furthermore, in the wireless power supply system 1 according to this embodiment, the power transmission device 3 further includes a power supply coil 31 that is arranged to be magnetically coupled to the power transmission coil 32 and transmits power to the power transmission coil 32, and the impedance matching mechanism is a coil moving mechanism 9 that changes the relative positions of the power supply coil 31 and the power transmission coil 32.

[0063] With this configuration, the magnetic coupling between the power supply coil 31 and the power transmission coil 32 becomes looser or tighter depending on the relative positional relationship between the power supply coil 31 and the power transmission coil 32, thereby increasing or decreasing the impedance of the circuit within the power transmission device 3 and reducing the difference between the input impedance and the load impedance as seen from the input terminal IE. This suppresses the generation of reflected waves at the input terminal IE, making it possible to avoid a decrease in power transmission efficiency and a system failure due to a decrease in transmitted power.

[0064] Furthermore, the wireless power supply system 1 according to this embodiment further includes a DC-DC converter 7 that converts the output voltage of the power receiving device 4 into a predetermined voltage, and the coil moving mechanism 9 is configured to move the power supply coil 31 relative to the power transmission coil 32 according to the operating state of the DC-DC converter 7.

[0065] With this configuration, even if the load-side impedance suddenly increases or decreases as the DC-DC converter 7 is turned on or off, the magnetic coupling between the power supply coil 31 and the power transmission coil 32 becomes looser or tighter depending on the relative positional relationship between the power supply coil 31 and the power transmission coil 32, thereby increasing or decreasing the impedance of the circuit within the power transmission device 3 and reducing the difference between the input-side impedance and the load-side impedance at the input terminal IE. This suppresses the generation of reflected waves at the input terminal IE, making it possible to avoid a decrease in power transmission efficiency and a system failure due to a decrease in transmitted power.

[0066] The power transmitting device 3 further includes a power feeding coil 31 for generating an electromotive force in the power transmitting coil 32, and the coil moving mechanism 9 is configured to move the position of the power feeding coil 31.

[0067] With this configuration, for example, if the wireless power supply system 1 is configured as a two-coil system having only the transmitting coil 32 and the receiving coil 41, moving the position of the transmitting coil 32 to vary the load-side impedance may result in the coil axis 32a of the transmitting coil 32 and the coil axis of the receiving coil 41 not being coaxial, which may result in a decrease in power transmission efficiency. However, by transmitting power to the transmitting coil 32 via the feeding coil 31, the positional relationship between the feeding coil 31 and the transmitting coil 32 can be changed without changing the positional relationship between the transmitting coil 32 and the receiving coil 41, thereby controlling the load-side impedance and maintaining good power transmission efficiency.

[0068] Furthermore, the present invention can be modified in various ways other than those described above without departing from the spirit of the present invention, and it goes without saying that the present invention also covers such modifications.

[0069] Furthermore, in the above-described embodiment, the cause of fluctuation in the load side impedance has been described as fluctuation in the load current due to the on / off switching of the DC-DC converter 7, but the cause of fluctuation in the load side impedance is not limited to this.

[0070] For example, it is conceivable that the load-side impedance fluctuates with the movement of the power supply target object 2. In that case, the coil moving mechanism 9 may move the relative positions of the power supply coil 31 and the power transmission coil 32 so that the impedance of the power transmission-side resonant circuit 36 ​​and the impedance of the power reception-side resonant circuit 43 match.

[0071] In the above-described embodiment, the coil moving mechanism 9 that moves the power supply coil 31 relative to the power transmission coil 32 has been described as an example of the impedance matching mechanism. However, the configuration of the coil moving mechanism 9 is not limited to this, as long as it is a mechanism that can change the positional relationship between the power supply coil 31 and the power transmission coil 32.

[0072] For example, the coil moving mechanism 9 may be either the forward / backward movement of the linear motion mechanism 91 or the swinging movement of the swinging mechanism 92, or the power supply coil 31 may be moved by a combination of the forward / backward movement of the linear motion mechanism 91 and the swinging movement of the swinging mechanism 92, or instead of the linear motion mechanism 91 and the swinging mechanism 92, the power supply coil 31 may be slid along the coil axial direction so that the power supply coil 31 moves toward or away from the power transmission coil 32.

[0073] Furthermore, when the power receiving coil 41 is fixed at a predetermined position, the coil movement mechanism 9 may be configured to change the relative positions of the power transmitting coil 32 and the power receiving coil 41. This causes the magnetic inductive coupling between the power feeding coil 31 and the power transmitting coil 32 to become looser or tighter, increasing or decreasing the impedance of the circuit in the power transmitting device 3, thereby reducing the difference between the input impedance and the load impedance at the input terminal IE.

[0074] In addition, the coil moving mechanism 9 may be configured to change the relative positions of the power transmitting coil 32 and the power receiving coil 41 depending on the positional relationship between the power transmitting coil 32 and the power receiving coil 41 so that the impedance of the power transmitting side resonant circuit 36 ​​matches the impedance of the power receiving side resonant circuit 43. In the above-described embodiment, the case where the power feeding coil 31, the power transmitting coil 32, and the power receiving coil 41 are all in a resonant state in order to reduce the imaginary part of the impedance to zero and suppress the generation of reactive power has been described as an example. However, even if the capacitor 33 is not connected to the power feeding coil 31, for example, reactive power occurs in the input impedance, but power transmission itself is possible, so only the power transmitting coil 32 and the power receiving coil 41 may be in a resonant state.

[0075] Furthermore, in the above-described embodiment, the wireless power supply system 1 has been described as a three-coil system configuration including the power supply coil 31, the power transmitting coil 32, and the power receiving coil 41, but the wireless power supply system may be a two-coil system having only the power transmitting coil 32 and the power receiving coil 41 without the power supply coil 31. In this case, the coil moving mechanism 9 is configured to change the relative positions of the power transmitting coil 32 and the power receiving coil 41, thereby enabling control of the load-side impedance. [Explanation of symbols]

[0076] 1: Wireless power supply system 2: Power supply object 3: Power transmission equipment 31: Power supply coil 31a: Coil axis (of the power supply coil) 32: Transmission coil 32a: Coil axis (of the transmitting coil) 33, 34: Capacitor 35: Power supply side resonant circuit 36: Power transmission side resonant circuit 4: Power receiving device 41: Receiving coil 42: Capacitor 43: Receiving side resonant circuit 5: AC power supply 6: Rectifier circuit 61: Diode 62: Capacitor 7: DC-DC converter (voltage conversion circuit) 8: Load 9: Coil moving mechanism 91: Linear motion mechanism 91a: Plunger 91b: Case 92: Oscillating mechanism 93: Controller 94: Storage section 95: Control section 96: Measuring part IE: Input terminal

Claims

1. A wireless power supply system that transmits and receives power using magnetism, a power transmitting device including: a power transmitting-side resonant circuit including a power transmitting coil; and a power feeding coil that is arranged to be magnetically coupled with the power transmitting coil and feeds power supplied from an input terminal to the power transmitting coil by a magnetic field resonance method; a power receiving device including a power receiving side resonant circuit including a power receiving coil and a voltage conversion circuit that converts an output voltage of power received by the power receiving coil into a predetermined voltage, the power receiving device supplying the power converted by the voltage conversion circuit to a load; an impedance matching mechanism that performs impedance matching processing to reduce a difference between a load-side impedance, which is the impedance of a circuit from an input end of the power transmitting device to a load, and an input-side impedance, which is the impedance of a circuit from the input end of the power transmitting device to a power supply device, by changing a coupling strength of a magnetic field coupling between the power supply coil and the power transmitting coil in accordance with an operating state of the voltage conversion circuit; A wireless power supply system comprising:

2. a measurement unit that measures a load current supplied to the load or a load voltage applied to the load; The wireless power supply system according to claim 1 , wherein the impedance matching mechanism performs impedance matching processing in accordance with the measurement result of the measurement unit.

3. 2. The wireless power supply system according to claim 1, wherein power is supplied from the power transmitting coil to the power receiving coil by a magnetic field resonance method.

4. a power transmitting device including a power transmitting side resonant circuit including a power transmitting coil, and a power feeding coil that is arranged to be magnetically coupled with the power transmitting coil and feeds power supplied from an input terminal to the power transmitting coil by a magnetic field resonance method, A wireless power feeding method for transmitting and receiving power by utilizing magnetism to a power receiving device including a power receiving side resonant circuit including a power receiving coil and a voltage conversion circuit that converts an output voltage of power received by the power receiving coil into a predetermined voltage, the power receiving device supplying the power converted by the voltage conversion circuit to a load, a power supply circuit that changes the strength of magnetic field coupling between the power supply coil and the power transmission coil in accordance with the operating state of the voltage conversion circuit, thereby reducing the difference between a load-side impedance, which is the impedance of a circuit from the input end of the power transmission device to the load side, and an input-side impedance, which is the impedance of a circuit from the input end of the power transmission device to the power supply device side.

5. A wireless power transmission system that transmits power to a power receiving device using magnetism, a power transmitting device including a power transmitting side resonant circuit including a power transmitting coil; and a power feeding coil arranged to be magnetically coupled with the power transmitting coil and feeding power supplied from an input terminal to the power transmitting coil by a magnetic field resonance method, the power transmitting device feeding the power to a load via the power receiving device; an impedance matching mechanism that performs impedance matching processing to reduce a difference between a load-side impedance, which is the impedance of a circuit from an input end of the power transmitting device to a load, and an input-side impedance, which is the impedance of a circuit from the input end of the power transmitting device to a power supply device, by changing a coupling strength of a magnetic field coupling between the power feeding coil and the power transmitting coil in accordance with an operating state of a voltage conversion circuit that converts an output voltage of the power receiving device into a predetermined voltage; A wireless power transmission system comprising:

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