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

Abstract

To provide a wireless power feeding system that reduces the reduction in power feeding efficiency even when the impedance of a load-side circuit fluctuates.SOLUTION: A wireless power feeding system 1 includes a power transmission device 3 provided with a power transmission side resonant circuit 36 including a power transmission coil 32, a power reception device 4 provided with a power reception side resonant circuit 43 including a power reception coil 41, for supplying power received via the power reception coil 41 to a load, a DC-DC converter 7 provided between the power reception device 4 and the load 8 to control the voltage supplied to the load 8, and an impedance adjusting device 9 to mitigate load-side impedance fluctuations.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In recent years, research and development of wireless power supply systems using magnetic resonance coupling (magnetic resonance) has been progressing. Magnetic resonance coupling refers to a state in which the vibration of a magnetic field generated by an AC current flowing through a resonance circuit of a power transmitting device is transmitted to a resonance circuit of a power receiving device and resonates, resulting in a strong coupling of the magnetic fields generated by the coils of each resonance circuit. Wireless power supply using magnetic resonance coupling has the advantage of a longer possible power supply distance compared to conventional wireless power supply 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, the impedance (total impedance) of the load side circuit including the power receiving device and the load, etc., as viewed from the power transmitting device, is set to be equivalent to the impedance (input side impedance) of the power source side as viewed from the power transmitting device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-505369 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-mentioned load side circuit is connected to a driving member such as a battery or a motor, and the battery or the motor becomes 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 supply system, since the total impedance fluctuates according to the fluctuation of the current flowing through the load side circuit, the total impedance and the input side impedance do not match, and a reflected wave is generated in the system, the power transmission efficiency is significantly reduced, and the transmitted power is reduced, which may result in a system failure.

[0006] Therefore, a technical problem arises that must be solved in order to reduce the decrease in power transmission efficiency even when the impedance of the load side circuit fluctuates, 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 supply system according to the present invention is a wireless power supply system that transmits power by a magnetic resonance method, and includes: a power transmitting device having a power transmitting side resonant circuit including a power transmitting coil; a power receiving device having a power receiving side resonant circuit including a power receiving coil and supplying power received via the power receiving coil to a load; a voltage conversion circuit provided between the power receiving device and the load and controlling a voltage supplied to the load; and an impedance adjustment device disposed between the voltage conversion circuit and the load and mitigating fluctuations in load side impedance, which is the impedance of a circuit on the load side as viewed from the voltage conversion circuit. The impedance adjustment device includes a first resistance element provided in series with the load, a second resistance element provided in parallel with the load, and a resistance control unit that variably controls the resistance values ​​of the first resistance element and the second resistance element. is. Effect of the Invention

[0008] The present invention reduces fluctuations in the load-side impedance, thereby suppressing the occurrence of reflected waves and making it possible to avoid a decrease in power transmission efficiency and the associated risk of system failure. [Brief description 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. [Diagram 2] 4 is a graph showing the relationship between a load voltage and a load current. [Diagram 3] 4 is a graph showing the relationship between a load current and a load side impedance. [Figure 4] FIG. 13 is a diagram showing a comparative example of the present invention, which is a circuit that does not have an impedance adjustment device. [Diagram 5] FIG. 2 is a diagram illustrating a circuit to be adjusted shown in FIG. [Figure 6] FIG. 11 is a diagram showing a main part of a wireless power supply system according to a first modified example of the present invention. [Figure 7] FIG. 13 is a diagram showing a main part of a wireless power supply system according to a second modified example of the present invention. [Figure 8] FIG. 13 is a diagram showing a main part of a wireless power supply system according to a third modified example of the present invention. [Figure 9] FIG. 13 is a diagram showing a main part of a wireless power supply system according to a fourth modified example of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

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

[0012] In addition, the drawings may exaggerate characteristic parts to make the features easier to understand, and the dimensional ratios of the components may not be the same as the actual ones. 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 object 2 in a non-contact manner by utilizing magnetic field resonant coupling (magnetic field resonance). The power supply object 2 is, for example, a vehicle, a robotic flying object, 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 winding a copper wire or the like having 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 of the copper wire 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 becomes larger than that of a single copper wire of the same diameter, allowing a larger current to flow and suppressing current loss.

[0016] The power supply coil 31 is supplied with AC power from the AC power source 5. For example, the AC power is set to 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 supply coil 31 on the AC power source 5 side is referred to as an "input end IE." Note that in this embodiment, a case will be described in which the power supply coil 31 and the AC power source 5 are directly connected via the input end IE, but the power supply coil 31 and the AC power source 5 may be directly connected via the input end IE or indirectly connected via a coaxial cable or the like provided between the AC power source 5 and the input end IE.

[0017] The power supply coil 31 and the capacitor 33 are connected in series to configure a power supply side resonant circuit 35. When an AC voltage having a frequency corresponding to a 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 so as to penetrate the power supply 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 33 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 so as to penetrate 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 winding a copper wire or the like having high electrical conductivity in a circular shape. Note that, like 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 the 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 the capacitor 33. As a result, an induced current flows in the power receiving coil 41 due to the vibration of the magnetic field 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. In this way, the magnetic fields of the power transmitting coil 32 and the power receiving coil 41 resonate and are firmly coupled.

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

[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 the impedance adjustment device> Next, with reference to the drawings, an impedance adjustment device 9 will be described which reduces fluctuations in the impedance (hereinafter referred to as the "load side impedance") of the circuit on the load 8 side (the circuit to be adjusted) as viewed from the DC-DC converter 7 so that the impedance (hereinafter referred to as the "total impedance") of the circuit (load side circuit) including the power transmission device 3, the power receiving device 4, the rectifier circuit 6, the DC-DC converter 7 and the load 8 from the input terminal IE falls within a predetermined range with respect to the input impedance of the AC power source 5.

[0027] As shown in FIG. 1, the impedance adjusting device 9 includes a first variable resistor 91 provided in series with the load 8, and a second variable resistor 92 provided in parallel with the load 8.

[0028] The operation of the impedance adjusting device 9 is controlled by a controller 93. The controller 93 is composed of, for example, a CPU, a memory, etc. The functions of the controller 93 may be realized by controlling using software, or may be realized by operating using hardware. The controller 93 is functionally divided into a resistance control unit 94 and a storage unit 95.

[0029] The resistance control unit 94 can control the resistance value of the first variable resistor 91 and the resistance value of the second variable resistor 92 based on various functions (described later) stored in the storage unit 95 and measured values ​​of the measurement unit 96. By increasing or decreasing the resistance values ​​of the first variable resistor 91 and the second variable resistor 92, the impedance adjustment device 9 can arbitrarily adjust the composite impedance of the circuit to be adjusted.

[0030] The storage unit 95 stores a function indicating the relationship between the load voltage and the 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 the load side impedance. The load voltage and the load current supplied to the load 8 are continuously measured in real time by a measurement unit 96 provided between the DC-DC converter 7 and the load 8. Therefore, the controller 93 can detect the load side impedance and its fluctuation in real time based on the values ​​of the load voltage and the load current measured by the measurement unit 96. Note that the measurement unit 96 is not limited to one that measures the load voltage, and may be one that measures the load current, or both.

[0031] Specifically, as shown in FIG. 2, the function showing the relationship between the load voltage and the load current includes a function that shows the relationship between the load voltage and the load current in an idling state (converter OFF) in which the input voltage to DC-DC converter 7 is equal to or lower than the operating voltage of DC-DC converter 7 (e.g., 12 V) and DC-DC converter 7 is not operating, and a function that shows the relationship between the load voltage and the load current in a state (converter ON) in which the input voltage to DC-DC converter 7 exceeds the operating power of DC-DC converter 7 and DC-DC converter 7 is operating.

[0032] Moreover, as shown in FIG. 3, 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).

[0033] 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 are calculated in advance through experiments or the like, and are not limited to the graphs of linear functions exemplified in Figures 2 and 3.

[0034] In this way, in the wireless power supply system 1 of this embodiment, the impedance adjusting device 9 can instantly adjust the composite impedance of the circuit to be adjusted in response to fluctuations in the load side impedance measured by the measuring unit 96 so that the impedance fluctuations in the load side impedance do not affect the total impedance, and the difference between the input side impedance at the input terminal IE and the total impedance can be mitigated in real time.

[0035] <Impedance adjustment> Next, the impedance adjustment performed by the impedance adjustment device 9 will be described with reference to the drawings.

[0036] First, a description will be given of the reason why the load impedance varies depending on whether the DC-DC converter 7 is on or off. In this embodiment, a case where the load impedance varies depending on whether the DC-DC converter 7 is on or off will be described as an example, but the variation in the load impedance can occur not only due to the on / off of the DC-DC converter 7, but also due to, for example, a change in the relative position between the transmitting coil 32 and the receiving coil 41, a change in the driving condition (output) of the load 8, etc., and it goes without saying that the present invention can be used to suppress the variation in the load impedance due to these various factors.

[0037] As shown in Fig. 2, 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. Also, as shown in Fig. 3, when the load current is small, the load side impedance is extremely large.

[0038] On the other hand, as shown in Fig. 2, when the DC-DC converter 7 is operating (converter ON), a load voltage according to the input voltage to the DC-DC converter 7 is output, and the load current increases rapidly in proportion to the load voltage. Also, from Fig. 3, it can be seen that when the load current is large, the load side impedance is extremely small.

[0039] In this way, as the load side impedance varies depending on the operating state of the DC-DC converter 7, the total impedance including the load side impedance varies, whereas the input side impedance is fixed at a predetermined value (for example, 50 Ω). As a result, the total impedance and the input side impedance do not match, and a reflected wave is generated at the input terminal IE, reducing the transmission efficiency or causing a system failure due to insufficient transmitted power.

[0040] Therefore, when the DC-DC converter 7 is in an operating state (converter ON), the impedance adjustment device 9 increases or decreases the resistance values ​​of the first variable resistor 91 and the second variable resistor 92 as necessary to mitigate impedance fluctuations in the load side impedance, i.e., to adjust the synthetic impedance ΣR of the circuit to be adjusted so that the impedance fluctuations in the load side impedance do not affect the total impedance.

[0041] Specifically, first, the resistance control unit 94 calculates the load current based on the load voltage measured by the measurement unit 96 and the function shown in Fig. 2. The resistance control unit 94 also calculates the load side impedance based on the calculated load current and the function shown in Fig. 3.

[0042] Next, the resistance control section 94 adjusts the resistance values ​​of the first variable resistor 91 and the second variable resistor 92 so that the total impedance falls within a predetermined range (for example, ±10%) with respect to the input impedance.

[0043] For example, in the case of a circuit without a resistive element as shown in FIG. 4, when comparing a state in which the load current is small and the load side impedance is large with a state in which the load current is large and the load side impedance is small, the fluctuation in the load side impedance is extremely large, and the ratio of the load side impedances (impedance ratio) in each of cases 1A and 1B shown as examples in the table in FIG. 4 is 100 times.

[0044] On the other hand, as shown in FIG. 5, when the load current is small and the load side impedance R0 is large, the resistance control unit 94 reduces the resistance value R1 of the first variable resistor 91 and increases the resistance value R2 of the second variable resistor 92, thereby reducing the load side impedance (synthetic impedance) ΣR after impedance adjustment.

[0045] In addition, when the load current is large and the load side impedance R0 is small, the resistance control unit 94 increases the resistance value R1 of the first variable resistor 91 and decreases the resistance value R2 of the second variable resistor 92, thereby raising the composite impedance ΣR of the circuit to be adjusted.

[0046] The resistance value R1 of the first variable resistor 91 and the resistance value R2 of the second variable resistor 92, which are variably controlled by the resistance control section 94, are obtained in advance through experiments or the like in the following procedure.

[0047] First, when the input impedance (e.g., 50Ω) of the AC power supply 5 is approximately equal to the total impedance, that is, when the load 8 is being supplied with rated power in rated operation, the rated impedance (R0_th) is measured in advance.

[0048] Next, based on the measurement results of the voltage and current supplied to the load 8 measured by the measurement unit 96, the resistance control unit 94 calculates the load side impedance (R0) before impedance processing.

[0049] When the load side impedance R0 is equal to or greater than the rated impedance (R0_th), the resistance value R1 of the first variable resistor 91 is set to 0 Ω, and the resistance value R2 of the second variable resistor 92 is set to satisfy the formula 1 / (R0_th)=(1 / R0)+(1 / R2).

[0050] For example, as in case 2A illustrated in the table in FIG. 5, if the load side impedance R0 before impedance adjustment is set to 200 Ω, the resistance value R1 of the first variable resistor 91 is set to 0 Ω, and the resistance value R2 of the second variable resistor 92 is set to 66.7 Ω, then the combined impedance ΣR of the circuit to be adjusted will be 50 Ω.

[0051] On the other hand, when the load side impedance R0 is smaller than the rated impedance (R0_th), the resistance value R2 of the second variable resistor 92 is set extremely large, and the resistance value R1 of the first variable resistor 91 is set so as to satisfy the formula (R0_th)-R0=R1.

[0052] For example, as in case 2B illustrated in the table in FIG. 5, if the load side impedance R0 before impedance adjustment is set to 2 Ω, the resistance value R1 of the first variable resistor 91 is set to 48 Ω, and the resistance value R2 of the second variable resistor 92 is set to ∞ Ω, then the combined impedance ΣR of the circuit to be adjusted will be 50 Ω.

[0053] In this way, the resistance control unit 94 controls the resistance value R1 of the first variable resistor 91 and the resistance value R2 of the second variable resistor 92 so that the synthetic impedance ΣR of the circuit to be adjusted approximately matches the rated impedance (R0_th).

[0054] In this manner, the wireless power supply system 1 according to 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 the power received via the power receiving coil 41 to a load, a DC-DC converter 7 provided between the power receiving device 4 and the load 8 for controlling the voltage supplied to the load 8, and an impedance adjustment device 9 for mitigating fluctuations in the load side impedance.

[0055] With this configuration, the impedance adjustment device 9 adjusts the synthetic impedance ΣR of the circuit to be adjusted so that fluctuations in the load side impedance due to the operating state of the DC-DC converter 7 do not affect the total impedance, thereby mitigating the difference between the input side impedance as seen from the input terminal IE and the total impedance, thereby suppressing the occurrence of reflected waves at the input terminal IE and avoiding system failures due to reduced transmission efficiency and reduced transmitted power.

[0056] Moreover, in the wireless power supply system 1 according to this embodiment, the impedance adjustment device 9 includes the first variable resistor 91 and the second variable resistor 92 that are provided in parallel and in series with the load 8, respectively.

[0057] With this configuration, by adjusting the resistance value R1 of the first variable resistor 91 and the resistance value R2 of the second variable resistor 92, the synthetic impedance ΣR of the circuit to be adjusted can be adjusted so that impedance fluctuations in the load side impedance R0 do not affect the overall impedance.

[0058] In addition, the wireless power supply system 1 of this embodiment is configured such that the impedance adjustment device 9 includes a first variable resistor 91 arranged in parallel with the load 8, a second variable resistor 92 arranged in series with the load 8, and a resistance control unit 94 that variably controls the resistance values ​​R1, R2 of the first variable resistor 91 and the second variable resistor 92.

[0059] With this configuration, the resistance control unit 94 can appropriately adjust the resistance value R1 of the first variable resistor 91 and the resistance value R2 of the second variable resistor 92, so that the composite impedance ΣR of the circuit to be adjusted can be smoothly increased or decreased.

[0060] Furthermore, in the wireless power supply system 1 according to this embodiment, the resistance control unit 94 is configured to make the resistance value R1 of the first variable resistor 91 smaller than the resistance value R2 of the second variable resistor 92 when the load side impedance R0 is equal to or greater than the rated impedance (R0_th), and to make the resistance value R2 of the second variable resistor 92 larger than the resistance value R1 of the first variable resistor 91 when the load side impedance R0 is smaller than the rated impedance (R0_th).

[0061] This configuration enables the resistance control section 94 to maintain a preferable state in which the synthetic impedance ΣR of the circuit to be adjusted and the rated impedance (R0_th) approximately match.

[0062] The impedance adjustment device 9 is not limited to a configuration including a first variable resistor 91 and a second variable resistor 92, and may be configured to include only one of the first variable resistor 91 and the second variable resistor 92.

[0063] For example, in the case where only the first variable resistor 91 is provided in the circuit to be adjusted as shown in Fig. 6, when the load side impedance R0 is equal to or greater than the rated impedance (R0_th), the resistance control unit 94 reduces the resistance value R1 of the first variable resistor 91. For example, in case 3A illustrated in the table in Fig. 6, when the load side impedance R0 before impedance adjustment is set to 200Ω and the resistance value R1 of the first variable resistor 91 is set to 2Ω, the combined impedance ΣR of the circuit to be adjusted becomes 202Ω.

[0064] On the other hand, when the load-side impedance R0 is smaller than the rated impedance (Ro_th), the resistance control unit 94 increases the resistance value of the first variable resistor 91. For example, in case 3B illustrated in the table in Fig. 6, when the load-side impedance R0 before impedance adjustment is set to 2Ω and the resistance value R1 of the first variable resistor 91 is set to 200Ω, the composite impedance ΣR of the circuit to be adjusted becomes 202Ω.

[0065] In this way, the resistance control unit 94 controls the resistance value R1 of the first variable resistor 91, so that even if fluctuations occur in the load side impedance R0 due to the operating state of the DC-DC converter 7, the composite impedance ΣR of the circuit to be adjusted is maintained approximately constant so that the impedance fluctuations in the load side impedance R0 do not affect the overall impedance.

[0066] Also, for example, in the case where only the second variable resistor 92 is provided as shown in Fig. 7, when the load side impedance R0 is equal to or greater than the rated impedance (Ro_th), the resistance control unit 94 reduces the resistance value R2 of the second variable resistor 92. For example, in case 4A illustrated in the table in Fig. 7, when the load side impedance R0 before impedance adjustment is set to 200Ω and the resistance value R2 of the second variable resistor 92 is set to 2Ω, the combined impedance ΣR of the circuit to be adjusted is 1.98Ω.

[0067] On the other hand, when the load-side impedance R0 is smaller than the rated impedance (Ro_th), the resistance control unit 94 increases the resistance value R2 of the second variable resistor 92. For example, in case 4B illustrated in the table in Fig. 7, when the load-side impedance R0 before impedance adjustment is set to 2Ω and the resistance value R2 of the second variable resistor 92 is set to 200Ω, the combined impedance ΣR of the circuit to be adjusted is 1.98Ω.

[0068] In this way, the resistance control unit 94 controls the resistance value R2 of the second variable resistor 92, so that even if fluctuations occur in the load side impedance R0 due to the operating state of the DC-DC converter 7, the composite impedance ΣR of the circuit to be adjusted is maintained approximately constant so that the impedance fluctuations in the load side impedance R0 do not affect the overall impedance.

[0069] Furthermore, the resistance element of the impedance adjustment device 9 is not limited to the variable resistor described above, and may be a fixed resistor whose resistance value is fixed.

[0070] For example, when a fixed resistor 97 is provided in parallel with the load 8 as shown in FIG. 8, it is preferable that the resistance value R3 of the fixed resistor 97 is set to approximately the median value between the maximum and minimum values ​​of the load side impedance R0 before impedance adjustment, which is calculated in advance by an experiment or the like.

[0071] In case 5A (when the load side impedance is equal to or greater than the rated impedance) illustrated in the table in FIG. 8, if the load side impedance R0 before impedance adjustment is set to 200 Ω and the resistance value R3 of the fixed resistor 97 is set to 100 Ω, the composite impedance ΣR of the circuit to be adjusted will be 66.6 Ω.

[0072] On the other hand, in case 5B (when the load side impedance is smaller than the rated impedance) illustrated in the table in FIG. 8, if the load side impedance R0 before impedance adjustment is set to 2 Ω and the resistance value R3 of the fixed resistor 97 is set to 100 Ω, the composite impedance ΣR of the circuit to be adjusted will be 1.96 Ω.

[0073] In this way, it can be seen that the impedance ratio of the adjustment target circuit having no resistance element as shown in Fig. 4 is 100 times, while the impedance ratio of the adjustment target circuit provided with fixed resistor 97 is suppressed to 34 times. Therefore, even when fixed resistor 97 is provided, the effect of impedance fluctuation of load side impedance R0 caused by the operating state of DC-DC converter 7 on the total impedance can be reduced.

[0074] Furthermore, in the above-described embodiment and modified examples, an example has been described in which the impedance adjustment device 9 adjusts the composite impedance ΣR of the circuit to be adjusted to approximately match the rated impedance (R0_th) when the DC-DC converter 7 is in an operating state (converter ON). However, the impedance adjustment device 9 may also be configured to lower the load side impedance R0 when the DC-DC converter 7 is idling (converter OFF).

[0075] Such an impedance adjusting device 9 may have, for example, a configuration in which a third variable resistor 98 is provided in parallel with the DC-DC converter 7, and a resistance control section 94 variably controls the resistance value R4 of the third variable resistor 98. When the DC-DC converter 7 is idling, sufficient power is not supplied to the load 8, but by increasing the resistance value R4 of the third variable resistor 98, the load side impedance R0 can be reduced.

[0076] 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 extends to such modifications.

[0077] In the above-described embodiment and modified example, the load impedance varies due to the load current fluctuation caused by the on / off of the DC-DC converter 7, but the load impedance variation is not limited to this. For example, the load impedance may vary due to the movement of the power supply target 2.

[0078] In addition, in the above-described embodiment and modified examples, one first variable resistor 91 arranged in series with the load 8, one second variable resistor 92 arranged in parallel with the load 8, one fixed resistor 97 arranged in series with the load 8, and one third variable resistor 98 arranged in parallel with the DC-DC converter 7 are exemplified as means for adjusting the synthetic impedance ΣR of the circuit to be adjusted, but there may be two or more of each type of resistance element.

[0079] Furthermore, the resistance elements included in the impedance adjustment device 9 are not limited to the combinations of various variable resistors and fixed resistors described in the above-mentioned embodiments and modifications, and may be any suitable combination of these.

[0080] Furthermore, as elements connected in series and / or in parallel to the load 8, in addition to the first variable resistor 91 and the second variable resistor 92, a coil or a capacitor may be arranged.

[0081] In the above-described embodiment and modified example, the case where the power supply coil 31, the power transmission 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, for example, even if the capacitor 33 is not connected to the power supply coil 31, power transmission itself is possible although reactive power is generated in the input impedance, so only the power transmission coil 32 and the power receiving coil 41 may be in a resonant state.

[0082] In addition, in the above-described embodiment and modified examples, the wireless power supply system 1 has been described using as an example a three-coil system configuration including the power supply coil 31, the power transmission coil 32, and the power receiving coil 41. However, the wireless power supply system may be a two-coil system having only the power transmission coil 32 and the power receiving coil 41 without the power supply coil 31. [Explanation of symbols]

[0083] 1: Wireless power supply system 2: Power supply object 3: Power transmission equipment 31: Power supply coil 32: 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: Impedance adjustment device 91: First variable resistor 92: Second variable resistor 93: Controller 94: Resistance control section 95: Storage section 96: Measuring part 97: Fixed resistance 98: Third variable resistor IE: Input terminal

Claims

1. A wireless power supply system that transmits power by a magnetic resonance method, A power transmitting device including a power transmitting side resonant circuit including a power transmitting coil; a power receiving device including a power receiving side resonant circuit including a power receiving coil and configured to supply power received via the power receiving coil to a load; a voltage conversion circuit provided between the power receiving device and a load, the voltage conversion circuit controlling the voltage supplied to the load; an impedance adjustment device disposed between the voltage conversion circuit and the load, which reduces fluctuations in a load-side impedance, which is an impedance of a circuit on the load side as viewed from the voltage conversion circuit; Equipped with The wireless power supply system is characterized in that the impedance adjustment device includes a first resistive element provided in series with the load, a second resistive element provided in parallel with the load, and a resistance control unit that variably controls the resistance values ​​of the first resistive element and the second resistive element.

2. The resistance control unit is when the load-side impedance is equal to or greater than a rated impedance of a circuit to be adjusted, which is a circuit on the load side as viewed from the voltage conversion circuit in a state in which rated power is being supplied to the load, the resistance value of the first resistance element is made smaller than the resistance value of the second resistance element; 2. The wireless power supply system according to claim 1, wherein when the load side impedance is smaller than a rated impedance of the circuit to be adjusted in a state in which rated power is supplied to the load, a resistance value of the second resistance element is made larger than a resistance value of the first resistance element.

3. The wireless power supply system of claim 1, further comprising a resistance element arranged in parallel with the voltage conversion circuit between the receiving side resonant circuit and the voltage conversion circuit, the resistance value of which is variably controlled by the resistance control unit so that the load side impedance remains approximately constant regardless of the operating state of the voltage conversion circuit.

4. A measurement unit for measuring a load current and / or a load voltage in the load, 4. The wireless power supply system according to claim 1, wherein the impedance adjustment device adjusts the load side impedance in accordance with a measurement result of the measurement unit.

5. A power transmitting device including a power transmitting side resonant circuit including a power transmitting coil; a power receiving device including a power receiving side resonant circuit including a power receiving coil and configured to supply power received via the power receiving coil to a load; a voltage conversion circuit provided between the power receiving device and a load, the voltage conversion circuit controlling the voltage supplied to the load; an impedance adjustment device disposed between the voltage conversion circuit and the load, which reduces fluctuations in a load-side impedance, which is an impedance of a circuit on the load side as viewed from the voltage conversion circuit; A measurement unit for measuring a load current and / or a load voltage in the load; A wireless power supply method using a wireless power supply system that transmits power by a magnetic field resonance method, comprising: The impedance adjustment device includes a first resistive element provided in series with the load, a second resistive element provided in parallel with the load, and a resistance control unit that variably controls the resistance values ​​of the first resistive element and the second resistive element, and is configured to adjust the impedance of the load side so as to mitigate fluctuations in the impedance according to the measurement results of the measurement unit.

6. A wireless power receiving system that receives power by a magnetic resonance method, a power receiving device including a power receiving side resonant circuit including a power receiving coil, receiving power transmitted from a power transmitting device including a power transmitting coil via the power receiving coil and supplying the power to a load; a voltage conversion circuit provided between the power receiving device and a load, the voltage conversion circuit controlling the voltage supplied to the load; an impedance adjustment device disposed between the voltage conversion circuit and the load, which reduces fluctuations in a load-side impedance, which is an impedance of a circuit on the load side as viewed from the voltage conversion circuit; Equipped with The wireless power receiving system is characterized in that the impedance adjustment device includes a first resistive element arranged in series with the load, a second resistive element arranged in parallel with the load, and a resistance control unit that variably controls the resistance values ​​of the first resistive element and the second resistive element.

7. A measurement unit for measuring a load current and / or a load voltage in the load, 7. The wireless power receiving system according to claim 6, wherein the impedance adjustment device adjusts the load side impedance in accordance with a measurement result of the measurement unit.

8. A wireless power supply system that transmits power by a magnetic resonance method, A power transmitting device including a power transmitting side resonant circuit including a power transmitting coil; a power receiving device including a power receiving side resonant circuit including a power receiving coil and configured to supply power received via the power receiving coil to a load; a voltage conversion circuit provided between the power receiving device and a load, the voltage conversion circuit controlling the voltage supplied to the load; an impedance adjustment device disposed between the voltage conversion circuit and the load, which reduces fluctuations in a load-side impedance, which is an impedance of a circuit on the load side as viewed from the voltage conversion circuit; Equipped with the impedance adjustment device includes a first resistance element provided in series with the load, and a resistance control unit that variably controls a resistance value of the first resistance element; a resistance element whose resistance value is variably controlled by the resistance control unit so that the load side impedance is approximately constant regardless of the operating state of the voltage conversion circuit is provided in parallel with the voltage conversion circuit between the power receiving side resonant circuit and the voltage conversion circuit.

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