Wireless power supply system and method

Abstract

To provide a wireless power supply system and method that enables low-cost, simple, and efficient wireless power transfer. [Solution] The wireless power supply system 1 transmits and receives power from the power supply device 5 between the transmitting coil 32 of the transmitting device 3 and the receiving coil 41 of the receiving device 4 of the power supply target object 2, using a magnetic field resonance method. The controller 92 estimates the load side impedance based on the voltage amplitude measured by the measuring unit 54 and the correspondence between the voltage amplitude and the load side impedance, and adjusts the inductance of the receiving coil 41 so that the estimated value of the load side impedance approaches the theoretical value of the load side impedance, thereby mitigating the difference between the load side impedance and the input side impedance.

Description

[Technical Field]

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

[0002] Research and development of wireless power transfer systems utilizing magnetic fields have been ongoing. Two known methods of power transfer using magnetism are electromagnetic coupling (electromagnetic induction) and magnetic resonance.

[0003] The magnetic resonance method transmits power through a state where the magnetic field vibrations generated by the flow of alternating current through the resonant circuit of the power transmission device are transmitted to the resonant circuit of the power receiving device, causing resonance. This results in a strong coupling of the magnetic fields generated by the coils in each resonant circuit (magnetic resonance coupling). Wireless power transfer using the magnetic resonance method has the advantage of extending the power transfer distance by several meters compared to wireless power transfer using the electromagnetic coupling method. Although the magnetic 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 resonance method.

[0004] Furthermore, as described in Patent Document 1, in order to improve the power transmission efficiency of wireless power supply systems, it has also been considered to use a Class E amplifier with extremely low switching losses in the power supply unit.

[0005] On the other hand, in wireless power transmission systems using magnetic resonance, it is known that impedance matching is necessary to minimize the difference between the impedance of the load-side circuit, including the receiving device and load, as viewed from the input terminal (IE) of the power transmission device, and the impedance of the power source as viewed from the input terminal (IE) of the power transmission device, in order to transmit power efficiently.

[0006] Patent Document 2 describes a wireless power supply system in which a directional coupler is placed between a power supply unit and a drive coil, reflected power from the drive coil side is detected by the directional coupler, and impedance matching is achieved by changing the impedance of the receiving coil according to the detected value of reflected power. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2017-093180 [Patent Document 2] Japanese Patent Publication No. 2023-175467 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] However, the directional coupler described in Patent Document 2 is very expensive, making it unavoidable that the cost of the wireless power transfer system will increase. In addition, there was the problem that incorporating the directional coupler into the wireless power transfer system required complicated adjustment work. Furthermore, power loss occurs in the directional coupler, which may reduce the power transmission efficiency of the wireless power transfer system, and power reflection occurs at the connection point of the directional coupler, which may reduce the accuracy of detecting the reflected power of the directional coupler and make it impossible to achieve impedance matching.

[0009] In particular, using the Class E amplifier described in Patent Document 1 would result in even higher costs, more complicated adjustment procedures, and a further decrease in power transmission efficiency due to load fluctuations, etc.

[0010] Therefore, technical challenges arise that need to be solved in order to perform wireless power transfer at low cost, simply, and efficiently, and the present invention aims to solve these challenges. [Means for solving the problem]

[0011] To achieve the above objective, the wireless power supply system according to the present invention comprises a power transmission device having a power transmission side resonant circuit including a power transmission coil, a power receiving unit having a power receiving side resonant circuit including a power receiving coil and a power receiving unit that can be connected to a load to which the power received by the power receiving coil is supplied, a control device for controlling the power receiving unit, and a power supply device for supplying power to the power transmission coil, wherein the power supplied from the power supply device transmits and receives power between the power transmission coil and the power receiving coil using a magnetic field resonance method, the power supply device comprising a DC conversion unit that outputs a DC voltage, and a first switching unit that performs switching operations based on a first high-frequency control signal that is input The control device comprises an element, a first inductor connected in series between the DC conversion unit and the first switching element, a first capacitor connected in parallel with the first switching element, a first resonant circuit connected in series between the power transmission device and the connection point of the first switching element and the first inductor, and a measuring unit for measuring the voltage amplitude or current amplitude of the power supply device in a predetermined range. The control device reduces the difference between the load-side impedance, which is the impedance of the circuit from the input terminal of the power transmission device to the load side, and the input-side impedance, which is the impedance of the circuit from the input terminal of the power transmission device to the power supply device side, according to the voltage amplitude or current amplitude measured by the measuring unit.

[0012] 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 includes a power transmission device equipped with a power transmission side resonant circuit including a power transmission coil, a power receiving unit equipped with a power receiving side resonant circuit including a power receiving coil and connectable to a load to which the power received by the power receiving coil is supplied, a control device for controlling the power receiving unit, and a power supply device for supplying power to the power transmission coil, wherein the power supplied from the power supply device transmits and receives power between the power transmission coil and the power receiving coil using a magnetic field resonance method, the power supply device includes a DC conversion unit that outputs a DC voltage, and a first high-frequency control signal that performs switching operations based on the input first high-frequency control signal. The control device comprises a switching element, a first inductor connected in series between the DC conversion unit and the first switching element, a first capacitor connected in parallel with the first switching element, a first resonant circuit connected in series between the power transmission device and the connection point of the first switching element and the first inductor, and a measuring unit for measuring the voltage amplitude or current amplitude of the power supply device in a predetermined range. The control device reduces the difference between the load-side impedance, which is the impedance of the circuit from the input terminal of the power transmission device to the load side, and the input-side impedance, which is the impedance of the circuit from the input terminal of the power transmission device to the power supply device side, according to the voltage amplitude or current amplitude measured by the measuring unit. [Effects of the Invention]

[0013] This invention enables low-cost, simple, and efficient wireless power transfer. [Brief explanation of the drawing]

[0014] [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 a power supply unit equipped with two switching elements. [Figure 3] This is a schematic diagram showing the configuration of a power supply unit equipped with a single switching element. [Figure 4] This is a schematic diagram showing the configuration of the measurement unit. [Figure 5] This is a circuit diagram for a wireless power transfer system. [Figure 6] This is an equivalent circuit diagram corresponding to the circuit diagram shown in Figure 7. [Figure 7] This is a schematic diagram showing the configuration of the drive coil. [Figure 8] This is a schematic diagram showing the positional relationship between the power transmission coil and the three drive coil sections, which are positioned offset in the axial direction of the coil shaft. [Figure 9] This is a schematic diagram of the experimental circuit used in an experiment that confirmed that the load-side impedance can be estimated based on the voltage amplitude across the capacitor. [Figure 10] This graph shows the relationship between the voltage amplitude across the capacitor and the load impedance. [Figure 11] This is a schematic diagram showing the configuration of the power receiving coil. [Figure 12] This is a schematic diagram showing the positional relationship between the three coil regions of the power transmission coil and the power receiving coil. [Figure 13] This graph shows the relationship between the voltage amplitude between the drain and source of a switching element and the load-side impedance. [Modes for carrying out the invention]

[0015] A wireless power supply system 1 and a wireless power supply method using the wireless power supply system 1 according to one embodiment of the present invention will be described with reference to the drawings. In the following, when referring to the number, numerical values, quantities, ranges, etc. of components, unless specifically stated or clearly limited to a particular number in principle, the number is not limited to that particular number and may be greater than or less than that number.

[0016] Furthermore, when referring to the shape, positional relationship, etc. of constituent elements, unless otherwise explicitly stated or in cases where it is clearly not the case in principle, this includes things that are substantially similar or analogous to those shapes, etc.

[0017] Furthermore, drawings may exaggerate features by enlarging characteristic parts to make them easier to understand, and the dimensional ratios of components may not be the same as in reality. Also, in cross-sectional drawings, hatching of some components may be omitted to make the cross-sectional structure of the components easier to understand.

[0018] <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 a 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. Also, at the time of power supply, the power supply target object 2 may be moving or stationary. The wireless power supply system 1 comprises a power transmission device 3, a power receiving device 4, and a power supply device 5 connected to an AC power supply 5A.

[0019] <Configuration of power transmission equipment> The power transmission device 3 comprises a drive coil 31, a power transmission coil 32, and capacitors 33 and 34.

[0020] The drive coil 31 and the 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 for the drive coil 31 and the 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.

[0021] The drive coil 31 is supplied with AC power from the AC power supply 5A of the power supply unit 5. The AC power is set to, for example, a frequency of 150kHz and a voltage of 10V, but the frequency and voltage of the AC power supply 5A can be changed arbitrarily. Hereinafter, the contact on the AC power supply 5A side of the drive coil 31 will be referred to as the "input terminal IE". In this embodiment, the case in which the drive coil 31 and the AC power supply 5A are directly connected via the input terminal IE will be explained as an example, but the drive coil 31 and the AC power supply 5A may be connected indirectly via a coaxial cable or the like provided between the AC power supply 5A and the input terminal IE, even if they are directly connected via 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.

[0022] The drive unit 35 includes a power supply side resonant circuit configured by connecting a drive coil 31 and a capacitor 33 in series. When an AC voltage with a frequency corresponding to the resonant frequency set by the inductance of the drive coil 31 and the capacitance of the capacitor 33 flows through the drive coil 31, an oscillating magnetic field is generated that penetrates the drive coil 31. The detailed configuration of the drive coil 31 will be described later.

[0023] The drive coil 31 and the transmission coil 32 are magnetically coupled, and the drive coil 31 supplies power to the transmission coil 32 using a magnetic field resonance method. Specifically, the resonant frequency set according to the inductance of the drive coil 31 and the capacitance of the capacitor 33 is approximately equal to the resonant frequency set according to the inductance of the transmission coil 32 and the capacitance of the capacitor 34, so that the drive coil 31 and the transmission coil 32 resonate together. As a result, the vibration of the magnetic field at a specific frequency (resonant frequency) generated by the flow of alternating current through the drive coil 31 is transmitted to the transmission coil 32, and when it resonates at the same specific frequency, an electromotive force is generated in the transmission coil 32. While a magnetic field resonance method is preferred for supplying power from the drive coil 31 to the 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 transmission coil 32 via the magnetic flux generated in the direction of the coil axis when alternating current flows through the drive coil 31. Furthermore, the magnetic resonance method and the electromagnetic coupling method may be used in combination.

[0024] The power transmission unit 36 ​​includes a power transmission side resonant circuit formed by connecting a power transmission coil 32 and a capacitor 34 in series. When an AC voltage with a frequency corresponding to the resonant frequency set by the inductance of the power transmission coil 32 and the capacitance of the capacitor 33 flows through the power transmission coil 32, the power receiving coil 41, described later, resonates and generates an electromotive force.

[0025] <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 comprises a power receiving coil 41 and a capacitor 42.

[0026] 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 driving coil 31 and the transmitting coil 32.

[0027] The power receiving unit 43 includes a power receiving side resonant circuit formed by connecting a power receiving coil 41 and a capacitor 42 in series. The resonant frequency set by the inductance of the power receiving coil 41 and the capacitance of the capacitor 42 is set to approximately coincide with the resonant frequency of the power transmitting coil 32 and the capacitor 33. As a result, vibrations in the magnetic field generated to penetrate the power transmitting coil 32 in the direction of the coil axis induce a current to flow in the power receiving coil 41, and an oscillating magnetic field is generated to penetrate the power receiving coil 41 in the direction of the coil axis. At this time, the magnetic fields of the power transmitting coil 32 and the power receiving coil 41 resonate and are strongly coupled. The detailed configuration of the power receiving coil 41 will be described later.

[0028] The AC power received by the 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.

[0029] 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.

[0030] 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.

[0031] The controller 92 constitutes the impedance matching mechanism 9 described later, and controls at least one of the drive unit 35 and the power reception unit 43 according to the measurement result by the measurement unit 54 of the power supply device 5. The controller 92 is composed of, for example, a CPU, a memory, etc. Note that the function of the controller 92 may be realized by controlling using software, or may be realized by operating using hardware. The controller 92 is functionally divided into a storage unit 93 and a control unit 94. The control of the drive unit 35 and the power reception unit 43 by the controller 92 will be described later.

[0032] <Configuration of Power Supply Device> As shown in FIG. 2, the power supply device 5 includes a DC conversion unit 51, a switching device 52 connected to the DC conversion unit 51, a power supply control unit 53 that controls the switching device 52, and a measurement unit 54 that measures the voltage amplitude in a predetermined region within the power supply device 5.

[0033] The DC conversion unit 51 converts the AC power input from the AC power supply 5A into DC power. In order to smooth the DC voltage output from the DC conversion unit 51, a capacitor may be arranged in parallel with the DC conversion unit 51 between the high-potential side terminal (output terminal) and the low-potential side terminal (ground terminal) of the DC conversion unit 51.

[0034] The switching device 52 is a class E amplifier and includes switching elements Q S1 , Q S2 , inductors L RF1 , L RF2 , diodes D S1 , D S2 , capacitors C Sh1 , C Sh2 , inductors L e1 , L e2 and capacitors C S1 , C S2 .

[0035] The switching element Q S1 (the first switching element), the switching element Q S2The (second switching element) receives a differential signal (for example, a square wave where one side is HIG and the other is LOW) from the power supply control unit 53 and switches between an ON state and an OFF state according to the differential signal. In this embodiment, the switching element Q S1 Q S2 A MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is used as the switching element Q. S1 Q S2 This is not limited to MOSFETs; it can also be a bipolar transistor, IGBT (Insulated Gate Bipolar Transistor), etc.

[0036] Switching Element Q S1 Between the drain terminal and the output terminal of the DC conversion unit 51, there is an inductor L RF1 The (first inductor) is connected in series, and the switching element Q S2 The drain terminal of the DC converter 51 and the output terminal of the switching element Q S2 Between the drain terminal and the inductor L RF2 The third inductor is connected in series. The DC conversion unit 51 outputs a constant DC voltage, so the inductor L RF1 is a switching element Q S1 A constant DC current is supplied to the inductor L. RF2 is a switching element Q S2 A constant DC current is supplied to it.

[0037] Switching Element Q S1 Q S2 The source terminals are each connected to ground. Switching element Q S1 Q S2 Between the drain terminal and the source terminal is a diode D, which is a so-called flywheel diode. S1 (First diode), D S2 (The second diode) is connected in antiparallel. That is, diode D S1The anode terminal of the switching element Q S1 It is connected to the source terminal, diode D S1 The cathode terminal of the switching element Q S1 It is connected to the drain terminal of diode D. S2 The anode terminal of the switching element Q S2 It is connected to the source terminal, diode D S2 The cathode terminal of the switching element Q S2 It is connected to the drain terminal of diode D. S1 , D S2 is a switching element Q S1 Q S2 The high reverse voltage caused by the back electromotive force generated by the switching of the switching element Q S1 Q S2 This suppresses the application of the switching element Q. S1 Q S2 If it has the function of operating as a diode internally, then diode D S1 , D S2 You can omit it.

[0038] Switching Element Q S1 Q S2 Control signals are input to the gate terminals of the switching element Q from the power supply control unit 53. S1 The control signal (first high-frequency control signal) input to the switching element Q S2 The control signal input to the switch element (the second high-frequency control signal) is a differential signal with opposite phases to the input signal. This differential signal is a pulse signal that alternates between high and low levels at a predetermined frequency f0 (for example, 85 kHz or 13.56 MHz). The frequency f0 is determined by the switching element Q. S1 Q S2 This is the frequency at which the switching element Q is switched, and will sometimes be referred to as "switching frequency f0" below. S1 Q S2 The switching element Q is in the off state when the input differential signal is low level and in the on state when it is high level. S1 Q S2By using differential signals for the input signals, transmission efficiency can be increased, and the device becomes more resistant to external noise, enabling stable power supply.

[0039] Capacitor C Sh1 (The first capacitor) is a switching element Q S1 Connected in parallel to, capacitor C Sh2 (The third capacitor) is a switching element Q S2 It is connected in parallel to capacitor C. Sh1 , C Sh2 is a switching element Q S1 Q S2 When it is in the off state, current flows and electrical energy is stored. Then, capacitor C Sh1 , C Sh2 After the voltage across the capacitor reaches its peak, it discharges and releases electrical energy. Then, capacitor C Sh1 , C Sh2 At the moment the voltage across the terminals becomes zero, the switching element Q S1 Q S2 It switches from the off state to the on state.

[0040] Inductor L e1 (Second inductor) and capacitor C S1 The (second capacitor) is connected in series to form a resonant circuit (the first resonant circuit). The first resonant circuit is a switching element Q S1 The drain terminal and inductor L RF1 It is connected in series between the connection point with one of its terminals and the power transmission device 3. The first resonant circuit is designed so that its resonant frequency matches the switching frequency f0.

[0041] Inductor L e2 (Fourth inductor) and capacitor C S2 The (fourth capacitor) is connected in series to form a resonant circuit (the second resonant circuit). The second resonant circuit is a switching element Q S2 The drain terminal and inductor L RF2It is connected in series between the connection point with one terminal and the power transmission device 3. The second resonance circuit is designed such that its resonance frequency matches the switching frequency f0.

[0042] In this way, the switching device 52 constitutes a class - E amplifier with extremely low switching losses, and the switching elements Q S1 、Q S2 switch according to the differential signal input from the power control unit 53, so that the power supply device 5 outputs a high - frequency current with the switching frequency f0. Note that the switching device 52 is not limited to the configuration shown in FIG. 2 as long as it constitutes a class - E amplifier, and some circuit elements may be removed or other circuit elements may be added.

[0043] Also, the switching device 52 is not limited to the configuration of inputting a differential signal to the switching elements Q S1 、Q S2 shown in FIG. 2. For example, as shown in FIG. 3, it may be composed of the switching element Q S1 (the first switching element), the diode D S1 (the first diode), the inductor L RF1 (the first inductor), and the capacitor C Sh1 (the first capacitor), the inductor L e1 (the second inductor) and the capacitor C S1 (the second capacitor). In the switching device 52 shown in FIG. 3, the source terminal of the switching element Q S1 is connected to one terminal of the DC conversion unit 51. Also, a capacitor C4 is connected to the output side of the switching device 52 in parallel with the DC conversion unit 51.

[0044] The measurement unit 54 measures the voltage across both ends of the capacitor C S1 . As shown in FIG. 4, the measurement unit 54 includes a differential amplifier circuit 541 and a rectifying and smoothing circuit 542.

[0045] The differential amplifier circuit 541 includes a register R A1, R A2 , R B1 , R B2 and is composed of an operational amplifier E1. The negative input IN1 of the differential amplifier circuit 541 is connected to the input side of the capacitor C S1 , and the positive input IN2 of the differential amplifier circuit 541 is connected to the output side of the capacitor C S1 . The differential amplifier circuit 541 amplifies the voltage difference across both ends of the capacitor C S1 and outputs it to the rectifying and smoothing circuit 542.

[0046] The rectifying and smoothing circuit 542 is composed of an operational amplifier E2, diodes D1, D2, a resistor R1, and a capacitor C1. The rectifying and smoothing circuit 532 rectifies the output from the differential amplifier circuit 541, smooths it, and sends it to the controller 92.

[0047] Note that the predetermined region in the power supply device 5 where the measurement unit 54 measures the voltage amplitude is not limited to both ends of the capacitor C S1 , and it can be anywhere in the power supply device 5 as long as it has a correlation with the load-side impedance described later. For example, it can be between the drain and source of the switching elements Q S1 , Q S2 as well.

[0048] <Configuration of the Impedance Matching Mechanism> Next, an impedance matching mechanism 9 that performs impedance matching processing to relax the difference between the impedance of the circuit on the power receiving device 4 side from the input terminal IE (i.e., the 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 (load-side circuit)) (hereinafter referred to as "load-side impedance") and the impedance of the circuit on the AC power supply 5A side from the input terminal IE (hereinafter referred to as "input-side impedance") will be described based on the drawings.

[0049] First, let's explain the factors that cause impedance mismatch, where the input impedance and the load impedance do not match. The larger the difference between the input impedance and the load impedance, the greater the power reflection and the lower the power transmission efficiency. Impedance mismatch can occur, for example, when the relative position of the transmitting coil 32 and the receiving coil 41 changes, or when foreign matter is interposed between the transmitting coil 32 and the receiving coil 41, causing a change in the coupling coefficient between the transmitting coil 32 and the receiving coil 41, or when the state of the load 8 changes due to the battery charge status, causing the load impedance to fluctuate.

[0050] Impedance mismatch will be explained in detail based on Figures 5 and 6. Figure 5 is a circuit diagram corresponding to wireless power supply system 1. In Figure 5, "V" is the voltage of the 5A power supply, and "Z" is the voltage of the 5A power supply. s " is the impedance of the 5A power supply (input impedance), "R0" is the parasitic resistance of the drive coil 31, "L0" is the inductance of the drive coil 31, "C0" is the capacitance of the capacitor 33, "I0" is the current flowing through the drive coil 31, "R1" is the parasitic resistance of the transmission coil 32, "L1" is the inductance of the transmission coil 32, "C1" is the capacitance of the capacitor 34, "I1" is the current flowing through the transmission coil 32, "k 01 " is the coupling coefficient of the drive coil 31 and the transmission coil 32, "R2" is the parasitic resistance of the 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.

[0051] Figure 6 is an equivalent circuit diagram based on the circuit diagram shown in Figure 5. The equivalent circuit diagram shown in Figure 6 shows a state in which the drive coil 31 and the transmission coil 32 are in resonance, and the transmission coil 32 and the receiving coil 41 are in resonance. Mutual inductance M between the drive coil 31 and the transmission coil 32 01 is, k 01 √(L0L1), mutual inductance M between the transmitting coil 32 and the receiving coil 41.12 is, k 12 The equation is √(L1L2). In Figure 6, "Z0" is the impedance of the circuit from the input terminal IE of the power transmission device 3 to the load 8 side (load-side impedance) between the power supply 5A and the drive coil 31. "Z1" is the impedance of the circuit from the drive coil 31 and the transmission coil 32 to the load 8 side. "Z2" is the impedance of the circuit from the receiving coil 41 to the load 8 side. From the equivalent circuit shown in Figure 6, the following equations 1 to 3 are obtained.

[0052]

number

[0053]

number

[0054]

number

[0055] For example, as the transmitting coil 32 and the receiving coil 41 approach each other, the coupling coefficient "k" between the transmitting coil 32 and the receiving coil 41 changes. 12 As the value of " increases, based on equation 2, the impedance "Z1" increases, and based on equation 3, the impedance "Z0" decreases.

[0056] Therefore, the impedance matching mechanism 9 uses a coupling coefficient "k 12 As the value of the current increases, the inductance "L2" of the receiving coil 41 is reduced. This suppresses the increase in impedance "Z1", and consequently suppresses fluctuations in impedance "Z0", thereby maintaining impedance matching.

[0057] Also, the coupling coefficient "k 12 As "k" increases, the impedance "Z1" increases, but the coupling coefficient "k" between the drive coil 31 and the transmission coil 32 increases. 01By increasing the value of "Z", the increase in impedance "Z1" can be offset, and as a result, fluctuations in impedance "Z0" can be suppressed, thus maintaining impedance matching.

[0058] Furthermore, the inductance "L2" of the receiving coil 41 and the coupling coefficient "k 01 By adjusting both of these, it is also possible to suppress fluctuations in impedance "Z0" and maintain impedance matching.

[0059] In other words, the impedance matching mechanism 9 determines the coupling coefficient "k" between the drive coil 31 and the power transmission coil 32. 01 By adjusting at least one of the inductance "L2" of the receiving coil 41 and the impedance "Z0", fluctuations in impedance "Z0" can be suppressed and impedance matching can be maintained.

[0060] Next, the coupling coefficient "k" of the drive coil 31 and the power transmission coil 32. 01 The impedance matching process, which involves adjusting the coupling strength in the magnetic field coupling between the drive coil 31 and the power transmission coil 32, will be explained with reference to Figures 7 and 8. As shown in Figure 7, the impedance matching mechanism 9 supplies power to at least one of the three drive coil sections 31A, 31B, and 31C that constitute the drive coil 31 by switching control of switches 91a to 91d by the controller 92. 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 drive coil sections 31A, 31B, and 31C.

[0061] The drive coil 31 is divided into three drive coil sections 31A, 31B, and 31C. The three drive coil sections 31A, 31B, and 31C divide the drive coil 31 into three parts and are essentially connected in series. Drive coil sections 31A and 31B are connected via wiring 31AB, and drive coil sections 31B and 31C are connected via wiring 31BC. Note that the wiring 31AB and 31BC may be omitted, and each of the drive coil sections 31A, 31B, and 31C may be composed of different drive coils. In normal conditions, the coil shafts 31a, 31b, and 31c of the drive coil sections 31A, 31B, and 31C and the coil shaft 32a of the power transmission coil 32 are located approximately coaxially. Note that the following explanation uses the case where the drive coil 31 is divided into three drive coil sections 31A, 31B, and 31C as an example, but the number of drive coil sections may be two, four or more.

[0062] The drive coils 31A, 31B, and 31C are arranged such that drive coil 31A is closest to the transmission coil 32, and the other coils are spaced further away from the transmission coil 32 in that order. Therefore, the magnetic field coupling strength with the transmission coil 32 is set to be strongest for drive coil 31A and weakest for drive coil 31C. When transmitting power between the drive coil 31 and the transmission coil 32 using a magnetic field resonance method, efficient power transmission can be achieved by setting the inductances of drive coils 31A, 31B, and 31C to be equal.

[0063] Switches 91a to 91d are switches consisting of MOSFETs or the like for supplying current to the drive coil sections 31A, 31B, and 31C. Switches 91a and 91b are connected to the power supply unit 5. Switch 91a is configured to switch between one end of the drive coil section 31C and the switch 91c side. Switch 91c is configured to switch between one end of the drive coil section 31A and one end of the drive coil section 31B. Switch 91b is configured to switch between the other end of the drive coil section 31C and the switch 91d side. Switch 91d is configured to switch between the other end of the drive coil section 31A and the other end of the drive coil section 31B.

[0064] When supplying power to the drive coil section 31A, switch 91a is switched to the switch 91c side, switch 91c is switched to one end of the drive coil section 31A, switch 91b is switched to the switch 91d side, and switch 91d is switched to the other end of the drive coil section 31A. When supplying power to the drive coil section 31B, switch 91a is switched to the switch 91c side, switch 91c is switched to one end of the drive coil section 31B, switch 91b is switched to the switch 91d side, and switch 91d is switched to the other end of the drive coil section 31B. Furthermore, when supplying power to the drive coil section 31C, switch 91a is switched to the drive coil section 31C side, and switch 91b is switched to the drive coil section 31C side.

[0065] Furthermore, when supplying power to the drive coil sections 31A and 31B, switch 91a is switched to the switch 91c side, switch 91c is switched to one end of the drive coil section 31A, switch 91b is switched to the switch 91d side, and switch 91d is switched to the other end of the drive coil section 31B. Furthermore, when supplying power to the drive coil sections 31B and 31C, switch 91a is switched to the switch 91c side, switch 91c is switched to one end of the drive coil section 31B, and switch 91b is switched to the drive coil section 31C side.

[0066] Furthermore, when supplying power to the drive coil sections 31A, 31B, and 31C, switch 91a is switched to the switch 91c side, switch 91c is switched to one end of the drive coil section 31A side, and switch 91b is switched to the drive coil section 31B side.

[0067] The magnetic field coupling strength between the drive coils 31A, 31B, and 31C and the transmission coil 32 decreases inversely proportional to the distance of the drive coils 31A, 31B, and 31C from the transmission coil 32. Therefore, as shown in Figure 8, the impedance of the circuit within the power transmission device 3 can be increased or decreased by supplying power to any of the drive coils 31A, 31B, or 31C, which have different magnetic field coupling strengths with the transmission coil 32.

[0068] Furthermore, by making the inductances "L0" of the drive coil sections 31A, 31B, and 31C shown in Figures 7 and 8 substantially equal, the resonant frequency can be kept constant without changing the capacitance "C0" of the capacitor 33. However, the present invention is not limited to this, and the inductances "L0" of the drive coil sections 31A, 31B, and 31C may be set to different values, and the capacitance "C0" of the capacitor 33 may be adjusted so that the resonant frequency is substantially constant according to the inductances "L0" of the drive coil sections 31A, 31B, and 31C that are switched and used. Furthermore, the method for adjusting the capacitance "C0" of the capacitor 33 may be to use a variable capacitor, or to provide multiple capacitors and switch between them according to the inductances "L0" of the drive coil sections 31A, 31B, and 31C that are used.

[0069] Furthermore, the coupling coefficient "k" of the drive coil 31 and the power transmission coil 32 01 The method for adjusting the coupling coefficient "k" is not limited to switching the series-connected drive coil sections 31A, 31B, and 31C shown in Figures 7 and 8. 01 Any form is acceptable as long as the "cooling" is adjustable. For example, such forms include arranging the drive coil 31 to be movable, preparing multiple coil sections with different coil diameters and switching between these coil sections, or preparing multiple coil sections with different coil inclinations and switching between these coil sections.

[0070] Switching control of switches 91a to 91d is controlled by the capacitor C measured by the measurement unit 54. S1 The controller 92 performs the following action based on the load-side impedance Z0 estimated from the voltage amplitude across both ends of the device.

[0071] Here, we will describe an experiment that confirmed that the load-side impedance Z0 can be estimated based on the voltage amplitude measured by the measurement unit 54. Figure 9 shows the experimental circuit used in this experiment, in which an impedance device 55 corresponding to the load-side impedance Z0 is placed on the output side of the power supply unit 5. In the experimental circuit shown in Figure 9, the settings for the various circuit components constituting the power supply unit 5 and the various circuit components constituting the measurement unit 54 were as follows. [Setting values ​​for various circuit components that make up the power supply unit] Inductor L RF1 , L RF2 :4.7mH Capacitor C Sh1 :4930pF Capacitor C Sh2 :4700pF Inductor L e1 , L e2 :200pH Capacitor C S1 , C S2 :8160pF [Setting values ​​for various circuit components that make up the measurement unit] • Register R A1 , R A2 :191.2kΩ • Register R B1 , R B2 :33.78kΩ • Resistor R1: 100kΩ Capacitor C1: 1μF

[0072] In this experiment, the impedance Z0 of the impedance device 55 was varied in 11 patterns within the range of 0.5Ω to 2990Ω, and the capacitor C in each pattern was measured. S1 The voltage amplitude (rectified and smoothed voltage) across both ends of the device was measured by the measurement unit 54. The measurement results are shown in Figure 10.

[0073] The graph shown in Figure 10 has the impedance Z0 of the impedance device 55 on the horizontal axis and the rectified and smoothed voltage measured by the measurement unit 54 on the vertical axis. According to Figure 10, capacitor C S1The rectified and smoothed voltage across the capacitor C decreases as the load impedance Z0 increases. S1 It can be seen that the value of the load-side impedance Z0 can be uniquely estimated from the voltage amplitude across both ends of the circuit.

[0074] Next, the procedure for selecting suitable drive coil sections 31A, 31B, and 31C in order to achieve impedance matching will be described.

[0075] First, the load-side impedance Z0 and capacitor C, which were obtained through experiments beforehand, are shown in Figure 9. S1 The correspondence between the voltage amplitudes at both ends of the device and the data is stored in the memory unit 93.

[0076] Next, the measurement unit 54 measures capacitor C S1 The voltage amplitude across the capacitor C is measured and the measured value is transmitted to the controller 92. The controller 92 takes the measured value from the measuring unit 54 and the capacitor C stored in advance. S1 The load-side impedance Z0 is uniquely estimated from the relationship between the voltage amplitudes at both ends of the circuit and the load-side impedance Z0.

[0077] The controller 92 then selects one of the drive coil sections 31A, 31B, or 31C by switching switches 91a to 91d so as to approach the estimated value of the load side impedance Z0. The method of selecting the drive coil section 31A, 31B, or 31C is determined by the coupling coefficient "k" between the drive coil 31 and the transmission coil 32 so that the theoretical value of the load side impedance Z0 shown in equation 3 approaches the estimated value of the load side impedance Z0. 01 The coupling coefficient "k" is calculated and this coupling coefficient "k 01 By selecting drive coil sections 31A, 31B, and 31C that achieve the value closest to "[ ]", impedance matching can be achieved.

[0078] Next, the impedance matching process performed by adjusting the inductance "L2" of the receiving coil 41 will be explained based on Figures 11 and 12. As shown in Figure 11, the impedance matching mechanism 9 selects which of the three coil regions 41A, 41B, and 41C of the receiving coil 41 to energize by switching control of switches 91e to 91f, which are connected to two terminals provided between the terminals on one end of the receiving coil 41 and the three receiving coil sections 41a, each divided into approximately the same number of coil turns and substantially connected in series. Capacitors 42a, 42b, and 42c are provided in series with the coil regions 41A, 41B, and 41C, and can be switched between coil region 41A and capacitor 42a, coil region 41B and capacitor 42b, or coil region 41C and capacitor 42c by switching control of switches 91e to 91f. The products of the inductance "L2" and capacitance "C2" of the coil region 41A and capacitor 42a, the coil region 41B and capacitor 42b, and the coil region 41C and capacitor 42c are set to be substantially equal in order to maintain the resonant state of the receiving coil 41. The terminal at the other end of the receiving coil 41 and the switch 91e are connected to the rectifier circuit 6. The switching control of switches 91e to 91f is controlled by the capacitor C measured by the measurement unit 54. S1 The controller 92 performs the operation according to the load-side impedance Z0 estimated based on the voltage amplitude across both ends of the coil. Note that if it is possible to select any of the coil regions 41A, 41B, or 41C, other configurations may be used instead of switches 91e to 91f. Furthermore, the following explanation uses the example of dividing the receiving coil 41 into three coil regions 41A, 41B, and 41C, but the number of receiving coil regions may be two, four or more.

[0079] Figure 12 is a schematic diagram showing how some or all of the receiving coil 41 is used selectively. Figure 12(a) illustrates the case where coil region 41A, which corresponds to the total number of turns of the receiving coil 41, is used; Figure 12(b) illustrates the case where coil region 41B, which is close to the transmitting coil 32 and corresponds to 2 / 3 of the total number of turns of the receiving coil 41, is used; and Figure 12(c) illustrates the case where coil region 41C, which is close to the transmitting coil 32 and corresponds to 1 / 3 of the total number of turns of the receiving coil 41, is used. The inductance "L2" of the receiving coil 41 increases in proportion to the number of turns of coil regions 41A, 41B, and 41C, so the inductance "L2" of coil region 41A is the largest, and the capacitance "C2" of capacitor 42a is the smallest at this time. The inductance "L2" of coil region 41B is 2 / 3 of that of coil region 41A, and the capacitance "C2" of capacitor 42b at this time is 3 / 2 of that of capacitor 42a. The inductance "L2" of coil region 41C is 1 / 3 of that of coil region 41A, and the capacitance "C2" of capacitor 42c at this time is 3 times that of capacitor 42a.

[0080] Next, we will describe the procedure for selecting suitable coil regions 41A, 41B, and 41C in order to achieve impedance matching.

[0081] First, the load-side impedance Z0 and capacitor C, which were obtained through experiments beforehand, are shown in Figure 9. S1 The correspondence between the voltage amplitudes at both ends of the device and the data is stored in the memory unit 93.

[0082] Next, the measurement unit 54 measures capacitor C S1 The voltage amplitude across the capacitor C is measured and the measured value is transmitted to the controller 92. The controller 92 takes the measured value from the measurement unit 54 and the capacitor C stored in the storage unit 93. S1 The load-side impedance Z0 is uniquely estimated from the relationship between the voltage amplitudes at both ends of the circuit and the load-side impedance Z0.

[0083] Next, the controller 92 selects one of the coil regions 41A, 41B, or 41C by switching switches 91e to 91f to approach the estimated value of the load side impedance Z0. The method for selecting coil regions 41A, 41B, or 41C is to calculate the value of the inductance "L2" of the receiving coil 41 so that the theoretical value of the load side impedance Z0 shown in equation 3 approaches the estimated value of the load side impedance Z0, and then select coil region 41A, 41B, or 41C that achieves the calculated inductance "L2" of the receiving coil 41, thereby achieving impedance matching.

[0084] When switching the drive coil 31 and the power receiving coil 41 in combination, the order in which the drive coil 31 and power receiving coil 41 are switched can be arbitrarily changed. For example, if the drive coil 31 is switched first, the drive coil sections 31A, 31B, and 31C of the drive coil 31 are switched first. Even after reaching the switching limit (for example, drive coil section 31A or 31C), if the theoretical value of the load side impedance Z0 deviates from the estimated value of the load side impedance Z0, the power receiving coil 41 is switched one stage, and then the drive coil sections 31A to 31C of the drive coil 31 are switched again in sequence. Similarly, the switching of the drive coil 31 and the power receiving coil 41 is repeated until the theoretical value of the load side impedance Z0 that is closest to the estimated value of the load side impedance Z0 is obtained. Note that the priority order of the power receiving coil 41 and the drive coil 31 may be such that the power receiving coil 41 is given priority.

[0085] Furthermore, in order to achieve impedance matching, it is not always necessary to switch the drive coil 31 and the receiving coil 41 together. It is acceptable to switch only the receiving coil 41 without switching the drive coil 31, or to switch only the drive coil 31 without switching the receiving coil 41.

[0086] Thus, the wireless power supply system 1 according to this embodiment comprises a power transmission device 3 having a power transmission side resonant circuit including a power transmission coil 32, a power receiving unit 43 having a power receiving side resonant circuit including a power receiving coil 41 with changeable inductance, a power receiving device 4 that can be connected to a load 8 to which the power received by the power receiving coil 41 is supplied, a controller 92 that controls the power receiving unit 43, and a power supply device 5 that supplies power to the power transmission coil 32, and the wireless power supply system 1 transmits and receives power between the power transmission coil 32 and the power receiving coil 41 using a magnetic field resonance method, wherein the power supply device 5 comprises a DC conversion unit 51 that outputs a DC voltage, and a first switching element Q that performs switching operation based on a first high-frequency control signal that is input. S1 The DC conversion unit 51 and the first switching element Q S1 A first inductor L is connected in series between it and RF1 And the first switching element Q S1 The first capacitor C is connected in parallel with it. Sh1 The power transmission device 3 and the first switching element Q S1 and the first inductor L RF1 An inductor L is connected in series between the connection point and the other point. e1 and capacitor C S1 The controller 92 comprises a first resonant circuit and a measuring unit 54 that measures the voltage amplitude in a predetermined range of the power supply unit 5, and the controller 92 changes the inductance "L2" of the power receiving coil 41 according to the voltage amplitude measured by the measuring unit 54, thereby changing the load side impedance Z0 and the input side impedance Z s The configuration was designed to mitigate the difference.

[0087] With this configuration, the controller 92 changes the inductance "L2" of the power receiving coil 41 according to the voltage amplitude in a predetermined range of the power supply unit 5 as a Class E amplifier, as measured by the measurement unit 54, thereby changing the load side impedance Z0 and the input side impedance Z sBecause the difference is mitigated, wireless power transfer can be performed efficiently, easily, and at low cost without the need for conventional directional couplers. Furthermore, compared to power supply and transmission equipment which are fixed installations, the adjustment is made at the receiving device installed on the moving power supply target 2, making it easy to adjust and repair various elements such as coils and capacitors in response to environmental changes and changes over time.

[0088] Furthermore, the wireless power supply system 1 according to this embodiment comprises a power transmission device 3 having a power transmission side resonant circuit including a power transmission coil 32 and a drive unit 35 having a drive coil 31 that is magnetically coupled to the power transmission coil 32 and transmits power to the power transmission coil 32 by magnetic field resonance; a power receiving device 4 having a power receiving side resonant circuit including a power receiving coil 41 and being connectable to a load 8 to which the power received by the power receiving coil 41 is supplied; a controller 92 that controls the drive unit 35; and a power supply device 5 that supplies power to the power transmission coil 32. The wireless power supply system 1 transmits and receives power between the power transmission coil 32 and the power receiving coil 41 using a magnetic field resonance method, wherein the power supply device 5 includes a DC conversion unit 51 that outputs a DC voltage and a first switching element Q that performs switching operation based on a first high-frequency control signal input. S1 The DC conversion unit 51 and the first switching element Q S1 A first inductor L is connected in series between it and RF1 And the first switching element Q S1 The first capacitor C is connected in parallel with it. Sh1 The power transmission device 3 and the first switching element Q S1 and the first inductor L RF1 An inductor L is connected in series between the connection point and the other point. e1 and capacitor C S1 The controller 92 comprises a first resonant circuit and a measuring unit 54 that measures the voltage amplitude in a predetermined range of the power supply unit 5, and the controller 92 measures the coupling coefficient "k" which is the coupling strength in the magnetic field coupling between the drive coil 31 and the power transmission coil 32, according to the voltage amplitude measured by the measuring unit 54. 01 By changing ", the load side impedance Z0 and the input side impedance Z sThe configuration was designed to mitigate the difference.

[0089] With this configuration, the controller 92 adjusts the coupling coefficient "k" between the drive coil 31 and the power transmission coil 32 according to the voltage amplitude in a predetermined range of the power supply device 5 as a Class E amplifier, as measured by the measurement unit 54. 01 By changing ", the load side impedance Z0 and the input side impedance Z s Because the difference is mitigated, wireless power transfer can be performed efficiently, simply, and at low cost without the need for conventional directional couplers. Furthermore, since the control is performed on fixed power supply and transmission equipment, it is less susceptible to external disturbances, improving durability.

[0090] Furthermore, the wireless power supply system 1 according to this embodiment comprises a power transmission device 3 having a power transmission side resonant circuit including a power transmission coil 32 and a drive unit 35 having a drive coil 31 that is magnetically coupled to the power transmission coil 32 and transmits power to the power transmission coil 32 by magnetic field resonance; a power receiving device 4 having a power receiving side resonant circuit including a power receiving coil 41 with changeable inductance, and which can be connected to a load 8 to which the power received by the power receiving coil 41 is supplied; a controller 92 that controls the drive unit 35 and the power receiving unit 43; and a power supply device 5 that supplies power to the power transmission coil 32. The wireless power supply system 1 transmits and receives power between the power transmission coil 32 and the power receiving coil 41 using a magnetic field resonance method, wherein the power supply device 5 includes a DC conversion unit 51 that outputs a DC voltage and a first switching element Q that performs switching operation based on a first high-frequency control signal that is input. S1 The DC conversion unit 51 and the first switching element Q S1 A first inductor L is connected in series between it and RF1 And the first switching element Q S1 The first capacitor C is connected in parallel with it. Sh1 The power transmission device 3 and the first switching element Q S1 and the first inductor L RF1 An inductor L is connected in series between the connection point and the other point. e1 and capacitor C S1The controller 92 comprises a first resonant circuit and a measuring unit 54 that measures the voltage amplitude in a predetermined range of the power supply unit 5. The controller 92 changes the inductance "L2" of the power receiving coil 41 according to the voltage amplitude measured by the measuring unit 54, and also changes the coupling coefficient "k", which is the coupling strength in the magnetic field coupling between the drive coil 31 and the power transmitting coil 32. 01 By changing ", the load side impedance Z0 and the input side impedance Z s The configuration was designed to mitigate the difference.

[0091] With this configuration, the controller 92 adjusts the inductance "L2" of the receiving coil 41 and the coupling coefficient "k" of the drive coil 31 and the transmitting coil 32 according to the voltage amplitude in a predetermined range of the power supply device 5 as a Class E amplifier, as measured by the measurement unit 54. 01 By changing this, the load side impedance Z0 and the input side impedance Z s Because the difference is mitigated, wireless power transfer can be performed efficiently, simply, and at low cost without the need for conventional directional couplers. Furthermore, the adjustment range for impedance adjustment can be expanded, or impedance adjustment can be performed with high precision.

[0092] Furthermore, in the wireless power supply system 1 according to this embodiment, the controller 92 changes the inductance "L2" of the power receiving coil 41 based on the correspondence between the voltage amplitude measured by the measurement unit 54 and the load-side impedance Z0, which is stored in advance.

[0093] With this configuration, the measurement unit 54 estimates the load-side impedance Z0 based on the relationship between the measured voltage amplitude and the voltage amplitude and the load-side impedance Z0. The inductance "L2" of the receiving coil 41 is then adjusted so that the estimated value of the load-side impedance Z0 approaches the theoretical value of the load-side impedance Z0. This allows for smooth and quick impedance matching.

[0094] Furthermore, in the wireless power supply system 1 according to this embodiment, the controller 92 determines the coupling coefficient "k" between the drive coil 31 and the power transmission coil 32 based on the correspondence between the voltage amplitude measured by the measurement unit 54 and the load side impedance Z0, which is stored in advance. 01 The configuration was changed to modify the "

[0095] With this configuration, the measurement unit 54 estimates the load-side impedance Z0 based on the relationship between the measured voltage amplitude and the voltage amplitude and the load-side impedance Z0, and adjusts the coupling coefficient "k" between the drive coil 31 and the transmission coil 32 so that the estimated value of the load-side impedance Z0 approaches the theoretical value of the load-side impedance Z0. 01 Because this is adjusted, impedance matching can be achieved smoothly and quickly.

[0096] <Variation> Next, modifications of this embodiment will be described. Note that, apart from the configurations described below, the various modifications are the same as those of the embodiment described above.

[0097] In the embodiment described above, the measurement unit 54 is capacitor C S1 Using an experimental circuit that measures the voltage amplitude across both ends, the load side impedance Z0 and capacitor C were measured. S1 The case where the correspondence with the voltage amplitude at both ends is obtained has been explained, but the predetermined region of the power supply 5 in which the measurement unit 54 measures the voltage amplitude can be any location within the power supply 5 as long as a correlation with the load side impedance Z0 is observed. Below, as a modified example, the measurement unit 54 is found to be a switching element Q S1 This section describes how to measure the voltage amplitude between the drain and source of a device.

[0098] In the experimental circuit shown in Figure 9, when the impedance Z0 of the impedance device 55 was varied in 11 patterns within the range of 0.5Ω to 2990Ω, the measurement unit 54 measured the switching element Q for each pattern. S1 Figure 13 shows the voltage amplitude (rectified and smoothed voltage) between the drain and source.

[0099] In the graph shown in Figure 13, the horizontal axis represents the load-side impedance Z0, and the vertical axis represents the rectified and smoothed voltage measured by the measurement unit 54. According to Figure 13, the switching element Q S1 The rectified and smoothed voltage between the drain and source of the switch element Q decreases as the load impedance Z0 increases, up to around 100Ω. S1 It can be seen that the load-side impedance Z0 can be uniquely estimated from the voltage amplitude between the drain and source. Therefore, if the load-side impedance Z0 fluctuates in the range of 0 to approximately 100 Ω, impedance matching can be achieved by switching the drive coil 31 and switching the power receiving coil 41 based on the estimated value of the load-side impedance Z0, in the same manner as in the embodiment described above.

[0100] On the other hand, according to Figure 13, when the load-side impedance Z0 fluctuates beyond approximately 100 Ω, the switching element Q S1 It can be seen that there are multiple load-side impedances Z0 estimated from the rectified and smoothed voltage between the drain and source. Therefore, when the load-side impedance Z0 fluctuates beyond approximately 100Ω, the switching element Q with respect to the load-side impedance Z0 S1 By calculating and considering the changes in the voltage amplitude between the drain and source (for example, the derivative value of the graph in Figure 13), one load-side impedance Z0 can be estimated in the same manner as in the embodiment described above. Based on this estimated value, impedance matching can be achieved by switching the drive coil 31 and switching the power receiving coil 41.

[0101] In addition, the points measured by the measurement unit 54 in the present invention may be other than the voltage amplitude across the capacitor CS1 in the first embodiment and the voltage amplitude between the drain and source of the modified switching element QS1. For example, the inductor L e1 (Second inductor) and capacitor C Sh1 The voltage amplitude across the first capacitor may also be measured. Furthermore, the switching element Q at the moment the Class E amplifier is switched is also measured.S1 It can also be the drain-source voltage.

[0102] Furthermore, the measurement unit 54 may also measure the current amplitude of the power supply unit 5 in a predetermined range where a correlation with the load-side impedance Z0 is observed. For example, capacitor C S1 You may also measure the current amplitude downstream of the current.

[0103] Furthermore, the impedance matching method of the present invention is not limited to changing the inductance value of the receiving coil 41 or changing the coupling strength in the magnetic field coupling between the driving coil 31 and the transmitting coil 32 in the above-described embodiment, but may also be, for example, changing the inductance value of the driving coil 31 or changing the inductance value of the transmitting coil 32.

[0104] Furthermore, the present invention can be modified in various ways other than those described above, as long as it does not depart from the spirit of the invention, and it goes without saying that the present invention extends to such modifications. In addition, the embodiments and modifications described above may be combined with each other. [Explanation of symbols]

[0105] 1: Wireless power supply system, 2: Power supply target, 3: Power transmission device, 31: Drive coil, 31A~31F: Drive coil section, 31a~31c: Coil shaft (of the drive coil), 32: Power transmission coil, 32a: Coil shaft (of the power transmission coil), 35: Drive unit, 36: Power transmission unit, 4: Power receiving device, 41: Power receiving coil, 41A~41C: Coil area, 43: Power receiving unit, 5: Power supply device, 5A: AC power supply, 51: DC conversion unit, 52: Switching device, 53: Power control unit, 54: Measurement unit, 541: Differential amplifier circuit, 542: Rectifier and smoothing circuit, 55: Impedance device, 8: Load, 9: Impedance matching mechanism, 91a~91f: Switch, 92: Controller (control device), 93: Memory unit, 94: Control unit

Claims

1. A power transmission device equipped with a power transmission side resonant circuit including a power transmission coil, A power receiving device comprising a power receiving section having a power receiving side resonant circuit including a power receiving coil, and which can be connected to a load to which the power received by the power receiving coil is supplied, A control device for controlling the power receiving unit, A power supply device that supplies power to the aforementioned transmission coil, A wireless power supply system comprising the power supply device, which transmits and receives power between the transmitting coil and the receiving coil using a magnetic resonance method, The aforementioned power supply device is A DC conversion unit that outputs a DC voltage, A first switching element that performs switching operations based on a first high-frequency control signal input, A first inductor is connected in series between the DC conversion unit and the first switching element, A first capacitor connected in parallel with the first switching element, A first resonant circuit is connected in series between the power transmission device and the connection point of the first switching element and the first inductor, A measuring unit for measuring the voltage amplitude or current amplitude in a predetermined range of the power supply device, Equipped with, The wireless power supply system is characterized in that the control device reduces the difference between the load-side impedance, which is the impedance of the circuit from the input terminal of the power transmission device to the load-side, and the input-side impedance, which is the impedance of the circuit from the input terminal of the power transmission device to the power supply device-side, according to the voltage amplitude or current amplitude measured by the measuring unit.

2. The power receiving coil is configured to have a changeable inductance. The wireless power supply system according to claim 1, characterized in that the control device reduces the difference between the load-side impedance and the input-side impedance by changing the inductance of the power receiving coil.

3. The power transmission device further comprises a drive unit having a drive coil that is magnetically coupled to the power transmission coil and transmits power to the power transmission coil by magnetic resonance. The wireless power supply system according to claim 1, characterized in that the control device reduces the difference between the load-side impedance and the input-side impedance by changing the coupling strength in the magnetic field coupling between the power transmission coil and the drive coil.

4. The power receiving coil is configured to have a changeable inductance. The power transmission device further comprises a drive unit having a drive coil that is magnetically coupled to the power transmission coil and transmits power to the power transmission coil by magnetic resonance. The wireless power supply system according to claim 1, characterized in that the control device reduces the difference between the load side impedance and the input side impedance by changing the inductance of the receiving coil and changing the coupling strength in the magnetic field coupling between the transmitting coil and the driving coil.

5. The wireless power supply system according to claim 2 or 4, characterized in that the control device changes the inductance of the power receiving coil based on a pre-stored correspondence between the voltage amplitude and the load-side impedance.

6. The wireless power supply system according to claim 3 or 4, characterized in that the control device changes the coupling strength in the magnetic field coupling between the power transmission coil and the drive coil based on a pre-stored correspondence between the voltage amplitude and the load-side impedance.

7. The first resonant circuit further comprises a second inductor and a second capacitor connected in series at the connection point between the first switching element and the first inductor. The wireless power supply system according to any one of claims 1 to 4, characterized in that the measuring unit measures the voltage amplitude across the second capacitor as the voltage amplitude.

8. The wireless power supply system according to any one of claims 1 to 3, characterized in that the measuring unit measures the voltage amplitude between the drain and source of the first switching element as the voltage amplitude.

9. The aforementioned power supply device is A second switching element that performs switching operations based on a second high-frequency control signal input, A third inductor is connected in series between the DC conversion unit and the second switching element, A third capacitor connected in parallel with the second switching element, A second resonant circuit is connected in series between the power transmission device and the connection point of the second switching element and the third inductor, Furthermore, The wireless power supply system according to any one of claims 1 to 4, characterized in that the first high-frequency control signal and the second high-frequency control signal are differential signals.

10. A power transmission device equipped with a power transmission side resonant circuit including a power transmission coil, A power receiving device comprising a power receiving section having a power receiving side resonant circuit including a power receiving coil, and which can be connected to a load to which the power received by the power receiving coil is supplied, A control device for controlling the power receiving unit, A power supply device that supplies power to the aforementioned transmission coil, A wireless power supply method using a wireless power supply system that includes a power supply device and transmits and receives power between the transmitting coil and the receiving coil using a magnetic field resonance method, wherein the power supplied from the power supply device is transmitted and received between the transmitting coil and the receiving coil, The aforementioned power supply device is A DC conversion unit that outputs a DC voltage, A first switching element that performs switching operations based on a first high-frequency control signal input, A first inductor is connected in series between the DC conversion unit and the first switching element, A first capacitor connected in parallel with the first switching element, A first resonant circuit is connected in series between the power transmission device and the connection point of the first switching element and the first inductor, A measuring unit for measuring the voltage amplitude or current amplitude in a predetermined range of the power supply device, Equipped with, The wireless power supply method is characterized in that the control device reduces the difference between the load-side impedance, which is the impedance of the circuit from the input terminal of the power transmission device to the load-side, and the input-side impedance, which is the impedance of the circuit from the input terminal of the power transmission device to the power supply device-side, according to the voltage amplitude or current amplitude measured by the measuring unit.

11. The power receiving coil is configured to have a changeable inductance. The wireless power supply method according to claim 10, characterized in that the control device reduces the difference between the load-side impedance and the input-side impedance by changing the inductance of the power receiving coil.

12. The power transmission device further comprises a drive unit having a drive coil that is magnetically coupled to the power transmission coil and transmits power to the power transmission coil by magnetic resonance. The wireless power supply method according to claim 10, characterized in that the control device reduces the difference between the load-side impedance and the input-side impedance by changing the coupling strength in the magnetic field coupling between the power transmission coil and the drive coil.

13. The power receiving coil is configured to have a changeable inductance. The power transmission device further comprises a drive unit having a drive coil that is magnetically coupled to the power transmission coil and transmits power to the power transmission coil by magnetic resonance. The wireless power supply method according to claim 10, characterized in that the control device reduces the difference between the load side impedance and the input side impedance by changing the inductance of the receiving coil and changing the coupling strength in the magnetic field coupling between the transmitting coil and the driving coil.

14. The wireless power supply method according to claim 11 or 13, characterized in that the control device changes the inductance of the power receiving coil based on a pre-stored correspondence between the voltage amplitude and the load side impedance.

15. The wireless power supply method according to claim 12 or 13, characterized in that the control device changes the coupling strength in the magnetic field coupling between the power transmission coil and the drive coil based on a pre-stored correspondence between the voltage amplitude and the load-side impedance.

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