Wireless power supply system and method

Abstract

To provide a wireless power supply system that can stably transmit and receive power by accurately grasping a positional relation between a power supply device and a power supplied device without impairing the mobility of a moving body on which the power supplied device is mounted.SOLUTION: A wireless power supply system 1 that transmits power through magnetic field resonance method includes power supply devices 2a-2c, each having a power transmission coil 21, a power supplied device 3, which is provided with a power receiving coil 31 that receives AC power of a first frequency from the power transmission coil 21, and with a power transmission circuit 37 that outputs AC signals of a second frequency different from the first frequency, multiple antenna coils 65a-65c that are provided in the vicinity of the multiple power transmission coils 21 correspondingly to the respective power transmission coils 21 and receive AC signals output from the power transmission circuit 37, multiple signal detection circuits 62a-62c that detect AC signals respectively received by the multiple antenna coils 65a-65c, and a controller 64 that controls power supplied to the multiple power transmission coils 21 based on AC signals detected by the multiple signal detection circuits 62a-62c.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] In recent years, research and development has been progressing on wireless power transfer systems that use magnetic resonance coupling (magnetic resonance). Magnetic resonance coupling refers to a state in which magnetic field vibrations generated by the flow of AC current through the resonant circuit of a power transfer device are transmitted to the resonant circuit of a powered device, causing resonance, resulting in a strong coupling of the magnetic fields generated by the coils of each resonant circuit. Wireless power transfer using magnetic resonance coupling has the advantage of longer power transfer distances compared to wireless power transfer using conventional electromagnetic induction (magnetic coupling).

[0003] Patent Document 1 discloses a configuration in which a large number of power supply coils L1 are arranged in a matrix to transmit power from a power supply coil L1 to a resonance coil L2 and to allow flexibility in the placement of a power-supplied device 200. Patent Document 1 also discloses a configuration in which an oscillator circuit 203 drives a coil L3 at a predetermined frequency to drive only the necessary power supply coil L1 and reduce the power consumption of the power supply coil L1, and a resonance coil L0b that is physically closest to the coil L3 detects a signal from the power-supplied device 200, thereby detecting the position of the power-supplied device 200. Note that the reference symbols are those described in Patent Document 1. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-149168 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the above-mentioned coil L3 is provided in the power-supplied device 200, the weight increases by the amount of the coil L3 and the size of the device increases, so when the power-supplied device 200 is mounted on a moving body such as an AGV (Automatic Guided Vehicle), there is a problem that the mobility of the moving body deteriorates.

[0006] Furthermore, there is a risk of interference occurring between the resonant coil L2 and the coil L3, so there is a problem in that mounting both the resonant coil L2 and the coil L3 in the power-supplied device 200 is not practical.

[0007] Therefore, a technical problem arises that must be solved in order to transmit and receive power stably without impairing the mobility of a mobile body equipped with a power-supplied device and accurately grasp the positional relationship between the power supply device and the power-supplied device, and the present invention aims to solve this problem. [Means for solving the problem]

[0008] In order to achieve the above object, a wireless power feeding system according to the present invention is a wireless power feeding system that transmits and receives power using magnetism, and includes: a plurality of power feeding devices each including a power transmitting coil; a power receiving coil that receives AC power of a first frequency from the power transmitting coil; and a transmitting circuit that outputs an AC signal of a second frequency that is different from the first frequency; and a power receiving device that is provided near the plurality of power transmitting coils and corresponding to each of the power transmitting coils, and via the receiving coil The output Second frequency The power transmission device includes a plurality of antenna coils that receive AC signals, a plurality of signal detection circuits that detect the AC signals received by the plurality of antenna coils, and a controller that controls the power supplied to the plurality of power transmission coils based on the AC signals detected by the plurality of signal detection circuits.

[0009] In order to achieve the above object, a wireless power feeding method according to the present invention is a wireless power feeding method using a wireless power feeding system that transmits and receives power using magnetism, the wireless power feeding system including: a plurality of power feeding devices each including a power transmitting coil; a power receiving coil that receives AC power of a first frequency from the power transmitting coil; and a transmitting circuit that outputs an AC signal of a second frequency that is different from the first frequency; and a transmitting circuit that is provided near the plurality of power transmitting coils and corresponding to each of the power transmitting coils, via the receiving coil The output Second frequency The power supply device includes a plurality of antenna coils that receive AC signals, a plurality of signal detection circuits that detect the AC signals received by the plurality of antenna coils, and a controller that controls the power supplied to the plurality of power supply devices, and the controller controls the power supplied to the plurality of power transmission coils based on the AC signals detected by the plurality of signal detection circuits. [Effects of the Invention]

[0010] The present invention makes it possible to stably detect the position of a power-supplied device and stably transmit and receive power to and from the power-supplied device without impairing the mobility of a mobile body on which the power-supplied device is mounted. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram illustrating an overview of a wireless power supply system according to the present invention. [Figure 2] 1 is a schematic diagram illustrating a configuration of a wireless power supply system according to a first embodiment of the present invention. [Figure 3] FIG. 10 is a schematic diagram illustrating the configuration of a wireless power supply system according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] (First embodiment) A wireless power supply system 1 according to a first embodiment of the present invention will be described with reference to the drawings. Note that, hereinafter, when referring to the number, numerical value, amount, range, etc. of components, unless otherwise specified or when it is clearly limited to a specific number in principle, the number is not limited to that specific number and may be more or less than the specific number.

[0013] Furthermore, when referring to the shape or positional relationship of components, etc., it includes things that are substantially similar or approximate to those shapes, etc., unless otherwise specified or when it is clearly considered otherwise in principle.

[0014] In addition, the drawings may exaggerate characteristic parts to make the features easier to understand, and the dimensional proportions of the components may not be the same as in reality. In addition, in cross-sectional views, hatching of some components may be omitted to make the cross-sectional structure of the components easier to understand.

[0015] <Wireless power supply system configuration> Fig. 1 is a schematic diagram showing an overview of a wireless power supply system 1. Fig. 2 is a schematic diagram showing the configuration of the wireless power supply system 1. The wireless power supply system 1 includes a power supply device 2 and a power-supplied device 3, and supplies power from the power supply device 2 to the power-supplied device 3 in a contactless manner by utilizing magnetic field resonant coupling (magnetic field resonance).

[0016] Three power supply devices 2 are arranged in a row above a moving body 4 carrying a power-supplied device 3. An AC power source 5 connected to each power supply device 2 supplies AC power to the power supply devices 2. The AC power is set to, for example, a frequency of 150 kHz and a voltage of 10 V, but the frequency and voltage of the AC power source 5 can be changed as desired.

[0017] The moving object 4 is a robotic flying object or the like that floats within a specified space and can move using the AC power received by the powered device 3, but is not limited to this and may be, for example, a vehicle, an underwater robot, a capsule endoscope, a cardiac pacemaker, etc.

[0018] The wireless power supply system 1 also includes a position estimation device 6 that drives only the power supply device 2 that is closest to the power-supplied device 3 among the above-mentioned multiple power supply devices 2, and does not drive the other power supply devices 2, thereby reducing the power consumption of the power supply devices 2. The configuration of the position estimation device 6 will be described later.

[0019] In the following description, the three power supply devices 2 are distinguished from one another by adding the suffixes a to c to their reference numerals. Similarly, the various components corresponding to the power supply devices 2a to 2c are also designated by the suffixes a to c.

[0020] <Configuration of power supply device> 2, the power supply device 2a includes a power transmission coil 21a and a capacitor 22a. The power transmission coil 21a and the capacitor 22a are connected in series to form a power supply-side resonant circuit 23a. When an AC voltage having a frequency corresponding to the resonant frequency of the power supply-side resonant circuit 23a, which is set by the inductance of the power transmission coil 21a and the capacitance of the capacitor 22a, flows through the power transmission coil 21a, an oscillating magnetic field is generated that penetrates the power transmission coil 21a in the coil axis direction.

[0021] Similarly, the power supply device 2b includes a power supply side resonant circuit 23b formed by connecting a power transmission coil 21b and a capacitor 22b in series, and when an AC voltage having a frequency corresponding to the resonant frequency of the power supply side resonant circuit 23b, which is set by the inductance of the power transmission coil 21b and the capacitance of the capacitor 22b, flows through the power transmission coil 21b, an oscillating magnetic field is generated that penetrates the power transmission coil 21b in the coil axis direction.

[0022] The power supply device 2c also includes a power supply side resonant circuit 23c formed by connecting a power transmission coil 21c and a capacitor 22c in series. When an AC voltage having a frequency corresponding to the resonant frequency of the power supply side resonant circuit 23c, which is set by the inductance of the power transmission coil 21c and the capacitance of the capacitor 22c, flows through the power transmission coil 21c, an oscillating magnetic field is generated that penetrates the power transmission coil 21c in the coil axis direction.

[0023] The power transmission coils 21a to 21c are formed by circularly winding copper wire or the like, which has high electrical conductivity. 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, which is made by twisting together multiple copper wires, is used as the wire material for the power transmission coils 21a to 21c, the surface area of ​​the litz wire is larger than that of a single copper wire of the same diameter, allowing more current to flow and suppressing current loss.

[0024] A switch 24a is connected in series to the power supply side resonant circuit 23a. A switch 24b is connected in series to the power supply side resonant circuit 23b, and a switch 24c is connected in series to the power supply side resonant circuit 23c. The opening and closing of the switches 24a to 24c is controlled by a controller 64, which will be described later.

[0025] <Configuration of powered device> As shown in FIG. 2, the power-supplied device 3 includes a power-receiving coil 31 and a capacitor 32.

[0026] The power receiving coil 31 and capacitor 32 are connected in series to form a power receiving-side resonant circuit 33. The resonant frequency of the power receiving-side resonant circuit 33, which is set by the inductance of the power receiving coil 31 and the capacitance of the capacitor 32, is set to match the resonant frequency of the power feeding-side resonant circuits 23a to 23c. As a result, an induced current flows in the power receiving coil 31 due to oscillation of the magnetic field that penetrates the power transmitting coil 21 in the coil axis direction, generating an oscillating magnetic field that penetrates the power receiving coil 31 in the coil axis direction, and the magnetic fields of the power transmitting coils 21a to 21c and the power receiving coil 31 resonate and are strongly coupled together.

[0027] The power receiving coil 31 is formed by winding a copper wire or the like having high electrical conductivity in a circular shape. As with the power transmitting coil 21, the power receiving coil 31 also preferably uses a Litz wire as the wire material.

[0028] The AC power received by the power receiving coil 31 through resonance is supplied to a load 41 via a rectifier circuit 34. The load 41 is a motor, a battery, or the like that constitutes the moving object 4.

[0029] The rectifier circuit 34 is a diode bridge circuit formed by arranging four diodes 35 on a bridge, and performs full-wave rectification on the AC power received by the power receiving coil 31 to output a DC voltage. The DC voltage output by the rectifier circuit 34 is smoothed by a capacitor 36. Note that the rectifier circuit 34 is not limited to the diode bridge circuit shown in the figure.

[0030] The power supplied device 3 includes a transmitting circuit 37. The transmitting circuit 37 is driven by the power output from the rectifier circuit 34, and outputs an AC signal of a predetermined frequency to the power receiving coil 31. The AC signal output from the transmitting circuit 37 is transmitted from the power receiving coil 31 to the power supply devices 2a to 2c.

[0031] <Configuration of location estimation device> The position estimation device 6 can estimate the relative position of the power supplied device 3 (power receiving coil 31) with respect to the power supply devices 2a to 2c. As shown in Fig. 2, the position estimation device 6 includes filter circuits 61a to 61c, signal detection circuits 62a to 62c, a position estimation unit 63, and a controller 64.

[0032] The filter circuits 61a to 61c are connected to the power transmitting coils 21a to 21c, respectively. The filter circuit 61a separates the AC power mixed in the power feeding side resonant circuit 23a from the AC signal received by the power transmitting coil 21a to extract the AC signal. Similarly, the filter circuit 61b separates the AC power mixed in the power feeding side resonant circuit 23b from the AC signal received by the power transmitting coil 21b to extract the AC signal, and the filter circuit 61c separates the AC power mixed in the power feeding side resonant circuit 23c from the AC signal received by the power transmitting coil 21c to extract the AC signal.

[0033] That is, the AC power generated by the power transmitting coils 21a to 21c and the AC signals output by the transmitting circuit 37 and received by the power transmitting coils 21a to 21c are supplied to the AC power supply 5 side of the power transmitting coils 21a to 21c in a mixed state, making it difficult to accurately extract only the AC signals. Therefore, the filter circuits 61a to 61c provided on the AC power supply 5 side of the power transmitting coils 21a to 21c separate the AC power generated by the power transmitting coils 21a to 21c from the AC signals output by the transmitting circuit 37 and received by the power transmitting coils 21a to 21c, thereby allowing only the AC signals received by the power transmitting coils 21a to 21c to pass.

[0034] The signal detection circuits 62a to 62c are connected to the filter circuits 61a to 61c, respectively. The signal detection circuit 62a detects the intensity of the AC signal extracted by the filter circuit 61a. Similarly, the signal detection circuit 62b detects the intensity of the AC signal extracted by the filter circuit 61b, and the signal detection circuit 62c detects the intensity of the AC signal extracted by the filter circuit 61c. The signal detection circuits 62a to 62c are each driven by an independent DC power supply (not shown).

[0035] The position estimation unit 63 estimates the position of the power supplied device 3 (power receiving coil 31) relative to the power supply devices 2a to 2c based on the strength of the AC signals detected by the signal detection circuits 62a to 62c. The controller 64 controls the on / off of the switches 24a to 24c, turning on the switch 24a to 24c corresponding to the position of the power supplied device 3 (power receiving coil 31) and turning off the other switches 24a to 24c.

[0036] Next, the operation of the wireless power supply system 1 will be described with reference to the drawings.

[0037] <Initial power transmission> First, when AC power is sequentially supplied to all or at least one of the three power transmitting coils 21, when current is applied to the power transmitting coil 21 closest to the power supplied device 3, an oscillating magnetic field is generated that penetrates the power transmitting coil 21 in the coil axial direction. Furthermore, the oscillation of the magnetic field causes an induced current to flow in the power receiving coil 31, generating an oscillating magnetic field that penetrates the power receiving coil 31 in the coil axial direction. In this way, the magnetic fields of the power transmitting coil 21 and the power receiving coil 31 that are applied with current resonate and are strongly coupled, and AC power of a first frequency (for example, 150 kHz) is transmitted from the power transmitting coil 21 to the power receiving coil 31.

[0038] The AC power supplied from the power supplying device 2 to the power supplied device 3 in the initial power transmission may be small enough to drive the transmitting circuit 37.

[0039] <Signal Transmission> Next, the power receiving coil 31 receives power and the DC voltage is rectified by the rectifier circuit 34, which drives the transmitting circuit 37. The transmitting circuit 37 outputs a weak AC signal to the power receiving coil 31.

[0040] The frequency of the AC signal output by the oscillation circuit 37 is set to a second frequency (for example, several thousand kHz) that is different from the first frequency and its harmonics, in order to prevent the AC signal from interfering with the AC power.

[0041] The second frequency is preferably set to a frequency that exceeds the frequency band that the rectifier circuit 34 can drive, or a frequency at which the rectification efficiency of the rectifier circuit 34 is equal to or less than a predetermined ratio (for example, 1 / 10). In particular, when a diode bridge circuit is used as the rectifier circuit 34, the second frequency is preferably set to a frequency that exceeds the response frequency of the diode 35, or a frequency at which the output of the diode 35 is lower than a predetermined threshold value of the DC characteristics (for example, 1 / 10).

[0042] <Position estimation> When the AC signal propagates from the power receiving coil 31 to the power feeding devices 2a-2c, and the power transmitting coils 21a-21c, which are in magnetic field resonance with the power receiving coil 31, receive the AC signal of the second frequency transmitted from the power receiving coil 31, the filter circuits 61a-61c block the AC power of the first frequency present in the power feeding side resonant circuits 23a-23c and pass the AC signal of the second frequency. Then, the signal detection circuits 62a-62c detect the intensity of the AC signal that has passed through the filter circuits 61a-61c.

[0043] Next, the position estimation unit 63 estimates the power supply device 2a to 2c that is closest to the power receiving coil 31 according to the strength of the AC signal detected by the signal detection circuits 62a to 62c, respectively. Specifically, the position estimation unit 63 compares the strength of the AC signal detected by the signal detection circuits 62a to 62c, respectively, and estimates that the power supply device 2 corresponding to the signal detection circuit 62a to 62c that received the AC signal with the strongest strength is closest to the power receiving coil 31.

[0044] 2, the power supplied device 3 (power receiving coil 31) is located closest to the power supply device 2b. Therefore, the power receiving coil 31 and the power transmitting coil 21b undergo magnetic field resonance, and the AC signal transmitted from the power receiving coil 31 is received by the power transmitting coil 21b with a strong intensity.

[0045] On the other hand, the power supplied device 3 (power receiving coil 31) is positioned offset from the power supply devices 2a and 2c in the radial direction of the coil, and the distance between the power supply devices 2a and 2c and the power receiving coil 31 is greater than the distance between the power supply device 2b and the power receiving coil 31. Therefore, the power receiving coil 31 and the power transmitting coils 21a and 21c do not resonate magnetically or resonate very weakly, and the AC signal transmitted from the power receiving coil 31 is not received by the power transmitting coils 21a and 21c or is received with very weak strength.

[0046] In the following, as described above, the case where the power supply device 2b is closest to the power receiving coil 31 will be described as an example.

[0047] Then, the controller 64 turns on the switch 24b corresponding to the power supply device 2b that the position estimation unit 63 has selected as the closest to the power receiving coil 31, and turns off the switches 24a and 24c corresponding to the other power supply devices 2a and 2c.

[0048] <Main Power Transmission> The magnetic fields of the energized power transmitting coil 21b and power receiving coil 31 resonate and are strongly coupled, and AC power of the first frequency is transmitted from the power transmitting coil 21b to the power receiving coil 31 efficiently.

[0049] Preferably, the initial power transmission from the power transmitting coil 21 to the power receiving coil 31 is performed at a predetermined cycle (for example, every 5 seconds). This allows the power supply device 2 closest to the power receiving coil 31 to be selected in real time so as to follow the movement of the mobile object 4, even when the mobile object 4 is moving.

[0050] For example, when the power supplied device 3 moves from the vicinity of the power supply device 2b to the vicinity of the power supply device 2c as the moving object 4 moves, the intensity of the AC signal detected by the signal detection circuit 62b gradually decreases, while the intensity of the AC signal detected by the signal detection circuit 62c gradually increases. If the controller 64 turns off the switch 24b and turns on the switch 24c at the timing when the intensity of the AC signal reverses, power can be supplied to the power supplied device 3 without interruption, and the most efficient power transmission can be achieved. Note that by turning on both the switches 24b and 24c around the timing when the intensity of the AC signal reverses, the stability of power transmission can be further improved.

[0051] In this way, the wireless power supply system 1 of this embodiment is a wireless power supply system 1 that transmits power using a magnetic field resonance method, and is configured to include power supply devices 2a to 2c each having a power transmission coil 21, a power receiving coil 31 that receives AC power of a first frequency from the power transmitting coil 21, a power supply receiving device 3 that has a transmitting circuit 37 that outputs an AC signal of a second frequency that is different from the first frequency and causes the AC signal to be transmitted from the power receiving coil 31, and a position estimation device 6 that estimates the positional relationship between the power supply devices 2a to 2c and the power receiving coil 31 based on the strength of the AC signal propagated from the power receiving coil 31 to each of the power supply devices 2a to 2c.

[0052] With this configuration, the transmitting circuit 37 outputs an AC signal set to a frequency that is not synchronized with the AC power, the receiving coil 31 is used for both receiving AC power and transmitting AC signals, and the position estimation device 6 estimates the positional relationship between the power supply devices 2a to 2c and the receiving coil 31 based on the strength of the AC signal received by each transmitting coil 21, thereby accurately grasping the positional relationship between the power supply devices 2a to 2c and the power-supplied device 3 and enabling stable power transmission and reception, and further allowing the moving body 4 to be configured to be lightweight and small.

[0053] Furthermore, the wireless power supply system 1 according to this embodiment is configured such that the position estimation device 6 includes filter circuits 61a to 61c connected to the power transmission coils 21a to 21c, respectively, for blocking AC power and passing AC signals received by the power transmission coils 21a to 21c, and a position estimation unit 63 for estimating the power transmission coils 21a to 21c that are closest to the power receiving coil 31 based on the strength of the AC signals that have passed through the filter circuits 61a to 61c, respectively.

[0054] With this configuration, the filter circuits 61a to 61c extract AC signals from signals of multiple frequency components present in the power supply devices 2a to 2c, and the position estimation unit 63 estimates the power transmission coil 21a to 21c that is closest to the power receiving coil 31 based on the intensity of the AC signals extracted by the filter circuits 61a to 61c, thereby accurately grasping the positional relationship between the power supply devices 2a to 2c and the power supplied device 3, and enabling stable power transmission and reception.

[0055] Furthermore, in the wireless power supply system 1 according to this embodiment, the power-supplied device 3 is arranged between the receiving coil 31 and the load 41 to which AC power is supplied, and further includes a rectifier circuit 34 that can be driven in a predetermined frequency band, and the second frequency is set to a frequency that exceeds the predetermined frequency band or a frequency at which the rectification efficiency of the rectifier circuit 34 is equal to or lower than a predetermined ratio.

[0056] This configuration can prevent the AC signal from interfering with the rectifier circuit 34 in the power-supplied device 3.

[0057] Furthermore, in the wireless power supply system 1 according to this embodiment, the rectifier circuit 34 is a diode bridge circuit having a plurality of diodes 35, and the second frequency is set to a frequency that exceeds the response frequency of the diodes 35 or a frequency at which the output of the diodes 35 becomes lower than a predetermined threshold value of the DC characteristics.

[0058] This configuration can prevent AC signals from interfering with the diode bridge circuit made up of diodes 35.

[0059] (Second embodiment) Next, a wireless power supply system 1 according to a second embodiment of the present invention will be described with reference to Fig. 3. As will be described later, the wireless power supply system 1 according to this embodiment differs from the wireless power supply system 1 according to the first embodiment described above only in the configuration of the position estimation device 6, and therefore the other common configurations are denoted by the same reference numerals and redundant description will be omitted.

[0060] The position estimation device 6 includes antenna coils 65a to 65c, signal detection circuits 62a to 62c, and a position estimation unit 63.

[0061] Antenna coils 65a to 65c are provided at any positions (for example, left and right, front and back, or top and bottom) near power transmitting coils 21a to 21c, and each receives an AC signal transmitted from power receiving coil 31. That is, antenna coil 65a receives the AC signal transmitted from power receiving coil 31 toward power transmitting coil 21a. Similarly, antenna coil 65b receives the AC signal transmitted from power receiving coil 31 toward power transmitting coil 21b, and antenna coil 65c receives the AC signal transmitted from power receiving coil 31 toward power transmitting coil 21c.

[0062] The signal detection circuits 62a to 62c are connected to corresponding antenna coils 65a to 65c, respectively. The signal detection circuit 62a detects the intensity of the AC signal received by the antenna coil 65a. Similarly, the signal detection circuit 62b detects the intensity of the AC signal received by the antenna coil 65b, and the signal detection circuit 62c detects the intensity of the AC signal received by the antenna coil 65c. The signal detection circuits 62a to 62c are each driven by an independent DC power supply (not shown).

[0063] Next, the operation of the wireless power supply system 1 will be described.

[0064] <Initial power transmission> First, when AC power is sequentially supplied to all or at least one of the three power transmitting coils 21, when current is applied to the power transmitting coil 21 closest to the power supplied device 3, an oscillating magnetic field is generated that penetrates the power transmitting coil 21 in the coil axial direction. Furthermore, the oscillation of the magnetic field causes an induced current to flow in the power receiving coil 31, generating an oscillating magnetic field that penetrates the power receiving coil 31 in the coil axial direction. In this way, the magnetic fields of the power transmitting coil 21 and the power receiving coil 31 that are applied with current resonate and are strongly coupled, and AC power of a first frequency (for example, 150 kHz) is transmitted from the power transmitting coil 21 to the power receiving coil 31.

[0065] The AC power supplied from the power supplying device 2 to the power supplied device 3 in the initial power transmission may be small enough to drive the transmitting circuit 37.

[0066] <Signal Transmission> Next, the power receiving coil 31 receives power and the DC voltage is rectified by the rectifier circuit 34, which drives the transmitting circuit 37. The transmitting circuit 37 outputs a weak AC signal to the power receiving coil 31.

[0067] The frequency of the AC signal output by the oscillation circuit 37 is set to a second frequency (for example, several thousand kHz) that is different from the first frequency and its harmonics, in order to prevent the AC signal from interfering with the AC power.

[0068] The second frequency is preferably set to a frequency that exceeds the frequency band that the rectifier circuit 34 can drive, or a frequency at which the rectification efficiency of the rectifier circuit 34 is equal to or less than a predetermined ratio (for example, 1 / 10). In particular, when a diode bridge circuit is used as the rectifier circuit 34, the second frequency is preferably set to a frequency that exceeds the response frequency of the diode 35, or a frequency at which the output of the diode 35 is lower than a predetermined threshold value of the DC characteristics (for example, 1 / 10).

[0069] <Position estimation> Next, the AC signal propagates from the receiving coil 31 to the power supply devices 2a to 2c, and when the antenna coils 65a to 65c each receive the AC signal of the second frequency transmitted from the receiving coil 31, the signal detection circuits 62a to 62c each detect the intensity of the AC signal received by the antenna coils 65a to 65c.

[0070] Next, the position estimation unit 63 estimates the power supply device 2a to 2c that is closest to the power receiving coil 31 according to the strength of the AC signal detected by the signal detection circuits 62a to 62c. Specifically, the position estimation unit 63 compares the strength of the AC signal detected by each of the signal detection circuits 62a to 62c, and estimates that the power supply device 2 corresponding to the signal detection circuit 62a to 62c that received the strongest AC signal is closest to the power receiving coil 31.

[0071] 3, similarly to the first embodiment, the power supplied device 3 (power receiving coil 31) is located closest to the power supply device 2b. Therefore, the AC signal transmitted from the power receiving coil 31 is received by the antenna coil 65b with a strong intensity.

[0072] On the other hand, the power supplied device 3 (power receiving coil 31) is positioned offset from the power supply devices 2a and 2c in the radial direction of the coil, and the distance between the power supply devices 2a and 2c and the power receiving coil 31 is greater than the distance between the power supply device 2b and the power receiving coil 31. Therefore, the AC signal transmitted from the power receiving coil 31 is not received by the antenna coils 65a and 65c or is received with very weak intensity.

[0073] In the following, as described above, the case where the power supply device 2b is closest to the power receiving coil 31 will be described as an example.

[0074] Then, the controller 64 turns on the switch 24b corresponding to the power supply device 2b that the position estimation unit 63 has selected as the closest to the power receiving coil 31, and turns off the switches 24a and 24c corresponding to the other power supply devices 2a and 2c.

[0075] <Main Power Transmission> The magnetic fields of the energized power transmitting coil 21b and power receiving coil 31 resonate and are strongly coupled, and AC power of the first frequency is transmitted from the power transmitting coil 21b to the power receiving coil 31 efficiently.

[0076] It is preferable that the initial power transmission from the power transmitting coil 21 to the power receiving coil 31 be performed at a predetermined cycle (for example, every 5 seconds). This allows the power supply device 2 closest to the power receiving coil 31 to be selected in real time so as to follow the movement of the mobile object 4, even when the mobile object 4 is moving.

[0077] For example, when the power supplied device 3 moves from the vicinity of the power supply device 2b to the vicinity of the power supply device 2c as the moving object 4 moves, the strength of the AC signal detected by the signal detection circuit 62b gradually decreases, while the strength of the AC signal detected by the signal detection circuit 62c gradually increases. If the controller 64 turns off the switch 24b and turns on the switch 24c at the timing when the strength of the AC signal reverses, power can be supplied to the power supplied device 3 without interruption, and the most efficient power transmission can be performed without any loss of total power. Note that by turning on both the switches 24b and 24c around the timing when the strength of the AC signal reverses, the stability of power transmission can be further improved.

[0078] In this way, the wireless power supply system 1 according to this embodiment is configured such that the position estimation device 6 includes antenna coils 65a to 65c that are provided in the vicinity of the power transmission coils 21a to 21c, respectively, and receive AC signals, and a position estimation unit 63 that estimates the power supply device 2a to 2c that is closest to the power receiving coil 31 based on the strength of the AC signals received by the antenna coils 65a to 65c, respectively.

[0079] With this configuration, the position estimation unit 63 estimates the power supply device 2a to 2c that is closest to the power receiving coil 31 based on the strength of the AC signal received by the antenna coils 65a to 65c, thereby accurately grasping the positional relationship between the power supply devices 2a to 2c and the power-supplied device 3, thereby enabling stable power transmission and reception.

[0080] (Third embodiment) In the first and second embodiments described above, an example was given in which the frequency of the AC signal output by the transmitting circuit 37 is set to a second frequency that is different from the first frequency and its harmonics, but the frequency of the AC signal output by the transmitting circuit 37 may be set to the same as the first frequency or to a frequency within a predetermined range (for example, ±1% of the first frequency) that can maintain the resonant state between the transmitting coil 21 and the receiving coil 31.

[0081] With this configuration, the receiving coil 31 and the transmitting coil 21 closest to the receiving coil 31 are in a resonant state, and even if the transmitting coil 21 and the receiving coil 31 are at a distance (for example, 1 m), the AC signal transmitted from the receiving coil 31 is received by one of the nearest transmitting coils 21a to 21c and detected by the signal detection circuits 62a to 62c connected thereto.

[0082] At this time, on the AC power supply 5 side of the power transmitting coils 21a to 21c, the AC power of the first frequency and the AC signal output by the transmission circuit 37 coexist and interfere with each other, but the position estimation device 6 can estimate that one of the power transmitting coils 21a to 21c that received the AC signal is closest to the power receiving coil 31, so there is no need to distinguish between the AC power and the AC signal that interfere with each other. Therefore, the position estimation device 6 can estimate the power transmitting coil 21 that is closest to the power receiving coil 31 by detecting the AC signal disturbed by the influence of interference or by extracting only the AC signal using a low-pass filter or high-pass filter that does not pass the first frequency.

[0083] Furthermore, the present invention can be modified in various ways other than those described above without departing from the spirit of the present invention, and it goes without saying that the present invention also covers such modifications. Furthermore, any or all of the above-described embodiments and modifications may be combined.

[0084] Furthermore, in each of the above-described embodiments, a configuration in which the power transmission coils 21a to 21c are arranged in a single row has been illustrated and described, but the power transmission coils 21 may be arranged in a matrix, or may be arranged three-dimensionally in space.

[0085] In the above-described embodiments, the "strength" of the AC signal includes the presence or absence of the AC signal. For example, if the signal detection circuits 62a to 62c determine that they have received an AC signal, the strength of the AC signal may be determined to be strong, and if the signal detection circuits 62a to 62c cannot receive the AC signal and determine that there is no AC signal, the strength of the AC signal may be determined to be weak.

[0086] Furthermore, in each of the above-described embodiments, the case where position estimation and power transmission are performed for one power supplied device 3 has been described as an example, but position estimation and power transmission may be performed for two or more moving objects 4 in parallel. [Explanation of symbols]

[0087] 1: Wireless power supply system 2, 2a, 2b, 2c: Power supply device 21, 21a, 21b, 21c: transmitting coils 22a, 22b, 22c: Capacitors (of power supply equipment) 23a, 23b, 23c: Power supply side resonant circuit 24a, 24b, 24c: Switch 3: Powered device 31: Receiving coil 32: Capacitor 33: Receiving side resonant circuit 34: Rectifier circuit 35: Diode 36: Capacitor (of powered equipment) 37: Oscillating circuit 4: Moving object 41: Load 5: AC power supply 6:Position estimation device 61a, 61b, 61c: filter circuits 62a, 62b, 62c: signal detection circuit 63:Position estimation part 64: Controller 65a, 65b, 65c: Antenna coil

Claims

1. A wireless power supply system that transmits and receives power using magnetism, a plurality of power supply devices each including a power transmission coil; a power-supplied device including a power receiving coil that receives AC power of a first frequency from the power transmitting coil and a transmission circuit that outputs an AC signal of a second frequency that is different from the first frequency; a plurality of antenna coils provided in the vicinity of the plurality of power transmitting coils in correspondence with the respective power transmitting coils, the antenna coils receiving the AC signal of the second frequency output from the transmitting circuit via the power receiving coil; a plurality of signal detection circuits that detect the AC signals received by the plurality of antenna coils, respectively; a controller that controls power supplied to the plurality of power transmitting coils based on the AC signals detected by the plurality of signal detection circuits; A wireless power supply system comprising:

2. the power-supplied device further includes a rectifier circuit that is provided between the power-receiving coil and a load to which the AC power is supplied and that can be driven in a predetermined frequency band; 2. The wireless power supply system according to claim 1, wherein the second frequency is set to a frequency exceeding the predetermined frequency band or a frequency at which the rectification efficiency of the rectifier circuit is equal to or lower than a predetermined ratio.

3. the power-supplied device is mounted on a moving body, 2. The wireless power supply system according to claim 1, wherein the controller controls the power supplied to the plurality of power transmitting coils in accordance with a positional relationship between the plurality of power transmitting coils and the power receiving coil that moves in accordance with the movement of the moving object.

4. A wireless power supply method using a wireless power supply system that transmits and receives power using magnetism, The wireless power supply system includes: a plurality of power supply devices each including a power transmission coil; a power-supplied device including a power receiving coil that receives AC power of a first frequency from the power transmitting coil and a transmission circuit that outputs an AC signal of a second frequency that is different from the first frequency; a plurality of antenna coils provided in the vicinity of the plurality of power transmitting coils in correspondence with the respective power transmitting coils, the antenna coils receiving the AC signal of the second frequency output from the transmitting circuit via the power receiving coil; a plurality of signal detection circuits that detect the AC signals received by the plurality of antenna coils, respectively; a controller for controlling power supplied to the plurality of power supply devices; Equipped with The wireless power supply method, wherein the controller controls the power supplied to the plurality of power transmission coils based on the AC signals detected by the plurality of signal detection circuits.

5. the power-supplied device is mounted on a moving body, 5. The wireless power supply method according to claim 4, wherein the controller controls the power supplied to the plurality of power transmitting coils in accordance with a positional relationship between the plurality of power transmitting coils and the power receiving coil that moves in accordance with the movement of the moving body.

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