Non-contact power supply device and power reception device

Abstract

A power reception device 3 of a non-contact power supply device 1 has: a plurality of resonance circuits (21-1 to 21-n) which each have a reception coil 22 and a resonance capacitor 23 and receive power from a power transmission device 2 by resonance of the reception coil 22 with the resonance capacitor 23 with respect to AC power supplied to a transmission coil 12 of the power transmission device 2; and a load coil 24 which is disposed so as to be electromagnetically coupled with the reception coil 22 of each resonance circuit and outputs power received from the power transmission device 2 by each resonance circuit. The reception coil 22 of each resonance circuit and the load coil 24 are formed as wiring patterns in mutually different layers of a substrate 5 having a plurality of layers and are connected to each other so that one end of the reception coil 22 of each resonance circuit and one end of the load coil 24 have the same potential.

Description

Contactless power supply device and power receiving device

[0001] The present invention relates to a contactless power supply device and a power receiving device used in the contactless power supply device.

[0002] Research has been conducted into so-called contactless power transfer (also called wireless power transfer) technology, which transfers power through space without using metal contacts, etc. In a power transfer device using contactless power transfer technology (hereinafter simply referred to as a contactless power transfer device), a primary-side (power transmission side) coil (hereinafter referred to as a transmitting coil or primary coil) and a secondary-side (power receiving side) resonant circuit coil (hereinafter referred to as a receiving coil or secondary coil) are electromagnetically coupled, and power is transferred from the power transmitting side device to the power receiving side device via these two coils.

[0003] In such a wireless power transfer technology, a technology has been proposed for preventing an excessively high inter-terminal voltage of a resonant capacitor in a resonant circuit of a power receiving device (see, for example, Patent Document 1). In this technology, the power receiving device has multiple resonant circuits that receive power from a power transmitting device. Each of the multiple resonant circuits has a receiving coil and a resonant capacitor that resonates with the receiving coil and the AC power supplied to the transmitting coil of the power transmitting device, and the receiving coils are arranged to be electromagnetically coupled to each other.

[0004] Japanese Patent Application Laid-Open No. 2020-156218

[0005] Depending on the application of the power receiving device, there may be a demand for miniaturization of the device. However, when multiple resonant circuits are provided in the power receiving device as in the above technology, a lead wire is provided for each resonant circuit, which makes the wiring of the power receiving device complicated, and as a result, there are cases where miniaturization of the power receiving device is restricted.

[0006] Therefore, an object of the present invention is to provide a contactless power supply device that can simplify the wiring of a power receiving device.

[0007] One aspect of the present invention provides a contactless power transfer device including a power transfer device and a power receiving device to which power is transferred contactlessly from the power transfer device. In this contactless power transfer device, the power transfer device includes a transmission coil that supplies power to the power receiving device and a power supply circuit that supplies AC power to the transmission coil. The power receiving device includes a plurality of resonant circuits that have a reception coil and a resonant capacitor and receive power from the power transfer device by resonating the reception coil and the resonant capacitor with AC power supplied to the transmission coil of the power transfer device, and a loading coil that is arranged to be electromagnetically coupled to each of the reception coils of the plurality of resonant circuits and outputs the power received from the power transfer device. The reception coils and loading coils of each of the plurality of resonant circuits are formed as wiring patterns on different layers of a substrate having multiple layers and are connected to each other so that one end of the reception coil and one end of the loading coil of each of the plurality of resonant circuits are at the same potential. By having such a configuration, the contactless power supply device of the present invention can reduce the amount of wiring related to the receiving coil and loading coil of each resonant circuit in the power receiving device, thereby simplifying the wiring of the power receiving device.

[0008] In this contactless power supply device, it is preferable that one end of the receiving coil and one end of the loading coil of each of the plurality of resonant circuits in the power receiving device are grounded, thereby improving the noise resistance of the power receiving device.

[0009] In this contactless power supply device, the other ends of the receiving coils of the plurality of resonant circuits of the power receiving device are preferably separated from each other, thereby preventing a decrease in power transmission efficiency even if the voltages generated by the received power differ for each resonant circuit.

[0010] Furthermore, in this contactless power transfer device, the number of turns of the loading coil of the power receiving device is preferably smaller than the total number of turns of the receiving coils of the multiple resonant circuits of the power receiving device, which makes it easier to operate each resonant circuit under conditions that result in high power transfer efficiency.

[0011] Furthermore, in this contactless power transfer device, it is preferable that the power receiving device further includes a DC-DC converter that operates to step down or step up the voltage output from the loading coil, and a voltage detection circuit that operates the DC-DC converter when the voltage output from the loading coil exceeds a predetermined threshold value, which makes it easy to operate each resonant circuit under conditions that maximize power transmission efficiency.

[0012] According to another embodiment, there is provided a power receiving device that receives power wirelessly transmitted from a transmitting coil of a power transmitting device. The power receiving device includes a plurality of resonant circuits each having a receiving coil and a resonant capacitor, and receiving power from the power transmitting device when the receiving coil and the resonant capacitor resonate with AC power supplied to the transmitting coil of the power transmitting device, and a loading coil arranged to be electromagnetically coupled to each of the receiving coils of the plurality of resonant circuits and outputting the power received from the power transmitting device. The receiving coils and loading coils of each of the plurality of resonant circuits are formed as wiring patterns on different layers of a substrate having multiple layers, and are connected to each other so that one end of the receiving coil and one end of the loading coil of each of the plurality of resonant circuits are at the same potential. With this configuration, the power receiving device according to the present invention can reduce the amount of wiring associated with the receiving coil and loading coil of each resonant circuit, thereby simplifying the wiring.

[0013] FIG. 1 is a schematic diagram of a contactless power transfer device according to one embodiment of the present invention. FIG. 2 is a schematic side cross-sectional view of a substrate on which the receiving coils and loading coils of each resonant circuit are arranged. FIG. 3A is a schematic plan view showing the arrangement of individual receiving coils and loading coils on one layer of the substrate, as viewed from the normal direction to the surface of the substrate. FIG. 3B is a schematic plan view showing the arrangement of individual receiving coils and loading coils on another layer of the substrate, as viewed from the normal direction to the surface of the substrate. FIG. 3C is a schematic plan view showing the arrangement of individual receiving coils and loading coils on yet another layer of the substrate, as viewed from the normal direction to the surface of the substrate. FIG. 3D is a schematic plan view showing the arrangement of individual receiving coils and loading coils on yet another layer of the substrate, as viewed from the normal direction to the surface of the substrate. FIG. 4 is a diagram showing an example of the operating characteristics of a DC-DC converter.

[0014] A contactless power transfer device according to one embodiment of the present invention will be described below with reference to the drawings. In this contactless power transfer device, a power receiving device (hereinafter simply referred to as a power receiving device) has multiple resonant circuits that resonate with AC power supplied to a transmitting coil of a power transmitting device (hereinafter simply referred to as a power transmitting device). Each resonant circuit in the power receiving device has a receiving coil and a resonant capacitor. The receiving coil of each resonant circuit is arranged so as to be electromagnetically coupled to a loading coil, and the power receiving device outputs power received by each resonant circuit from the loading coil. Furthermore, the receiving coil and loading coil of each resonant circuit are formed by wiring patterns on different layers of a substrate having multiple layers. The receiving coil and loading coil of each resonant circuit are connected to each other via vias in the substrate so that one end of the receiving coil and one end of the loading coil of each resonant circuit are at the same potential. In this way, by connecting one end of the receiving coil and one end of the loading coil of each resonant circuit to each other so that they are at the same potential, preferably grounded, the wiring of the power receiving device is simplified.

[0015] FIG. 1 is a schematic diagram of a contactless power transfer device according to one embodiment of the present invention. As shown in FIG. 1, the contactless power transfer device 1 includes a power transfer device 2 and a power receiving device 3 to which power is transferred contactlessly from the power transfer device 2 via space. The power transfer device 2 includes a power supply circuit 11, a transmission coil 12, and a capacitor 13. The power receiving device 3 includes n resonant circuits 21-1 to 21-n (where n is an integer equal to or greater than 2; in the example shown in FIG. 1, n=3), a loading coil 24, a rectifying and smoothing circuit 25, a voltage detection circuit 26, and a DC-DC converter 27, and outputs power received from the power transfer device 2 to a load circuit 4. In this embodiment, the contactless power transfer device 1 is a contactless power transfer device of a type (NP type) in which a receiving coil and a resonant capacitor resonate in parallel on the secondary side without using resonance on the primary side. However, the contactless power supply device 1 may also be a device conforming to other contactless power supply methods, such as a method (SP method) in which the transmitting coil 12 and capacitor 13 resonate in series on the primary side and the receiving coil and resonant capacitor resonate in parallel on the secondary side.

[0016] First, the power transmission device 2 will be described. The power supply circuit 11 supplies AC power to the transmission coil 12. To this end, the power supply circuit 11 includes, for example, a DC power supply that supplies DC power, an inverter circuit that converts the DC power supplied from the DC power supply into AC power and supplies it to the transmission coil 12, and a control circuit that controls the inverter circuit. The inverter circuit may be a full-bridge inverter in which four switching elements (e.g., MOSFETs) are connected in a full-bridge configuration, or a half-bridge inverter in which two switching elements are connected in a half-bridge configuration. Alternatively, the inverter circuit may have the same configuration as a class E amplifier. The control circuit controls the on / off switching of each switching element of the inverter circuit so that the frequency of the AC power supplied to the transmission coil 12 becomes a predetermined frequency (e.g., a frequency at which each resonant circuit of the power receiving device 3 can resonate when the degree of coupling between the receiving coil of each resonant circuit and the transmission coil 12 is a predetermined value). The power supply circuit 11 may further include a DC-DC converter between the DC power supply and the inverter circuit.

[0017] The transmitting coil 12 is electromagnetically coupled to the receiving coil of each resonant circuit of the power receiving device 3, thereby transmitting the AC power supplied from the power supply circuit 11 to the resonant circuits 21-1 to 21-n of the power receiving device 3 through space.

[0018] The capacitor 13 is connected in series with the transmitting coil 12 between the transmitting coil 12 and the inverter circuit of the power supply circuit 11. In this embodiment, the capacitor 13 is provided to block DC power. Therefore, the capacitance of the capacitor 13 is set so that the resonant circuit formed by the transmitting coil 12 and the capacitor 13 does not resonate with the AC power supplied to the transmitting coil 12, that is, so that the frequency of the AC power supplied to the transmitting coil 12 is different from the resonant frequency of the resonant circuit. Note that if the power supply circuit 11 has a full-bridge inverter, the capacitor 13 may be omitted.

[0019] Next, a description will be given of the power receiving device 3. Each of the n resonant circuits 21-1 to 21-n has a receiving coil 22 and a resonant capacitor .

[0020] In this embodiment, in each of the resonant circuits 21-1 to 21-n, the receiving coil 22 and the resonant capacitor 23 are connected in parallel. The receiving coil 22 and the resonant capacitor 23 form a closed loop in each of the resonant circuits 21-1 to 21-n. Furthermore, the inductance of the receiving coil 22 and the capacitance of the resonant capacitor 23 in each of the resonant circuits 21-1 to 21-n are set so that the product of the inductance and capacitance of each resonant circuit can be equal to each other, and so that each resonant circuit can resonate with the AC power supplied to the transmitting coil 12. For example, the inductance of the receiving coil 22 in each of the resonant circuits 21-1 to 21-n is set to be the same as each other, and the capacitance of the resonant capacitor 23 in each of the resonant circuits 21-1 to 21-n is set to be the same as each other.

[0021] Furthermore, the receiving coil 22 of each of the resonant circuits 21-1 to 21-n is arranged so as to be electromagnetically coupled to the loading coil 24. Therefore, when the power transmitting device 2 and the power receiving device 3 are positioned so that power can be transmitted from the power transmitting device 2 to the power receiving device 3, the receiving coil 22 of each of the resonant circuits 21-1 to 21-n resonates with the resonant capacitor 23 and is electromagnetically coupled to the transmitting coil 12, thereby allowing each resonant circuit to receive power from the transmitting coil 12. Furthermore, the power received by each of the resonant circuits 21-1 to 21-n is output via the loading coil 24.

[0022] The loading coil 24 is arranged so as to be electromagnetically coupled to the receiving coil 22 of each of the resonant circuits 21-1 to 21-n. Both ends of the loading coil 24 are connected to the rectifying and smoothing circuit 25. Therefore, the power received by each of the resonant circuits 21-1 to 21-n from the power transmission device 2 is output from the loading coil 24 to the load circuit 4 via the rectifying and smoothing circuit 25 and the DC-DC converter 27.

[0023] The rectifying and smoothing circuit 25 is connected between the loading coil 24 and the DC-DC converter 27 and rectifies and smoothes the power output from the loading coil 24 to convert it into DC power. The rectifying and smoothing circuit 25 then outputs the converted DC power to the DC-DC converter 27. In this embodiment, the rectifying and smoothing circuit 25 includes a half-round rectifier circuit formed by a single diode connected to one end of the loading coil 24 opposite the grounded end, and a smoothing capacitor on the output side of the half-round rectifier circuit that smoothes the power rectified by the half-round rectifier circuit. By configuring the rectifying and smoothing circuit 25 as a half-round rectifier circuit in this way, the potential at the negative output terminal of the rectifying and smoothing circuit 25 can be made equal to the potential at one end of the receiving coil 22 and one end of the loading coil 24 of each of the resonant circuits 21-1 to 21-n. This makes it possible to ground one end of the receiving coil 22 and one end of the loading coil 24 of each of the resonant circuits 21-1 to 21-n. As a result, it is possible to improve the resistance of the power receiving device 3 to noise.

[0024] The voltage detection circuit 26 is connected between the rectifying and smoothing circuit 25 and the DC-DC converter 27, and turns on the DC-DC converter 27 when the voltage output from the rectifying and smoothing circuit 25 exceeds a predetermined threshold. In this embodiment, the voltage detection circuit 26 is configured with a Zener diode. The anode terminal of the Zener diode is connected to the on / off control terminal of the DC-DC converter 27, and the cathode terminal is connected to the positive output terminal of the rectifying and smoothing circuit 25. Therefore, when the voltage output from the rectifying and smoothing circuit 25 is equal to or lower than the breakdown voltage of the Zener diode (corresponding to the predetermined threshold), a relatively low voltage is applied to the on / off control terminal of the DC-DC converter 27, and the DC-DC converter 27 is turned off. On the other hand, when the voltage output from rectifying and smoothing circuit 25 exceeds the breakdown voltage of the Zener diode, a relatively high voltage equivalent to the voltage output from rectifying and smoothing circuit 25 is applied to the on / off control terminal of DC-DC converter 27, turning on DC-DC converter 27 and operating to maintain a constant output power. Note that voltage detection circuit 26 is not limited to the above example, and may have another circuit configuration that can turn on DC-DC converter 27 when the output voltage from rectifying and smoothing circuit 25 exceeds a predetermined threshold.

[0025] The DC-DC converter 27 is connected between the rectifying and smoothing circuit 25 and the load circuit 4. When an ON voltage is applied to the ON / OFF control terminal, the DC-DC converter 27 converts the voltage input via the rectifying and smoothing circuit 25 to increase or decrease the voltage so that the power output from the DC-DC converter 27 is constant, and outputs the converted DC power to the load circuit 4 via a smoothing capacitor connected between the DC-DC converter 27 and the load circuit 4. When an OFF voltage is applied to the ON / OFF control terminal, the DC-DC converter 27 stops outputting power to the load circuit 4. In order to improve power transmission efficiency, the DC-DC converter 27 is preferably a step-down DC-DC converter. However, the DC-DC converter 27 may be a step-up or step-down DC-DC converter as long as it is capable of outputting a voltage at which the load circuit 4 operates.

[0026] The arrangement of the receiving coil 22 and the loading coil 24 of each of the resonant circuits 21-1 to 21-n will be described below.

[0027] FIG. 2 is a schematic side cross-sectional view of the substrate 5 on which the receiving coils 22 and loading coils 24 of each of the resonant circuits 21-1 to 21-n are arranged. Also, FIGS. 3A to 3D are schematic plan views showing the arrangement of the individual receiving coils 22 and loading coils 24 on each of the layers 5a to 5d of the substrate 5, as viewed from the normal direction to the surface of the substrate 5. Note that FIGS. 3A to 3D omit illustration of wiring patterns other than those of the individual resonant circuits 21-1 to 21-n and loading coils 24. In this example, the power receiving device 3 has three resonant circuits (i.e., n = 3). Furthermore, in FIGS. 2 and 3A to 3D, the receiving coils of the resonant circuits 21-k (k = 1, 2, 3) are each denoted as receiving coils 22-k.

[0028] 2, the substrate 5 made of an insulator is, for example, a substrate with a thickness of about 1 mm to several mm and has multiple layers 5a to 5d. The receiving coil 22-k and the loading coil 24 of each resonant circuit 21-k are arranged on different layers of the substrate 5. In this example, the loading coil 24 is arranged on the second layer 5c, which is closest to the transmitting coil 12 during power transmission. However, the layer on which the loading coil 24 is arranged is not limited to this example; the loading coil 24 may be arranged on the layer 5a farthest from the transmitting coil 12, the layer 5d closest to the transmitting coil 12, or another intermediate layer 5b.

[0029] As shown in FIGS. 3A to 3D, the receiving coils 22-k and the loading coils 24 are formed as wiring patterns with line widths of less than 1 mm to several mm on different layers of the substrate 5 so that they are coaxial and preferably have the same outer diameter. This arrangement of the receiving coils 22-k and the loading coils 24 allows the receiving coils 22-k and the loading coils 24 to be electromagnetically coupled to each other. One end of each receiving coil 22-k and one end of the loading coil 24 are connected to each other via vias 51 provided in the substrate 5. Therefore, one end of each receiving coil 22-k and one end of the loading coil 24 are at the same potential. Forming the receiving coils 22-k and the loading coil 24 in this manner eliminates the need to provide lead wires for each coil, simplifying the wiring. Because a higher voltage is applied to the loading coil 24 than to the resonant circuits 21-k, the width of the wiring pattern of the loading coil 24 is preferably wider than that of the receiving coils 22-k to reduce loss.

[0030] Furthermore, on the layer 5c on which the loading coil 24 is provided, one end of the loading coil 24 is connected to a grounded via 52. Therefore, one end of each receiving coil 22-k and one end of the loading coil 24 are grounded. This suppresses the effects of noise. Meanwhile, the other ends of the receiving coils 22-k are separated from each other. In the example shown in FIGS. 3A to 3D, the other end of each receiving coil 22-k is connected to one end of a corresponding resonant capacitor provided on the layer 5a via a via. This is for the following reason. That is, because the receiving coils 22-k of each resonant circuit 21-k are provided on different layers of the substrate 5, the degree of coupling to the transmitting coil 12 varies slightly for each resonant circuit 21-k. As a result, the voltage of the power received by each resonant circuit 21-k also varies slightly. If the other ends of the receiving coils 22-k were also connected to each other, a current corresponding to the difference in voltage generated from the resonant circuit that generates the highest voltage to the other resonant circuits would flow, resulting in a decrease in power transmission efficiency. However, in this embodiment, the other ends of the receiving coils 22-k are separated from each other, preventing such a current flow between the resonant circuits, thereby suppressing a decrease in power transmission efficiency.

[0031] Furthermore, the number of turns of the loading coil 24 is preferably smaller than the total number of turns of each of the receiving coils 22. In particular, the number of turns of the loading coil 24 is preferably 1 turn or less (for example, 0.5, 0.6, or 0.8 turns).

[0032] In this embodiment, each resonant circuit 21-k is configured so that the receiving coil 22 and the resonant capacitor are in parallel resonance. When such parallel resonance is used for power transmission, it is known that power transmission efficiency is optimized and the resistance of the load connected to the resonant circuit becomes relatively large. Furthermore, in this embodiment, the receiving coil 22 and the loading coil 24 of each resonant circuit 21-k are arranged so that they can be electromagnetically coupled to each other, so the power receiving device 3 can be represented by an equivalent circuit that receives power through one resonant circuit and outputs the received power to the load. The equivalent resistance R" of the load in this equivalent circuit (hereinafter referred to as the equivalent load for convenience of explanation) is the equivalent resistance R' of the load connected to the loading coil 24 multiplied by the square of m, which is the ratio of the total number of turns of the receiving coil 22 of each resonance circuit 21-k to the number of turns of the loading coil 24. In the example shown in FIG. 2 and FIGS. 3A to 3D, the number n of resonance circuits is 3. Furthermore, the number of turns of each receiving coil 22-k is 2, and the number of turns of the loading coil 24 is 1. Therefore, m=(3*2) 2 = 36. Therefore, the equivalent resistance R" of the equivalent load is m 2 *R' = 36 *R'. In this way, the larger the value of the ratio m, the larger the equivalent resistance R" of the equivalent load, making it easier to optimize power transmission efficiency. Therefore, by setting the relationship between the number of turns of each receiving coil 22 and the number of turns of the loading coil 24 as described above, it becomes easier to optimize power transmission efficiency. Furthermore, by setting the number of turns of the loading coil 24 to one turn or less, it becomes easy to connect one end of the loading coil 24 to the via 52 that is grounded. Furthermore, even if the number of turns of the receiving coil 22-k of each resonant circuit is two or more, it becomes easy to ground one end of the receiving coil 22-k through the via 51 that is connected to the loading coil 24.

[0033] Furthermore, in this embodiment, since the load coil 24 is connected to the load circuit 4 via the DC-DC converter 27, the equivalent resistance R' of the load connected to the load coil 24 is a value obtained by multiplying the resistance R of the load circuit 4 by the square of the ratio (Vo / Vin) of the output voltage Vo from the DC-DC converter 27 to the input voltage Vin to the DC-DC converter 27 (i.e., R'=R*(Vo / Vin) 2 Therefore, by performing a step-down operation of the DC-DC converter 27, it is possible to make the equivalent resistance R″ larger than the resistance R of the load circuit 4, making it easier to optimize the power transmission efficiency.

[0034] Furthermore, in order to maintain a constant output power, the DC-DC converter 27 operates so that the duty ratio of its switching elements increases as the input voltage Vin decreases. As the duty ratio increases, the average value of the current flowing through the input side of the DC-DC converter 27 increases, resulting in a smaller equivalent resistance R'. Therefore, if the input voltage Vin is low, the output power from the DC-DC converter 27 may not reach the target power value, causing the operation of the DC-DC converter 27 to become unstable. Alternatively, if there are multiple operating conditions under which the output voltage from the DC-DC converter 27 remains constant, the lower the input voltage Vin, the more likely it is that the converter will converge to the operating condition with the smaller equivalent resistance R'. Conversely, as the input voltage Vin increases, the DC-DC converter 27 operates so that the duty ratio of its switching elements decreases, resulting in a larger equivalent resistance R'. Therefore, as described above, by turning on DC-DC converter 27 when the voltage output from rectifying and smoothing circuit 25 exceeds a predetermined threshold, it becomes possible to stabilize the operation of DC-DC converter 27 and operate DC-DC converter 27 under operating conditions that increase equivalent resistance R', thereby improving power transmission efficiency.

[0035] FIG. 4 is a diagram showing an example of the operating characteristics of the DC-DC converter 27. In FIG. 4, the horizontal axis represents the equivalent resistance R', and the vertical axis represents the output power Wo from the DC-DC converter 27. Graph 400 shows the relationship between the equivalent resistance R' and the output power Wo due to the operation of the DC-DC converter 27. As shown in graph 400, there are two equivalent resistance R' points (operating points A and B) that result in the target output power Wt. As described above, when the input voltage Vin is low, the DC-DC converter 27 operates to lower the equivalent resistance R', so that the DC-DC converter 27 operates so that the value of the equivalent resistance R' approaches operating point A, where the value of the equivalent resistance R' is lower. On the other hand, if the input voltage Vin is sufficiently high (i.e., higher than a predetermined threshold), the DC-DC converter 27 can be operated so that the value of the equivalent resistance R' approaches operating point B, where the value of the equivalent resistance R' is higher. As a result, it is possible to increase the equivalent resistance R'' of the equivalent load, thereby improving power transmission efficiency.

[0036] As described above, the power receiving device of this contactless power transfer device has multiple resonant circuits that can resonate with AC power supplied to the transmitting coil of the power transmitting device, and a loading coil that extracts the received power in each resonant circuit. The receiving coil and loading coil of each resonant circuit are formed by wiring patterns on different layers of a substrate having multiple layers, and the receiving coil and loading coil of each resonant circuit are connected so that one end of the receiving coil and one end of the loading coil of each resonant circuit are at the same potential. Therefore, this contactless power transfer device can simplify the wiring of the power receiving device. Furthermore, because the power receiving device receives power through multiple resonant circuits, an excessive increase in the voltage between the resonant capacitor terminals of each resonant circuit is suppressed.

[0037] According to a modified example, the rectifying and smoothing circuit 25 of the power receiving device 3 may have a full-wave rectifying circuit in which four diodes are connected in a full-bridge configuration, instead of a half-end rectifying circuit consisting of a single diode. In this case, the potential of each output terminal of the rectifying and smoothing circuit 25 connected to the load circuit 4 differs from the potential of one end of the receiving coil 22 and one end of the loading coil 24 of each connected resonant circuit. Therefore, when one end of the load circuit 4 is grounded, one end of the receiving coil 22 and one end of the loading coil 24 of each resonant circuit are not grounded. Furthermore, if it is expected that the voltage output from the rectifying and smoothing circuit 25 of the power receiving device 3 during power transmission will be a voltage that allows the load circuit 4 to operate, the voltage detection circuit 26 and the DC-DC converter 27 may be omitted.

[0038] As described above, those skilled in the art can make various modifications to the embodiments within the scope of the present invention.

[0039] REFERENCE SIGNS LIST 1 non-contact power supply device 2 power transmission device 11 power supply circuit 12 transmission coil 13 capacitor 3 power reception device 4 load circuit 5 substrate 51, 52 vias 21-1 to 21-n resonance circuit 22, 22-1 to 22-3 reception coil 23 resonance capacitor 24 load coil 25 rectification smoothing circuit 26 voltage detection circuit 27 DC-DC converter

Claims

1. A contactless power supply device having a power transmission device and a power receiving device to which power is transmitted contactlessly from the power transmission device, wherein the power transmission device has a transmitting coil that supplies power to the power receiving device, and a power supply circuit that supplies AC power to the transmitting coil, the power receiving device has a receiving coil and a resonant capacitor, and receives power from the power transmission device by resonating with the receiving coil and the resonant capacitor with the AC power supplied to the transmitting coil of the power transmission device, and a loading coil that is arranged so as to be electromagnetically coupled to the receiving coil of each of the plurality of resonant circuits and outputs the power received from the power transmission device, the receiving coil and the loading coil of each of the plurality of resonant circuits are formed as wiring patterns in different layers of a substrate having multiple layers, and one end of the receiving coil and one end of the loading coil of each of the plurality of resonant circuits are connected to each other so that they are at the same potential.

2. The contactless power supply device according to claim 1, wherein one end of the receiving coil and one end of the loading coil of each of the plurality of resonant circuits are grounded.

3. The contactless power supply device according to claim 1 or 2, wherein the other ends of the receiving coils of each of the plurality of resonant circuits are separated from each other.

4. The contactless power supply device according to claim 1 or 2, wherein the number of turns of the load coil is smaller than the total number of turns of the receiving coils of each of the plurality of resonant circuits.

5. The contactless power supply device according to claim 1 or 2, further comprising: a DC-DC converter that operates to step down or step up the voltage output from the loading coil; and a voltage detection circuit that operates the DC-DC converter when the voltage output from the loading coil exceeds a predetermined threshold value.

6. A power receiving device that receives power transmitted contactlessly from a transmitting coil of a power transmitting device, comprising: a plurality of resonant circuits each having a receiving coil and a resonant capacitor, and receiving power from the power transmitting device by resonating between the receiving coil and the resonant capacitor with AC power supplied to the transmitting coil of the power transmitting device; and a loading coil arranged so as to be electromagnetically coupled to the receiving coil of each of the plurality of resonant circuits, and each of the plurality of resonant circuits outputs the power received from the power transmitting device; the receiving coil and the loading coil of each of the plurality of resonant circuits are formed as wiring patterns in different layers of a substrate having multiple layers, and one end of the receiving coil and one end of the loading coil of each of the plurality of resonant circuits are connected to each other so that they are at the same potential.

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