Method for detecting metal foreign object in contactless power supply system, contactless power supply device, power reception device, and contactless power supply system

• US 9,177,716 B2
• Filed: 10/17/2012
• Issued: 11/03/2015
• Est. Priority Date: 08/25/2011
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Inventors: Goto, Hiromichi
• Primary Examiner(s): Barnie, Rexford
• Assistant Examiner(s): Ly, Xuan
• Application Number:
  US13/653,487
• Publication Number:
  US 20130093257A1
• Time in Patent Office: 1,112 Days
• Field of Search: 307/29, 307/104, 320/108
• US Class Current: 1/1
• CPC Class Codes: G01V 3/10 using induction coils
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H01M 10/46 Accumulators structurally combined with charging apparatus circuits for charging H02J7/00
• CPC Class Codes: H02J 50/005 Mechanical details of housing or structure aiming to accommodate the power transfer means, e.g. mechanical integration of coils, antennas or transducers into emitting or receiving devices
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/402 the two or more transmitting or the two or more receiving devices being integrated in the same unit, e.g. power mats with several coils or antennas with several sub-antennas
• CPC Class Codes: H02J 50/60 responsive to the presence of foreign objects, e.g. detection of living beings
• CPC Class Codes: H02J 7/00045 Authentication, i.e. circuits for checking compatibility between one component, e.g. a battery or a battery charger, and another component, e.g. a power source
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A contactless power supply system includes a power supply areas, each provided with a primary coil and a primary authentication coil. The primary coil and primary authentication coil are arranged at different locations. An electric appliance includes a power reception area provided with a secondary coil and a secondary authentication coil. The secondary coil and the secondary verification coil are arranged at different locations. The presence of a metal foreign object is detected between the primary coil and secondary coil based on a transmission oscillation signal generated by the primary coil, and the presence of a metal foreign object is detected between the primary authentication coil and secondary authentication coil based on an authentication oscillation signal generated by the primary authentication coil.

Claims

1. A method for detecting a metal foreign object in a contactless power supply system including a contactless power supply device and a power reception device, wherein the contactless power supply device includes at least one power supply area and a primary coil and a primary authentication coil, which correspond to the power supply area, and wherein the power reception device is arranged in an electric appliance, which includes at least one power reception area, and includes a secondary coil and a secondary authentication coil, which correspond to the power reception area, the method comprising:

transmitting an authentication oscillating signal from the primary authentication coil;

generating an authentication signal with the secondary authentication coil in response to the authentication oscillating signal;

after the authentication signal is received by the primary authentication coil and authenticated, generating secondary power at the secondary coil with a power transmission oscillating signal generated by the primary coil;

detecting whether or not a metal foreign object is present between the primary coil and the secondary coil based on the power transmission oscillating signal from the primary coil; and

detecting whether or not a metal foreign object is present between the primary authentication coil and the secondary authentication coil based on the authentication oscillating signal from the primary authentication coil, wherein

the primary authentication coil includes a first primary authentication coil and a second primary authentication coil that are connected in series to generate magnetic fluxes in opposite directions,

the primary coil is wound around a core projecting from a first magnetic body, the first magnetic body having a shape in conformance with the contour of the power supply area,

the primary coil is arranged in the middle of the power supply area while the first primary authentication coil and the second primary authentication coil are arranged in the power supply area at symmetrical locations with the primary coil arranged in between, the primary coil partially overlapping each of the first primary authentication coil and the second primary authentication coil in a plan view, and the first and second primary authentication coils each including a portion that does not overlap the primary coil in a plan view, and

the secondary coil is wound around a core projecting from a second magnetic body, the second magnetic body having a shape in conformance with the contour of the power reception area,

the secondary authentication coil includes a first secondary authentication coil and a second secondary authentication coil that are connected in series to generate magnetic fluxes in opposite directions, and

the secondary coil is arranged in the middle of the power reception area while the first secondary authentication coil and the second secondary authentication coil are arranged in the power reception area at symmetrical locations with the secondary coil arranged in between, the secondary coil partially overlapping each of the first secondary authentication coil and the second secondary authentication coil in a plan view, and the first and second secondary authentication coils each including a portion that does not overlap the secondary coil in a plan view.

2. The method for detecting a metal foreign object according to claim 1, wherein

the detection of a metal foreign object between the primary coil and the secondary coil is performed before the detection of a metal foreign object between the primary authentication coil and the secondary authentication coil, and

when a metal foreign object is detected to be present between the primary coil and the secondary coil, the detection of a metal foreign object between the primary authentication coil and the secondary authentication coil is not performed.

3. The method for detecting a metal foreign object according to claim 2, wherein

the power transmission oscillating signal generated by the primary coil has a lower oscillation frequency than that of the authentication oscillating signal generated by the primary authentication coil.

4. The method for detecting a metal foreign object according to claim 1, wherein

the detection of a metal foreign object between the primary authentication coil and the secondary authentication coil is performed before the detection of a metal foreign object between the primary coil and the secondary coil, and

when a metal foreign object is detected to be present between the primary authentication coil and the secondary authentication coil, the detection of a metal foreign object between the primary coil and the secondary coil is not performed.

5. The method for detecting a metal foreign object according to claim 4, wherein

the authentication oscillating signal generated by the primary authentication coil has a lower oscillation frequency than that of the power transmission oscillating signal generated by the primary coil.

6. A method for detecting a metal foreign object in a contactless power supply system including a contactless power supply device and a power reception device, wherein the contactless power supply device includes at least one power supply area and a primary coil and a primary authentication coil, which correspond to the power supply area, and wherein the power reception device is arranged in an electric appliance, which includes at least one power reception area, and includes a secondary coil and a secondary authentication coil, which correspond to the power reception area, the method comprising:

transmitting an authentication oscillating signal from the primary authentication coil;

generating an authentication signal with the secondary authentication coil in response to the authentication oscillating signal;

after the authentication signal is received by the primary authentication coil and authenticated, generating secondary power at the secondary coil with a power transmission oscillating signal generated by the primary coil;

detecting whether or not a metal foreign object is present between the primary coil and the secondary coil based on the power transmission oscillating signal from the primary coil; and

detecting whether or not a metal foreign object is present between the primary authentication coil and the secondary authentication coil based on the authentication oscillating signal from the primary authentication coil, wherein

the primary coil includes a first primary coil and a second primary coil that are connected in series to generate magnetic fluxes in opposite directions, with the first and second primary coils being wound around two cores projecting from a first magnetic body, the first magnetic body having a shape in conformance with the contour of the power supply area, and

the primary authentication coil is arranged in the middle of the power supply area while the first primary coil and the second primary coil are arranged in the power supply area at symmetrical locations with the primary authentication coil arranged in between, the primary authentication coil partially overlapping each of the first primary coil and the second primary coil in a plan view, and the first and second primary coils each including a portion that does not overlap the primary authentication coil in a plan view,

the secondary coil includes a first secondary coil and a second secondary coil that are connected in series to generate magnetic fluxes in opposite directions, with the first and second secondary coils being wound around two cores projecting from a second magnetic body, the second magnetic body having a shape in conformance with the contour of the power reception area, and

the secondary authentication coil is arranged in the middle of the power reception area while the first secondary coil and the second secondary coil are arranged in the power reception area at symmetrical locations with the secondary authentication coil arranged in between, the secondary authentication coil partially overlapping each of the first secondary coil and the second secondary coil in a plan view, and the first and second secondary coils each including a portion that does not overlap the secondary authentication coil in a plan view.

7. A contactless power supply device for use with a power reception device including a power reception area, a secondary coil, which generates secondary power in response to a power transmission oscillating signal, and a secondary authentication coil that generates an authentication signal in response to an authentication oscillating signal, wherein the secondary authentication coil includes a first secondary authentication coil and a second secondary authentication coil that are connected in series to generate magnetic fluxes in opposite directions, the secondary coil is wound around a core projecting from a second magnetic body, the second magnetic body having a shape in conformance with the contour of the power reception area, the secondary coil is arranged in the middle of the power reception area while the first secondary authentication coil and the second secondary authentication coil are arranged in the power reception area at symmetrical locations with the secondary coil arranged in between, the secondary coil partially overlapping each of the first secondary authentication coil and the second secondary authentication coil in a plan view, and the first and second secondary authentication coils each including a portion that does not overlap the secondary coil in a plan view, the contactless power supply device comprising:

at least one power supply area;

a primary coil, which generates the power transmission oscillating signal, and a primary authentication coil, which generates the authentication oscillating signal, wherein the primary coil and the primary authentication coil correspond to the power supply area;

a first envelope detection circuit that converts a power transmission load modulation signal into a first load modulation signal by detecting an envelope of the power transmission load modulation signal when the primary coil receives the power transmission load modulation signal reflecting a variation in a magnetic flux between the primary coil and the secondary coil resulting from the power transmission oscillating signal generated by the primary coil;

a second envelope detection circuit that converts an authentication load modulation signal into a second load modulation signal by detecting an envelope of the authentication load modulation signal when the primary authentication coil receives the authentication load modulation signal reflecting a variation in a magnetic flux between the primary authentication coil and the secondary authentication coil resulting from the authentication oscillating signal generated by the primary authentication coil; and

a system controller that determines whether or not a metal foreign object is present in the power supply area based on the first load modulation signal, which is provided from the first envelope detection circuit, and the second load modulation signal, which is provided from the second envelope detection circuit,

wherein the primary authentication coil includes a first primary authentication coil and a second primary authentication coil that are connected in series to generate magnetic fluxes in opposite directions,

the primary coil is wound around a core projecting from a first magnetic body, the first magnetic body having a shape in conformance with the contour of the power supply area, and

the primary coil is arranged in the middle of the power supply area while the first primary authentication coil and the second primary authentication coil are arranged in the power supply area at symmetrical locations with the primary coil arranged in between, the primary coil partially overlapping each of the first primary authentication coil and the second primary authentication coil in a plan view, and the first and second primary authentication coils each including a portion that does not overlap the primary coil in a plan view.

8. The contactless power supply device according to claim 7, wherein the at least one power supply area is a plurality of power supply areas, the contactless power supply device further comprises:

a plurality of excitation circuits corresponding to the plurality of power supply areas, respectively; and

a plurality of oscillation circuits corresponding to the plurality of power supply areas, respectively,

each of the excitation circuits excites the primary coil in the corresponding power supply area to transmit the power transmission oscillating signal, and

each of the oscillation circuits excites the primary authentication coil in the corresponding power supply area to transmit the authentication oscillating signal.

10. The contactless power supply device according to claim 7, wherein

the primary coil is arranged at a lower side of the primary authentication coil so that the primary authentication coil is proximal to the power reception device, and

the primary coil is wound around the core projecting upward from the first c having a larger coil area than the primary coil.

9. A contactless power supply device for use with a power reception device including a power reception area, a secondary coil, which generates secondary power in response to a power transmission oscillating signal, and a secondary authentication coil that generates an authentication signal in response to an authentication oscillating signal, wherein the secondary authentication coil includes a first secondary authentication coil and a second secondary authentication coil that are connected in series to generate magnetic fluxes in opposite directions, the secondary coil is wound around a core projecting from a second magnetic body, the second magnetic body having a shape in conformance with the contour of the power reception area, the secondary coil is arranged in the middle of the power reception area while the first secondary authentication coil and the second secondary authentication coil are arranged in the power reception area at symmetrical locations with the secondary coil arranged in between, the secondary coil partially overlapping each of the first secondary authentication coil and the second secondary authentication coil in a plan view, and the first and second secondary authentication coils each including a portion that does not overlap the secondary coil in a plan view, the contactless power supply device comprising:

at least one power supply area;

a primary coil, which generates the power transmission oscillating signal, and a primary authentication coil, which generates the authentication oscillating signal, wherein the primary coil and the primary authentication coil correspond to the power supply area;

a first envelope detection circuit that converts a power transmission load modulation signal into a first load modulation signal by detecting an envelope of the power transmission load modulation signal when the primary coil receives the power transmission load modulation signal reflecting a variation in a magnetic flux between the primary coil and the secondary coil resulting from the power transmission oscillating signal generated by the primary coil;

a second envelope detection circuit that converts an authentication load modulation signal into a second load modulation signal by detecting an envelope of the authentication load modulation signal when the primary authentication coil receives the authentication load modulation signal reflecting a variation in a magnetic flux between the primary authentication coil and the secondary authentication coil resulting from the authentication oscillating signal generated by the primary authentication coil; and

a system controller that determines whether or not a metal foreign object is present in the power supply area based on the first load modulation signal, which is provided from the first envelope detection circuit, and the second load modulation signal, which is provided from the second envelope detection circuit, wherein

the primary coil includes a first primary coil and a second primary coil that are connected in series to generate magnetic fluxes in opposite directions,

the first and second primary coils are wound around two cores projecting from a first magnetic body, the first magnetic body having a shape in conformance with the contour of the power supply area, and

the primary authentication coil is arranged in the middle of the power supply area while the first primary coil and the second primary coil are arranged at symmetrical locations with the primary authentication coil arranged in between, the primary authentication coil partially overlapping each of the first primary coil and the second primary coil in a plan view, and the first and second primary coils each including a portion that does not overlap the primary authentication coil in a plan view.

11. A power reception device for use with a contactless power supply device including a power supply area, a primary coil, which generates a power transmission oscillating signal, and a primary authentication coil, which generates an authentication oscillating signal and includes a first primary authentication coil and a second primary authentication coil that are connected in series to generate magnetic fluxes in opposite directions, wherein the primary coil is wound around a core projecting from a first magnetic body, the first magnetic body having a shape in conformance with the contour of the power supply area, the primary coil is arranged in the middle of the power supply area while the first primary authentication coil and the second primary authentication coil are arranged in the power supply area at symmetrical locations with the primary coil arranged in between, the primary coil partially overlapping each of the first primary authentication coil and the second primary authentication coil in a plan view, and the first and second primary authentication coils each including a portion that does not overlap the primary coil in a plan view, wherein the power reception device is arranged in an electric appliance including at least one power reception area, the power reception device comprising:

a secondary coil and a secondary authentication coil that correspond to the power reception area, wherein

the secondary authentication coil transmits an authentication signal to the primary authentication coil in response to the authentication oscillating signal generated by the primary authentication coil,

the secondary coil generates secondary power with the power transmission oscillating signal from the primary coil, and the secondary coil and the secondary authentication coil are arranged in the power reception area at different locations;

a first modulation wave signal generation circuit that generates a first modulation wave signal from the power transmission oscillating signal received by the secondary coil, wherein the first modulation wave signal reflects a variation in a magnetic flux between the primary coil and the secondary coil;

a first load modulation signal generation circuit that generates a power transmission load modulation signal by modulating the power transmission oscillating signal with the first modulation wave signal;

a second modulation wave signal generation circuit that generates a second modulation wave signal from the authentication oscillating signal received by the secondary authentication coil, wherein the second modulation wave signal reflects a variation in a magnetic flux between the primary authentication coil and the secondary authentication coil; and

a second load modulation signal generation circuit generating an authentication load modulation signal by modulating the authentication oscillating signal with the second modulation wave signal,

wherein the secondary coil is wound around a core projecting from a second magnetic body, the second magnetic body having a shape in conformance with the contour of the power reception area,

the secondary authentication coil includes a first secondary authentication coil and a second secondary authentication coil that are connected in series to generate magnetic fluxes in opposite directions, and

the secondary coil is arranged in the middle of the power reception area while the first secondary authentication coil and the second secondary authentication coil are arranged in the power reception area at symmetrical locations with the secondary coil arranged in between, the secondary coil partially overlapping each of the first secondary authentication coil and the second secondary authentication coil in a plan view, and the first and second secondary authentication coils each including a portion that does not overlap the secondary coil in a plan view.

13. The power reception device according to claim 11, wherein

the secondary coil is arranged at an upper side of the secondary authentication coil so that the secondary authentication coil is proximal to the contactless power supply device, and

the secondary coil is wound around the core projecting downward from the second magnetic body having a larger coil area than the secondary coil.

12. A power reception device for use with a contactless power supply device including a power supply area, a primary coil, which generates a power transmission oscillating signal, and a primary authentication coil, which generates an authentication oscillating signal and includes a first primary authentication coil and a second primary authentication coil that are connected in series to generate magnetic fluxes in opposite directions, wherein the primary coil is wound around a core projecting from a first magnetic body, the first magnetic body having a shape in conformance with the contour of the power supply area, the primary coil is arranged in the middle of the power supply area while the first primary authentication coil and the second primary authentication coil are arranged in the power supply area at symmetrical locations with the primary coil arranged in between, the primary coil partially overlapping each of the first primary authentication coil and the second primary authentication coil in a plan view, and the first and second primary authentication coils each including a portion that does not overlap the primary coil in a plan view, wherein the power reception device is arranged in an electric appliance including at least one power reception area, the power reception device comprising:

a secondary coil and a secondary authentication coil that correspond to the power reception area, wherein

the secondary authentication coil transmits an authentication signal to the primary authentication coil in response to the authentication oscillating signal generated by the primary authentication coil,

the secondary coil generates secondary power with the power transmission oscillating signal from the primary coil, and the secondary coil and the secondary authentication coil are arranged in the power reception area at different locations;

a first modulation wave signal generation circuit that generates a first modulation wave signal from the power transmission oscillating signal received by the secondary coil, wherein the first modulation wave signal reflects a variation in a magnetic flux between the primary coil and the secondary coil;

a first load modulation signal generation circuit that generates a power transmission load modulation signal by modulating the power transmission oscillating signal with the first modulation wave signal;

a second modulation wave signal generation circuit that generates a second modulation wave signal from the authentication oscillating signal received by the secondary authentication coil, wherein the second modulation wave signal reflects a variation in a magnetic flux between the primary authentication coil and the secondary authentication coil; and

a second load modulation signal generation circuit generating an authentication load modulation signal by modulating the authentication oscillating signal with the second modulation wave signal,

wherein

the secondary coil includes a first secondary coil and a second secondary coil that are arranged in series to generate magnetic fluxes in opposite directions, with the first and second secondary coils being wound around two cores projecting from a second magnetic body, the second magnetic body having a shape in conformance with the contour of the power reception area, and

the secondary authentication coil is arranged in the middle of the power reception area while the first secondary coil and the second secondary coil are arranged at symmetrical locations with the secondary authentication coil arranged in between, the secondary authentication coil partially overlapping each of the first secondary coil and the second secondary coil in a plan view, and the first and second secondary coils each including a portion that does not overlap the secondary authentication coil in a plan view.

14. A contactless power supply system comprising:

an electric appliance including at least one power reception area and a power reception device; and

a contactless power supply device, wherein

the contactless power supply device includes at least one power supply area, a primary coil, which corresponds to the power supply area and generates a power transmission oscillating signal, and a primary authentication coil, which corresponds to the power supply area and generates an authentication oscillating signal,

the power reception device includes a secondary coil, which corresponds to the power reception area and generates secondary power in response to the power transmission oscillating signal, and a secondary authentication coil, which corresponds to the power reception area and generates an authentication signal in response to the authentication oscillating signal,

the contactless power supply device includes

a first envelope detection circuit that converts a power transmission load modulation signal into a first load modulation signal by detecting an envelope of the power transmission load modulation signal when the primary coil receives the power transmission load modulation signal reflecting a variation in a magnetic flux between the primary coil and the secondary coil resulting from the power transmission oscillating signal generated by the primary coil,

a second envelope detection circuit converting an authentication load modulation signal into a second load modulation signal by detecting an envelope of the authentication load modulation signal when the primary authentication coil receives the authentication load modulation signal reflecting a variation in a magnetic flux between the primary authentication coil and the secondary authentication coil resulting from the authentication oscillating signal generated by the primary authentication coil, and

a system controller that determines whether or not a metal foreign object is present in the power supply area based on the first load modulation signal provided from the first envelope detection circuit and the second load modulation signal provided from the second envelope detection circuit, and the power reception device includes

a first modulation wave signal generation circuit that generates a first modulation wave signal from the power transmission oscillating signal received by the secondary coil, wherein the first modulation wave signal reflects a variation in a magnetic flux between the primary coil and the secondary coil,

a first load modulation signal generation circuit that generates the power transmission load modulation signal by modulating the power transmission oscillating signal with the first modulation wave signal,

a second modulation wave signal generation circuit generating a second modulation wave signal from the authentication oscillating signal received by the secondary authentication coil, and

a second load modulation signal generation circuit generating the authentication load modulation signal by modulating the authentication oscillating signal with the second modulation wave signal,

wherein

the primary coil is wound around a core projecting from a first magnetic body, the first magnetic body having a shape in conformance with the contour of the power supply area,

the primary authentication coil includes a first primary authentication coil and a second primary authentication coil that are connected in series to generate magnetic fluxes in opposite directions,

the primary coil is arranged in the middle of the power supply area while the first primary authentication coil and the second primary authentication coil are arranged in the power supply area at symmetrical locations with the primary coil arranged in between, the primary coil partially overlapping each of the first primary authentication coil and the second primary authentication coil in a plan view, and the first and second primary authentication coils each including a portion that does not overlap the primary coil in a plan view,

the secondary coil is wound around a core projecting from a second magnetic body, the second magnetic body having a shape in conformance with the contour of the power reception area,

the secondary authentication coil includes a first secondary authentication coil and a second secondary authentication coil that are connected in series to generate magnetic fluxes in opposite directions, and

the secondary coil is arranged in the middle of the power reception area while the first secondary authentication coil and the second secondary authentication coil are arranged in the power reception area at symmetrical locations with the secondary coil arranged in between, the secondary coil partially overlapping each of the first secondary authentication coil and the second secondary authentication coil in a plan view, and the first and second secondary authentication coils each including a portion that does not overlap the secondary coil in a plan view.

15. A contactless power supply system comprising:

an electric appliance including at least one power reception area and a power reception device; and

a contactless power supply device, wherein

the contactless power supply device includes at least one power supply area, a primary coil, which corresponds to the power supply area and generates a power transmission oscillating signal, and a primary authentication coil, which corresponds to the power supply area and generates an authentication oscillating signal,

the power reception device includes a secondary coil, which corresponds to the power reception area and generates secondary power in response to the power transmission oscillating signal, and a secondary authentication coil, which corresponds to the power reception area and generates an authentication signal in response to the authentication oscillating signal,

the contactless power supply device includes

a first envelope detection circuit that converts a power transmission load modulation signal into a first load modulation signal by detecting an envelope of the power transmission load modulation signal when the primary coil receives the power transmission load modulation signal reflecting a variation in a magnetic flux between the primary coil and the secondary coil resulting from the power transmission oscillating signal generated by the primary coil,

a second envelope detection circuit converting an authentication load modulation signal into a second load modulation signal by detecting an envelope of the authentication load modulation signal when the primary authentication coil receives the authentication load modulation signal reflecting a variation in a magnetic flux between the primary authentication coil and the secondary authentication coil resulting from the authentication oscillating signal generated by the primary authentication coil, and

a system controller that determines whether or not a metal foreign object is present in the power supply area based on the first load modulation signal provided from the first envelope detection circuit and the second load modulation signal provided from the second envelope detection circuit, and

the power reception device includes

a first modulation wave signal generation circuit that generates a first modulation wave signal from the power transmission oscillating signal received by the secondary coil, wherein the first modulation wave signal reflects a variation in a magnetic flux between the primary coil and the secondary coil,

a first load modulation signal generation circuit that generates the power transmission load modulation signal by modulating the power transmission oscillating signal with the first modulation wave signal,

a second modulation wave signal generation circuit generating a second modulation wave signal from the authentication oscillating signal received by the secondary authentication coil, and

a second load modulation signal generation circuit generating the authentication load modulation signal by modulating the authentication oscillating signal with the second modulation wave signal,

wherein the primary coil includes a first primary coil and a second primary coil that are connected in series to generate magnetic fluxes in opposite directions,

the first and second primary coils are wound around two cores projecting from a first magnetic body, the first magnetic body having a shape in conformance with the contour of the power supply area,

the primary authentication coil is arranged in the middle of the power supply area while the first primary coil and the second primary coil are arranged in the power supply area at symmetrical locations with the primary authentication coil arranged in between, the primary authentication coil partially overlapping each of the first primary coil and the second primary coil in a plan view, and the first and second primary coils each including a portion that does not overlap the primary authentication coil in a plan view,

the secondary coil includes a first secondary coil and a second secondary coil that are connected in series to generate magnetic fluxes in opposite directions,

the first and second secondary coils are wound around two cores projecting from a second magnetic body, the second magnetic body having a shape in conformance with the contour of the power reception area, and

the secondary authentication coil is arranged in the middle of the power reception area while the first secondary coil and the second secondary coil are arranged in the power reception area at symmetrical locations with the secondary authentication coil arranged in between, the secondary authentication coil partially overlapping each of the first secondary coil and the second secondary coil in a plan view, and the first and second secondary coils each including a portion that does not overlap the secondary authentication coil in a plan view.