METAL DETECTION METHOD, METAL DETECTION DEVICE, METAL DETECTION METHOD FOR WIRELESS POWER SUPPLY DEVICE, AND WIRELESS POWER SUPPLY DEVICE

• US 20150028875A1
• Filed: 02/28/2013
• Published: 01/29/2015
• Est. Priority Date: 03/09/2012
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Hyodo, Satoshi, Irie, Kenichi, Kawada, Masashi, Kohara, Hiroshi
• Granted Patent: US 9,618,645 B2
• Time in Patent Office: Days
• US Class Current: 324/345
• 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: H02J 5/005 with inductive power transfer for charging H02J7/025
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 7/0068 Battery or charger load switching, e.g. concurrent charging and load supply H02J7/0013 takes precedence
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

Provided are a metal detection method, a metal detection device, a metal detection method for a wireless power supply device, and a wireless power supply device which are capable of accurately detecting whether an object is a metal or a nonmetal. An oscillation circuit (10) oscillates and produces a sine wave having a single fundamental frequency, and excites a metal detection coil (Ls) by the oscillation current (It) of the sine wave. An electromagnetic wave of the sine wave having the single fundamental frequency is radiated from the metal detection coil (Ls). A high-pass filter circuit (11a) receives the oscillation current (It), removes the fundamental frequency component from the oscillation current (It), and extracts a high-harmonic component of the fundamental frequency. A comparison circuit (12) determines the presence or absence of a metal.

Claims

1. A method for exciting a metal detection coil arranged in a metal detection area to use an electromagnetic wave radiated from the metal detection coil and detect whether or not metal exists in the metal detection area, the method comprising:

exciting the metal detection coil with a sinusoidal oscillating current having a single fundamental frequency to radiate an electromagnetic wave from the metal detection coil; and

detecting whether or not metal exists in the metal detection area from a change in the fundamental frequency in the oscillating current flowing to the metal detection coil.

2. The method according to claim 1, wherein the detecting whether or not metal exists in the metal detection area includes detecting that metal exists in the metal detection area when a harmonic of the fundamental frequency is generated in the oscillating current.

3. A metal detection device comprising:

a metal detection coil arranged in a metal detection area, wherein the metal detection coil is excited, and an electromagnetic wave radiated from the metal detection coil is used to detect whether or not metal exists in the metal detection area;

an oscillation circuit that generates a sinusoidal oscillating current having a single fundamental frequency, wherein the oscillation circuit supplies the oscillating current to the metal detection coil to excite the metal detection coil;

a harmonic level detection circuit that detects a harmonic component of the fundamental frequency component of the oscillating current and generates a detection signal;

a comparison circuit that compares a signal level of the detection signal and a reference value, which is set in advance; and

a processing circuit that determines whether or not metal exists in the metal detection area based on a comparison result, wherein when determining that metal exists in the metal detection area, the processing circuit drives a notification unit to issue a notification indicating detection of metal.

4. The metal detection device according to claim 3, wherein the harmonic level detection circuit includes

a filter circuit that filters a frequency component higher than the fundamental frequency from the oscillating current to generate a filtered signal, and

an amplification circuit that amplifies the filtered signal from the filter circuit to generate the detection signal.

5. The metal detection device according to claim 3, wherein the harmonic level detection circuit includes a high speed Fourier transformation circuit that extracts a frequency component higher than the fundamental frequency from the oscillating current to generate the detection signal.

6. The metal detection device according to claim 3, wherein the notification unit includes an indication lamp.

7. A metal detection method using a contactless power supplying device including a primary coil arranged in a power supplying area, wherein when an electric instrument is placed in the power supplying area, the contactless power supplying device excites the primary coil arranged in the power supplying area to cause electromagnetic induction at a secondary coil of a power receiving device arranged in the electric instrument and supply power to the electric instrument, and the contactless power supplying device includes a metal detection coil arranged in the power supplying area, the metal detection method comprising:

exciting the metal detection coil with a sinusoidal oscillating current having a single fundamental frequency to radiate an electromagnetic wave from the metal detection coil; and

detecting whether or not metal exists in the power supplying area from a change in a fundamental frequency of the oscillating current flowing to the metal detection coil.

8. The metal detection method using the contactless power supplying device according to claim 7, wherein the detecting whether or not metal exists in the power supplying area includes detecting that metal exists in the power supplying area when a harmonic of the fundamental frequency is generated in the oscillating current.

9. A contactless power supplying device comprising:

a primary coil arranged in a power supplying area, wherein when an electric instrument is placed in the power supplying area, the primary coil arranged in the power supplying area is excited to cause electromagnetic induction at a secondary coil of a power receiving device arranged in the electric instrument to supply power to the electric instrument;

a metal detection coil arranged in the power supplying area;

an oscillation circuit that generates a sinusoidal oscillating current having a single fundamental frequency and supplies the oscillating current to the metal detection coil to excite the metal detection coil;

a harmonic level detection circuit that detects a harmonic component of the fundamental frequency component of the oscillating current and generates a detection signal;

a comparison circuit that compares a signal level of the detection signal and a reference value, which is set in advance; and

a control circuit that determines whether or not metal exists in the power supplying area based on a comparison result, wherein when determining that metal exists in the power supplying area, the control circuit causes the oscillation circuit to stop the excitation of the metal detection coil.

10. The contactless power supplying device according to claim 9, wherein the harmonic level detection circuit includes

a filter circuit that filters a frequency component higher than the fundamental frequency from the oscillating current to generate a filtered signal, and

an amplification circuit that amplifies the filtered signal from the filter circuit and generates the detection signal.

11. The contactless power supplying device according to claim 9, wherein the harmonic level detection circuit includes a high speed Fourier transformation circuit that extracts a frequency component higher than the fundamental frequency from the oscillating current and generates the detection signal.

12. The contactless power supplying device according to claim 9, wherein

the power supplying area is one of a plurality of separate power supplying areas,

the primary coil is one of a plurality of primary coils respectively arranged in the plurality of power supplying areas,

the metal detection coil is one of a plurality of metal detection coils respectively arranged in the plurality of power supplying areas,

the oscillation circuit is one of a plurality of oscillation circuits respectively arranged in the plurality of power supplying areas,

the harmonic level detection circuit is one of a plurality of harmonic level detection circuits respectively arranged in the plurality of power supplying areas,

the comparison circuit is one of a plurality of comparison circuits respectively arranged in the plurality of power supplying areas,

the contactless power supplying device includes a plurality of metal detection circuits respectively arranged in the plurality of power supplying areas, and

each of the plurality of metal detection circuits includes the oscillation circuit, the harmonic level detection circuit, and the comparison circuit, and is controlled by the control circuit.

13. The contactless power supplying device according to claim 9, comprising a notification unit that indicates whether or not metal exists in the power supplying area,

wherein the control circuit drives the notification unit based on a comparison result of the comparison circuit.

14. The contactless power supplying device according to claim 13, wherein the notification unit includes an indication lamp.

15. A metal detection method using a contactless power supplying device including a primary coil arranged in a power supplying area, wherein when an electric instrument is placed in the power supplying area, the contactless power supplying device excites a primary coil arranged in the power supplying area and causes electromagnetic induction at a secondary coil of a power receiving device arranged in the electric instrument to supply power to the electric instrument, the metal detection method comprising:

exciting the primary coil with a sinusoidal oscillating current having a single fundamental frequency to radiate an electromagnetic wave from the primary coil; and

detecting whether or not metal exists in the power supplying area from a change in a fundamental frequency of the oscillating current flowing to the primary coil.

16. The metal detection method using the contactless power supplying device according to claim 15, wherein the detecting whether or not metal exists in the power supplying area includes detecting that metal exists in the power supplying area when a harmonic of the fundamental frequency is generated in the oscillating current.

17. A contactless power supplying device comprising:

a primary coil arranged in a power supplying area, wherein when an electric instrument is placed in the power supplying area, the primary coil arranged in the power supplying area is excited to cause electromagnetic induction in a secondary coil of a power receiving device arranged in the electric instrument to supply power to the electric instrument;

an excitation circuit that generates a sinusoidal oscillating current having a single fundamental frequency and supplies the oscillating current to the primary coil to excite the primary coil;

a harmonic level detection circuit that detects a harmonic component of the fundamental frequency component of the oscillating current to generate a detection signal;

a comparison circuit that compares a signal level of the detection signal with a reference value, which is set in advance; and

a processing circuit that determines whether or not metal exists in the power supplying area based on a comparison result, wherein when determining that metal exists in the power supplying area, the processing circuit drives a notification unit to issue a notification indicating detection of metal.

18. The contactless power supplying device according to claim 17, wherein the harmonic level detection circuit includes

a filter circuit that filters a frequency component higher than the fundamental frequency from the oscillating current and generates a filtered signal, and

an amplification circuit that amplifies the filtered signal from the filter circuit and generates the detection signal.

19. The contactless power supplying device according to claim 17, wherein the harmonic level detection circuit includes a high speed Fourier transformation circuit that extracts a frequency component higher than the fundamental frequency from the oscillating current and generates the detection signal.

20. The contactless power supplying device according to claim 17, wherein the notification unit includes at least one of an indication lamp and a buzzer.