Method for detecting metal foreign object on contactless power supply device, contactless power supply device, contactless power reception device, and contactless power supply system
View Patent ↗With a metal foreign object detecting method, a metal detection circuit arranged in a contactless power supply device transmits an oscillation signal to a modulation circuit of an electric appliance. The modulation circuit generates a square wave pulse signal from the oscillation signal. The cycle of the oscillation signal received by the modulation circuit changes in accordance with whether or not a metal piece is present. The modulation circuit modulates the square wave pulse signal to generate a modulated wave signal and transmits the modulated wave signal to the metal detection circuit of the power supply device. The metal detection circuit demodulates the modulated wave signal and determines whether or not a metal piece is present based on the cycle of the demodulated signal corresponding to the square wave pulse signal.
1. A method for detecting whether or not a metal foreign object is present on a contactless power supply device that supplies power to a power reception device included in an electrical appliance using an electromagnetic induction phenomenon, the method comprising:
transmitting an oscillation signal from the contactless power supply device to the power reception device;
detecting, from the oscillation signal received by the power reception device, a modulating wave based on a change in magnetic flux caused by the presence of a metal foreign object;
generating a modulated wave signal by modulating a carrier signal in accordance with the modulating wave to transmit the modulating wave to the contactless power supply device, and transmitting the modulated wave signal from the power reception device to the contactless power supply device; and
receiving the modulated wave signal transmitted from the power reception device with the contactless power supply device, and determining whether or not a metal foreign object is present based on comparison between a reference cycle and the cycle of a demodulated signal demodulated from the modulated wave signal, the cycle of the demodulated signal corresponding to the cycle of the modulating wave.
2. The metal foreign object detecting method according to claim 1 , wherein
the modulating wave is a square wave pulse signal derived from the oscillation signal received by the power reception device and having a cycle changed based on a change in magnetic flux caused by the presence of a metal foreign object,
the modulated wave signal is generated by modulating an amplitude of the carrier signal in proportion to the square wave pulse signal, and
the demodulated signal is a square wave pulse signal generated by detecting an envelope of the modulated wave signal.
3. The metal foreign object detecting method according to claim 1 , wherein the carrier signal is the oscillation signal transmitted from the contactless power supply device to the power reception device.
4. The metal foreign object detecting method according to claim 1 , wherein
the carrier signal is an electromagnetic wave signal generated based on a supplying current supplied to a secondary coil included in the power reception device, using an electromagnetic induction phenomenon, from a primary coil arranged in the contactless power supply device, and
the modulated wave signal is obtained by superimposing the modulating wave onto the electromagnetic wave signal.
5. A contactless power supply device that supplies power to a power reception device included in electric appliance using an electromagnetic induction phenomenon, the contactless power supply device comprising:
an oscillation circuit that transmits an oscillation signal to the power reception device;
a wave detection circuit that receives, from the power reception device receiving the oscillation signal, a modulated wave signal obtained by modulating the oscillation signal with a modulating wave based on a change in magnetic flux, detects the modulated wave signal, and demodulates the modulated wave signal detected by the power reception device;
a frequency detection circuit that detects a frequency of the modulating wave demodulated by the wave detection circuit; and
a determination circuit that determines whether or not a metal foreign object is present based on comparison between a reference cycle and the cycle corresponding to the frequency of the demodulated modulating wave detected by the frequency detection circuit, the cycle of the demodulated modulating wave corresponding to the cycle of the modulating wave.
6. The contactless power supply device according to claim 5 , wherein
the modulating wave is a square wave pulse signal derived from the oscillation signal received by the power reception device and having a cycle changed based on a change in magnetic flux caused by the presence of a metal foreign object,
the modulated wave signal is generated by modulating an amplitude of the carrier signal in proportion to the square wave pulse signal, and
the wave detection circuit is configured to demodulate the square wave pulse signal by detecting an envelope of the modulated wave signal,
the frequency detection circuit is configured to detect a cycle of the square wave pulse signal demodulated by the wave detection circuit, and
the determination circuit determines whether a metal foreign object is present based on the cycle of the square wave pulse signal detected by the frequency detection circuit.
7. The contactless power supply device according to claim 6 , wherein the carrier signal is the oscillation signal transmitted from the oscillation circuit to the power reception device.
8. The contactless power supply device according to claim 5 , wherein the reference cycle is prestored in the determination circuit.
9. A contactless power supply system comprising a power reception device, which is included in an electric appliance, and a contactless power supply device, which supplies power to the power reception device using an electromagnetic induction phenomenon, wherein
the contactless power supply device includes
an oscillation circuit that transmits, to the power reception device, an oscillation signal having a fixed frequency used to detect whether or not a metal foreign object is present,
a wave detection circuit that receives, from the power reception device receiving the oscillation signal, a modulated wave signal obtained by modulating the oscillation signal with a modulating wave based on a change in magnetic flux, detects the modulated wave signal, and demodulates the modulated wave signal detected by the power reception device,
a frequency detection circuit that detects a frequency of a demodulated modulating wave demodulated by the wave detection circuit, and
a determination circuit that determines whether a metal foreign object is present based on comparison between a reference cycle and the cycle corresponding to the frequency of the demodulated modulating wave detected by the frequency detection circuit, the cycle of the demodulated modulating wave corresponding to the cycle of the modulating wave, and
the power reception device includes
an oscillation signal receiving circuit that receives the oscillation signal transmitted from the contactless power supply device,
a modulating wave signal generation circuit that generates, from the oscillation signal received by the oscillation signal receiving circuit, the modulating wave, and
a modulated wave signal generation circuit that generates a modulated wave signal by modulating a carrier signal in accordance with the modulating wave to transmit the modulating wave to the contactless power supply device.
10. The contactless power supply system according to claim 9 , wherein
the modulating wave is a square wave pulse signal,
the modulating wave signal generation circuit of the power reception device is configured to generate the square wave pulse signal, from the received oscillation signal, with a cycle changed based on a change in magnetic flux caused by the presence of a metal foreign object,
the modulated wave signal is generated by modifying an amplitude of the carrier signal in proportion to the square wave pulse signal,
the modulated wave signal generation circuit of the power reception device is configured to generate the modulated wave signal by modulating an amplitude of the carrier signal in proportion to the square wave pulse signal,
the wave detection circuit of the contactless power supply device is configured to demodulate the square wave pulse signal by detecting an envelope of the modulated wave signal,
the frequency detection circuit of the contactless power supply device is configured to detect a cycle of the square wave pulse signal demodulated by the wave detection circuit, and
the determination circuit of the contactless power supply device determines whether or not a metal foreign object is present based on the cycle of the square wave pulse signal detected by the frequency detection circuit.
11. The contactless power supply system according to claim 9 , wherein the carrier signal is the oscillation signal transmitted from the oscillation circuit of the contactless power supply device to the oscillation signal receiving circuit of the power reception device.
12. The contactless power supply device according to claim 9 , wherein the reference cycle is prestored in the determination circuit.