Detection apparatus, power receiving apparatus, non-contact power transmission system and detection method
Disclosed herein is a detection apparatus including: a resonant circuit provided with a Q-factor measurement coil and one or more capacitors to serve as a circuit for receiving pulses; a response-waveform detecting section configured to detect the waveform of a response output by the resonant circuit in response to the pulses; and a Q-factor measuring section configured to measure a Q factor of the resonant circuit from the response waveform detected by the response-waveform detecting section. It is possible to increase the precision of detection of a metallic foreign substance existing between a power transmitting side and a power receiving side.
1. A detection apparatus comprising:
a pulse generator with circuitry to generate pulses;
a resonant circuit including a Q-factor measurement coil and one or more capacitors, the resonant circuit configured to receive the pulses from the pulse generator;
a response-waveform detecting section configured to detect-a response waveform that is output by the resonant circuit in response to the pulses; and
a Q-factor measuring section configured to measure a Q factor of the resonant circuit from the response waveform detected by the response-waveform detecting section,
wherein,
the response waveform detected by the response-waveform detecting section is a time-domain response waveform,
the Q-factor measuring section measures the Q factor of the resonant circuit from a first amplitude obtained from the time-domain response waveform at a first time and a second amplitude obtained from the time-domain response waveform at a second time, the second time lagging behind the first time by a time period determined in advance, and
when a resonance frequency of the resonant circuit is denoted by f, the first amplitude obtained from the time-domain response waveform at the first time t 1 is denoted by V 1 , and the second amplitude obtained from the time-domain response waveform at the second time t 2 is denoted by V 2 , the Q-factor measuring section measures the Q factor in accordance with the following equation:
Q=πf ·( t 2 −t 1 )/ln( V 1 /V 2 ).
2. The detection apparatus according to claim 1 , wherein the Q-factor measuring section measures the Q factor when the second amplitude obtained from the time-domain response waveform is in a predetermined amplitude range not including the first amplitude.
3. The detection apparatus according to claim 2 , wherein the predetermined amplitude range set for the second amplitude obtained from the time-domain response waveform is a range of 40% to 25% of the first amplitude obtained from the time-domain response waveform.
4. The detection apparatus according to claim 1 , wherein, if the second amplitude obtained from the time-domain response waveform has not entered a predetermined amplitude range not including the first amplitude within a predetermined time period, the Q-factor measuring section measures the Q factor by detecting the second amplitude at a point of time after a lapse of the predetermined time period.
5. The detection apparatus according to claim 1 , wherein the pulses applied to said resonant circuit are a single pulse.
6. A detection apparatus comprising:
a pulse generator with circuitry to generate pulses;
a resonant circuit including a Q-factor measurement coil and one or more capacitors, the resonant circuit configured to receive the pulses from the pulse generator;
a response-waveform detecting section configured to detect-a response waveform that is output by the resonant circuit in response to the pulses; and
a Q-factor measuring section configured to measure a Q factor of the resonant circuit from the response waveform detected by the response-waveform detecting section,
wherein,
the response waveform detected by the response-waveform detecting section is a time-domain response waveform, and
when a number of vibrations occurring within a predetermined time period of the time-domain response waveform is denoted by “vibration-count,” an amplitude obtained at a start of the predetermined time period is denoted by V 1 , and an amplitude obtained at an end of the predetermined time period is denoted by V 2 , the Q-factor measuring section measures the Q factor in accordance with the following equation:
Q =π·vibration-count/ln( V 1 /V 2 ).
7. A detection apparatus comprising:
a pulse generator with circuitry to generate pulses;
a resonant circuit including a Q-factor measurement coil and one or more capacitors, the resonant circuit configured to receive the pulses from the pulse generator;
a response-waveform detecting section configured to detect-a response waveform that is output by the resonant circuit in response to the pulses;
a Q-factor measuring section configured to measure a Q factor of the resonant circuit from the response waveform detected by the response-waveform detecting section; and
a determination section configured to determine a state of electromagnetic coupling between the Q-factor measurement coil and an external apparatus by comparing the Q factor measured by the Q-factor measuring section with a predetermined reference value.
8. The detection apparatus according to claim 7 , wherein the state of electromagnetic coupling between the Q-factor measurement coil and the external apparatus indicates existence/non-existence of a circuit including any coil or a conductor between said Q-factor measurement coil and the external apparatus.
9. The detection apparatus according to claim 8 , further comprising a control section configured to execute control to stop output of a power transmission signal from the external apparatus upon determining that a circuit including any coil or a conductor exists between the Q-factor measurement coil and the external apparatus.
10. A detection apparatus comprising:
a pulse generator with circuitry to generate pulses;
a resonant circuit including a Q-factor measurement coil and one or more capacitors, the resonant circuit configured to receive the pulses from the pulse generator;
a response-waveform detecting section configured to detect-a response waveform that is output by the resonant circuit in response to the pulses; and
a Q-factor measuring section configured to measure a Q factor of the resonant circuit from the response waveform detected by the response-waveform detecting section,
wherein,
the response waveform detected by the response-waveform detecting section is a frequency-domain response waveform, and
the Q-factor measuring section measures the Q factor from a bandwidth between two frequencies at each of which an amplitude of the frequency-domain response waveform is 1/√2 times an amplitude at a resonance frequency of a series resonant circuit, the series resonant circuit including one or more of the capacitors and the Q-factor measurement coil.
11. A detection apparatus comprising:
a pulse generator with circuitry to generate pulses;
a resonant circuit including a Q-factor measurement coil and one or more capacitors, the resonant circuit configured to receive the pulses from the pulse generator;
a response-waveform detecting section configured to detect-a response waveform that is output by the resonant circuit in response to the pulses; and
a Q-factor measuring section configured to measure a Q factor of the resonant circuit from the response waveform detected by the response-waveform detecting section,
wherein,
the response waveform detected by the response-waveform detecting section is a frequency-domain response waveform, and
the Q-factor measuring section measures the Q factor from a bandwidth between two frequencies at each of which an amplitude of the frequency-domain response waveform is √2 times an amplitude at a resonance frequency of a parallel resonant circuit, the parallel resonant circuit including one or more of the capacitors and the Q-factor measurement coil.
12. A power receiving apparatus comprising:
a power receiving coil electromagnetically coupled to an external apparatus;
a power receiving section configured to receive electric power from the external apparatus through the power receiving coil;
a pulse generator with circuitry to generate pulses;
a resonant circuit including a Q-factor measurement coil and one or more capacitors in a low pass filter configuration, the resonant circuit configured to receive the pulses from the pulse generator;
a response-waveform detecting section configured to detect a response waveform that is output by the resonant circuit in response to the pulses; and
a Q-factor measuring section configured to measure a Q factor of the resonant circuit from the response waveform detected by the response-waveform detecting section.
13. A non-contact power transmission system comprising:
a power transmitting apparatus configured to transmit electric power by adoption of a non-contact transmission technique; and
a power receiving apparatus configured to receive the electric power from said power transmitting apparatus,
wherein, the power receiving apparatus includes
a power receiving coil electromagnetically coupled to a power transmitting coil of the power transmitting apparatus,
a power receiving section configured to receive electric power from the power transmitting apparatus through the power receiving coil,
a resonant circuit including a Q-factor measurement coil and one or more capacitors in a low pass filter configuration, the resonant circuit configured to receive the pulses from the pulse generator,
a response-waveform detecting section configured to detect a response waveform that is output by the resonant circuit in response to the pulses, and
a Q-factor measuring section configured to measure a Q factor of the resonant circuit from the response waveform detected by the response-waveform detecting section.
14. A detection method comprising:
generating pulses via circuitry of a pulse generator;
applying pulses to a resonant circuit that includes a Q-factor measurement coil and one or more capacitors in a low pass filter configuration;
driving a response-waveform detecting section to detect a response waveform that is output by the resonant circuit in response to the pulses; and
driving a Q-factor measuring section to measure a Q factor of the resonant circuit from the response waveform detected by the response-waveform detecting section
wherein,
the response waveform detected by the response-waveform detecting section is a time-domain response waveform,
the Q-factor measuring section measures the Q factor of the resonant circuit from a first amplitude obtained from the time-domain response waveform at a first time and a second amplitude obtained from the time-domain response waveform at a second time, the second time lagging behind the first time by a time period determined in advance, and
when a resonance frequency of the resonant circuit is denoted by f, the first amplitude obtained from the time-domain response waveform at the first time t 1 is denoted by V 1 , and the second amplitude obtained from the time-domain response waveform at the second time t 2 is denoted by V 2 , the Q-factor measuring section measures the Q factor in accordance with the following equation:
Q=πf ·( t 2 −t 1 )/ln( V 1 /V 2 ).