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. An apparatus comprising:
a resonant circuit including a coil and one or more capacitors;
a signal source configured to generate a signal that is input into the resonant circuit;
a Q-factor measuring section configured to (a) measure a first voltage at a first terminal of the coil when the signal-source signal is input into the resonant circuit, and (b) obtain a Q-factor of the coil using the measurement of the first voltage; and
a determination section configured to determine whether or not a foreign object exists in close vicinity of the coil by comparing the Q-factor obtained by the Q-factor measuring section with a predetermined reference value.
2. The apparatus of claim 1 , wherein the signal-source comprises:
a pulse generator with circuitry to generate signal pulses; and
a resistor to generate the signal based on the signal pulses.
3. The apparatus of claim 1 , further comprising a control section operative to stop transmission of electric power by a power transmitter to a power receiver in response to detection of a foreign object in the close vicinity of the coil.
4. The apparatus of claim 1 , wherein the frequency of the signal is equal to a resonance frequency of the resonant circuit.
5. The power transmitting apparatus of claim 4 , wherein the frequency of the signal is equal to a resonance frequency of the resonant circuit.
6. The power transmitting apparatus of claim 4 configured to obtain the Q-factor of the coil before power transmission occurs.
7. The power transmitting apparatus of claim 4 , configured to determine the existence of a foreign object in the close vicinity of the coil when the Q-factor obtained by the Q-factor measuring section is lower than the predetermined reference value.
8. The apparatus of claim 1 , wherein the Q-factor measuring section is configured to measure the first voltage twice, and obtain the Q-factor using the two measurements of the first voltage.
9. The apparatus of claim 8 , wherein the Q-factor measuring section is configured to measure the first voltage at a first time and at a second time lagging behind the first time by a predetermined time period.
10. The apparatus of claim 8 , wherein the Q-factor measuring section is configured to obtain the Q-factor using Equation 3:
Q
=
π
f
·
t
2
-
t
1
1
n
(
V
1
V
2
)
where, f is a resonance frequency of the resonant circuit, V 1 is the first measurement of the first voltage at a point in time t 1 , and V 2 is the second measurement of the first voltage a point in time t 2 .
11. The apparatus of claim 8 , wherein the Q-factor measuring section is configured to measure the first voltage at a second time when the first voltage is in a predetermined range including the first voltage at a first time.
12. The apparatus of claim 11 , wherein the predetermined range set for the first voltage at the second time is a range of 40% to 25% of the first voltage at the first time.
13. The apparatus of claim 8 , wherein, the Q-factor measuring section is configured to measure the first voltage again at a second point of time after the lapse of a determined time period as when the first voltage has not entered a predetermined range not including the first voltage at a first point in time within the predetermined time period.
14. The apparatus of claim 13 , wherein the predetermined range set for the first voltage at the second point in time is only in a range of 40% to 25% of the first voltage at the first point in time.
15. The apparatus of claim 8 , wherein the Q-factor measuring section is configured to obtain the Q-factor using Equation 15:
Q
=
π
·
vibration
-
count
1
n
(
V
1
V
2
)
where, V 1 is the first measurement of the first voltage at a point in time t 1 , V 2 is the second measurement of the first voltage a point in time t 2 , and vibration-count is a count of vibrations in a constant-amplitude signal related to the first voltage.
16. The apparatus of claim 1 , wherein the Q-factor measuring section is configured to measure a second voltage at a second terminal of the coil when the signal-source signal is input into the resonant circuit, and obtain the Q-factor using the measurements of the measurements of the first voltage and the second voltage.
17. A power transmitting apparatus comprising:
a resonant circuit including a coil and one or more capacitors;
a signal-source configured to input a signal to the resonant circuit;
a Q-factor measuring section configured to measure a first voltage at a first terminal of the coil and a second voltage at a second terminal of the coil when the signal-source signal is input into the resonant circuit, and to obtain a Q-factor of the coil using the first voltage and the second voltage;
a determination section configured to determine whether or not a foreign object exists in close vicinity of the coil by comparing the Q-factor obtained by the Q-factor measuring section with a predetermined reference value; and
a power transmitting section configured to transmit electric power wirelessly to a power receiving apparatus.
18. The power transmitting apparatus of claim 17 , wherein the signal-source comprises:
a pulse generator with circuitry to generate signal pulses; and
a resistor to generate the signal based on the signal pulses.
19. The power transmitting apparatus of claim 17 , further comprising a control section operative to stop transmission of electric power by the power transmitter to the power receiver in response to detection of a foreign object in the close vicinity of the coil.
20. A method comprising:
providing a resonant circuit including (a) a coil and one or more capacitors, (b) a signal-source configured to generate a signal that is input into the resonant circuit, (c) a Q-factor measuring section configured to (1) measure a first voltage at a first terminal of the coil when the signal-source signal is input into the resonant circuit, and (2) obtain a Q-factor of the coil using the measurement of the first voltage, and (c) a determination section configured to determine whether or not a foreign object exists in close vicinity of the coil by comparing the Q-factor obtained by the Q-factor measuring section with a predetermined reference value;
inputting the signal-source signal into the resonant circuit;
measuring the first voltage at the first terminal;
obtaining a Q-factor of the coil using the measurement of the first voltage; and
determining whether or not a foreign object exists in close vicinity of the coil by comparing the Q-factor obtained by the Q-factor measuring section with a predetermined reference value.
21. A power transmitting apparatus comprising:
providing a resonant circuit including (a) a coil and one or more capacitors, (b) a signal-source configured to input a signal to the resonant circuit, (c) a Q-factor measuring section configured to measure a first voltage at a first terminal of the coil and measure a second voltage at a second terminal of the coil when the signal-source signal is input into the resonant circuit, and to obtain a Q-factor of the coil using the first voltage and the second voltage, (d) a determination section configured to determine whether or not a foreign object exists in close vicinity of the coil by comparing the Q-factor obtained by the Q-factor measuring section with a predetermined reference value, and (e) a power transmitting section configured to transmit electric power wirelessly to a power receiving apparatus;
inputting the signal-source signal into the resonant circuit;
measuring the first voltage at the first terminal;
measuring the second voltage at the second terminal;
obtaining a Q-factor of the coil using the measurement of the first voltage and the measurement of the second voltage; and
determining whether or not a foreign object exists in close vicinity of the coil by comparing the Q-factor obtained by the Q-factor measuring section with a predetermined reference value.