WIRELESS POWER FEEDER AND WIRELESS POWER TRANSMISSION SYSTEM
Power is transmitted from a feeding coil L 2 to a receiving coil L 2 by magnetic resonance. A power circuit 200 turns ON/OFF switching transistors Q 1 and Q 2 to feed AC current to an exciting circuit 110 , whereby the AC power is fed from an exciting coil L 1 to a feeding coil L 2 . A phase detection circuit 150 sets the switching transistor Q 2 of the power circuit 200 as a measurement target and detects the phase difference between source-drain current IDS 2 and source-drain voltage VDS 2 from the current phase and voltage phase thereof.
1 . A wireless power feeder for feeding power by wireless from a feeding coil to a receiving coil at the resonance frequency of the feeding coil and receiving coil, comprising:
a power circuit;
the feeding coil;
an exciting coil that is magnetically coupled to the feeding coil and feeds AC power fed from the power circuit to the feeding coil; and
a phase detection circuit that detects the phase difference between the voltage phase and current phase of the AC power fed from the power circuit, wherein
the power circuit includes first and second current paths and makes first and second switches connected in series respectively to the first and second current paths alternately conductive to feed the AC power to the exciting coil, and
the phase detection circuit measures the phase of current passing through both or one of the first and second switches to achieve measurement of the current phase of the AC power.
2 . A wireless power feeder for feeding power by wireless from a feeding coil to a receiving coil at the resonance frequency of the feeding coil and receiving coil, comprising:
a power circuit that feeds AC power to the feeding coil at the drive frequency;
a feeding coil circuit that includes the feeding coil and a capacitor, and resonate at the resonance frequency; and
a phase detection circuit that detects the phase difference between the voltage phase and current phase of the AC power fed from the power circuit, wherein
the power circuit includes first and second current paths and makes first and second switches connected in series respectively to the first and second current paths alternately conductive to feed the AC power to the feeding coil, and
the phase detection circuit measures the phase of current passing through both or one of the first and second switches to achieve measurement of the current phase of the AC power.
3 . The wireless power feeder as claimed in claim 2 , wherein
a primary coil included in the power circuit and a secondary coil included in the feeding coil circuit constitute a coupling transformer, and
AC power is fed from the power circuit to the feeding coil circuit through the coupling transformer.
4 . The wireless power feeder as claimed in claims 1 , further comprising a drive frequency tracking circuit that adjusts the drive frequency of the power circuit so as to reduce the detected phase difference to allow the drive frequency to track the resonance frequency.
5 . The wireless power feeder as claimed in claims 1 , wherein
the first and second switches are each a field-effect transistor.
6 . The wireless power feeder as claimed in claim 5 , wherein
first resistors are connected in series between the source and ground of the first switch and between the source and ground of the second switch, and
the phase detection circuit measures the current phase from a change in voltage applied to the first resistors.
7 . The wireless power feeder as claimed in claim 5 , wherein
the phase detection circuit measures the voltage phase from a change in the source-drain voltage of both or one of the first and second switches.
8 . The wireless power feeder as claimed in claim 7 , wherein
second resistors are connected in parallel to the source-drain of both or one of the first and second switches, and
the phase detection circuit measures the voltage phase from a change in intermediate potential taken from the middle of the second resistors.
9 . The wireless power feeder as claimed in claims 1 , further comprising:
a first waveform rectifier that converts an analog waveform having the same phase as that of a current waveform of the AC power into a digital waveform; and
a second waveform rectifier that converts an analog waveform having the same phase as that of a voltage waveform of the AC power into a digital waveform, wherein
the phase detection circuit compares the edges of two digital waveforms to detect the phase difference.
10 . A wireless power feeder for feeding power by wireless from a feeding coil to a receiving coil at the resonance frequency of the feeding coil and receiving coil, comprising:
a resonance circuit that includes a first coil and a capacitor which are connected in series;
a first switch that controls supply of power fed from a first direction to the resonance circuit;
a second switch that controls supply of power fed from a second direction to the resonance circuit;
a power transmission control circuit that makes the first and second switches alternately conductive to cause the resonance circuit to resonate to transmit AC power from the first coil serving as the feeding coil to the receiving coil;
a second coil that generates inductive current using a magnetic field generated by the AC power; and
a phase detection circuit that detects the phase difference between the voltage phase and current phase of the AC power, wherein
the phase detection circuit measures the phase of the inductive current flowing in the second coil to achieve measurement of the current phase of the AC current.
11 . The wireless power feeder as claimed in claim 10 , wherein
a current path passing through the first and second switches and a current path passing through the resonance circuit are separated by a coupling transformer, and
AC power is fed to the resonance circuit through the coupling transformer.
12 . The wireless power feeder as claimed in claim 10 , further comprising a drive frequency tracking circuit that adjusts the drive frequency of the power transmission control circuit so as to reduce the detected phase difference to allow the drive frequency to track the resonance frequency.
13 . The wireless power feeder as claimed in claims 10 , wherein
the power transmission control circuit feeds the AC power from the first coil to the feeding coil which is a coil different from the first coil to achieve transmission of the AC power from the feeding coil to the receiving coil.
14 . The wireless power feeder as claimed in claims 10 , wherein
the second coil is wounded around a toroidal core, and
a part of the first coil is made to pass through the toroidal core to constitute a coupling transformer by the first and second coils.
15 . The wireless power feeder as claimed in claims 10 , wherein
a resistor is connected in parallel to both ends of the second coil, and
the phase detection circuit measures the current phase from a change in voltage applied to the resistor.
16 . The wireless power feeder as claimed in claims 10 , further comprising:
a first waveform rectifier that converts an analog waveform having the same phase as that of a current waveform of the AC power into a digital waveform; and
a second waveform rectifier that converts an analog waveform having the same phase as that of a voltage waveform of the AC power into a digital waveform, wherein
the phase detection circuit compares the edges of two digital waveforms to detect the phase difference.
17 . A wireless power feeder for feeding power by wireless from a feeding coil to a receiving coil at the resonance frequency of the feeding coil and receiving coil, comprising:
a power circuit;
the feeding coil;
an exciting coil that is magnetically coupled to the feeding coil and feeds AC power fed from the power circuit to the feeding coil;
a detection coil that generates inductive current using a magnetic field generated by the AC power; and
a phase detection circuit that detects the phase difference between the voltage phase and current phase of the AC power, wherein
the power circuit includes first and second current paths and makes first and second switches connected in series respectively to the first and second current paths alternately conductive to feed the AC power to the exciting coil, and
the phase detection circuit measures the phase of the inductive current flowing in the detection coil to achieve measurement of the current phase of the AC power.
18 . A wireless power feeder for feeding power by wireless from a feeding coil to a receiving coil at the resonance frequency of the feeding coil and receiving coil, comprising:
a power circuit that feeds AC power to the feeding coil at the drive frequency;
a feeding coil circuit that includes the feeding coil and a capacitor, and resonate at the resonance frequency;
a detection coil that generates inductive current using a magnetic field generated by the AC power of the feeding coil circuit; and
a phase detection circuit that detects the phase difference between the voltage phase and current phase of the AC power, wherein
the power circuit includes first and second current paths and makes first and second switches connected in series respectively to the first and second current paths alternately conductive to feed the AC power to the feeding coil circuit, and
the phase detection circuit measures the phase of inductive current passing through the detection coil to achieve measurement of the current phase of the AC power.
19 . The wireless power feeder as claimed in claim 17 , wherein
the detection coil is a coil that generates the inductive current using a magnetic field generated by the AC power flowing through the feeding coil.
20 . The wireless power feeder as claimed in claim 17 , wherein
the detection coil is a coil that generates the inductive current using a magnetic field generated by the AC power flowing through the exciting coil.
21 . The wireless power feeder as claimed in claims 17 , further comprising a drive frequency tracking circuit that adjusts the drive frequency of the power transmission control circuit so as to reduce the detected phase difference to allow the drive frequency to track the resonance frequency.
22 . The wireless power feeder as claimed in claim 17 , wherein
the detection coil is wounded around a toroidal core, and
a part of the exciting coil is made to pass through the toroidal core to constitute a coupling transformer by the exciting coil and detection coil.
23 . The wireless power feeder as claimed in claims 17 , wherein
the detection coil is wounded around a toroidal core, and
a part of the feeding coil is made to pass through the toroidal core to constitute a coupling transformer by the feeding coil and detection coil.
24 . The wireless power feeder as claimed in claims 17 , wherein
a resistor is connected in parallel to both ends of the detection coil, and
the phase detection circuit measures the current phase from a change in voltage applied to the resistor.
25 . The wireless power feeder as claimed in claims 17 , further comprising:
a first waveform rectifier that converts an analog waveform having the same phase as that of a current waveform of the AC power into a digital waveform; and
a second waveform rectifier that converts an analog waveform having the same phase as that of a voltage waveform of the AC power into a digital waveform, wherein
the phase detection circuit compares the edges of two digital waveforms to detect the phase difference.
26 . A wireless power transmission system comprising:
a wireless power feeder as claimed in claim 2 ;
the receiving coil; and
a loading coil that is magnetically coupled to the receiving coil and receives power that the receiving coil has received from the feeding coil.
27 . A wireless power transmission system comprising:
a wireless power feeder as claimed in claim 10 ;
the receiving coil; and
a loading coil that is magnetically coupled to the receiving coil and receives power that the receiving coil has received from the feeding coil.
28 . A wireless power transmission system comprising:
a wireless power feeder as claimed in claim 18 ;
the receiving coil; and
a loading coil that is magnetically coupled to the receiving coil and receives power that the receiving coil has received from the feeding coil.