WIRELESS POWER RECEIVER AND WIRELESS POWER TRANSMISSION SYSTEM
Power is fed from a feeding coil L 2 to a receiving coil L 3. In a wireless power receiver 118, capacitors CA and CB are each charged by received power and function as a DC power source. Meanwhile, a reference signal and an input signal are supplied to a control signal generation circuit 108. Based on the reference signal and input signal, the control signal generation circuit 108 generates a control signal representing the signal level of the input signal by a duty ratio. A voltage waveform of an output voltage V 5 at a load LD is controlled by the control signal.
1 . A wireless power receiver that receives, at a receiving coil, AC power fed from a feeding coil by wireless using a magnetic field resonance phenomenon between the feeding coil and the receiving coil, the receiver comprising:
a receiving coil circuit that includes the receiving coil and a capacitor; and
a loading circuit that includes a loading coil that is magnetically coupled to the receiving coil to receive the AC power from the receiving coil and an adjustment circuit that adjusts an output voltage,
the adjustment circuit including:
a reference signal generation circuit that generates a reference signal at a predetermined reference frequency; and
a control signal generation circuit that receives an input signal including a frequency component lower than the reference frequency and generates a control signal representing a magnitude relation between the signal level of the reference signal and that of the input signal, and
adjusting the output voltage based on the control signal.
2 . The wireless power receiver according to claim 1 , wherein
the control signal generation circuit changes the duty ratio of the control signal based on a magnitude relation between the signal level of the reference signal and that of the input signal.
3 . The wireless power receiver according to claim 1 , wherein
the adjustment circuit includes a DC circuit that generates DC voltage from the AC power and changes the DC voltage based on the control signal to generate the output voltage.
4 . The wireless power receiver according to claim 3 , wherein
the adjustment 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 turn conductive depending on the state of the control signal to generate the output voltage from the DC voltage.
5 . The wireless power receiver according to claim 4 , wherein
the adjustment circuit makes the first and second switches turn conductive/non-conductive in a complementary manner based on the control signal.
6 . The wireless power receiver according to claim 1 , wherein
the input signal is a sine-wave signal at a commercial frequency band.
7 . A wireless power transmission system comprising:
the wireless power receiver as claimed in claim 1 ;
the feeding coil; and
a power supply circuit that supplies the AC power to the feeding coil.
8 . The wireless power transmission system according to claim 7 , wherein
the power supply circuit feeds the AC power from the feeding coil that does not substantially resonate with a circuit element at the power feeding side to the receiving coil.
9 . The wireless power transmission system according to claim 7 , wherein
the feeding coil does not constitute a resonance circuit that resonates with a power feeding side circuit element at a resonance point corresponding to the resonance frequency of the receiving coil.
10 . The wireless power transmission system according to claim 7 , wherein
a capacitor is not inserted in series or in parallel to the feeding coil.