Wireless power feeder, wireless power transmission system, and table and table lamp using the same
Power is fed from a feeding coil to a receiving coil by magnetic resonance. A drive circuit outputs an IN signal generated by an oscillator as a DR signal to alternately turn ON/OFF switching transistors at a resonance frequency, whereby AC current is fed to the feeding coil, and then the AC current is fed from the feeding coil to the receiving coil. An enable signal generation circuit generates an EN signal at a frequency lower than the resonance frequency. The drive circuit outputs the DR signal only while the EN signal assumes a high level. Transmission power from a wireless feeder to a wireless receiver is controlled by adjusting the duty ratio of the EN signal.
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 transmission control circuit that feeds AC power to the feeding coil at the resonance frequency;
a feeding coil circuit that includes the feeding coil and a capacitor and resonates at the resonance frequency;
a control signal generation circuit that generates a control signal having a control frequency lower than the resonance frequency; and
a comparison circuit that generates an enable signal when a predetermined magnitude relationship is established between the level of the control signal and that of a reference signal, wherein
the power transmission control circuit feeds the AC power to the feeding coil under only while the enable signal is being generated.
2. The wireless power feeder according to claim 1 , wherein
the control signal generation circuit generates a signal having a saw-tooth waveform as the control signal.
3. The wireless power feeder according to claim 1 , further comprising a reference signal adjustment circuit for adjusting the level of the reference signal.
4. The wireless power feeder according to claim 1 , further comprising an exciting coil that is magnetically coupled to the feeding coil and feeds AC power fed from the power transmission control circuit to the feeding coil, wherein
the power transmission control 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.
5. A wireless power transmission system comprising:
the wireless power feeder as claimed in claim 1 ;
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.
6. A table with wireless power feeding function comprising the wireless power feeder as claimed in claim 1 , wherein
the feeding coil is provided on the rear surface of the table or incorporated inside the table.