Abstract: An inductive power transfer device including: a resonant circuit, having a power transfer coil and a power transfer capacitor; a coupling coil, magnetically-coupled to the power transfer coil; a variable impedance; and a controller configured to determine the impedance value of the variable impedance based on predetermined criteria including: substantially regulating power provided to a load; tuning the resonant circuit resonant frequency substantially to a predetermined frequency; adjusting a frequency of a magnetic field associated with the power transfer coil; and/or adjusting an impedance reflected by the power transfer coil to a corresponding coupled power transfer coil.

Abstract: An inductive power transfer device including: a resonant circuit, having a power transfer coil and a power transfer capacitor; a coupling coil, magnetically-coupled to the power transfer coil; a variable impedance; and a controller configured to determine the impedance value of the variable impedance based on predetermined criteria including: substantially regulating power provided to a load; tuning the resonant circuit resonant frequency substantially to a predetermined frequency; adjusting a frequency of a magnetic field associated with the power transfer coil; and/or adjusting an impedance reflected by the power transfer coil to a corresponding coupled power transfer coil.

Abstract: A contactless power system comprising a power transmitter having a transmitting coil and a power receiver having a receiving coil, the power receiver being configured to receive power transmitted by the power transmitter via contactless electromagnetic coupling of the respective coils and deliver the received power to a load, wherein the receiving coil of the power receiver is part of a resonant circuit having a resonant frequency, the resonant circuit comprising a detuning element to detune the frequency of the resonant circuit from the resonant frequency in accordance with power requirements of the load.