Patent ID: 8884469

Claim:
Circuitry for use in a primary unit of an inductive power transfer system to generate an electromagnetic field so as to transfer power wirelessly by electromagnetic induction to one or more secondary units of the system, the or each secondary unit having a load and being separable from the primary unit, the circuitry comprising: a resonance network; a primary circuit; a driving circuit operable to supply said resonance network and said primary circuit with a drive signal so as to cause said primary circuit to generate said electromagnetic field, said resonance network and said primary circuit collectively having a frequency response, said frequency response having a first resonant peak at a first frequency defined primarily by said resonance network and a second resonant peak at a second frequency defined primarily by said primary circuit, wherein said drive signal is supplied at a frequency between said first frequency and said second frequency; wherein said first frequency, said second frequency, and said drive signal frequency are different frequencies.