Patent attributes
Systems and methods for ensuring that resonant inductive power transfer goes only to authorized users using encryption. Resonant inductive power transfer requires near-identical resonant frequencies in the transmitter and the receiver. The frequency of the power transfer signal changes on a schedule known only to the transmitter and receiver so a “power eavesdropper” cannot track the frequency well enough to efficiently receive power. To make the frequency transitions energetically efficient, a capacitive or inductive element is switched in or out of each circuit at moments of zero-crossing: zero charge on a capacitor or zero current in an inductor. To maintain phase alignment, either switching an inductor on the transmit side is nearly simultaneous with switching a capacitor on the receive side, or switching a capacitor on the transmit side is nearly simultaneous with switching an inductor on the receive side.
