Transmission-guard system and method for an inductive power supply

1. A wireless power transmitter operable to transfer power wirelessly to a wireless power receiver, said wireless power transmitter comprising:

a primary coil operable to form an inductive couple with a secondary coil associated with said wireless power receiver and to transfer power wirelessly thereto;

a detector operable to activate said wireless power transmitter when a wireless power receiver is brought into proximity therewith;

a driver operable to be triggered by said detector and to provide a driving voltage across said primary coil; and

a peak detector for monitoring transmission voltage of said wireless power transmitter,

wherein said detector is operable to detect resonance of said inductive couple, said driver is operable to select a transmission frequency significantly different from a resonant frequency of said inductive couple, and said peak detector is configured to detect large increases in the transmission voltage indicating an increase in resonant frequency.

2. The wireless power transmitter of claim 1 wherein said detector comprises an array of magnetic switches.

3. The wireless power transmitter of claim 2 , wherein said array of magnetic switches is configured to be activated by a corresponding configuration of magnetic elements in the wireless power receiver.

4. The wireless power transmitter of claim 1 wherein said detector comprises a Hall effect sensor configured to detect a magnetic field.

5. The wireless power transmitter of claim 1 wherein said detector comprises a magnetic switch.

6. The wireless power transmitter of claim 1 wherein said detector comprises said primary coil.

7. The wireless power transmitter of claim 1 wherein said detector is operable to detect resonance of said wireless power receiver.

8. The wireless power transmitter of claim 1 wherein said detector is operable to detect a frequency identifying the wireless power receiver.

9. The wireless power transmitter of claim 1 wherein said detector is operable to detect a frequency authenticating the wireless power receiver.

10. The wireless power transmitter of claim 1 wherein said primary coil is operable to apply a power pulse to energize said secondary coil to transmit a response signal and said detector is operable to detect said response signal.

11. A method for establishing wireless power transfer from a wireless power transmitter to a wireless power receiver, which method comprises:

detecting, by a detector of said wireless power transmitter, a magnetic field when said wireless power receiver is in proximity therewith;

activating said wireless power transmitter upon detection of the magnetic field;

detecting resonance of an inductive couple formed between a primary coil of said wireless power transmitter and a secondary coil of said wireless power receiver;

selecting a transmission frequency significantly different from a resonant frequency of said inductive couple; and

monitoring transmission voltage of said wireless power transmitter to detect large increases in the transmission voltage.

12. The method of claim 11 wherein said detecting comprises a Hall effect sensor detecting a magnetic field from said wireless power receiver.

13. The method of claim 11 wherein said detecting comprises said primary coil detecting a response from a secondary coil of said wireless power receiver.

14. The method of claim 11 wherein said detecting comprises said primary coil detecting a frequency authenticating the wireless power receiver.

15. The method of claim 11 wherein said detecting comprises said primary coil applying a power pulse to energize a secondary coil of said wireless power receiver to transmit a response signal and said detecting said response signal.