Multi-Coil Wireless Power Transmitter

A wireless power transmitter, comprising:

• a plurality of coils, the plurality of coils configured such that nearest-neighbor coils produce magnetic fields of opposite directions;
• a switching network coupled to the plurality of coils, the switching network receiving one or more power signals and applying the one or more power signals to one or more of the plurality of coils according to switching signals;
• a power source configured to provide the one or more power signals to the switching network according to power control signals;
• a signal sensor configured to receive signals from each of the plurality of coils and provide sense signals;
• and
• a controller configured to provide switching signals to the switching network, power control signals to the power source, and to receive sense signals from the signal sensors, the controller configured to execute instructions to
• determine a position of a receiver relative to the plurality of coils based on the sense signals;
• select one or more of the plurality of coils as active coils based on the position;
• provide power control signals to the power source;
• provide switching signals to the switching network to provide power from the one or more power signals to the active coils;
• monitor the sense signals to determine whether the receiver has moved to a new position;
• and
• if the receiver has moved to a new position,
• reassign active coils according to the new position, and
• transition power in the switching network to provide power from the reassigned active coils.