US Patent 9672976 Multi-mode wireless charging

A device may include a multiple inductive coils arranged concentrically for operating according multiple modes of wireless power transfer. The device may include multiple layers of magnetic shields to protect device components from the effects of the magnetic field used for power transfer. Construction and material of multiple layers of shields may be based on addressing individually the different parameters of the multiple modes of operation and based on the combined effect of the layers in each mode of operation. In some examples, the device may include first and second ferrite shields each having different magnetic properties.