System for inductive wireless power transfer for portable devices

A wireless power transfer system comprising:

• a wireless power receiver comprising
• a rechargeable battery,
• a ferrite core, wherein a cross section of the ferrite core is solid,
• a receiver coil having a length wrapped around the ferrite core such that the ferrite core and the receiver coil share a longitudinal axis, wherein the receiver coil is disposed at a substantially same angle to the longitudinal axis along the length of the receiver coil, and
• a receive circuit coupled to the receiver coil configured to convert a time varying current induced in the receiver coil into a voltage to charge the rechargeable battery,
• wherein the wireless power receiver includes an externally visible marking that indicates the longitudinal axis of the ferrite core and the receiver coil;
• and
• a housing in which the wireless power receiver is disposed, an external portion of the housing configured for a predetermined alignment between the receiver coil and the housing.

An electronic device comprising:

• a wireless power receiver structure comprising
• a ferrite core, wherein a cross section of the ferrite core is solid,
• a receiver coil having a length wrapped around the ferrite core such that the ferrite core and the receiver coil share a longitudinal axis, wherein the receiver coil is disposed at a same angle to the longitudinal axis along the length of the receiver coil, and
• a receive circuit coupled to the receiver coil configured to convert a time varying current induced in the receiver coil into a voltage;
• and
• a visible marking disposed on an external portion of a housing of the wireless power receiver structure, the visible marking representative of a direction of the longitudinal axis with respect to the housing.