Electronic device having an inductive receiver coil with ultra-thin shielding layer and method

摘要

An electronic device (10,40) which is inductively powered or charged has a receiver coil (12) on which a metal object (24,42) can be placed without causing deterioration of the coil's magnetic field and without generating heat in the metal object. An ultra-thin, flexible, high magnetic permeability metal foil (14) having a thickness of 50 μm or less is provided as a shielding layer between the coil and the object. Radial slits (22) are provided in the shielding layer, which suppress unwanted eddy currents in the layer to reduce power transfer losses and heat generation.

主权项

1. An electronic device configured for being inductively powered or charged comprising:
an inductive receiver coil configured for generating current in response to being exposed to an alternating magnetic field generated substantially on a first side of the receiver coil, and a soft magnetic shielding layer disposed on a second side of the receiver coil, opposite to the first side where the magnetic field is generated, configured to shield the magnetic field from an overlying object and mitigate formation of eddy currents within the soft magnetic shielding layer and the overlying object, the overlying object being subject to an undesirable influence by the magnetic field or causing an undesirable influence on the magnetic field; wherein said soft magnetic shielding layer includes an ultra-thin layer having a thickness less than or equal to one hundred micrometers (100 μm) and at least one eddy current mitigation feature that comprises a number of slits formed within the soft magnetic shielding layer, the slits being substantially parallel to magnetic flux lines and orthogonal to eddy current flow for imposing a large impedance to eddy current formation, the slits extending from an outer perimeter of the soft magnetic shielding layer toward but not ultimately reaching a solid center of the soft magnetic shielding layer, the slits including a number of short slits and a number of long slits, the short slits having a length that is shorter than a length of the long slits, and wherein the soft magnetic shielding layer comprises a material selected from the group consisting of Mumetal, nanocristaline metal and amorphous metals.