Transmitter for an Inductive Power Transfer System
An inductive power transfer transmitter that includes an enclosure for accommodating devices to be energised. The enclosure has one or more side walls and one or more coils for generating an alternating magnetic field within the enclosure. The density of the one or more coils varies with distance from an end of the one or more sidewalls. There is also disclosed an inductive power transmitter that includes one or more magnetically permeable layers wherein the combined thickness or the permeability of the one or more magnetically permeable layers varies.
1 . An inductive power transfer transmitter comprising:
an enclosure for accommodating devices to receive wireless power, the enclosure having a base portion and one or more sidewalls extending from the base portion; and
a drive circuit configured to drive a coil disposed within the one or more sidewalls so as to generate an alternating magnetic field within the enclosure;
wherein the coil is arranged so that a number of loops of the coil per unit height varies in a manner selected to improve uniformity of the magnetic field within the enclosure.
2 . The inductive power transmitter of claim 1 wherein the varying number of loops of the coil per unit height causes a corresponding variation in lateral coil thickness with height.
3 . The inductive power transmitter of claim 1 wherein the varying number of loops per unit height is achieved by winding the coils outwardly from a center of the enclosure.
4 . The inductive power transmitter of claim 1 wherein the number of loops of the coil per unit height is higher near a top of the enclosure.
5 . The inductive power transfer transmitter of claim 1 , wherein the base portion includes a magnetically permeable layer.
6 . The inductive power transfer transmitter of claim 5 , wherein the coil is made of wire that decreases in gauge.
7 . The inductive power transfer transmitter of claim 6 , wherein the coil is made of Litz wire.
8 . An inductive power transmitter comprising:
an enclosure configured to receive a device to receive wireless power, the enclosure having a base portion and one or more sidewalls extending from the base portion; and
a drive circuit configured to drive a coil disposed within the one or more sidewalls so as to generate an alternating magnetic field within the enclosure;
wherein the base portion includes one or more magnetically permeable layers having a varying thickness, the varying thickness being selected to improve uniformity of the magnetic field within the enclosure.
9 . The inductive power transmitter of claim 8 , wherein the one or more magnetically permeable layers includes at least two magnetically permeable layers having different dimensions, such that a combined thickness of the at least two magnetically permeable layers is not uniform.
10 . The inductive power transmitter of claim 9 , wherein a first magnetically permeable layer has a first dimension, and a second magnetically permeable layer has smaller dimensions than the first magnetically permeable layer, and the second magnetically permeable layer is placed in the center of the first magnetically permeable layer.
11 . The inductive power transmitter of claim 8 , wherein the combined thickness of the one or more magnetically permeable layers increases towards a center of the base portion.
12 . The inductive power transmitter of claim 8 , wherein the one or more magnetically permeable layers are made of a ferrite material.
13 . The inductive power transmitter of claim 8 wherein the coil is arranged so that a number of loops of the coil per unit height varies in a manner selected to improve uniformity of the magnetic field within the enclosure.
14 . The inductive power transmitter of claim 13 wherein the number of loops of the coil per unit height is higher near a top of the enclosure.
15 . An inductive power transmitter comprising:
an enclosure configured to receive a device to receive wireless power, the enclosure having a base portion and one or more sidewalls extending from the base portion; and
a drive circuit configured to drive one or more coils located in or on the one or more sidewalls to generate an alternating magnetic field within the enclosure; and
wherein the base portion includes one or more magnetically permeable layers having a variable magnetic permeability selected to improve uniformity of the magnetic field within the enclosure.
16 . The inductive power transmitter of claim 15 , wherein the one or more magnetically permeable layers includes at least two magnetically permeable layers having different magnetic permeability.
17 . The inductive power transmitter of claim 15 , wherein the one or more magnetically permeable layers includes a magnetically permeable layer having non-uniform magnetic permeability.
18 . The inductive power transmitter of claim 15 , wherein the one or more magnetically permeable layers are made of a ferrite material.
19 . The inductive power transmitter of claim 15 wherein the coil is arranged so that a number of loops of the coil per unit height varies in a manner selected to improve uniformity of the magnetic field within the enclosure.
20 . The inductive power transmitter of claim 17 wherein the number of loops of the coil per unit height is higher near a top of the enclosure.