Inductive element for intravascular implantable devices
An inductive element adapted for use in implantable intravascular devices (IIDs) having an elongate form factor with a cross-section. The inductive element includes a core that has an outer surface contour that corresponds to the form factor. A set of elongate, or oblong, windings are situated lengthwise along the major length dimension of the inductive element. The windings are also situated to direct a magnetic field along a radial direction in relation to the elongate form factor. In one embodiment the form factor is generally cylindrical and the cross-section is generally round.
1. An implantable intravascular medical device comprising:
a structure that defines a form factor having an elongate geometry including a form factor length and a cross-section defined perpendicularly to the form factor length; and
a circuit situated within the form factor and including an inductive element;
wherein the inductive element includes:
a core of magnetic material having a core length and a core cross-section defined perpendicularly to the length; and
a coil having a plurality of windings that define a loop area;
wherein a portion of the core is situated in the loop area such that the coil, when energized, produces a magnetic flux in the core along a forward path and a return path; and
wherein a sum of a total cross-sectional area of the magnetic flux in the forward path and a total cross-sectional area of the magnetic flux in the return path is greater than an area of the core cross-section.
2. The implantable intravascular medical device of claim 1 , wherein the sum of a total cross-sectional area of the magnetic flux in the forward path and the total cross-sectional area of the magnetic flux in the return path is greater than an area of the cross-section of the form factor.
3. The implantable intravascular medical device of claim 1 , wherein the loop area is greater than at least one area selected from the group consisting of: an area of the core cross-section, and an area of the cross-section of the form factor.
4. The implantable intravascular medical device of claim 1 , wherein:
the implantable intravascular device includes a defibrillator and the circuit is a power converter circuit;
the form factor is generally cylindrical and has a generally circular cross-section, and the structure that defines the form factor includes a housing having a generally cylindrical outer surface and an inner surface that defines at least a portion of the form factor, wherein the housing includes a generally hermetic barrier;
the inductive element is a transformer having a plurality of mutually-coupled coils that are entirely arranged within a boundary defined by the outer surface of the inductive element;
the core has a generally cylindrical outer boundary and a post having an oblong cross-sectional boundary with a major oblong dimension situated lengthwise along the generally cylindrical outer boundary, the post having a post height situated radially in relation to the generally cylindrical outer boundary, and the coils being situated around the post; and
the core comprises a pair of core halves, wherein when the core is assembled from the pair of core halves, the core halves interface at respective mating surfaces, and the post comprises a pair of post portions, each post portion corresponding to one of the core halves and arranged such that the post includes an air gap.
5. An inductive element, comprising:
a core of magnetic material having a core length and a generally cylindrical outer boundary; and
at least one coil having a plurality of windings that define a loop area;
wherein a portion of the core is situated in the loop area such that the at least one coil, when energized, produces a closed magnetic flux along a flux path through the core, wherein a length of the flux path is less than the core length.
6. The inductive element of claim 5 , wherein:
the inductive element is a transformer having a plurality of mutually-coupled coils that are entirely arranged within the outer boundary;
the core includes a post having an oblong cross-sectional boundary with a major oblong dimension situated lengthwise along the generally cylindrical outer boundary, the post having a post height situated radially in relation to the generally cylindrical outer boundary, and the coils being situated around the post; and
the core comprises a pair of core halves, wherein when the core is assembled from the pair of core halves, the core halves interface at respective mating surfaces, and the post comprises a pair of post portions, each post portion corresponding to one of the core halves and arranged such that the post includes an air gap.