This invention relates generally to transformers, and more particularly to transformers having a high quality factor and used for transferring power across an isolated barrier while using a small form factor and achieving a high isolation rating.
Galvanic isolation is the principle of isolating sections of circuits to prevent current flow between the sections. This can be achieved by capacitive or inductive methods. However, the isolation is frequently a limiting factor in circuit design. High quality isolation transformers typically are wire wound transformers, which are large and expensive. The size of such transformers makes them impractical for smaller footprint circuit designs. Small isolation transformers typically have poor isolation rating. There is a need for a small, affordable isolation transformer with a high isolation rating which would be better suited for module integration.
Generally speaking, pursuant to these various embodiments, an isolation transformer includes a particular topology including a first and second inductive element each at least partially embedded in a layer of magnetic material. The magnetic material reduces flux leakage, which both increases the inductance of the transformer and shields against interference between the transformer and the outside circuit. The inductive elements are separated by an isolation layer that limits current leakage between the inductive elements. Such a design allows for a smaller form factor isolation transformer that is readily suitable for modular integration. In particular, transformers with such a topology can have a much smaller profile over other transformers with similar performance characteristics. Use of the magnetic materials also provides for a higher breakdown voltage, which allows for a thinner overall design for the transformer.
These and other benefits may become clearer upon making a thorough review and study of the following detailed description.
The above needs are at least partially met through provision of the isolation transformer topology for module integration described in the following detailed description, particularly when studied in conjunction with the drawings, wherein:
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.
Referring now to the drawings, and in particular to
The first and second layers of magnetic material 110, 120 can be made of any magnetic material. Possible examples include iron, hematite, steel, nickel, cobalt, and ferrite based materials such a nickel-zinc ferrite, ferrite powder disposed in a binder material, a metal powder material, or other types of magnetic ferrite materials. The isolation layer 130 is composed of an electrical insulator. In some embodiments, the isolation layer 130 is comprised of two or more dielectric laminate layers, such as layers of bismaleimide triazine, FR4, ABF, or any other dielectric material used for substrate or printed circuit board manufacturing.
The first layer of magnetic material 110 has an outer edge 111 facing away from the isolation layer 130. The second layer of magnetic material 120 also has an outer edge 121 facing away from the isolation layer 130. The isolation layer has a center plane 135 that is substantially normal to the primary axis 105.
The transformer 100 also includes two inductive elements 140, 150. The first inductive element 140 is positioned between the outer layer 111 of the first magnetic layer 110 and the center plane 135 of the isolation layer 130. The second inductive element 150 is positioned between the outer layer 121 of the second magnetic layer 120 and the center plane 135 of the isolation layer 130. The two inductive elements 140, 150 are arranged such that when a time-varying electrical current is run through the first inductive element 140 it produces a magnetic field that induces a current in the second inductive element 150. In some embodiments, the so constructed transformer is implemented on a silicon substrate.
The two inductive elements 140, 150 are made of conductive material. Example materials include silver, copper, gold, and aluminum. The inductive elements 140, 150 are wound about a center axis or primary magnetic field producing axis extending in an axial direction. The primary magnetic field producing axes of the two inductive elements 140, 150 are substantially parallel to each other. The shape of the inductive elements 140, 150 can vary. Examples include coils, circles, ellipses, racetrack shapes, squares, rectangles, truncated cones, polygons, or others. In the embodiment shown in
The first inductive element 140 is positioned between the center plane 135 of the isolation layer 130 and the outer edge 111 of the first layer of magnetic material 110. The second inductive element 150 is positioned between the center plane 135 of the isolation layer 130 and the outer edge 121 of the second layer of magnetic material 120. Both inductive elements 140, 150 are surrounded on each side by one of the magnetic material or the isolation layer material. In
In typical operation, the isolation layer 130 prevents the direct flow of electrical current between the two inductive elements 140, 150. The magnetic layers 110, 120 prevent substantial flux leakage outside of the transformer. This reduced flux leakage results in a high quality factor. The magnetic layers 110, 120 have the added effect of shielding the transformer 100 from electrical interference form the surrounding circuit. The reduced flux leakage also protects the surrounding circuit from interference caused by the transformer 100. The magnetic material of the magnetic layers 110, 120 in the illustrated example of
In the embodiment shown in
In the embodiment shown in
As shown in the example of
The indentation 122 in the isolation layer 130 at least partially filled with magnetic material can extend all the way through the isolation layer 130 as shown in the example of
In an alternative embodiment, as shown in
In an alternative embodiment, the first and second inductive elements 140, 150 are disposed on the surface of the isolation layer 130. The magnetic material extends to cover the inductive elements in the radial directions 106, 107 as well in the axial direction 105 on the faces of the inductive elements 140, 150 facing away from the isolation layer 130. The inductive elements 140, 150 are surrounded by the isolation layer 130 or the layers of magnetic material 110, 120 on every side.
Those skilled in the art will recognize that a wide variety of modifications, alterations, and combinations can be made with respect to the above described embodiments without departing from the scope of the invention, and that such modifications, alterations, and combinations are to be viewed as being within the ambit of the inventive concept.