EP0435160A1

EP0435160A1 - Inductor

Info

Publication number: EP0435160A1
Application number: EP90124835A
Authority: EP
Inventors: Tetsuya Yokokawa
Original assignee: Toshiba Lighting and Technology Corp
Current assignee: Toshiba Lighting and Technology Corp
Priority date: 1989-12-28
Filing date: 1990-12-19
Publication date: 1991-07-03
Also published as: KR910013322A; JPH03201511A

Abstract

An inductor for use in a circuit. The inductor includes a spiral coil (16) consisting of a conductor material (26) and an insulating material (28) formed into a spiral together, wherein the conductor material (26) in the spiral is selectively connected through the insulating material (28).

Description

The present invention relates generally to an inductor, and more particularly, to an inductor which has an improved induction characteristics.
A planar inductor 10, as shown in FIGURES 1 and 2, is well known in an prior art. FIGURES 1 and 2 show a side section and a plan section of the planar inductor 10, respectively. Such a planar inductor 10 comprises a planar inductor element 12 and a base 14 for mounting the element 12 thereon (see FIGURE 1). The planar inductor element 12 comprises a spiral coil 16 and a pair of magnetic layers 18, 20. The spiral coil 16 is laid between the magnetic layers 18, 20 via insulating layers 22, 24. The spiral coil 16 includes a conductor layer 26 and an insulator layer 28 which are coiled together (see FIGURE 2).
In many fields, such a planar inductor 10 is adapted in a power supply circuit. There is a field in which a specific characteristic of inductance to current, e.g., a non-linear characteristics as shown in FIGURE 3, is necessary. To satisfy such a demand, two planar inductors with different inductances have been used in series connection, as shown in FIGURE 4.
In FIGURE 4, a first planar inductor 10a with a small inductance L1 and a second planar inductor 10b with a large inductance L2 are coupled in series within a power supply circuit 30. According to the power supply circuit 30, a large inductance La (La = L1 + L2) can be established at a low load (see FIGURE 3). While, a relatively small inductance Lb (Lb = L1) can be established without saturation at a high load.
However, such a power supply circuit using inductors has a problem in that cost will increase because a plurality of inductance elements having different inductances become necessary. Therefore, it has been desired to improve the inductance elements for simplifying such a power supply circuit.
The present invention therefore seeks to provide an improved inductor.
The present invention also seeks to provide an inductor having an inductance characteristic which is equivalent to that obtained by using a plurality of inductance elements.
An inductor according to one aspect of the present invention includes a spiral coil consisting of a conductor material and an insulating material formed into a spiral together, wherein the conductor material in the spiral is selectively connected through the insulating material.
For a better understanding of the present invention and many of the attendant advantages thereof reference will now be made by way of example to the accompanying drawings, wherein:

FIGURE 1 is a side section of a conventional planar inductor;
FIGURE 2 is a plan section of the conventional planar inductor of FIGURE 1;
FIGURE 3 is a graph for showing a D.c. biased current dependence of inductance of inductors required in a power supply circuit;
FIGURE 4 is a diagram showing a power supply circuit using two conventional inductors;
FIGURE 5 is a cross section showing an embodiment of the inductor according to the present invention;
FIGURE 6 is a plan section showing a modification of the inductor according to the present invention;
FIGURE 7 is a plan view showing a modification of the inductor according to the present invention; and
FIGURE 8 is a plan view showing another modification of the inductor according to the present invention.

The present invention will be described in detail with reference to the FIGURES 5 through 8. Throughout the drawings, reference numerals or letters used in FIGURES 1 through 4 will be used to designate like or equivalent elements for simplicity of explanation.
Referring now to FIGURES 5 and 6, an embodiment of the inductor according to the present invention will be described in detail. In this embodiment, the inductor is implemented as a planar inductor 10. FIGURES 5 and 6 show a cross section and a plan section of the planar inductor 10, respectively.
The planar inductor 10 comprises a planar inductor element 12 and a base 14 for mounting the inductor element 12 thereon (see FIGURE 5). The base 14 is, for instance, made of alumina.
The planar inductor element 12 comprises a spiral coil 16 and a pair of magnetic layers 18, 20. The spiral coil 16 is laid between magnetic layers 18, 20 via insulating layers 22, 24, respectively.
The spiral coil 16 includes a conductor layer 26 and an insulator layer 28 which are coiled together (see FIGURE 6).
At a bridging section A, as shown in FIGURE 6, two adjacent turns 26a and 26b of the conductor layer 26 are electrically bridged with each other by a bridge connection 32 through the insulator layer 28.
According to the planar inductor 10 with the structure as described above, the spiral coil 16 is separated into the inner and outer coil parts at the bridging section A. As a result, the planar inductor 10 exhibits a non-linear inductance characteristics which is equivalent to that of FIGURE 3.
Therefore, if the bridging section A is defined in a proper position so that either the inner or outer coil part is not saturated for load current, the non-linear D.C. biased current dependence of induction, as shown in FIGURE 3, can be realized by a single element.
Further, because the same characteristic as that obtainable from two inductance elements can be obtained from a single inductance element, cost can be reduced below that of a conventional inductor, and also, the mounting density can be increased.
Referring now to FIGURE 7, a modification of the planar inductor 10 will be described in brief. In FIGURE 7, a spiral coil 16 is formed by using a conventional print circuit technique.
For instance, the spiral coil 16 may be formed by a conductive coil pattern 26 printed on an insulative substrate 34. The coil pattern 26 is separated into the inner and outer coil parts at a bridging section A. In the bridging section A, two adjascent turns 26a and 26b of the coil pattern 26 are electrically bridged with each other by a bridge pattern 32. Further, the inner end of the coil pattern 26 is connected to a lead terminal 36 on the opposite surface of the substrate 34 via a through-hole 38.
In the above embodiments, the conductor coil or the coil pattern 26 of the spiral coil 16 is bridged at one portion, but it may be bridged at plural portions more than one.
FIGURE 8 shows such a modification of the inductor which is also implemented by using a print circuit technique. In FIGURE 8, the spiral coil 16 has two bridge portions A1 and A2. However, it will be understood that the spiral coil can have any number of bridge portions more than two. Here, it will be also understood that the inductor with the plural bridge portions becomes equivalent to those with a series circuit including a corresponding number of conventional inductor devices.
It is also understood that the inductor can be implemented for many types of inductors, without being limited to the planar inductor.
As described above, according to the present invention, a desired non-linear inductor characteristic can be obtained by an inductor with a very simple construction. Further, such an inductor can be accomplished at a low cost.
As described above, the present invention can provide an extremely preferable inductor.
While there have been illustrated and described what are at present considered to be preferred embodiments of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made, and equivalents may be substituted for elements thereof without departing from the true scope of the present invention. In addition, many modifications may be made to adapt a particular situation or material to the teaching of the present invention without departing from the central scope thereof. Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out the present invention, but that the present invention include all embodiments falling within the scope of the appended claims.
The foregoing description and the drawings are regarded by the applicant as including a variety of individually inventive concepts, some of which may lie partially or wholly outside the scope of some or all of the following claims. The fact that the applicant has chosen at the time of filing of the present application to restrict the claimed scope of protection in accordance with the following claims is not to be taken as a disclaimer or alternative inventive concepts that are included in the contents of the application and could be defined by claims differing in scope from the following claims, which different claims may be adopted subsequently during prosecution, for example for the purposes of a divisional application.

Claims

An inductor for use in a circuit comprising a spiral coil (16) consisting of a conductor material (26) and an insulating material (28) formed into a spiral together, CHARACTERIZED IN THAT the conductor material (26) in the spiral is selectively connected through the insulating material (28).
An inductor of claim 1, wherein the spiral coil (16) has a bridge section (32) for electrically bridging two adjacent turns (26a, 26b) of the conductor material (26).
An inductor of claim 2, wherein the two adjacent turns (26a, 26b) of the conductor material (26) are connected together via the insulating material (28).
An inductor of claim 1, wherein the insulating material includes an insulative substrate (34) and the conductor material includes a conductive coil pattern (26) printed on the insulative substrate (34).
An inductor of any of claims 1 to 4, wherein the spiral coil (16) has a plurality of bridge sections (A1, A2) each for electrically bridging two adjascent turns of the conductor material (26).