Transformer and electrical device using the same

Information

  • Patent Grant
  • 6559750
  • Patent Number
    6,559,750
  • Date Filed
    Wednesday, July 25, 2001
    23 years ago
  • Date Issued
    Tuesday, May 6, 2003
    22 years ago
Abstract
A transformer comprises first and second flat coils stacked with each other. Each of first and second flat coils comprises a conductive wire which is wound in a flat spiral shape having a through hole at a center thereof such that the conductive wire has an inner end and an outer end at an inner periphery and an outer periphery of the spiral shape, respectively. The inner end of the first flat coil passes through the through hole of the second flat coil, thus reducing the overall thickness of the transformer because both inner ends pass over only one flat coil.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to transformers and electrical devices using the same. In particular, the present invention relates to a transformer to be used for a switching power supply device and to an electrical device using the transformer.




2. Description of the Related Art





FIG. 10

is an exploded perspective view of a known thin transformer. In

FIG. 10

, a transformer


1


includes flat coils


2


,


3


, and


4


which are formed by winding wires in spirals and which coaxially overlap each other with doughnut-shaped insulative sheets


5


and


6


therebetween, and core members


7


and


8


sandwiching the flat coils


2


,


3


, and


4


and the insulative sheets


5


and


6


. The flat coils


2


,


3


, and


4


coaxially overlapping each other are individually provided with holes for passing a magnetic core-leg formed in central parts of the flat coils


2


,


3


, and


4


. The core members


7


and


8


are each provided with a magnetic core-leg.





FIG. 11A

is a plan view of the flat coil


3


of the transformer


1


.

FIG. 11B

is a sectional view along line A—A of the flat coil


3


shown in FIG.


11


A. In

FIG. 11A

, the flat coil


3


is formed with a wire


3




a


wound in a spiral. An inner end


3




b


of the wire


3




a


is drawn to the outside over the other part of the wire


3




a


. An outer end


3




c


of the wire


3




c


is drawn to the outside in the same winding direction.




The thickness of the overall flat coil


3


thus formed is substantially the same as the diameter of the wire


3




a


. However, the thickness of the flat coil


3


is at least twice the diameter of the wire


3




a


in a portion of the flat coil


3


over which the inner end


3




b


of the wire


3




a


is drawn to the outside. The flat coils


2


and


4


each have the same configuration as the flat coil


3


shown in

FIGS. 11A and 11B

.




The transformer I shown in

FIG. 10

includes the flat coils


2


,


3


, and


4


overlapping each other, each having the thickness twice the diameter of the wire


3




a


, whereby the thickness of the flat coils


2


,


3


, and


4


becomes six times the diameter of the wire


3




a


. Since the transformer


1


also includes the insulative sheets


5


and


6


each having a given thickness, there is a problem in that the thickness of the transformer


1


is increased.




SUMMARY OF THE INVENTION




Accordingly, it is an object of the present invention to provide a transformer which can be reduced in thickness and an electrical device using the transformer.




To the end, according to an aspect of the present invention, a transformer comprises a plurality of flat coils overlapping each other, each formed by winding a wire in a spiral. Respective inner ends of the wires forming at least two of the plurality of flat coils are drawn out through a hole for passing a magnetic core-leg and over one of the plurality of flat coils. The respective inner ends are disposed on the same surface of the one of the plurality of flat coils.




The inner ends of the other two of the plurality of flat coils may be connected to each other.




In the transformer according to the present invention, respective outer ends of the wires forming two of the plurality of flat coils may be connected to each other.




The wire forming at least one of the plurality of flat coils may be a three-layer insulated wire.




The wire may be a self-welding-type three-layer insulted wire.




An electrical device according to the present invention is provided which comprises the transformer described above.




The transformer according to the present invention can be reduced in thickness by arranging the same as described above.




The electrical device according to the present invention can be reduced in thickness and in size.











BRIEF DESCRIPTION OF THE DRAWING(S)





FIG. 1A

is an exploded perspective view of a transformer according to a first embodiment of the present invention;





FIG. 1B

is an exploded perspective view of a transformer according to a second embodiment of the present invention;





FIG. 2A

is a plan view of the transformer shown in

FIG. 1A

according to the first embodiment of the present invention;





FIG. 2B

is a sectional view along line B—B of the transformer shown in

FIG. 2A

according to the first embodiment of the present invention;





FIG. 3

is a sectional view of a transformer according to a third embodiment of the present invention;





FIG. 4

is an exploded perspective view of a transformer according to a fourth embodiment of the present invention;





FIG. 5

is an exploded perspective view of a transformer according to a fifth embodiment of the present invention;





FIG. 6

is an exploded perspective view of a transformer according to a sixth embodiment of the present invention;





FIG. 7

is an exploded perspective view of a transformer according to a seventh embodiment of the present invention;





FIG. 8

is an exploded perspective view of a transformer according to an eighth embodiment of the present invention;





FIG. 9

is a perspective view of an electrical apparatus according to a ninth embodiment of the present invention;





FIG. 10

is an exploded perspective view of a known transformer;





FIG. 11A

is a plan view of a flat coil used in the known transformer shown in

FIG. 10

; and





FIG. 11B

is a sectional view along line A—A of the flat coil shown in FIG.


11


A.











DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION





FIG. 1A

is an exploded perspective view of a transformer according to a first embodiment of the present invention.

FIG. 1B

is an exploded perspective view of a transformer according to a second embodiment of the present invention.

FIG. 2A

is a plan view of the transformer shown in

FIG. 1A

according to the first embodiment.

FIG. 2B

is a sectional view along line B—B of the transformer shown in

FIG. 2A

according to the first embodiment.

FIGS. 1A

,


1


B,


2


A, and


2


B show major portions of the transformer according to the present invention, in which core members corresponding to the core members


7


and


8


shown in

FIG. 10

are omitted so as to avoid complexity in the drawings, the core members being omitted from the drawings referred to in the following description.




In

FIGS. 1A

,


2


A, and


2


B, a transformer


10




a


includes flat coils


11


,


12


, and


13


coaxially stacked with each other, each formed with a wire wound in a spiral. Doughnut-shaped insulative sheets


14


and


15


are disposed between the flat coils


11


and


12


and between the flat coils


12


and


13


, respectively. In particular, the flat coils


11


,


12


, and


13


are formed with wires


11




a


,


12




a


, and


13




a


, respectively. Each of wires


11




a


,


12




a


, and


13




a


is wound in a spiral shape having a through hole at a center thereof such that the wire has an inner end and an outer end at the inner periphery and the outer periphery of the spiral shape, respectively. The flat coils


11


,


12


, and


13


overlapping each other with the doughnut-shaped insulative sheets


14


and


15


therebetween are provided with holes for passing a magnetic core-leg coaxially formed in a central part of each of the flat coils


11


,


12


, and


13


and the insulative sheets


14


and


15


. The inner end


11




b


of the wire


11




a


forming the flat coil


11


is drawn to the outside of the flat coil


11


, that is, the outside of the transformer


10




a


over a wound portion of the wire


11




a.


The inner end


12




b


of the wire


12




a


forming the flat coil


12


is drawn to the outside of the transformer


10




a


through the respective holes for passing a magnetic core-leg of the insulative sheet


14


and the flat coil


11


and over the wound portion of the wire


11




a


. An inner end


13




b


of the wire


13




a


forming the flat coil


13


is drawn to the outside of the transformer


10




a


through the respective holes for passing a magnetic core-leg of the insulative sheet


15


, the flat coil


12


, the insulative sheet


14


, and the flat coil


11


and over the wound portion of the wire


11




a


forming the flat coil


11


. That is, the inner ends


11




b


,


12




b


, and


13




b


of the flat coils


11


,


12


, and


13


, respectively, are disposed on the same surface of the flat coil


11


. Outer ends


11




c


,


12




c


, and


13




c


of the flat coils


11


,


12


,


13


, respectively, are drawn to the outside of the transformer


10




a


at the same levels as the flat coils


11


,


12


, and


13


, respectively.




In the thus formed transformer


10




a


, the inner ends


11




b


,


12




b


, and


13




b


are drawn to the outside of the transformer


10




a


over the wound portion of the wire


11




a


of the flat coil


11


and are disposed on the same surface of the flat coil


11


. Therefore, the thickness of the overall flat coils, which is the sum of the thickness of the three flat coils


11


,


12


, and


13


and the thickness of a portion of one of the flat coil


11


,


12


, and


13


, of which the inner ends


11




b


,


12




b


, and


13




b


, respectively, are drawn out, is substantially four times the diameter of the wire


11




a


. That is, the transformer


10




a


can be made thinner than the known transformer


1


shown in

FIG. 10

by a thickness corresponding to twice the diameter of a wire, whereby the overall transformer


10




a


can be reduced in thickness.




Although in the transformer


10




a


shown in

FIGS. 1A

,


2


A, and


2


B, the inner ends


11




b


,


12




b


, and


13




b


of the flat coils


11


,


12


, and


13


, respectively, are brought into contact with each other and into the flat coil


11


, it may be necessary to dispose the inner ends


11




b


,


12




b


, and


13




b


separated from each other and to provide an insulative film between the flat coil


11


and the inner ends


11




b


,


12




b


, and


13




b


according to the dielectric strength between the flat coils


11


,


12


, and


13


.




Although in the transformer


10




a


shown in

FIG. 1A

, the inner ends


11




b


,


12




b


, and


13




b


of the flat coils


11


,


12


, and


13


, respectively, are drawn out over the outer surface (upper side) of the outermost flat coil


11


, the inner ends


11




b


,


12




b


, and


13




b


may be drawn out over the outer surface (lower side) of the outermost flat coil


13


. The inner ends


11




b


,


12




b


, and


13




b


may be drawn out between the flat coils


11


and


12


or between the flat coils


12


and


13


. The inner ends


11




b


,


12




b


, and


13




b


may be drawn out in directions differing from each other, as in a transformer


10




b


according to a second embodiment shown in

FIG. 1B

, as long as the inner ends


11




b


,


12




b


, and


13




b


are each disposed on the same surface of one of the flat coils


11


,


12


, and


13


. When the inner ends


11




b


,


12




b


, and


13




b


are drawn out between two of the flat coils


11


,


12


, and


13


, an insulative film may be provided between the corresponding flat coil


11


,


12


, or


13


and the inner ends


11




b


,


12




b


, and


13




b


, as needed.





FIG. 3

is a sectional view of a transformer according to a third embodiment of the present invention. The transformer is shown in section along a line corresponding to the line B—B of the transformer


10




a


shown in FIG.


2


A. Components the same as or corresponding to those which are shown in

FIGS. 2A and 2



b


are referred to with the same reference numerals, for which description is omitted.




In a transformer


18


shown in

FIG. 3

, the inner end


13




b


of the wire


13




a


forming the flat coil


13


is drawn to the outside of the transformer


18


through the respective holes for passing a magnetic core-leg of the insulative sheet


15


, the flat coil


12


, the insulative sheet


14


, and the flat coil


11


and over the inner ends


11




b


and


12




b


of the flat coils


11


and


12


, respectively. That is, the inner ends


11




b


and


12




b


of the flat coils


11


and


12


, respectively, are disposed on the same surface of the flat coil


11


, and the inner end


13




b


of the flat coil


13


is disposed on the inner ends


11




b


and


12




b.






In the thus formed transformer


18


, the two inner ends


11




b


and


12




b


of the two flat coils


11


and


12


, respectively, are drawn to the outside of the transformer


18


over a wound portion of the wire


11




a


of the flat coil


11


on the same surface of the flat coil


11


. Therefore, the thickness of the overall flat coils


11


,


12


, and


13


, which is the sum of the thickness of the three flat coils


11


,


12


, and


13


, the thickness corresponding to the diameter of a portion of one of the wires


11




a


and


12




a


of which the inner ends


11




b


and


12




b


, respectively, are drawn out, and the thickness corresponding to the diameter of the inner end


13




b


of the wire


13




a


which is drawn out is substantially five times the diameter of a wire. Although the thickness of the overall flat coils of the transformer


18


is greater than that of the transformer


10




a


or


10




b


shown in

FIG. 1A

or


1


B, respectively, the transformer


18


can be made thinner than the known transformer


1


shown in

FIG. 10

by a thickness corresponding to the diameter of the wire


11




a


,


12




a


, or


13




a


, whereby the overall transformer


18


can be reduced in thickness.




The thickness of the transformer


18


can be reduced when the inner ends of at least two flat coils are each drawn out over a surface of one of the flat coils


11


,


12


, and


13


.




Although in the transformer


18


shown in

FIG. 3

, the inner ends


11




b


and


12




b


of the two flat coils


11


and


12


, respectively, are each drawn out over the outer side of the outermost flat coil


11


, the two inner ends


11




b


and


12




b


may be drawn out between two flat coils


11


and


12


or


12


and


13


, in the same way as in the transformer


10




a


or


10




b


shown in

FIG. 1A

or


1


B, respectively.





FIG. 4

is an exploded perspective view of a transformer according to a fourth embodiment of the present invention, in which components the same as or corresponding to those of the transformers


10




a


and


10




b


shown in

FIGS. 1A and 1B

, respectively, are referred to with the same reference numerals, for which description is omitted.




In a transformer


20


shown in

FIG. 4

, the inner ends


1


b and


13




b


of the wire


11




a


and


13




a


forming the flat coils


11


and


13


are drawn to the outside of the transformer


20


over a wound portion of the wire


11




a


forming the flat coil


11


, the inner end


13




b


being drawn through the respective holes for passing a magnetic core-leg of the insulative sheet


15


, the flat coil


12


, the insulative sheet


14


, and the flat coil


11


. That is, only the inner ends


11




b


and


13




b


of the flat coils


11


and


13


, respectively, are disposed on the same surface of the flat coil


11


. The inner end


12




b


of the wire


12




a


forming the flat coil


12


is drawn to the outside of the transformer


20


between the flat coils


11


and


12


, more particularly, between the insulative sheet


14


and the flat coil


12


over a wound portion of the wire


12




a.






In the thus formed transformer


20


, the two inner ends


11




b


and


13




b


of the two flat coils


11


and


13


, respectively, are drawn to the outside of the transformer


20


over the wound portion of the wire


11




a


of the flat coil


11


on the same surface of the flat coil


11


. Therefore, the thickness of the overall flat coils, which is the sum of the thickness of the three flat coils


11


,


12


, and


13


, the thickness corresponding to the diameter of one of the inner ends


11




b


and


12




b


of the wires


11




a


and


13




a


, respectively, which are drawn out, and the thickness corresponding to the diameter of the inner end


12




b


of the wire


12




a


which is drawn out is substantially five times the diameter of the wire


11




a


,


12




a


, or


13




a


. Although the thickness of the overall flat coils of the transformer


20


is greater than that of the transformer


10




a


or


10




b


shown in

FIG. 1A

or


1


B, respectively, the transformer


20


can be made thinner than the known transformer


1


shown in

FIG. 10

by a thickness corresponding to the diameter of the wire


11




a


,


12




a


, or


13




a


, whereby the thickness of the overall transformer


20


can be reduced.




The transformer


20


can be reduced in thickness when the inner ends of at least two flat coils are each drawn out over a surface of one of the flat coils


11


,


12


, and


13


.




Although in the transformer


20


shown in

FIG. 4

, the inner ends


11




b


and


13




b


of the two flat coils


11


and


13


, respectively, are each drawn out over the outer side of the outermost flat coil


11


, the two inner ends


11




b


and


13




b


may be drawn out between two flat coils


11


and


12


or


12


and


13


, in the same way as in the transformer


10




a


or


10




b


shown in

FIG. 1A

or


1


B, respectively.





FIG. 5

is an exploded perspective view of a transformer according to a fifth embodiment of the present invention, in which components the same as or corresponding to those of the transformers


10




a


and


10




b


shown in

FIGS. 1A and 1B

, respectively, are referred to with the same reference numerals, for which description is omitted.




A transformer


30


shown in

FIG. 5

is provided with a flat coil


31


in addition to the transformer


10




a


or


10




b


shown in

FIG. 1A

or


1


B, respectively, the flat coil


31


being disposed on the outer side of the flat coil


13


with a doughnut-shaped insulative sheet


32


between the flat coils


13


and


31


. The flat coil


31


is formed by winding a wire in a spiral. An end


31




b


of a wire


31




a


forming the flat coil


31


is drawn to the outside of the transformer


30


through the holes for passing a magnetic core-leg of the insulative sheet


32


, the flat coil


13


, the insulative sheet


15


, the flat coil


12


, the insulative sheet


14


, and the flat coil


11


and over a wound portion of the wire


11




a


of the flat coil


11


. That is, the inner ends


11




b


and


31




b


of the flat coils


11


and


31


, respectively, are each disposed on the same surface of the flat coil


11


. The inner end


12




b


of the wire


12




a


forming the flat coil


12


and the inner end


13




b


of the wire


13




a


forming the flat coil


13


are connected to each other in the holes for passing a magnetic core-leg of the flat coils


12


and


13


and the insulative sheet


15


. The outer ends


11




c


,


12




c


,


13




c


and


31




c


of the four flat coils


11


,


12


,


13


, and


31


, respectively, are drawn to the outside of the transformer


30


at respective levels of the flat coils


11


,


12


,


13


, and


31


.




The thus formed transformer


30


can be reduced in thickness by drawing the inner ends


11




b


and


31




b


of the two flat coils


11


and


31


, respectively, to the outside of the transformer


30


, each inner end


11




b


or


31




b


being disposed on the same surface of the flat coil


11


. The inner ends


12




b


and


13




b


of the two flat coils


12


and


13


, respectively, are connected to each other, whereby the inner ends


12




b


and


13




b


are not necessarily drawn to the outside of the transformer


30


, thereby omitting a process of preparing lead wires, simplifying winding structures, and reducing manufacturing costs of windings.





FIG. 6

is an exploded perspective view of a transformer according to a sixth embodiment of the present invention, in which components the same as or corresponding to the transformer


10




a


or


10




b


shown. in

FIG. 1A

or


1


B, respectively, are referred to with the same reference numerals, for which description is omitted.




In a transformer


40


shown in

FIG. 6

, the outer end


11




c


of the flat coil


11


and the outer end


13




c


of the flat coil


13


are connected to each other.




In the thus formed transformer


40


, the flat coils


11


and


13


can be continuously wound by connecting the outer ends


11




c


and


13




c


of the flat coils


11


and


13


, respectively, to each other, thereby omitting a process of preparing lead wires, simplifying winding structures, and reducing manufacturing costs of windings.





FIG. 7

is an exploded perspective view of a transformer according to a seventh embodiment of the present invention. A transformer


50


shown in

FIG. 7

includes flat coils


51


,


52


, and


53


coaxially overlapping each other, each formed by winding a three-layer insulated wires in a spiral. The flat coils


51


,


52


, and


53


are formed by winding wires


51




a


,


52




a


, and


53




a


, respectively. An inner end


51




b


of the wire


51




a


forming the flat coil


51


is drawn to the outside of the transformer


50


over a wound. portion of the wire


51




a


. An inner end


52




b


of the wire


52




a


forming the flat coil


52


is drawn to the outside of the transformer


50


through a hole for passing a magnetic core-leg of the flat coil


51


and over the wound portion of the wire


51




a


of the flat coil


51


. An end


53




b


of the wire


53




a


forming the flat coil


53


is drawn to the outside of the transformer


50


through the respective holes for passing a magnetic core-leg of the flat coils


52


and


51


and over the wound portion of the wire


51




a


of the flat coil


51


. The inner ends


51




b


,


52




b


, and


53




b


of the flat coils


51


,


52


, and


53


, respectively, are each disposed on the same surface of the flat coil


51


. Outer ends


51




c


,


52




c


, and


53




c


of the three flat coils


51


,


52


, and


53


are drawn to the outside of the transformer


50


at respective levels of the flat coils


51


,


52


, and


53


. The three-layer insulated wire is a conducting wire coated with three layers of insulating materials differing from each other about the conducting wire, thereby providing a high dielectric strength.




The thus formed transformer


50


differs from the transformers


10




a


and


10




b


shown in

FIGS. 1A and 1B

, respectively, in that the transformer


50


is not provided with insulative sheets between the flat coils


51


and


52


and between the flat coils


52


and


53


. This is because the dielectric strength between the flat coils


51


,


52


, and


53


becomes large by virtue of the three-layer insulated wires


51




a


,


52




a


, and


53




a


, whereby the insulative sheets


14


and


15


can be eliminated.




Since the insulative sheets


14


and


15


can be eliminated by using the three-layer insulated wires


51




a


,


52




a


, and


53




a


, the thickness of the transformer


50


can be reduced further.





FIG. 8

is an exploded perspective view of a transformer according to an eighth embodiment of the present invention, in which components the same as or corresponding to those of the transformer


50


shown in

FIG. 7

are referred to with the same reference numerals, for which description is omitted.




In a transformer


60


shown in

FIG. 8

, the inner end


51




b


of the wire


51




a


forming the flat coil


51


is drawn to the outside of the transformer


60


between the flat coils


51


and


52


and over a wound portion of the wire


52




a


of the flat coil


52


. The inner end of the wire


52




a


forming the flat coil


52


is drawn to the outside of the transformer


60


over the wound portion of the wire


52




a


. The inner end


53




b


of the wire


53




a


forming the flat coil


53


is drawn to the outside of the transformer


60


through the hole for passing a magnetic core-leg of the flat coil


52


and over the wound portion of the wire


52




a


of the flat coil


52


. That is, the inner ends


51




b


,


52




b


, and


53




b


of the flat coils


51


,


52


, and


53


, respectively, are disposed between the flat coils


51


and


52


and on the same surface of the flat coil


52


.




In the thus formed transformer


60


in which the inner ends


51




b


,


52




b


, and


53




b


of the three flat coils


51


,


52


, and


53


, respectively, are drawn out between the flat coils


51


and


52


, insulative sheets, for ensuring the dielectric strength between the flat coil


51


and the inner ends


51




b


,


52




b


, and


53




b


and between the inner ends


51




b


,


52




b


, and


53




b


and the flat coil


52


, are not provided because a sufficient dielectric strength is maintained by using the three-layer insulated wires


51




a


,


52




a


, and


53




a


. Therefore, the thickness of the transformer


60


can be reduced further.





FIG. 9

is a perspective view of an electrical apparatus according to a ninth embodiment of the present invention, in which an electrical device


70


is a switching power supply device which uses the transformer


10




a


according to the present invention. The electrical device


70


includes a substrate


71


mounted with the transformer


10




a


according to the present invention, resistors, capacitors, choke coils, etc., and semiconductors such as transistors, diodes, and integrated circuits, these components being connected to each other via wires formed on the substrate


71


.




The thus formed electrical device


70


can be reduced in thickness and in size by reducing the thickness of the transformer


10




a.






Although the switching power supply device is shown in

FIG. 9

as an electrical device, the present invention may be applied to other electrical devices, such as analogue circuits and speaker devices, which use transformers according to the present invention.



Claims
  • 1. A transformer comprising:first and second flat coils being stacked with each other, each of the first and second flat coils comprising a conductive wire which is wound in a flat spiral shape having a through hole at a center thereof such that the conductive wire has an inner end and an outer end at an inner periphery and an outer periphery of the spiral shape, respectively, wherein the inner end of the first flat coil passes through the through hole of the second flat coil.
  • 2. The transformer of claim 1, further comprising third and fourth flat coils each comprising a conductive wire which is wound in a flat spiral shape having a through hole at a center thereof such that the conductive wire has an inner end and an outer end at an inner periphery and an outer periphery of the spiral shape, respectively,wherein the inner end of the third and fourth flat coils are connected with each other.
  • 3. The transformer of claim 1, further comprising third and fourth flat coils each comprising a conductive wire which is wound in a flat spiral shape having a through hole at a center thereof such that the conductive wire has an inner end and an outer end at an inner periphery and an outer periphery of the spiral shape, respectively, wherein the outer end of the third and fourth flat coils are connected with each other.
  • 4. The transformer of claim 1, wherein the wire forming at least one of the first and second flat coils is an insulated wire.
  • 5. The transformer of claim 4, wherein the wire forming at least one of the first and second flat coils is a three layer insulated wire.
  • 6. The transformer of claim 5, wherein said wire is a self-welding-type three-layer insulated wire.
  • 7. The transformer of claim 1, further comprising an insulating sheet having a through hole and being provided between the first and second flat coils, the inner end of the first flat coil passing through the through hole of the insulating layer.
  • 8. The transformer of claim 1, further comprising a core, at least a portion of the core passing through the through holes of the first and second flat coils.
  • 9. The transformer of claim 1, further comprising a third flat coil stacked with the first and second flat coils and comprising a conductive wire wound in a flat spiral shape and having a through hole at a center thereof such that the conductive wire has a an inner and an outer end at an inner periphery and an outer periphery of the spiral shape, respectively, wherein the inner end of the third coil passes through the through hole of at least one of the first and second flat coils.
  • 10. The transformer of claim 9, wherein the inner end of the third coil passes through the through hole of both the first and second flat coils.
  • 11. An electrical device comprising a transformer and a circuit coupled to the transformer, the transformer comprising:first and second flat coils being stacked with each other, each of the first and second flat coils comprising a conductive wire which is wound in a flat spiral shape having a through hole at a center thereof such that the conductive wire has an inner end and an outer end at an inner periphery and an outer periphery of the spiral shape, respectively, wherein the inner end of the first flat coil passes through the through hole of the second flat coil.
  • 12. The electrical device of claim 11, further comprising third and fourth flat coils each comprising a conductive wire which is wound in a flat spiral shape having a through hole at a center thereof such that the conductive wire has an inner end and an outer end at an inner periphery and an outer periphery of the spiral shape, respectively,wherein the inner end of the third and fourth flat coils are connected with each other.
  • 13. The electrical device of claim 11, further comprising third and fourth flat coils each comprising a conductive wire which is wound in a flat spiral shape having a through hole at a center thereof such that the conductive wire has an inner end and an outer end at an inner periphery and an outer periphery of the spiral shape, respectively, wherein the outer end of the third and fourth flat coils are connected with each other.
  • 14. The electrical device of claim 11, further wherein the wire forming at least one of the first and second flat coils is an insulated wire.
  • 15. The electrical device of claim 14, further wherein the wire forming at least one of the first and second flat coils is a three layer insulated wire.
  • 16. The electrical device of claim 15, further wherein said wire is a self-welding-type three-layer insulated wire.
  • 17. The electrical device of claim 11, further comprising an insulating sheet having a through hole and being provided between the first and second flat coils, the inner end of the first flat coil passing through the through hole of the insulating layer.
  • 18. The electrical device of claim 11, further comprising a core, at least a portion of the core passing through the through holes of the first and second flat coils.
  • 19. The electrical device of claim 11, further comprising a third flat coil stacked with the first and second flat coils and comprising a conductive wire wound in a flat spiral shape and having a through hole at a center thereof such that the conductive wire has an inner end and an outer end at an inner periphery and an outer periphery of the spiral shape, respectively, wherein the inner end of the third coil passes through the through hole of at least one of the first and second flat coils.
  • 20. The electrical device of claim 11, further wherein the inner end of the third coil passes through the through hole of both the first and second flat coils.
Priority Claims (1)
Number Date Country Kind
2000-229752 Jul 2000 JP
US Referenced Citations (2)
Number Name Date Kind
5631822 Silberkleit et al. May 1997 A
6211767 Jitaru Apr 2001 B1
Foreign Referenced Citations (1)
Number Date Country
05006829 Jan 1993 JP