Multilayered common-mode choke coil

Details Multilayered common-mode choke coil Multilayered common-mode choke coil

2002-09-04

2004-02-24

Nguyen, Tuyen T. (Department: 2832)

Inductor devices

Coil or coil turn supports or spacers

Printed circuit-type coil

C336S083000

Reexamination Certificate

active

06696911

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to multilayered common-mode choke coils, for example, common-mode choke coils for use with a sound signal.
2. Description of the Related Art
A conventional multilayered common-mode choke coil
60
shown in
FIG. 8
has been known as a common-mode choke coil which prevents noise having the same phase from passing. The common-mode choke coil
60
includes a plurality of coils in which the diameters of coil portions are substantially equal to each other and the axes of the coil portions are aligned collinearly. The multilayered common-mode choke coil
60
includes insulating sheets
61
having surfaces that are provided with coil conductors
62
to
69
, respectively.
The coil conductors
62
to
65
are electrically connected in series through via-holes
75
a
to
75
c
provided in some of the insulating sheets
61
so as to define a spiral coil La having an axis which is parallel to the laminating direction of the insulating sheets
61
. The coil conductors
66
to
69
are electrically connected in series through via-holes
75
d
to
75
f
provided in some of the other insulating sheets
61
so as to define a spiral coil Lb having an axis which is parallel to the laminating direction of the insulating sheets
61
.
The coil conductor
62
has an extended portion
62
a
, which is exposed at the left on the back portion of one of the sheets
61
and which functions as the input-side extended portion of the coil La. The coil conductor
65
has an extended portion
65
a
, which is exposed at the left on the front portion of one of the sheets
61
and which functions as the output-side extended portion of the coil La. Furthermore, a coil portion
62
b
of the coil conductor
62
, the coil conductors
63
and
64
, and a coil portion
65
b
of the coil conductor
65
are spirally wound by 1.75 turns so as to define a coil portion
70
of the coil La.
On the other hand, the coil conductor
69
has an extended portion
69
a
, which is exposed at the right on the back portion of one of the sheets
61
and which functions as the input-side extended portion of the coil Lb. The coil conductor
66
has an extended portion
66
a
, which is exposed at the right on the front portion of one of the sheets
61
and which functions as the output-side extended portion of the coil Lb. Furthermore, a coil portion
66
b
of the coil conductor
66
, the coil conductors
67
and
68
, and a coil portion
69
b
of the coil conductor
69
are spirally wound by 2.25 turns so as to define a coil portion
71
of the coil Lb.
Each of the sheets
61
is laminated and then is integrally baked so that a laminated body
80
as shown in
FIG. 9
is produced. An input electrode
81
a
of the coil La and an input electrode
82
a
of the coil Lb are located on the back surface of the laminated body
80
, and an output electrode
81
b
of the coil La and an output electrode
82
b
of the coil Lb are located on the front surface of the laminated body
80
.
As shown in
FIG. 10
, the input-side extended portion
62
a
of the coil La is electrically connected to the input electrode
81
a
and the output-side extended portion
65
a
is electrically connected to the output electrode
81
b
. Also, the input-side extended portion
69
a
of the coil Lb is electrically connected to the input electrode
82
a
and the output-side extended portion
66
a
is electrically connected to the output electrode
82
b
. The extended portions
62
a
,
65
a
,
66
a
, and
69
a
connect the input/output electrodes
81
a
to
82
b
and the coil portions
70
and
71
linearly with the shortest distance.
In the known common-mode choke coil
60
, a 0.5-turn difference is inevitably caused between the two spiral coils La and Lb. Therefore, the line length of the coil La is different from that of the coil Lb, and thus difference in transmission delay is generated between the coils La and Lb. Consequently, a problem arises, that is, the suppression characteristic of an in-phase signal (in-phase suppression characteristic) is poor. Accordingly, the known common-mode choke coil
60
has been used only for a signal transmission line or a power supply line for a signal in a low frequency band, in which the difference in transmission delay between the coils La and Lb can be ignored.
Recently, however, difference in the number of coil turns cannot be ignored because a transmission signal of higher frequency has been used and a differential signal transmission method has been adopted. For example, in the differential signal transmission method, transmission delay is caused in accordance with the difference in the number of coil turns (difference in the length of transmission line of coils). Also, the balance of differential signal transmission is lost.
SUMMARY OF THE INVENTION
In order to solve the problems described above, preferred embodiments of the present invention provide a multilayered common-mode choke coil in which transmission delay is prevented from occurring in a high-frequency band and a balance of a transmission signal is not lost in differential signal transmission.
According to a preferred embodiment of the present invention, a multilayered common-mode choke coil includes a laminated body having a plurality of insulating layers and a plurality of coil conductors laminated together, and at least two spiral coils which are defined by electrically connecting the coil conductors and which includes extended portions and coil portions. The diameters of the coil portions of the at least two spiral coils are substantially the same, the axes of the coil portions are aligned collinearly, and the two spiral coils are aligned in the laminating direction of the insulating layers. The extended portions of the spiral coils are extended on the insulating layers and junctions of the extended portions and the coil portions are located at substantially the center in a predetermined direction of the insulating layers so that the lengths of the coil portions of the spiral coils are substantially equal to each other.
According to another preferred embodiment of the present invention, a multilayered common-mode choke coil includes a laminated body having a plurality of insulating layers and a plurality of coil conductors laminated together, and three spiral coils which are defined by electrically connecting the coil conductors and which includes extended portions and coil portions. The diameters of the coil portions of the three spiral coils are substantially the same, the axes of the coil portions are aligned collinearly, and the three spiral coils are aligned in the laminating direction of the insulating layers. Each of the three spiral coils preferably has a trifiler configuration. A spiral coil positioned at the approximate center in the laminating direction of the insulating layers is connected to a ground electrode. In two spiral coils positioned at the top and the bottom in the laminating direction of the insulating layers, the extended portions of the spiral coils are extended on the insulating layers and junctions of the extended portions and the coil portions are located at substantially the center in a predetermined direction of the insulating layers so that the lengths of the coil portions of the two spiral coils are substantially equal to each other.
With this arrangement, the junction of each of the extended portions and each of the coil portions of the spiral coils may have a folded configuration. Also, the number of turns and the line length of the spiral coils are substantially equal so that a difference in delay of signal transmission between the coils can be prevented.
Preferably, when the laminated body is seen through, the junctions of the extended portions and the coil portions of the plurality of spiral coils do not overlap. With this arrangement, a local internal stress caused at the junctions of the extended portions and the coil portions is dispersed when the laminated body, which is constructed by laminating the insulating layers and the coil conducto

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