Choke coil

Details Choke coil Choke coil

2002-09-05

2003-09-09

Nguyen, Tuyen T. (Department: 2832)

Inductor devices

Winding formed of plural coils

Two windings

C336S170000, C336S206000, C336S222000

Reexamination Certificate

active

06617949

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority based on Japanese Patent Application No. 2001-268909 filed on Sep. 5, 2001, the contents of which are herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a choke coil having a coil pair having winding ratio of 1:1. More particularly, the invention relates to a choke coil to be effectively used in a band-pass filter used as inserted in a transmission line balanced with respect to the ground, such as a telephone circuit and so forth.
2. Description of the Related Art
For example, in ADSL (Asymmetric Digital Subscriber Line) in which superimposed a high speed digital signal on a telephone circuit, a branching filter called as splitter is employed for separating a telephone signal and a digital signal. The branching filter is constructed with an LPF (low-pass filter) selectively passing a frequency band of the telephone signal and an HPF (high-pass filter) selectively passing a frequency band of the digital signal.
On the other hand, the telephone circuit, in which the branching filter is used, is typically a transmission line balanced with respect to the ground. Upon forming a BPF (band-pass filter), such as LPF, HPF and the like, it is essential to certainly achieve unbalance attenuation amount with respect to the ground in order to restrict adverse effect of potential fluctuation in a grounding layer and loop noise with the ground.
As shown by winding structure and equivalent circuits of a choke coil in
FIGS. 4A
,
4
B,
4
C and
4
D,
4
E and
4
F, a choke coil is constituted by winding a coil pair L
1
and L
2
in one coil with a winding ratio of 1:1. Both coils L
1
and L
2
are wound on a common core (magnetic core) in a single coil bobbin. Various winding structures may be employed as shown in
FIGS. 4A
to
4
F.
The coil shown in
FIG. 4A
includes a first coil L
1
and a second coil L
2
forming the coil pair having winding ratio of 1:1. The first and second coils L
1
and L
2
are wound inside and outside separated by an intermediate insulation layer
2
. The first coil L
1
is wound predetermined turns n
1
inside of the intermediate insulation layer
2
. On the other hand, the second coil L
2
is wound predetermined turns n
2
(n
1
=n
2
) outside of the intermediate insulation layer
2
. By this, the choke coil having the coil pair L
1
and L
2
having winding ratio of n
1
:n
2
=1:1, is formed. It should be noted that outermost side of the coil is covered with an insulation layer
29
.
The coil shown in
FIG. 4B
includes the first and second coils L
1
and L
2
having predetermined turns n
1
and n
2
. Respective first and second coils L
1
and L
2
are dividedly wound the predetermined turns n
1
and n
2
into two coil segments respectively having number of turns half of the predetermined turns n
1
and n
2
. From inside to outside, a first coil segment L
11
of the first coil L
1
, a first coil segment L
21
of the second coil L
2
, a second coil segment L
12
of the first coil L
1
and a second coil segment L
22
of the second coil L
2
are sequentially wound in sequentially stacked manner. Between respectively adjacent coil segments L
11
, L
21
, L
12
and L
22
, intermediate insulation layers
2
are interposed for insulation therebetween. Winding numbers n
11
, n
21
, n
12
and n
22
of the coil segments L
11
, L
21
, L
12
and L
22
are the same (n
11
=n
21
=n
12
=n
22
) as each other. By this, the coil pair L
1
and L
2
having the winding ratio 1:1 is formed.
The coil shown in
FIG. 4C
also includes the first and second coils L
1
and L
2
, wherein the first coil L
1
is separated into the first coil segment L
11
and the second coil segment L
12
which are arranged on innermost side and outermost side. Between the first and second coil segments L
11
and L
12
of the first coil L
1
, the first and second coil segments L
21
and L
22
of the second coil L
2
are wound simultaneously.
The coil shown in
FIG. 4D
has a partitioning wall portion
11
dividing a spool portion of the coil bobbin
1
into two sections. In respective sections, the first and second coils L
1
and L
2
are separately wound by the predetermined turns n
1
and n
2
(n
1
=n
2
).
The coil shown in
FIG. 4E
is also provided with the partitioning wall portion
11
dividing the spool of the coil bobbin
1
into two sections. In one of the divided spool sections, the first coil segment L
11
of the first coil L
1
and the first coil segment L
21
of the second coil L
2
are wound in stacking manner with insulation by the intermediate insulation layer
2
. In the other divided spool section, the second coil segment L
12
of the first coil L
1
and the second coil segment L
22
of the second coil L
2
are wound in stacking manner with insulation by the intermediate insulation layer
2
.
In the coil shown in
FIG. 4F
, the first coil L
1
and the second coil L
2
are simultaneously wound by respectively predetermined turns n
1
and n
2
(n
1
=n
2
).
As set forth above, there have been proposed various manners of winding in the common mode choke coil.
In the conventional choke coil set forth above, the inventors have found the following problems to be encountered.
Namely, in case of the coils shown in
FIGS. 4A and 4B
, while number of turns n
1
and n
2
of the first and second coils L
1
and L
2
are the same with each other to have 1:1 of winding ratio, difference of wire wound resistances due to difference of winding diameters of the first and second coils L
1
and L
2
is significant to cause difficulty in obtaining sufficient unbalance attenuation amount with respect to the ground.
In case of the coil shown in
FIG. 4C
, the first and second coils L
1
and L
2
are divided into two segments, respectively. The first and second coil segments L
21
and L
22
of the second coil L
2
are simultaneously wound. Therefore, winding operation is complicated and difficult to increase process steps.
In case of the coils shown in
FIGS. 4D and 4E
, the bobbin provided with the partitioning wall portion
11
dividing the spool into two sections becomes necessary. Furthermore, in comparison with the divided winding structure (so-called sandwich structure) of coaxially stacking manner shown in
FIG. 4A
or
4
B, a leakage inductance between the first and second coils L
1
and L
2
becomes large. If the leakage inductance becomes large, when the band-pass filter, such as LPF or the like is formed, good transmission characteristics cannot be obtained in a pass frequency band (pass band).
In case of the coil shown in
FIG. 4F
, line capacity between the first and second coils L
1
and L
2
becomes large. When the line capacity becomes large, if the band-pass filter is formed, good attenuation characteristics cannot be obtained at a blocking frequency band (out of pass-band).
As set forth above, the aforementioned conventional choke coils cause problems in unbalance attenuation amount with respect to the ground, workability in winding, leakage inductance, line capacity and so forth. Conventionally, it is quite difficult to clear up all of the problems set forth above.
SUMMARY OF THE INVENTION
The present invention has been worked out in view of the above and other problems. Therefore, it is an object of the present invention to provide a choke coil which has small difference of wire wound resistances between coils to obtain sufficient unbalance attenuation amount, has superior in workability in winding and reduce leakage inductance and line capacity.
According to one aspect of the present invention, a choke coil including a coil pair having a winding ratio of 1:1, comprises:
first and second coils forming the coil pair, respective of the first and second coils being divided into first and second segments wound on a single spool disposing intermediate insulations layers between respectively adjacent coil segments, the first and second coil segments being stackingly wound in sequential order of the firs

Affiliated with

Also associated with

Rating

Choke coil does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Choke coil, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Choke coil will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3049092