JP3085122B2 - choke coil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a choke coil mainly used for removing noise flowing out of an electronic device or the like.

[0002]

2. Description of the Related Art In general, a common mode choke coil has a small amount of a normal mode leakage inductance component, and thus is effective for normal mode noise. Separately, it was necessary to take countermeasures against noise using a normal mode choke coil.

[0003] In the case of a common mode choke coil having a relatively large leakage inductance component in a normal mode, the leakage magnetic flux may have an adverse effect on peripheral circuits. For this reason, it is necessary to take measures such as applying a magnetic shield to the outer periphery of the common mode choke coil.

[0004]

The conventional choke coil cannot sufficiently remove both the common mode noise and the normal mode noise with a single choke coil, and therefore removes the common mode noise and the normal mode noise. For this purpose, two choke coils, that is, a common mode choke coil and a normal mode choke coil must be mounted on a printed circuit board or the like, and there is a problem that the area occupied by the printed circuit board or the like is large.

Further, providing a magnetic shield on the outer periphery of the choke coil also increases the cost of the choke coil. Therefore, an object of the present invention is to provide a choke coil having a sufficient noise removing effect on common mode noise and normal mode noise.

[0006]

In order to achieve the above object, a choke coil according to the present invention comprises: (a) a pair of windings; and (b) a cylindrical body around which the pair of windings is wound. And a bobbin made of a magnetic material having a closed magnetic path surrounding each of the pair of windings, and (c) a magnetic core forming a closed magnetic path having one side inserted through a hole in the cylindrical body. (D) the position of the hole of the cylindrical body is eccentric with respect to the cylindrical body.

[0007]

In the above construction, when a common mode noise current flows through a pair of windings, a magnetic flux is generated in each winding. The magnetic fluxes are added to each other and converted into thermal energy in the form of an eddy current loss and attenuated in the magnetic core forming the closed magnetic path. Thereby, the common mode noise current is removed. On the other hand, when a normal mode noise current flows through the pair of windings, a magnetic flux is generated in the windings. This magnetic flux goes around the closed magnetic path of the bobbin, is converted into thermal energy in the form of eddy current loss or the like, and is attenuated. Thereby, the normal mode noise current is removed.

Further, since the bobbin has an eccentric hole with respect to the cylindrical body, the thickness of the cylindrical body of the bobbin inside the opening of the magnetic core is small, and the cylindrical body of the bobbin outside the opening is small. Becomes thicker. Therefore, in the opening of the magnetic core, the area occupied by the bobbin is reduced, and the area where the winding can be wound around the body of the bobbin increases accordingly, and the normal mode and common mode inductances increase. Become. Outside the opening of the magnetic core, the cross-sectional area of the magnetic path of the bobbin increases, so that the magnetic resistance of this magnetic path decreases and the inductance in the normal mode increases.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a choke coil according to the present invention will be described below with reference to the accompanying drawings. 1 and 2
1 is a side view and a front view of a bobbin 1 used in the choke coil of the present embodiment. The bobbin 1 includes a square tubular body 11, flanges 12, 13, and 14 provided at both ends and a center of the body 11, and a lid 15 joined to outer peripheral end surfaces of the flanges 12 to 14. Have been.

The hole 11a of the cylindrical body 11 is provided eccentrically near the corner with respect to the body 11. The cross section of the hole 11a is circular. However, it goes without saying that the shape of the cross section of the hole is arbitrary and may be rectangular. A protrusion 16 for fixing the magnetic core is provided near the hole 11a on the upper part of the flanges 12 and 13, and a terminal mount 17 is provided on the lower part. Terminals 18 are implanted on the terminal mount 17.

As shown in FIG. 3, the lid 15 has a U-shaped cross section. After windings 4 and 5 described later are wound around the body 11 of the bobbin 1, the lid 15 is coated with an adhesive or the like. Flange 12-14
Is joined to the outer peripheral end face. As the material of the bobbin 1, an insulating magnetic material having a relative magnetic permeability of 1 or more (for example, 2 to several tens) is used. Specifically, a material obtained by kneading a Ni-Zn or Mn-Zn ferrite and a resin binder is used.

FIGS. 4 and 5 show a choke coil using the bobbin 1 having the above structure. The choke coil includes a bobbin 1, a pair of windings 4 and 5 wound around the bobbin 1, and two U-shaped magnetic cores 6 and 7, respectively. The pair of windings 4 and 5 are respectively
Are wound around the flange portion 14 with the flange portion 14 interposed therebetween, and the respective start and end portions are fixed to different terminals 18.

In FIG. 5, the bobbin 1 forms a closed magnetic path around the winding 4 by the left half of the body 11, the flange 12, the left half of the lid 15 and the flange 14, and the right side of the body 11. The half, the flange 13, the right half of the lid 15, and the flange 14 constitute a closed magnetic circuit that goes around the winding 5. The magnetic cores 6, 7 are
The bobbin 1 is joined in a state where it is inserted into the hole 11a of the body 11 to form a square-shaped core. The magnetic cores 6 and 7 are regulated by magnetic core fixing projections 16 provided on the bobbin 1 and are disposed substantially vertically. The thickness t ₁ of the body 11 inside the opening 8 formed by the magnetic cores 6 and 7 is smaller than the thickness t ₂ of the body 11 outside the opening. The lid 15 of the bobbin 1 is joined to the flanges 12 to 14 from the side opposite to the side where the magnetic cores 6 and 7 are provided. Core 6,7
Preferably, the material has a relative magnetic permeability of several thousands, and specifically, ferrite, amorphous, or the like is used.

In the choke coil having the above configuration, the hole 11a is eccentric with respect to the body 11, so that the area occupied by the bobbin 1 in the opening 8 of the magnetic cores 6, 7 is reduced. Accordingly, the area where the windings 4 and 5 can be wound around the body 11 of the bobbin 1 is increased by that much, and the normal mode and common mode inductances can be increased. Outside the openings of the magnetic cores 6 and 7, the cross-sectional area of the magnetic path of the bobbin 1 becomes large.
The magnetic resistance of this magnetic path decreases, and the inductance in the normal mode increases. As a result, it is possible to obtain a choke coil that can sufficiently exhibit a noise removing effect on common mode noise and normal mode noise.
FIG. 6 is an electric equivalent circuit diagram of the choke coil.

Here, the common mode noise removing action of the choke coil having the above configuration will be described with reference to FIGS.
This will be described with reference to FIG. As shown in FIG. 7, the choke coil is electrically connected to two signal lines provided between a power supply 20 and a load 21 such as an electronic device. A stray capacitance C1 is generated between the power supply 20 and the ground, and a stray capacitance C2 is generated between the load 21 and the ground. When the common mode noise currents i ₁ and i ₂ flow in the two signal lines in the direction of the arrow in the figure, as shown in FIG.
φ2 occurs. The magnetic fluxes φ1 and φ2 are added to each other and orbit inside the closed magnetic paths of the cores 6 and 7, and gradually attenuate without leaking to other parts. This is because the magnetic fluxes φ1 and φ2 are converted into thermal energy in the form of eddy current loss or the like. This allows
The common mode noise currents i ₁ and i ₂ are reduced.

Next, the normal mode noise removing operation of the choke coil will be described with reference to FIGS. As shown in FIG. 9, the normal mode noise current i ₃
Flows through the two signal lines in the directions of the arrows in the figure, as shown in FIG. The magnetic fluxes φ3 and φ4 are converted into thermal energy in the form of eddy current loss and the like, and gradually attenuate while circulating in the closed magnetic circuit of the bobbin 1 without leaking. Thereby, the normal mode noise current i ₃ is reduced.

As shown in FIG. 11, the magnetic cores 6 and 7 are connected to the magnetic core fixing projections 16 and the terminal mount 1.
7 and may be arranged substantially horizontally. In this case, the lid 15 of the bobbin 1 is joined to the flanges 12 to 14 from the side opposite to the side where the magnetic cores 6 and 7 are provided. The choke coil having the structure shown in FIG. 11 occupies a larger area on a printed circuit board and the like than the choke coil shown in FIG. 4, but has the advantage that the height can be reduced.

The choke coil according to the present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the invention. The eccentric position of the hole in the cylindrical body of the bobbin is arbitrary. For example, as shown in FIG.
What is necessary is just to provide 1a in the position near the center part upper part. Where 3
Reference numeral 1 denotes a guide groove for a magnetic core. FIG.
As shown in FIG. 3, when the magnetic cores 6 and 7 are always arranged in a horizontal state, the hole 11a may be provided at a position closer to the left of the center. Here, reference numeral 32 denotes a magnetic core guide groove.

The bobbin does not need to be one common bobbin for a plurality of windings, and may be a plurality of independent bobbins corresponding to each of the windings. May have a cylindrical shape or a rectangular tube shape. Further, the magnetic core may be a combination of two U-shaped cores or E-shaped cores, or a combination of a U-shaped core or E-shaped core with an I-shaped core. Alternatively, the core is not limited to a split type, but may be an integral type, for example, a Japanese character core or a square character core.

[0020]

As is apparent from the above description, according to the present invention, there is provided a bobbin made of a magnetic material having a closed magnetic path surrounding each of a pair of windings, and a closed magnetic path formed through the bobbin. Since a magnetic core is provided, the magnetic flux generated by the common mode noise current and the normal mode noise current flowing through the pair of windings is converted into thermal energy in the form of eddy current loss etc. in the magnetic body or bobbin, respectively. It is converted and attenuated, thereby removing common mode noise and normal mode noise. Further, since the magnetic flux does not leak out of the choke coil, a magnetic shield on the outer periphery of the choke coil is not required.

Further, since the position of the hole of the cylindrical body of the bobbin is eccentric with respect to the cylindrical body, the cross section of the magnetic path through which the magnetic flux generated in the bobbin by the normal mode noise passes becomes large. The magnetic resistance of the road decreases. Therefore, a large normal mode inductance can be obtained. further,
Since the ratio of the bobbin in the opening of the magnetic core is small, the number of windings can be increased by that much, and the normal mode and common mode inductances can be increased.

As a result, a choke coil having a sufficient noise removing effect on common mode noise and normal mode noise can be obtained.

[Brief description of the drawings]

FIG. 1 is a side view of a bobbin used in an embodiment of a choke coil according to the present invention.

FIG. 2 is a front view of the bobbin shown in FIG.

FIG. 3 is a perspective view of a lid of the bobbin shown in FIG. 1;

FIG. 4 is a side view showing one embodiment of the choke coil according to the present invention.

FIG. 5 is a sectional view of the choke coil shown in FIG. 4;

6 is an electric equivalent circuit diagram of the choke coil shown in FIG.

FIG. 7 is an electric circuit diagram for explaining common mode noise removal by the choke coil shown in FIG. 5;

8 is a magnetic circuit diagram for explaining common mode noise removal by the choke coil shown in FIG.

FIG. 9 is an electric circuit diagram for explaining normal mode noise removal by the choke coil shown in FIG. 5;

10 is a magnetic circuit diagram for explaining normal mode noise removal by the choke coil shown in FIG.

FIG. 11 is a side view showing a modification of the choke coil shown in FIG. 5;

FIG. 12 is a side view of a bobbin used in another embodiment.

FIG. 13 is a side view of a bobbin used in another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Bobbin 4, 5 ... Winding 6, 7 ... Magnetic core 11 ... Cylindrical trunk | drum 11a ... Hole 12, 13, 14 ... Flange 15 ... Lid

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Iwao Fukuya 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Murata Manufacturing Co., Ltd. (56) References JP-A-7-263238 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01F 17 / 06,27 / 02

Claims (1)

(57) [Claims] A pair of windings; a cylindrical body around which the pair of windings is wound;
A bobbin made of a magnetic material having a closed magnetic path that goes around each of the pair of windings; and a magnetic core formed of a closed magnetic path having one side inserted through a hole in the cylindrical body, the cylindrical body. the magnetic relative to the tube-shaped body portion position of the hole of
The magnetic body core is eccentric to the side on which the
Of the cylindrical body of the bobbin in the opening formed by
The thickness is relatively thin, and the outside of the opening of the magnetic core is
The tubular body of the bobbin has a relatively large wall thickness .