JP3580061B2 - choke coil - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a choke coil, and more particularly to a choke coil used for removing noise generated from an electronic device or the like and noise entering the electronic device or the like.
[0002]
[Prior art]
Conventionally, a common mode choke coil is used to remove common mode noise when taking measures against noise in signal lines and power supply lines, and a normal mode choke is used in addition to the common mode choke coil to remove normal mode noise. Coil had to be used separately. For this reason, a large occupied area is required, and the number of parts is increased, resulting in high cost.
[0003]
Therefore, assuming that both a common mode noise and a normal mode noise can be removed by one choke coil, as shown in FIG. 9, a square-shaped magnetic member provided with protrusions 62a and 62b close to the center. A choke coil 61 including a body core 62 and a pair of windings 63 and 64 wound around legs 62c and 62d of the magnetic core 62 has been proposed. The choke coil 61 increases the leakage magnetic flux by the protrusions 62a and 62b, and obtains a relatively large inductance in the normal mode. In FIG. 9, φ1 and φ2 indicate the magnetic flux generated when a common mode noise current flows through the windings 63 and 64, respectively, and φ3 and φ4 indicate when the normal mode noise current flows through the windings 63 and 64, respectively. Is displayed.
[0004]
[Problems to be solved by the invention]
However, in the choke coil 61, a magnetic path through which the magnetic fluxes φ1 and φ2 generated by the common mode noise current pass through the magnetic core 62 and a magnetic path through which the magnetic fluxes φ3 and φ4 generated by the normal mode noise current pass. Are partially common, causing the following problems.
[0005]
(1) In order to maintain a large common mode inductance even in a low frequency region, it is necessary to use ferrite or the like having a large relative magnetic permeability as the material of the magnetic core 62. However, since ferrite is easily saturated, the magnetic core 62 is immediately saturated by the magnetic fluxes φ3 and φ4 generated by the normal mode noise current. For this reason, the inductance of the common mode is reduced, and it cannot be used for a signal line or the like through which a large normal signal current flows.
[0006]
(2) On the contrary, when silicon steel or dust having a small relative magnetic permeability is used as a material of the magnetic core 62, saturation of the magnetic core 62 is less likely to occur, but a large common mode required for common mode noise elimination is obtained. No inductance could be obtained.
In order to solve these problems, a choke coil including a core dedicated to normal mode inductance and a core dedicated to common mode inductance has been proposed. However, in this choke coil, it is necessary to provide two bobbins to make a magnetic path through which a magnetic flux generated by a normal mode noise current passes and a magnetic path through which a magnetic flux generated by a common mode noise current passes. However, there is a problem that the number of components increases. Further, there is also a problem that the winding area of the winding is small compared to the size of the entire choke coil, and the size of the choke coil is increased if a large inductance is to be obtained.
[0007]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a small choke coil having less characteristic deterioration due to saturation and having sufficient common mode and normal mode inductance.
[0008]
[Means and Actions for Solving the Problems]
In order to achieve the above object, the choke coil according to the present invention is:
(A) a bobbin made of a non-magnetic insulating material , comprising: a tubular portion having extending portions at both ends; and a flange provided at both ends and a central portion of the tubular portion;
(B) a pair of windings wound around the outer periphery of the cylindrical portion including the outer periphery of the extending portion ;
(C) a first magnetic core having a closed magnetic path formed of a high magnetic permeability material and having one side inserted through the hole of the cylindrical portion;
(D) One magnetic core piece inserted into a hole provided substantially parallel to the hole of the cylindrical portion in each of the extending portions, and combined with the one magnetic core piece to form a closed magnetic path. A second magnetic core made of a low-permeability material constituted by another magnetic core piece;
It is characterized by having.
[0009]
With the above configuration, when a common mode noise current flows through a pair of windings, a magnetic flux is generated by the common mode noise current. The magnetic fluxes are added to each other to form a magnetic path around which the magnetic flux circulates in the first magnetic core, and are converted into thermal energy in the form of eddy current loss and attenuated in the first magnetic core. Thereby, the common mode noise current is removed. When a normal signal current flows through the pair of windings, a magnetic flux is generated by the normal signal current. The magnetic fluxes cancel each other in the first magnetic core. Therefore, this choke coil does not form a magnetic path in the first magnetic core for a normal signal current.
[0010]
On the other hand, when a normal mode noise current flows through the pair of windings, a magnetic flux is generated by the normal mode noise current. This magnetic flux circulates in the second magnetic core, is converted into thermal energy in the form of eddy current loss, and is attenuated. Thereby, the normal mode noise current is removed.
Further, the choke coil according to the present invention is characterized in that the width of the middle leg of the second magnetic core is substantially twice the width of the outer leg and the joint of the second magnetic core. Since the magnetic path through which the magnetic flux generated in each of the pair of windings by the normal mode noise current passes has a common middle leg of the second magnetic core, the width of the middle leg is set to approximately 2 times the width of the other portions. By setting it to twice, the magnetic flux density in the second magnetic core becomes the same value in any part. Therefore, local saturation in the second magnetic core is eliminated, and a decrease in inductance in the normal mode is suppressed.
[0011]
Further, in the choke coil according to the present invention, the distance between the first magnetic core and the second magnetic core is A, and the tip of the outer leg of the second magnetic core passes through the joint to reach the distal end of the middle leg. When the length of the magnetic path is B and the relative magnetic permeability of the second magnetic core is μ, A ≧ B / 2μ is satisfied. According to the above configuration, the magnetic resistance between the first magnetic core and the second magnetic core is increased by the magnetic resistance of the magnetic path extending from the tip of the outer leg of the second magnetic core to the tip of the middle leg through the joint. Be larger. Therefore, there is no fear that the magnetic flux generated by the normal mode noise current leaks from the second magnetic core to the first magnetic core, and the magnetic flux due to the normal mode noise current does not saturate the first magnetic core. As a result, a decrease in common mode inductance is suppressed.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a choke coil according to the present invention will be described with reference to the accompanying drawings.
As shown in FIGS. 1 and 2, the choke coil 1 generally includes a bobbin 2, magnetic cores 3 and 4, and a pair of windings 5 and 6. The bobbin 2 includes a tubular portion 21 having extending portions 21 a and 21 b projecting toward the front side at both ends, flanges 22 and 23 provided at both ends of the tubular portion 21, and a central portion of the tubular portion 21. And flange portions 24, 25, and 26 provided on the front side. Holes 28 and 29 are provided in the extending portions 21a and 21b, respectively. In the case of the present embodiment, the hole 27 of the cylindrical portion 21 and the holes 28, 29 of the extending portions 21a, 21b have a rectangular cross section, the cylindrical portion 21 has a substantially rectangular cross section, and the flange portions 22 to 26 Has a substantially rectangular shape. However, it goes without saying that the present invention is not necessarily limited to these shapes.
[0013]
Windings 5 and 6 are wound around the outer periphery of the cylindrical portion 21. That is, the winding 5 has a winding area in the right half (between the flanges 22 and 26) of the cylindrical portion 21 and is further divided into the first winding portion 5a and the second winding portion 5b by the flange 24. Have been. Similarly, the winding 6 is configured such that a region on the left half (between the flange portions 23 and 26) of the cylindrical portion 21 is a winding region, and is divided into a first winding portion 6a and a second winding portion 6b by the flange portion 25. Have been. The first winding portions 5a and 6a are wound around both ends of the cylindrical portion 21 having the extending portions 21a and 21b. In this manner, the first winding portions 5a and 6a are wound around one side of the magnetic cores 3 and 4 described below, and the second winding portions 5b and 6b are wound around one side of the magnetic core 3. Will be. The start and end of each of the windings 5 and 6 are fixed to and electrically connected to four pin terminals 18 implanted at the bottom of the bobbin 2.
[0014]
The bobbin 2 is made of a non-magnetic material, for example, an insulator material. Specifically, a polybutylene terephthalate resin, a polyphenylene sulfide resin, a polyethylene terephthalate resin, or the like is used. Since the bobbin 2 having a complicated shape composed of the cylindrical portion 21 and the flange portions 22 to 26 is molded using a non-magnetic material that is easy to mold, advanced technology and strict management of manufacturing conditions are required. There is no need to mold using a magnetic material, and the bobbin 2 can be easily manufactured.
[0015]
The magnetic core 3 has a rectangular shape formed by abutting U-shaped magnetic core pieces 11 and 12, and one side thereof is inserted into the hole 27 of the cylindrical portion 21. The material of the magnetic core 3 preferably has a relative magnetic permeability of several thousands, and specifically, ferrite, amorphous, or the like is used.
[0016]
The magnetic core 4 has a Japanese character shape formed by abutting an I-shaped magnetic core piece 13 and an E-shaped magnetic core piece 14. 21b are inserted through holes 28 and 29, respectively. The E-shaped magnetic core piece 14 includes a middle leg portion 14a, outer leg portions 14b and 14c, and a joint portion 14d that connects the three leg portions 14a to 14c. The middle leg portion 14a is disposed between the two extending portions 21a and 21b of the bobbin 2, and the outer leg portions 14b and 14c are disposed outside the flange portions 22 and 23, respectively. The width W2 of the outer legs 14b, 14c and the joint 14d of the E-shaped magnetic core piece 14 is equal to the width W2 of the I-shaped magnetic core piece 13 and is equal to the width W2 of the E-shaped magnetic core piece 14. The width is set to approximately half of the width W1 of the leg 14a. As the material of the magnetic core 4, a magnetic material having a relative permeability of 1 or more (for example, 2 to several tens) is used. Specifically, kneaded silicon steel, dust, Ni-Zn or Mn-Zn ferrite powder and a resin binder are used. When ferrite, amorphous, or the like having a large relative magnetic permeability is used as the magnetic core 4, for example, as shown in FIG. 6, the length of the middle leg portion 14a of the E-shaped magnetic core piece 14 is slightly shortened. A predetermined gap G may be formed between the I-shaped magnetic core piece 13 and the I-shaped magnetic core piece 13 so as to prevent saturation.
[0017]
The distance between the magnetic material core 3 and the magnetic material core 4 is defined as A, and the tip of the outer leg portion 14b (or 14c) of the E-shaped magnetic material core piece 14 passes through the joint portion 14d to the tip of the middle leg portion 14a. Assuming that the length of the magnetic path to be reached is B, the length is set so as to satisfy the following relational expression (1).
A ≧ B / 2μ (1)
However, μ: relative magnetic permeability of the magnetic core 4 These components 2 to 6 are fixed with an adhesive or a varnish as required.
[0018]
In the choke coil 1 having the above configuration, large winding regions of the windings 5 and 6 are secured in a space region surrounded by the magnetic core 3 and a space region surrounded by the magnetic core 4, respectively. That is, the right half of the space region surrounded by the magnetic core 3 is a winding region of the winding 5, and the left half is a winding region of the winding 6. The right space region of the two space regions surrounded by the magnetic core 4 is a winding region of the first winding portion 5 a of the winding 5, and the left space region is the first winding region of the winding 6. This is a winding area of the wire portion 6a. Accordingly, the ratio of the winding regions of the windings 5 and 6 to the entire choke coil 1 increases, and a large normal mode inductance and a large common mode inductance can be obtained without increasing the size of the choke coil 1. it can. Further, since the choke coil 1 has one bobbin 2, the number of components is small, and the winding operations of the windings 5 and 6 can be simultaneously performed, thereby improving workability.
[0019]
FIG. 3 is an electric equivalent circuit diagram of the choke coil 1 having the above configuration. In FIG. 3, L _C represents the inductance component of the common mode, L _N represents the inductance component of the normal mode.
Next, the common mode noise removing operation of the choke coil 1 will be described with reference to FIGS.
[0020]
As shown in FIG. 4B, the choke coil 1 is electrically connected to two signal lines disposed between a power supply 30 and a load 31 such as an electronic device. A stray capacitance C1 is generated between the power supply 30 and the ground, and a stray capacitance C2 is generated between the load 31 and the ground. When common mode noise currents i ₁ and i ₂ flow in the two signal lines in the directions of arrows in the figure, magnetic fluxes φ 1 and φ 2 are generated in the windings 5 and 6 as shown in FIG. The magnetic fluxes φ1 and φ2 are added to each other and gradually attenuate while passing through the magnetic core 3. This is because the magnetic fluxes φ1 and φ2 are converted into thermal energy in the form of eddy current loss or the like. Thereby, the common mode noise currents i ₁ and i ₂ are reduced.
[0021]
Incidentally, when the winding 5 and 6 flows normalized signal current _{i S,} flux .phi.3, .phi.4 is caused by the normal signal current _{i S.} The directions of the magnetic fluxes φ3 and φ4 are opposite in the magnetic material core 3 and cancel each other. Therefore, the magnetic flux φ3 to the magnetic core 3, a magnetic path φ4 passes is not formed, the choke coil 1 has no effect nothing against normal signal current i _S.
[0022]
Next, the normal mode noise removal of the choke coil 1 will be described with reference to FIGS.
FIG 5 (b) as shown in, when the normal mode noise current i ₃ flows two signal lines in the direction of the arrow respectively view, as shown in FIG. 5 (a), the winding 5 and 6 flux .phi.5, φ6 occurs. The magnetic fluxes φ5 and φ6 are converted into thermal energy in the form of eddy current loss and the like while circulating in a closed magnetic path formed in the magnetic core 4, and are gradually attenuated. Accordingly, the normal mode noise current i ₃ is reduced.
[0023]
At this time, the magnetic paths through which the magnetic fluxes φ5 and φ6 pass share the middle leg portion 14a of the E-shaped magnetic core piece 14. However, the width W2 of the middle leg portion 14a of the E-shaped magnetic core piece 14 is approximately twice the width W1 of the outer leg portions 14b, 14c and the joint portion 14d and the width W1 of the I-shaped magnetic core piece 13. Since it is set, the magnetic flux density in the magnetic core 4 can be set to the same value in any part. Therefore, local saturation in the magnetic core 4 is eliminated, and a decrease in inductance in the normal mode can be suppressed.
[0024]
Further, since the choke coil 1 satisfies the condition of the relational expression (1), the magnetic resistance between the magnetic core 3 and the magnetic core 4 is reduced by the outer leg of the E-shaped magnetic core piece 14. The magnetic resistance is larger than the magnetic resistance of the magnetic path from the tip of the portion 14b (or 14c) to the tip of the middle leg 14a through the joint 14d. Therefore, the magnetic fluxes φ5 and φ6 generated in the magnetic core 4 by the normal signal current i _S do not leak from the magnetic core 4 to the magnetic core 3, and the magnetic fluxes φ5 and φ6 do not saturate the magnetic core 3. . As a result, the common mode inductance does not decrease, and the common mode noise current reducing ability of the choke coil 1 does not decrease.
[0025]
It should be noted that the choke coil according to the present invention is not limited to the above embodiment, but can be variously changed within the scope of the gist.
The shapes of the magnetic cores 3 and 4 are variously selected according to specifications. For example, the magnetic material core 3 may be a Japanese character-shaped magnetic material core formed by joining two E-shaped magnetic materials.
[0026]
In the above embodiment, the windings 5 and 6 are divided into first winding portions 5a and 6a and second winding portions 5b and 6b, respectively. However, as shown in FIG. , 6a alone. When the windings 5 and 6 are divided into the first winding portions 5a and 6a and the second winding portions 5b and 6b, the common mode inductance and high frequency characteristics are improved as shown in FIG. 8, a solid line 41 is a graph showing the frequency characteristics of the choke coil 40 shown in FIG. 7, and a dotted line 42 is a graph showing the frequency characteristics of the choke coil 1 shown in FIG.
[0027]
【The invention's effect】
As apparent from the above description, according to the present invention, the first magnetic core made of a high magnetic permeability material having one side inserted through the hole of the cylindrical portion of the bobbin, and the hole provided in the extending portion of the bobbin Since the second magnetic core made of a low magnetic permeability material having one side inserted therein is provided, common mode noise current can be removed in the first magnetic core, and normal mode noise can be eliminated in the second magnetic core. Noise current can be eliminated. A large winding area can be secured in each of the region surrounded by the first magnetic core and the region surrounded by the second magnetic core, and large common mode and normal mode inductances are provided. A small choke coil can be obtained. Further, since only one bobbin is required for the choke coil, the number of components is small, and the winding work of each of the pair of windings can be simultaneously performed, thereby improving workability.
[0028]
Further, by setting the width of the middle leg of the second magnetic core to approximately twice the width of the outer leg and the joint of the second magnetic core, local saturation in the second magnetic core is achieved. Can be prevented, and a decrease in inductance in the normal mode can be suppressed. Further, by setting the first magnetic core so that the relational expression (1) is satisfied, the magnetic flux generated by the normal signal current does not leak from the second magnetic core to the first magnetic core, and the common mode Can be reduced. As a result, a choke coil with less characteristic deterioration due to saturation can be obtained.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing an embodiment of a choke coil according to the present invention.
FIG. 2 is a perspective view showing the appearance of the choke coil shown in FIG.
FIG. 3 is an electric equivalent circuit diagram of the choke coil shown in FIG.
4A and 4B are diagrams for explaining common mode noise removal by the choke coil shown in FIG. 2, wherein FIG. 4A is a magnetic circuit diagram, and FIG. 4B is an electric circuit diagram.
5A and 5B are diagrams illustrating normal mode noise removal by the choke coil shown in FIG. 2, wherein FIG. 5A is a magnetic circuit diagram and FIG. 5B is an electric circuit diagram.
FIG. 6 is a front view of a magnetic core for describing a modification of the choke coil shown in FIG. 1;
FIG. 7 is a perspective view showing another embodiment.
FIG. 8 is a graph showing frequency characteristics of a choke coil.
FIG. 9 is a schematic configuration diagram showing a conventional choke coil.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Choke coil 2 ... Bobbin 3 ... Magnetic core (1st magnetic core)
4: Magnetic core (second magnetic core)
5, 6 ... winding 13 ... I-shaped magnetic core piece 14 ... E-shaped magnetic core piece 14a ... middle legs 14b, 14c ... outer legs 14d ... joint 21 ... cylinders 22 to 26 ... flange 27, 28, 29 ... holes

Claims (3)

A tubular portion having an extending portion at each end thereof, and a bobbin made of a non-magnetic insulating material constituted by flange portions provided at both ends and a central portion of the tubular portion,
A pair of windings wound around the outer periphery of the cylindrical portion including the outer periphery of the extending portion ,
A first magnetic core having a closed magnetic path formed of a high magnetic permeability material having one side inserted through a hole of the cylindrical portion;
One magnetic core piece inserted into a hole provided substantially parallel to the cylindrical portion hole in each of the extending portions, and another magnetic material forming a closed magnetic path in combination with the one magnetic material core piece A second magnetic core made of a low magnetic permeability material composed of a body core piece;
A choke coil comprising: The choke coil according to claim 1, wherein the width of the middle leg of the second magnetic core is approximately twice the width of the outer leg and the joint of the second magnetic core. The distance between the first magnetic core and the second magnetic core is A, and the length of the magnetic path from the tip of the outer leg of the second magnetic core to the tip of the middle leg through the joint is B. And the relative magnetic permeability of the second magnetic core is μ,
A ≧ B / 2μ
The choke coil according to claim 1, wherein the following is satisfied.

Images