JP2013191660A - Common mode noise filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a common mode noise filter capable of eliminating both common mode noise, and differential mode noise in a specific frequency band.SOLUTION: The common mode noise filter of this invention includes a common mode filter part 18 comprising a first coil 15 and a second coil 16, the second coil 16 is formed over the first coil 15 so as to be magnetically coupled with the first coil 15 mutually, an open coil 17 is located over the second coil 16 to be magnetically coupled with the common mode filter part 18, one end part 17a of the open coil 17 and the first coil 15 are connected, and the other end part 17b is opened.

Description

  The present invention relates to a common mode noise filter used between differential signal lines of various electronic devices such as digital devices, AV devices, and information communication terminals.

  A conventional common mode noise filter of this type has a first coil 2 and a second coil 3 formed in a plurality of laminated insulator layers 1a to 1f as shown in FIG. The first coil 2 and the second coil 3 are connected to the lead conductors 4 and 5, respectively. The insulator layer 1a provided on the lowermost surface and the insulator layer 1f provided on the uppermost surface are made of a magnetic material. The other insulator layers 1b to 1e are made of a nonmagnetic material. Then, the first coil 2 and the second coil 3 are magnetically coupled to remove common mode noise.

  As prior art document information relating to the invention of this application, for example, Patent Document 1 is known.

JP-A-8-203737

  The above-described conventional common mode noise filter has a problem that the unnecessary differential mode noise can hardly be removed because the loss is small with respect to the differential mode (normal mode) component.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a common mode noise filter that can remove not only common mode noise but also differential mode noise in a specific frequency band.

  In order to achieve the above object, the present invention has the following configuration.

  The invention according to claim 1 of the present invention includes two magnetic body portions, a non-magnetic body portion formed between the two magnetic body portions, a first coil formed on the non-magnetic body portion, A second coil, an open coil whose one end is connected to the first coil and the other end is opened, and a common mode filter unit composed of the first coil and the second coil. And the second coil is formed above the first coil so as to be magnetically coupled to the first coil, and the open coil is positioned above the second coil. In this configuration, LC resonance occurs due to the stray capacitance between the second coil and the open coil and the inductance component of the open coil. Noise can be removed, also by the common mode filter unit, and has a effect that can eliminate many of the common mode noise.

  The invention according to claim 2 of the present invention, in particular, comprises a plurality of coiled conductors formed in the vertical direction in the open coil in the non-magnetic part, and at least one winding direction of the plurality of coiled conductors. In the direction opposite to the winding direction of the other coil-shaped conductors, the first and second coils, and is generated between the second coil and the open coil according to this configuration. Without reducing the stray capacitance, the inductance components of the coiled conductors with different winding directions cancel each other to some extent, so that the inductance value of the entire open coil is lowered, thereby the number of coiled conductors with different winding directions. Because the inductance value of the entire open coil can be easily adjusted by the number of turns, etc., the frequency of the attenuation pole of differential mode noise can be controlled. It is those having an iodine effect.

  In the invention according to claim 3 of the present invention, in particular, a coiled conductor having the other end opened among the plurality of coiled conductors constituting the open coil is laminated and disposed so as to be adjacent to the second coil. In this configuration, since the stray capacitance can be configured on the open end side with the second coil, the inductance value of the open coil that directly contributes to the LC resonance can be increased. This has the effect of reducing the frequency of the attenuation pole of the mode noise.

  According to a fourth aspect of the present invention, in particular, the first open coil disposed above the second coil, having one end connected to the first coil and having the other end open, and the first coil 2 is provided with a second open coil that is connected to one end of the coil and connected to the second coil and is open at the other end. According to this configuration, two different resonance circuits are provided. The first open coil, the inductance component of the second open coil, the stray capacitance between the first open coil and the second coil, and between the second open coil and the first coil By adjusting the stray capacitance of the differential mode noise, attenuation poles can be created in two different frequency bands for the differential mode noise, thereby eliminating the differential mode noise in a wide frequency band. And it has a effect that that.

  In the invention according to claim 5 of the present invention, in particular, wide portions are respectively formed in a part of the first coil or the second coil and a part of the open coil, and the wide parts are opposed to each other in a top view. According to this configuration, since the stray capacitance between the first and second coils and the open coil can be increased, the differential mode noise can be reduced by adjusting the size of the wide portion. This has the effect of being able to control the frequency of the attenuation pole.

  According to a sixth aspect of the present invention, in particular, a third coil and a fourth coil that are magnetically coupled to each other are provided between the upper magnetic body portion and the open coil, and the third coil and the fourth coil are provided. The other common mode filter unit composed of the coil is connected to the first coil and the third coil, and the second coil and the fourth coil are connected. Since the coil can be formed between the common mode filter section and another common mode filter section, the common mode filter section, the other common mode filter section, and the magnetic body section can be brought close to each other, and two common mode filters Because the parts can be magnetically coupled together, the impedance of the common mode component can be increased, which can eliminate a lot of common mode noise. Cormorant is as it has the effect effect.

  In the invention according to claim 7 of the present invention, in particular, the second coil and the fourth coil are adjacent to the open coil. According to this configuration, the gap between the open coil and the second coil is determined. Since stray capacitance is generated between the open coil and the fourth coil, the stray capacitance between the coil and the open coil can be increased, thereby lowering the frequency of the attenuation pole of the differential mode noise. It has the effect that it can be performed.

  As described above, in the common mode noise filter of the present invention, the second coil is formed above the first coil so as to be magnetically coupled to the first coil, and one end of the first coil is connected. In addition, since the open coil whose other end is opened is positioned above the second coil and magnetically coupled to the common mode filter unit, the stray capacitance between the second coil and the open coil LC resonance due to the inductance component of the open coil occurs between the differential lines, and this provides an excellent effect that differential mode noise can be removed.

1 is an exploded perspective view of a common mode noise filter according to Embodiment 1 of the present invention. Perspective view of the common mode noise filter Internal connection schematic diagram of the common mode noise filter Characteristic diagram showing the frequency dependence of the differential mode insertion loss of the common mode noise filter An exploded perspective view of another example of the common mode noise filter The disassembled perspective view of the common mode noise filter in Embodiment 2 of this invention An exploded perspective view of another example of the common mode noise filter Internal connection schematic diagram of the common mode noise filter Internal connection schematic diagram of the common mode noise filter The disassembled perspective view of the common mode noise filter in Embodiment 3 of this invention Internal connection schematic diagram of the common mode noise filter The disassembled perspective view of the common mode noise filter in Embodiment 4 of this invention The disassembled perspective view of the common mode noise filter in Embodiment 5 of this invention Internal connection schematic diagram of the common mode noise filter An exploded perspective view of another example of the common mode noise filter Internal connection schematic diagram of the common mode noise filter Exploded perspective view of a conventional common mode noise filter

(Embodiment 1)
Hereinafter, the first and second aspects of the present invention will be described with reference to the first embodiment.

  FIG. 1 is an exploded perspective view of a common mode noise filter according to Embodiment 1 of the present invention, and FIG. 2 is a perspective view of the common mode noise filter.

  As shown in FIGS. 1 and 2, the common mode noise filter according to the first exemplary embodiment of the present invention includes a magnetic body portion 12 including first and second magnetic layers 11 a and 11 b, and a first magnetic layer. A non-magnetic body portion 14 composed of first to fifth insulator layers 13a to 13e located between the body layer 11a and the second magnetic body layer 11b, and a first magnetic layer formed on the non-magnetic body portion 14. A coil 15, a second coil 16, an open coil 17, and a common mode filter unit 18 including the first coil 15 and the second coil 16 are provided.

  In addition, the second coil 16 is formed above the first coil 15 so as to be magnetically coupled to the first coil 15, and the open coil 17 is positioned above the second coil 16. Thus, the common mode filter unit 18 is magnetically coupled, the one end 17a of the open coil 17 and the first coil 15 are connected, and the other end 17b is opened.

  In the above configuration, the first and second magnetic layers 11a and 11b are formed in a sheet shape and are formed of a magnetic material such as Ni—Cu—Zn ferrite. In addition, the first magnetic layer 11a and the second magnetic layer 11b are formed separately in the upper and lower portions and constitute the magnetic body portion 12, respectively.

  The first to fifth insulator layers 13a to 13e are, from below, the first insulator layer 13a, the second insulator layer 13b, the third insulator layer 13c, the fourth insulator layer 13d, 5 insulator layers 13e are stacked in this order, and are formed into a sheet shape from a nonmagnetic material such as Cu-Zn ferrite or glass ceramic. The first to fifth insulator layers 13a to 13e constitute a nonmagnetic material portion 14.

  Further, the first coil 15, the second coil 16, and the open coil 17 are each formed by plating or printing a conductive material such as silver in a spiral shape. The first coil 15 is on the top surface of the second insulator layer 13b, the second coil 16 is on the top surface of the third insulator layer 13c, and the open coil 17 is on the top surface of the fourth insulator layer 13d. Is formed. That is, the first coil 15, the second coil 16, and the open coil 17 are configured in this order from the bottom. Here, the first coil 15, the second coil 16, and the open coil 17 are arranged at substantially the same position in the top view, and the winding direction is also the same direction in the top view. Here, the same winding direction means that a common current flows in the same direction. The first coil 15 and the second coil 16 are magnetically coupled to constitute the common mode filter unit 18, and the open coil 17 and the common mode filter unit 18 are also magnetically coupled. The shapes of the first coil 15, the second coil 16, and the open coil 17 may be spiral instead of spiral.

  The first coil 15 is connected to the first lead conductor 20 formed in the first insulator layer 13a via the first via electrode 19a formed in the second insulator layer 13b. The second coil 16 is formed on the second insulator layer 13a via the second via electrodes 19b formed on the second and third insulator layers 13b and 13c. The lead-out conductor 21 is connected. The first lead conductor 20 and the second lead conductor 21 may be formed in different insulator layers.

  Further, the two second via electrodes 19b are respectively provided at the same position in a top view. In addition, the first via electrode 19a and the second via electrode 19b are formed by drilling a hole in a predetermined portion of the insulator layer with a laser and filling the hole with silver. The number of the first and second magnetic layers 11a and 11b and the first to fifth insulator layers 13a to 13e is not limited to the number shown in FIG.

  And the main-body part 22 of a common mode noise filter is formed by the above-mentioned structure. Further, first to fourth external electrodes 23 to 26 are provided on both side surfaces of the main body 22, and the first external electrode 23 is connected to one end 15 a of the first coil 15 and the open coil 17. Is connected to one end 17a. As a result, the first coil 15 and the one end 17 a of the open coil 17 are connected via the first external electrode 23. The other end 17b of the open coil 17 is open without being connected to the external electrode. Further, the second to fourth external electrodes 24 to 26 are respectively connected to one end 16 a of the second coil 16, one end 20 a of the first lead conductor 20, and one end 21 a of the second lead conductor 21. Connected. Further, the first to fourth external electrodes 23 to 26 are formed by printing silver on the side surface of the main body 22, and a nickel plating layer is formed on these surfaces by plating. A low melting point metal plating layer such as tin or solder is formed on the surface of the substrate by plating.

  FIG. 3 is a connection schematic diagram of the common mode noise filter according to the first embodiment of the present invention.

  As apparent from FIG. 3, the common mode noise entering from the first external electrode 23 and the second external electrode 24 can be removed by the first coil 15 and the second coil 16, and the second A stray capacitance (C component) is generated between the coil 16 and the open coil 17, and an LC resonance circuit is configured by the stray capacitance and the inductance component (L component) of the open coil 17.

  That is, the second coil is formed between a differential line formed by a line passing through the first external electrode 23 and the third external electrode 25 and a line passing through the second external electrode 24 and the fourth external electrode 26. The stray capacitance (C component) and the inductance component (L component) of the open coil 17 are generated between the open coil 17 and the open coil 17, and LC resonance is generated by the LC component between the differential lines in the differential mode. Differential mode noise is attenuated.

  As described above, in the common mode noise filter according to the first exemplary embodiment of the present invention, the second coil 16 is formed above the first coil 15 so as to be magnetically coupled to the first coil 15, and is thus an open coil. 17 is located above the second coil 16 and is magnetically coupled to the common mode filter unit 18, one end 17 a of the open coil 17 is connected to the first coil 15, and the other end 17 b is opened. Therefore, in the differential mode, as described above, LC resonance occurs due to the stray capacitance between the second coil 16 and the open coil 17 and the inductance component of the open coil 17, thereby causing differential mode noise. The effect that can be removed is obtained. Further, since the open coil 17 can be magnetically coupled to the common mode filter unit 18 to obtain a high inductor value with a small number of turns, a desired inductor value can be easily obtained even with a small number of coil turns. Furthermore, the size can be reduced.

  Then, by adjusting the LC resonance frequency, it is possible to selectively reduce differential mode noise in a specific frequency band, for example, a communication frequency band of a mobile phone in the 800 to 900 MHz band or a 2 GHz band, a GPS frequency band, or the like. .

  FIG. 4 is a characteristic diagram showing the frequency dependence of the differential mode insertion loss of the common mode noise filter according to the first embodiment of the present invention and the conventional common mode noise filter.

  As apparent from FIG. 4, in the present invention, differential mode noise at 800 to 900 MHz is selectively adjusted by adjusting the stray capacitance between the second coil 16 and the open coil 17 and the inductance component of the open coil 17. Can be reduced.

  Furthermore, since the number of open coils 17 is one, the number of stacked layers can be reduced.

  In the first embodiment of the present invention described above, the open coil 17 is wound in the same direction as the first coil 15 and the second coil 16 in the top view. As shown, the winding direction of the open coil 17 may be reversed from that of the first coil 15 and the second coil 16.

  Moreover, although the open coil 17 was comprised by 1 layer, you may comprise by multiple layers.

(Embodiment 2)
The second and third embodiments of the present invention will be described below with reference to the second embodiment.

  FIG. 6 is an exploded perspective view of the common mode noise filter according to Embodiment 2 of the present invention. In the second embodiment of the present invention, components having the same configurations as those of the first embodiment of the present invention are denoted by the same reference numerals, and the description thereof is omitted.

  The second embodiment of the present invention is different from the first embodiment of the present invention described above in that the open coil 17 is composed of two coiled conductors 27a and 27b as shown in FIG.

  In the first embodiment, the inductor value can be reduced by reducing the number of turns of the open coil 17, but at the same time, the stray capacitance between the second coil 16 and the open coil 17 is reduced. It is difficult to adjust the LC resonance frequency.

  On the other hand, in the second embodiment, the two coiled conductors 27a and 27b are formed in the vertical direction, and the coiled conductor 27a formed below the coiled conductors 27a and 27b is the first coil 15. The winding direction is the same as that of the second coil 16 when viewed from above, and the upper coiled conductor 27b is configured such that the winding direction thereof is opposite to that when viewed from above. The one end 17a of the open coil 17 connected to the first coil 15 is configured as a coiled conductor 27a formed below, and the other end 17b of the open coil 17 is configured as a coiled conductor 27b formed above. Is done. The two coiled conductors 27a and 27b are connected by a third via electrode 19c. Further, the coiled conductor 27b formed above is formed on the sixth insulator layer 13f.

  With this configuration, in a state where stray capacitance is generated between the second coil 16 and the coiled conductor 27a of the open coil 17, the inductance components are offset to some extent between the coiled conductors 27a and 27b in different winding directions. Therefore, the inductance value of the entire open coil 17 is lowered, so that the inductance value of the entire open coil 17 can be easily adjusted by the number of coiled conductors 27a and 27b in different winding directions, the number of windings, etc. Since the necessary stray capacitance can be secured without decreasing, the frequency of the attenuation pole of the differential mode noise can be easily controlled.

  Further, as shown in FIG. 7, the coiled conductor 27 a having the other end 17 b opened among the plurality of coiled conductors 27 a and 27 b constituting the open coil 17 is laminated so as to be adjacent to the second coil 16. You may arrange. With this configuration, since the stray capacitance can be configured on the open end side with the second coil 16, the inductance value of the open coil 17 that directly contributes to LC resonance can be increased. The frequency of the attenuation pole can be adjusted low.

  Here, FIG. 8 shows a schematic diagram of internal connections in the common mode filter of FIG. 6, and FIG. 9 shows a schematic diagram of internal connections in the common mode filter of FIG.

  The common mode noise filter shown in FIGS. 6 and 7 can control the frequency of the attenuation pole of the differential mode noise or can reduce the frequency of the attenuation pole of the differential mode noise. For example, differential mode noise in a mobile phone communication frequency band of 800 to 900 MHz band can be reduced.

(Embodiment 3)
The third embodiment of the present invention will be described below in particular.

  FIG. 10 is an exploded perspective view of the common mode noise filter according to Embodiment 3 of the present invention. In the third embodiment of the present invention, components having the same configurations as those of the first embodiment of the present invention are denoted by the same reference numerals, and the description thereof is omitted.

  The third embodiment of the present invention is different from the first embodiment of the present invention described above in that it is disposed above the second coil 16 as shown in FIG. The first open coil 27b that is connected and opened at the other end 17b is located below the first coil 15 and is connected to one end of the first coil 15 and the second coil 16, and the other end 17b is opened. It is a point provided with two open coils 27a.

  According to this configuration, since two different resonance circuits can be formed, the inductance component of the first open coil, the second open coil, the stray capacitance between the first open coil and the second coil, the second By adjusting the stray capacitance between the open coil of the first coil and the first coil, attenuation poles can be created in two different frequency bands for differential mode noise. Can be removed.

  With this configuration, two different resonance circuits can be formed as shown in FIG. 11, so that the first open coil 27 b above the second coil 16 and the second open below the first coil 15. Of the open coil 27a, stray capacitance between the first open coil 27b above the second coil and the second coil 16, and the second open coil 27a below the first coil and the first coil. The stray capacitance between the coil 15 and the coil 15 can be adjusted. As a result, an attenuation pole can be created in two different frequency bands for the differential mode noise, so that the differential mode noise can be removed in a wide frequency band. . In addition, there are a plurality of mobile phone communication frequency bands depending on the country. Typically, there are 800 to 900 MHz and 2 GHz bands. By setting the resonance frequency according to these two frequency bands, the differential mode in both frequency bands. Noise can be removed. Furthermore, since it is symmetrical with respect to the vertical direction, the directionality is lost.

  In Embodiments 2 and 3 of the present invention described above, the number of coiled conductors (first and second open coils) 27a and 27b constituting the open coil 17 is one, but a plurality may be used.

(Embodiment 4)
Hereinafter, the invention according to the fifth aspect of the present invention will be described with reference to the fourth embodiment.

  FIG. 12 is an exploded perspective view of the common mode noise filter according to Embodiment 4 of the present invention. In the fourth embodiment of the present invention, components having the same configurations as those of the first embodiment of the present invention are denoted by the same reference numerals, and the description thereof is omitted.

  The fourth embodiment of the present invention is different from the first embodiment of the present invention described above in that a wide portion 28 is formed in a part of each of the second coil 16 and the open coil 17 as shown in FIG. The wide portions 28 are opposed to each other in a top view.

  With this configuration, the stray capacitance between the second coil 16 and the open coil 17 can be increased. Therefore, by adjusting the size of the wide portion 28, the frequency of the attenuation pole of the differential mode noise can be controlled. . In FIG. 12, the wide portion 28 is formed in the vicinity of the second via electrode 19b, but may be another portion.

  In the first to fourth embodiments of the present invention described above, the open coil 17 and the first and second coils 15 and 16 are connected via the external electrodes 23 and 24, but via the via electrodes. You may connect.

(Embodiment 5)
Hereinafter, the present invention, particularly, the inventions described in claims 6 and 7 will be described using the fifth embodiment.

  FIG. 13 is an exploded perspective view of the common mode noise filter according to the fifth embodiment of the present invention. In the fifth embodiment of the present invention, components having the same configurations as those of the first embodiment of the present invention described above are denoted by the same reference numerals, and description thereof is omitted.

  The fifth embodiment of the present invention differs from the first embodiment of the present invention described above in that a third coil 29 and a fourth coil that are magnetically coupled to each other above the open coil 17 are shown in FIG. 30, the other common mode filter unit 31 including the third coil 29 and the fourth coil 30 is provided, and the first coil 15 and the third coil 29 are connected and the second coil 16 and the fourth coil 30 are connected. The coil 30 is connected through via electrodes 19a and 19b.

  At this time, the first and second lead conductors 20 and 21 are not formed, and the third coil 29 and the fourth coil 30 are provided below the upper magnetic body portion 12. The third and fourth external electrodes 25 and 26 are connected to one end 29 a of the third coil 29 and one end 30 a of the fourth coil 30, respectively. Furthermore, it is necessary to form the sixth insulator layer 13f due to the increase in the number of coils.

  By configuring in this way, the open coil 17 can be formed between the common mode filter unit 18 and the other common mode filter unit 31, so the common mode filter unit 18, the other common mode filter unit 31 and the magnetic body unit 12 can be brought close to each other. Furthermore, since the two common mode filter sections 18 and 31 can be connected in series in a magnetically coupled state, the impedance of the common mode component can be increased, thereby removing a lot of common mode noise.

  Also in this case, as shown in FIG. 14, since the LC resonance occurs due to the stray capacitance between the third coil 29 and the open coil 17 and the inductance component of the open coil 17, the differential mode noise can be removed. .

  As shown in FIGS. 15 and 16, the second coil 16 and the fourth coil 30 may be provided at a position closer to the open coil 17 than the first coil 15 and the third coil 29. With this configuration, stray capacitance is generated between the open coil 17 and the second coil 16 and between the open coil 17 and the fourth coil 30, so that the stray capacitance between the coil and the open coil 17 is increased. Accordingly, the frequency of the attenuation pole of the differential mode noise can be further reduced. Further, since it is symmetric with respect to the vertical direction, the directionality is lost.

  At this time, even if the first coil 15 and the third coil 29 connected to the open coil 17 are brought close to the open coil 17, they have the same potential, so that no stray capacitance is generated.

  In the first to fifth embodiments of the present invention described above, a magnetic material serving as a magnetic core may be formed at a predetermined location of the insulator layer. Further, the upper and lower sides may be reversed, and the upper side may be the mounting surface.

  The common mode noise filter according to the present invention has an effect that not only common mode noise but also differential mode noise in a specific frequency band can be removed, and in particular, digital equipment, AV equipment, information communication terminals, etc. This is useful in a common mode noise filter used as a noise countermeasure for various electronic devices.

11a, 11b First and second magnetic layers 12 Magnetic portions 13a-13e First to fifth insulator layers 14 Nonmagnetic portion 15 First coil 16 Second coil 17 Open coil 18 Common mode filter Part 27a Coiled conductor (second open coil)
27b Coiled conductor (first open coil)
28 Wide part 29 Third coil 30 Fourth coil 31 Other common mode filter part

Claims (7)

Two magnetic body parts, a non-magnetic body part formed between the two magnetic body parts, a first coil and a second coil formed on the non-magnetic body part, and one end thereof is the first part An open coil connected to the first coil and having the other end open, and a common mode filter unit including the first coil and the second coil, the second coil being the first coil A common mode noise filter formed above the first coil so as to be magnetically coupled to the coil, and the open coil being positioned above the second coil and magnetically coupled to the common mode filter unit . In the non-magnetic part, the open coil is composed of a plurality of coiled conductors formed in the vertical direction, and at least one winding direction of the plurality of coiled conductors is the other coiled conductor, the first and second coils. The common mode noise filter according to claim 1, wherein the common mode noise filter is opposite to the winding direction of the wire when viewed from above. The common mode noise filter according to claim 1, wherein among the plurality of coiled conductors constituting the open coil, a coiled conductor having the other end opened is laminated and disposed adjacent to the second coil. A first open coil disposed above the second coil, having one end connected to the first coil and having the other end open, and one end of the first coil and the first coil The common mode noise filter according to claim 1, further comprising a second open coil connected to the second coil and having the other end opened. The common mode noise filter according to claim 1, wherein wide portions are respectively formed in a part of the first coil or the second coil and a part of the open coil, and the wide parts are opposed to each other in a top view. A third coil and a fourth coil that are magnetically coupled to each other are provided between the upper magnetic body portion and the open coil, and another common mode filter portion including the third coil and the fourth coil is provided. The common mode noise filter according to claim 1, wherein the first coil and the third coil are connected, and the second coil and the fourth coil are connected. The common mode noise filter according to claim 6, wherein the second coil and the fourth coil are adjacent to the open coil.

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