JP2015111720A - Common mode filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a common mode filter of winding type capable of reducing the common mode noise.SOLUTION: A common mode filter includes first and second wires W1, W2 wound around a winding core 11a. The wires W1, W2 are wound from one end toward the other end of the winding core 11a in the longitudinal direction, up to the N-th turn. The i-th turn of the wire W1 (i is 2 to N-2) is located closer to one end side of the winding core than the i-th turn of the wire W2, the i-th turn of the wire W2 is located closer to one end side than the i-th turn of the wire W1, and the i-th turn of the wire W1 is located closer to one end side than the i-th turn of the wire W2. The j-th turn of the wire W1 (j is i+1 to N-1) is located closer to the other end side than the j-th turn of the wire W2, the (j+1)-th turn of the wire W2 is located closer to the other end side than the j-th turn of the wire W1, and the (j+1)-th turn of the wire W1 is located closer to the other end side than the (j+1)-th turn of the wire W2.

Description

  The present invention relates to a common mode filter, and more particularly to a winding structure of a common mode filter.

  A common mode filter is known which includes two inductances that are provided on each of two signal lines constituting a transmission line of a differential transmission system and are magnetically coupled to each other. By inserting the common mode filter into the transmission line of the differential transmission system, it is possible to selectively remove only the common mode noise current.

  As a specific structure of the common mode filter, one using a toroidal core and one using a drum core are known. When using a toroidal core, since there is no gap inside the core and it has a high effective magnetic permeability, high noise removal performance can be obtained, but automatic winding is difficult and you have to rely on manual winding. Variation in characteristics increases. On the other hand, when a drum core is used, it is difficult to obtain a noise removal performance as high as that of a toroidal core. On the other hand, since an automatic winding method can be used, variation in characteristics can be reduced. Moreover, since the automatic winding method can be used, the drum core type common mode filter is suitable for mass production.

  Patent Documents 1 and 2 disclose examples of common mode filters configured using a drum core. In the example of Patent Document 1, two wires each constituting an inductance are wound in a two-layer structure. On the other hand, in the example of Patent Document 2, two wires each forming an inductance are wound simultaneously as a pair of wires. In general, the former winding method is called layer winding, and the latter winding method is called bifilar winding. Further, Patent Document 3 discloses an example of an automatic winding machine used for winding a wire around a drum core.

Japanese Patent No. 4789076 Japanese Patent No. 3973028 Japanese Patent No. 4737268

  By the way, in recent years, the adoption of Ethernet in in-vehicle LAN has been advanced. A common mode filter used in an in-vehicle Ethernet is required to have more stable characteristics and higher noise reduction performance than before. In this regard, the drum core type common mode filter has a feature in that variation in characteristics can be reduced as described above. Therefore, if the noise reduction performance of the drum core type common mode filter can be improved, an optimum common mode filter for an in-vehicle Ethernet can be obtained.

  What is specifically required as high noise reduction performance is a reduction in mode conversion characteristics (Scd) indicating the ratio of differential signal components input to the common mode filter that are converted into common mode noise and output. Therefore, as a result of the research conducted by the inventor of the present invention to solve this problem, a capacitance generated between different turns (hereinafter referred to as “different-turn capacitance”) is used to reduce the mode conversion characteristics of the common mode filter. It turned out that the balance of was greatly involved. Further, a high inductance value is also required, and for that purpose, it is a good idea to increase the number of turns of the coil.

  Accordingly, one of the objects of the present invention is to provide a drum core type common mode filter capable of realizing a high inductance while achieving a reduction in mode conversion characteristics by balancing the capacitance between different turns generated in each of a pair of coils. It is to provide.

  In order to solve the above-described problems, a common mode filter according to the present invention includes a core portion having one and other ends in the longitudinal direction, and first and second wires wound around the core portion. The first and second wires are wound from a first turn to an N-th turn from the one end of the core to the other end, and the first wire An i-turn (i is 2 or more and N-2 or less) is located closer to the one end of the core than the i-th turn of the second wire, and the i-th of the second wire The turn is located closer to the one end of the core than the i-th turn of the first wire, and the i-1 turn of the first wire is the first wire of the second wire. It is located on the one end side of the winding core part from the i-1th turn, and the jth t (J is not less than i + 1 and not more than N-1) is located on the other end side of the core portion than the j-th turn of the second wire, and the j + 1-th turn of the second wire is It is located on the other end side of the winding core part from the j-th turn of the first wire, and the j + 1-th turn of the first wire is more than the j + 1-th turn of the second wire. It is located in the said other edge part side of the said core part, It is characterized by the above-mentioned.

  According to the present invention, since the winding structure of the first and second wires is bilaterally symmetrical including the positional relationship of the wires, the capacity between different turns is made uniform with respect to both the first and second wires. It is possible to reduce the impedance imbalance between the first and second wires. Therefore, the mode conversion characteristic Scd can be reduced, and a high-quality common mode filter can be realized.

  In the present invention, it is preferable that a space is provided between the i-th turn and the j-th turn of the first wire. When a space is provided between the i-th turn and the j-th turn of the first wire, a symmetrical winding structure can be easily realized with reference to the boundary between the i-th turn and the j-th turn. The influence of the capacity between turns can be sufficiently reduced. Therefore, Scd can be sufficiently reduced, and a high-quality common mode filter can be realized.

  In the present invention, the i-1th turn, the ith turn, the jth turn, and the j + 1th turn of the first wire are wound on the first layer on the core portion, and the second wire The i-th turn and the j-th turn are wound on the first layer, and the i-1th turn and the j + 1th turn of the second wire are wound on the second layer on the first layer. It is preferable.

  In the present invention, the i-1th turn, the ith turn, the jth turn, and the j + 1th turn of the first wire are wound on the first layer on the core portion, and the second wire It is preferable that the i-1th turn, the ith turn, the jth turn, and the j + 1th turn are wound around the first layer.

  In the present invention, it is preferable that j = i + 1. According to this, a winding structure with perfect left-right symmetry can be realized.

  Moreover, in order to solve the said subject, the common mode filter by this invention contains the 1st winding area located in the one end side of a longitudinal direction, and the 2nd winding area located in the other end side of the said longitudinal direction. A core part, a first wire wound around the core part, including a plurality of first winding patterns and a plurality of second winding patterns, and wound around the core part, A second wire including a third winding pattern and a plurality of fourth winding patterns, and the first winding block comprising the plurality of first and third winding patterns includes the core A second winding block that is wound around the first winding area of the winding portion and includes the plurality of second and fourth winding patterns is wound around the second winding area of the winding core portion. The winding structure of the first winding block and the winding structure of the second winding block are Symmetric with respect to the boundary between the first and second winding areas, and the longitudinal positions of the first winding pattern and the third winding pattern in the first winding block are Different from each other, the positions of the second winding pattern and the fourth winding pattern in the second winding block in the longitudinal direction are different from each other.

  When the winding structure of the first and second wires is symmetric including the positional relationship of the wires, the inter-turn capacitance is uniformly generated for both the first and second wires. The impedance imbalance between the first and second wires can be suppressed. Therefore, the mode conversion characteristic Scd can be reduced, and a high-quality common mode filter can be realized.

  In the present invention, it is preferable that the winding core portion further includes a space area positioned between the first winding area and the second winding area. When a space area is provided between the first winding area and the second area, it is possible to easily realize a symmetrical winding structure with respect to the boundary between the two winding areas, and the capacity between different turns. Can be sufficiently reduced. Therefore, Scd can be sufficiently reduced, and a high-quality common mode filter can be realized.

  In the present invention, it is preferable that the first wire is wound around a first layer on the core portion, and the second wire is wound around a second layer on the first layer. According to this configuration, Scd can be reduced in a so-called layer winding structure, and a high-quality common mode filter can be realized.

  In the common mode filter according to the present invention, when the number of turns of the first to fourth winding patterns is n turns (n is a positive integer), the first winding area includes the first layer. The first winding pattern of n turns is wound and the third winding pattern of 1 turn is wound, and the third winding pattern of n-1 turns is wound on the second layer. In the second winding area, the second winding pattern of n turns is wound around the first layer, and the fourth winding pattern of one turn is wound around the first layer. It is preferable that the fourth winding pattern of n-1 turns is wound around the second layer. According to this configuration, it is possible to realize left-right symmetry in a realistic winding structure that takes into account the collapse of the second layer in advance. Therefore, Scd can be reduced and a high-quality common mode filter can be realized.

  In the present invention, the one turn of the third winding pattern wound around the first layer in the first winding area is wound around the first layer in the first winding area. Of the plurality of first winding patterns, the first winding pattern is provided adjacent to the turn closest to the one end in the longitudinal direction, and is wound on the first layer of the second winding area. The one turn of the four winding patterns is the turn closest to the other end in the longitudinal direction among the plurality of second winding patterns wound around the first layer in the second winding area. It is preferable that it is provided adjacent to. According to this structure, the drop part from the 2nd layer of the 2nd wire to the 1st layer can be provided in the both ends of the longitudinal direction of the core part 11a. Therefore, Scd can be reduced and a high-quality common mode filter can be realized.

  In the present invention, the one turn of the third winding pattern wound around the first layer in the first winding area is wound around the first layer in the first winding area. The plurality of first winding patterns are provided adjacent to the turn closest to the other end in the longitudinal direction, and are wound on the first layer of the second winding area. The one turn of the fourth winding pattern is the turn closest to the one end in the longitudinal direction among the plurality of second winding patterns wound around the first layer of the second winding area. It is preferable that it is provided adjacent to. According to this structure, the drop part from the 2nd layer of a 2nd wire to the 1st layer can be provided in the center part of the longitudinal direction of the core part 11a. Therefore, Scd can be reduced and a high-quality common mode filter can be realized.

  In this invention, it is preferable that the 1st and 2nd wire is wound by turns in the said longitudinal direction on the said core part. According to this configuration, Scd can be reduced in a so-called bifilar winding structure, and a high-quality common mode filter can be realized.

  In the present invention, the winding core portion further includes a third winding area different from the first and second winding areas, and the first wire is wound around the third winding area. Preferably, the second wire further includes a sixth winding pattern wound around the third winding area. In this case, the number of turns of the fifth winding pattern is less than half of the number of turns of the first winding pattern, and the number of turns of the sixth winding pattern is the third winding. It is preferable that it is less than half of the number of turns of the pattern. Alternatively, the number of turns of the fifth and sixth winding patterns is preferably 2 turns or less, respectively.

  ADVANTAGE OF THE INVENTION According to this invention, the common mode filter which can obtain a high inductance can be provided, implement | achieving reduction of a mode conversion characteristic.

FIG. 1 is a schematic perspective view showing an external structure of a surface mount type common mode filter 1 according to a first embodiment of the present invention. FIG. 2 is a basic electric circuit diagram of the common mode filter 1. FIG. 3 is a more detailed equivalent circuit diagram of the common mode filter 1 shown in FIG. FIG. 4 is a schematic diagram for explaining the distributed capacity between a pair of wires. FIG. 5 is an equivalent circuit diagram showing a generation model of the distributed capacitance of the common mode filter. FIG. 6 is a schematic plan view showing a detailed configuration of the common mode filter 1. FIG. 7 is a schematic cross-sectional view of the common mode filter 1 shown in FIG. 6, (a) is a cross-sectional view along the line A ₁ -A ₁ ′, and (b) is along the line A ₂ -A ₂ ′. It is sectional drawing. FIG. 8 is a schematic cross-sectional view showing the configuration of the common mode filter 2 according to the second embodiment of the present invention. FIG. 9 is a schematic cross-sectional view showing the configuration of the common mode filter 3 according to the third embodiment of the present invention. FIG. 10 is a schematic plan view showing the configuration of the common mode filter 4 according to the fourth embodiment of the present invention. 11 is a schematic cross-sectional view of the common mode filter 4 shown in FIG. 10, (a) is a cross-sectional view taken along the line A ₁ -A ₁ ′, and (b) is taken along the line A ₂ -A ₂ ′. It is sectional drawing. FIG. 12 is a schematic plan view showing the configuration of the common mode filter 5 according to the fifth embodiment of the present invention. FIG. 13 is a schematic cross-sectional view of the common mode filter 5 shown in FIG. 12, (a) is a cross-sectional view along the line A ₁ -A ₁ ′, and (b) is along the line A ₂ -A ₂ ′. It is sectional drawing.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic perspective view showing an external structure of a surface mount type common mode filter 1 according to a first embodiment of the present invention. In the present embodiment, as shown in FIG. 1, the opposing direction of a pair of flanges 11b and 11c to be described later is the y direction, and the direction perpendicular to the y direction is within the plane of the upper surfaces 11bs and 11cs to be described later. A direction perpendicular to both the x direction and the y direction is referred to as a z direction.

  As shown in FIG. 1, the common mode filter 1 includes a drum core 11, a plate-like core 12 attached to the drum core 11, and wires W <b> 1 and W <b> 2 (first and second wires) wound around the drum core 11. It is configured with. The drum core 11 includes a rod-shaped core portion 11a having a rectangular cross section, and flanges 11b and 11c provided at both ends of the core portion 11a, and has a structure in which these are integrated. The plate-like core 12 is fixed to the lower surfaces of the flange portions 11b and 11c (surfaces opposite to the upper surfaces 11bs and 11cs). The common mode filter 1 is surface-mounted with the upper surfaces 11bs and 11cs of the flange portions 11b and 11c of the drum core 11 facing the circuit board.

  The drum core 11 and the plate-like core 12 are made of a magnetic material having a relatively high magnetic permeability, for example, a sintered body of Ni—Zn ferrite or Mn—Zn ferrite. Note that a magnetic material having a high magnetic permeability such as Mn—Zn-based ferrite usually has a low specific resistance and conductivity.

  Two terminal electrodes E1 and E2 are formed on the upper surface 11bs of the flange portion 11b, and two terminal electrodes E3 and E4 are formed on the upper surface 11cs of the flange portion 11c. The terminal electrodes E1, E2 are arranged in this order from one end side in the x direction. Similarly, the terminal electrodes E3 and E4 are also arranged in this order from one end side in the x direction. The end portions of the wires W1 and W2 are connected to the terminal electrodes E1 to E4 by thermocompression bonding.

  The wires W1 and W2 are coated conductors, and are wound around the winding core portion 11a in the same winding direction to constitute a coil conductor. The number of turns of the wires W1, W2 is also the same. In the present embodiment, the wires W1 and W2 are wound by layer winding of a two-layer structure. Moreover, a space is provided between adjacent turns located in the middle of the core part 11a, and thereby a space area S1 is configured. This point will be described in detail again later. The portions other than the space area S1 are wound with adjacent turns in close contact with each other. One end (end on the flange 11b side) W1a and the other end (end on the flange 11c side) W1b of the wire W1 are connected to the terminal electrodes E1 and E3, respectively. Further, one end (end on the flange 11b side) W2a and the other end (end on the flange 11c side) W2b of the wire W2 are connected to the terminal electrodes E2 and E4, respectively.

  FIG. 2 is a basic electric circuit diagram of the common mode filter 1.

  As shown in FIG. 2, the common mode filter 1 has a configuration in which an inductor 10a connected between the terminal electrodes E1 and E3 and an inductor 10b connected between the terminal electrodes E2 and E4 are magnetically coupled to each other. Have. Inductors 10a and 10b are configured by wires W1 and W2, respectively. With this configuration, when the terminal electrodes E1 and E2 are input terminals and the terminal electrodes E3 and E4 are output terminals, the differential signal input from the input terminal is hardly affected by the common mode filter 1 and is output from the output terminal. Is done. On the other hand, the common mode noise input from the input end is greatly attenuated by the common mode filter 1 and is hardly output to the output end.

  Here, the common mode filter generally has a property that a part of the differential signal input to the input end of the common mode filter is converted into common mode noise and output from the output end. Of course, this property is not desirable. Therefore, it is necessary to suppress the ratio of the differential signal converted to common mode noise (the above-described mode conversion characteristic Scd) to a certain value or less. Apart from this, the common mode filter is required to have as many turns as possible. This is to obtain the required inductance with a small size. In the common mode filter 1 according to the present embodiment, the above problem is solved by reducing the influence of the capacitance between different turns by making the winding structure including the positional relationship of the wires W1 and W2 symmetrical. This will be described in detail below.

  FIG. 3 is a more detailed equivalent circuit diagram of the common mode filter 1 shown in FIG.

  As shown in FIG. 3A, the common mode filter 1 has a resistance R0 and a capacitance C0 in parallel with the inductance L in addition to the original inductance L. Furthermore, it has a distributed capacitance C1 generated across a pair of inductances L, L by the wires W1, W2. FIG. 3B is a diagram in which the common mode filter 1 of FIG. 3A is divided into two blocks for convenience of explanation, and the divided inductances are L / 2, respectively. Further, the parallel resistance is R0 / 2, and the parallel capacitance is 2C0.

  FIG. 4 is a schematic diagram for explaining the distributed capacity between a pair of wires.

  As shown in FIG. 4A, for example, a distributed capacity C1 is generated between the same turns of a pair of wires wound by bifilar, and when the distance d between adjacent turns is wide, the distributed capacity between them is large. Does not occur. On the other hand, as shown in FIG. 4B, when the distance d between adjacent turns is small, a distributed capacity (capacity between different turns) C2 distributed between adjacent turns is generated. That is, both distributed capacitances C1 and C2 are generated between the pair of wires.

  FIG. 5 is an equivalent circuit diagram showing a generation model of the distributed capacitance of the common mode filter.

  As shown in FIG. 5 (a), when a pair of coils (inductance L) is divided into two at an intermediate position in a common mode filter composed of a pair of wires W1 and W2 wound with ordinary bifilar winding, Is a series connection of two inductances L / 2. A pair of coils generates a distributed capacitance C1 between the same turns and a distributed capacitance C2 between adjacent turns (see FIG. 4). Here, the distributed capacity C2 can be divided into a distributed capacity C21 of one block and a distributed capacity C22 of the other block in accordance with the division of the coil, and these distributed capacity C21 and C22 are both coils on the wire W2 side. As a result, only the resonance point of the LC circuit by the wire W2 changes, and as a result, the Scd also increases.

  On the other hand, as shown in FIG. 5B, the winding order of the pair of wires W1 and W2 on which the bifilar winding is performed is reversed at the intermediate position, and the winding structure including the positional relationship of the wires is made symmetrical. In this case, the distributed capacitance C21 of one block is generated in parallel with the coil on the wire W1 side, and the distributed capacitance C22 of the other block is generated in parallel with the coil on the wire W2 side. As a result, both the resonance point of the LC circuit by the wire W1 and the resonance point of the LC circuit by the wire W2 change, but the balance of the two resonance points does not change. Therefore, Scd can be reduced. Further, since the distance d between adjacent turns can be reduced, the number of turns can be increased to increase the inductance. This is because Scd can be reduced as described above even if the distance d between adjacent turns is narrowed to generate a distributed capacitance C2 between adjacent turns.

  The above description is for the case where the two wires are bifilar wound, but the same applies to the case of layer winding. Next, the structure of the common mode filter 1 will be described in detail.

FIG. 6 is a schematic plan view showing a detailed configuration of the common mode filter 1. Further, FIG. 7 is a schematic cross-sectional view of the common mode filter 1 shown in FIG. 6, (a) is 'cross-sectional view along the line, (b) the _{A 2 -A 2' A 1 -A} 1 in line FIG.

  As shown in FIGS. 6 and 7, the common mode filter 1 includes a pair of wires W <b> 1 and W <b> 2 wound around the core portion 11 a of the drum core 11 by so-called layer winding. The first wire W1 is directly wound around the surface of the core portion 11a to form a first winding layer (first layer), and the second wire W2 is the first wire except for a part thereof. A second winding layer (second layer) wound on the outside of the first layer is configured. The first wire W1 and the second wire W2 have substantially the same number of turns (here, 12 turns).

  The winding structure by the pair of wires W1 and W2 includes the first winding block BK1 provided in the first winding area AR1 located on one end side in the longitudinal direction of the core portion 11a, and the core portion 11a. A second winding block BK2 provided in the second winding area AR2 located on the other end side in the longitudinal direction is configured. The first to sixth turns (a plurality of first winding patterns) of the first wire W1 and the first to sixth turns (a plurality of third winding patterns) of the second wire W2 are the first The winding block BK1 is configured, and the seventh to twelfth turns (a plurality of second winding patterns) of the first wire W1 and the seventh to twelfth turns (a plurality of fourth wires) of the second wire W2. ) Constitutes a second winding block BK2.

  The first wire W1 is wound in order from one end to the other end of the core portion 11a. In particular, in the first and second winding areas AR1 and AR2, the first wire W1 is tightly wound with no gap between the lines. On the other hand, in the space area S1 located between the first winding area AR1 and the second winding area AR2, there is a space between the first winding block BK1 and the second winding block BK1. Is provided. That is, the first to sixth turns of the wire W1 are densely wound, a space is provided between the sixth and seventh turns, and the seventh to twelfth turns are densely wound again.

  The second wire W2 is also wound in order from one end of the core portion 11a toward the other end, and is wound while being fitted into a valley formed between the lines of the first wire W1. That is, the second wire W2 is not arranged directly above the first wire W1 of the same turn, and the positions of the winding core portions 11a in the longitudinal direction do not coincide with each other. The first turn of the second wire W2 is located in the valley between the first turn and the second turn of the first wire W1, and is overlaid on the winding layer of the first wire W1 until the fifth turn. It is wound.

  The sixth turn of the second wire W2 falls into the space between the first winding block BK1 and the second winding block BK2 and is in contact with the surface of the core portion 11a. Part of the layer. The seventh turn is the same as the sixth turn. Ideally, the sixth turn and the seventh turn of the second wire W2 are ideally formed in the second layer, but a space is provided between the sixth turn and the seventh turn of the first wire W1. In this case, since one of the two turns of the first wire W1 supporting the second wire W2 is missing, the position of the second layer cannot be maintained. For this reason, as a realistic structure, the sixth and seventh turns are in a state of being collapsed from the beginning.

  The eighth to twelfth turns of the second wire W2 are wound while being fitted again into the valley formed between the lines of the first wire W1. The eighth turn of the second wire W2 is located in the valley between the seventh and eighth turns of the first wire W1, and is wound on the winding layer of the first wire W1 until the 12th turn. Turned.

  The above is the case of 12 turns, but this is generalized as follows. When the number of turns of the first and second wires W1 and W2 in the first and second winding areas AR1 and AR2 is n (n is a positive integer), the first winding area AR1 On the first layer, an n-turn first wire W1 (first winding pattern) and a one-turn second wire W2 (third winding pattern) are wound, respectively. An n-1 turn second wire (third winding pattern) is wound around the second layer of the area AR1. Similarly, the n-turn first wire W1 (second winding pattern) and the one-turn second wire W2 (fourth winding pattern) are provided in the first layer of the second winding area AR2. Are wound, and an n-1 turn second wire W2 (fourth winding pattern) is wound on the second layer of the second winding area AR2.

  As shown in the figure, the winding structure of the first winding block BK1 and the winding structure of the second winding block BK2 are symmetrical with respect to the boundary line B (laterally symmetric). In particular, the positional relationship between the wires W1 and W2 in the first winding block BK1 and the positional relationship between the wires W1 and W2 in the second winding block BK2 are symmetrical. However, the positional relationship between the first and second wires W1, W2 in the first winding block BK1 and the second winding block BK2 is not symmetrical.

  For example, the twelfth to seventh turns of the first wire W1 of the second winding block BK2 are symmetrical to the first to sixth turns of the first wire W1 of the first winding block BK1. And both are the first wires W1. Further, the twelfth to eighth turns of the second wire W2 of the second winding block BK2 are symmetrical to the first to fifth turns of the second wire W2 of the first winding block BK1. Both are the second wires W2. Further, the sixth turn of the first wire W1 of the first winding block BK1 is symmetrical with the sixth turn of the first wire W1 of the second winding block BK2. The wire W1. Note that the symmetry is inevitably broken at the winding start and winding end positions, but such a slight deviation in symmetry is acceptable.

  As described above, when the winding structure of the first and second wires W1 and W2 is symmetric including the positional relationship of the wires, the distributed capacitance generated between different turns (inter-turn capacitance). Occurs uniformly in both the wires W1 and W2, so that the impedance imbalance of the wires W1 and W2 can be suppressed. Therefore, Scd (noise due to the differential signal component being converted into the common mode) can be reduced, and a high-quality common mode filter can be realized.

  Furthermore, when a space is provided between the first block and the second block as in the present embodiment, a symmetrical winding structure can be easily realized, and the influence of the capacitance between different turns is sufficient. Can be reduced. Therefore, Scd can be sufficiently reduced, and a high-quality common mode filter can be realized.

  In the above embodiment, the case where the left-right symmetry is perfect has been described, but it is not always necessary to be completely symmetric, and an asymmetric part may be included in part.

  FIG. 8 is a schematic cross-sectional view showing the configuration of the common mode filter 2 according to the second embodiment of the present invention.

  As shown in FIG. 8, the common mode filter 2 is characterized in that the number of turns of the first and second wires W1 and W2 is 13 (odd turns), and the symmetry of the winding structure is that of the core 11a. It exists in the point which has collapsed in one edge part of a longitudinal direction. The first to twelfth turns are the same as in the first embodiment. In the present embodiment, the 13th turn is provided after the 12th turn, and the 13th turn (fifth winding pattern) of the wire W1 and the 13th turn (sixth winding) of the second wire W2. Line pattern) constitutes a third winding block BK3 provided in the third winding area AR3.

  When the second and third winding blocks BK2 and BK3 are viewed as one winding block BK4, there is no strict symmetry between the first winding block BK1 and the fourth winding block BK4. . If the first and second wires W1, W2 are 13 turns, they cannot be divided equally. However, in this embodiment, the left 6 turns and the right 7 turns are divided into 6 turns of the right 7 turns and the left 6 turns have a symmetrical relationship. Symmetry is ensured between the first to sixth turns in the first winding block BK1 and the seventh to twelfth turns of the second winding block BK2, and the third winding is an asymmetric part. Since the number of turns of the line block BK3 is relatively small, the same effect as that of the first embodiment can be obtained without being greatly affected by the asymmetric portion.

  When the winding structure of the first and second wires W1 and W2 further includes a third winding block that is asymmetric with respect to the first and second winding blocks, the first winding block BK3 includes the first winding block BK3. And the number of turns of the second wires W1, W2 (fifth and sixth winding patterns) are respectively the first and second wires W1, W2 in the first and second winding blocks BK1, BK2. The number of turns is preferably half or less. For example, as shown in the figure, when the number of turns of the wires W1 and W2 in the first and second winding blocks BK1 and BK2 is both 6, the number of turns of the wires W1 and W2 in the third winding block BK3 is Each is preferably 3 turns or less. If the number of turns in the asymmetric part exceeds half of the number of turns in the symmetric part, the effect cannot be ignored, and the noise reduction effect will be insufficient, but if it is less than half, both windings This is because the impedance imbalance is relatively small, and there is no practical problem.

  The number of turns of the first and second wires W1, W2 in the third winding block BK3 is less than 2 turns regardless of the number of turns of the wires in the first and second winding blocks BK1, BK2. It is particularly preferred. In most cases, it is considered that the number of turns of the asymmetric part can be kept within 2 turns unless it is intentionally made asymmetric. Within this range, the impedance imbalance has a very small influence and is asymmetric. This is because it is almost the same as when there is no part.

  FIG. 9 is a schematic cross-sectional view showing the configuration of the common mode filter 3 according to the third embodiment of the present invention.

  As shown in FIG. 9, the common mode filter 3 is characterized in that the number of turns of the first and second wires W1 and W2 is 13 (odd turns), and the symmetry of the winding structure is that of the winding core portion 11a. It is in the point which has collapsed in the central part of the longitudinal direction. The first to sixth turns of the first and second wires W1, W2 are the same as those in the first embodiment. Next to the sixth turn of the second wire W2, the seventh turn (fifth winding pattern) of the first wire W1 is wound, and next to the seventh turn of the first wire W1. A seventh turn (sixth winding pattern) of the second wire W2 is wound. The seventh turns of the first and second wires W1, W2 are both provided in the first layer, and constitute a third winding block BK3 provided in the third winding area AR3. Thereafter, the eighth to thirteenth turns of the first and second wires W1 and W2 are wound in the same manner as the seventh to twelfth turns in the first embodiment.

  The first winding block BK1 and the seventh turn of the first wire W1 of the third winding block BK3 constitute one winding block BK4, and the second winding block BK2 and the third winding block BK3. When the seventh turn of the second wire W2 is viewed as another winding block BK5, there is no strict symmetry between the fourth winding block BK4 and the fifth winding block BK5. . However, symmetry is ensured between the first to sixth turns in the first winding block BK1 and the seventh to twelfth turns of the second winding block BK2, and the third asymmetric portion. Since the number of turns of the winding block BK3 is relatively small, the same effect as that of the first embodiment can be obtained without being greatly affected by the asymmetric part, as in the second embodiment.

  In the present embodiment, no space is provided between the first winding block BK1 and the second winding block BK2. However, a space may be provided as in the first embodiment. is there. When a space is provided between the first winding block BK1 and the second winding block BK2, a symmetrical winding structure can be easily realized, and the influence of the capacitance between different turns can be sufficiently reduced. Can do. Therefore, Scd can be sufficiently reduced, and a high-quality common mode filter can be realized.

FIG. 10 is a schematic plan view showing the configuration of the common mode filter 4 according to the fourth embodiment of the present invention. Further, FIG. 11 is a schematic cross-sectional view of the common mode filter 4 shown in FIG. 10, (a) is 'cross-sectional view along the line, (b) the _{A 2 -A 2' A 1 -A} 1 in line FIG.

  As shown in FIGS. 10 and 11, the common mode filter 4 is characterized in that the drop portion of the second wire W2 from the second layer to the first layer is not at the center portion in the longitudinal direction of the core portion 11a but at both ends. It is in the point provided in the part.

  The first wire W1 is wound in order from one end to the other end of the core portion 11a. In particular, the first to twelfth turns of the first wire W1 are tightly wound with no gap between the lines, and no space is provided between the sixth turn and the seventh turn. That is, no space between the lines is provided between the first winding block BK1 and the second winding block BK2.

  The second wire W2 is also wound in order from one end of the core portion 11a toward the other end, and is wound while being fitted into a valley formed between the lines of the first wire W1. The first turn and the twelfth turn of the second wire W2 are dropped into the first layer and are in contact with the surface of the core portion 11a, and form a part of the first layer instead of the second layer.

  The second turn of the second wire W2 is located in the valley between the first turn and the second turn of the first wire W1, and is overlaid on the winding layer of the first wire W1 until the sixth turn. And tightly wound. The sixth turn is located in the valley between the fifth and sixth turns of the first wire.

  The seventh turn is arranged by skipping one next winding position (valley), located in the valley between the seventh turn and the eighth turn of the first wire W1, and the first turn until the eleventh turn. The wire W1 is wound while being fitted into a valley formed between the wires W1. The twelfth turn, which is the final turn, falls into the first layer and is in contact with the surface of the core portion 11a as in the first turn, and forms part of the first layer instead of the second layer.

  As shown in the figure, the winding structure of the first winding block BK1 and the winding structure of the second winding block BK2 are symmetrical with respect to the boundary line B (laterally symmetric). In particular, the positional relationship between the wires W1 and W2 in the first winding block BK1 and the positional relationship between the wires W1 and W2 in the second winding block BK2 are symmetrical. However, the positional relationship of the first and second wires W1 and W2 in the first winding block BK1 and the second winding block BK2 is not symmetrical.

  For example, a symmetric relationship with the first turn of the second wire W2 of the first winding block BK1 is the twelfth turn of the second wire W2 of the second winding block BK2. The wire W2. Further, the twelfth to seventh turns of the first wire W1 of the second winding block BK2 are symmetrical to the first to sixth turns of the first wire W1 of the first winding block BK1. And both are the first wires W1. Further, the first to seventh turns of the second wire W2 of the second winding block BK2 are symmetrical to the second to sixth turns of the second wire W2 of the first winding block BK1. Both are the second wires W2. Note that the symmetry is inevitably broken at the winding start and winding end positions, but such a slight deviation in symmetry is acceptable.

  As described above, when the winding structure of the first and second wires W1 and W2 is symmetric including the positional relationship of the wires, the inter-turn capacitance is uniformly generated in both the wires W1 and W2. Therefore, the impedance imbalance of the wires W1 and W2 can be suppressed. Therefore, as in the first embodiment, Scd can be reduced, and a high-quality common mode filter can be realized.

FIG. 12 is a schematic plan view showing the configuration of the common mode filter 5 according to the fifth embodiment of the present invention. 13 is a schematic cross-sectional view of the common mode filter 5 shown in FIG. 12, where (a) is a cross-sectional view taken along the line A ₁ -A ₁ ′, and (b) is a line taken along the line A ₂ -A ₂ ′. FIG.

  As shown in FIGS. 12 and 13, the common mode filter 5 is characterized in that a pair of windings are wound by so-called bifilar winding. Bifilar winding is a winding method in which the first and second wires W1, W2 are alternately arranged one by one, and is preferably used when primary and secondary close coupling is required. The first wire W1 and the second wire W2 are wound in the longitudinal direction of the winding core portion 11a while being in parallel with each other to form a first winding layer. The first wire W1 and the second wire W2 have substantially the same number of turns (here, 6 turns).

  The winding structure by the pair of wires W1 and W2 is provided on the first winding block BK1 provided on one end side in the longitudinal direction of the core portion 11a and on the other end side in the longitudinal direction of the core portion 11a. A second winding block BK2 is provided. The first to third turns of the first and second wires W1 and W2 constitute a first winding block BK1, and the fourth to sixth turns of the first and second wires W1 and W2 are the first turns. 2 winding blocks BK2 are formed.

  In the first block (first to third turns), the first wire W1 is located on the left side and the second wire W2 is located on the right side, and in this order, the wire is tightly wound with no gap between the lines. In the second block (fourth to sixth turns), the positional relationship is reversed, the second wire W2 is located on the left side, and the first wire W1 is located on the right side. Has been.

  As shown in the figure, the winding structure of the first winding block BK1 and the winding structure of the second winding block BK2 are symmetrical with respect to the boundary line B (laterally symmetric). In particular, the positional relationship between the wires W1 and W2 in the first winding block BK1 and the positional relationship between the wires W1 and W2 in the second winding block BK2 are symmetrical. However, the positional relationship between the first and second wires W1, W2 in the first winding block BK1 and the second winding block BK2 is not symmetrical.

  For example, the first, second, and third turns of the first wire W1 of the first winding block BK1 are symmetrically related to the sixth wire of the first wire W1 of the second winding block BK2. , 5th and 4th turns, both being the first wire W1. The sixth wire of the second wire W2 of the second winding block BK2 is symmetrical with the first, second, and third turns of the second wire W2 of the first winding block BK1. , 5th and 4th turns, both being the second wire W2. Note that the symmetry is inevitably broken at the winding start and winding end positions, but such a slight deviation in symmetry is acceptable.

  As described above, when the winding structure of the first and second wires W1 and W2 is symmetric including the positional relationship of the wires, the capacity between different turns is uniform with respect to both the wires W1 and W2. Therefore, the impedance imbalance of the wires W1 and W2 can be suppressed. Therefore, Scd can be reduced and a high-quality common mode filter can be realized.

  Furthermore, when a space is provided between the first block and the second block as in the present embodiment, the effect of the left-right symmetric structure can be increased, and Scd can be sufficiently achieved. Can be reduced.

  The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention, and it goes without saying that these are also included in the present invention. Yes.

  For example, in the above-described embodiment, a drum core is used as a core around which a pair of wires are wound. However, the core in the present invention is not limited to the drum core, as long as it has a core portion for the pair of wires. Any shape of core may be used. Further, the number of turns (number of turns) of each wire may be larger than that in the above embodiment. For example, the layer winding may be 30 to 50 turns and the inductance may be about 200 to 400 μH, or the bifilar winding may be 15 to 25 turns and the inductance may be 100 to 200 μH.

1-5 Common mode filters 10a, 10b Inductors (coils)
11 drum core 11a winding core portion 11b, 11c flange portion 11bs, 11cs upper surface 12 of flange portion plate cores AR1, AR2, AR3 winding area B boundary lines BK1-BK5 winding blocks C0, C1, C2, C21, C22 capacitance E1 ~ E4 Terminal electrodes I1, I2 Inductor S1 Space area W1, W2 Wire

Claims (5)

A core having one and other ends in the longitudinal direction;
Comprising first and second wires wound around the core,
The first and second wires are wound from a first turn to an Nth turn from the one end of the core to the other end,
The i-th turn (i is 2 or more and N-2 or less) of the first wire is located closer to the one end of the core than the i-th turn of the second wire,
The i-1 turn of the second wire is located closer to the one end of the core than the i turn of the first wire,
The i-1 turn of the first wire is located closer to the one end side of the core than the i-1 turn of the second wire,
The j-th turn (j is not less than i + 1 and not more than N-1) of the first wire is located on the other end side of the core portion than the j-th turn of the second wire,
The j + 1 turn of the second wire is located closer to the other end of the core than the j turn of the first wire,
The common mode filter, wherein the j + 1 turn of the first wire is located closer to the other end of the core than the j + 1 turn of the second wire.   The common mode filter according to claim 1, wherein a space is provided between an i-th turn and a j-th turn of the first wire. The i-1th turn, ith turn, jth turn and j + 1th turn of the first wire are wound around the first layer on the winding core part,
The i-th turn and j-th turn of the second wire are wound around the first layer,
The common mode filter according to claim 1 or 2, wherein the (i-1) th turn and the (j + 1) th turn of the second wire are wound around a second layer on the first layer. The i-1th turn, ith turn, jth turn and j + 1th turn of the first wire are wound around the first layer on the winding core part,
3. The common mode filter according to claim 1, wherein the i−1th turn, the ith turn, the jth turn, and the j + 1th turn of the second wire are wound around the first layer.   The common mode filter according to claim 1, wherein j = i + 1.