JP5558609B1 - Common mode choke coil - Google Patents

Abstract

Provided is a common mode choke coil that reduces a stray capacitance between transmission lines and suppresses a differential inductance generated by a differential current.
A common mode choke coil is wound around a first signal wire and a second signal wire that constitute a transmission line, and the first signal wire and the second signal wire are wound together. And a bar core 5 for magnetically short-circuiting the magnetic core 4 is provided. Electrodes 6 and 8 and electrodes 7 and 9 are attached to the jaw portions 41 and 42 of the magnetic core 41, respectively. The ends of the first signal wire 2 and the second signal wire 3 are electrically connected to the electrodes 6, 7, 8, 9 attached to the magnetic core 4, respectively.
[Selection] Figure 1

Description

  The present invention relates to a technology of a common mode choke coil which is an electronic component used for measures against electromagnetic noise.

  Conventionally, a technique using a common mode choke coil has been proposed as a noise countermeasure in differential signal transmission. A common mode choke coil used for noise suppression in a signal transmission line has a problem that stray capacitance is generated between both lines. Further, when inductance is generated by a differential current, there is a problem that the transmission impedance is increased and the waveform of the transmitted signal is distorted. That is, in order to improve signal quality (SI: Signal Integrity), a common mode choke coil having a small stray capacitance between transmission lines and a small inductance generated by a differential current is required.

  In a common bifilar-wound common mode choke coil, two lines are wound in an alternately adjacent state, and each line forms a coil. In such a common mode choke coil, it is necessary to increase the number of turns in order to increase the impedance. However, since the bifilar-wound common mode choke coil has two lines wound close to each other, increasing the number of turns increases the stray capacitance between the two lines.

  Therefore, a common mode choke coil that does not increase the stray capacitance even if the impedance is increased (the number of turns is increased) is described in Patent Document 1, for example. The common mode choke coil described in Patent Document 1 has a structure in which a coil formed by each line is arranged on a straight line. That is, since each coil exists away from both ends of the core, there are few portions where both lines are close to each other, and even if the number of turns is increased, the portion does not increase.

JP2013-062477A

  However, even with the technique described in Patent Document 1, there is a problem that the signal quality is not sufficient only by reducing the stray capacitance between both lines in order to cope with further increase in transmission speed. .

  For example, the quality of the transmitted signal is also reduced by a decrease in the coupling coefficient (ideally 1.0) in the coil circuit formed by both lines. In particular, in the common mode choke coil described in Patent Document 1, the stray capacitance is reduced because the coils are arranged apart from each other, but the coupling coefficient is reduced, which causes the waveform of the differential signal to be distorted. was there.

  The present invention has been made in view of the above problems, and provides a technique related to a common mode choke coil capable of taking noise countermeasures on a differential signal line without distorting the waveform even in a signal in high-speed transmission. Objective.

In order to solve the above problems, the invention of claim 1 is a common mode choke coil, comprising: a first signal wire comprising a single wire; a second signal wire comprising a single wire; and the first signal wire. And a magnetic core wound around the signal wire and the second signal wire wound together.

  The invention according to claim 2 is the common mode choke coil according to the invention of claim 1, wherein the winding direction of the first signal wire with respect to the magnetic core and the magnetic core of the second signal wire with respect to the magnetic core. The winding direction is the same direction.

  The invention of claim 3 is the common mode choke coil according to the invention of claim 1 or 2, wherein the number of times the first signal wire and the second signal wire are wound together is two or more.

According to a fourth aspect of the present invention, there is provided the common mode choke coil according to any one of the first to third aspects, wherein the first signal wire and the second signal wire in a state of being wound together are attached to the magnetic core. The number of windings is 2 or more.
The invention according to claim 5 is the common mode choke coil according to any one of claims 1 to 4, wherein the first signal wire and the second signal wire in a state of being wound together are the magnetic It is wound directly around the body core.
A sixth aspect of the invention is a common mode choke coil according to any one of the first to fifth aspects of the present invention, wherein only the first signal wire and the second signal wire in a state of being wound together are the magnetic. Wound around the body core.

The invention according to any one of claims 1 to 6 includes a magnetic core that is wound in a state in which a first signal wire composed of one electric wire and a second signal wire composed of one electric wire are wound together. Thus, it is possible to suppress a decrease in the coupling coefficient between the coil formed by the first signal wire and the coil formed by the second signal wire while suppressing stray capacitance.

It is a figure which shows a common mode choke coil. It is a figure which shows the state which looked at the common mode choke coil shown in FIG. 1 toward the (+ Z) direction from the (-Z) side. It is the figure which looked at the common mode choke coil shown in Drawing 1 toward the (-X) direction from the (+ X) side. It is a flowchart which shows the manufacturing method of a common mode choke coil. It is a figure which illustrates the relationship between common mode impedance and a stray capacitance in the common mode choke coil of the conventional bifilar winding. It is a figure which shows the waveform of a differential signal when a stray capacitance is 0 [pF]. It is a figure which shows the waveform of a differential signal when a stray capacitance is 1 [pF]. It is a figure which shows the waveform of a differential signal when a stray capacitance is 2 [pF]. It is a figure which shows the waveform of a differential signal when a stray capacitance is 5 [pF]. It is a figure which shows the waveform of a differential signal when a stray capacitance is 10 [pF]. It is a figure which shows the frequency characteristic of the impedance of a common mode choke coil. It is a figure which shows the simulation result when a differential signal is input into a common mode choke coil. It is a figure which shows a circuit when the simulation result shown in FIG. 12 is obtained.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. However, unless otherwise specified in the following description, descriptions of directions and orientations correspond to the drawings for the convenience of the description, and do not limit, for example, a product, a product, or a scope of rights.

<1. Embodiment>
FIG. 1 is a diagram showing a common mode choke coil 1. FIG. 2 is a diagram illustrating a state in which the common mode choke coil 1 illustrated in FIG. 1 is viewed from the (−Z) direction toward the (+ Z) direction. FIG. 3 is a view of the common mode choke coil 1 shown in FIG. 1 as viewed from the (+ X) direction toward the (−X) direction.

  As shown in FIGS. 1 to 3, the common mode choke coil 1 includes a first signal wire 2, a second signal wire 3, a magnetic core 4, a bar core 5, four electrodes 6, 7, 8, 9 and. The common mode choke coil 1 in the present embodiment is a chip-shaped electronic component, and is configured as an electronic component for removing noise in the common mode when transmitting a signal.

  The magnetic core 4 is a member made of a magnetic material such as ferrite, for example. The magnetic core 4 in the present embodiment is a member (integrated structure) integrally molded from the magnetic material, but may be a structure in which a plurality of parts are combined, for example. The magnetic core 4 is formed with a central core portion 40 constituting a substantially cylindrical portion and jaw portions 41 and 42 constituting a substantially rectangular parallelepiped portion.

  The core part 40 of the magnetic core 4 is disposed so that the central axis of the cylinder is substantially parallel to the X-axis direction. In other words, the core portion 40 is disposed in the magnetic core 4 in a direction extending along the X-axis direction. As shown in FIGS. 1 and 2, the first signal wire 2 and the second signal wire 3 are wound around the cylindrical side surface of the core portion 40 in a state where they are wound together.

  The jaw portion 41 and the jaw portion 42 in the present embodiment are substantially the same shape portions formed on the magnetic core 4, and as shown in FIG. It has become a shape. That is, on the (−Z) side of the jaw part 41 and the jaw part 42, there are two abutment-like projections (parts projecting in the (−Z) direction, hereinafter simply referred to as “projections”). Is formed. And the tip part on the (−Z) side of each projection forms a plane substantially parallel to the XY plane.

  The jaw portion 41 of the magnetic core 4 is a portion formed at the (−X) side end portion of the core portion 40 extending along the X-axis direction. Thin plate-like electrodes 6 and 8 are attached to the tip portions of the two protrusions of the jaw 41 so as to be substantially parallel to the XY plane. In the present embodiment, the electrode 6 is disposed on the (−Y) side, and the electrode 8 is disposed on the (+ Y) side. In the jaw portion 41, the electrode 6 and the electrode 8 are insulated without contacting each other.

  The jaw portion 42 of the magnetic core 4 is a portion formed at the (+ X) side end portion of the core portion 40 extending along the X-axis direction. Thin plate-like electrodes 7 and 9 are attached to the tip ends of the two protrusions of the jaw 42 so as to be substantially parallel to the XY plane. In the present embodiment, the electrode 7 is disposed on the (−Y) side, and the electrode 9 is disposed on the (+ Y) side. Moreover, in the jaw part 42, the electrode 7 and the electrode 9 are insulated without contacting each other.

  As shown in FIG. 1 and FIG. 2, the first signal wire 2 and the second signal wire 3 are wound together in a portion wound around the magnetic core 4 (portion forming a winding). It has become. More specifically, in this portion, the number of times the first signal wire 2 and the second signal wire 3 are twisted together is 2 or more. The first signal wire 2 and the second signal wire 3 are wound directly around the magnetic core 4.

  Although not shown in detail, the first signal wire 2 and the second signal wire 3 are both covered with an insulating film (for example, a material with a low dielectric constant such as enamel is preferable). Accordingly, the first signal wire 2 and the second signal wire 3 are insulated from each other at least in a portion where a winding for the magnetic core 4 is formed. That is, the 1st signal wire 2 and the 2nd signal wire 3 comprise what is called a twisted pair wire in the portion which forms a coil.

  In addition, it is preferable that the 1st signal wire | line 2 and the 2nd signal wire | line 3 as a coil | winding are substantially the same length mutually. For example, when the first signal wire 2 is arranged in a straight line and the second signal wire 2 is spirally wound around the first signal wire 2, the length of the first signal wire 2 and the winding of the second signal wire 3 are This is not preferable because the length is different. Further, in order to suppress disturbance (non-uniformity) due to the position of the stray capacitance, it is preferable that the number of turns per unit length is uniform. On the contrary, when the disturbance due to the position occurs in the stray capacitance, the number of turns per unit length may be adjusted to make the stray capacitance uniform.

  In the portion where the first signal wire 2 and the second signal wire 3 form a winding with respect to the magnetic core 4, the first signal wire 2 and the second signal wire 3 wound together are the magnetic core 4. The inner core portion 40 is wound around the inner core portion 40 a plurality of times (two or more times) so as to draw a spiral. Thereby, the winding direction of the first signal wire 2 around the magnetic core 4 and the winding direction of the second signal wire 3 around the magnetic core 4 are always the same direction. Further, the winding direction of the first signal wire 2 with respect to the magnetic core 4 and the winding direction of the second signal wire 3 with respect to the magnetic core 4 are both wound in a certain direction without changing on the way. .

  As shown in FIG. 2, the (−X) side end of the first signal wire 2 is electrically connected to the (+ X) side surface of the electrode 8. Further, the (+ X) side end portion of the first signal wire 2 is electrically connected to the (−X) side surface of the electrode 9. Similarly, the (−X) side end of the second signal wire 3 is electrically connected to the (+ X) side surface of the electrode 6. In addition, the (+ X) side end of the second signal wire 3 is electrically connected to the (−X) side surface of the electrode 7. Thus, the electrodes 6, 7, 8, 9 constitute an input / output terminal for the common mode choke coil 1.

  The bar core 5 is a member formed of a magnetic material like the magnetic core 4, and is spanned between the jaw portion 41 and the jaw portion 42 of the magnetic core 4 as shown in FIG. It is a member. The bar core 5 is joined to the jaw part 41 and the jaw part 42 with, for example, an appropriate adhesive. The bar core 5 has a function of magnetically short-circuiting both ends (jaws 41 and 42) of the magnetic core 4 to form a closed circuit.

  The above is the description of the structure of the common mode choke coil 1. Next, a method for manufacturing the common mode choke coil 1 will be described.

  FIG. 4 is a flowchart showing a method for manufacturing the common mode choke coil 1. Before the process shown in FIG. 4 is started, the first signal wire 2, the second signal wire 3, the magnetic core 4 and the bar core 5 are separately manufactured as parts, and each of the magnetic core 4 It is assumed that predetermined electrodes 6, 7, 8, and 9 are already attached to the protrusions. Since these manufacturing methods can adopt conventional techniques as appropriate, description thereof is omitted here.

  First, the first signal wire 2 and the second signal wire 3 are wound together (step S1). The process shown in step S1 can be realized, for example, by a process similar to the process of manufacturing a twisted wire (twisted pair wire) conventionally.

  Next, the end portions in the same direction (end portions forming the pair) of the first signal wire 2 and the second signal wire 3 in a state of being twisted are pulled out to have appropriate lengths, and predetermined electrodes are formed by welding or the like. (Step S2). In the present embodiment, the end of the first signal wire 2 is connected to the electrode 8 and the end of the second signal wire 3 is connected to the electrode 6 in step S2. However, the present invention is not limited to this. For example, the end of the first signal wire 2 may be connected to the electrode 9 and the end of the second signal wire 3 may be connected to the electrode 7.

  When step S2 is completed, the magnetic core 4 is rotated with the cylindrical central axis of the core 40 as the central axis of rotation, and the first signal wire 2 and the second signal wire in a state of being wound around the core 40. 3 is wound up (step S3). Thereby, the 1st signal wire 2 and the 2nd signal wire 3 in the state where they were twisted together are wound around the magnetic core 4.

  In the prior art, since it was necessary to wind a pair of signal lines separately around the magnetic core or in opposite directions, the manufacturing process becomes complicated and the cost increases. there were. However, in the common mode choke coil 1 in the present embodiment, the winding direction of the first signal wire 2 and the second signal wire 3 around the magnetic core 4 is the same. As a result, when the common mode choke coil 1 is manufactured, the first signal wire 2 and the second signal wire 3 are handled as if they were one signal wire, so to speak, the two signal wires are bundled together. Can do. Therefore, the manufacturing method of the common mode choke coil 1 is simpler than the conventional technique, and the manufacturing cost of the common mode choke coil 1 can be suppressed.

  Next, the remaining ends of the first signal wire 2 and the second signal wire 3 are drawn out to appropriate lengths and connected to the electrodes (step S4). For example, in step S <b> 4, the end of the first signal wire 2 is connected to the electrode 9, and the end of the second signal wire 3 is connected to the electrode 7. By performing step S4, the attachment of the first signal wire 2 and the second signal wire 3 to the magnetic core 4 is completed.

  When the attachment (winding) of the first signal wire 2 and the second signal wire 3 is completed, the bar core 5 is joined to the jaw portions 41 and 42 of the magnetic core 4 using an appropriate adhesive or the like (step S5). . By attaching the bar core 5, both ends (jaws 41 and 42) of the magnetic core 4 can be magnetically short-circuited.

  As described above, the common mode choke coil 1 can be manufactured by performing the manufacturing method shown in FIG. Moreover, since the manufacturing method can manufacture the common mode choke coil 1 without requiring a complicated process, the cost of the manufactured common mode choke coil 1 can be suppressed.

  In general, signal quality (SI) degradation in common mode choke coils varies depending on factors such as stray capacitance between signal lines, disturbance of characteristic impedance due to differential inductance, or coupling coefficient between two coils. These factors are caused by complicated effects. In the common mode choke coil of the conventional bifilar winding (a method in which two signal lines are alternately arranged), the stray capacitance is proportional to the length of the winding, and the common mode inductance is the length of the line. It is proportional to the square.

  FIG. 5 is a diagram illustrating the relationship between common mode impedance and stray capacitance in a conventional bifilar-wound common mode choke coil.

  In a conventional bifilar-wound common mode choke coil, when the common mode impedance at 100 [MHz] is 260 [Ω], the generated stray capacitance is about 3.8 [pF]. At this time, the coupling coefficient between both lines was 0.987. In a conventional bifilar-wound common mode choke coil, both lines are arranged close to each other, and the coupling between both lines is high.

  6 to 10 are diagrams illustrating how the waveform of the differential signal changes depending on the value of the stray capacitance between the lines. FIG. 6 is a diagram illustrating a waveform of the differential signal when the stray capacitance is 0 [pF]. FIG. 7 is a diagram illustrating a waveform of a differential signal when the stray capacitance is 1 [pF]. FIG. 8 is a diagram illustrating a waveform of a differential signal when the stray capacitance is 2 [pF]. FIG. 9 is a diagram illustrating a waveform of a differential signal when the stray capacitance is 5 [pF]. FIG. 10 is a diagram illustrating a waveform of a differential signal when the stray capacitance is 10 [pF]. The examples shown in FIGS. 6 to 10 show waveforms when the transmission speed is 500 [Mbps] and the characteristic impedance is 100 [Ω].

  6 to 10, it can be seen that the waveform of the differential signal is greatly distorted as the stray capacitance increases. In general, unless the stray capacitance is suppressed within 2 [pF], the product cannot be practically used as a common mode choke coil. In order to make the stray capacitance within 2 [pF], the conventional bifilar-wound common mode choke coil can only increase the common mode impedance at 100 [MHz] to about 100 [Ω] (FIG. 5).

  On the other hand, in the split-winding common mode choke coil described in JP2013-062477A, when the common mode impedance at 100 [MHz] is 283 [Ω], the generated stray capacitance is 1.5 [Ω]. An example of pF] is shown. That is, the split-winding common mode choke coil has a stray capacitance reduced to about 1/2 to 1/3 as compared with the conventional bifilar winding. At this time, the coupling coefficient between both lines is 0.857. In the split-winding common mode choke coil, since both lines are arranged apart from both ends of the core, the coupling coefficient between both lines is considered to be low.

  The common mode choke coil 1 according to the present embodiment has a structure in which the first signal wire 2 and the second signal wire 3 are wound together, and the common mode impedance at 100 [MHz] is 240 [Ω]. The generated stray capacitance was 1.59 [pF]. As described above, it has been experimentally confirmed that the common mode choke coil 1 has a stray capacitance reduced to about 1/2 to 1/3 as compared with the conventional bifilar winding. At this time, the coupling coefficient between the two lines was 0.97.

  That is, it has been found that the common mode choke coil 1 is equivalent to the split-winding common mode choke coil with respect to the performance of suppressing stray capacitance. In addition, the coupling coefficient in the common mode choke coil 1 was found to be equivalent to that of a conventional bifilar-wound common mode choke coil. The common mode choke coil 1 according to the present embodiment is considered to have a high coupling coefficient because the first signal wire 2 and the second signal wire 3 are arranged close to each other.

  In the common mode choke coil 1 according to the present embodiment, the stray capacitance is reduced to about 1/2 to 1/3 as compared with the conventional bifilar wound common mode choke coil. By extending the length, it is possible to obtain a common mode impedance of about 2 2 times (4 times) to 3 2 times (9 times) with the same stray capacitance. Further, the coupling coefficient in this case is also high, and the deterioration of signal quality due to the reduction of the coupling coefficient is suppressed. Therefore, if the common mode choke coil 1 in the present embodiment is used, effective noise countermeasures can be achieved even in high-speed transmission.

  FIG. 11 is a diagram illustrating frequency characteristics of the impedance Z [Ω] of the common mode choke coil 1. FIG. 11 shows the frequency characteristics in the normal mode and the frequency characteristics in the common mode.

  11 that the common mode choke coil 1 has a large difference between the impedance in the normal mode and the impedance in the common mode at the same frequency. Therefore, the common mode choke coil 1 has sufficient characteristics even when the frequency is about 500 [MHz].

  FIG. 12 is a diagram illustrating a simulation result when a differential signal is input to the common mode choke coil 1. FIG. 13 is a diagram showing a circuit when the simulation result shown in FIG. 12 is obtained.

  Referring to FIG. 12, in the common mode choke coil 1, the rise of the differential signal at 500 [Mbps] is steep, and distortion of the differential signal is suppressed. Therefore, it can be seen that the common mode choke coil 1 is effective for noise suppression in high-speed transmission.

  As described above, the common mode choke coil 1 according to the present embodiment has the first signal wire 2, the second signal wire 3, and the first signal wire 2 and the second signal wire 3 wound together. By providing the wound magnetic core 4, a decrease in coupling coefficient between the coil formed by the first signal wire 2 and the coil formed by the second signal wire 3 is suppressed while suppressing stray capacitance. can do. Therefore, compared with the conventional technique, it is possible to take effective noise countermeasures even in high-speed transmission.

  Further, the common mode choke coil 1 has a simple manufacturing process because the winding direction of the first signal wire 2 around the magnetic core 4 and the winding direction of the second signal wire 3 around the magnetic core 4 are the same direction. Can be

<2. Modification>
Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made.

  For example, each process shown in the above embodiment is merely an example, and the order and contents may be appropriately changed as long as the same effect can be obtained. For example, when winding a winding wire around the magnetic core 4, the magnetic core 4 may be fixed and the winding wire may be moved. Alternatively, the magnetic core 4 may be wound by rotating the first signal wire 2 and the second signal wire 3 together. That is, the step of winding and the step of winding may be performed in parallel.

  Moreover, in the said embodiment, the example in which the 1st signal electric wire 2 and the 2nd signal electric wire 3 were wound around the core part 40 of the magnetic body core 4 was mutually demonstrated. However, for example, in a state where the first signal wire 2 and the second signal wire 3 are wound together, the first signal wire 2 and the second signal wire 3 are apparently covered and insulated with an insulating material having a low dielectric constant. And may be wound around the magnetic core 4 after constituting as if constituting one cable. By adopting such a structure, it is possible to mitigate the disturbance and looseness of the windings (the first signal wire 2 and the second signal wire 3).

  Further, when the ends of the first signal wire 2 and the second signal wire 3 are electrically connected to the electrodes 6, 7, 8, 9 respectively, the side surfaces (YZ plane) of the electrodes 6, 7, 8, 9 are not necessarily required. It does not have to be connected to a plane substantially parallel to). For example, you may connect to the surface (bottom surface) exposed to the (-Z) side. That is, as long as the manufacturing process (assembly process) can be simplified and the connection part (welding part) is attached so as not to be easily detached, the connection may be made in any way.

DESCRIPTION OF SYMBOLS 1 Common mode choke coil 2 1st signal electric wire 3 2nd signal electric wire 4 Magnetic body core 40 Core part 41,42 Jaw part 5 Bar core 6,7,8,9 Electrode

Claims (6)

A first signal wire consisting of one wire;
A second signal wire consisting of one wire;
A magnetic core wound around the first signal wire and the second signal wire wound together,
A common mode choke coil comprising: The common mode choke coil according to claim 1,
A common mode choke coil in which a winding direction of the first signal wire with respect to the magnetic core is the same as a winding direction of the second signal wire with respect to the magnetic core. The common mode choke coil according to claim 1 or 2,
A common mode choke coil in which the number of times the first signal wire and the second signal wire are wound together is 2 or more. The common mode choke coil according to any one of claims 1 to 3,
A common mode choke coil in which the number of times of winding the first signal wire and the second signal wire wound around the magnetic core is two or more. A common mode choke coil according to any one of claims 1 to 4,
A common mode choke coil in which the first signal wire and the second signal wire wound together are directly wound around the magnetic core. A common mode choke coil according to any one of claims 1 to 5,
A common mode choke coil in which only the first signal wire and the second signal wire wound together are wound around the magnetic core.

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