JPS6338220A - Common mode choke coil for pulse transmission line - Google Patents

Abstract

PURPOSE:To provide good particle characteristics over a wide band to a common mode noise current which conducts through a transmission line thereby to be able to apply it to a high speed pulse transmission line by forming a densely concentrated winding on the short axis magnetic path of symmetrical magnetic paths, and forming a rough winding on a part except the part on which the concentrated winding is wound. CONSTITUTION:A closed magnetic path core 12 has a long axis X-X and a short axis Y-Y, and is so formed symmetrically with respect to the axis Y-Y that a distance between opposed magnetic paths becomes maximum near the axis Y-Y. Windings 13, 13 are formed in a multilayer or concentrically wound at that part of the length l0 of the core 12 where the distance between the opposing magnetic paths is maximum. Windings 15, 15' are roughly wound uniformly oppositely to the parts of lengths l1, l2 longer than l0 of the core 12, and the winding directions of the windings wound between input/output terminals 10-11 and 10'-11' are so formed so that magnetic fluxes generated in the core 12 are in the same direction of a common mode current flowing in phase from one terminal and strengthen each other.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a common mode choke coil that blocks high frequency common mode noise transmitted in the same direction in a pulse balanced transmission line over a wide band.

[Prior art]

FIG. 9 is a diagram for explaining the conduction status of common mode noise t″f current due to the induction of pulse signals and external electromagnetic noise conducted in a balanced transmission line, where 1°1′ is a balanced transmission line, 2 is a A pulse signal transmission device 8n connected to the transmission lines 1 and 1' is a digital signal consisting of a pulse train transmitted through the transmission lines 1 and 1', 3 is a building such as a telephone office in which the device 2 is housed, and 4 is a broadcasting device. wave.

External noise from radio waves, high frequency equipment, etc., Nc is a common mode noise current due to induction of external noise 4 into transmission lines 1, 1', 5 is communication terminal equipment connected to transmission lines 1, 1',
6 is the ground impedance of the communication terminal equipment 5, and 7 is a common mode choke coil inserted into the signal input section of the terminal (4n terminal) li+5 to prevent the intrusion of the common mode 1 to noise current Nc flowing through the transmission path. .

Further, FIG. 10 is an explanatory diagram of the common mode choke coil shown in FIG. 9 using a circular toroidal core that has been widely used in the past. Winding wound into 10.1
0' and 11.11' are the input and output terminals of windings 9 and 9', respectively. The winding direction of the windings 9 and 9' with respect to the core 8 is such that the magnetic flux generated in the core 8 is in the same direction as the common mode current flowing in the same phase from the input terminal 10.10' or the output terminal 11.11'. They are wound so that they strengthen each other. In FIG. 10(A), the windings 9 and 9' are wound to face the core 8, and in FIG. 10(B), the windings 9 and 9' are wound together. In FIG. 10, C is the capacitance existing between the input and output windings.

[Problem that the invention seeks to solve]

The blocking effect against common mode noise current Nc in such a common mode choke coil is determined by the inductance L and the capacitance C, and the larger the inductance L and the smaller the capacitance C, the better the blocking characteristics over a wide band. especially.

The high frequency characteristics are influenced by the capacitance C, and the smaller the capacitance C is, the more high frequency noise can be blocked. On the other hand, the inductance L is
It is known that when the magnetic permeability of the core is μ, the cross-sectional area is S9, the number of turns is N, and the average magnetic path length of the core is d, it is expressed as L=μSN2/d. Therefore, assuming that the material and shape of the core are constant, it is necessary to increase the number of turns N in order to obtain a large inductance L. However, when the number of turns N is increased, the windings are wound within a circle determined from the inner diameter of the circular core. are crowded together, the capacitance C between the output terminals due to multiple windings increases, and the high frequency characteristics deteriorate.

That is, FIG. 11 is an electrical equivalent circuit diagram of the common mode choke coil as shown in FIG. , 9' to pass through capacitance C to the other side.

It does not act as an inductance L, and the noise blocking effect is reduced. In particular, if the number of turns N is increased by crowding adjacent wire windings around a core of a certain shape as shown in FIG. The capacitance between the windings 9 and 9' increases, and the capacitance C inserted between the lines of the transmission line -3=1.1' shown in FIG. 9 increases as a whole.

When such a common mode choke coil is used in a digital signal transmission line, it has an effect on pulse transmission. That is, (A) in FIG. 12 is an example of a digital signal Sn (normal mode) consisting of a pulse train flowing between transmission lines 1 and 1', and (B) is an example of a digital signal Sn (normal mode) consisting of a pulse train flowing between transmission lines 1 and 1'. An example of the waveform of a transmission signal when a common mode choke coil with a large line capacitance kk Cs is inserted is shown.

In other words, the influence of the accumulation of capacitors Cs appears and the waveform becomes distorted. As a result, in Fig. 9, transmission lines 1, 1'
The digital signal (pulse transmission signal) Sn used for original information transmission is deformed by the common mode choke coil inserted to block the common mode noise current Nc. The influence of this capacitance Cs becomes larger as the pulse rise time and pulse width of the pulse transmission signal Sn become smaller and the faster the transmission becomes, and in extreme cases, the accumulation of capacitance Cs may cause a line short-circuit, which may affect the normal operation of communication terminal equipment. There are drawbacks that may hinder operation or make it unusable. On the other hand, if the number of turns N of the common mode choke coil is reduced in order to avoid this, the inductance L cannot be increased, so the noise current Nc cannot be sufficiently blocked, and the external noise 4 may cause trouble such as malfunction of the communication terminal equipment. There was a problem with causing it.

In this way, when conventionally used common mode choke coils are applied to pulse transmission lines, those that do not affect the pulse signal cannot achieve a broadband blocking characteristic against external noise, and those with good noise blocking characteristics cannot be achieved. The problem was that it could not be applied to pulse transmission lines.

An object of the present invention is to provide a common mode choke coil that has good blocking characteristics over a wide band against common mode noise current conducted through a transmission line and can be applied to a high-speed pulse transmission line.

The above and other objects and novel features of the present invention are explained by the following description of the specification and the accompanying drawings.

[Means for solving problems]

A brief overview of typical inventions disclosed in this application is as follows.

In a common mode choke coil in which two windings are wound so that magnetic fluxes in the same direction are generated in a closed magnetic circuit core having an effective magnetic permeability of a certain value or more up to a predetermined high frequency region, the closed magnetic circuit core is Among the short and long axes that are orthogonal to each other, the short axis and the long axis are symmetrical about the long axis, and the distance between the symmetrical magnetic paths is maximized at the short axis, and the concentrated winding is concentrated in the short axis magnetic path. The main feature is that sparse uniform windings are wound oppositely in the symmetrical magnetic path portion except for the concentrated winding portion.

[Effect]

According to the above means, the closed magnetic path core has a long axis and a short axis that are orthogonal to each other, and is formed symmetrically with respect to the long axis so that the opposing distance of the symmetrical magnetic path is maximized at the short axis portion, By applying densely concentrated windings to the short-axis magnetic path portion of this symmetrical magnetic path, and sparsely concentrated windings to areas other than the portions of the symmetrical magnetic path where densely concentrated windings have been applied, input/output with a large number of turns is possible. Since increases in capacitance C between terminals and capacitance between opposing lines are suppressed, and inductance L increases, pulse transmission is not adversely affected at all, and common mode conduction noise can be blocked over a wide band. .

Therefore, when applied to a transmission line such as a high-speed digital transmission line where the rise is fast, the pulse width is small, and the repetition is quick, the common mode noise having a wide frequency component that is transmitted through the transmission line does not affect the transmitted signal. can be prevented.

[Embodiments of the invention]

Embodiments of the present invention will be specifically described below with reference to the drawings.

In addition, in all the figures for explaining an example.

Components having the same function are given the same reference numerals, and repeated explanations thereof will be omitted.

[Example ■]

FIG. 1 (explanatory diagram) shows a schematic configuration of a common mode choke coil for a pulse transmission line according to Embodiment 2 of the present invention.

In FIG. 1, 12 indicates a magnetic permeability μ and an average magnetic path length d, which are comparable to those of the conventional circular toroidal core 8 shown in FIG.
, is a closed magnetic circuit core having a cross-sectional area S, has a long axis XX and a short axis Y-Y, is symmetrical about the long axis XX, and has a gap between opposing magnetic paths near the short axis Y-Y portion. It is formed to maximize the distance. Moreover, 13.13' is the length Q of the closed magnetic circuit core 12 with the maximum distance between opposing magnetic paths. It is a winding that is wound in multiple layers or in a concentrated manner. 14.14' and winding 15.15' are the above a of the closed magnetic circuit core 12. These windings are wound sparsely and evenly opposite the lengths Q and Q above, and these windings are wound between input/output terminals 10-11 and input/output terminals 10'-11'. The winding direction of the wire is such that the magnetic flux generated in the closed magnetic circuit core 12 in response to the common mode current flowing in the same phase from one terminal is in the same direction and strengthens each other. Co, C1゜C2
are windings 13, 14, 15 and windings 13', 14',
The capacitance between the windings 13' and 13' is the capacitance between the windings 15' and 15', and the capacitance C6 between the windings 13' and 13' has a large value because of the concentrated winding. The capacitance C□, C2 between both ends of ゜15 and 14', 15' is
Each has a small value. On the other hand, concentrated winding 11A13,1
3' is.

Since the closed magnetic circuit core 12 is wound near the short axis Y-Y portion where the facing distance is the largest, even if the number of windings is large, if the facing gap g between both windings is kept above a certain level, the winding 13
．． 13' opposing capacitance Cso can be configured to be small. Also, the opposing capacitance Cs1 between the windings 14 and 14' and between the windings 15 and 15'. Cs2 is small because each of these windings is loosely wound.

Fig. 2 is an electrical equivalent circuit diagram of the common mode choke coil shown in Fig. 1. In order to increase the inductance L, when the winding N is increased using the winding method described above, the increased capacitance is It is possible to suppress the increase in both the capacitances c11 C2+ Csa Hcsl and Cs2. Therefore, input/output terminal 10-11 and input/output terminal 10'-11'
Of the capacitors C6, C, and C2 inserted in series between them, the capacitor tc. Even if the value of is large, the overall capacitance C between the input and output terminals does not become large. Also, the capacitance Cs,, Cs,
, Cs2 are both small.

increase can be suppressed.

As can be seen from the above explanation, if the common mode choke coil of FIG. 1 is applied in place of the common mode choke coil 7 of FIG. 9, there will be no effect on the normal mode pulse transmission signal Sn. In addition, with respect to the common mode noise current Nc due to the external noise 4, the inductance L is large and the capacitance C between the input and output terminals is small, so that the noise current Nc can be blocked over a wide band.

[Example II] A schematic configuration of a common mode choke coil for a pulse transmission line according to Example H of the present invention is shown in FIG. 3 (explanatory diagram).

16 is an elliptical closed magnetic circuit core with a long axis x-x and a short axis Y-Y, and 17.17' is a core near the short axis Y-Y where the distance between opposing magnetic paths is maximum. Windings 18.18' and 19.1 wound intensively opposite to the magnetic path section.
Reference numeral 9' denotes a winding that is wound loosely opposite to the magnetic path portion other than the winding of the winding 17 and 17'. In this embodiment (2), since the shape of the closed magnetic circuit core 16 is smooth, there is less leakage of magnetic flux generated in the core 16 due to noise current flowing through the winding, and compared to the one in FIG. 1, when the number of turns is the same, Inductance1. It has the advantage of being able to increase the size of

[Example ■]

FIG. 4 (explanatory diagram) shows a schematic configuration of a common mode choke coil for a pulse transmission line according to Example 2 of the present invention. (A) in Figure 4 shows the cross-sectional magnetic path (shaded area) along the closed magnetic path loop.
FIG. 3B is a diagram showing windings applied to the core, and (B) is an external view of only the core.

In Fig. 4, 20 is a closed magnetic circuit core, 21.21'l:
The windings 22, 22' and 23, 23', which are wound intensively opposite to each other on the short axis portion of the core 20, are the core 20.
-1: This is a winding wound opposite to the core portion other than the winding 21 and 21'.

The commode choke coil for pulse transmission line of this embodiment (■) is based on the example (2) of Fig. 1, and the vertical and horizontal dimensions of the core outer diameter (
hxp) are each constrained to be constant,
As shown in Fig. 4, since the outer diameter of the core at the short axis portion is kept constant, the thickness of the core is made thinner so that more windings can be wound in this portion = 11 = min. By expanding the core cross-sectional area perpendicular to the closed magnetic path as a whole by expanding it in the height and width directions, the first
The same effect as shown in the figure is obtained.

With this configuration, even when the outer diameter size is reduced, the number of turns N can be increased, so that the inductance L does not decrease.

5 to 8 are explanatory diagrams of an embodiment of the core of the present invention for facilitating the winding method during assembly, and FIG. 5 shows the core 12 of FIG. K) is a configuration diagram in which cores 12A and 12B, which are divided into two, are assembled using a U-shaped leaf spring 24.

FIG. 6 is an exploded perspective view of FIG. 5, and the retainers a, a', b, and b' of the spring 24 and the cores 12A and 12B are made flat so that they do not shift due to the fitting of the springs. be.

Figure 7 shows that the elliptical core in Figure 3 is similarly divided into two equal parts along the long axis, and planes a, a', b, and b' are provided on the outside of the core's long axis to hold the spring. It is something.

Figure 8 shows the short axis of the core bulging outward in the same way.
This uses cores 25Δ and 25B that extend linearly toward both sides. In all of these, the coil winding can be performed in an open magnetic path state in which the closed magnetic path is divided into two, and then the closed magnetic path can be assembled using leaf springs, so that winding can be easily performed.

The present invention has been specifically explained above based on examples, but
It goes without saying that the present invention is not limited to the embodiments described above, and can be modified in various ways without departing from the spirit thereof.

〔Effect of the invention〕

As explained above, according to the present invention, the closed magnetic circuit core has a long axis and a short axis that are orthogonal to each other, and is symmetrical about the long axis, and the opposing distance of this symmetrical magnetic path is maximized at the short axis portion. A densely concentrated winding is applied to the short-axis magnetic path portion of this symmetrical magnetic path, and a sparsely concentrated winding is applied to the portion of the symmetrical magnetic path other than the portion where the densely concentrated winding is applied. This suppresses the increase in the capacitance C between the input and output terminals and the increase in the capacitance between the opposing windings due to the large number of turns, and increases the inductance L, so there is no adverse effect on pulse transmission and common mode conduction noise is suppressed. Current can be blocked over a wide band.

Therefore, when applied to a transmission line such as a high-speed digital transmission line where the rise is fast, the pulse width is small, and the repetition is quick, common mode noise current with a wide frequency component that does not affect the transmitted signal and is conducted through the transmission line. can be prevented.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a schematic configuration of a commode choke coil for a pulse transmission line according to Embodiment I of the present invention, FIG. 2 is an electrical equivalent circuit diagram of FIG. 1, and FIG. 3 is an illustration of the present invention. FIG. 4 is an explanatory diagram showing a schematic configuration of a commode choke coil for a pulse transmission line according to Example (■) of the present invention; FIG. FIG. 5 is a configuration diagram in which the core of FIG. 1 is divided into two equal parts along the long axis and assembled using a U-shaped leaf spring. FIG. 6 is an exploded perspective view of FIG. 5. Figure 7 shows that the elliptical core in Figure 3 is similarly divided into two equal parts along the long axis, and planes a, a', b, and b' are provided on the outside of the core's long axis to hold the spring. Figure 8 shows the short axis of the core bulging outward in the same way.
Figure 9 is an explanatory diagram of the conduction situation of pulse signals and external noise current in a balanced transmission line. Figure 10 is a common diagram using a conventional circular toroidal core. An explanatory diagram of the mode choke coil, FIG.
FIG. 12 is a pulse transmission waveform diagram when a conventional common mode coil is used. In the figure, 12.16.20...Closed magnetic circuit core, 13.13'
, 17°17', 21.21'...Dense concentrated winding, 14, 14', 15. 15
', 18. 18', 19. 19', 2
2. 22'. 23.23'... Loosely wound winding, 24... Spring, 25A. 25B...Core.

Claims (1)

[Claims] (1) In a common mode choke coil in which two windings are wound in a closed magnetic circuit core having an effective magnetic permeability of a certain value or more up to a predetermined high frequency region so that magnetic flux is generated in the same direction for an in-phase current, the closed magnetic Among the short axis and long axis that are perpendicular to each other, the path core is symmetrical with respect to the long axis, and the distance between the symmetrical magnetic paths is maximized at the short axis part, and the concentrated winding is dense in the short axis magnetic path part. 1. A common mode choke coil for a pulse transmission path, characterized in that a wire is wound with equal windings sparse in the symmetrical magnetic path portions excluding the concentrated winding portions, each facing the other.