JP7557665B2 - Common Mode Choke Coil - Google Patents

Description

The present invention relates to a common mode choke coil that includes a core and a wire, and in particular to a common mode choke coil that is suitable for use in a common mode filter that removes noise.

The trend towards electronics in the automotive market has been remarkable in recent years, with the number of electrical devices installed per vehicle continuing to increase. In-vehicle LANs are used for these communications, and in order to transmit large amounts of information, high speed and highly reliable communication quality are required. This has created a need for measures against unwanted radiation noise and common mode noise from high-frequency signals, and wire-wound common mode choke coils are widely used.

Such a common mode choke coil of the prior art is composed of a ferrite magnetic core with flanges formed on both sides of the winding core, a wire made of multiple insulating coated copper wires wound around the winding core of the magnetic core by bifilar winding or the like for several turns to several tens of turns, and a magnetic plate having approximately the same magnetic permeability as the magnetic core and having both flanges of the magnetic core bonded together with an adhesive. The magnetic core and magnetic plate are obtained by mixing ferrite powder with a binder, press molding, and then sintering the mixture. Furthermore, multiple electrodes are formed on both flanges or on one of the flanges, and the start and end ends of the wire are conductively connected to these electrodes by soldering, thermocompression, or the like. In such a common mode choke coil, the desired impedance value is obtained by appropriately setting the number of turns of the wire wound around the winding core of the core.
As examples of prior art literature related to the invention of this application, Patent Document 1 and Patent Document 2 are known.

JP 2003-168611 A JP 2014-75533 A

Conventionally, a common mode choke coil was sufficient for CAN communication, which has been widely used, but for even faster in-vehicle Ethernet communication, more advanced performance such as suppression of mode conversion characteristics is required. In general, as in Patent Document 1, a pair of windings is wound around a magnetic core so that they run parallel to each other in close contact, and the two wires are electrically connected at each contact point through the floating capacitance of the coating. Since the impedance of the floating capacitance component decreases as the AC signal becomes higher in frequency, a phenomenon occurs in which the AC signal leaks at each contact point of the two wires. If the signal flowing from the first winding side to the second winding side and the signal flowing from the second winding side to the first winding side can be canceled out by each other in this AC signal, good mode conversion characteristics can be obtained. In order to cancel the AC signal leaking through the coating in the two wires, it is effective to balance the impedance at each contact point of the two wires. For example, if the two wires could be wound to trace the same path over the entire area, including the connection, the impedance of the two wires would be considered to be in a nearly balanced state, and the mode conversion characteristics would be greatly reduced. However, because the connection positions of the winding terminals of the two wires are physically separated, strictly speaking the two wires do not trace exactly the same path, which hinders the reduction of the mode conversion characteristics. For products for Ethernet communications, a method is used in which the winding area is divided into multiple areas to control the stray capacitance of each wire and reduce the mode conversion characteristics, as in Patent Document 2, for example. However, this requires space to divide the winding areas, which leads to a deterioration of inductance.

In response to this problem, the present invention provides a magnetic core consisting of a winding core and a first flange and a second flange provided at both ends of the winding core, a first winding is wound directly around the winding core, a second winding is mainly wound around the first winding, an end portion of the first winding is connected to a first external electrode provided on the first flange and a second external electrode provided on the second flange, and an end portion of the second winding is connected to a third external electrode provided on the first flange and a second external electrode provided on the second flange. a first external electrode and a third external electrode having a connection portion formed on the same surface of the first flange, and a second external electrode and a fourth external electrode having a connection portion formed on the same surface of the second flange, each terminal portion being connected at the respective connection portions, and a magnetic plate being bonded so as to straddle the first flange and the second flange, is rectangular, and each turn is counted from the winding lead-out portion of the first winding and the second winding to the winding core portion, and each turn is designated as the first side, second side, third side, and fourth side as the winding proceeds along each surface of the winding core portion. The surface of the winding core portion corresponding to the first side of the first winding is designated the first surface, the surface of the winding core portion corresponding to the second side of the first winding is designated the second surface, the surface of the winding core portion corresponding to the third side of the first winding is designated the third surface, and the surface of the winding core portion corresponding to the fourth side of the first winding is designated the fourth surface. On the second surface, the n-turn second side of the second winding is located in the valley between the n-turn second side of the first winding and the n+1-turn second side of the first winding, and on the fourth surface, the n-turn fourth side of the second winding is located in the valley between the n-1-turn fourth side of the first winding and the n-turn first side of the first winding, and the second winding is wound so as to cross the first winding on the first and third surfaces.

By configuring it as described above, even if the first and second windings trace different physical trajectories, the impedance of the entire first and second windings can be kept nearly balanced, mode conversion can be suppressed, and high inductance can be achieved because there is no need for space that would cause inductance degradation with each turn.

FIG. 2 is an exploded perspective view of a common mode choke coil according to an embodiment of the present invention; FIG. 2 is a schematic diagram showing a first winding and a second winding wound in front of a winding core when a magnetic core portion of a common mode choke coil according to an embodiment of the present invention is viewed from a first direction; FIG. 2 is a schematic diagram showing a first winding and a second winding wound in front of a winding core when the magnetic core portion of the common mode choke coil according to the embodiment of the present invention is viewed from a second direction; FIG. 13 is a schematic diagram showing a first winding and a second winding wound in front of a winding core when the magnetic core portion of the common mode choke coil according to the embodiment of the present invention is viewed from a third direction. FIG. 13 is a schematic diagram showing a first winding and a second winding wound in front of a winding core when the magnetic core portion of the common mode choke coil according to the embodiment of the present invention is viewed from a fourth direction. FIG. 13 is a schematic diagram showing a part of a trajectory of a first winding wound around a winding core when a magnetic core portion of the common mode choke coil according to the embodiment of the present invention is viewed from a fifth direction; FIG. 13 is a schematic diagram showing a part of a trajectory of a second winding wound around a winding core when the magnetic core of the common mode choke coil according to the embodiment of the present invention is viewed from a fifth direction; FIG. 13 is a diagram showing the mode conversion characteristic (Sds21) of the common mode choke coil according to the embodiment of the present invention.

Below, a common mode choke coil according to one embodiment of the present invention will be described with reference to the drawings.

Figure 1 is an exploded perspective view of a common mode choke coil according to one embodiment of the present invention. The magnetic core 14 is made up of a winding core 11 and a first flange 12 and a second flange 13 provided at both ends of the winding core 11. A pair of insulating conductors are wound around the winding core 11 to form a winding. The winding is made up of a first winding 15 and a second winding 16, with the first winding 15 wound directly around the winding core 11 and the second winding 16 wound mainly on the first winding 15. The terminals of the first winding 15 are connected to the first external electrode 17 provided on the first flange 12 and the second external electrode 18 provided on the second flange 13, and the terminals of the second winding 16 are connected to the third external electrode 19 provided on the first flange 12 and the fourth external electrode 20 provided on the second flange 13, and a magnetic plate 22 is bonded to straddle the first flange 12 and the second flange 13. The first external electrode 17, the second external electrode 18, the third external electrode 19, and the fourth external electrode 20 are bonded to the flanges, and the ends of the windings are connected to a connection part provided on the surface that will be the mounting surface of the common mode choke coil.

The dimensions of this common mode choke coil are approximately 3.2 mm in length (in the winding direction), approximately 2.5 mm in width, and approximately 2.2 mm in height. The thickness of the magnetic plate 22 is approximately 0.6 mm. Furthermore, the windings use insulated conductor wire with a diameter of approximately 0.05 mm.

The first flange 12 and the second flange 13 each have a width of approximately 2.5 mm, a height of approximately 1.6 mm, and a thickness of approximately 0.7 mm.

The core portion 11 is approximately 1.0 mm wide, 1.0 mm high, and 1.6 mm long.

Figure 2 is a schematic diagram showing the first winding 15 and the second winding 16 wound in front of the winding core 11 when the magnetic core 14 of this common mode choke coil is viewed from a first direction. The dashed line shows the winding position of the first winding 15, and the solid line shows the winding position of the second winding 16.

Figure 3 is a schematic diagram showing the first winding 15 and second winding 16 wound in front of the winding core 11 when the magnetic core 14 of this common mode choke coil is viewed from a second direction.

Similarly, FIG. 4 is a schematic diagram showing the first winding 15 and the second winding 16 wound in front of the winding core 11 when the magnetic core 14 of this common mode choke coil is viewed from a third direction. FIG. 4 is upside down to make the winding positions correspond to FIGS. 2, 3, and 5. The dashed line indicates the winding position of the first winding, and the solid line indicates the winding position of the second winding.

Figure 5 is a schematic diagram showing the first winding 15 and second winding 16 wound in front of the winding core 11 when the magnetic core 14 of this common mode choke coil is viewed from the fourth direction.

The first winding 15 is connected to the first external electrode 17, wound around the winding core 11 from the winding lead-out portion 21a, and connected to the second external electrode 18 from the winding lead-out portion 21b. The circled numbers in Figures 2, 3, 4, and 5 indicate the number of turns of the first winding 15 and the second winding 16.

Figure 6 is a schematic diagram showing the path of the first winding 15 drawn from the first external electrode 17 to the winding core 11 and wound around the square-shaped winding core 11 when the flange portion of the common mode choke coil is viewed from the fifth direction. The dashed line in Figure 6 shows the path of the first winding 15 when it is wound. The first winding 15 is counted as one turn from the connection point between the winding draw-out portion 21a and the winding core 11, and each time the winding proceeds along each surface of the winding core 11, it is counted as the first side, second side, third side, and fourth side, and the second turn is counted when the winding goes around the outer circumference of the winding core 11 once through the first side, second side, third side, and fourth side. Thereafter, one turn is added each time the winding goes around the first side, second side, third side, and fourth side in the same manner.

7 is also a schematic diagram showing a part of the trajectory of the second winding 16 being drawn from the third external electrode 19 to the winding core 11 and wound around the square-shaped winding core when the flange of the common mode choke coil is viewed from the fifth direction. The second winding 16 is connected to the third external electrode 19, wound around the winding core 11 from the winding draw-out portion 21c, and connected to the fourth external electrode 20 from the winding draw-out portion 21d. However, strictly speaking, the second winding 16 is placed on the first winding 15 that is already wound, and the second winding 16 is placed on the valley where each turn of the first winding 15 contacts. Note that only the first and final turns of the second winding 16 pass through a part of the trajectory where the valley of the first winding 15 is not formed as shown in FIG. 7, so there are parts where the second winding 16 is directly wound around the winding core. Also, as shown in Figures 6 and 7, the first winding 15 and the second winding 16 start winding from the same position on the winding core 11.

When the surface of the winding core 11 corresponding to the first side of the first winding 15 is defined as the first surface 23, the surface of the winding core 11 corresponding to the second side of the first winding 15 is defined as the second surface 24, the surface of the winding core 11 corresponding to the third side of the first winding 15 is defined as the third surface 25, and the surface of the winding core 11 corresponding to the fourth side of the first winding 15 is defined as the fourth surface 26, on the second surface 24, the n-turn second side of the second winding 16 is positioned in the valley between the n-turn second side and the n+1-turn second side of the first winding 15 (see FIG. 3), and on the fourth surface 26, the n-turn fourth side of the second winding 16 is positioned in the valley between the n-1-turn fourth side and the n-turn fourth side of the first winding 15 (see FIG. 5).

On the first surface 23, the first side of n turns of the first winding 15 crosses the first side of n turns of the second winding 16 (see Figure 2), and on the third surface 25, the third side of n turns of the first winding 15 crosses the third side of n turns of the second winding 16 (see Figure 4).

By configuring it as described above, even if the first winding 15 and the second winding 16 are in close contact at multiple points and electrically interfere with each other, the impedance deviation can be significantly reduced, and the first winding 15 and the second winding 16 are in a nearly balanced state at each turn. This suppresses the mode conversion characteristics.

In the above embodiment, the cross section of the core is square, but it may be rectangular.

In addition, if the arrangement of the first winding and the second winding is substantially the same, the direction of rotation of the windings of the first winding and the second winding may be reversed from that of the above embodiment.

In FIG. 2, the final turn of the second winding 16 is wound directly around the winding core 11, but it may be wound between the final turn of the first winding 15 and the second flange 13. It may also be wound between the second flange 13 and the winding one turn before the final turn of the second winding 16. In this way, if the arrangement of the first winding 15 and the second winding 16 in the other wound turns is substantially the same as that shown in FIG. 2 to FIG. 5, the impedance balance state of the first winding 15 and the second winding 16 does not change to an extent that affects the characteristics, so the final turn of the second winding 16 does not have to be wound in the above-mentioned winding position.

Here, an experiment was carried out to confirm the effect of the electrical characteristics of the winding of the present invention. Specifically, 30 turns of copper wire insulated with polyamideimide and having a diameter of 0.04 mm were wound around the magnetic core 14 using the winding method shown in Figures 2, 3, 4, and 5, and the effect was confirmed by measuring the mode conversion characteristic (Sds21), which indicates the ratio of a common mode input signal converted to a differential output signal.

Figure 8 shows the actual measurement results of the mode conversion characteristic (Sds21). We were able to confirm an extremely good mode conversion characteristic suppression effect of -75 dB or less over a wide frequency band from 1 MHz to 100 MHz.

The common mode choke coil of the present invention brings the impedance of a pair of windings closer to an electrically balanced state, resulting in a common mode choke coil with excellent mode conversion characteristics and high inductance, making it industrially useful.

REFERENCE SIGNS LIST 11 Winding core portion 12 First flange portion 13 Second flange portion 14 Magnetic core 15 First winding 16 Second winding 17 First external electrode 18 Second external electrode 19 Third external electrode 20 Fourth external electrode 21a Winding lead-out portion 21b Winding lead-out portion 21c Winding lead-out portion 21d Winding lead-out portion 22 Magnetic plate 23 First surface 24 Second surface 25 Third surface 26 Fourth surface

Claims (1)

the magnetic core is provided with a winding core portion and a first flange portion and a second flange portion provided on both ends of the winding core portion; a winding consisting of a first winding wound directly around the winding core portion and a second winding wound mainly around the first winding; external electrodes consisting of a first external electrode and a third external electrode provided on the first flange portion and a second external electrode and a fourth external electrode provided on the second flange portion; a connecting portion connecting the external electrodes and terminal portions of the winding; and a magnetic plate bonded so as to straddle the first flange portion and the second flange portion;
an end portion of the first winding is connected to a first external electrode and a second external electrode, and an end portion of the second winding is connected to a third external electrode and a fourth external electrode,
a common mode choke coil, wherein the first external electrode and the third external electrode have connection wire portions on the same surface of the first flange, and the second external electrode and the fourth external electrode have connection wire portions on the same surface of the second flange ,
a cross section of the winding core portion is rectangular, and the first winding and the second winding are wound starting from the same position on the winding core portion,
When the first winding reaches the winding core part from its winding pull-out part, each turn is counted, and each turn as the winding progresses along each surface of the winding core part is called a first side, a second side, a third side, and a fourth side, the surface of the winding core part corresponding to the first side of the first winding is called a first surface, the surface of the winding core part corresponding to the second side of the first winding is called a second surface, the surface of the winding core part corresponding to the third side of the first winding is called a third surface, and the surface of the winding core part corresponding to the fourth side of the first winding is called a fourth surface,
a common mode choke coil in which, on the second surface, an n-turn second side of the second winding is arranged in a valley between an n-turn second side of the first winding and an n+1-turn second side of the first winding, and, on the fourth surface, an n-turn fourth side of the second winding is arranged in a valley between an n-1-turn fourth side of the first winding and an n-turn fourth side of the first winding, and, on the first surface and the third surface, the second winding is wound so as to cross the first winding, and further, on the first surface, an n-turn first side of the first winding crosses an n-turn first side of the second winding, and on the third surface, an n-turn third side of the first winding crosses an n-turn third side of the second winding.