JP2569445Y2 - Choke coil for noise prevention - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a choke coil used for preventing electromagnetic noise generated, propagated or flying in electronic equipment, and more particularly to a choke coil for preventing noise having a wide frequency range to be prevented.

[0002]

2. Description of the Related Art The noise generated from electronic equipment is 10K.
It has a wide range of frequencies from Hz to 1 GHz, and its strength and propagation method are various. These noises may affect the functions of other electronic devices, or the electronic devices themselves may be affected by the noise of other devices. With the progress of digitalization of devices, prevention of noise has become an important issue. Generally, to prevent these noises, there is a simple and effective method.
Choke coils are used. In the prevention of noise by the choke coil, an impedance characteristic combining the loss of the magnetic core is used in a frequency region where the inductance and the inductance decrease. In order to obtain the impedance necessary for preventing noise, a large inductance is required in a low frequency region, and a relatively small inductance is sufficient in a high frequency region. In general, ferrite that can obtain various levels of magnetic permeability and has good frequency characteristics is used as a magnetic core for such applications.

[0003] However, for example, the above-mentioned 10 KHz
When trying to obtain a choke coil having effective noise prevention characteristics with a single magnetic core in a wide frequency range such as 1 GHz, the size and cost are low and the characteristics are very large at low frequencies. Therefore, it is required to have an appropriate magnetic permeability even in a high frequency region. However, the permeability and frequency characteristics of the magnetic core are in opposition to each other, that is, a high magnetic permeability has a low-frequency characteristic, and a low magnetic permeability has a high-frequency characteristic. Cannot satisfy the requirements of Therefore, as a countermeasure, for example, by superposing a magnetic core having a high magnetic permeability and a low frequency characteristic and a magnetic core having a low magnetic permeability and a high frequency characteristic to perform winding, the characteristics of the two magnetic cores are achieved. Although it is likely to be drawn out, in fact, it has almost high magnetic permeability and becomes almost equivalent to the characteristics of the magnetic core having low frequency characteristics, and thus it is impossible to obtain a noise prevention effect in a wide frequency range required. This is because anti-resonance occurs in a relatively low frequency range due to high inductance and winding capacitance in a low frequency range, and a necessary impedance cannot be obtained in a high frequency range.

Therefore, at present, in order to satisfy this requirement, for example, a low-frequency choke coil effective in the 10 kHz to 1 MHz band, a medium-frequency choke coil effective in the 500 kHz to 10 MHz band, and a high-frequency choke coil effective in the 10 MHz to 1 GHz band. A choke coil and approximately three types of choke coils are combined and connected to obtain a noise prevention effect in a wide frequency range. For this reason, naturally, the number of choke coils to be used increases, and the size of the device is increased, the assembly is troublesome, or the choke coils are combined with each other to cause interference between the choke coils, and a sufficient noise prevention effect cannot be obtained. And so on.

FIGS. 5 to 7 show a conventional choke coil. Conventionally, as shown in FIG. 5, a choke coil 101 for a high frequency band is formed by winding a winding 103 around a magnetic core (for example, a Ni—Zn ferrite, relative magnetic permeability 700, etc.) 102 having a low magnetic permeability.
a, 103b are wound. As shown in FIG. 6, the low frequency choke coil 104 is made of a magnetic core having a high magnetic permeability (for example, a Mn-Zn ferrite, a relative magnetic permeability of 4000, etc.).
5, windings 106a and 106b are wound. Further, as shown in FIG. 7, there is also a choke coil 107 in which a plurality of choke coils 101 and 104 having different characteristics are connected in series. This example is a case of two pieces, but in order to obtain a good noise prevention effect, choke coils having further different magnetic permeability or frequency characteristics are required.

Here, a more specific example will be described with reference to the frequency characteristics of actual impedance. FIG. 5 is vertical 1
A total of 26 turns of 6 turns and 20 turns are provided on two legs of the endless magnetic core 1 of Ni—Zn ferrite having a permeability of 700 and dimensions of 0.9 mm, 16.1 mm in width and 5 mm in thickness.
6 shows a choke coil provided with turn windings 103a and 103b. FIG. 6 shows that each of the two legs of the endless magnetic core 2 of Mn—Zn ferrite having the same size as that shown in FIG.
6 shows a choke coil having six turns of windings 106a and 106b. 5 and 6, the windings are connected such that the directions of the magnetic flux in the magnetic core match. FIG.
5 shows a choke coil 101 and 104 of FIGS. 5 and 6 connected in series. However, each winding frame shown in the figure is omitted, and the number of turns of the coil merely indicates that the winding is qualitatively performed. FIG. 4 shows curves indicating the frequency characteristics of the impedance of each of the choke coils 101, 104, and 107. From the impedance characteristics shown in FIG. 4, the choke coil 10 of FIG.
In the case of 1, an impedance sufficient for a noise prevention effect is obtained in a high frequency range of about 6 MHz or more, but 6 MHz
The following is not sufficient. In the case of the choke coil 104 of FIG. 6, the low frequency range is good, but the high frequency range of about 350 MHz or more is insufficient. Choke coil 10 of FIG.
In the case of 7, the impedance is almost equal to the sum of the impedances, and it can be seen that a sufficient noise prevention effect is obtained in the range of 10 KHz to 1 GHz.

[0007]

As described above, in the conventional choke coil, since the number of the choke coils is increased, the size is increased and the assembling is troublesome, and the choke coils whose individual characteristics are clear only are combined. For,
There is a problem that a case where sufficient effects cannot be obtained due to interference between the choke coils occurs.

An object of the present invention is to provide a small and inexpensive choke coil for noise prevention having an effective noise prevention effect in a wide frequency band.

[0009]

According to the present invention, there is provided a first endless shape having a high magnetic permeability and a low frequency characteristic.
And a second magnetic core partially joined to a part of the first magnetic core and having an endless shape having a lower magnetic permeability and a higher frequency characteristic than the first magnetic core. Core, a common winding wound around a joint between the two magnetic cores, and an individual winding wound around a non-joint between the two magnetic cores or one of the magnetic cores. The choke coil for noise prevention is characterized in that the winding is connected to the common winding such that the magnetic flux is generated in a direction coinciding with the direction of the magnetic flux generated in each magnetic core portion by the common winding. Can be

Further, according to the present invention, in the noise preventing choke coil, windings having exactly the same combination as the windings to which the common winding and the individual windings are connected are viewed from the input terminal or the output terminal. A common mode noise preventing choke coil provided with winding directions opposite to each other is obtained.

Further, according to the present invention, in the noise preventing choke coil, the two magnetic cores are mounted and fixed on a substrate or a frame provided with a winding connection portion and an external connection terminal. A noise preventing choke coil is obtained, wherein the common winding and the individual winding are each connected by a winding connection portion on a substrate or a frame.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to a specific embodiment, the impedance of a choke coil and the effect of preventing noise will be outlined. The effect on the noise is contributed by the impedance of the choke coil, and in order to play the role of effective noise prevention, an impedance of approximately 500Ω or more is required over the entire noise generation frequency. As is well known, the magnetic permeability of the magnetic core in an alternating magnetic field is expressed by complex magnetic permeability (= impedance magnetic permeability) μ _c = μ′−iμ ″, μ ′ is equal to the inductance magnetic permeability, and μ ″ is equal to the inductance. Shows the contribution to loss. Therefore, the impedance of the choke coil is a combination of the impedance based on the inductance of the coil and the impedance due to loss such as iron loss of the magnetic core.

Hereinafter, the present invention will be described in detail with reference to embodiments. FIG. 1 shows one embodiment of the present invention. The noise preventing choke coil 1 of the present invention has a first magnetic core 2 having an endless shape having a high magnetic permeability and a low frequency characteristic, and a part of the first magnetic core 2 is partially joined to the first magnetic core 2. And a second magnetic core 3 having an endless shape having a lower magnetic permeability and a higher frequency characteristic than the first magnetic core 2, and is wound around a joint between the two magnetic cores 2 and 3. It comprises a common winding 4 and individual windings 5 and 6 wound around the non-joined portions of the magnetic cores 2 and 3. The common winding 4 has 6 turns, the individual winding 5 has 70 turns, and the individual winding 6 has 20 turns. This is an example in which windings and connections are made such that the magnetic fields generated by the individual windings 5 and 6 are in the same direction inside each magnetic core. In this case, as shown by the curve in FIG. 4, almost the same characteristics as those of the conventional choke coil 107 shown in FIG. 7 can be obtained. That is, the choke coil 10 shown in FIG.
7, one less number of windings is required. In order to obtain a noise prevention effect in a wide frequency range, it is necessary to reduce the capacity of the winding as much as possible. In particular, the magnetic core 3 having a low frequency characteristic has a large number of windings in order to obtain a large inductance in a low frequency range, and it is necessary to consider the winding capacity. Since the magnetic core 2 having high frequency characteristics may have a relatively small inductance, the number of windings may be small and the winding capacity may be small in many cases. Therefore, the winding of the magnetic core 2 may be performed only at the joint, in which case the number of windings can be further reduced.
Further, the endless magnetic core referred to in the present invention does not necessarily mean only an integrally fired magnetic core without any seam, but for example, U core
The effect of the present invention is the same even in the case of a joint type such as an I-shaped magnetic core.

FIG. 2 shows another embodiment of the present invention. In FIG. 2, reference numerals 2 and 3 denote the above-described cores for the low frequency band and the high frequency band, respectively. The width of the leg of the joint of each of the magnetic cores 2 and 3 is one of the width of the leg of the non-joint where the individual winding is applied.
/ 2, and the thickness and width of the leg portions on which the individual windings of the non-joined portions are applied in the joined state are made equal. In this combination of the magnetic cores 2 and 3, the same winding frame (not shown) can be used because the dimensions of the winding portions of the joined portion and the non-joined portion are equal.

FIG. 3 shows another embodiment, wherein reference numerals 2 and 3 denote the above-mentioned low-frequency and high-frequency magnetic cores, respectively.
4 is a common winding of the junction of the above two types of magnetic cores 2, 3, 5, 6
Indicates an individual winding of a non-joined portion of each of the magnetic cores 2 and 3. Reference numeral 7 denotes a printed circuit board or a frame, and a connection portion and a conductor portion (not shown) for connecting the windings 5, 4, and 6 to the front surface, the back surface, or the inside thereof, and a drawing connection to equipment. It has a terminal 8. If necessary, a concave portion or a convex portion (not shown) may be provided so that the magnetic core, the winding, and the like can be closely contacted and aligned. In the description of the embodiment of the present invention, a normal mode type choke coil is exemplified. In addition to the common winding 4 and the individual windings 5 and 6, windings of exactly the same combination are input to each winding. A common mode choke coil having exactly the same effect can be obtained by providing the winding direction in the opposite direction as viewed from the end or the output end.

[0016]

The noise preventing choke coil according to the present invention has an effective noise preventing effect in a wide frequency band, and is small and inexpensive.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of the present invention.

FIG. 2 is a perspective view showing a main part of another embodiment of the present invention.

FIG. 3 is a perspective view showing another embodiment of the present invention.

FIG. 4 is a diagram showing characteristics of the impedance of the choke coil for preventing noise according to the present invention and the related art.

FIG. 5 is a perspective view showing a conventional example.

FIG. 6 is a perspective view showing another conventional example.

FIG. 7 is a perspective view showing another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Noise prevention choke coil 2, 3 Magnetic core 4 Common winding 5, 6 Individual winding 7 Printed circuit board

Claims (3)

(57) [Scope of request for utility model registration] 1. A first magnetic core having an endless shape having a high magnetic permeability and a low frequency characteristic, a part of the first magnetic core being joined to a part of the first magnetic core, and A second endless shape with low permeability and high frequency characteristics compared to the core
Core, and a common winding wound around a joint between the two magnetic cores, and an individual winding wound around a non-joint between the two magnetic cores or one of the magnetic cores, A noise preventing choke coil, wherein the individual winding is connected to the common winding so that a magnetic flux is generated by the common winding in a direction coinciding with a direction of a magnetic flux generated in each magnetic core portion. . 2. The choke coil for noise prevention according to claim 1, wherein a winding having exactly the same combination as a winding to which the common winding and the individual winding are connected is viewed from an input end or an output end. A common mode type noise prevention choke coil provided in opposite directions. 3. The choke coil for noise prevention according to claim 1, wherein the two magnetic cores are mounted and fixed on a substrate or a frame provided with a winding connection portion and an external connection terminal, and the common core is fixed. A choke coil for preventing noise, wherein each of the winding and the individual winding is connected by a winding connection portion on a substrate or a frame.