JP2010182875A - Common mode choke coil and noise filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a common mode choke coil designed to improve a frequency characteristic using an easily obtainable core material, and a noise filter applied with such a common mode choke coil. <P>SOLUTION: The choke coil is configured by winding a winding wire 3 (a first winding wire 31; a second winding wire 32) on a core 2 composed of magnetic bodies 4a, 4b each having a practical upper limit frequency of the magnetic permeability of about 1 MHz, and by disposing gaps 5a, 5b in a predetermined position of the closed magnetic path formed of the magnetic bodies 4a, 4b, the gap length of the gaps 5a, 5b is selected so that the upper limit frequency functioning as an inductance is several MHz or higher. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to, for example, a noise filter that is connected to a commercial power supply, a power line inside a power supply system, or a ground line, and is used to suppress high-frequency pulsation components and noise flowing out from the power supply side, and such a noise filter. The present invention relates to a common mode choke coil applied to the above.

Two types of filter reactors, which are noise filters used in power supply devices such as semiconductor power converters, are a common mode choke coil for countermeasures against common mode noise (leakage current) and a normal mode choke coil for reducing switching ripple. Things are well known.
FIG. 8 is a circuit diagram showing a configuration example of a conventional noise filter using a general common mode choke coil and a normal mode choke coil.
In FIG. 8, the noise filter 80 is provided with a common mode choke coil Lc1 and a normal mode choke coil Ln1 as shown between input side terminals Ri, Si, Ei and output side terminals Ro, So, Eo. Yes. The input side terminals Ri, Si, Ei are connected to a power supply 81, and the output side terminals Ro, So, Eo are connected to an electric device (not shown).

A noise reducing capacitor Cx1 is connected between the input side terminals Ri and Si on the power supply 81 side of the common mode choke coil Lc1.
A noise reducing capacitor Cy1 is connected between the S-phase line on the output side of the common mode choke coil Lc1 and the ground, and a noise reducing capacitor is connected between the R-phase line on the output side of the common mode choke coil Lc1 and the ground. A capacitor Cy2 is connected.
Further, a noise reduction capacitor Cx2 is connected between the S-phase line and the R-phase line on the output side of the common mode choke coil Lc1.
Arranging the common mode choke coil Lc1 as in the noise filter of FIG. 8 is a known technique even in the patent literature (see, for example, patent literature 1).

Further, the arrangement of the normal mode choke coil Ln1 as in the noise filter of FIG. 8 is also a known technique according to the patent literature (see, for example, patent literature 2).
Various improvements have been proposed for the common mode choke coil. Below, some examples of those proposals will be described.
(Integrated with normal mode choke coil)
The common mode choke coil is originally a noise countermeasure component for reducing common mode noise, but is also used for reducing normal mode noise by utilizing its leakage inductance component.

However, the noise of the normal mode component is large, and there are cases where it cannot be sufficiently reduced only by suppression using the leakage inductance component. In such a case, both the common mode choke coil and the normal mode choke coil are required as shown in FIG. 8, and problems such as an increase in the number of parts and an increase in the size of the apparatus occur.
In order to cope with the problem of the enlargement as described above, a technique has already been proposed in which a noise filter is configured by arranging a choke coil in the direct current portion of the rectifier diode in the power converter as shown in FIG. (For example, refer to Patent Document 3).

In this proposal, that is, a filter is configured by dividing a choke coil into a high-voltage side and a low-voltage side line of the DC section, and attenuation characteristics of both a common mode component and a normal mode component can be obtained. In this way, a choke coil having a so-called composite characteristic is constructed.
Specifically, the choke coil having the composite characteristics described above has been proposed to be configured as follows.
FIG. 10 shows a reduction in the size of the noise filter unit by increasing the leakage inductance while winding the winding in the same manner as the common mode choke coil (see, for example, Patent Document 4).

  In the noise filter of FIG. 10, a pair of protrusions 122 and 123 are formed so as to protrude from and approach each other from the opposed portions that are not used for coil winding in the core 121 around which the windings 111 and 112 are wound. In this way, an independent closed magnetic circuit is formed for each of the windings 111 and 112 so that the leakage magnetic flux actively passes through the protrusions 122 and 123 of the windings. As a result, a leakage inductance larger than that of a general common mode choke coil can be formed, so that a normal mode component of noise can be suppressed.

In addition to the above, a technology for realizing a noise prevention choke coil that can suppress small common mode noise, normal mode noise, and high frequency noise that have both large common mode inductance and normal mode inductance Has been proposed.
For example, two outer cylindrical cores such as two bottomed cylindrical containers having the same diameter and two hollow inner cylindrical cores having the same diameter coaxial with the central axis of the outer cylinder are opposed to each other on the opening side. In addition, a noise preventing choke coil having a structure in which an annular winding is housed in an internal space while being combined via an annular gap spacer has been proposed (see, for example, Patent Document 5).

(Avoiding magnetic saturation)
On the other hand, the common mode choke coil has a configuration in which magnetic saturation is difficult because the winding is applied to the core in a direction to cancel the magnetic flux caused by the current of the normal component. However, when noise of a common mode component is applied to the common mode choke coil from the outside, magnetic saturation occurs.
Here, the noise of the common mode component is, for example, as described in JEM-TR177 Guidelines for Square Wave Impulse Noise Immunity Test for Electrical Equipment Used for Industrial Use (Technical Document of the Japan Electrical Manufacturers' Association, Non-Patent Document 1) It is noise.
In order to avoid the noise as described above, a proposal has been made to provide a gap in the common mode choke coil (see, for example, Patent Document 6).

In the proposal in Patent Document 6, as shown in FIGS. 11 and 12, the corresponding ends of the cores 132a and 132b of the two common mode choke coils 131a and 131b are opposed to each other through a minute gap 133a and 133b of about several μm. The DC top characteristics are improved so that the core is not saturated even when a large current flows.
However, since the inductance is reduced by providing the gap, it is necessary to use a plurality of common mode choke coils connected in series.
When it is assumed that noise of several hundred kHz is reduced, it is necessary to obtain an inductance value equivalent to the case where there is no gap, and it is essential to use them in series connection.

(High-frequency coil)
Further, in order to improve the high frequency characteristics of the common mode choke coil, a winding winding method that reduces the stray capacitance between the windings has been proposed.
FIG. 13 is a diagram showing an example of a conventional proposal relating to a winding method of an inductor winding. In FIG. 13, each turn of the winding is numbered. In the example of FIG. 13, the first to tenth turns form a group of coils, and similarly, the eleventh to twentieth turns and the twenty-first turn to the thirty turns form a group of coils. is doing.
By winding so that the windings do not overlap from the beginning of winding to the end of winding, the inter-winding stray capacitance is reduced and high-frequency characteristics are improved (for example, see Non-Patent Document 2).

However, in the common mode choke coil, the high frequency characteristics vary greatly depending on the core material even if the winding structure is the same.
In general, a common mode choke coil exhibits an inductance characteristic (inductivity) in a low frequency region of 100 kHz or less. However, when the frequency is increased, the reactance is changed from inductive to capacitive and is no longer a reactor. Present the situation.
The frequency at which the coil is no longer a reactor is called a “self-resonant frequency”, and this frequency varies depending on the core material.

Examples of ferrite materials are given below. Even for ferrite, the value of the self-resonant frequency varies greatly depending on the type.
In the Mn—Zn-based ferrite, the self-resonance frequency is a little less than 1 MHz, while the initial permeability is several thousand [H / m].
In the Ni—Zn-based ferrite, the self-resonance frequency is over 100 MHz, while the initial permeability is several hundreds [H / m].

  In general, each noise application is different from the relationship between the self-resonance frequency and the initial permeability as described above. That is, common mode chokes using Mn-Zn ferrite (amorphous or finemet if not ferrite) as a core material to prevent conduction noise (noise terminal voltage) subject to regulation at 150 kHz to 30 MHz. A coil is required, and Ni—Zn-based ferrite needs to be applied in order to take measures against radiation noise (radiation electric field strength) that is subject to regulation at 30 MHz to 1 GHz.

JP-A-61-102122 (first page, lower right column, FIG. 5) Japanese Unexamined Patent Publication No. 2000-102263 (paragraph 0070, FIG. 3) JP-A-4-251557 (FIG. 3) JP-A-4-355906 (paragraph 0020, FIGS. 1 and 2) Japanese Utility Model Publication No. 6-13120 (FIG. 2) JP-A-61-126810 (Page 2, lower right column, FIGS. 1 and 2)

JEM-TR177 Guideline for square wave impulse noise immunity test for electrical equipment used in industrial use (Technical data of Japan Electrical Manufacturers' Association) IEEJ Technical Committee on Semiconductor Power Conversion SPC-07-16 Modeling of Noise Generated by 200kHz PWM Inverter and Its Suppression Method

As described above, various proposals for improving the characteristics of the common mode choke coil have already been made.
However, there are a number of problems that still remain regarding the improvement of the characteristics of the common mode choke coil. For example, in order to satisfy both regulations of noise terminal voltage (150 kHz to 30 MHz) and radiation electric field strength (30 MHz to 1 GHz), those using the aforementioned Mn—Zn ferrite core and Ni—Zn ferrite core Two or more common mode choke coils with those using That is, a plurality of types of members must be secured.

In addition, the common mode choke coil of Mn—Zn ferrite has many suppliers and is relatively easily available. However, the common mode choke coil of Ni—Zn ferrite has a limited supplier. There is a problem that it is difficult to obtain and expensive.
In particular, in the case of a power converter (so-called power electronics equipment), it is often difficult to make the noise terminal voltage near several MHz lower than the regulation value rather than the noise terminal voltage in the frequency band of 10 MHz or higher.

This is a frequency band in which resonance due to switching of a semiconductor device is likely to occur, and a frequency band in which a noise reduction effect by a common mode choke coil using Mn—Zn based ferrite as a core material cannot be obtained. That is the cause.
The present invention has been made in view of the above situation, and a common mode choke coil whose frequency characteristics are improved while using an easily available core material, and noise to which such a common mode choke coil is applied. The purpose is to provide a filter.

In order to solve the above-described problems, the present application proposes the following techniques.
(1) A choke coil is formed by winding a winding around a core made of a magnetic material having a practical upper limit frequency of magnetic permeability of about 1 MHz, and a gap is provided in a predetermined portion of a closed magnetic circuit formed by the magnetic material. Thus, the common mode choke coil is characterized in that the gap length of the gap is selected so that the upper limit frequency that functions as an inductance is several MHz or more.
In the common mode choke coil of the above (1), the core is a magnetic substance having a practical upper limit frequency of permeability of about 1 MHz, for example, made of Mn—Zn ferrite, so that it is easy to obtain materials for production. .

Moreover, since the gap whose gap length is selected so that the upper limit frequency functioning as an inductance is several MHz or more is provided in a predetermined part of the closed magnetic circuit formed by the magnetic body of the core, power conversion is particularly performed. It exhibits a self-resonant frequency that is particularly suited to devices.
(2) A noise filter including a plurality of common mode choke coils and a plurality of capacitors, wherein at least one of the plurality of common mode choke coils has a practical upper limit frequency of magnetic permeability of 1 MHz. The upper limit frequency that functions as an inductance becomes several MHz or more by forming a gap in a predetermined part of a closed magnetic circuit formed by winding a winding around cores made of front and rear magnetic bodies. Thus, a noise filter characterized by being a gap core type common mode choke coil in which the gap length of the gap is selected.

The noise filter of the above (2) is a noise filter configured to include a plurality of common mode choke coils and a plurality of capacitors, and at least one of the plurality of common mode choke coils is the above ( Since it is a gap-core type common mode choke coil that is a common mode choke coil of 1), it is easy to obtain materials for manufacturing.
In addition, a gap whose gap length is selected so that the upper limit frequency at which the gap-core common mode choke coil functions as an inductance is several MHz or more is a predetermined part of the closed magnetic circuit formed by the core magnetic body. Since it is provided, it is possible to obtain a self-resonant frequency particularly suitable for a power converter or the like.

(3) The gap core type common mode choke coil is relatively positioned relative to the power supply device among the plurality of common mode choke coils when the noise filter is inserted in a power supply path from the power supply device to the electrical device. The noise filter according to (2), wherein the noise filter is disposed at a position on the circuit of the noise filter that is largely separated.
In the noise filter of (3) above, in particular, in the noise filter of (2), the gap core type common mode choke coil is a plurality of the plurality of the noise filters in the case where the noise filter is inserted in the power supply path from the power supply device to the electric device. The common mode choke coil is disposed at a position on the circuit of the noise filter relatively far away from the power supply device, so that the above-mentioned gap core type common mode choke coil and other common mode choke coils Thus, it is possible to appropriately share the frequency band of noise suppression between the two.

  A common mode choke coil whose frequency characteristics are improved while using an easily available core material and a noise filter to which such a common mode choke coil is applied can be realized.

It is a figure showing the common mode choke coil as an embodiment of the invention. It is a figure for demonstrating the characteristic of the common mode choke coil of FIG. It is a figure for demonstrating the characteristic of the common mode choke coil of FIG. It is a figure showing the common mode choke coil applied to the measurement for obtaining the characteristic of FIG. It is a frequency characteristic figure of an inductance at the time of measuring about a common mode choke coil of composition which a core member does not constitute a closed magnetic circuit. It is a frequency characteristic figure of an inductance at the time of measuring about a common mode choke coil of an air core core. It is a circuit diagram showing the noise filter as one embodiment of the present invention. It is a circuit diagram showing the structural example of the conventional noise filter using a common common mode choke coil and a normal mode choke coil. It is a figure showing the other prior art of a noise filter. It is a figure showing the prior art which aimed at size reduction of a noise filter part. It is a figure showing the further another prior art of a noise filter. It is a figure showing the common mode choke coil applied to the noise filter of FIG. It is a figure which shows an example of the conventional proposal regarding the winding method of the coil | winding of an inductor.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a common mode choke coil as an embodiment of the present invention.
In FIG. 1, a common mode choke coil 1 according to an embodiment of the present invention has an annular core 2 made of a magnetic material having a practical upper limit frequency of permeability of around 1 MHz (more specifically, for example, 500 kHz to 1 MHz). A choke coil is formed by winding a winding 3 around the coil.
The magnetic material having a practical upper limit frequency of permeability of about 1 MHz described above corresponds to, for example, a magnetic material made of Mn—Zn ferrite.
Gap 5a, 5b is provided in a predetermined portion of the closed magnetic path formed by the magnetic bodies 4a, 4b as described above constituting the core 2.

That is, the annular core 2 is configured such that two corresponding magnetic bodies 4a and 4b having a substantially arc-shaped planar projection are joined to the corresponding ends of the two via gaps 5a and 5b.
The winding 3 includes a first winding 31 wound around the magnetic body 4a and a second winding 32 wound around the magnetic body 4b.
The first winding 31 is formed by winding one conductor from the input end 31a to the output end 31b around the magnetic body 4a, and reaching the output end 32b from the input end 32a of the second winding 32. A conductor is wound around the magnetic body 4a.

The above-described gaps 5a and 5b act so as to alleviate the phenomenon that the magnetic material forming the core 2 reaches magnetic saturation in accordance with the strength of the external magnetic field. The gap length of the gap is selected so that the upper limit frequency (self-resonant frequency) at which the mode choke coil 1 functions as an inductance is several MHz or more (more specifically, for example, around 1 MHz to 10 MHz).
In the common mode choke coil 1 as described above, since the core 2 is a magnetic body having a practical upper limit frequency of permeability of about 1 MHz, for example, made of Mn—Zn ferrite, it is easy to obtain materials for production. is there.

In addition, because the gap whose gap length is selected so that the upper limit frequency functioning as an inductance is several MHz or more as described above is provided in a predetermined part of the closed magnetic circuit formed by the core magnetic body. In particular, it exhibits a self-resonant frequency that is particularly suited to power converters and the like.
2 and 3 are diagrams for explaining the characteristics of the common mode choke coil of FIG.
FIG. 2 is a frequency characteristic diagram of the inductance of the common mode choke coil when no gap is provided in order to facilitate understanding of the characteristics of the common mode choke coil of FIG. 1 in comparison with FIG.

On the other hand, FIG. 3 is a frequency characteristic diagram of the inductance of the common mode choke coil when a gap is provided as shown in FIG.
2 and 3 show the characteristics when the common mode choke coil 40 having the shape as shown in FIG. 4 is estimated to exhibit characteristics in accordance with the characteristics of the annular common mode choke coil as shown in FIG. Represents.
The common mode choke coil 40 shown in FIG. 4 has a gap 42a, 42b via a gap 42a, 42b with respect to a coil winding core 41 having both legs of the same width hanging from both ends of a rectangular parallelepiped core member as shown in the figure. The closed magnetic path forming core member 43 is configured to be close to and opposed to each other.

Windings 44 a and 44 b are wound around the above-described legs of the coil winding core 41 independently of each other.
Comparing the characteristics shown in FIGS. 2 and 3 as a result of measuring the above-described common mode choke coil shown in FIG. 4, the following can be understood.
That is, when no gap is provided, the inductance becomes maximum near 550 kHz as shown in FIG. 2, and the inductance decreases rapidly at frequencies higher than that.

On the other hand, when a gap is provided, it becomes a constant value up to around 2 MHz as shown in FIG. 3, and it can be confirmed that an inductance of 100 nH or more is maintained even at a higher frequency.
Further, when no gap is provided, it can be confirmed that although the inductance is large in the low frequency region, the inductance when the gap is provided in the vicinity of about 1.1 MHz becomes larger.
From the above considerations, it can be seen that when the gap is provided in the core material of the common mode choke coil, the inductance in the low frequency region is reduced, but the frequency characteristics are improved when viewed over the entire frequency range to be used.

Based on such knowledge, by adjusting the gap of the common mode choke coil, it becomes possible to set the self-resonance frequency (upper limit frequency indicating inductance characteristics) to several MHz or more, and to reduce the noise around several MHz. It can be effectively suppressed.
Note that the common mode choke coil disclosed in Patent Document 6 described above (referred to as a common coil in Patent Document 6) also discloses that a fine gap is provided in the ferrite core.
However, since Patent Document 6 aims to reduce noise at a relatively low frequency of several hundred kHz or less, a large inductance is essential, and the configuration is different in that it is essential to connect a plurality of common mode choke coils in series. .

On the other hand, the common mode choke coil according to the present embodiment is intended to reduce noise at a relatively high frequency in the vicinity of several MHz. Therefore, a large inductance is not required, and an effect can be obtained even when used alone.
In the case of Patent Document 6, since the inductance is desired to be as large as possible, the general length of the gap length is set to about several μm. However, in the common mode choke coil according to the present embodiment, the frequency to be countered When the value is high, an effect can be obtained even if an extremely large gap is provided.

That is, by adopting a configuration in which a part of the core is deleted, it can function as an inductance up to a higher frequency.
FIG. 5 is a frequency characteristic diagram of inductance when measurement is performed on a common mode choke coil having a configuration in which the closed magnetic circuit forming core member 43 in FIG. 4 is not provided.
As can be seen from FIG. 5, although the inductance becomes smaller as the gap becomes larger, the frequency characteristic can be improved as compared with the common mode choke coil having the gap as shown in FIG.

FIG. 6 is a frequency characteristic diagram of inductance when measurement is performed for a common mode choke coil that does not use a core at all (air core).
As is clear from the comparison of the characteristics of FIG. 5 with FIG. 6, even in an extreme state where the core member 43 for forming a closed magnetic circuit is not used, an inductance of 30 MHz or less does not use the core at all (air core). It is larger than the common mode choke coil and it can be confirmed that the noise countermeasure effect can be obtained.

As described above, in the embodiment of the present invention, by providing a gap in the core made of the magnetic material of the common mode choke coil, the high frequency characteristics can be improved, and the upper limit frequency that functions as the inductance is set to several MHz or more. become.
As a result, it is possible to realize a common mode choke coil and a noise filter using the same to prevent conduction noise in the vicinity of several MHz without using an expensive core material that is difficult to obtain such as Ni—Zn ferrite. .

In the embodiment of the present invention, the gap provided in the predetermined part of the closed magnetic circuit formed of the magnetic material sandwiches the dielectric material in the same manner as a general inductance with a gap (flyback transformer or normal mode choke coil). What is necessary is just to comprise.
FIG. 7 is a circuit diagram showing a noise filter as one embodiment of the present invention. The noise filter 70 in FIG. 7 includes a plurality of common mode choke coils (two in this example, Lc1 and Lc2) and a plurality of capacitors (in this example, across-the-line capacitors Cx1, Cx2, and Line bypass capacitors Cy1, Cy2).

  One of the above-mentioned common mode choke coils (Lc1 in this example) is a core made of a magnetic material having a practical upper limit frequency of about 1 MHz (more specifically, for example, 500 kHz to 1 MHz). An upper limit frequency that functions as an inductance by providing a gap in a predetermined part of a closed magnetic circuit formed by the magnetic material and having a winding is wound over several MHz (more specifically, for example, 1 MHz A gap-core type common mode choke coil in which the gap length of the gap is selected so as to be around 10 MHz.

The gap core type common mode choke coil in this case has the same configuration as the common mode choke coil described in detail with reference to FIGS.
In particular, in the embodiment of FIG. 7, the gap core type common mode choke coil Lc1 is connected to an electric device (output side terminal Ro, connected to the input side terminals Ri, Si, Ei but not shown). From the power source among a plurality of common mode choke coils (in this example, two of Lc1 and Lc2) when the noise filter 70 is inserted in a power feeding path to So and Eo (not shown) The noise filter 70 is arranged at a position on the circuit that is relatively largely separated.

By adopting such an arrangement, for example, the common mode choke coil Lc2 is configured as a type having no gap and functions so as to reduce noise of 1 MHz or less, while a gap core type common mode choke coil Lc1 is used. Can function sufficiently to reduce noise in the several MHz band.
That is, it is possible to appropriately share the frequency band for noise suppression between the above-described gap core type common mode choke coil Lc1 and the other common mode choke coil Lc2.
Although FIG. 7 discloses a configuration including across-the-line capacitors Cx1, Cx2 and line bypass capacitors Cy1, Cy2), the noise filter is not limited to this arrangement.

1, 40, 131a, 131b Common mode choke coil 2, 132a, 132b Core 3, 44a, 44b, 111, 112 Winding 4a, 4b Magnetic body 5a, 5b, 42a, 42b Gap 31 First winding 31a, 32a Input End 31b, 32b Output end 32 Second winding 41 Coil winding core 43 Closed magnetic path forming core member 70, 80 Noise filter 122, 123 Projection

Claims (3)

  A choke coil is formed by winding a winding around a core made of a magnetic material having a practical upper limit frequency of permeability of about 1 MHz, and an inductance is provided by providing a gap in a predetermined part of a closed magnetic circuit formed by the magnetic material. The common mode choke coil is characterized in that the gap length of the gap is selected so that the upper limit frequency that functions as a few MHz or more.   A noise filter including a plurality of common mode choke coils and a plurality of capacitors, wherein at least one of the plurality of common mode choke coils has a magnetic permeability whose practical upper limit frequency is about 1 MHz. The upper limit frequency that functions as an inductance is set to several MHz or more by providing a gap in a predetermined part of a closed magnetic circuit formed by the magnetic body, and winding a winding around a core made of a body. A noise filter characterized by being a gap core type common mode choke coil in which a gap length is selected.   The gap core-type common mode choke coil is relatively far away from the power supply device among the plurality of common mode choke coils when the noise filter is inserted in a power supply path from the power supply device to an electrical device. The noise filter according to claim 2, wherein the noise filter is disposed at a position on the circuit of the noise filter.

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