JP2567363Y2 - Noise prevention choke coil - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise prevention choke coil mainly used as a part of a noise filter circuit which also suppresses harmonics in a power input portion of an electronic device or the like.
In particular, the present invention relates to a choke coil capable of obtaining a large common mode and a large normal mode inductance with one element.

[0002]

2. Description of the Related Art A coil inserted into a power supply input section of an electronic device is most commonly a common mode choke coil used for the purpose of preventing switching noise or the like generated from a switching power supply. In addition, harmonics that have recently become a problem due to voltage distortion in the power system (harmonics refer to frequencies from the second to the 20th order with respect to 50 or 60 Hz, and failures are evident in some devices. Therefore, large inductance (1) is required to suppress international regulations such as IEC-pub-555-2.
A reactor having a normal mode inductance of 10 mH to 10 mH) is used.

[0003] In FIG. 4, a theoretical equation showing the ratio of the n-th harmonic current of the power supply rectifier circuit when there is no reactor is as follows.

[0004] _{i n / i 1 = 2sinnπ /} 2 · (sinnπα · cos πα-ncosn παsin πα) / n (n 2 -1) (παsin πα · cos πα) However, α = (π-2γ) / 2π γ: flow start angle Here, by inserting the reactor 2 of FIG. 4, the flow start angle in the above equation can be advanced, and harmonic current can be suppressed. Also, by inserting the common mode choke coil 1 of FIG. 4, the common mode impedance is increased, and the common mode noise current can be suppressed. When the harmonic current suppressing reactor and the common mode choke shown in FIG. 4 are configured, conventionally, as shown in FIG. 5, windings 11 and 12 are wound in the same phase on a core 13 made of ferrite or amorphous magnetic material or the like. The common mode choke coil 1 constitutes a core 21 made of silicon steel or the like in series with the common mode choke coil 1.
Is connected to a reactor 2 for suppressing harmonics, on which a winding 22 is wound.

[0005]

As described above, conventionally, the common mode choke coil 1 and the reactor 2 for suppressing harmonics are each configured as individual parts independent of each other, and are connected to each other so that the power supply shown in FIG. The circuit was configured. Therefore, three windings, two cores are required, and connection work is required. In addition, since the number of components is increased, the mounting area is increased, and the cost and the size of the device are disadvantageously increased. I was

The present invention eliminates the above-mentioned disadvantages and, when used in a power supply circuit of an electronic device, has a particularly large common mode and normal mode inductor, is small in size, has a small mounting space, is inexpensive and has good common mode noise and noise. It is an object of the present invention to provide a noise prevention choke coil having a harmonic suppression action.

[0007]

A noise prevention choke coil according to the present invention is a magnetic circuit including an outer magnetic path having a magnetic gap and a short-circuit magnetic path for short-circuiting the outer magnetic path. Are provided with two windings each having the same number of turns, and one winding of each of the outer magnetic path and the short-circuit magnetic path is connected to each other, thereby being connected to the two power supply lines and the respective lines of the load. It is a two-line choke coil that constitutes two sets of windings. The windings and connections of each set cancel each other in the normal mode when the direction of the magnetic flux generated in the metatarsal core by each set of windings, and in the common mode. The outer core is in normal mode,
The midfoot core portion and the outer core portion each function as a magnetic path for obtaining a common mode inductor.

[0008]

[Embodiment] To suppress harmonics, as described above, a large normal mode inductance (for example, 1 mH to 10 mH)
And it is necessary not to be saturated by a fundamental wave or a harmonic current having a large amplitude. In order to prevent common mode noise, also consider the increase of line-to-ground leakage current due to the capacitor in the noise filter configuration.
A common mode inductance having an appropriate size (for example, 1 mH to 10 mH) and high frequency characteristics (for example, 10 kHz to 30 MHz) is required.

FIG. 1 is a schematic diagram showing a first embodiment of the present invention. In FIG. 1, a core A and a core B are, for example, silicon steel which is a magnetic material having a relatively high saturation magnetic flux density,
An E-shaped core formed by punching and laminating an amorphous magnetic material, ferrite, or the like, or pressing or sintering powder. The length of the legs at both ends is shorter than the length of the center leg. By arranging the center legs of the core A and the core B abutting each other, a magnetic gap 3 having the same length is formed at both ends. It is formed. Outer magnetic path (outer core) with magnetic gaps 3 along with bridges at both ends
4 is constituted. The center leg constitutes a short-circuit magnetic path (middle foot core) 5 for short-circuiting the outer magnetic path 4.

On the legs 41 and 42 of the outer core located on both sides of the middle foot core, the windings 6 and 7 having the same number of turns are respectively provided with the windings viewed from the respective input ends 61 and 71 or the output ends 62 and 72. They are wound so that the directions are the same as each other. The windings 8 and 9 having the same number of turns are wound around the middle foot core portion so that the winding directions are the same. The winding 6 is connected in series with the winding 9, and the winding 7 is connected in series with the winding 8.
1-62-91-92 and 71-72-81-82 to form two sets of windings. In the two sets of windings, when the normal mode current flows, the respective magnetic fluxes cancel each other out in the middle foot core portion, and when the common mode current flows, the respective magnetic fluxes are added in the middle foot core portion. Each is connected.

When this noise preventing choke coil is inserted in series between two lines between the power supply line and the load, the currents I _N (normal mode currents) including the fundamental wave and the harmonic current are applied to the windings 6 and 7. Generates magnetic fluxes Φ ₁ and Φ ₂ . A part Φ ₁₄ of the magnetic flux Φ ₁ (Φ ₁₄ = Φ ₁₄ −Φ ₂₅ ) is added so that a part Φ ₂₄ of the magnetic flux Φ ₂ (Φ ₂₄ = Φ ₂ −Φ ₂₅ ) passes through the outer core 4 and is added together with Φ _{1 in the} winding 6. Φ ₁ -Φ ₁₅ ) flows together with Φ ₂ through the outer core 4 so as to be added at the winding 7 portion, and the others (Φ ₁₅ and Φ ₂₅ ) flow in the direction in which the metatarsal core 5 cancels each other. In this case, the magnitude of the added magnetic flux (Φ ₁₄ and Φ ₂₄ ) and the magnitude of the canceling magnetic flux (Φ ₁₅ and Φ ₂₅ ) are determined by the length of the magnetic gap at both end legs and the cross-sectional area. , The cross-sectional area of the midfoot core,
It is determined by the relationship between the short circuit path and the magnetic path length of the outer path. Actually, since the outer core 4 is provided with the magnetic gap 3, the magnetic resistance (reluctance) is remarkably large and Φ ₂₄ is substantially 0 and Φ ₁₄ is also substantially 0, that is, Φ ₁ is substantially equal to Φ ₁₅ ; It can be considered that Φ _{2 is} also substantially equal to Φ ₂₅ .

The magnetic fluxes Φ ₃ and Φ ₄ generated by the windings 9 and 8 of the metatarsal core are in opposite directions and have the same magnitude, and are canceled in the metatarsal core. That is, the normal mode inductance of each of the winding in the magnetic flux interlinked [Phi ₁ and winding 7 parts winding 6 parts of the outer core 4 parts by magnetic flux interlinking [Phi ₂ showing the effect on the fundamental wave and the harmonic current It is the sum of the inductances generated in the wire and has nothing to do with the winding of the midfoot core. On the other hand, the current I _c of the common mode noise component
Flow, a part of each of the magnetic flux Φ ₅ due to the current of the common mode noise component flowing through the winding _{6 and} the magnetic flux Φ ₆ due to the current of the common mode noise component flowing through the winding 7 is Φ ₅₅ , Φ ₆₅ As the magnetic flux added to the metatarsal core 5, the magnetic flux generated in the metatarsal core windings 8 and 9, Φ ₇ ,
Φ _{8 is} also a magnetic flux added to Φ ₅₅ , Φ ₆₅ and the midfoot core 5. In the winding 7 of the outer core, a part Φ ₅₄ (= Φ ₅ −Φ ₅₅ ) of the magnetic flux Φ ₅ due to the winding 6 becomes opposite to the direction of Φ ₆ and the winding 6
In the section, a part Φ ₆₄ of the magnetic flux Φ ₆ by the winding 7 (= Φ ₆ −
Φ ₆₅ ) flows in the opposite direction to Φ ₅ . However, since the outer core 4 has the magnetic gap 3, the magnetic resistance is large as in the case of the normal mode noise, Φ ₅₄ is substantially 0, and Φ ₆₄ is substantially 0, that is, Φ ₅ = Φ ₅₅ , Φ ₆ = _Φ may be regarded as _65.

The magnetic fluxes Φ ₇ and Φ ₈ generated by the current of the common mode noise component in the windings 9 and ₈ are Φ ₆₅ and Φ ₅₅
And in the same direction. Some of them are Φ ₇₄ , Φ ₈₄ (Φ _{74
= Φ 7/2, Φ 84} = Φ 8/2) as the outer core winding 6
And flow to 7. Accordingly, the common mode inductance generated in the windings 6 and 9 and the windings 7 and 8 is a magnetic flux linked to the winding 6, Φ ₅ + Φ ₇₄ + Φ ₈₄ , a magnetic flux linked to the winding 9, and Φ ₅₅
The sum of composed inductance in each of the (approximately equal to [Phi ₆₎ ([Phi approximately equal to _{5) + Φ 7 + Φ 8} + Φ 65. Further, the common mode inductance generated in the windings 7 and 8 is the magnetic flux linked to the winding 7, Φ ₆ + Φ ₇₄ + Φ ₈₄ ,
Magnetic flux linked with Φ ₅₅ (approximately Φ ₅ ) + Φ ₇ + Φ
₈ + Φ ₆₅ (substantially equal to Φ ₆ ). Here, since the windings 6 and 7 and the windings 8 and 9 have the same number of turns, Φ ₆ = Φ ₅ and Φ ₇ = Φ _8.
And the common mode inductance of each winding set is equal.

The principle of the present invention will be described in detail with reference to an equivalent circuit of the common mode and normal mode choke coil according to the present invention shown in FIG. FIG. 2A shows a normal mode. The reluctance of the leg including the magnetic gap of the outer core is r ₁ , the reluctance of the metatarsal core is r ₂ , and the reluctance of the bridge between the leg of the outer core and the metatarsal is r ₃ .
Further, the magnetomotive force generated by the windings 6 and 7 is expressed as N ₁ · I _N (N ₁ :
The number of turns, I _N : normal mode current), the magnetomotive force by the windings 8 and 9 is N ₂ · I _N (N ₂ : number of turns), Φ ₁ is the magnetic flux generated by the magnetomotive force in the winding 6, Φ ₁₄ , Φ ₁₅ is Φ
_The magnetic flux diverted from ₁ to the winding 7 and the midfoot core is shown. Similarly, Φ ₂ indicates a magnetic flux generated by the magnetomotive force in the winding 7, and Φ ₂₄ and Φ ₂₅ indicate magnetic flux shunted from Φ ₂ to the winding 6 and the midfoot core, respectively. Φ ₃ and Φ ₄ indicate magnetic fluxes generated by the magnetomotive force in the windings 9 and 8, respectively. Arrows indicate the direction of the magnetic flux. Calculate the normal mode inductance from this relationship (step omitted) L _N = 2N ₁ ² / from the sum of the inductance of the two sets of windings (r ₁ + 2r ₃₎ is obtained.

FIG. 2B shows the state of the magnetic flux in the common mode. Φ ₅ indicates a magnetic flux generated by the magnetomotive force in the winding 6, and Φ ₅₄ and Φ ₅₅ indicate magnetic flux shunted from the Φ ₅ to the winding 7 and the midfoot core, respectively. Similarly, Φ ₆ indicates a magnetic flux generated by the magnetomotive force in the winding 7, and Φ ₆₄ and Φ ₆₅ indicate magnetic fluxes shunted from Φ ₆ to the winding 6 and the midfoot core, respectively. Φ ₈ and Φ ₇ indicate magnetic fluxes generated by the magnetomotive force in the windings 9 and 8, respectively. Φ ₈₄ and Φ ₇₄ are Φ ₈ ,
The magnetic flux shunted from Φ ₇ to the windings 6 and 7 is shown. Detailed calculation process is common mode inductance omitted L _c = the ^{_{(4N 2 2 + N 1 2}} + 4N 1 N 2) / (r 1 + 2r 2 + 2r 3) is obtained. If case of a N ₂ = N _1/2, the above equation becomes ^{_{L c = 4N 1 2 / (}} r 1 + 2r 2 + 2r 3). Since a magnetic gap is provided in the outer magnetic path, the reluctance of the windings 6 and 7 is much larger than the reluctance of the other parts, and can be regarded as r ₁ ? (2r ₂ + 2r ₃ ). A double common mode inductance is obtained. On the other hand, it is about 4.5 times for the ^{_{L c = 9N 1 2 / (}} r 1 + 2r 2 + 2r 3) in the case of N ₁ = N _2.

The required combination of normal mode and common mode inductance is determined by taking into account elements (cross-sectional area, magnetic gap length,...) Of a magnetic circuit for preventing magnetic saturation caused by superimposed fundamental and harmonic currents. Winding 6,
It can be obtained by changing the winding N ₁ of seven parts and the number of turns N ₂ of the windings 7 and 8. As described above, the common-mode noise is generated in such a manner that magnetic fluxes are added to each other in the common mode noise at the five-portion core.
0A), which is a very small current (several tens to several hundreds of mA),
Also, magnetic saturation is unlikely to occur because the magnetic fluxes generated in the normal mode noise cancel each other out, and the cross-sectional area can be made sufficiently smaller than the cross-sectional area of the outer core.

Even when a magnetic circuit similar to that shown in FIG. 1 is formed by using two U-shaped outer cores and one I-shaped core for the midfoot core 5, the same effect can be obtained in terms of inductance. . However, as shown in this embodiment, the outer core 4 and the midfoot core 5 and the magnetic gap are formed as a unitary structure by punching and laminating silicon steel, amorphous magnetic material, or powder pressing and sintering of ferrite. It is more inexpensive to form it with, and the effect on assembly is great.

FIG. 3 is a perspective view showing a second embodiment of the present invention. The outer magnetic path comprises two U-shaped outer cores 4 ', a portion of an I-shaped metatarsal core 5', and a magnetic gap 3 '.
It consists of. The winding method is the same as in the first embodiment.
Since the state of the magnetic flux, the normal mode inductance, and the common mode inductance of the present embodiment are the same as those of the first embodiment, the description will be omitted. The feature of the second embodiment is that the metatarsal core 5 'is completely separated from the outer core 4'
'Means that a core having magnetic properties different from those of the outer core 4' can be used. As described above, a large normal mode inductance and a large common mode inductance are required to suppress harmonics and common mode noise, whereas the outer magnetic path has a magnetic gap to prevent magnetic saturation. Is provided, the effective magnetic permeability is lowered, and it is necessary to perform many windings to obtain a required inductance. For this reason, a large so-called window area for winding is required, and a large choke coil is inevitably obtained. Therefore, in order to make the choke coil as small as possible, it is important how to effectively secure the window area of the winding.

The second embodiment further solves this problem. That is, by increasing the magnetic permeability of the metatarsal core 5 'to be larger than the magnetic permeability of the outer core, the cross-sectional area of the metatarsal core 5' can be further reduced as described in the description of the first embodiment. When the magnetic path has the same size, the length of the legs of the U-shaped core can be increased, and a wide winding window area can be secured accordingly.

[0020]

[Effect of the invention] As described above, according to the invention,
Provide a compact, small mounting space and inexpensive noise prevention choke coil that combines a large common and normal mode inductance that can effectively suppress common mode noise, normal mode noise and harmonics while being a single component. It will make a significant contribution to the realization of small, low-cost electronic devices with more effective harmonic and noise suppression functions.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a first embodiment of a noise preventing choke coil according to the present invention.

FIG. 2 is an electrical equivalent circuit diagram showing a state of a magnetic flux of the first embodiment shown in FIG.

FIG. 3 is a perspective view showing the configuration of a second embodiment of a noise preventing choke coil according to the present invention.

FIG. 4 is a diagram showing an example of a power supply input circuit to an electronic device using a conventional choke coil.

FIG. 5 is a diagram showing a specific connection state of the choke coil shown in FIG. 4;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Conventional common mode choke coil 2 Conventional normal mode choke coil or harmonic suppression reactor 13 Conventional common mode choke coil core 21 Conventional harmonic suppression reactance (core for normal mode choke coil) 3 Magnetic gap 4 Outer magnetic path (Outer core) 5 Short-circuit magnetic path (middle foot core) 6, 7, 8, 9, 11, 12, 22 Winding 61, 71, 81, 91 Winding input terminal 62, 72, 82, 92 Winding output terminal I _N Normal mode current I _c Common mode current

Claims (2)

(57) [Scope of request for utility model registration] 1. An outer magnetic path (outer core) having a magnetic gap and a short-circuit magnetic path (middle foot core) for short-circuiting the outer magnetic path.
Comprising two windings of the same number of turns wound around the outer magnetic path (outer core) and two windings of the same number of turns wound on the short-circuited magnetic path (middle foot core). Then, one set of each of the outer magnetic path and the short-circuited magnetic path is connected to each other to form two sets of windings connected to the two power supply lines and the load lines. It is a choke coil for two lines, and the windings and connections of each set are applied such that the directions of the magnetic fluxes generated in the middle foot core by the respective sets of windings cancel each other in the normal mode, and are added in the common mode. A noise preventing choke coil for both a common mode inductor and a normal mode inductor, wherein a normal mode inductor is formed in an outer core portion, and a common mode inductor is formed in the middle foot core portion and the outer core portion. 2. The noise preventing choke coil according to claim 1, wherein the outer magnetic path is constituted by a magnetic gap, a part of the midfoot core, and the outer core. .