JP2002164232A - Core for choke coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a core for a choke coil that can improve output current leveling in a small load, using a simple configuration. SOLUTION: A projection 24, integrated with a ferrite core 21, is provided in parallel with a void 23 of ferrite cores 221 and 22 for forming the core for the choke coil, thus achieving a large inductance in the small load, and preventing magnetic saturation in the ferrite cores 21 and 22 at large load times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a choke coil core for a chopper circuit or a rectifier circuit, and more particularly to a choke coil core for a synchronous chopper circuit.

[0002]

2. Description of the Related Art FIG.
As shown in (1), a chopper switching element 1 having one end connected to the voltage input terminal Vin and being interrupted at a predetermined frequency;
Connect the other end of the chopper switching element 1 to the voltage output terminal Vout
A choke coil 2 for smoothing a current by connecting to the other end, and a connection point between the chopper switching element 1 and the choke coil 2 and a constant potential end (ground end) GND connected to operate in reverse to the chopper switching element 1 Operation switching element 3
Is known. As a core for a choke coil of a synchronous chopper circuit, a so-called gap core having a gap for preventing magnetic saturation of the core is usually used as in other chopper circuits.

However, the synchronous chopper circuit described above has a problem that a reverse current flows as shown in FIG. 10 when the on-duty ratio of the chopper switching element 1 is small and the load is low.

In order to prevent the above-mentioned reverse current in the synchronous chopper circuit, it has been proposed to add various complicated reverse current prevention circuits. However, there has been a problem in that the structure becomes complicated and the manufacturing labor increases.

Further, a chopper circuit including the above-mentioned synchronous chopper circuit, a rectifier circuit, and a
In the C-DC converter, a choke coil having a gap core is used for smoothing the output current. In most cases, the choke coil is operated with a much smaller partial load than the full load. It is expected that the output current smoothing performance under a partial load is improved while suppressing the magnetic saturation of the coil core.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a choke coil core capable of improving output current smoothing performance under a low load with a simple configuration.

[0007]

According to a first aspect of the present invention, there is provided a choke coil core having a saturable high permeability magnetic path having a high permeability and a magnetic permeability smaller than the high permeability magnetic path. A magnetic saturation suppressor that is disposed in series in the magnetic path direction with respect to the high-permeability magnetic path section to suppress magnetic saturation of the high-permeability magnetic path section, and is used for a chopper circuit or a rectifier circuit. In a choke coil core for smoothing a change in current of a wound coil, the magnetic saturation suppressing section includes a small magnetic resistance section that is magnetically saturable and has high magnetic permeability, and a non-saturated small magnetic resistance section that is smaller than the small magnetic resistance section. A large magnetic resistance part having a magnetic susceptibility and forming a parallel magnetic path with respect to the small magnetic resistance part.

That is, in this configuration, the saturation suppressing portion of the choke coil core has a small magnetoresistive portion which is magnetically saturable and has a smaller reluctance than the large magnetoresistive portion in parallel with the large magnetoresistive portion. The magnetic flux mainly flows through the small magnetic resistance part. As a result, the choke coil core has a large inductance, and the choke coil core can have excellent current fluctuation suppression performance.

At the time of a large load (large current), the small magnetic resistance part is magnetically saturated, and the magnetic flux mainly flows through the large magnetic resistance part which is not magnetically saturated. As a result, although the inductance of the choke coil core decreases and the current fluctuation suppressing performance decreases, the magnetic fluctuation of the high permeability magnetic path portion of the choke coil core is prevented, and the current fluctuation suppressing performance at a large current is reduced. Can be secured.

According to a second aspect of the present invention, in the choke coil core according to the first aspect, the small magnetic resistance portion has the same magnetic permeability portion as the high magnetic permeability magnetic path portion. The same magnetic permeability portion of the portion can be formed by extending the high magnetic permeability magnetic path portion, and the structure and the number of manufacturing steps can be simplified.

Further, in a preferred embodiment, the small magnetic resistance portion is formed by abutting portions of both end surfaces of a high magnetic permeability magnetic path portion constituting a closed magnetic circuit directly or with a low magnetic permeability material interposed therebetween. You. In this way, the small magneto-resistive part can have a large inductance with a simple structure.
The width of the gap in the magnetic path direction can be simultaneously and accurately determined.

According to a third aspect of the present invention, in the choke coil core according to the first aspect, the large-magnetoresistive portion has a gap width that varies continuously or in multiple steps in a direction perpendicular to the magnetic path direction. It has a characteristic gap.

With this configuration, it is possible to prevent the step change of the core inductance during the transition from the low load state to the high load state, and to reduce problems such as output voltage fluctuation due to the step change of the inductance. Can be improved.

According to a fourth aspect of the present invention, in the choke coil core according to the first or third aspect, the choke coil core of the present invention is used for a choke coil of a synchronous chopper circuit.

In this way, the reverse current of the synchronous chopper circuit at the time of a low load can be favorably prevented without using a reverse current prevention circuit and without requiring an increase in manufacturing labor.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments in which the choke coil core of the present invention is employed in a synchronous chopper circuit will be described in detail with reference to the following examples.

(Embodiment) FIG. 1 shows a synchronous chopper circuit of this embodiment.

The synchronous chopper circuit includes a chopper switching element 1 having one end connected to a voltage input terminal Vin;
Connect the other end of the chopper switching element 1 to the voltage output terminal Vout
A choke coil 2 for smoothing a current by connecting to the other end; a reverse operation switching element 3 for connecting a connection point between the chopper switching element 1 and the choke coil 2 and a ground terminal GND to operate in reverse to the chopper switching element 1; have.

The chopper switching element 1 is intermittently switched at a predetermined frequency, and its on-duty ratio is adjusted according to the load. The reverse operation switching element 3 operates complementarily to the chopper switching element 1.

The choke coil 2 is formed by winding a coil around a required gap core (a choke coil core according to the present invention) forming a closed magnetic circuit.

FIG. 2 shows the cross section of the magnetic path parallel to the gap core including the gap. The gap core is saturable, has high magnetic permeability, and is formed substantially in a ring as a whole by abutting ferrite cores 21 and 22 at two places.
FIG. 2 shows one butted portion.

The ferrite cores 21 and 22 have a gap 23 extending at one end face perpendicular to the magnetic path direction, and the ferrite core 21 is abutted against the end face of the ferrite core 22 adjacent to the gap 23. It has a projection 24.

The projection 24 constitutes a small magnetic resistance part according to the present invention, the gap 23 constitutes a high magnetic resistance part according to the present invention, and the projection 24 and the gap 23 constitute a magnetic saturation suppressing part according to the present invention. The ferrite core 21 and the ferrite core 22 other than the protrusion 24 constitute a high magnetic permeability magnetic path section referred to in the present invention.

Preferably, in a cross section perpendicular to the magnetic path in the magnetic saturation suppressing section, the gap 23 has an area at least three times as large as the projection 24.

A choke coil having a core configured as described above has a large inductance at a low load current and a low load current at a high load current as shown in FIG. 3, but has a magnetic saturation of the ferrite cores 21 and 22. As described above, the reverse current of the synchronous chopper circuit can be satisfactorily prevented at a low load without using a reverse current prevention circuit and without requiring a simple and no increase in manufacturing labor, as already described. .

Furthermore, when the load is low, the current fluctuation suppressing performance is excellent, and when the load is high, the magnetic saturation of the ferrite cores 21 and 22 other than the protrusions 24 is prevented, so that the current fluctuation suppressing performance of the choke coil can be secured. .

Further, in this embodiment, the small magnetic resistance portion of the magnetic saturation suppressing portion has the protrusion 2 protruding from the ferrite core 21.
4, the manufacturing is simple, and the width of the gap 23 forming the large magnetoresistive portion can be accurately determined.

(Modification) FIG. 4 shows a modification of the above embodiment.
Shown in

In this modification, the ferrite core 21 is formed into a U-shape, the ferrite core 22 is formed into an I-shape, and the two are butted together to form a gap core (choke coil core). 21 are formed integrally. The effect is almost the same as that of the first embodiment. 26
Is a coil.

FIG. 5 shows another modification.

In this modification, 21 'and 22' are ferrite cores 2 and 23 'are voids, 24' is a protrusion 26 'and a coil, and the ferrite core 21 shown in FIG. A projection 24 'is provided at the tip of the central column.

FIG. 6 shows another modification.

In this modification, a non-magnetic material 25 is interposed in the gap 23 shown in FIG. The air gap 23 forming the large magnetic resistance portion may be a magnetic air gap, and a non-magnetic material (low magnetic permeability material) may be freely provided. When a non-magnetic material is interposed in the gap 23, a thin gap can be arranged between the protrusion 24 and the ferrite core 23.

FIG. 7 shows another modification.

In this modification, the gap 23 'shown in FIG.
And a non-magnetic material 25 'is interposed therebetween.

As another modification, the protrusions 24, 2
A thin non-magnetic material may be interposed between the 4 ′ and the ferrite cores 23, 23 ′ to make abutment.

FIG. 8 shows a modification of FIG.

In this embodiment, the gap width of the gap 23 shown in FIG. 2 is continuously changed in the direction perpendicular to the magnetic path.

In this way, as shown in FIG. 9, when the current is equal to or less than the predetermined current, the inductor has a large inductance as in FIG.
Thereafter, it is possible to realize a choke coil core in which the inductance continuously decreases as the current increases.

This makes it possible to prevent a step change in the inductance of the core at the time of a transition from a low load state to a high load state, and to reduce problems such as output voltage fluctuation due to the step change in the inductance. Can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a synchronous chopper circuit using a choke coil core of the present invention.

FIG. 2 is a sectional view in the magnetic path direction of a gap portion of a choke coil core used in the choke coil of FIG. 1;

FIG. 3 is a characteristic diagram showing a current-inductance relationship of a choke coil using the choke coil core of FIG. 2;

FIG. 4 is a side view of a choke coil core according to a modified embodiment.

FIG. 5 is a side view of a choke coil core according to a modified embodiment.

FIG. 6 is a side view of a choke coil core according to a modified embodiment.

FIG. 7 is a side view of a choke coil core according to a modified embodiment.

FIG. 8 is a sectional view in the magnetic path direction of a gap portion of a choke coil core according to a modified embodiment.

9 is a characteristic diagram showing a current-inductance relationship of a choke coil using the choke coil core of FIG.

FIG. 10 is a circuit diagram showing a synchronous chopper circuit using a conventional choke coil core.

[Explanation of symbols]

 Reference Signs List 21 ferrite core (high permeability magnetic path portion) 22 ferrite core (high permeability magnetic path portion) 23 air gap (large magnetic resistance portion, magnetic saturation suppressing portion) 24 protrusion (small magnetic resistance portion, magnetic saturation suppressing portion)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02M 7/21 H02M 7/21 A (72) Inventor Hiroshi Matsumae 1-1-1 Showa-cho, Kariya-shi, Aichi Stock Inside Denso Corporation (72) Inventor Toshihiko Sugiura 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Inventor Shigeo Hirashima 1-1-1, Showa-cho, Kariya-shi, Aichi F-term (Reference) 5E070 AA01 AA19 AB01 BA08 BA15 5H006 BB08 CA02 CB07 CC08 DA04 5H730 AS01 BB13 BB57 DD04 EE13 FG05 ZZ17

Claims (4)

[Claims] 1. A high-permeability magnetic path portion which is saturable and has a high magnetic permeability, and has a magnetic permeability smaller than that of the high-permeability magnetic path portion and extends in a magnetic path direction with respect to the high-permeability magnetic path portion. A magnetic saturation suppressing section arranged in series to suppress magnetic saturation of the high magnetic permeability magnetic path section; and a choke coil core used for a chopper circuit or a rectifier circuit for smoothing a current change of a wound coil. In the magnetic saturation suppressing section, a magnetically saturable small magnetic resistance section having a high magnetic permeability and a non-saturated small magnetic resistance section having a smaller magnetic permeability than the small magnetic resistance section are provided in parallel with the small magnetic resistance section. A choke coil core comprising: a large magnetic resistance portion forming a magnetic path. 2. The choke coil core according to claim 1, wherein said small magnetic resistance portion has the same magnetic permeability portion as said high magnetic permeability magnetic path portion. 3. The choke coil core according to claim 1, wherein the large magnetoresistive portion has a magnetic gap portion having a gap width different continuously or in multiple stages in a direction perpendicular to the magnetic path direction. Choke coil core. 4. The choke coil core according to claim 1, wherein the choke coil core is used for a choke coil of a synchronous chopper circuit.