JP2007081239A - Magnetic device and switching power source using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic device excellent in high frequency characteristics and a switching power source using it. <P>SOLUTION: The magnetic device is a wound body of a laminate provided with a ribbon-like magnetic body layer and a conductor layer arranged in parallel with the longitudinal direction. Also, it is preferable that the magnetization easy direction of the ribbon-like magnetic body layer matches with an outline conductor layer longitudinal direction. Also, the gap of the wound body may be filled with the mixture of a magnetic material and a resin. Then, an amorphous ribbon is preferable for the ribbon-like magnetic body layer. Such a magnetic device is suitable for an inductor, a noise filter and various kinds of transformers. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inductor, a noise filter, a magnetic device suitable for various transformers, and a switching power supply using the magnetic device.

The switching power supply circuit is capable of high-efficiency and high-current output, and the output voltage can be continuously varied. Therefore, it is important to realize low power consumption of portable devices in recent years. However, since the switching power supply circuit is turned on and off by a clock, a large switching noise is generated. On the other hand, the noise has become non-negligible due to the low voltage accompanying the low power consumption of LSI. In addition, since the switching frequency is increased, a noise filter capable of handling high-current noise at a higher frequency than before has been required.
In addition, high frequency, large current, and low loss are also required for switching power supply inductors. An inductor using ferrite is mainly used at several MHz, but since ferrite has a low saturation magnetic flux, magnetic saturation occurs at a large current. Moreover, since the coercive force is larger than amorphous, sendust, etc., the loss has increased. On the other hand, an inductor using an amorphous ribbon has a problem in that the magnetic permeability suddenly decreases and the inductance deteriorates in the MHz band.
In addition, noise filters mounted on portable devices are also required to be downsized. Japanese Patent Laid-Open No. 5-291865 (Patent Document 1) proposes a noise filter in which a coil is wound. This has a structure in which thin conductive wires whose surfaces are covered with an insulating material are overlapped and wound in a spiral shape, and two coils each have an inductance component and both are opposed to each other via an insulating material. Having a component forms a distributed constant filter. However, there is a limit to downsizing the self-inductance and mutual inductance because large values cannot be obtained. Japanese Laid-Open Patent Publication No. 7-122460 (Patent Document 2) proposes an LC noise filter in which strip-shaped conductors are laminated and wound via a dielectric sheet. However, self-inductance and mutual inductance have large values. Since it was not obtained, there was a limit to its miniaturization.
Since the noise filters of Patent Document 1 and Patent Document 2 both use nonmagnetic metal materials, large values of both the self-inductance and the mutual inductance cannot be obtained. In order to cope with such a problem, JP 2004-358847 A (Patent Document 3) discloses a magnetic core material in which amorphous magnetic ribbons and resin films are alternately laminated.

JP-A-5-291865 JP-A-7-122460 JP 2004-358847 A JP-A-8-55736

However, since the magnetic core material of Patent Document 3 uses an amorphous magnetic ribbon, the inductance value increased in the region of 10 MHz or less, and the frequency characteristics were not satisfactory in the higher frequency region. . In other words, the phenomenon that the inductance value suddenly decreases when used in a higher frequency range has occurred.
In view of such a situation, as a result of earnest research, the present inventor has found that a magnetic device having excellent high-frequency characteristics can be provided by devising a winding method of the ribbon-like magnetic layer and the conductor layer.
Further, the conventional magnetic device is designed for the transformer only for the transformer and the noise filter only for the noise filter, and there is no compatibility between the magnetic devices. For this reason, a device having a complicated circuit configuration such as a recent switching power supply cannot be said to have good assemblability because parts (magnetic devices) must be prepared for each.

The magnetic device of the present invention is a wound body of a laminate having a ribbon-like magnetic layer and a conductor layer arranged in parallel with the longitudinal direction thereof. Further, it is preferable that the direction of easy magnetization of the ribbon-like magnetic layer is substantially coincident with the longitudinal direction of the conductor layer. Moreover, it is preferable to fill the space | gap of the said winding body with the mixture of a magnetic material and resin. The ribbon-like magnetic layer is preferably a mixture of a magnetic material and a resin. The conductor layer is preferably composed of a plurality of conductors. Moreover, it is preferable to interpose an insulating film between the ribbon-like magnetic layer and the conductor layer. The ribbon-like magnetic layer is preferably an amorphous ribbon.
The magnetic device of the present invention can be applied to various fields such as an inductor, a noise filter, and a transformer. In particular, since the same shape can be applied to various magnetic devices such as an inductor and a noise filter, compatibility between the magnetic devices is established, so that versatility is high. Moreover, it is preferable that the ribbon-like magnetic layer has a structure that is grounded. Such a magnetic device is suitable for a switching power supply.

The magnetic device of the present invention is excellent in high frequency characteristics, particularly high frequency characteristics of 1 MHz or more, and hardly magnetically saturated. Therefore, it is suitable for large current devices. Moreover, a switching power supply using the same has good high frequency characteristics.

The magnetic device of the present invention is a wound body of a laminate having a ribbon-like magnetic layer and a conductor layer arranged in parallel with the longitudinal direction thereof.
First, the ribbon-like magnetic layer is made of a magnetic material such as ferrite, sendust, amorphous (amorphous), or a magnetic material having fine crystals, which is solidified with a resin, a ribbon obtained by a rapid solidification method, an insulating film, etc. A magnetic film formed by vapor deposition such as sputtering or vapor deposition or plating may be used.
Examples of amorphous materials include Co-based amorphous materials and Fe-based amorphous materials. Magnetic materials having fine crystals include Fe-based magnetic materials having fine crystals of 300 angstroms (0.03 μm) or less (see Patent Document 4). Examples of the magnetic film formed by vapor deposition or plating include soft magnetic films such as CoZrNb, CoZrNbTa, FeBN, CoFeB-SiO, CoFeAlO, CoAlPdO, CoFeMn, CoFeN, and FeNi.

Further, the thickness of the ribbon-like magnetic layer is preferably 100 μm or less. In terms of magnetic characteristics, there is no problem even if the thickness exceeds 100 μm, but considering the winding, the thickness of the magnetic layer is preferably 100 μm or less, and more preferably 50 μm or less. Further, the lower limit of the thickness of the ribbon-like magnetic layer is preferably 0.1 μm or more. If the thickness is less than 0.1 μm, the magnetic layer may be thin and sufficient magnetic properties may not be obtained. Moreover, it is preferable that the thickness of the thin magnetic layer is 0.1 μm or more because manufacturing management becomes complicated. Considering the thickness of such a magnetic layer, an amorphous material capable of obtaining a ribbon (ribbon) by a rapid solidification method is a preferable material. In particular, if it is Co-based amorphous, the magnetic properties are also good. Further, the ribbon-like magnetic layer may have material magnetic anisotropy (crystal magnetic anisotropy, induced magnetic anisotropy, etc.) superimposed in the longitudinal direction.
Next, it has a conductor layer arrange | positioned in parallel with the longitudinal direction of a ribbon-like magnetic body layer. The conductor layer is preferably a metal material such as Cu or Al. The form of the conductor layer may be a ribbon shape (thin ribbon shape) or a thin film such as vapor phase growth or plating. The thickness of the conductor layer is preferably 100 μm or less like the ribbon-like magnetic layer. Since it is not the type which winds like the past, the volume of a magnetic device can be made small and size reduction is attained.
The ribbon-like magnetic layer and the conductor layer are arranged in parallel. This “arranged in parallel” may be substantially parallel, and it is desirable that the angle between the two is a low angle within 20 °. That is, it is important that the longitudinal direction (magnetization easy axis) of the ribbon-like magnetic layer and the longitudinal direction of the conductor layer are substantially parallel. In addition, the angle between the ribbon-like magnetic layer and the conductor layer being within 20 ° is referred to as that the direction of easy magnetization of the ribbon-like magnetic layer substantially coincides with the longitudinal direction of the conductor layer.
A laminated body in which such ribbon-like magnetic body layers and conductor layers are arranged in parallel in the longitudinal direction is formed, and further wound to form a magnetic device. The number of windings is arbitrary. Moreover, the shape after winding is not specifically limited, such as a circle, an ellipse, and a rectangle.

In addition, when the ribbon-like magnetic layer is made of a powder of magnetic material such as ferrite or amorphous, which is solidified with a resin, that is, if the ribbon-like magnetic layer has an insulating property, a conductor layer is directly formed thereon. It may be provided. On the other hand, when the ribbon-like magnetic layer is conductive, such as amorphous, it is necessary to provide an insulating layer between the magnetic layer and the conductor layer. Examples of the insulating layer include an insulating resin film and an inorganic insulating layer such as an oxide. In the case where a thin magnetic layer and a conductor layer are used, the insulating layer is preferably a resin film. If it is a ribbon-like magnetic layer, a ribbon-like conductor layer, and a resin film, all three layers are film-like and can be produced by a winding method using a roll, so that mass productivity is improved.
An example of a magnetic device using a ribbon-like magnetic layer, a ribbon-like conductor layer, and a resin film is shown in FIG. In the figure, 1 is a magnetic device, 2 is a ribbon-like magnetic layer, 3 is a conductor layer, 4 is a resin film, and 5 is a terminal. In the figure, the resin film 4 is provided on both surfaces of the magnetic layer 2, but at least one layer may be provided between the conductor layer 3 and the magnetic layer 2. Moreover, if the resin film 4 is provided on both surfaces of the magnetic layer 2, the outermost magnetic layer 2 after winding is not exposed, and the outermost resin film serves as a protective layer. Terminals 5 are provided at both ends of the conductor layer 3. The terminal 5 may be formed by bending the conductor layer 3 or may be provided with a terminal member separately. The resin film 4 may be a magnetic sheet mixed with magnetic powder.

Further, a plurality of conductor layers may be provided (see FIG. 7). Even when a plurality of conductor layers are provided, each conductor layer is arranged in parallel with the longitudinal direction of the ribbon-like magnetic layer. Further, the plurality of conductor layers may have overlapping portions. Further, a plurality of transformers can be realized by using a plurality of conductor layers as shown in FIG.
The ribbon-like magnetic layer, the insulating layer, and the conductor layer may each be a single layer, or may be a wound body after a plurality of layers are stacked. In the above description, the ribbon-like magnetic layer is sandwiched between insulating layers (resin films). For example, ribbon-like magnetic layer / insulating layer / conductor layer / insulating layer / ribbon-like magnetic layer / insulating layer. Thus, after constituting a laminated body in which a plurality of layers are provided, a wound body may be used (see FIG. 8).
Further, in the wound body, it is preferable to fill a gap (gap) in each layer with a mixture of magnetic powder and resin. When the mixture at the time of filling is pasty, it is easy to pack in the gap. When such a mixture is filled, the inductance value can be improved. The magnetic powder is preferably a material used for the ribbon-like magnetic layer described above. In particular, it is preferably the same as that used for the ribbon-like magnetic layer. The resin is preferably a silicone resin, an epoxy resin, a polyimide resin, or the like.
In the magnetic device of the present invention as described above, since the current direction coincides with the easy magnetization direction, the magnetic material is magnetized in the hard axis direction, and magnetization reversal is performed in the magnetization rotation mode. For this reason, the frequency characteristics are greatly improved, and a stable inductance can be obtained at several MHz.
The magnetic device of the present invention may have a structure in which the ribbon-like magnetic layer is grounded. The grounded structure indicates a state where the ribbon-like magnetic layer and the ground electrode 6 are electrically connected when the ground electrode 6 is provided separately from the terminal 5 as shown in FIG. There may be at least one ground electrode 6. Further, when a grounded structure can be achieved, the ground electrode 6 and the ribbon-shaped magnetic layer 2 can be easily connected by setting the relation of the width of the ribbon-shaped magnetic layer> the width of the insulating layer. Also, the ribbon-like magnetic layer that has been exposed is filled with a mixture of conductive powder and resin (conductive paste) so that the ribbon-like magnetic layer has the same potential (so as not to cause a phase difference). It is preferable to have the property. Examples of the conductive powder include metal powders such as copper and silver. In addition, when the conductive paste is filled, the conductor layer 3 and the conductive paste are prevented from conducting.
Thus, since the magnetic device of the present invention is excellent in high frequency characteristics, it is suitable for various magnetic devices such as inductors, noise filters, and transformers. Further, since it is not necessary to wind the toroidal core unlike the conventional magnetic device, the volume can be reduced.
Such a magnetic device is effective for a switching power supply and is suitable for a switching power supply used in a high frequency region of 1 MHz or higher.

Example 1
A melt quench ribbon of Co ₇₄ Fe ₄ Si ₈ B ₁₄ (at%) amorphous alloy having a width of 10 mm, a length of 600 mm, and a thickness of 25 μm was used as the magnetic layer. The conductor layer was a copper foil slit material having a width of 2 mm × length of 600 mm (+ terminal portion) × thickness of 30 μm, and a polyimide film having a width of 10 mm × length of 600 mm × thickness of 25 μm was used for the insulating layer. These are laminated as shown in FIG. 4 to produce a wound body (amorphous ribbon and a conductor arranged in parallel to the longitudinal direction and wound through an insulating layer), whereby the inductor shown in FIG. Produced. At this time, the longitudinal direction of the magnetic layer was made to coincide with the easy magnetization direction.
The frequency characteristics of the inductor according to Example 1 were examined. The result is shown in FIG. As is apparent from FIG. 2, it can be seen that in a high frequency region of 1 MHz or more, the inductance value does not decrease and has excellent high frequency characteristics.
Further, the change in the inductance value when the DC superimposed current value (A) was changed while being fixed at 100 kHz and the excitation AC voltage 0.1 V was examined. The result is shown in FIG. As can be seen from FIG. 3, high inductance can be maintained even with a large current.
Thus, since the current direction and the easy magnetization direction coincide with each other, the magnetic material is magnetized in the hard magnetization axis direction, and magnetization reversal is performed in the magnetization rotation mode. Further, the easy axis of magnetization tends to be in the longitudinal direction due to the shape magnetic anisotropy, and the magnetic anisotropy (crystal magnetic anisotropy, induced magnetic anisotropy, etc.) of the material may be superimposed in that direction.

(Comparative Example 1)
Using the same material as in Example 1, a conductor layer was wound so as to be perpendicular to the longitudinal direction of the amorphous ribbon to produce an inductor according to Comparative Example 1 having a diameter of 12 mm. FIG. 5 shows the frequency characteristics of the inductance with respect to the inductor according to Comparative Example 1. From FIG. 5, the inductance decreases rapidly with increasing frequency. This is considered because magnetization reversal is performed by domain wall movement.
(Example 2)
Using the same material as in Example 1, the inductance value when the angle of the conductor layer was changed with respect to the longitudinal direction of the amorphous ribbon was examined. The result is shown in FIG. As can be seen from FIG. 6, when the angle between the longitudinal direction of the amorphous ribbon and the conductor layer exceeds 20 °, a decrease in the inductance value in the high frequency band was confirmed. Therefore, the angle between the longitudinal direction of the amorphous ribbon and the conductor layer is preferably 20 ° or less. In other words, the direction of easy magnetization and the longitudinal direction of the conductor need not be completely coincident with each other because the magnetization reversal may be realized mainly by the magnetization rotation.
(Examples 3 to 5)
Next, using the inductor of Example 1, the gap was filled with a mixture of magnetic powder and resin (magnetic paste) in Example 3, and a magnetic powder and resin mixture sheet (magnetic sheet) was used as the insulating layer. Example 5 was provided with both the configurations of Example 3 and Example 4 and Example 4. The inductance value at 100 kHz of the inductor according to each example was examined. The results are shown in Table 1.
Sendust powder (average particle size of 10 μm or less) was used as the magnetic powder, and silicone resin was used as the resin.

As can be seen from Table 1, when the magnetic paste or the magnetic sheet is used, the magnetic efficiency is improved and the inductance value is improved. In addition, the magnetic flux density inside the conductor is reduced, eddy current loss inside the conductor is reduced, and thus device loss can be suppressed.
(Examples 6 to 8)
Next, the example used as a noise filter is shown. First, Example 6 was obtained by using a wound body having the same shape as Example 1.
Further, as shown in FIG. 7, Example 7 is one in which two conductors are placed in parallel.
A melt quench ribbon of Co ₇₄ Fe ₄ Si ₈ B ₁₄ (at%) amorphous alloy having a width of 10 mm, a length of 600 mm, and a thickness of 25 μm was used as the magnetic layer. The conductor layer is a polyimide film (thickness 25 μm) in which a Cu foil (thickness 18 μm) is bonded on one side having a width of 9.5 mm, the conductor width 2 mm, the conductor spacing 1 mm, and the distance from each tape end to the conductor is 2, 2 A polyimide film having a thickness of 9.5 mm, a length of 600 mm, and a thickness of 25 μm was used for the insulating layer. The internal terminal portion was taken out using a vinyl tube having an inner diameter of 6 mm and an outer diameter of 8 mm as shown in FIG. 9 and wound as shown in FIG. 1 to produce the inductor shown in FIG. 9 having a diameter of 15 mm. At this time, the longitudinal direction of the magnetic layer was made to coincide with the easy magnetization direction. Further, as shown in FIG. 10, a conductive paste was embedded between the amorphous ribbons, and the amorphous ribbon was used as the ground electrode 6. The ground electrode 6 is not a terminal for connecting to an external circuit like the terminal 5 but functions as a ground electrode.
The frequency characteristics of the attenuation rate for the noise filters according to Examples 6 and 7 were examined. The results are shown in FIG. 11 for Example 6 and FIG. 12 for Example 7.
As can be seen from each figure, the current direction and the easy magnetization direction of each filter coincide with each other, so that the magnetic material is magnetized in the hard axis direction, and magnetization reversal is performed in the magnetization rotation mode. For this reason, the frequency characteristics are greatly improved. Thus, the magnetic device according to the present embodiment is highly versatile because it can be applied to various fields such as inductors and noise filters.
As shown in FIG. 11, the attenuation rate of the transmitted signal is increased in the high frequency band, and an effective low pass filter is formed.
FIG. 12 shows the transmission signal attenuation rate (SCC21) of the differential mode signal and the transmission signal attenuation rate (SDD21) of the common mode signal. In a wide region of 10 M to several GHz, a large attenuation rate with respect to the common mode signal is shown, indicating the attenuation rate. As shown in FIG. 8 in Example 7 (FIG. 12), the two conductors are opposed to each other through an insulating layer, and the two conductors are sandwiched between magnetic layers, so that a large self-inductance, mutual inductance, and This is because a capacitor component can be obtained.
Further, as shown in FIG. 8 as Example 8, a laminate of (insulating layer / magnetic layer / insulating layer / conductor layer / insulating layer / conductor layer) is wound so that the two conductors are opposed to each other through the insulating layer. As a result of experiments on the samples, almost the same results as in Example 7 were obtained.

Schematic diagram showing an example of the magnetic device of the present invention The figure which shows an example of the frequency characteristic of the inductance value of an Example (inductor) The figure which shows an example of the direct current superposition characteristic of an Example (inductor) The schematic diagram which shows an example of the lamination | stacking form of each layer of this invention The figure which shows the frequency characteristic of the inductance of the comparative example (conventional inductor) The figure which shows an example of the relationship between the angle characteristic made by the easy magnetization direction and the ribbon longitudinal direction, and the frequency characteristic of the inductance Schematic diagram showing an example of a laminated form when a plurality of conductor layers are arranged The schematic diagram which shows another example of the lamination | stacking form when arrange | positioning a several conductor layer The figure which shows an example of how to take out an electrode The figure which shows an example which provided the ground electrode The figure which shows the frequency characteristic of the attenuation factor of Example 6. The figure which shows the frequency characteristic of the attenuation factor of Example 7

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Magnetic device 2 ... Ribbon-like magnetic body layer 3 ... Conductor layer 4 ... Insulating layer 5 ... Terminal part 6 ... Ground electrode

Claims (10)

A magnetic device comprising a laminated body having a ribbon-like magnetic body layer and a conductor layer arranged in parallel to the longitudinal direction thereof. 2. The magnetic device according to claim 1, wherein the direction of easy magnetization of the ribbon-like magnetic material layer substantially coincides with the longitudinal direction of the conductor layer. 3. The magnetic device according to claim 1, wherein a gap of the wound body is filled with a mixture of a magnetic material and a resin. The magnetic device according to any one of claims 1 to 3, wherein the ribbon-like magnetic layer is a mixture of a magnetic material and a resin. The magnetic device according to any one of claims 1 to 4, wherein the conductor layer includes a plurality of conductors. The magnetic device according to claim 1, wherein an insulating film is interposed between the ribbon-like magnetic layer and the conductor layer. The magnetic device according to any one of claims 1 to 6, wherein the ribbon-like magnetic layer is an amorphous ribbon. The magnetic device according to any one of claims 1 to 7, further comprising a structure in which the ribbon-like magnetic material layer is grounded. The magnetic device according to claim 1, wherein the magnetic device is an inductor, a noise filter, or a transformer. A switching power supply comprising the magnetic device according to claim 1.

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