JP3378261B2 - Laminated core and switching power supply using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated magnetic core, and more particularly to a low loss laminated magnetic core effective for increasing the frequency and thinning of a power source.

[0002]

2. Description of the Related Art In recent years, switching power supplies have been widely used as stabilizing power supplies for electronic equipment. In particular, a switching power supply incorporating a magnetic amplifier for output control has been widely used because of its ease of multi-output and low noise. By the way, as the demand for smaller and lighter power sources increases, it is required to further increase the switching frequency.

In response to such a demand, it is required that the transformer for the power supply also be compatible with higher frequencies. Here, the materials currently used for the transformer are
Ferrite occupies most of them, but a transformer using ferrite has a problem that such requirements cannot be sufficiently satisfied. Therefore, use of an amorphous alloy having good high-frequency characteristics among metal materials for the transformer is being studied. However, even if an amorphous alloy that can obtain a low iron loss and a high squareness ratio in the high frequency range is used, the eddy current loss increases in the MHz range, so the practical limit is 200 kHz to 500 kHz. In addition, a transformer using an amorphous alloy easily reaches a saturable state in a low magnetic field because the gradient of the magnetic curve of the amorphous alloy is steep, and when used at a relatively large current, it averages. There was a problem that good characteristics could not be obtained.

On the other hand, from the viewpoint of reducing switching noise caused by higher frequency, a noise reducing element using an amorphous magnetic snubber has begun to be used in place of the conventional CR snubber. Further, also for the choke coil, a component capable of coping with high frequency is also required, and a magnetic core using an amorphous alloy has been put into practical use. However, even in these noise reduction elements and choke coils, the same problems as those of the above-mentioned transformer have arisen as the switching frequency becomes higher. In particular, when the noise reduction element reaches a saturable state in a low magnetic field, the inductance instantly becomes almost zero when used with a relatively large current, so a sufficient noise reduction effect can be obtained. It's gone.

[0005]

As described above, as the demand for smaller size and lighter weight for the stabilized power supply and the like has further increased, the switching frequency is required to be higher than 500 kHz, for example. Further, in order to increase the switching frequency as described above, it is essential to develop a magnetic component having a lower loss. For example, with respect to a power supply that performs high-frequency switching at 500 kHz or more, the conventional transformer has a problem that the loss increases and good characteristics cannot be obtained on average when used with a relatively large current. In high frequency transformers, the reduction of magnetic core loss has become important for improving the efficiency of power supplies. Further, when a conventional magnetic core having magnetic characteristics is used for a magnetic snubber, heat generation and magnetic saturation on the high magnetic field side pose problems, and the noise reduction effect cannot be sufficiently obtained.

On the other hand, there is a limit to the thinning of the power source in the wound magnetic core which is generally used, and there is a demand for a magnetic core which can be made thinner and has low loss. . The present invention has been made in order to address the above-described problems, and achieves low iron loss in a high frequency range and magnetic saturation so that good characteristics can be obtained even in a high magnetic field. It is an object of the present invention to provide a laminated magnetic core that can cope with thinning.

[0007]

The laminated magnetic core of the present invention is a laminated magnetic core formed by laminating a plurality of soft magnetic alloy thin plates having an endless shape to form a closed magnetic circuit. A scratch is provided so as to cross the excitation direction. Also, the present invention
The switching power supply of the above uses the laminated magnetic core of the present invention described above.
It is characterized by having been.

Examples of the material of the soft magnetic alloy thin plate used in the laminated magnetic core of the present invention include amorphous soft magnetic alloys and Fe-based soft magnetic alloys having ultrafine crystal grains.

Fe as the amorphous soft magnetic alloy is Fe.
It is possible to use a group-based or Co-based amorphous alloy, but a Co-based amorphous alloy represented by the following formula (1) is particularly preferably used.

General formula: (Co _1-ab Fe _a M _b ) _100-x (Si _1-c B _c ) _x (1) (where M is V, Cr, Mn, Ni, Cu, At least one element selected from Nb, Mo, Ta, W, etc. is used as a, b, c and
x is 0 ≤ a ≤ 0.10, 0.005 ≤ b ≤ 0.10, 0.15 ≤ c ≤ 0.9
0, 15at% ≤ x ≤ 30at% are shown.)
Here, Fe in the above formula (1) is an element that can make the magnetostriction constant zero by balancing with Co, and its amount is achieved within a range of 0.10 or less as the value of a. More preferable value of a is 0.02 to 0.09, and more preferably 0.03.
~ 0.08. The M element is an element effective for improving thermal stability and magnetic properties, and the substitution amount of this M element is set to a value of b in the range of 0.005 to 0.10. If the value of b is less than 0.005, the above effect cannot be sufficiently obtained, and 0.10
If it exceeds, the Curie temperature becomes too low and the practicality is lowered. The more preferable value of b is 0.01 to 0.09, and further preferably 0.02 to 0.08.

Si and B are essential elements for amorphization, but if the value of c is less than 0.15, it becomes difficult to amorphize, and if it exceeds 0.90, sufficient magnetic properties cannot be obtained. The more preferable value of c is 0.2 to 0.8, and further preferably 0.3 to 0.7. Further, if the total amount of these amorphizing elements is less than 15 at%, it becomes difficult to amorphize, and the range where low loss is obtained becomes extremely narrow, and if it exceeds 30 at%, the Curie temperature becomes too low. The more preferable value of x is 16 at% to 29 at%, and the still more preferable value is 17 at% to 28 at%.

Further, as the Fe-based soft magnetic alloy having ultrafine crystal grains, Fe _100-defgh D _d E _e G _f Si _g B _h (2) (wherein D is selected from Cu and Au) At least one element, E is at least one element selected from IVa group elements, Va group elements and VIa group elements, G is Ga, Ge, M
n, Al, In, Sn, and at least one element selected from platinum group elements, where d, e, f, g, and h are 0.1 at% ≤ d ≤ 3 at% and 0.1 at% ≤ e ≤ 10 at%, respectively. , 0 ≤ f ≤ 5at
%, 12at% ≤ g ≤ 20at%, 5at% ≤ h ≤ 12at%, 20at% ≤
g + h ≦ 25 at% is satisfied), and the alloy structure has ultrafine crystal grains with an average grain size of 50 nm or less. The Fe-based soft magnetic alloy (Fe-based ultrafine crystal alloy) thin plate having such ultrafine crystal grains is formed by forming an amorphous alloy ribbon by a melt quenching method or the like, and then subjecting it to heat treatment at a temperature equal to or higher than the crystallization temperature. , Average particle size
It is obtained by precipitating ultrafine crystal grains of 50 nm or less.

The element D in the above formula (2), namely Cu and Au, is an element effective for enhancing corrosion resistance, preventing coarsening of crystal grains, and improving soft magnetic properties such as iron loss and magnetic permeability. is there. Especially, it is effective for precipitation of bcc phase at low temperature. If the amount of substitution by the D element is too small, the above effect cannot be obtained, and if it is too large, the magnetic properties are deteriorated. Therefore, the content of D element is 0.1at% 〜3a
The t% range is suitable. More preferable range is 0.1 at% to 2a
t%.

Further, IVa group element, Va group element and VIa
The E element selected from the group elements is an element that is effective in making the crystal grain size uniform, reducing magnetostriction, etc., and improving the soft magnetic characteristics and the magnetic characteristics against temperature changes. In addition, the bcc phase is stabilized in a wider temperature range by the combined addition of D element. If this amount is too small, the above effects cannot be obtained, and if it is too large, it becomes difficult to amorphize in the manufacturing process, and the saturation magnetic flux density becomes low. Therefore, the content of E element is 0.1at% ~ 10at%
The range is suitable. The more preferable range is 1 at% to 8 at% .Each element contained in the above-mentioned E element has the above-mentioned effect, and the IVa group element expands the heat treatment condition for obtaining the optimum magnetic characteristics, and the Va group. Elements are effective for improving embrittlement resistance and workability such as cutting, and Group VIa elements are effective for improving corrosion resistance and surface property. Among them, Ta, Nb, W and Mo are preferable because Ta, Nb, W and Mo show remarkable effects in improving soft magnetic properties, and V shows a remarkable effect in improving embrittlement resistance and surface property. G element selected from Ga, Ge, Mn, Al, In, Sn and platinum group elements is an element effective for improving soft magnetic characteristics and corrosion resistance. However, if the content of G element is too high, the saturation magnetic flux density will decrease, so its content is 5 at%.
Below. It is more preferably 3 at% or less. Of the above-mentioned G elements, the platinum group elements are particularly effective for improving the corrosion resistance, and Ge is effective for stabilizing the bcc phase, which is the main phase of fine crystal grains.

Si and B are elements that assist the amorphization of the alloy during production. Further, it is an element which can improve the crystallization temperature and is effective for heat treatment for improving magnetic properties. In particular, Si is Fe, which is the main component of fine crystal grains.
It forms a solid solution in and contributes to the reduction of magnetostriction and the like.

When the Si content is less than 12 at%, it is difficult to improve the soft magnetic properties, and when it exceeds 20 at%, the effect of ultra-quenching becomes small, and relatively coarse crystal grains of μm level are deposited, which is good. Soft magnetic properties cannot be obtained. Furthermore, Si
Is an essential element that constitutes a regular lattice, and for the appearance of this regular lattice, the range of 12 at% to 18 at% is particularly preferable. In addition, the content of B is less than 5at%, or 1
If it exceeds 2 at%, pinholes are likely to be formed in the ribbon and the soft magnetic properties deteriorate, so the B content should be 5 at% or more.
The range is 12at%.

Further, the total amount of amorphizing elements (Si +
If B) is less than 20 at%, it becomes difficult to amorphize,
On the other hand, if it exceeds 25 at%, the magnetic properties are likely to deteriorate when crystallized by heat treatment. Therefore, the total amount of Si and B should be in the range of 20at% to 25at%. Furthermore, it is preferable to set the Si / B ratio to 1 or more in order to obtain excellent soft magnetic characteristics. In particular, by setting the Si amount in the range of 13 at% to 17 at%, the magnetostriction can be made almost zero, the magnetic characteristics are not deteriorated by resin molding, etc., and the initial excellent soft magnetic characteristics can be effectively exhibited. It becomes possible.

The amorphous soft magnetic alloy described above and
Fe-based ultrafine crystal alloys that impair the effects of the present invention even if they contain trace amounts of unavoidable impurities such as those contained in ordinary Fe-based alloys such as O, S, N, and C Not the laminated magnetic core of the present invention, the ribbon of the soft magnetic alloy as described above, endless shape forming a closed magnetic path, for example, ring shape,
After being formed into an elliptical shape, a rectangular shape, a rectangular shape having an opening, or the like, a plurality of the soft magnetic alloy thin plates are laminated. The thickness of the soft magnetic alloy ribbon is 3μ
It is preferably in the range of m to 20 μm. The range is more preferably 3 μm to 15 μm, still more preferably 3 μm.
It is in the range of m to 10 μm. By reducing the thickness of the soft magnetic alloy ribbon, iron loss can be reduced and high frequency characteristics can be improved. A plurality of scratches are provided on the surface of each soft magnetic alloy thin plate so as to cross the excitation direction. This scratch imparts magnetic anisotropy to the soft magnetic alloy thin plate.

The scratch described above may be either a linear groove or a dot groove, and the groove is not limited to a straight line, a wavy line, etc., and is selected according to required characteristics. The line width or point diameter is preferably 20 μm or more and 0.5 mm or less, more preferably about 0.1 mm. The depth is 6.25% or more and 50% of the thickness of the ribbon.
The following is preferable.

Such a scratch is formed so as to cross the magnetic flux flowing in the soft magnetic alloy thin plate. For example, as shown in FIG. 1, a ring-shaped soft magnetic alloy thin plate 1
Then, magnetic flux is formed in the circumferential direction (indicated by arrow A in the figure). When such a soft magnetic alloy thin plate 1 is used, a plurality of scratches 2 are formed radially, for example. In other words, each scratch 2 is formed so as to be substantially perpendicular to the exciting direction. Thus, the maximum magnetic anisotropy can be obtained by radially introducing the scratches 2. However, the scratch forming direction may be within a range of ± 45 degrees from the direction perpendicular to the excitation direction, and magnetic anisotropy corresponding to each forming angle can be obtained.

Further, when the scratches are formed radially on, for example, a ring-shaped soft magnetic alloy thin plate, it is preferable that the respective scratches are formed within the range of 0.1 to 45 degrees of the ring-shaped ribbon. Scratch formation interval is 0.1
Less than the degree, that is, even if the scratches are formed too closely,
Not only can no further effect be obtained, but the flow of magnetic flux is hindered and the saturation magnetic flux density is reduced. Also,
If the scratch formation interval exceeds 45 degrees, that is, if the scratches are formed too coarsely, sufficient magnetic anisotropy cannot be imparted. The more preferable scratch forming interval is in the range of 0.2 to 30 degrees of the ring-shaped ribbon,
More preferably, it is in the range of 0.3 to 20 degrees. When a soft magnetic alloy thin plate having a shape other than the ring shape, such as a square shape having an opening, is used, the scratches are formed on the basis of the above-mentioned formation interval. Also,
These scratches can be formed on one side or both sides of the soft magnetic alloy thin plate.

The laminated magnetic core of the present invention is manufactured, for example, as follows.

First, the amorphous magnetic alloy ribbon or Fe
The amorphous ribbon, which is the base of the base ultrafine crystal alloy ribbon,
It is manufactured by ultra-quenching by a single roll method or a twin roll method. In particular, when producing a thin strip with an extremely thin plate thickness of 12 μm or less and excellent surface properties without pinholes, etc., perform a rapid cooling process under reduced pressure or in an inert atmosphere such as Ar or He. Is preferred. For example, first, a rotary cooling body is made of an Fe-based alloy or a Cu-based alloy, the tip shape of the nozzle is rectangular, and the length of the short side positioned parallel to the circumferential direction of the rotary cooling body is 0.07 mm. ~ 0.13 mm, the distance from the rotary cooling body is 0.05 mm to 0.20 mm, and the rotary speed of the rotary cooling body is 2
While rotating at 0m / sec~ 50m / sec, 1 × 10 under a reduced pressure of not more than atmospheric ^-1 Torr or under an inert atmosphere, injected molten alloy of 0.015kg / cm ² ~0.025kg / cm ² from a nozzle as described above It can be obtained by injecting into the rotary cooling body with pressure.

When using the amorphous soft magnetic alloy ribbon, the amorphous alloy ribbon is formed by etching or mechanical punching so as to have a desired endless shape after the heat treatment or before the heat treatment. After that, the scratches as described above are formed by irradiating the surface of each amorphous alloy thin plate after forming with, for example, a laser or an electron beam. The scratches may be formed before molding. When the scratches are radially introduced, the scratches can be introduced with good reproducibility by forming the radial scratches on the long amorphous soft magnetic alloy ribbon and forming the endless shape with the center thereof as a reference.

When the Fe-based ultrafine crystal alloy ribbon is used, the amorphous ribbon is formed into an endless shape (before the heat treatment). After this, after introducing scratches in the same manner as the amorphous soft magnetic alloy ribbon, or before introducing scratches, at a temperature equal to or higher than the crystallization temperature, for example, at a temperature of about 400 ° C to 700 ° C, for 1 minute to Heat treatment is performed for about 10 hours to precipitate ultrafine crystal grains.

In this way, a plurality of soft magnetic alloy thin plates, which are formed into a desired endless shape and have scratches introduced, are laminated to have a desired thickness and are housed in a case, or at least. The laminated magnetic core of the present invention can be obtained by partially hardening it with an epoxy resin or the like. The heat treatment for removing strain from the amorphous soft magnetic alloy ribbon and the heat treatment for precipitating crystal grains of the Fe-based ultrafine crystal alloy ribbon may be performed after the lamination.

[0027]

In the laminated magnetic core of the present invention, scratches are introduced on the respective surfaces of the soft magnetic alloy thin plates having an endless shape so as to cross the exciting direction. This scratch imparts magnetic anisotropy to the soft magnetic alloy thin plate, which makes it possible to appropriately reduce the squareness ratio. That is, the gradient of the magnetization curve (BH loop) is gentle, and the magnetic field at which the magnetic flux density reaches the saturation state is shifted to the high magnetic field side. Therefore, the magnetic core is prevented from being magnetically saturated on the low magnetic field side, and a magnetic core having good characteristics even on the high magnetic field side can be obtained.

The iron loss of the magnetic core is determined by the eddy current loss and the hysteresis loss, and the eddy current loss is mainly in the high frequency range. This eddy current loss is caused by the movement of the domain wall, but like the soft magnetic alloy thin plate used in the present invention, by introducing scratches, the magnetic stability is improved and the movement of the domain wall can be suppressed. . Therefore, it is possible to suppress the loss in the high frequency range as much as possible. Further, since the stability against heat is increased, the deterioration of the magnetic characteristics due to the temperature rise is suppressed, and the aging characteristics are also improved.

Basically, the laminated magnetic core has an advantage that it can be made thinner more stably than the wound magnetic core. The laminated magnetic core of the present invention having such advantages is effective for secondary side control in a normal PWM (pulse width modulation) circuit of a switching power supply circuit, or for output control of a resonance type power supply or a partial resonance type power supply. . Further, it is also effective for a magnetic snubber, a high frequency transformer, a noise filter, a high frequency compatible choke coil and the like.

[0030]

EXAMPLES Examples of the present invention will be described below.

Examples 1 to 16 Each alloy composition shown in Table 1 was prepared and melted to obtain a mother alloy for producing an amorphous alloy, and an amorphous alloy ribbon was produced by a single roll method under the following conditions. .

That is, the nozzle shape during injection of the molten alloy was a slit shape of 6 mm × 0.12 mm, and the distance between the nozzle and the cooling roll was 0.1 mm. Further, Fe was used as the material of the cooling roll. After placing such a single roll device in the vacuum chamber and evacuating the vacuum chamber to 5 × 10 ^-5 Torr, the injection pressure of 0.02 was applied to the peripheral surface of the cooling roll controlled at the peripheral speed of 40 m / sec. Molten alloy was injected at kg / cm ² and ultra-quenched to obtain long Co-based amorphous alloy ribbons with a width of 5.5 mm. The obtained ribbon was excellent in surface property and had few pinholes and the like. The plate thickness of each ribbon is as shown in Table 1.

Next, the surface of the Co-based amorphous alloy ribbon was radially irradiated with lasers at equal intervals, and scratches were introduced into the ribbons. The scratches introduced were all linear scratches with a width of 20 μm and a depth of about 2 μm. Further, the formation intervals were as shown in Table 1.

Next, the Co-based amorphous alloy ribbon was formed into a ring shape having an outer diameter of 10 mm and an inner diameter of 8 mm by chemical etching with the center of the radial scratch as a reference. Thereafter, the ring-shaped thin plates were subjected to strain relief heat treatment (as shown in Table 1) if necessary, and then laminated to a height of 2 mm to obtain the intended laminated cores.

The iron loss of each laminated magnetic core thus obtained was measured in the high frequency range (1 MHz, 0.1 T). In addition, each laminated magnetic core was incorporated as a main transformer of a switching power supply operating at 1MHz, and the power supply efficiency and the temperature rise of the magnetic core were measured. The results are also shown in Table 1.

Comparative Example 1 in the table is a laminated magnetic core formed in the same shape using MnZn ferrite.
Is a stack of the amorphous alloy ribbons used in Example 1 without introducing scratches.

[0037]

[Table 1]

As is clear from Table 1, the main transformer according to each embodiment is effective in increasing the efficiency of the power supply.

Further, the magnetic core for transformer shown in the above Example 1 and Comparative Example 2 was incorporated as a main transformer of a switching power supply, and the aging characteristics of loss at 120 ° C. were evaluated. The loss was measured under the conditions of 1 MHz and 0.1 T using a magnetic property evaluation system (SY-8617 manufactured by Iwasaki Tsushinki).
The result is shown in FIG. As is clear from FIG. 2, the laminated magnetic core according to the present invention has very little deterioration in magnetic characteristics over time.

Further, an amorphous alloy ribbon ((Co _0.91 Fe _0.05 Cr _0.04 ) ₈₀ (Si _0.5 B with a plate thickness of 6.3 μm and a width of 10 μm)
_0.5 ) ₂₀ ), ring-shaped thin plates with an inner diameter of 8 mm were produced, and the scratch 2 was introduced by laser irradiation while changing the angle θ between the scratch 2 and the excitation direction A as shown in FIG. A plurality of ring-shaped laminated magnetic cores were produced. The scratches 2 were formed at the same interval of 5 degrees.

Losses of these ring-shaped laminated magnetic cores having different angles θ between the scratch 2 and the excitation direction A were measured in the same manner as in Example 1. The result is shown in FIG. As is clear from FIG. 4, the loss is changed by changing the angle θ between the scratch 2 and the excitation direction A.
It can be seen that low loss can be obtained in the high frequency range by setting the angle above 45 degrees.

Examples 17 to 27 Each of the Fe-based alloys shown in Table 2 was once made amorphous under the same conditions as in Example 1 and then formed into a ring shape having the same shape as in Example 1 by chemical etching.
Then, laser was applied to each of the ring-shaped thin plates to introduce scratches. All scratches are wide
It was introduced at 30 μm and 1 μm depth with 0.2 mm intervals. In addition, the formation intervals are as shown in Table 2.

Thereafter, each Fe-based alloy thin plate was heat-treated at the temperature shown in Table 2 for 1 hour to precipitate fine crystal grains. The average crystal grain size obtained from the X-ray diffraction half-width was in the range of 10 nm to 20 nm. These ring-shaped thin plates were laminated to a height of 2 mm to obtain the intended laminated magnetic core.

The core loss of each laminated magnetic core thus obtained in the high frequency range, and the power supply efficiency and the temperature rise of the magnetic core when incorporated as a main transformer of a switching power supply operating at 1 MHz similar to that of Example 1 were measured. The results are also shown in Table 2.

[0045]

[Table 2]

[0046]

As described above, according to the present invention, it is possible to provide a laminated magnetic core capable of reducing iron loss in a high frequency range (to MHz range) and obtaining stable and good characteristics up to a high magnetic field side. It becomes possible to do. Since the laminated magnetic core is basically easy to be made thin, it is possible to stably provide a magnetic core that can cope with, for example, higher frequency and thinner shape of the power supply.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a soft magnetic alloy thin plate used for a laminated magnetic core of the present invention.

FIG. 2 is a diagram showing aging characteristics of a switching power supply using the laminated magnetic core of the present invention in comparison with a conventional example.

FIG. 3 is a view showing another example of a soft magnetic alloy thin plate used for the laminated magnetic core of the present invention.

FIG. 4 is a diagram showing a relationship between a formation angle and a loss with respect to an excitation direction of a scratch in the laminated magnetic core of the present invention.

[Explanation of symbols]

1 ... Ring-shaped soft magnetic alloy thin plate 2 ... scratch A: Excitation direction

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Daiki Yamada 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa Toshiba Yokohama Works (56) References JP-A-59-132111 (JP, A) JP-A-60 -245205 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01F 27/24 H01F 17/00

Claims (7)

(57) [Claims] 1. A laminated magnetic core formed by laminating endless soft magnetic alloy thin plates forming a closed magnetic circuit, wherein scratches are provided on the surface of the soft magnetic alloy thin plates so as to cross the excitation direction. A laminated magnetic core characterized in that. 2. The laminated magnetic core according to claim 1, wherein the soft magnetic alloy thin plate is made of an amorphous magnetic alloy or an Fe-based magnetic alloy having ultrafine crystal grains. 3. The laminated magnetic core according to claim 1 or 2.
In, you wherein scratch is provided with a plurality of
Product layer core. 4. Any one of claims 1 to 3.
In the laminated core according the product layer core you wherein scratch is a linear and / or point-like. 5. The method according to any one of claims 1 to 4.
In the laminated core according the product layer core you wherein scratch line width or Ten径is 20μm or more 0.5mm or less. 6. The method according to any one of claims 1 to 5.
In the laminated core according the depth of the scratches in the thickness of the soft magnetic alloy thin plate 6.
Product layer core shall be the equal to or less than 50% more than 25%. 7. A switching power supply using the laminated magnetic core according to any one of claims 1 to 6.