JP3471896B2 - Ferrite and ferrite core for power supply - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is particularly applicable to 10 to 500 kHz.
The present invention relates to a manganese-zinc-based ferrite for a power source core such as a power source transformer that operates at a high frequency of about 100 ° C., and a power source core made of this ferrite.

[0002]

2. Description of the Related Art Manganese-zinc-based ferrite is widely used as a core material for coils and transformers of various communication equipments, consumer equipments, etc., but recently, there is a tendency that a high frequency power source is used. Performance as a core material meeting the purpose has been demanded. Especially for switching power supplies, it is necessary to have a transformer that can be used with a power of several tens of watts in the high frequency range of 10 to 500 kHz. In addition to this, cores for various transformers for motor drive, signal amplification, oscillation, etc. are also required. ing. Until now, manganese-zinc-based low-loss ferrite has been used for transformer cores, but in the high-frequency range of about 10 to 500 kHz, power loss called core loss is large, and improvement in terms of core loss is required. There are various proposals for this purpose.

As such a proposal, oxides of Si and Ca are added, and tetravalent metal oxides such as Sn, Ti and Zr and pentavalent metal oxides such as V, Nb and Ta are further added. There is something to add. Examples of the addition of tetravalent or pentavalent metal oxides alone or in combination are as follows: JP-A-46-2880, JP-A-48-72696, and JP-A-60-26240.
4, gazette 61-108109, gazette 61-25.
2609, 61-252611, 63.
-222018, JP-A-1-129403, JP-A-2-54902, JP-A-3-141611, JP-A-3-163804, JP-A-3-223119, JP-A-3-248403, JP-A-3-248403. -248404
No. 3,3,485,405, and No. 3,254,410.
No. 3, gazette 4-55362, gazette 4-15000.
7, gazette 5-198416 gazette, and gazette 5-2670.
No. 40, etc.

However, these are high frequencies, for example 100
At kHz and 100 ° C., the difference ΔB = Bm−Br between the maximum magnetic flux density Bm and the residual magnetic flux density Br is increased, the power loss at high frequency is decreased, and the effective magnetic permeability (μa ) Cannot be raised. Therefore, when these conventional ferrites are used, it is difficult to reduce the size of the transformer.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a ferrite having a small power loss, a large ΔB = Bm-Br at a high frequency and a good μa-B characteristic, and a power supply using the ferrite. Is to provide the core.

[0006]

These objects are achieved by the present invention described in (1) to (11) below. (1) Manganese oxide, zinc oxide, and iron oxide are contained as main components, and silicon oxide, calcium oxide, tin oxide and / or titanium oxide, niobium oxide, and zirconium oxide are contained as secondary components. Including, silicon carbide (S
iC) and silicon nitride (Si ₃ N ₄ ) are not contained, and the content rate of manganese oxide in the main component is 30 to 30 in terms of MnO.
41 mol%, zinc oxide content 6 to 16 in terms of ZnO
Mol%, the weight ratio of the minor component to the main component is 50 to 250 ppm in terms of SiO _{2 in} terms of SiO ₂ , calcium oxide is 200 to 1500 ppm in terms of CaO, and tin oxide is 4000 ppm or less in terms of SnO ₂ , Further, titanium oxide is 3,000 ppm or less in terms of TiO ₂ , the total of tin oxide and titanium oxide is 300 ppm or more, and niobium oxide is 500 ppm or less (excluding 0) in terms of Nb ₂ O ₅ , zirconium oxide. Is 400 ppm or less (not including 0) in terms of ZrO ₂ . (2) The content ratio of niobium oxide to the main component is Nb ₂ O ₅
The ferrite according to (1) above, which has a conversion rate of 50 ppm or more and a zirconium oxide content of 50 ppm or more in terms of ZrO ₂ . (3) The content ratio of niobium oxide to the main component is Nb ₂ O ₅
The ferrite of (1) or (2) above, which is 100 to 400 ppm in terms of conversion. (4) The ferrite according to any of (1) to (3) above, wherein the weight ratio of P to the main component is 0 to 30 ppm. (5) The ferrite according to any one of (1) to (4) above, wherein the weight ratio of B to the main component is 0 to 50 ppm. (6) The ferrite according to any one of (1) to (5) above, which has a power loss of 300 kW / m ³ or less at a temperature of 100 ° C. when an AC magnetic field of 100 kHz and 200 mT is applied. (7) The ferrite of (6) above, which has an eddy current loss of 200 kW / m ³ or less at a temperature of 100 ° C. when an alternating magnetic field of 100 kHz and 200 mT is applied. (8) Temperature 10 when an AC magnetic field of 100 kHz is applied
In the hysteresis curve at 0 ° C, ΔB = Bm
-Br (provided that Bm and Br are the maximum magnetic flux density and the residual magnetic flux density, respectively) of 220 mT or more, and the ferrite according to any one of (1) to (7) above. (9) Temperature 10 when an AC magnetic field of 100 kHz is applied
Magnetization B = 2 in the hysteresis curve at 0 ° C.
Effective permeability μa at 00 mT is 5000 or more, magnetization B = 3
The ferrite according to any one of (1) to (8) above, which has an effective magnetic permeability μa of 4500 or more at 00 mT. (10) Whether the residual magnetic flux density Br measured under a DC magnetic field at a temperature of 25 ° C. is 140 mT or less, or ΔB = Bm−
Br (however, Bm and Br are each at a temperature of 25 ° C.
(1) to (9) above, in which the maximum magnetic flux density and the residual magnetic flux density measured under a DC magnetic field are 380 mT or more.
One of the ferrites. (11) A ferrite core for a power supply, which is formed of the ferrite according to any one of (1) to (10) above.

[0007]

ACTION AND EFFECT The manganese-zinc system ferrite of the present invention is compared by containing silicon oxide, calcium oxide, tin oxide and / or titanium oxide, niobium oxide and zirconium oxide in predetermined amounts. In a very high frequency region (for example, 10 to 500 kHz), power loss is extremely small and ΔB is large. Therefore, O
It is useful as a core of a transformer for output of several W to several tens of W for equipment A. In addition, it shows good μa-B characteristics,
Since the μa is high, the power transformer can be downsized. And such characteristics are realized in a wide temperature range,
The power loss is sufficiently low at an actual operating temperature of about 80 to 110 ° C.

Although some of the above-mentioned publications disclose subcomponent compounds used in the present invention, there are no examples in which specific combinations within the scope of the present invention are tried.

For example, in Japanese Unexamined Patent Publication (Kokai) No. 5-198416, in addition to SiC and CaO as auxiliary components, niobium oxide, titanium oxide, antimony oxide, in a basic component consisting of Fe ₂ O ₃ , MnO and ZnO, Tantalum oxide,
Vanadium oxide, zirconium oxide, tin oxide, aluminum oxide, cobalt oxide, copper oxide, hafnium oxide,
Mn-Zn containing at least one of silicon oxide
Series ferrites are disclosed. However, in the publication,
There is no description that the addition of silicon oxide, calcium oxide, tin oxide and / or titanium oxide, niobium oxide, and zirconium oxide is indispensable. Absent. In the examples of the publication, reduction of loss is observed by adding subcomponents, but Bm, Br, and ΔB at high frequency and direct current are not described, and effective permeability (μa) is also not described.

In Japanese Unexamined Patent Publication No. 5-267040, Fe
_In addition to Si ₃ N ₄ and CaO as subcomponents in the basic component consisting of ₂ O ₃ , MnO and ZnO, niobium oxide, titanium oxide, antimony oxide, tantalum oxide, zirconium oxide, tin oxide, cobalt oxide, oxidation Mn-Zn ferrites containing one or more of silicon are disclosed. However, in this publication, silicon oxide and
There is no description that the addition of calcium oxide, tin oxide and / or titanium oxide, niobium oxide, and zirconium oxide is essential, and there is no example of composite addition of these in the examples of the publication. In the examples of the publication, reduction of loss is observed by adding subcomponents, but Bm, Br, and ΔB at high frequency and direct current are not described, and effective permeability (μa) is also not described.

[0011]

Specific Structure The specific structure of the present invention will be described in detail below. The manganese-zinc ferrite of the present invention is
It contains manganese oxide, zinc oxide, and iron oxide as main components, and silicon oxide, calcium oxide, tin oxide and / or titanium oxide, niobium oxide, and zirconium oxide as subcomponents.

The content of each oxide in the main component is 30 to 41 mol% of manganese oxide in terms of MnO, preferably 33 to 41 mol%, and the content of zinc oxide is 6 to 16 mol% in terms of ZnO. It is preferably 6 to 12 mol%, and the balance is iron oxide. Outside this range, the power loss increases, the minimum temperature becomes 60 ° C. or less and the Curie point becomes 200 ° C. or less, or Bm and initial permeability (μi) in the high frequency region decrease, and Br decreases. Will increase.

The weight ratio of the subcomponent to the main component is as follows.

Silicon oxide is 50 to 25 in terms of SiO _2.
0 ppm, preferably 70 to 200 ppm, and calcium oxide is 200 to 1500 ppm, preferably 300 to 1000 ppm in terms of CaO. By adding silicon oxide and calcium oxide in such a range, B
r decreases, ΔB (= Bm−Br) increases, power loss decreases, the Q value improves, and the μa-B characteristic improves.

Tin oxide is 4000 ppm in terms of SnO _2.
Titanium oxide is 3000ppm in terms of TiO ₂
Below. The total amount of tin oxide and titanium oxide is 300 ppm or more, preferably 500 ppm or more. It is preferable to contain tin oxide in an amount of 500 to 4000 ppm and to use tin oxide alone or to replace 90% by weight or less of tin oxide with titanium oxide. By adding at least one of tin oxide and titanium oxide in such a range, Br is decreased, ΔB is increased, power loss is decreased, μa-B characteristics are further improved, and the core is downsized. It will be possible.

Niobium oxide is 500 pp in terms of Nb ₂ O _5.
m or less (not including 0), preferably 400 ppm or less, and preferably 50 ppm or more, more preferably 1
It is at least 00 ppm. Zirconium oxide is 400 ppm or less (not including 0) in terms of ZrO ₂ , and preferably 50 ppm or more. By adding niobium oxide and zirconium oxide in such a range, power loss is critically decreased, Br is decreased, ΔB is increased, and μ is decreased.
The a-B characteristic is improved.

In addition to these subcomponents, the ferrite of the present invention may contain a trace amount of additional elements and impurity elements in the raw materials. Such elements include P, B, Al, Co, C
Examples include u, Li, Na, K, In, Bi and the like. In order to suppress the power loss and the influence on the magnetic characteristics, the weight ratio of each of these elements to the main component is 200 ppm or less (0 to 2
However, since P and B have a large influence on power loss and magnetic properties, the weight ratio of P to the main component is preferably 0 to 30 ppm, more preferably 0 to 20 ppm, and further preferably Is 0-10ppm
The weight ratio of B to the main component is preferably 0 to 50 ppm, more preferably 0 to 30 ppm.
As a result, Br, ΔB, μa and loss can be improved.

The average crystal grain size of the ferrite of the present invention is preferably 10 to 30 μm, more preferably 10 to 20 μm.
m. If the average crystal grain size is too small, the hysteresis loss increases, and if the average crystal grain size is too large, the eddy current loss increases.

With the ferrite of the present invention, when a 100 kHz sinusoidal alternating magnetic field (maximum value 200 mT) is applied, 10
The power loss at 0 ° C. can be set to 300 kW / m ³ or less, and can be set to 260 kW / m ³ or less. And
Of the power loss, the eddy current loss can be 200 kW / m ³ or less, and can be 170 kW / m ³ or less. The hysteresis loss is proportional to the frequency, and the eddy current loss is proportional to the square of the frequency.
Since the eddy current loss at kHz is relatively small, 100 kH
The power loss does not increase significantly even in the high frequency range exceeding z.

In the ferrite of the present invention, 100 kH
In a hysteresis curve at a temperature of 100 ° C when a z sinusoidal AC magnetic field is applied, Bm is 350 mT
The above is obtained, and the Br is 170 mT or less, especially 150 mT
The following is obtained, and when ΔB = Bm−Br, it is usually 220
mT or more can be obtained, 250 mT or more, and even 280 mT or more can be obtained. In addition, the coercive force Hc is usually 2
0A / m or less is obtained, 14A / m or less, and further 13A / m
You can also get:

In addition, in the ferrite of the present invention, when measured in a DC magnetic field at 25 ° C., Br of 14
0 mT or less is obtained, or ΔB is 380 mT or more, and Bm is 520 mT or more,
As Hc, 12.5 A / m or less, particularly 12.0 A / m or less is obtained.

If Br is small or ΔB is large, the unsaturated region is widened, so that it can be used with a large electric power.
It is also advantageous in minor loop drive when implemented as a core.

In the ferrite of the present invention, 100 kH
In a hysteresis curve at a temperature of 100 ° C. when a sinusoidal AC magnetic field of z is applied, the effective magnetic permeability μa at a magnetization B = 200 mT is 5000 or more, particularly 5200.
As described above, generally about 7,000 or less is obtained, and the magnetization B
= 500m as μa at 300mT, especially 480
A value of 0 or more, particularly 5500 or more, and generally about 7,000 or less can be obtained, and it is possible to obtain a core which is remarkably downsized as compared with the conventional one.

A core for a power transformer composed of such a ferrite has a frequency of 10 to 500 kHz,
It operates at a temperature of about 0 to 110 ° C., and its power is usually about 1 to 100 W.

The ferrite and the ferrite core for power supply of the present invention are usually manufactured by the following method.

As the raw material of the main component, powder of an oxide or a compound which becomes an oxide by heating is used. Specifically, iron oxide powder, manganese oxide powder, manganese carbonate powder, zinc oxide powder and the like can be used. These are mixed and calcined, and the calcined product is pulverized to an average particle size of about 1 to 3 μm. The calcination may be performed in air at a predetermined temperature within the range of 800 to 1000 ° C.

As the raw material of the accessory component, powder of an oxide or a compound which becomes an oxide by heating is usually used, but powder of a simple metal which is a constituent element of the accessory component may be used in some cases.

The mixing ratio of the main component and the subcomponent should correspond to the final composition. The raw material of the main component and the raw material of the subcomponent may be mixed before or after the above-mentioned calcination.

Not limited to the above-mentioned main component raw material, powder of a complex oxide containing two or more kinds of metals may be used as the main component raw material. The powder of such a complex oxide is usually produced by oxidizing and roasting a chloride. For example, by oxidizing and roasting an aqueous solution containing iron chloride, manganese chloride, and zinc chloride, powder of a composite oxide containing Fe, Mn, and Zn can be obtained. Usually, this composite oxide contains a spinel phase. However, zinc chloride has a high vapor pressure and tends to cause compositional deviation. Therefore, a powder of a composite oxide containing Fe and Mn may be produced using an aqueous solution containing iron chloride and manganese chloride, and this powder may be mixed with zinc oxide powder or zinc ferrite powder to be used as a main component raw material. When the complex oxide powder produced by the oxidative roasting method is used as the main component raw material, it is not necessary to perform the above-mentioned calcination.

Next, a small amount of a suitable binder, for example, polyvinyl alcohol, is added to the mixture of the main component raw material and the subcomponent raw material, and this is mixed with a spray dryer or the like at 80 to 200.
Granules with a diameter of approximately μm. And molded, then
This molded product is usually fired at a predetermined temperature in the range of 1250 to 1400 ° C in an atmosphere in which the oxygen concentration is controlled to obtain ferrite.

[0031]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention.

Ferrite core samples having the compositions shown in Table 1 were prepared. First, the calcined material of the main component raw material and the raw material of the subordinate component were mixed. Fe ₂ O is used as the main ingredient material.
₃ , ₃ , Mn ₃ O ₄ and ZnO were mixed, and then they were mixed and calcined at 900 ° C. for 3 hours. The raw material for the subcomponents is S
iO ₂ , CaCO ₃ , SnO ₂ , TiO ₂ , Nb ₂ O ₅
And ZrO ₂ were used. Raw materials for the subcomponents were added to the calcined product of the raw materials for the main components and mixed while being crushed. Crushing
The process was repeated until the average particle size of the calcined product became about 2 μm. A binder was added to the obtained mixture, and the mixture was granulated with a spray dryer to an average particle size of 150 μm, and then molded and sintered at 1300 ° C. for 5 hours in an atmosphere with controlled oxygen partial pressure,
A toroidal sample having an outer diameter of 31 mm, an inner diameter of 19 mm and a height of 8 mm was obtained. When the ratio of the component elements in the sample was measured by fluorescent X-ray analysis and compared with the raw material composition, the ratio of the component elements was the same. The P content shown in Table 1 was measured by an absorptiometry. Further, when the content ratio of B in the samples was measured by ICP, the content ratio of B was 30 ppm or less in all the samples. It is considered that P and B are derived from a raw material oxide such as iron oxide.

For each sample, 100 kHz, 200
Applying a sinusoidal AC magnetic field of mT (maximum value),
The hysteresis loss (Phv), eddy current loss (Pev), and core loss (Pcv) at 0 ° C. were measured. The results are shown in Table 2. By the way, when the residual loss is Prv, the equation is generally I Pcv = Phv + Pev + Prv, and when the driving frequency is f, Phv = α × f Pev = β × f ² Prv = γ (α, β, γ are constants) Is. Therefore, the formula II Pcv = α × f + β × f ² + γ is obtained, and when both sides of this formula are divided by f, the formula III Pcv / f = β × f + α + γ / f is obtained. Here, if γ is sufficiently small, the formula III can be approximated to a linear formula of f. In the ferrite used in each sample, γ is sufficiently small in the frequency band of 25 to 500 kHz, so in Table 2, Pcv = Phv + Pev.

For each sample, Br, Hc and ΔB = Bm-Br in a hysteresis curve at a temperature of 100 ° C. when a 100 kHz sinusoidal AC magnetic field was applied were determined. Also, the magnetization B = 2 in this hysteresis curve
The μa at 00 mT and the μa at magnetization B = 300 mT were determined. Further, a DC magnetic field was applied, and Br, Hc, and ΔB = Bm−Br at 25 ° C. were obtained. The results are shown in Table 2.

[0035]

[Table 1]

[0036]

[Table 2]

The average crystal grain size of each sample is 10 to 10.
It was 15 μm. FIG. 1 shows an optical micrograph of the sample No. 1 cross section, and FIG. 2 shows an optical micrograph of the sample No. 12 cross section. 1 and 2, the crystal grain shapes are almost the same and the average crystal grain sizes are also the same.

As shown in Table 2, both the hysteresis loss and the eddy current loss are small in the sample of the present invention, and therefore the core loss is small. The hysteresis loss generally decreases as the crystal grain size increases, and the eddy current loss decreases as the crystal grain size decreases. From the comparison between FIG. 1 and FIG. 2, the loss reduction in the sample of the present invention depends on the crystal grain size. You can see that it was not done.

The sample of the present invention has a small Hc,
Since ΔB is large, it can be used with a large amount of power and exhibits excellent μa-B characteristics. As a result, it can be seen that the size of the power supply transformer and the efficiency of the power supply using it can be reduced. . More specifically, the core size can be made extremely small. As a result of improved efficiency, less input power is required and the number of windings can be reduced. Also, the amount of heat generated changes depending on the input power and core shape,
The power used is limited according to the amount of heat generated, but since the core of the present invention has a small power loss, the input power can be further increased.

In the above sample No. 12, when the weight ratio of silicon oxide to the main component was less than 50 ppm, the core loss (particularly eddy current loss) was increased to 25
The core loss increased even when the content exceeded 0 ppm. When the weight ratio of calcium oxide to the main component is less than 200 ppm, core loss (particularly eddy current loss) increases, and Br increases and ΔB decreases, resulting in 1500 ppm.
The core loss increased even when it was over. In addition, when the weight ratio of tin oxide to the main component is more than 4000 ppm, and when titanium oxide of more than 3000 ppm is added without adding tin oxide, the temperature at which the core loss becomes a minimum is 60 ° C or less. Oops.

Further, in Sample No. 12, even when tin oxide and titanium oxide were used in combination instead of tin oxide alone, it was possible to obtain the same characteristics as in Sample No. 12.

[Brief description of drawings]

FIG. 1 is a drawing-substitute photograph showing a crystal structure, which is an optical microscope photograph of a cross section of a ferrite core.

FIG. 2 is a drawing-substitute photograph showing a crystal structure, which is an optical microscope photograph of a cross section of a ferrite core.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuji Inoue 1-13-1, Nihonbashi, Chuo-ku, Tokyo TDK Corporation (56) References JP-A-5-198416 (JP, A) JP-A 5-267040 (JP, A) JP-A-3-163802 (JP, A) JP-A-3-223119 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01F 1/34

Claims (11)

(57) [Claims] 1. Manganese oxide, zinc oxide, and iron oxide are contained as main components, and silicon oxide, calcium oxide, tin oxide and / or titanium oxide, niobium oxide, and zirconium oxide are contained as secondary components. And does not contain silicon carbide (SiC) and silicon nitride (Si ₃ N ₄ ), the content of manganese oxide in the main component is 30 to 41 mol% in terms of MnO, and the content of zinc oxide is in terms of ZnO. 6
Is 16 mol%, the weight ratio of the subcomponents to the main component is 50 to 250 ppm in terms of SiO _{2 in} terms of SiO ₂ , calcium oxide is 200 to 1500 ppm in terms of CaO, and tin oxide is 4000 ppm in terms of SnO _2. or less and the titanium oxide is not more 3000ppm or less in terms of TiO _2, the total of tin oxide titanium oxide is not less 300ppm or more and 500ppm or less niobium oxide calculated _as Nb ₂ O ₅ (not including 0), 400ppm or less of zirconium oxide is ZrO ₂ in terms of (0
Ferrite, characterized in that 2. The content of niobium oxide with respect to the main component is N.
The ferrite according to claim 1, wherein the ferrite content is 50 ppm or more in terms of b ₂ O ₅ , and the content ratio of zirconium oxide to the main component is 50 ppm or more in terms of ZrO ₂ . 3. The content of niobium oxide with respect to the main component is N.
The ferrite according to claim 1 or 2, which has a content of 100 to 400 ppm in terms of b ₂ O ₅ . 4. The weight ratio of P to the main component is 0 to 30 pp.
The ferrite according to claim 1, which is m 3. 5. The weight ratio of B to the main component is 0 to 50 pp.
The ferrite according to claim 1, which is m 2. 6. A power loss of 300 kW / m at a temperature of 100 ° C. when an alternating magnetic field of 100 kHz and 200 mT is applied.
The ferrite according to any one of claims 1 to 5, which is ³ or less. 7. An eddy current loss at a temperature of 100 ° C. is 200 kW when an AC magnetic field of 100 kHz and 200 mT is applied.
The ferrite according to claim 6, which is not more than / m ³ . 8. In a hysteresis curve at a temperature of 100 ° C. when an alternating magnetic field of 100 kHz is applied, Δ
B = Bm-Br (however, Bm and Br are a maximum magnetic flux density and a residual magnetic flux density, respectively) of 220 mT or more, The ferrite in any one of Claims 1-7. 9. In a hysteresis curve at a temperature of 100 ° C. when an AC magnetic field of 100 kHz is applied, the effective permeability μa at a magnetization B = 200 mT is 5000 or more, and the effective permeability μa at a magnetization B = 300 mT is 4500 or more. The ferrite according to any one of claims 1 to 8. 10. The residual magnetic flux density Br measured under a DC magnetic field at a temperature of 25 ° C. is 140 mT or less, or ΔB
= Bm-Br (where Bm and Br are the maximum magnetic flux density and residual magnetic flux density measured under a DC magnetic field at a temperature of 25 ° C, respectively) of 380 mT or more.
Any one of 9 ferrites. 11. A ferrite core for a power supply, comprising the ferrite according to any one of claims 1 to 10.