JP3381947B2 - Power supply ferrite and power supply core - 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 magnetic core for a power source transformer or the like that operates at a high frequency of about 100%, and a power source magnetic core formed from the same.

[0002]

2. Description of the Related Art Manganese-zinc type ferrite is widely used as a coil and a transformer material for various communication equipments, consumer equipments, etc., but recently, a power source with a high frequency tends to be used, which meets its purpose. Performance as a transformer material has been required. Especially for switching power supplies, it is necessary to have a transformer material that can be used with a power of several tens of watts in the high frequency range of 10 kHz to 500 kHz. In addition to this, a stable transformer material for motor drive, signal amplification, oscillation, etc. is also required. It is said that. Until now, manganese-zinc-based low-loss ferrite has been used as a transformer material, but in the high frequency region of about 10 kHz 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. One such suggestion is
Add oxides of Si and Ca, Sn, Ti, Zr
There are those in which a tetravalent metal oxide such as V or Nb, or a pentavalent metal oxide such as Ta is added. As an example of the addition of a tetravalent or pentavalent metal oxide alone or in combination, Japanese Patent Laid-Open No.
No. 6-2880, No. 48-72696, No. 6
0-262404, 61-108109, 61-252609, 61-25261.
No. 1, JP-A No. 63-222018, JP-A No. 1-1.
No. 29403, No. 2-54902, and No. 3-1.
No. 41611, No. 3-163804, No. 3-
No. 223119, No. 3-248403, No. 3
No. 248404, No. 3-248405, No. 3-254103, No. 4-55362, No. 4-150007.

However, all of them have a large residual magnetic flux density on the BH curve at a high frequency, for example, 100 kHz and 100 ° C., and the difference ΔB = Bm between the maximum magnetic flux density Bm and Br.
Bm-Br is small, power loss at high frequencies is large, and the magnetic permeability μa in the μa-B characteristic is low, which makes it difficult to reduce the size of the transformer.

[0004]

SUMMARY OF THE INVENTION A main object of the present invention is to provide a low power loss ferrite having a large ΔB = Bm-Br at high frequency and an improved μa-B characteristic, that is, a power supply ferrite and a power supply using the same. It is to provide a magnetic core.

[0005]

The above objects are achieved by the present invention described in (1) to (4) below. (1) 51 to 57 mol% of iron oxide in terms of Fe ₂ O ₃ and 30 to 41 mol% of manganese oxide in terms of MnO;
It contains 6 to 16 mol% of zinc oxide in terms of ZnO, and further contains 50 to 250 ppm of silicon oxide in terms of SiO ₂ .
It contains 400 to 2500 ppm of calcium oxide in terms of CaCO ₃ , 500 to 4000 ppm of tin oxide in terms of SnO ₂ , and 100 to 500 ppm or less of niobium oxide in terms of Nb ₂ O ₅ , titanium oxide, tantalum oxide and vanadium oxide. And a part of the niobium oxide is Zr.
Ferrite for power supply, which may be substituted with zirconium oxide in a total amount of 90% or less in terms of O ₂ and further, SiC is not added. (2) In the 100 kHz B-H curve at 100 ° C., the magnetic permeability μa at B = 200 mT is 5200 or more, and B = 3.
Ferrite for power supply according to the above (1), wherein μa of 00 mT is 4500 or more. (3) ΔB = Bm−Br at 100 kHz at 100 ° C.
(However, Bm and Br are the maximum magnetic flux density and the residual magnetic flux density, respectively) of 110 mT or more, the ferrite for power supply of the above (2). (4) A power supply magnetic core formed from the power supply ferrite according to any one of (1) to (3) above.

[0006]

Specific Structure The specific structure of the present invention will be described in detail below. The manganese-zinc system ferrite material in the present invention contains iron oxide, manganese oxide and zinc oxide as main components.

Each of these main components is generally
e ₂ O ₃ equivalent 51-57 mol%, MnO equivalent 30-41
Mol%, 6 to 16 mol% in terms of ZnO. 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 increases. To do

Such a main component contains oxides of silicon and calcium. By containing silicon oxide and calcium oxide, Br decreases, ΔB increases, power loss decreases, Q value improves, and μa-B characteristics improve. In this case, the contents of silicon oxide and calcium oxide are SiO ₂ and CaCO ₃ , respectively.
It is preferably 50 to 250 ppm and 400 to 2500 ppm in terms of conversion.

Further, tin oxide is contained in the ferrite. By containing tin oxide, Br is decreased, ΔB is increased, power loss is decreased, μ is improved, and μa-B characteristics are further improved, resulting in size reduction. The content expressed as SnO ₂ conversion value is 4000 ppm or less in tin oxide, and the total of these is 300 ppm or more,
Particularly, it is 500 ppm or more. And 500-4000
Contains ppm tin oxide, tin oxide alone, no titanium oxide.

Further, the ferrite contains niobium or an oxide of niobium and zirconium. By containing them, Br decreases, ΔB increases, power loss decreases, and μa-B characteristics improve. N each
The content of b ₂ O ₅ and ZrO ₂ is 50% in niobium oxide.
It is 0 ppm or less, and the total of these is 50 ppm or more, particularly 100 ppm or more. And, it contains 100 to 500 ppm of niobium oxide and is either niobium oxide alone or 90% by weight or less of niobium oxide substituted with zirconium oxide. It should be noted that tantalum oxide and vanadium oxide are not contained.

Further, the P content in ferrite is 30
It is preferable to regulate to below ppm, that is, to 0 to 30 ppm. As a result, Br, ΔB, μa and loss can be improved. In addition, in ferrite,
Within the range of 0-200ppm, aluminum, cobalt,
Oxides such as copper, lithium, sodium, potassium, indium and bismuth may be contained.

The average crystal grain size of ferrite containing such components is generally about 10 to 30 μm. And at 100 ℃, sine wave 100kHz, 200mT,
A low power loss of 400 kW · m ⁻³ or less, particularly 350 kW · m ⁻³ or less, and 200 to 300 W · m ⁻³ can be obtained. Also, in the BH loop at 100 kHz and 100 ° C, B
m is 350-370 mT, Br is 120-170 mT, ΔB
Is 110 mT or more, especially 220 mT or more, and further 220-
250 mT, Hc is 0.43 Oe or less, especially 0.35 to 0.
40 Oe is obtained. Furthermore, B of 100kHz, 100 ℃
In the −H loop, the magnetic permeability μa at B = 200 mT is 52
00 or more, particularly 5500 or more, generally about 7,000 or less, and μa of B = 300 mT is 4500 or more, especially 4
It is 800 or more, particularly 5500 or more, and generally about 7,000 or less, and it is possible to obtain a magnetic core which is remarkably downsized as compared with the conventional one. A magnetic core for a power transformer formed of such a ferrite material operates at a frequency of 10 to 500 kHz and a temperature of about 80 to 110 ° C., and its power is about 1 to 100 W. .

In order to manufacture the ferrite material and the magnetic core of the present invention, first, as a main component, a usual iron oxide component,
A mixture of a manganese oxide component and a zinc oxide component is prepared.

Then, a compound of the above-mentioned metal or metalloid component is added to these main components. The added amount corresponds to the composition ratio of the final component. After mixing the main component and the minor component to be added in this way, a suitable binder, for example, polyvinyl alcohol, is added thereto in a small amount, and the mixture is made into granules having a diameter of about 80 to 200 μm by a spray dryer or the like. Then, it is molded, and then this molded product is usually heated to 1250 to 140 in an atmosphere in which the oxygen concentration is controlled.
Baking is performed at a predetermined temperature within the range of 0 ° C.

[0015]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention. Example 1 MnO (36.2 mol%), ZnO (10.3 mol%), Fe ₂ O ₃ (53.5 mol%) as main components, and SiO ₂ (120 ppm) and CaCO ₃ (12) as subcomponents.
00ppm), SnO ₂ (2000ppm), Nb ₂ O ₅
(300 ppm) was added. P in this sample No. 1
Was less than 30 ppm.

Further, SnO ₂ and Nb ₂ O ₅ of this sample No. 1 were changed as shown in Tables 1 to 3 to obtain sample Nos. 2 to 49 for the present invention and for comparison. The P content of all samples was less than 30 ppm.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3]

After mixing these, a binder was added and the mixture was granulated with a spray drier to an average particle size of 150 μm, molded, and sintered at 1330 ° C. for 4 hours while controlling the oxygen atmosphere, and the outer diameter was 31 mm and the inner diameter was 19 mm. A toroidal core having a height of 8 mm was obtained. When the final composition was measured by fluorescent X-ray, it corresponded to the raw material composition.

Table 4 shows the μa at B = 200 mT and 300 mT of the BH loop at 100 kHz and 100 ° C. Also, Table 5 shows the B-H loop at 100 kHz and 100 ° C.
m, Br, ΔB = Bm−Br and Hc are shown. Furthermore, the power loss (core loss) at 100 kHz, 200 mT, and 100 ° C. is shown.

[0022]

[Table 4]

[0023]

[Table 5]

[0024]

[Table 6]

From the results shown in Tables 4, 5 and 6, the sample of the present invention has a small Hc, a large ΔB, a small power loss, can be used at a large power, and has a good μa-B characteristic. As a result, it can be seen that the downsizing of the power supply transformer and the efficiency of the power supply using the same can be achieved. More specifically, the core size is extremely small. As a result of improved efficiency, less input power is required and the number of windings can be reduced. Further, the amount of heat generation changes depending on the input power and the core shape, and the limit of the power used depends on the amount of heat generation, but this input power can be further increased.

[0026]

The manganese-zinc type ferrite of the present invention has a relatively high frequency range of 10 kHz to 500 kHz.
Since ΔB is large and the loss is low, O
It is useful as a magnetic core of a transformer having an output of several W to several tens of W for A equipment. At this time, good μa-B characteristics are exhibited, and high μa is exhibited, so that the power transformer can be downsized. And, such a feature is realized in a wide temperature range, and the power loss is sufficiently low at an actual operating temperature of about 80 to 110 ° C.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01F 1/12-1/375

Claims (4)

(57) [Claims] 1. Containing 51 to 57 mol% of iron oxide in terms of Fe ₂ O ₃ , 30 to 41 mol% of manganese oxide in terms of MnO, and 6 to 16 mol% of zinc oxide in terms of ZnO, further the silicon oxide 50~250ppm in terms of SiO _2, calcium oxide in 400~2500ppm in terms of CaCO _3, and tin oxide 500~4000ppm in terms of SnO _2, Nb ₂ O ₅ 100 to 500 ppm or less of niobium oxide in terms of And does not contain titanium oxide, tantalum oxide, and vanadium oxide, and part of the niobium oxide may be replaced with zirconium oxide in a total amount of 90% or less in terms of ZrO _2. Further, SiC is added. Not for power ferrite. 2. A 100 kHz BH curve at 100 ° C. has a magnetic permeability μa of 5200 or more at B = 200 mT,
2. The ferrite for a power supply according to claim 1, wherein μa of = 300 mT is 4500 or more. 3. ΔB = Bm− at 100 kHz at 100 ° C.
3. Br (provided that Bm and Br are the maximum magnetic flux density and residual magnetic flux density, respectively) of 110 mT or more.
Power supply ferrite. 4. A power supply magnetic core formed from the power supply ferrite according to claim 1.