JP2006347848A - Low loss ferrite material for power source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wide temperature range low loss ferrite having sufficiently small power loss in a high temperature range. <P>SOLUTION: The wide temperature range low loss ferrite is a magnetic ferrite material consisting essentially of iron oxide, zinc oxide and manganese oxide wherein the content of the zinc oxide is 8.0-15.0 mol% expressed in terms of ZnO, the content of the iron oxide is 55.0-65.0 mol% expressed in terms of Fe<SB>2</SB>O<SB>3</SB>and the balance is manganese oxide. As subsidiary components, 0-30,000 (excluding 0) ppm CuO, 5,000-60,000 ppm NiO, 280-1,680 ppm CaO and 50-500 ppm SiO<SB>2</SB>are contained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an Mn—Zn-based low-loss ferrite suitable for a coil magnetic core of a switching power supply.

  Mn-Zn ferrite is used in transformer materials for various communication devices, consumer devices, etc., but in conventional switching power transformers, the switching frequency region is exclusively 100 kHz to 500 kHz, and about 1 MHz in part. This is also in practical use. In recent years, with the increase in communication capacity, space-saving and multifunctional consumer devices, and the advancement of electronics in automobiles, miniaturization is required by further increasing the switching frequency, and a low-loss magnetic material compatible with high frequencies of 2 MHz or higher. The use temperature range is mainly 20 to 120 ° C. A magnetic ferrite material suitable for this purpose has a low loss in a frequency region near 2 MHz, a temperature region of 20 to 120 ° C., and a temperature exhibiting a minimum loss is in a region of 60 to 120 ° C. desirable. On the other hand, if the permeability of the transformer of the switching power supply or the core of the choke coil portion is too low, it becomes an obstacle to the reduction in the number of turns of the coil. The magnetic permeability at room temperature of a conventional ferrite core used for a switching frequency of 1 MHz is about 900 to 1500, and about 500 or more is desirable for a switching frequency of 2 MHz.

  In the case of conventional Mn—Zn ferrite, core loss in the region of frequency 1 to 2 MHz, maximum magnetic flux density 50 to 100 mT, and temperature 100 to 120 ° C. is large, so it is easy to cause thermal runaway when driving the power source. There was a drawback that there was a risk of destroying electronic components. In view of the above problems, the present invention intends to provide a wide temperature region low-loss ferrite with a sufficiently low power loss even in a high temperature region.

In the present invention, Fe ₂ O ₃ , MnO, and ZnO are the main components, and CuO is used as a subcomponent.
0 to 30000 ppm (excluding 0), NiO 5000 to 60000 ppm is added, CaO 280 to 16800 ppm, SiO ₂ 50 to 500 ppm is contained, and Ta ₂ O ₅ 3000 ppm or less, ZrO ₂ 4000 ppm or less, V ₂ O ₅ as appropriate. By adding and containing at least one of 3000 ppm or less, a low loss ferrite in a high frequency region near 2 MHz and a high magnetic flux density region of 30 mT or more is provided.
The reason why NiO and CuO are added as main components in the present invention is as follows.
When CuO and NiO are not added, the temperature range in which the core loss at 2 MHz and 50 to 70 mT is minimum is 40 ° C. or less, and the power loss in the high temperature region of 60 ° C. or more increases. However, as shown in the present invention, by adding and containing CuO and NiO in the main components of Fe ₂ O ₃ , MnO, and ZnO, the temperature that shows the minimum value of power loss at 2 MHz and 50 to 70 mT is 60 ° C. to 120 ° C. A Mn—Zn-based low-loss ferrite for a power source with a wide temperature range, which is in the range of ° C. and has a sufficiently low power loss in a higher temperature range than before, can be obtained.
Further, it is possible to further reduce the loss by appropriately adding and containing at least one of Ta ₂ O ₅ 50 to 3000 ppm, ZrO ₂ 50 to 4000 ppm, and V ₂ O ₅ 50 to 3000 ppm.

In the magnetic ferrite material of the present invention, the minimum value of the core loss measured at a maximum magnetic flux density of 50 mT and a frequency of 2 MHz is 2000 kW / m ³ or less, and the temperature at which the core loss is minimized is a temperature range of 40 ° C. to 120 ° C. Magnetic ferrite material. And in the temperature range of 20 ° C. to 120 ° C., the difference between the maximum value and the minimum value of the core loss measured at a maximum magnetic flux density of 50 mT and a frequency of 2 MHz is less than 1500 kW / m ³ .

In the magnetic ferrite material of the present invention, the minimum core loss measured at a maximum magnetic flux density of 70 mT and a frequency of 2 MHz is 5000 kW / m ³ or less, and the temperature at which the core loss is minimized is a temperature of 40 ° C. to 120 ° C. Magnetic ferrite material in the band. In the temperature range of 20 ° C. to 120 ° C., the difference between the maximum value and the minimum value of the core loss measured at a maximum magnetic flux density of 70 mT and a frequency of 2 MHz is 4000 kW / m ³ or less.

  The magnetic ferrite material of the present invention is characterized in that the AC initial permeability is 500 or more at 20 ° C.

  According to the magnetic ferrite material of the present invention, the temperature showing the minimum value of the power loss in the high magnetic flux density region of 30 to 100 mT at a high frequency around 2 MHz is in the range of 60 ° C. to 120 ° C., and in a wider temperature range than before. An Mn—Zn-based power loss low loss ferrite with a sufficiently small power loss can be obtained.

In the following, embodiments of the low-loss ferrite for a wide temperature range for power supply according to the present invention will be described. After blending the raw material oxides of each component so that the basic components have the final composition shown in Table 1, followed by wet mixing using a ball mill for 4 hours and drying, at 900 ° C. in an air atmosphere. After calcining, as secondary components, CuO (10000 ppm), NiO (20000 ppm), CaCO ₃ (1000 ppm when converted to CaO) (560 ppm) and SiO ₂ (100 ppm) were added together, and the mixture was pulverized with a ball mill for 15 hours. However, CaO, as SiO _2, in advance, for the sub-component contained in the raw material, reducing the amount to be added after calcination correspondingly as a whole and to match the proportions of the components. Moreover, even if NiO and CuO are added at the time of mixing before temporary baking, there is no difference in characteristics. After drying this pulverized raw material, 1 wt% of the binder was added in terms of solid content, and granulated and molded. This molded body was fired at 1100 ° C. for 5 hours in a nitrogen / oxygen mixed gas with a controlled oxygen partial pressure. The shape of the fired body was a ring shape having an outer diameter of 14 mm, an inner diameter of 7 mm, and a height of 3 mm. The obtained fired body was measured with a BH analyzer and an LCR meter.

Table 1 shows the characteristic results of the core. Samples 1 to 13 are examples of the present invention, and samples 14 to 17 are comparative examples in which Fe ₂ O ₃ and ZnO are outside the scope of the claims. Hereinafter, the sample numbers of the comparative examples in the table are distinguished by giving *.
As is clear from these results, the proportions of the main components Fe ₂ O ₃ , ZnO, and MnO are Fe ₂ O _3.
In the range of 55.0 to 65.0 mol%, ZnO 8.0 to 15.0 mol%, and the remaining manganese oxide, the minimum core loss at a maximum magnetic flux density of 50 mT and a frequency of 2 MHz in the temperature range of 20 to 120 ° C. The value is 2000 kW / m ³ or less, the difference between the maximum value and the minimum value of the core loss is 1500 kW / m ³ or less, and the minimum value of the core loss at a maximum magnetic flux density of 70 mT and a frequency of 2 MHz is 5000 kW / m ^3. The difference between the maximum value and the minimum value of the core loss is 4000 kW / m ³ or less, and the temperature at which the core loss is minimized can be controlled in a temperature range of 40 ° C. to 120 ° C. The magnetic permeability can be 500 or more.

  In addition, if the subcomponents CuO and NiO added after the pre-baking of the above-mentioned main components are within the range of CuO 10 to 30000 ppm and NiO 500 to 60000 ppm, characteristics similar to those of the examples shown in Table 1 may be obtained. all right. However, if there is more CuO than 30000 ppm, power loss will become large and magnetic permeability will fall rapidly. When there is more NiO than 60000 ppm, a power loss will become large and a magnetic permeability will fall rapidly. When NiO is less than 5000 ppm, the electrical resistance is lowered, so the eddy current loss in the high frequency region is increased and the power loss is increased. Table 2 shows data showing the results. The samples shown in Table 2 were prepared by changing the subcomponent composition in the same sample preparation process as the example shown in Table 1. Samples 18 to 32 are examples of the present invention, and samples 33 and 34 are comparative examples in which CuO and NiO are outside the scope of the claims.

In addition, subcomponents CaO and SiO ₂ added after the pre-baking of the above-mentioned main components are CaO.
It was found that characteristics similar to those of the examples shown in Table 1 can be obtained if they are in the range of 280 to 1680 ppm and SiO2 of 50 to 500 ppm. However, when there is more CaO than 1680 ppm, electric power loss will become large and magnetic permeability will fall. If the CaO content is less than 280 ppm, the electrical resistance is lowered, so the eddy current loss in the high frequency region increases and the power loss increases. When the subcomponent SiO ₂ exceeds the range, abnormal sintering occurs, power loss increases, and magnetic permeability decreases. On the other hand, when the subcomponent SiO ₂ is less than the range, the electrical resistance is lowered and the power loss is increased. Table 3 shows data showing the results. The samples shown in Table 3 were prepared by changing the subcomponent composition in the same sample preparation process as the example shown in Table 1. Samples 35 to 45 are examples of the present invention, and samples 46, 47, and 48 are comparative examples in which CaO and SiO ₂ are outside the scope of the claims.

Further, the subcomponents Ta ₂ O ₅ and ZrO _{2 to be} added after the above-mentioned main component is pre-baked are Ta ₂ O _5.
It was found that the characteristics of the examples shown in Table 1 can be further improved if they are within the ranges of 50 to 3000 ppm and ZrO ₂ 50 to 4000 ppm. However, if Ta ₂ O ₅ is more than 3000 ppm, and if ZrO ₂ is more than 4000 ppm, the power loss increases and the magnetic permeability decreases. When both Ta ₂ O ₅ and ZrO ₂ are less than 50 ppm, no effect is observed as compared with the case of the examples shown in Table 1. Table 4 shows data showing the results. The samples shown in Table 4 were prepared by changing the subcomponent composition in the same sample preparation process as the example shown in Table 1. Samples 49 to 63 are examples of the present invention, and samples 64 and 65 are comparative examples in which Ta ₂ O ₅ and ZrO ₂ are outside the scope of the claims.

Further, the subcomponent V ₂ O ₅ added after the pre-baking of the main component is V ₂ O _5.
It was found that the characteristics of the examples shown in Table 1 can be further improved within the range of 20 to 3000 ppm. However, if it exceeds V ₂ O ₅ 3000 ppm, the power loss increases and the magnetic permeability decreases. If it is less than 50 ppm, no effect is observed. Table 5 shows data showing the results. Samples shown in Table 5 were prepared by changing the subcomponent composition in the same sample preparation process as the example shown in Table 1. Samples 66 to 76 and 78 are examples of the present invention, and sample 77 is a comparative example in which V ₂ O ₅ is outside the scope of the claims.

  1 and 2 are graphs showing temperature characteristics of power loss of the magnetic ferrite material. It can be seen that the magnetic ferrite material according to the present invention has a sufficiently small power loss in a wide temperature range as compared with the comparative example.

As described above, the low-loss ferrite for power supply having a wide temperature range includes Fe ₂ O ₃ , MnO, and ZnO as main components and CuO as subcomponents.
0-30000 ppm (excluding 0), NiO 5000-60000 ppm, CaO 280-1680 ppm, SiO ₂ 50-500 ppm, Ta ₂ O ₅ 3000 ppm or less, ZrO ₂
50-4000 ppm or less and V ₂ O ₅ 3000 ppm or less are selected and added, and the temperature which shows the minimum value of the power loss in the high frequency vicinity of 2 MHz and the high magnetic flux density region of 30 mT or more is in the range of 60 ° C. to 120 ° C. Therefore, it is possible to obtain a Mn—Zn-based low-loss ferrite for power supply that has a sufficiently low power loss in a wider temperature range than before.

The temperature characteristic of the power loss in the frequency 2MHz and the magnetic flux density 50mT of the magnetic ferrite material which concerns on the Example of this invention and the magnetic ferrite material of a comparative example is shown. The temperature characteristic of the power loss in the frequency 2MHz and the magnetic flux density 70mT of the magnetic ferrite material which concerns on the Example of this invention and the magnetic ferrite material of a comparative example is shown.

Claims (7)

A magnetic ferrite material mainly composed of iron oxide, zinc oxide, and manganese oxide, wherein the zinc oxide content is in the range of 8.0 to 15.0 mol% in terms of ZnO, and the iron oxide content is Fe. _{It has} a range of 55.0 to 65.0 mol% in terms of ₂ O ₃ and the remaining manganese oxide, and as subcomponents, CuO 0 to 30000 ppm (excluding 0), NiO 5000 to 60000 ppm, CaO 280 A magnetic ferrite material containing 1680 ppm and SiO ₂ 50 to 500 ppm. The magnetic ferrite material according to claim 1, further comprising at least one of Ta ₂ O ₅ 3000 ppm or less, ZrO ₂ 4000 ppm or less, or V ₂ O ₅ 3000 ppm or less as a subcomponent. The minimum value of the core loss measured at a maximum magnetic flux density of 50 mT and a frequency of 2 MHz is 2000 kW / m ³ or less, and the temperature at which the core loss is minimized is in a temperature range of 40 ° C. to 120 ° C. Item 3. The magnetic ferrite material according to Item 1 or 2. In the temperature range of 20 ° C. to 120 ° C., the maximum magnetic flux density 50 mT, the difference between the maximum value and the minimum value of the core loss measured at a frequency of 2MHz is of claims 1 to 3, characterized in that it is less than 1500 kW / ^{m 3} The magnetic ferrite material according to any one of the above. The minimum value of the core loss measured at a maximum magnetic flux density of 70 mT and a frequency of 2 MHz is 5000 kW / m ³ or less, and the temperature at which the core loss is minimized is in a temperature range of 40 ° C. to 120 ° C. Item 5. The magnetic ferrite material according to any one of Items 1 to 4. The difference between the maximum value and the minimum value of the core loss measured at a maximum magnetic flux density of 70 mT and a frequency of 2 MHz in a temperature range of 20 ° C to 120 ° C is 4000 kW / m ³ or less. The magnetic ferrite material described in any one. The magnetic ferrite material according to any one of claims 1 to 6, wherein an alternating current initial permeability is 500 or more at 20 ° C.

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