JPH04249302A - High-frequency transformer - Google Patents

Abstract

PURPOSE:To obtain the title transformer which is suitably used for a main transformer as a switching power supply by providing the following: a magnetic core composed of an Fe-based amorphous magnetic material whose composition is expressed as Fe86-xSi6B10Nbx and in which the value of (x) is within a specific range; and a winding which has been wound on the magnetic core. CONSTITUTION:The title transformer is provided with the following: a magnetic core 2 composed of an Fe-based amorphous magnetic material whose composition is expressed as Fe86-xSi6B10Nbx and in which 0.5 atomic %<=x<=6 atomic %; and a winding 3 which has been wound on the magnetic core 2. For example, the title transformer is provided with a shell-type magnetic core 2 formed of said Fe-based amorphous magnetic material. Thereby, since the eddy-current loss in a high-frequency region such as 1MHz or the like of said amorphous magnetic material is small and the material is provided with a high saturation flux density, it is possible to obtain a high-frequency transformer whose loss in the high-frequency region is small and whose saturation flux density is high. When the high-frequency transformer is used, a switching power supply can be made small-sized.

Description

Description: FIELD OF INDUSTRIAL APPLICATION This invention relates to a high frequency transformer suitable for use as a main transformer of a switching power supply. [0002] In recent years, as OA equipment has become smaller, lighter, and cheaper, the proportion of these power supplies in the equipment has increased significantly, and the miniaturization of various power supplies has been rapid. is being advanced. Switching power supplies, which have been miniaturized in accordance with recent trends, are replacing normal 50 Hz power supplies in fields such as power electronics. [0003] If we consider the components of a typical switching power supply, it includes various magnetic parts such as a noise filter, a main transformer, a saturable magnetic core, a noise absorber, and a smoothing choke. Therefore, it can be seen that by increasing the switching frequency of these magnetic components, it is possible to realize miniaturization of these magnetic components. For this reason, miniaturization and higher efficiency of various components used in switching power supplies have become important issues. Due to this trend, the operating frequency of recent switching power supplies has reached as high as 500 kHz, but in the future, the goal is to operate at 1 MHz in order to further downsize switching power supplies. Due to the above background, great efforts have been made to reduce eddy current loss in the high frequency range of components used in switching power supplies. Conventionally, Mn- was mainly used as the magnetic core material of the main transformer used in this type of switching power supply.
Zn ferrite, silicon steel, etc. are used. [0007] However, although all of the above-mentioned conventional materials have good squareness, they have the problem of large loss in the high frequency region. For example, in a ferrite core, the loss at 1MHz is 100kHz.
Test results showing that the loss is 60 times greater than that in z have also been well received. Therefore, as magnetic materials that can meet these demands, amorphous alloys such as Co-based alloys, which have the characteristic of low core loss even in high frequency regions, are attracting attention as magnetic cores for switching power supplies, and are being used as saturable magnetic cores and It is becoming widely used in some parts such as smooth chokes. However, there have been no examples of using amorphous alloys for high-frequency transformers in the high-frequency range of 100 kHz or higher, and among the previously known Co-based amorphous alloys, those with a saturated hourly density of less than 10,000 G However, the further miniaturization of the main transformer has the problem of insufficient characteristics. The present invention has been made to solve the above problems, and is a high frequency transformer suitable for use as a main transformer of a switching power supply because it exhibits low loss and high saturation magnetic flux density in a high frequency region. The purpose is to provide [Means for Solving the Problems] In order to solve the above problems, the present invention provides an Fe-based amorphous magnetic material having a composition of Fe86-xSi6B10Nbx and where 0.5 at.%≦x≦6 at.%. The magnetic core includes a magnetic core, and a winding wire wound around the magnetic core. [0012] Since the Fe-based amorphous magnetic material used in the present invention has a special composition, it has low eddy current loss in a high frequency region such as 1 MHz, and has a high saturation magnetic flux density. Therefore, a high frequency transformer with low loss and high saturation magnetic flux density in a high frequency region can be obtained, and by using this high frequency transformer, a switching power supply can be made smaller. The present invention will be explained in more detail below. FIG. 1 shows an embodiment of the high frequency transformer of the present invention. The high frequency transformer 1 of this embodiment is made of an Fe-based amorphous magnetic material, which will be described later, and has an outer iron type magnetic core 2 and a magnetic core 2. It is configured to include a wound wire 3. The Fe-based amorphous magnetic material forming the magnetic core 2 has a composition of Fe86-xSi6B10Nbx, and x represents the content of Fe and Nb, respectively.
The value of is in the range of 0.5 atomic %≦x≦6 atomic %. In the above composition, Fe is the central element responsible for magnetism. Since the saturation magnetic flux density tends to decrease as the amount of Nb added increases, it is preferable to reduce the Nb content in order to increase the saturation magnetic flux density. Moreover, the magnetic permeability changes significantly depending on the Nb content. In order to increase the magnetic permeability to 500 or more, it is necessary to adjust the Nb content to 0.5 to 6 at%. Furthermore, in order to increase the magnetic permeability to 1000 or more, the Nb content should be increased from 1 to 1.8 at%.
It is preferable to set it within the range of , or within the range of 3.1 to 5.3 atomic %. The Fe-based amorphous magnetic material can be manufactured by rapidly cooling a molten metal having the composition described above. To rapidly cool the molten metal, it is possible to adopt a roll quenching method in which the molten metal is dropped onto the surface of a rotating metal roll to obtain a ribbon state. It can also be obtained as a powder after being squirted into a liquid and rapidly cooled. In order to form the magnetic core 2 from these, the ribbons obtained as described above are laminated and processed into a tanzaku shape and stacked, or two cores wound in an annular shape are joined together. Good. Moreover, the magnetic core 2 of a desired shape can also be formed by compacting and sintering the powder obtained by the atomization method. Since the Fe-based amorphous material having the above composition has sufficiently excellent saturation magnetic flux density and magnetic permeability even in the rapidly cooled state, it is subjected to special heat treatment (annealing treatment) in a magnetic field.
Even if it is not carried out, it is suitable as a magnetic core of a high frequency transformer, and has the effect of promoting miniaturization and weight reduction of high frequency transformers. Note that if the alloy having the above composition is heat-treated (annealed) in a magnetic field as necessary, the magnetic properties can be further improved, and in that case, a high-frequency transformer 1 with even more excellent properties can be provided. . By the way, the Fe-based amorphous material used in the present invention does not need to be completely amorphous as a whole, and may contain a small amount of crystalline phase inside. can also be considered to be equivalent to the material of the present invention. [0021] A case in which a Fe-based soft magnetic material having the above composition is manufactured will be described below. A ribbon is formed by spouting a molten metal having a composition of Fe84-xSi6B10Nbx (where x is set to each value of 1, 2, 3, and 4) from a crucible onto a rotating metal roll through a nozzle and rapidly cooling it. A plurality of test pieces having a width of 1 mm and a thickness of 0.25 μm were obtained. x=1,2,3
, 4, and the results of the X-ray diffraction test are shown in FIG. For the diffraction test, an X-ray diffraction method using filtered Co Kα radiation was employed. From FIG. 2, a small peak diffracted from the (110) plane of the bcc phase was observed in the test pieces in which the x value of the Nb content was set to 1 and 2. Therefore, it was found that these compositions partially contained a crystalline phase and the rest consisted of an amorphous matrix. In addition, it was found that the test pieces in which the x value was set to 3 or 4 had an amorphous single-phase structure. Next, for each test piece having the above composition, 1MH
In addition to measuring the saturation magnetic flux density (Bs) at z, the (effective) magnetic permeability (μe) and coercive force (Hc) were also measured. The saturation magnetic flux density was measured using an applied magnetic field of 800 kA/m.
was carried out using a vibrating sample magnetometer under Moreover, the coercive force was evaluated from a DC B-H loop with a maximum magnetic field of 0.8 kA/m. Furthermore, the magnetic permeability was measured using a vector impedance analyzer in a driving magnetic field of 0.8 A/m from 1 kHz to 1
Measurements were made in the frequency range between 0 MHz. The results are shown in FIGS. 3(a) and 3(b). From the results shown in FIG. 3(a), the saturation magnetic flux density tends to decrease as the Nb content increases as a result of magnetic dilution. On the other hand, from the results shown in FIG. 3(b), it was found that the magnetic permeability had two peaks within the range of Nb content of 0.5 to 6 at%, but It showed an excellent magnetic permeability of 500 or more over the entire range. It has also been found that in order to make the magnetic permeability 1000 or more, it is preferable to set the Nb content in the range of 1 to 1.8 at % and 3.1 to 5.3 at %. Note that the sample piece with the composition Fe83Si6B10Nb1 showed a saturation magnetic flux density of 1.44T, and
The test piece with the composition 80Si6B10Nb4 was 1.17T.
showed a saturation magnetic flux density of Also, Fe82.5Si6B
A test piece with a composition of 10Nb1.5 showed a magnetic permeability of 1650, and a test piece with a composition of Fe80Si6B10Nb1 showed a magnetic permeability of 1800. Furthermore, a B-H loop showing the relationship between magnetic flux density and magnetic field strength was obtained for an amorphous material having a composition of Fe81Si6B10Nb3 and an amorphous material having a composition of Fe80Si6B10Nb4. The results are shown in Figure 4 (a
) and (b). The value of Hc is 3.4A for the former.
/m, and the latter was 5.8A/m. Furthermore, the shape of the B-H loop between the two amorphous alloys is shown in Figure 4 (a
) and (b), they are completely different, and the values of ΔB are greatly different. The reason for this is the induced magnetic anisotropy Ku
It can be presumed that this is because a high value of . [0028] In the test piece with the composition Fe80Si6B10Nb4, Bm is 1.17T and Br is 0.06T, so the value of ΔB is 1.11T, which is found to be a sufficiently large value. did. Furthermore, the significant increase in the μe value at a Nb content of 4 at% is shown in Figure 3(b).
It is thought that this is closely related to the excellent DC magnetic properties as revealed in . From this, it is possible to realize a significant reduction in loss in the MHz region from a DC B-H loop having an extremely low remanence ratio (Br/Bs). Incidentally, although the test piece was not subjected to any special heat treatment, it was found that even in the unheated state, it exhibited sufficient magnetic properties for use as a magnetic core of a converter. [0030] Also, Fe80S obtained in the above example
A test piece with a composition of i6B10Nb4 (Example 1) and (
The saturation magnetic flux density Br, Bs, and ΔB[Bs- Table 1 shows the measurement results of Br], Br/Bs, coercive force Hc, and magnetic permeability. (The following is a blank space) [Table 1] From the results shown in Table 1, the alloy of Example 1 has a higher saturation magnetic flux density (Bs) than the alloys of Comparative Examples 1 and 2, and The value of ΔB is also large, the coercive force (Hc) is an intermediate value, and the magnetic permeability is also an excellent value. Also, 1
The magnetic permeability value at MHz is the same for Co-based amorphous alloys and M
It is somewhat larger than n-Zn powder ferrite. As mentioned above, the magnetic material according to the invention has a large saturation magnetic flux density resulting in a high ΔB and has a small Br/Bs value. Furthermore, since the magnetic permeability is as high as 1800, 1MH
Even if eddy current loss increases to some extent when used at a high frequency such as Z, heat generation can be kept low and sufficient performance can be ensured. From the above, it has become clear that the magnetic material used in the present invention is suitable as a magnetic core material for a main transformer of a forward converter used at an operating frequency of 1 MHz. FIG. 5 shows another embodiment of the high frequency transformer of the present invention. The high frequency transformer 5 of this embodiment is equipped with an annular magnetic core 6 made of an Fe-based amorphous magnetic material having the composition described above. The winding 7 surrounds the magnetic core 6.
This embodiment is of a toroidal type, and the same effects as in the previously described embodiment can be obtained in this embodiment. [0035] In the previous embodiment, an example was explained in which the present invention was applied to an outer iron type and a toroidal type transformer, but it goes without saying that the present invention may be applied to transformers of various other shapes. It is. Effects of the Invention As explained above, the present invention provides Fe8
Since the magnetic core is made of an Fe-based amorphous material having a composition of 6-xSi6B10Nbx, it has sufficiently excellent saturation magnetic flux density and magnetic permeability. Furthermore, since the magnetic permeability is sufficiently high, even if some eddy current loss occurs in a high frequency region such as 1 MHz, the temperature rise can be suppressed to a low level and sufficiently high magnetic properties can be maintained. Therefore, according to the present invention, a high-performance high-frequency transformer can be provided, the main transformer can be made smaller and lighter, and the switching power supply can be made smaller. In addition, the Fe-based amorphous material used in the present invention exhibits soft magnetic properties suitable for the magnetic core of a high-frequency transformer without special heat treatment (annealing treatment) in a magnetic field, so it is easier to manufacture than conventional materials that require heat treatment. There is an effect that can be easily achieved. Note that if the alloy having the above composition is heat-treated (annealed) in a magnetic field as necessary, the magnetic properties can be further improved, and in that case, a high-frequency transformer with even more excellent properties can be provided.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of a high frequency transformer of the present invention.

FIG. 2 shows Fe86-xSi6B10 according to the present invention.
1 is a graph showing an X-ray diffraction pattern of an alloy having a composition of Nbx.

FIG. 3(a) is a graph showing the relationship between Nb content and saturation magnetic flux density in the same alloy. FIG. 3(b) is a graph showing the relationship between Nb content and magnetic permeability in the same alloy.

FIG. 4(a) is a graph showing a B-H loop of an alloy having a composition of Fe81Si6B10Nb3. Figure 4 (
b) is B- of the alloy with the composition Fe80Si6B10N4.
It is a diagram showing an H loop.

FIG. 5 is a sectional view showing another embodiment of a transformer to which the present invention is applied.

[Explanation of symbols]

1 High frequency transformer, 2. Magnetic core, 3 Winding wire, 5 High frequency transformer, 6 Magnetic core, 7 Winding wire.

Claims (1)

[Claims] Claim 1: A magnetic core made of an Fe-based amorphous magnetic material having a composition of Fe86-xSi6B10Nbx, where 0.5 atomic %≦x≦6 atomic %, and a winding wound around this magnetic core. A high frequency transformer characterized by: