JPH04249301A - Converter - Google Patents

Abstract

PURPOSE:To obtain the title converter which is suitably used as a high-frequency switching power supply by a method wherein at least one magnetic core out of a magnetic core for a choke coil and a magnetic core for a transformer is composed of an amorphous magnetic material whose composition is expressed as Fe86-xSi6B10Nbx. CONSTITUTION:At a converter A which is provided with a choke coil 5, a transformer 1, a capacitor 7 and diodes 3, 4, 5, at least one magnetic core out of a magnetic core for the choke coil 5 and a magnetic core 8 for the transformer 1 is composed of an Fe-based amorphous magnetic material whose composition is expressed as Fe86-xSi6B10Nbx and in which 0.5 atomic %<=x<=6 atomic %. For example, a converter A is constituted so as to be provided with a transformer 1, a power transistor 2, diodes 3, 4, 6, a choke coil 5 and a capacitor 7. A shell-type magnetic core 8 for the transformer 1 is constituted of said amorphous magnetic material whose eddy-current loss in a high-frequency region is small and whose saturation flux density is high.

Description

Description: FIELD OF INDUSTRIAL APPLICATION This invention relates to a converter incorporated in a switching power supply or the like. [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. Based on this background, switching power supplies, which are being miniaturized, tend to replace ordinary 50 Hz power supplies in fields such as power electronics. [0003] If we consider the components of a general switching power supply, we will see that they include a noise filter, a main transformer,
In addition to various magnetic components such as a saturable magnetic core, noise absorber, and smooth choke, the converter is equipped with magnetic components such as a transformer and a choke coil. Therefore, it can be seen that by increasing the frequency of these magnetic components, it is possible to realize miniaturization of these magnetic components. For this reason, miniaturization and higher performance of various components used in switching power supplies have become important issues. Due to the above-mentioned trends, 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. For this reason, great efforts have been made to reduce eddy current loss in the high frequency range in components used in switching power supplies. Conventionally, Mn--Zn ferrite has been mainly used as a core material for magnetic parts used in converters of switching power supplies of this type. [0006] However, among the above-mentioned conventional materials, none has been found to be excellent in both saturation magnetic flux density and magnetic permeability. In addition, conventional Co
Amorphous alloys such as Amorphous alloys are attracting attention as magnetic cores for converters, and are becoming widely used in some parts such as smooth chokes. However, most of the conventionally known Co-based amorphous alloys have a saturation magnetic flux density of less than 10,000 G, and there is a problem that the characteristics are insufficient for further improving the performance of noise filters. The present invention has been made to solve the above problems, and an object thereof is to provide a converter suitable as a converter for a high frequency switching power supply. Means for Solving the Problems In order to solve the above problems, the present invention provides a converter comprising a choke coil, a transformer, a capacitor, and a diode. , at least 1
Each of the magnetic cores is made of an Fe-based amorphous magnetic material having a composition of Fe86-xSi6B10Nbx, where 0.5 atomic %≦x≦6 atomic %. [0010] 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 magnetic core with low loss and high saturation magnetic flux density in the high frequency range can be obtained, which allows the transformer and choke coil to be made smaller and higher in performance. Therefore, by using the converter of the present invention, a switching power supply can be made smaller and have higher performance. [Embodiment] FIG. 1 shows an embodiment in which the converter of the present invention is applied to a forward converter. Converter A of this embodiment includes a transformer 1 and a power transistor 2.
, diodes 3, 4, and 6, a choke coil 5, and a capacitor 7. The transformer 1 is composed of a magnetic core 8, a primary winding 9, and a secondary winding 10. As the magnetic core 8, an Fe-based amorphous material, which will be described later, is used, and various types such as EI type and EE type are used. The Fe-based amorphous magnetic material constituting the magnetic core 8 has a composition of Fe86-xSi6B10Nbx, and x indicates 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 %. A power transistor 2 is connected to the primary winding 9, and the power transistor 2 is controlled to be turned on and off by controlling current flow to its base. In the converter A shown in FIG. 1, when a voltage is applied to the primary winding 9, a primary current flows and a magnetic flux is generated in the magnetic core 8.
An induced voltage is generated in the secondary winding 10. The magnitude of the induced voltage is proportional to the current change or magnetic flux change caused by the applied voltage. While the power transistor 2 is on, the current from the power transistor 2 flows through the transformer 1 and magnetic energy is accumulated, and the capacitor 7 is discharged. On the other hand, during the period when the power transistor 2 is off, the energy stored in the transformer 1 is transferred to the capacitor 7 via the choke coil 5.
is charged to. Therefore, when the power transistor 2 is repeatedly turned on and off, a predetermined DC voltage is obtained across the capacitor 7. That is, a DC output voltage that depends on the step-up ratio of the transformer 1 and the on/off time ratio (duty ratio) of the power transistor 2 is obtained across the capacitor 7 . FIG. 2 shows an example of a concrete structure of the transformer 1, which has an outer iron magnetic core 8, and has a structure in which a primary winding 9 and a secondary winding 10 are laminated. FIG. 3 shows the capacitor 4 and choke coil 5.
This figure shows a specific structural example of element B that integrates the following elements. This element B includes a terminal rod 12 provided in the center, pipes 13 and 14 inserted through the terminal rod 12, a coating layer 15 that covers the pipes 13 and 14, and a coating layer 15 that covers the outside of the coating layer 15. mold layer 16 and mold layer 16
A cylindrical body 17 buried therein, a metal shield case 18 provided to cover the outer circumference of the mold layer 16, and a metal shield case 18 buried in the mold layer 16 to connect the cylindrical body 17 and the terminal rod 12. It is configured to include a connection board 19. The terminal rod 12 is made of a highly conductive metal material such as annealed copper, the pipes 13 and 14 are made of an Fe-based amorphous material having the composition described above, the coating layer 15 is made of an insulator, and the mold layer 16 is made of resin, the cylindrical body 17 is made of dielectric, and the shield case 18 and the connecting piece 1 are made of resin.
9 is made of a metal with good conductivity. The covering layer 15 is an insulator made of heat-shrinkable silicone resin or the like. The cylindrical body 17 is a dielectric material made of BaTiO3-based ceramics, etc.
Electrodes, such as thin silver films, are formed on both the top and bottom surfaces. A capacitor is constructed by covering this cylindrical body 17 with a mold layer 16. By the way, 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 pipes 13 and 14 from the above material, the ribbon obtained as described above may be wound and processed into a pipe shape. Further, the pipes 13 and 14 or the magnetic core 8 can also be formed by compacting the powder obtained by the atomization method into a pipe shape and sintering it. The Fe-based amorphous material with the above composition has sufficiently excellent saturation magnetic flux density and magnetic permeability even in the rapidly cooled state, so it can be subjected to special heat treatment (annealing treatment) in a magnetic field.
It is suitable as a magnetic core even if it is not performed, and has the effect of promoting high performance of the magnetic core. Incidentally, 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 magnetic core with even more excellent properties can be provided. By the way, the Fe-based amorphous material used in the present invention does not have to be a complete amorphous phase 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. A case in which a ribbon of Fe-based soft magnetic material having the above composition is manufactured will be described below. Fe84-xSi6
A molten metal with a composition of B10Nbx (x = 1, 2, 3, 4) is jetted from a crucible onto a rotating metal roll through a nozzle and rapidly cooled to form a ribbon with a width of 1 mm. A plurality of test pieces with a thickness of 0.25 μm were obtained. FIG. 4 shows the X-ray diffraction test results of each test piece manufactured by setting x to each value of 1, 2, 3, and 4. For the diffraction test, an X-ray diffraction method using filtered Co Kα radiation was employed. From FIG. 4, 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, the saturation magnetic flux density (Bs) was measured, and the effective magnetic permeability (μe) and coercive force (Hc) at 1 MHz were also measured. Measurements of saturation magnetic flux density were performed using a vibrating sample magnetometer under an applied magnetic field of 800 kA/m. Moreover, the coercive force was evaluated from a DC BH loop with a maximum magnetic field of 0.8 kA/m. Furthermore, the magnetic permeability was measured in the frequency range between 1 kHz and 10 MHz using a vector impedance analyzer in a driving magnetic field of 0.8 A/m. The results are shown in Figure 5(a).
, (b). From the results shown in FIG. 5(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. 5(b), it was found that the magnetic permeability had two peaks within the range of Nb content of 0.5 to 6 at%; 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 Fe80Si6B10Nb4 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 6 (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 6 (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 assumed that this is because a high value of . [0032] 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. In addition, the significant increase in μe value at Nb content of 4 at% is shown in Fig. 5(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). By the way, although the test piece was not subjected to any special heat treatment, it was found that it exhibited sufficient magnetic properties as a magnetic core even in the unheated state. [0034] 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. [Table 1]
From the results shown in Table 1, the material of Example 1 has a larger saturation magnetic flux density (Bs) and a larger value of ΔB than the alloys of Comparative Examples 1 and 2, and has an intermediate coercive force (Hc). value, and the magnetic permeability is also an excellent value. Moreover, the value of magnetic permeability at 1 MHz is somewhat larger than that of Co-based amorphous alloy and Mn-Zn powder ferrite. As mentioned above, the magnetic material according to the present invention has a large saturation magnetic flux density resulting in a high ΔB,
It has a small Br/Bs value. Furthermore, the magnetic permeability is 1800
Since it is large, it is used at a high frequency such as 1MHz,
Even if eddy current loss increases to some extent, 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 converter used at an operating frequency of 1 MHz. Incidentally, in the above embodiment, an example was explained in which both the choke coil 5 and the magnetic core 8 of converter A were formed of the Fe-based amorphous material having the above composition, but only one of them may be formed of the Fe-based amorphous material. Of course. Effects of the Invention As explained above, the present invention provides Fe8
Since at least one of the magnetic core of the transformer and the magnetic core of the choke coil is made of an Fe-based amorphous material having a composition of 6-xSi6B10Nbx, these magnetic cores have sufficiently excellent saturation magnetic flux density and magnetic permeability. Furthermore, since the magnetic core has a sufficiently high magnetic permeability, 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 converter including a high-performance transformer and a choke coil can be provided, and the converter can be improved in performance, and the switching power supply can be downsized. In addition, the Fe-based amorphous material used in the present invention exhibits soft magnetic properties suitable for the magnetic core of transformers and choke coils without special heat treatment (annealing treatment) in a magnetic field. It has the advantage of being easier to manufacture than other materials. In addition, if the Fe-based amorphous material having the above composition is heat-treated (annealed) in a magnetic field as necessary, the magnetic properties can be further improved. converter can be provided.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of a converter of the present invention.

FIG. 2 is a sectional view showing a structural example of a transformer suitable for use in the converter.

FIG. 3 is a sectional view showing a capacitor and choke coil suitable for use in the converter.

FIG. 4 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. 5(a) is a graph showing the relationship between Nb content and saturation magnetic flux density in the same alloy. FIG. 5(b) is a graph showing the relationship between Nb content and magnetic permeability in the same alloy.

FIG. 6(a) is a graph showing a BH loop of an alloy having a composition of Fe80Si6B10Nb4. Figure 6 (
b) is B of the alloy with the composition Fe80Si6B10Nb4
- It is a diagram showing a H loop.

[Explanation of symbols]

A converter, 1 transformer, 2 power transistor, 3,
4, 6 diode, 5 choke coil, 7 capacitor, 8
Magnetic core, 9 Primary winding, 10
Secondary winding.

Claims (1)

[Claims] [Claim 1] A converter comprising a choke coil, a transformer, a capacitor, and a diode,
At least one of the choke coil magnetic core and the transformer magnetic core is Fe86-xSi6B10Nbx
1. A converter comprising an Fe-based amorphous magnetic material having a composition of 0.5 atomic %≦x≦6 atomic %.