JPH0324761B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic core suitable for constructing a chiyoke coil that is used with superimposed direct current. For example, in a chi-yoke coil that is used with DC current superimposed, such as a chi-yoke coil or an output filter of a switching power supply, in order to improve the DC superposition characteristic, as illustrated in Fig. 1,
Air gap in part of closed magnetic circuit such as core center part
It is common to use a ferrite magnetic core provided with Ga. When such an air gap Ga is provided,
As shown in Figure 2, the inductance L of the coil for a certain width of change in ampere turns IN
This is because a flat DC superposition characteristic in which the voltage is constant can be obtained. Note that the DC superposition characteristics are based on the air gap.
As Ga increases, the curve shifts as shown in A ₁ →A ₂ → ₃ . However, a switching regulator using a chiyoke coil using this magnetic core has the disadvantage that the output voltage becomes high when the load current is small, resulting in poor output stability. Figure 3 is a circuit diagram of a conventionally known general single-stone forward converter, showing the primary winding of the conversion transformer T.
A DC voltage E _IN is supplied to N ₁ via a switch circuit S, and one end of the secondary winding N ₂ is connected to one end of a capacitor C via a diode D ₁ and a choke coil L using the magnetic core. Secondary winding N ₂
The other end is connected to the connection point between the diode _D1 and the choke coil L via the diode _D2 , and is also connected to the other end of the capacitor C, and another DC voltage ₀ is applied to both ends of the capacitor C. is configured to output. In such a circuit, the relationship between load current ₀ and output voltage ₀ is as shown in Figure 4. When load current ₀ is small, that is, in the region where the current flowing through the choke coil L is discontinuous, the output voltage ₀ is It gets expensive. The region of discontinuous current is I ₀ ≦ (T - τ)V ₀ /2L T: Period of turning on/off switch S τ: ON period of switch S L: Inductance of the current of switch S, and therefore the output In order to improve stability, it is possible to increase the inductance L to narrow the discontinuous region of the current, or add a dummy load to the output terminal, but in the former case, the copper loss due to the increase in the number of turns of the current In the latter case,
It has the disadvantage of increasing power consumption and heat generation, and there has been a strong desire to improve it. The present invention eliminates the above-mentioned conventional drawbacks, and makes it possible to suppress the output voltage at light loads, improve output stability, and reduce loss when used in a choke coil or an output filter of a switching power supply. The purpose is to provide magnetic cores. In order to achieve the above object, one of the inventors of the present invention devised and previously proposed a composite magnetic core having a special configuration. (Utility Application No. 56-74915) The present invention was obtained as a result of intensive research efforts into the magnetic materials constituting the composite magnetic core. The present invention was based on the knowledge that a composite magnetic core with suitable characteristics can be obtained by using a magnetic ribbon having a certain composition. That is, the present invention provides a chiyoke coil using a magnetic core having a central leg core located in parallel and integrally provided between side magnetic cores, in which a gap is provided in the middle leg core, and a gap is provided around the gap. is a Chiyoke coil which is wound with a magnetic ribbon made of amorphous material represented by the following compositional formula, and has a cut portion in a part in the circumferential direction of the magnetic ribbon, the formula: F _x B _y However, in the above formula, X+Y=100 at%, of which Y is 10 to 35 at%. When y is smaller than 15% or larger than 35%, it is difficult to make it amorphous, and it is not suitable for high-yield production. Also, a part of B is Si
By substituting with , amorphization becomes easy,
Corrosion resistance is increased and changes over time are also improved, resulting in better properties. The amount to be replaced depends on the composition.
When written as Fex(SipBq)y, 0.01≦p≦70% is appropriate. When p<0.01%, it is difficult to obtain this effect, and when p>70%, conversely, it becomes difficult to make amorphous. Furthermore, by substituting a part of B and Si with other metalloid elements, such as P and C, changes over time can be further improved and good characteristics can be obtained. The amount of substitution is 0.01%≦r≦10 when the composition is written as Fex(SipBqXr)y (where X=P, C, or at least one other metalloid element)
%, more preferably 0.01%≦r≦5%. When r<0.01%, it is difficult to obtain this effect, and when r>5% or r>10%, problems arise in terms of magnetic properties. DESCRIPTION OF THE PREFERRED EMBODIMENTS The content of the present invention will be specifically described below with reference to the accompanying drawings, which are examples. FIG. 5A is a front sectional view of the magnetic core according to the present invention, and FIG. 5B is B ₁ - of FIG. 5A.
It is a cross-sectional view on line _B1 . In the present invention, E
It is possible to use a magnetic core such as a type core, a pot type core, etc., which has a middle leg core and side cores located parallel to the left and right sides or the periphery of the middle leg core. In this embodiment, an E-shaped core is used, which is composed of a middle leg magnetic core part 4a and side magnetic core parts (side leg parts) located on the left and right sides of the middle leg magnetic core part 4a.
The two E-type cores 3 and 4 are combined to form an air gap Ga between the middle leg magnetic cores 3a and 4a, and a thin magnetic material 5 is attached around the air gap Ga. In this way, by providing the gap and the magnetic ribbon in the middle leg magnetic core, it is possible to improve the characteristics by adjusting only one location. As the magnetic material 5, a magnetic ribbon having the above composition and being substantially amorphous is used. Further, as a method of attaching the magnetic body 5 around the air gap Ga, there is a method of fitting the middle leg magnetic core parts 3a and 4a from both sides into the inner diameter part of the magnetic body 5 which is previously formed into a cylindrical shape, or a method shown in FIG. like,
A method of winding an appropriate number of layers of the magnetic material 5 formed in a sheet or thin plate shape using the above-mentioned magnetic material around the middle magnetic core portions 3a and 4a constituting the air gap Ga may be considered. Furthermore, in the embodiments shown in FIGS. 5A and 5B and FIG. 6, the magnetic body 5 is formed in an endless shape, but as shown in FIG. A method of forming an end having a cut portion (gap g ₁ ) is also effective. When the magnetic body 5 is formed in an endless shape, the magnetic body 5 forms a short circuit with respect to the electromotive force generated in the magnetic body 5 due to the magnetic flux flowing between the middle leg magnetic cores 3a and 4a. However, if the magnetic body 5 is provided with a gap _g1 as described above and has an end shape,
The gap is applied to the electromotive force generated in the magnetic body 5.
This is because an open circuit is formed due to g ₁ , reducing loss and heat generation. Note that the gap _g1 is not limited to a void, but may also be formed of an insulating material such as an insulating resin. It is also preferable to provide an electrically insulating layer on the surface of the magnetic ribbon. As mentioned above, if the gap Ga has the above-mentioned composition and is attached with a substantially amorphous magnetic thin strip, when a chi-yoke coil is constructed using the magnetic core, it will not work under light load. Although the effect of rapidly increasing the inductance is obtained, this effect is greater than when the magnetic material disclosed in Utility Model Application No. 56-74915 is used as the magnetic body 5. (Experiment A) Figure 8 is a current-inductance characteristic diagram of each York coil with a different magnetic core structure.The horizontal axis shows the coil current (A), and the vertical axis shows the inductance L.
(mH) is taken. Curve A is the characteristic of a choke coil using a conventional magnetic core, and curve B is the characteristic of a gap coil.
Characteristics when using a magnetic core with a magnetic material 5 made of composite resin ferrite wrapped around Ga, curve C
is around the gap Ga (Fe _0.4 Co _0.3 Ni _0.3 ) ₈₀
(Si _0.1 B _0.9 ) Characteristics when using a magnetic core wrapped with a magnetic material 5 made of an amorphous alloy having a composition of ₂₀ .
All are comparative examples. Curve D represents the characteristics of the present invention when a magnetic core having a composition of Fe ₈₀ (Si _0.5 B _0.5 ) ₂₀ and wrapped with an amorphous magnetic material 5 manufactured by a high-speed quenching method is used. are shown respectively. The amorphous ribbon of curve D has the same thickness, shape, and weight as the amorphous ribbon of curve C, and is wound around the gap portion. (Experiment B) By changing the composition of the amorphous magnetic ribbon, magnetic material 5
A chiyoke coil having almost the same DC current resistance characteristics as in Experiment A was created. Table 1 shows the inductance values when the DC current is 0.03A.

【table】

[Table] (Experiment C) (4), (5), (7), (8), (9), (11), (
12)
A life test of 1000 hours at 120°C was conducted using an amorphous material with a composition of The deterioration of magnetic permeability is (5), (9)
5% or more, (4) and (11) ~5%, all others 5%
It was below. As is clear from these experiments, when a substantially amorphous magnetic ribbon having the composition of the present invention is used as the magnetic material, a magnetic core with very good characteristics can be obtained, and the coil current can be reduced. However, as the load becomes lighter, the inductance L tends to increase rapidly. As described above, by using the magnetic ribbon of the present invention, it is possible to most effectively handle light loads, especially to rapidly increase the inductance L. Therefore, when the magnetic core according to the present invention is used to configure a chiyoke coil or an output filter of a switching power supply, As shown in Figure 9, the output voltage ₀ , which conventionally had a tendency to rise abnormally as shown in (b) at light loads, is suppressed as shown in (c) by increasing the inductance L. Therefore, the output stability is very good. In addition, since the rise in output voltage during light loads is small, even when a dummy load is added, power consumption and heat generation are reduced, a small capacity dummy load is sufficient, and heat dissipation measures can be easily taken. It will be done.
Similar effects can be obtained when used in a push-pull converter other than a forward converter, for example. As described above, the present invention is characterized in that a magnetic core having a gap in part is provided with a substantially amorphous magnetic ribbon having a specific composition near the gap. Like York coils and output filters of switching power supplies,
When used for a coil where direct current is superimposed, it is possible to provide a magnetic core that can suppress increases in output voltage and frequency during light loads, improve output stability, and reduce loss. .

[Brief explanation of drawings]

Figure 1 is a front view of a conventional magnetic core, Figure 2 is its DC superimposition characteristic diagram, Figure 3 is a circuit diagram of a general single-stone forward converter, and Figure 4 is a diagram of a conventional magnetic core. Fig. 5A is a front sectional view of the magnetic core according to the present invention, and Fig. 5B is B ₁ -B ₁ of Fig. 5A.
6 and 7 are cross-sectional views along the line, and FIG. 8 is a cross-sectional view of another embodiment of the magnetic core according to the present invention.
The figure is a diagram showing the current-inductance characteristics of a coil using the magnetic core according to the present invention in comparison with a conventional one, and Figure 9 is an output current-output voltage characteristic diagram when using the magnetic core according to the present invention. be. Ga...gap, 5...magnetic material.

Claims (1)

[Scope of Claims] 1. A chi-yoke coil using a magnetic core having a central leg magnetic core located in parallel and integrated between side magnetic cores, in which a gap is provided in the middle leg magnetic core, and the gap is provided in the middle leg magnetic core. is wound around the periphery of a magnetic ribbon made of amorphous material having the composition formula below, and the magnetic ribbon has a cut portion at a portion in the circumferential direction. . Formula F _x B _y However, in the above formula, x+y=100 at%, of which y is 15 to 35 at%. 2. In a chain coil using a magnetic core having a middle leg core located in parallel and integrated between side magnetic cores, a gap is provided in the middle leg core, and the area around the gap has the following composition. What is claimed is: 1. A chiyoke coil that is wound with a magnetic ribbon made of amorphous material represented by the formula, and has a cut portion in a part of the magnetic ribbon in the circumferential direction. Formula Fe _x (Si _p S _q ) _y However, in the above formula, x+y=100 at%, of which y is 15 to 35 at%. Furthermore, p+q=
100%, of which p is 0.01 to 70%. 3. In a chain coil using a magnetic core having a central leg core located in parallel and integrated between side magnetic cores, a gap is provided in the middle leg core, and the area around the gap has the following composition. A Chiyoke coil is wound with an amorphous magnetic ribbon shown by the formula, and has a cut section in the circumferential direction of the magnetic ribbon.Formula Fe _x (Si _{p B q _} Furthermore, p+q+r=
100%, of which p is 0.01 to 70% and r is
It is 0.01-10%.