JP2637184B2 - Core for oscillation transformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention] (Industrial application field) The present invention relates to a core for an oscillation transformer used for a switching power supply or the like.

(Prior Art) In recent years, switching power supplies that can be smaller and lighter than conventional series dropper power supplies are frequently used as stabilized power supplies for various electronic devices and the like.

This switching power supply has suitable switching elements and magnetic characteristics (hysteresis characteristics) of the core for the oscillation transformer.
There is a configuration in which a DC on the input side is temporarily converted into a high-frequency AC using the above, and then converted again into a DC by a rectifier circuit to obtain an output.

As a material of a core for an oscillation transformer used in such a switching power supply, a Fe-Ni alloy, ferrite, an amorphous magnetic alloy, or the like has been conventionally used.

(Problems to be Solved by the Invention) By the use of such a switching power supply, the size of the power supply has been reduced as compared with the conventional series power supply, but it is still larger and heavier than other devices. Therefore, as a method for further reducing the size, for example, there is a method of increasing the oscillation frequency and thereby reducing the size of the transformer, the coil, and the like.

However, among the materials of the magnetic core for the oscillation transformer used in the conventional switching power supply, the Fe-Ni alloy has a large iron loss and cannot increase the oscillation frequency.
There is a problem that the characteristics with respect to the temperature are poor, and the oscillation frequency is remarkably changed due to the temperature rise of the circuit. Further, the amorphous magnetic alloy has low iron loss and good characteristics with respect to temperature, but has a problem that oscillation becomes unstable.

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem, and it is possible to increase the oscillation frequency, stably oscillate, and further downsize the power supply for an oscillation transformer. The purpose is to provide.

[Constitution of the Invention] (Means for Solving the Problems) The core for an oscillation transformer of the present invention is a wound body of an amorphous magnetic alloy ribbon, and the surface roughness R _f of the amorphous magnetic alloy ribbon is obtained. But
It is characterized by being 0.3 or more. Where R _f is JIS B
10-point average roughness at a standard length of 2.5 mm specified in 0601,
And the plate thickness is R _z , T, respectively, and is a parameter characterizing the roughness determined by R _f = R _z / T.

In the present invention, the surface roughness R _f of the amorphous magnetic alloy ribbon is 0.
The reason for setting it to 3 or more is that if it is less than 0.3, the squareness ratio at the oscillation frequency exceeds 97%, making oscillation unstable or impossible. Although the cause is not clear, it is considered to be due to shape anisotropy due to surface roughness. The upper limit of R _f is not particularly limited. Therefore, the amorphous magnetic alloy ribbon may have a hole, and the magnetic property may be such that the squareness ratio at the oscillation frequency is 80% or more.

As means to fall within the range of the present invention having a thin ribbon surface, it is necessary to control production conditions such as a roll material, a roll surface temperature, and a melt temperature. When the roll surface is used in the atmosphere, it depends particularly on the entrapment of air bubbles.

Amorphous magnetic alloy used in the present invention have the general formula: M _{a M'b} X _c (wherein, M is one or selected from Fe, Co and Ni
M ′ represents one or more elements selected from the group IIIa, IVa, Va, VIa, and X represents B, S
represents one or more elements selected from i, P, C, Ge, and a + b + c = 1,0.60 ≦ a + b ≦ 0.88,0.005 ≦ b
≤0.1, 0.12≤c≤0.30. )), And preferably represented by the general formula: (Co _1-gh Fe _g M _h ) _100-j (Si _1-i B _i ) _j M: Ti, V, Cr, Mn, Cu, Ni, At least one selected from Nb, Mo, W
A Co-based amorphous alloy represented by the following formula: 0.005≤g≤0.10≤h≤0.08 0.3≤i≤0.923≤j≤32.

Among them, those having a Curie temperature of 200 ° C to 280 ° C are suitable. If the Curie temperature is lower than 200 ° C., the rate of change of the saturation magnetic flux density with respect to the operating temperature becomes 20% or more, whereby the oscillation frequency also changes and becomes impractical. This is because the oscillation frequency f of the switching power supply is determined by the saturation magnetic flux density Bs, the cross-sectional area S, the number of turns N, and the input voltage E of the core of the transformer used, and is determined by the following equation. This is because the magnetic flux density is determined by the Curie temperature, that is, the composition of the material.

If the Curie temperature is 280 ° C. or higher, the loss at the oscillation frequency is large, leading to a decrease in power supply efficiency.

Among such amorphous magnetic alloys, a Co-based amorphous magnetic alloy having a saturation magnetostriction constant of 2 × 10 ⁻⁶ or less in absolute value is particularly suitable.

The magnetic core for an oscillation transformer of the present invention is manufactured, for example, as follows.

That is, first, a thin plate of an amorphous magnetic core is wound and laminated,
Heat treatment is performed at a temperature of 350 ° C. to 500 ° C. according to a conventional method, and then the case is completed by putting it in a case or by using a method such as resin coating.

(Action) By using an amorphous magnetic alloy ribbon having a surface roughness _Rf of 0.3 or more in the oscillation transformer core of the present invention, it is possible to realize an oscillation transformer having a stable oscillation state at the operating frequency and change with time. There is almost no.

(Example) Next, an example of the present invention is described.

Example 1 First, an amorphous magnetic alloy having a composition of (Co _0.94 Fe _0.05 Nb _0.01 ) ₇₂ (Si _0.6 B _0.4 ) ₂₈ [Curie temperature 260 ° C.] was used. A thin ribbon was produced. These were wound around a predetermined winding jig and laminated to form a core having an outer diameter of 8 mm, an inner diameter of 6 mm, and a height of 4.5 mm.
Next, after performing a heat treatment in a nitrogen gas atmosphere at 400 ° C. for 90 minutes, the resultant was coated with a resin and packaged to obtain a magnetic core for an oscillation transformer.

An oscillation transformer was manufactured using each of the magnetic cores thus obtained, and a circuit test was performed using a Jensen oscillation circuit. The oscillation frequency was set to 100 KHz. The average temperature of the magnetic core during the test was 50 ° C, and the maximum temperature was
70 ° C. The room temperature was 25 ° C.

The result is shown in FIG. This shows that the circuit efficiency is as high as 85% or more when the surface roughness is 0.3 or more.

Examples 2 to 7 After preparing an amorphous magnetic alloy ribbon having the alloy composition shown in Table 1 in the same manner as in Example 1, the obtained ribbon was wound and heat-treated to obtain a core for an oscillation transformer.

The Curie temperature (T _c ) of each alloy is determined by the inductance method.
(Bs (120) / Bs (20)). Further, the circuit efficiency (η) is applied to the same oscillation circuit as in the first embodiment, and the circuit efficiency (η) is 12
Aging was evaluated at 0 ° C. for 1000 hours.

The results are shown in Table 1, where _Tc is the surface roughness.
The magnetic core having _Rf within the range of the present invention has Bs (120) / Bs (20) of 80% or more and is stable against aging.

[Effects of the Invention] As described above, according to the core for an oscillation transformer of the present invention, by limiting the surface roughness at the oscillation frequency to 0.3 or more, stable oscillation can be obtained even in a high frequency range, and the change over time can be obtained. With very little, this allows a further miniaturization of the power supply.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the surface roughness of the core for an oscillation transformer and the circuit efficiency according to the embodiment of the present invention.

 ────────────────────────────────────────────────── (7) Continuation of the front page (72) Inventor Masami Okamura 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside the Toshiba Yokohama Office Co., Ltd. 6508 (JP, A) JP-A-58-56307 (JP, A) JP-A-59-177902 (JP, A) JP-A-62-65404 (JP, A) Actually open, 56-56608 (JP, U)

Claims (1)

(57) [Claims] 1. A core for an oscillation transformer, which is formed by winding an amorphous magnetic alloy ribbon having a surface roughness _Rf of 0.3 or more. (However, R _f is the standard length 2.5 specified in JIS B0601.
A parameter characterizing the roughness obtained from _Rf = _Rz / T, where _Rz and T are the ten-point average roughness in mm and the average plate thickness obtained from the weight of the ribbon, respectively. )