JPS6119097B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an inductance element suitable for use in switching regulators and the like.

(Background of the Invention) Conventionally, when smoothing a pulsating voltage in an inductance element such as a chiyoke coil, it has been thought that it is necessary to have an almost constant inductance as shown in Figure 1 from a small value to a large value of the smoothed current. An inductance element was used that was large, had a magnetic core made of a soft magnetic material, and was designed so that the saturation current was larger than the maximum value of the smoothed current. However, in this case, the dimensions of the inductance element are LI ² (L is the inductance, I is the saturation current)
Since it is almost proportional to , it has the disadvantage of becoming large.

(Prior Art) Therefore, it has been proposed to configure the magnetic circuit with an EI magnetic core and provide an air gap in the central magnetic leg to prevent the magnetic core from being saturated even when the current is large beyond a certain level, thereby reducing the size of the magnetic circuit. However, in this case, it is not possible to use a standard product as the E-type magnetic core, and processing is troublesome, and it is difficult to adjust and set so as to obtain predetermined characteristics. Furthermore, providing an air gap in the central magnetic leg increases the magnetic resistance of the magnetic circuit, resulting in a disadvantage that the inductance in a low current region is lower than when there is no air gap.

Furthermore, an inductance element that provided a magnetic bias by installing a permanent magnet in the air gap of the magnetic core was developed in the 1970s.
No. 5501, Japanese Utility Model Publication No. 54-7319, and Japanese Patent Publication No. 54-32696, but since permanent magnets are used, the cost is high and there are problems such as heat generation of the permanent magnets.

(Objective of the Invention) An object of the present invention is to eliminate the above-mentioned conventional drawbacks and to provide a small inductance element suitable for smoothing pulsating voltage.

(Main points of the structure of the invention) A feature of the present invention is that in a magnetic core assembly that combines a first magnetic core having a central magnetic leg and side magnetic legs, and a second magnetic core that is in contact with these magnetic legs, The second magnetic core is divided into a first magnetic body that is in direct contact with the first magnetic core, and a second magnetic body that is opposed to the first magnetic body with a nonmagnetic layer interposed therebetween.

(Embodiments of the Invention) Hereinafter, embodiments of an inductance element according to the present invention will be described with reference to the drawings.

FIG. 2 shows a first embodiment of the invention. In this figure, the inductance element is an E-type soft magnetic material 1
and the two I-type soft magnetic bodies 2 and 3 form an EI magnetic core, and a non-magnetic layer 4 such as a non-magnetic material or an air gap is provided between the I-type soft magnetic bodies 2 and 3, and the center of the E-type soft magnetic body is Magnetic leg 1a
A winding 5 is applied to the wire. Here, the I-type soft magnetic body 2 is in direct contact with the central magnetic leg 1a and the side magnetic leg 1b of the E-type soft magnetic body 1, and preferably has a sufficiently larger magnetic permeability than the magnetic bodies 1 and 3. The soft magnetic body 3 is structurally integrated with the I-type soft magnetic body 2 via the nonmagnetic layer 4.

Next, the operation of the first embodiment will be explained with reference to the operation diagram in FIG. 3 and the characteristic diagram in FIG. 4. however,
The E-type and I-type soft magnetic bodies 1, 2, and 3 are ferrite cores of the same characteristics as EI-30 manufactured by Tokyo Denki Kagaku Kogyo Co., Ltd., and the E-type soft magnetic body 1 is a standard product and the I-type soft magnetic body 2 is a standard product. The thickness was 1 mm, the I-type soft magnetic body 3 was 4 mm thick, and the nonmagnetic layer 4 was 1 mm thick.

Now, the operation can be roughly divided into a region where the current is small, less than 1A, and a region where the current is larger. First, in a region where the current is small, the magnetic flux φi due to the winding 5 passes through the magnetic body 2 of the two I-type soft magnetic bodies 2 and 3, and the inductance becomes a large value (approximately 500 μH).

Next, the current flowing through winding 5 is large (1A or more)
When it becomes , the magnetic flux φi increases, and the magnetic flux passing through the I-type soft magnetic body 2 also increases. As a result, since the I-type soft magnetic body 2 has a thin plate shape, its saturation magnetic flux density will be exceeded, and the magnetic resistance of the I-type soft magnetic body 2 will be equivalent to the state where no magnetic body exists. As a result, the E-type soft magnetic body 1 and I
The EI magnetic core has a large equivalent air gap G formed by the soft magnetic material 3, and the inductance element has a small value (approximately 150 μH). In this state, winding 5
After the magnetic flux φl starts to pass through the I-type soft magnetic body 3, it continues until the magnetic flux due to the current exceeding 20 A exceeds the saturation magnetic flux density of the I-type soft magnetic body 3.

As explained above, according to the first embodiment, a large inductance value can be obtained in a region where the smoothed current is small, and a small inductance value can be obtained in a region where the smoothed current is large. A suitable inductance element can be realized. Moreover, by changing the thickness of the I-type soft magnetic bodies 2 and 3, arbitrary characteristics can be obtained. Furthermore, if used in a switching regulator, when the load is light, the current flowing through the choke coil will be discontinuous and the filter effect will be lost, but if this current is defined as the critical current _IUL , then _IUL ≧Ein-Eout /2L·t _ON (where, Ein: input DC voltage, Eout: output DC voltage, t _ON : transistor on time, L: inductance of the choke coil). Therefore, in a switching regulator, in order to exceed the critical current _IUL , a dummy resistor is usually connected to the output terminal to flow a dummy current. However, since the inductance element of the present invention has a large inductance under light loads, the critical current I _UL may be small. As a result, it is possible to reduce the dummy load and improve efficiency.

FIG. 5 shows a second embodiment of the invention. In this figure, the inductance element constitutes a magnetic circuit with a pot-shaped magnetic core 10 made of soft magnetic material and two disc-shaped soft magnetic materials 11 and 12 that are divided into two disc-shaped magnetic cores.
A non-magnetic layer 13 such as a non-magnetic material or an air gap is provided between the disc-shaped soft magnetic bodies 11 and 12, and a winding 14 is provided on the central magnetic leg 10a of the pot-shaped magnetic core 10. Here, the disc-shaped soft magnetic body 11 is in direct contact with the central magnetic leg 10a and the cylindrical side magnetic leg 10b of the pot-shaped magnetic core 10, and the disc-shaped soft magnetic body 12 is connected to the disc-shaped soft magnetic body 12 through the nonmagnetic layer 13. It is structurally integrated with the soft magnetic body 11.

The second embodiment described above also exhibits a high inductance value until the disc-shaped soft magnetic body 11 is saturated, and exhibits a small inductance value when the current exceeds that value, thereby achieving the same effect as the first embodiment described above. I can do it.

(Effects of the Invention) As described above, according to the present invention, it is possible to obtain a large inductance value in a small current region and a small inductance value in a large current region, making it possible to obtain a small inductance value for a switching regulator, etc. A suitable inductance element can be realized.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the relationship between current and inductance of a conventional inductance element, FIG. 2 is a perspective view showing a first embodiment of the inductance element according to the present invention, FIG. 3 is a diagram of the same operation, and FIG. The figure is a characteristic diagram showing the relationship between current and inductance in the case of the first embodiment, and FIG. 5 is an exploded perspective view showing the second embodiment of the present invention. 1... E type soft magnetic material, 2, 3... I type soft magnetic material, 4, 13... Nonmagnetic layer, 5, 14... Winding wire,
10... Pot-shaped magnetic core, 11, 12... Disc-shaped soft magnetic material.

Claims (1)

[Claims] 1. A first magnetic core having a central magnetic leg and side magnetic legs;
In an inductance element in which a magnetic circuit is configured by combining these magnetic legs with a second magnetic core that is in contact with the magnetic legs, and a wire is wound around the central magnetic leg, the second magnetic core is connected to the central magnetic core of the first magnetic core. An inductance element comprising a first magnetic body in direct contact with a leg and a side magnetic leg, and a second magnetic body facing the first magnetic body with a nonmagnetic layer interposed therebetween. 2. The inductance element according to claim 1, wherein the first magnetic body is a soft magnetic body having higher magnetic permeability than the first magnetic core and the second magnetic body.