JPH0645151A - U-shaped ferrite core - Google Patents

Abstract

(57) [Summary] [Purpose] Relaxing the concentration of magnetic flux in the inner corner,
As a result, iron loss and heat generation can be reduced, the average magnetic flux can be increased, the performance and reliability of the flyback transformer can be improved, and the magnetic circuit in the outer peripheral corner portion can be eliminated to reduce the size of the device. Obtain a letter-shaped ferrite core. [Structure] In a U-shaped ferrite core 2 in which legs 2b extend in parallel from both ends of a base 2a, an inner peripheral corner 2c
1 mmR or more or 1 mmC or more overhanging portion 11 is formed on the outer peripheral corner portion 2d, and the average magnetic flux density of the leg portion is 30%.
The cutout portion 12 is formed in the following portion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a U-shaped ferrite core having two windings wound in a butt shape and used for a flyback transformer of a television receiver or the like.

[0002]

2. Description of the Related Art FIG. 4 is a front view showing a flyback transformer partially cut away, FIG. 5A is a front view showing a conventional U-shaped ferrite core in a butted state, and FIG.
A sectional view, (c) is a plan view of one U-shaped ferrite core. In the figure, 1 is a flyback transformer, 1
From a pair of U-shaped ferrite cores 2, a winding portion 3 wound around the U-shaped ferrite cores 2, a gap spacer 4 interposed at a butting portion of the U-shaped ferrite cores 2, and a clamp 5 for fixing them. It is configured.

The winding section 3 is composed of a primary coil, a high-voltage secondary coil and a low-voltage tertiary coil. The high-voltage secondary coil is for supplying the cathode voltage and the focus voltage of the cathode ray tube and has a winding of several thousand turns. Have. The low-voltage tertiary coil is for supplying the heater power of the cathode ray tube, and the DC voltage to the image circuit and the integrated circuit.

The U-shaped ferrite core 2 is a U-shaped core half body made of a ferrite core, and has a rectangular rod-shaped base 2a.
A round rod-shaped leg portion 2b extends in parallel from both ends of the. The U-shaped ferrite core 2 is inserted into the previously wound winding portion 3 with the leg portions 2b butted together.
Form an annular magnetic path. A gap spacer 4 is inserted on the abutting surface of the U-shaped ferrite core 2 in order to prevent magnetic saturation of the ferrite. The assembled flyback transformer 1 is fixed by a metal clamp 5 having U-shaped elasticity so as to press the two U-shaped ferrite cores 2 from both sides, and the flyback transformer 1 is formed.

Such a flyback transformer 1 is designed so as to obtain a high output of several tens to several hundreds of watts depending on the deflection angle of the television receiver, the screen size, the voltage, and the like. Since this flyback transformer 1 handles a large amount of electric power, the inside of the ferrite core 1 is 2000-
A magnetic flux of 2500 gauss is passing through. Therefore, the heat generated by the iron loss raises the temperature of the flyback transformer, which causes deterioration of the resin used and the like, and is accompanied by the risk of ignition.

Since heat generated from copper loss is added in addition to ferrite, measures against heat generation are extremely important problems. Normally, to avoid such a danger, U-shaped ferrite core 2
The magnetic flux passing through the inside is reduced and the temperature rise is reduced to U
The letter-shaped ferrite core 2 is designed. For this reason, the U-shaped ferrite core 2 becomes large, and it is difficult to reduce the size and weight. In the current ferrite core design method, the shape, volume, etc. of the U-shaped ferrite core 2 are determined on the assumption that the magnetic flux uniformly passes through the inside of the U-shaped ferrite core 2.

Therefore, U of the flyback transformer 1 described above.
The magnetic flux distribution inside the V-shaped ferrite core 2 was obtained by magnetic field analysis. The U-shaped ferrite core used for analysis is the base 2
The length of a is 44.15 mm, the width is 15.15 mm, the height is 11.95 mm, the height of the legs 2b is 27.6 mm, and the diameter is 15.15 mm. FIG. 6 is a magnetic flux density distribution diagram showing relative values of magnetic flux inside the U-shaped ferrite core 2. From this analysis, the magnetic flux is U-shaped ferrite core 2
It was found that the magnetic flux did not uniformly pass through the inside of the inner peripheral side, and the density was high on the inner peripheral side and low on the outer peripheral side. It was found that it did not contribute as a magnetic material. Figure 7
[Fig. 4] is an iron loss distribution chart showing the relative value of the iron loss of the U-shaped ferrite core 2. It has been clarified that the iron loss distribution also shows the same tendency as the magnetic flux density.

[0008]

Since the conventional flyback transformer is constructed as described above, a large magnetic flux passes through the ferrite core during actual operation, and the magnetic flux density is concentrated in the inner peripheral corner portion in terms of shape. However, iron loss also increases. For this reason, heat generation is increased locally, accelerating the temperature rise of the entire flyback transformer, and significantly reducing the reliability of the flyback transformer. In the worst case, the danger of ignition is built in, and as a countermeasure, there is a problem that the shape of the ferrite core must be made large and the magnetic flux density must be designed to be small on average.

The present invention has been made in order to solve the above-mentioned problems, and provides a U-shaped ferrite core which can reduce the concentration of magnetic flux density to improve reliability and reduce the size and weight of a flyback transformer. The purpose is to

[0010]

The present invention is the following U-shaped ferrite core. (1) A U-shaped ferrite core in which legs extend from both ends of the base, and a projecting portion of 1 mmR or more or 1 mmC or more is formed in an inner peripheral corner portion formed by the base and the legs. (2) The U-shaped ferrite core according to (1) above, wherein a cutout portion is formed in a portion having an average leg magnetic flux density of 30% or less in an outer peripheral corner portion constituted by a base portion and a leg portion.

[0011]

In the U-shaped ferrite core according to claim 1 of the present invention, since the overhanging portion exists in the inner peripheral corner portion, the magnetic flux concentrated in the inner peripheral corner portion in the related art is dispersed, which causes iron loss and heat generation. To achieve high performance and high reliability of the flyback transformer. In the U-shaped ferrite core according to claim 2 of the present invention, since the cutout portion is formed in the portion of the outer peripheral corner portion where the magnetic flux density is low, it is possible to reduce the size and weight of the core without affecting the magnetic circuit. it can.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a front view showing a butted state of a U-shaped ferrite core of an embodiment, (b) is a BB sectional view thereof, and (c) is a front view of one U-shaped ferrite core. 4 to 7 indicate the same or corresponding parts.

The U-shaped ferrite core 2 has a structure in which the leg portions 2b in the shape of a round rod extend in parallel from both ends of the base portion 2a in the shape of a square rod, similarly to the conventional one. 1m in the inner corner 2c
An overhanging portion 11 having an inner peripheral surface formed by a C tangent of mC or more is formed. Further, in the outer peripheral corner portion 2d formed by the base portion 2a and the leg portion 2b, a portion having an average magnetic flux density of 30% or less of the leg portion 2b is deleted by a C tangent line to form a cutout portion 12.

In the U-shaped ferrite core 2 described above, the leg portions 2b of the two U-shaped ferrite cores 2 are inserted from both sides into the winding portion 3 which is wound in advance, as in the conventional one, and a gap spacer is formed. Butt with 4 in between to form a flightback transformer.

Since the U-shaped ferrite core 2 has the projecting portion 11 in the inner peripheral corner portion 2c, the magnetic flux concentrated in the conventional inner peripheral corner portion 2e is dispersed, thereby reducing iron loss and heat generation. And the high performance of the flightback transformer,
High reliability is realized. Further, the cutout portion 1 is provided in the outer peripheral corner portion 2d.
Since 2 is formed, it does not affect the magnetic circuit,
The U-shaped ferrite core 2 can be reduced in size and weight.

FIG. 2 is a magnetic flux density distribution diagram showing the relative values of the magnetic flux inside the U-shaped ferrite core 2. The inner peripheral corner portion 2c of the U-shaped ferrite core 2 used in the analysis of FIGS. 6 and 7 is 2 mmC. C tangent line (inner peripheral corner portion 2c of FIG. 6)
To the base portion 2a side and the leg portion 2b side to form an overhanging portion 11 having an inner peripheral surface formed by a C tangent line connecting 2 mm points, and a 6 mm C tangent line (see FIG. 6) on the outer peripheral corner portion 2d. The cutout portion 1 having an outer peripheral surface formed by a C tangent line of 6 mm from the outer peripheral corner portion 2d to the base portion 2a side and 6 mm to the leg portion 2b side.
Analysis was performed on the U-shaped ferrite core 2 in which 2 was formed. In FIG. 2, it can be seen that the concentration of the magnetic flux in the inner peripheral corner portion 2c is lessened than in the case of FIG. Further, FIG. 3 is an iron loss distribution diagram showing the relative value of the iron loss of the U-shaped ferrite core 2 as compared with the case of FIG.
It can be seen that the iron loss in c is reduced. In any case, it can be seen that the formation of the cutout portion 12 in the outer peripheral corner portion 2d has no influence on the magnetic circuit.

As described above, the unnecessary portion of the outer peripheral corner portion 2d of the U-shaped ferrite core 2 is deleted, and the overhanging portion 11 is formed on the inner peripheral corner portion 2c where the magnetic flux and the iron loss are concentrated. The U-shaped ferrite core for the back transformer can be optimized from the viewpoint of the magnetic circuit, and the overall weight and size can be reduced compared to the conventional shape. Since the local concentration of magnetic flux and iron loss is relaxed, a large average magnetic flux can be taken in the magnetic circuit design.

In the above embodiment, the inner peripheral portions of the overhanging portion 11 and the cutout portion 12 are formed in a C tangential line of 1 mmC or more, but these may be R-shaped of 1 mmR or more. Needless to say. U-shaped ferrite core 2
Although the leg portion 2b has a round shape, the same effect can be obtained even if the leg portion 2b has an angular shape, an elliptical shape, or the like. Furthermore U
The application of the U-shaped ferrite core 2 is not limited to the flyback transformer of the TV receiver, but can be applied to a flyback transformer of a display monitor, a high-voltage generation transformer using a U-shaped ferrite core, and the same effect as the above embodiment. Play.

[0019]

According to the U-shaped ferrite core of claim 1 of the present invention, since the overhanging portion of 1 mmR or more or 1 mmC or more is formed in the inner peripheral corner portion, the concentration of the magnetic flux in the inner peripheral corner portion can be relaxed. As a result, iron loss and heat generation can be reduced, a large average magnetic flux can be obtained, and high performance and high reliability of the device can be achieved.

In the U-shaped ferrite core according to claim 2 of the present invention, since the cutout portion is formed in a portion of the outer peripheral corner portion where the average magnetic flux density of the leg portion is 30% or less, waste as a magnetic circuit is eliminated and the apparatus is made compact. Can be converted.

[Brief description of drawings]

FIG. 1A is a front view showing a butted state of a U-shaped ferrite core of an embodiment, FIG.
(C) is a front view of one U-shaped ferrite core.

FIG. 2 is a magnetic flux density distribution diagram of the U-shaped ferrite core of the example.

FIG. 3 is an iron loss distribution diagram of the U-shaped ferrite core of the example.

FIG. 4 is a front view in which a part of a flyback transformer is cut.

FIG. 5 is a front view showing a butt state of a conventional U-shaped ferrite core, (b) is a sectional view taken along line AA, and (c) is a plan view of one U-shaped ferrite core.

FIG. 6 is a magnetic flux density distribution diagram of a conventional U-shaped ferrite core.

FIG. 7 is an iron loss distribution diagram of a conventional U-shaped ferrite core.

[Explanation of symbols]

 1 Flyback Transformer 2 U-shaped Ferrite Core 2a Base 2b Leg 2c Inner Corner 2d Outer Corner 3 Winding 4 Gap Spacer 5 Clamp 11 Overhang 12 Notch

Claims (2)

[Claims] 1. A U-shaped ferrite core having legs extending from both ends of a base, wherein an overhang of 1 mmR or more or 1 mmC or more is formed in an inner peripheral corner portion formed by the base and the legs. U-shaped ferrite core. 2. The U-shaped ferrite core according to claim 1, wherein a cutout portion is formed in a portion having a leg average magnetic flux density of 30% or less in an outer peripheral corner portion constituted by a base portion and a leg portion.