GB2250139A - Flyback transformer - Google Patents

Abstract

A flyback transformer has butting core pieces 2a, 2b of magnetic material. A gap spacer 6 also of magnetic material has a hole 8 which is not open to the outside, and is interposed at at least one of the butting portions 4 of the core pieces. Alternatively a hole 8 which is not open to the outside is formed in at least one of the butting portions 4 of the core pieces (Fig.4). <IMAGE>

Description

FLYBACK TRANSFORMER The present invention relates to a flyback transformer used for a TV receiver wherein a core is formed by butting U-shaped core pieces of a material such as ferrite with each other and windings are formed on the core.

Figure 5 is a front view partly broken of a conventional flyback transformer. In Figure 5, a flyback transformer 1 comprises a core formed by butting a pair of U-shaped core pieces 2a, 2b with each other, a winding part 3 applied to the core 2, a gap spacer inserted in gaps 5 at the butting portions 4 and a C-shaped clamp 7 for fixing the pair of U-shaped cpre pieces 2a, 2b.

The winding part 2 is constituted by a primary coil, a secondary coil for high voltage and a third coil for low voltage. The secondary coil for high voltage is to apply an anode voltage and a focus voltage to a TV tube and has a winding of several thousand turns. The third coil for low voltage is to apply a d.c. voltage to a picture signal circuit, an I.C. circuit for the TV tube and to supply power to the heater for the TV tube.

In the conventional flyback transformer 1, the winding part 3 is previously formed, and the U-shaped core pieces 2a, 2b of ferrite are inserted in the winding part 3, and gap spacers 6 are interposed at the gaps 5 at the butting portions 4 of the core pieces 2a, 2b. Thus assembled core pieces 2a, 2b are fixed by means of a metallic clamp 7 of a C-shaped elastic material to thereby form the flyback transformer 1.

Such flyback transformer 1 is so designed as to obtain a high output such as of from several ten Ws to one hundred and several ten Ws depending on the angle of polarization, the screen size and required voltage for the TV receiver. Since the flyback transformer 1 generates a large electric power, a magnetic flux of 2,000-2,500 Gauss is formed in the core 2. Therefore the gap spacers 6 made of a material such as a plastic plate are used to prevent magnetic saturation in the core 2.

In the conventional flyback transformer having the above-mentioned construction, a large amount of leakage flux leaked from the gaps spacers 6 to the outside, which adversely effected to the characteristics of electronic components such as a deflection yoke and so on. Further, the leakage flux interfered with the coils of the winding part 3 to cause increase in a copper loss.

It is an object of the present invention to eliminate the above-mentioned problem and to provide a flyback transformer which reduces a leakage flux leaked from the flyback transformer to the outside, and reduces a copper loss caused by interference with the coil portions of the winding part.

In an aspect of the present invention, there is provided a flyback transformer comprising a core formed by butting core pieces made of a magnetic material with each other and a winding part, characterized in that a gap spacer made of a magnetic material having a hole which does not open to the outside is interposed at at least one of the butting portions of the core pieces.

In another aspect of the present invention, there is provided a flyback transformer comprising a core formed by butting core pieces made of a magnetic material with each other and a winding part, characterized in that a hole which does not open to the outside is formed at at least one of the butting portions of the core pieces.

In drawings: Figure 1 is a front view partly cross-sectioned and broken of an embodiment of the flyback transformer according to the present invention; Figure 2 is a perspective view of an embodiment of a gap spacer used for the flyback transformer of the present invention; Figure 3 is a front view partly cross-sectioned and broken of another embodiment of the flyback transformer according to the present invention; Figure 4 is a perspective view of an embodiment of a core piece used for the flyback transformer of the present invention; Figure 5 is a front view partly cross-sectioned and broken of a conventional flyback transformer; Figure 6 is a front view partly cross-sectioned and broken of another embodiment of the flyback transformer of the present invention;; Figure 7 is a perspective view of another embodiment of a gap spacer used for the flyback transformer as shown in Figure 6; Figure 8 is a front view partly cross-sectioned and broken of another embodiment of the flyback transformer of the present invention; and Figure 9 is a perspective view of another embodiment of a core piece for the flyback transformer as shown in Figure 8.

Preferred embodiments of the flyback transformer of the present invention will be described in detail with reference to the drawings.

Figure 1 is a front view partly cross-sectioned and broken of an embodiment of the flyback transformer of the present invention, and Figure 2 is a perspective view showing a gap spacer used for the flyback transformer of the present invention. In Figures 1 and 2, the same reference numerals designate the same or corresponding parts.

A flyback transformer 1 in this embodiment as in Figure 1 has the substantially same construction as in Figure 5. However, eadh gap spacer 6 is made of a ferrite plate having a hole at the central portion which does not open to the outside at its outer peripheral portion as shown in Figure 2. The gap spacer 6 is interposed in a gap 5 at each of the butting portions 4 of the core pieces 2a, 2b which are also made of ferrite.

Preferably, the gap spacer has a ring body which has the same outer configuration as the shape of the outer configuration of the butting portions of each of the core pieces 2a, 2b, and the hole is a through hole having the same center as that of the ring body. In Figure 1, numeral 9 designates a line of magnetic flux which is produced in the core when a current is supplied to the primary coil of the winding part 3.

The operation of the flyback transformer of the present invention will be described. When an a.c.

current is supplied to the primary coil of the winding part 3, the line of magnetic flux 9 in a closed curve is produced in a magnetic circuit which is constituted by the U-shaped core pieces 2a, 2b and the gap spacers 6.

The line of magnetic flux 9 changes at the same frequency as the current flowing in the primary coil. If no gap spacers 6 are interposed between the core pieces 2a, 2b, the magnetic resistance of the line of magnetic flux 9 is determined by the magnitude of the gaps 5.

On the other hand, when the gap spacers 6 are used, the magnetic resistance R of the magnetic circuit can be expressed as follows: D + y2S2 r1S where S represents the surface area of a plane cut perpendicular to the magnetic path in the U-shaped core pieces 2a, 2b in an assembled state, e represents the average length of magnetic path, d represents the distance of the gap 5, y1 is the magnetic permeability of the U-shaped core pieces, 2 is the magnetic permeability of the gap spacer and S2 is a cross-sectional surface area of the gap spacer cut perpendicular to the magnetic path.

Generally, when the magnetic permeability of the Ushaped core pieces is greater than the magnetic permeability of the gap spacer, the following equation is established: d 2S Accordingly, a magnetic flux zit produced when an a.c.

current I is supplied to the primary coil which has the number of turns N1 is expressed as follows:

which is introduced from the equation of relationship as follows:

Accordingly, an average magnetic density B in the core is expressed as follows:

Accordingly, by providing the hole 8 in the gap spacer 6 and by changing the cross-sectional area S2, the magnetic saturation of the flyback transformer 1 comprising the U-shaped core pieces 2a, 2b can be prevented.

Further, if the gap spacer 6 is formed by using a material different from that of the core pieces 2a, 2b to thereby change the magnetic permeability, the magnetic saturation can be further easily controlled.

Figure 3 is a front view partly cross-sectioned and broken of another embodiment of the flyback transformer of the present invention, and Figure 4 is a perspective view showing one of the core pieces used for the flyback transformer of the present invention.

In the second embodiment, each of the core pieces 2a, 2b is formed into a U-shape using ferrite, and each of the butting portions 4 of each of the core pieces 2a, 2b is circular and a hole 8 is formed in the center of each of the butting portions 4. The core 2 is formed by butting the core pieces 2a, 2b with each other without forming a gap. In this case, an enclosed cylindrical bore is formed at the central portion of the butting portion by butting the core pieces 2a, 2b with each other. The embodiment as shown in Figure 3 performs the same effect as that shown in Figure 1. In the abovementioned embodiments, the case that the gap spacer 6 or the hole 8 is formed at each of the butting portions 4 which are formed by butting the U-shaped core pieces 2a, 2b with each other, has been discussed.However, the same effect can be obtained even in the case that the gap spacer 6 or the hole 8 is provided one of the butting portions 4.

Figure 6 and 7 show another embodiment of the flyback transformer of the present invention is which the same reference numerals designate the same or corresponding parts as in Figures 1 and 2. In this embodiment, a single gap spacer 6 made of a ferrite plate having a ring body in which a through hole 8 is formed at the central portion is interposed at one of the butting portions of the core pieces 2a, 2b. In this case, the length of the gap portion and the height of the gap spacer are respectively about twice as those shown in the Figure 1 embodiment.

Figures 8 and 9 show another embodiment of the flyback transformer of the present invention in which the same reference numerals designate the same or corresponding parts as in Figures 3 and 4. In this embodiment, a hole 8 is formed in one of the butting portions 4 in the same manner as shown in Figures 3 and 4. In this case, the depth of the hole 8 is about twice as that shown in the Figure 3 embodiment.

Further, in the above-mentioned embodiments, the flyback transformer comprising a pair of the U-shaped core pieces 2a, 2b of ferrite has been explained.

However, a combination of a U-shaped core piece and another core piece of a magnetic material having a different shape, e.g. an I-shaped core piece may be applicable in the present invention.

Thus, in the present invention, since the flyback transformer is provided with a gap spacer of a magnetic material or a hole which is not opened to the outside, at the butting portion of the core pieces, a leakage flux leaked outside can be reduced to thereby provide the flyback transformer of a high quality.

Claims (5)

CLAIMS:

1. A flyback transformer comprising a core formed by butting core pieces made of a magnetic material with each other and a winding part, characterized in that a gap spacer made of a magnetic material having a hole which is not open to the outside is interposed at at least one of the butting portions of said core pieces.

2. The flyback transformer according to Claim 1, wherein said gap spacer has a ring body which has the same shape of outer configuration as the shape of the outer configuration of the butting portion, and said hole is a through hole having the same center as that of the ring body.

3. A flyback transformer comprising a core formed by butting core pieces made of a magnetic material with each other and a winding part, characterized in that a hole which does not open to the outside is formed in at least one of the butting portions of said core pieces.

4. The flyback transformer according to Claim 3, wherein said hole is formed in - both core pieces, and the shape of the holes is circular so as to form enclosed cylindrical bore when the core pieces are abutted each other.

5. A flyback transformer substantially as herein described with reference to any of Figures 1 to 4, or 6 to 9 of the accompanying drawings.