JPH0451448Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a flyback transformer for supplying high voltage to cathode ray tube anodes of television receivers, display devices, etc.

<Prior art> In general, in a flyback transformer, a driving DC current flows through a coil wound around the core, but in order to prevent DC magnetization saturation caused by this, conventionally, as shown in Fig. 7, a pair of U-shaped core 3
A bobbin 3 with a coil 32 wound around 1a and 31b
3, and core gaps 34a and 34b were inserted evenly between the joints of the cores 31a and 31b, that is, on both the winding side and the non-winding side of the coil 32.

On the other hand, in a flyback transformer, the magnetic resistance of the core on the non-winding side of the coil increases by the gap, and some of the magnetic flux generated in the coil leaks out into space. Magnetic interference may occur due to magnetic flux,
Conventionally, as a method to reduce this leakage magnetic flux, (1)
(2) A method of magnetic shielding in which the entire flyback transformer is covered with a shielding case.(2) A method of magnetic shielding in which the entire flyback transformer is covered with a shielding case. It was hot.

<Problems to be solved by the invention> However, among these conventional methods for reducing leakage magnetic flux, the above-mentioned method (1) requires a complicated structure for providing the shot ring.
Method (2) had a problem in that the entire structure was covered with a shield case, making the structure larger.

<Means for solving the problems> In order to solve the above problems, the flyback transformer of the present invention has a main coil and, if necessary, a sub coil wound around the core. An air-core cancel coil is connected in series to the sub coil, and the cancel coil is arranged coaxially with the main coil via a magnetic piece, and the external leakage magnetic flux generated by the main coil is A reverse magnetic flux is generated by a combination of a cancel coil and a magnetic piece.

<Function> An air-core cancel coil is placed coaxially with the main coil wound around the core via a magnetic piece, and the external leakage magnetic flux generated by the main coil is canceled by the cancel coil. The magnetic flux is reliably reduced by the magnetic flux opposite to the external leakage magnetic flux generated by the combination of the coil and the magnetic piece.

<Example> Hereinafter, an example of the flyback transformer of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a partially cutaway cross-sectional side view of the flyback transformer of the present invention. In the figure, 1 is a low-voltage bobbin made of synthetic resin, and the low-voltage bobbin 1 is a cylindrical body around which a low-voltage coil 2 is wound. A core guide frame 4 is formed at one end of the coil 3, and a terminal attachment part 6 is formed in which a plurality of pin terminals 5 for connecting the coil terminal parts are implanted. Reference numeral 7 denotes a high-pressure bobbin made of synthetic resin, and is installed on the outside of the main body 3 of the low-pressure bobbin 1 with a high-voltage coil 8 wound thereon. A core 9 is constructed by joining a pair of U-shaped cores 9a and 9b, and is disposed on the inner surface of the main body 3 of the low-pressure bobbin 1 and on the core guide frame 4, and is secured by fixing means such as screws and nuts (Fig. (not shown) to the low-pressure bobbin 1. 10 is an air-core cancel coil, and as shown in Fig. 2, it is connected horizontally to the B power supply in order to reduce the external leakage magnetic flux generated from the B power supply of the flyback transformer to the collector winding of the horizontal output transistor Tr. It is electrically connected in series with the low voltage coil 2 between the output transistor Tr,
The low-voltage coil 2, which forms the main coil of the flyback transformer, and the low-voltage coil 2 are connected via a disc-shaped magnetic piece 11 made of ferrite, silicon steel plate, etc. (with the magnetic piece 11 inserted into the air core of the cancel coil 10). Coaxially and above the high voltage coil 8 wound on the outside of the
(on the opposite side). Here, the low voltage coil 2 and the cancel coil 10 of the flyback transformer are set in a winding direction and a current direction such that the direction of the magnetic flux generated by each is always opposite. FIG. 3 shows a cancel bobbin for arranging a cancel coil and a magnetic piece. In the figure, the cancel bobbin 12 is composed of a flat main part 13 and three leg parts 14. A groove 13a is formed on the inner periphery of the magnetic piece 13 to accommodate the cancel coil 10 and the magnetic piece 11.
The entire cancel bobbin 12 is divided into two parts to facilitate storage in the groove 13a. In FIG. 1, numeral 15 indicates a printed circuit board on which a flyback transformer is mounted.

In a flyback transformer with such a configuration,
The low voltage coil 2 is wound around the outer periphery of the main body 3 of the low voltage bobbin 1, and the high voltage coil 8 is wound around the outside of the low voltage coil 2 via the high voltage bobbin 7.
The U-shaped cores 9a and 9b are fitted into the inner periphery of the main body 3 and the core guide frame 4 portion, and are attached and fixed to the printed circuit board 15 via pin terminals 5 and the like. On the other hand, the cancel coil 10 and the cancel bobbin 12 equipped with the magnetic piece 11 are connected to the cancel coil 10.
The magnetic piece 11 is mounted and fixed on a printed circuit board 15 via the legs 14 so that it is coaxial with the main coil (low-voltage coil 2) of the flyback transformer. After that, current is applied in a predetermined direction to the low voltage coil 2, high voltage coil 8, and cancel coil 10, respectively. As shown in Fig. 4, when the current is applied, the cancel _coil 1
The cancel magnetic flux Hc generated by the combination of 0 and the magnetic piece 11 becomes a magnetic flux in the opposite direction, and as a result,
The external leakage magnetic flux H _R generated by the main coil is canceled out by the cancel magnetic flux Hc and is surely reduced. Here, when the magnetic piece 11 is used, the rate of reduction in external leakage magnetic flux H _R increases by about 60% compared to the case where the magnetic piece 11 is not used. And in Figure 4,...

Claims (1)

[Scope of utility model registration request] In a flyback transformer in which a main coil and, if necessary, a sub-coil are wound around a core, an air-core cancel coil is connected in series to the main coil or the sub-coil, and the cancel coil is connected through a magnetic piece. and is arranged coaxially with respect to the main coil, and a magnetic flux opposite to the external leakage magnetic flux generated by the main coil is generated by a combination of the cancel coil and the magnetic piece. Flyback transformer.