JPH0429534Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a transformer leakage magnetic flux prevention structure that prevents induced hum caused by transformer leakage magnetic flux.

[Prior Art] Generally, leakage magnetic flux is generated from power transformers used in audio equipment such as amplifiers.
Particularly in high-sensitivity amplifiers that amplify minute signals, the presence of this leakage magnetic flux cannot be ignored, and problems such as deterioration of amplification characteristics occur due to the influence of induced hum generated by the leakage magnetic flux. Figure 3 shows the principle of generation of leakage magnetic flux.
Due to the AC power applied from the power transformer 2 placed above, at a certain moment, a leakage magnetic flux φ _A along the front surface of the chassis 1 and a leakage magnetic flux φ _A ′ along the back surface of the chassis 1 are generated as shown in the figure. Occur. For example, if a coil 3 or the like is placed on the path of these leakage magnetic fluxes φ _A and φ _A ', an electromotive force e is induced in the coil 3 by interlinking with these leakage magnetic fluxes. This causes induced hum.

In order to prevent this induced hum, conventionally, the power transformer and the affected parts have been shielded with a steel plate case.
Alternatively, magnetic shielding is performed using a steel plate shot ring or a humful belt.

[Problems to be solved by the invention] By the way, when shielding is performed using a steel plate case, not only does the cost increase, but the steel plate case has a negative effect on the signal current and causes distortion.
Another problem is that the height dimension becomes large. On the other hand, when using a shot ring or the like, there is a problem that sufficient effects cannot be obtained.

The present invention has been developed in response to the above-mentioned problems, and it is an object of the present invention to provide a transformer leakage magnetic flux prevention structure that can easily prevent induced hum.

[Means for Solving the Problems] In order to achieve the above object, the present invention has a transformer leakage magnetic flux prevention structure that prevents induced hum caused by leakage magnetic flux of the transformer, in which magnetic fluxes are generated in opposite directions. The present invention is characterized in that the first and second transformers are disposed close to each other to cancel leakage magnetic flux generated by the first and second transformers.

[Operation] Since the first and second transformers generate magnetic flux in mutually opposite directions, the leakage magnetic fluxes cancel each other out. Therefore, induced hum can be easily prevented without using any means such as shielding with a steel plate case.

[Embodiment of the invention] Fig. 1 is a schematic plan view showing a structure for preventing leakage magnetic flux of a transformer according to an embodiment of the invention, and Fig. 2 is a schematic diagram showing the principle of the invention. On the chassis 11 there is a
power transformer 12a and second power transformer 1
2b are arranged close to each other, and a high-sensitivity amplifier circuit 1 such as a phono amplifier is placed at a desired position on the chassis 11.
4 is placed. 15 indicates other circuits. First and second power transformers 12a, 1
2b are configured to generate magnetic flux in mutually opposite directions.

When AC power is applied to the first and second power transformers 12a and _12b , as shown in FIG. Leakage magnetic flux φ _A ′ is generated. At the same time, the second power transformer 1
2b generates a leakage magnetic flux φ _{B along the back surface of the chassis 1 and φ B ' along the front surface in the opposite direction to the above-mentioned φ A and φ A} '. Since these leakage magnetic fluxes φ _A and φ _B ′, φ _A ′ and φ _B are in opposite directions, they are canceled out, and as a result, they are placed on the path of φ _A , φ _A ′, and φ _B , φ _B ′. No electromotive force is induced in the coil 13.

Therefore, no electromotive force is generated in the amplifier circuit 14 disposed at a position corresponding to the coil 13 in FIG. 1, so that induced hum can be prevented.

According to the embodiment of the present invention, an increase in cost can be avoided because a steel plate case for shielding, a shot ring, etc. are not used as in the conventional case. Further, there will be no adverse effect on the signal current. Furthermore, since a case is not used, the height dimension can be reduced, so that it is possible to downsize the device.

[Effects of the invention] As described above, according to the invention, the transformer is divided into two parts to cancel the leakage magnetic flux, so that induced hum can be easily prevented without increasing costs.

[Brief explanation of the drawing]

Fig. 1 is a schematic plan view showing a transformer leakage magnetic flux prevention structure according to an embodiment of the present invention, Fig. 2 is a schematic diagram showing the principle of the present invention, and Fig. 3 is a schematic diagram showing the background of the present invention. 11 ... chassis, 12a, 12b ... power transformer, 14 ... amplifier circuit.

Claims (1)

[Scope of utility model registration request] In a transformer leakage magnetic flux prevention structure that prevents induced hum caused by leakage magnetic flux of a transformer, first and second transformers that generate magnetic flux in opposite directions are arranged close to each other, and the first and second
A transformer leakage magnetic flux prevention structure characterized in that the leakage magnetic flux generated by the transformer is canceled out.