JPH0129856Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a leakage magnetic flux canceling device that reduces noise caused by leakage magnetic flux in a low frequency amplifier circuit or the like.

2. Description of the Related Art Amplifying circuits for minute signals such as phono inputs of audio equipment have a problem in that noise is generated by leakage magnetic flux from a transformer that constitutes the power supply.

FIG. 1 shows a conventional leakage magnetic flux canceling device that solves this problem. In Figure 1, 1 is the rear chassis of the device, 2 is a printed circuit board placed inside the chassis, and 3 and 4 are signal side and ground side input terminals attached to the rear chassis 1 and soldered to the printed circuit board 2. , 5 is an amplifier circuit, 6 and 7 are input terminals on the signal side and ground side,
Reference numerals 8 and 9 are conductive wires connecting the input terminals 3 and 4 on the chassis 1 side and the input terminals 6 and 7 on the amplifier circuit 5 side. The conductive wires 8 and 9 are made of copper foil printed on the printed circuit board 2, and are wired to form two loops.

If this is done, electromotive forces A and B will be generated in each loop due to the leakage magnetic flux F, but since these loops intersect, the input terminals 6 and 7 of the amplifier circuit 5 will have electromotive forces A and B. The difference between the electromotive forces is input, and the amplifier circuit 5 generates noise corresponding to this difference between the electromotive forces. Therefore, if the electromotive forces A and B are made equal by, for example, setting the sizes of the two loops to be equal, these cancel each other out and noise can be reduced.

However, this method is often not possible due to implementation reasons. That is, since a large number of electrical components are usually attached to the upper surface of the printed circuit board 2, considerable restrictions are placed on the wiring of the conductive wires 8 and 9. Therefore, it is actually extremely difficult to set the two loops to the same size. Furthermore, even if loops of the same size are formed, it is rare that the leakage magnetic flux received by each loop will be equal, and in this case also a difference will occur in the electromotive forces A and B, and noise will be generated accordingly. become.

The present invention solves this problem by absorbing the difference between the electromotive forces of the two loops by the electromotive force of a separately provided coil, thereby reducing the leakage magnetic flux. The purpose of this invention is to provide a canceling device.

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3.

In FIGS. 2 and 3, parts having the same functions as those in FIG. 1 are denoted by the same reference numerals, and explanations thereof will be omitted. 10 is a coil connected in series to one loop (more specifically, to the conductor 8 on the signal side);
Reference numerals 1 and 12 are output terminals of the amplifier circuit 5, and 13 is a signal source for a preceding stage amplifier, cartridge, oscillator, etc.

In the above configuration, for the reasons mentioned above, 2
A difference occurs between the electromotive forces A′ and B′ of the two loops. However, in this embodiment, an electromotive force is also generated in the coil 10 due to the leakage magnetic flux, and this is added to the electromotive force B' of one loop. Therefore, by adjusting the size and number of turns of the coil 10 so that the sum of the electromotive force of the coil 10 and the electromotive force B' of one loop becomes equal to the electromotive force A' of the other loop, the total electromotive force can be reduced. The powers cancel each other out, and as a result, no noise is input to the input terminals 6 and 7 of the amplifier circuit 5, and no noise is output to the output terminals 11 and 12 as well.

Note that if the electromotive force A' becomes smaller than the electromotive force B', the coil 10 may be connected to the loop on the side that generates the electromotive force A'.

In this way, when it is difficult to adjust the size of the conductor loop due to mounting reasons, the present invention connects a coil in series to the loop with the smaller electromotive force due to leakage magnetic flux, and adjusts the number of turns of the coil. Since the size is adjusted to completely cancel the electromotive force caused by the loop and the electromotive force caused by the coil, it is possible to reliably eliminate noise caused by leakage magnetic flux in a low frequency amplifier or the like.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a conventional leakage flux canceling device.
FIG. 2 is a perspective view of an embodiment of the present invention, and FIG. 3 is a circuit diagram thereof. 1...Rear chassis, 2...Printed circuit board,
3, 4...Input terminal, 5...Amplification circuit, 6,7...
...Input terminal of amplifier circuit, 8, 9... Conductor, 10...
... Coil, 11, 12 ... Output terminal of amplifier circuit,
13...Signal source.

Claims (1)

[Scope of utility model registration request] Wire the conductors drawn from the input terminals on the signal side and the ground side into two loops so that the electromotive force caused by the leakage magnetic flux is in opposite directions, and in series with one of the above loops, the electromotive force generated by the leakage magnetic flux is A device for canceling leakage magnetic flux, characterized in that a coil having a size and number of turns is connected such that the electromotive force is equal to the difference between the electromotive forces of the two loops.