JP2012129378A - Impedance element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an impedance element having a high inductance and excellent DC superposition characteristics, as a filter for audio signal, without increasing the footprint.SOLUTION: The impedance element 1 consists of two metal conductors 5, an upper ferrite element 2 and a lower ferrite element 3. Either the upper ferrite element 2 and/or the lower ferrite element 3 is provided with grooves 4 of substantially same shape as that of the metal conductors 5 so that the metal conductors 5 can be sandwiched from above and below by two ferrite elements and buried therein. Furthermore, the metal conductors 5 are made to meander in a portion buried in the ferrite elements, and the linear line length thereof is increased in the range of 1.1-2.0 times.

Description

The present invention relates to a noise filter used in an amplifier circuit for digital audio.

The audio digital amplifier uses a PWM system that carries a sound signal by changing the width of a rectangular wave pulse. In a digital amplifier with an output of 10 watts or more, such as an audio circuit of a television receiver, a rectangular wave ripple is generated by combining two winding inductors and a capacitor for the purpose of preventing heat generation of the speaker coil by rectangular wave pulses and noise radiation from the speaker cable. Filtering.

In the case where such a large current flows, a magnetic element having a good DC superposition characteristic in which the effective inductance does not decrease when a large current is passed is required. For example, there is one disclosed in Patent Document 1. The magnetic element disclosed in Patent Document 1 has a structure in which a U-shaped metal conductor is sandwiched between two elements.

Japanese Patent No. 2951324

However, the problem when using the prior art is that the noise removal effect may be insufficient due to low impedance depending on the equipment used. This problem becomes conspicuous because the inductance becomes smaller as the element is made smaller.

There is a method of making the internal electrode into a spiral structure as a means to increase the impedance, but this method deteriorates the DC superposition characteristic, and the effective impedance characteristic affects the audio signal range, causing the signal to be distorted and the sound to be deteriorated. . Therefore, when the circuit current of the audio circuit is high, there is a problem that there are few choices of elements that can be used.

In order to solve the above-described problems, the present invention provides a sound signal filter that has a high inductance without increasing the mounting area, has a good DC superposition characteristic, and can be used even when the circuit current is high. It is to provide.

The impedance element according to the present invention includes two metal conductors and two ferrite elements sandwiching the metal conductor from above and below, that is, an upper ferrite element and a lower ferrite element.

By using two metal conductors as metal conductors, two circuits are formed in one element. For this reason, two winding inductors used for each of plus and minus are conventionally mounted. However, since the same effect can be obtained with one element, the mounting cost and the mounting area can be reduced.

At least one of the upper ferrite element and the lower ferrite element is provided with a groove having substantially the same shape as the metal conductor, and the two ferrite elements can be embedded so as to sandwich the metal conductor from above and below. It has become. The groove may be the same depth as the metal conductor, and both ferrite elements may have grooves or only one of them. For example, when the upper ferrite element is provided with a groove having the same depth as the metal conductor, the lower ferrite element may not be provided with a groove.

The two metal conductors can improve the inductance by meandering the portion embedded in the ferrite element and increasing the line length. The reason why the DC superposition characteristics deteriorate when using the conventional multilayer ferrite chip beads is that the internal electrodes have a spiral structure. It becomes possible to avoid degradation of the.

The longer the line length of the part where the metal conductor is embedded, the greater the inductance. However, if the length is too long, the current direction of the adjacent meandering pattern will counteract and the magnetic flux will cancel out, so the part where the metal conductor is embedded The line length is preferably set to be 1.1 to 2.0 times, more preferably 1.3 to 1.7 times that of the straight line.

According to the present invention, it is easy to increase the current and the distortion of the audio signal can be reduced. Further, since the structure is simple, the manufacturing process is simplified, and provision at a low cost is possible.

Assembly exploded perspective view of impedance element according to the present invention Perspective view with metal conductor embedded in upper and lower ferrite elements The perspective view of the impedance element by this invention Graph showing the relationship between increase in metal conductor length and impedance value

Next, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is an exploded perspective view of an impedance element 1 according to the present invention, which includes two metal conductors 5, an upper ferrite element 2, and a lower ferrite element 3.

As shown in FIG. 1, the portion of the metal conductor 5 embedded in the ferrite element has a long line length compared to when it is made linear by meandering.

The distance ratio when meandering relative to the length when the portion in which the metal conductor is embedded is made linear, and the impedance value ratio when making the meander when the metal conductor is made linear (Z value ratio) 4 is the relationship shown in FIG. 4. When the distance ratio is between 1.1 times and 2.0 times, the Z value ratio becomes 1.3 times or more. More preferably, if the distance ratio is in the range of 1.3 times to 1.7 times, the Z value ratio is 1.8 times or more, which is further desirable. Thus, when the line length is increased within the above range, the impedance value of the element increases, that is, the inductance can be increased.

Further, as shown in FIG. 1, the upper ferrite element 2 and the lower ferrite element 3 are provided with grooves 4 having substantially the same shape as that of the metal conductor 5, and the depth of each of them is one half of the thickness of the metal conductor. When the metal conductor 5 is sandwiched between the upper ferrite element 2 and the lower ferrite element 3, the gap is not formed. It should be noted that the groove depth of the upper ferrite element and the groove depth of the lower ferrite element only have to be the same as the thickness of the metal conductor 5, for example, the same as the thickness of the metal conductor 5 in one ferrite element. A depth groove may be provided, and the other ferrite element may not have a groove.

As shown in FIG. 2, a metal conductor 5 is sandwiched between the upper ferrite element 2 and the lower ferrite element 3, and the upper ferrite element 2 and the lower ferrite element 3 are bonded and fixed with an adhesive such as an epoxy.

As shown in FIG. 3, the start and end portions of the metal conductor 5 exposed to the outside of the bonded ferrite element can be mounted on a printed circuit board by being bent toward the upper ferrite element side or the lower ferrite element side.

By causing the two metal terminals to meander in the ferrite element, a high inductance can be obtained without increasing the mounting area. In addition, since the impedance element according to the present invention has a simple structure, the manufacturing process is simplified and the impedance element can be provided at low cost.

1 Impedance element 2 Upper ferrite element 3 Lower ferrite element 4 Groove 5 Metal conductor

Claims (3)

In an impedance element in which two non-contact metal conductors are sandwiched between an upper ferrite element and a lower ferrite element, at least one of the ferrite elements has a groove, and the metal conductor is inserted into the groove. And the two ferrite conductors are meandered so that the line length of the portion embedded in the ferrite element is a straight line. An impedance element characterized by being lengthened in a range of 1 to 2.0 times. The impedance element according to claim 1, wherein a start end portion and a termination end portion of the two metal conductors exposed to the outside of the ferrite element are bent toward the upper ferrite element side or the lower ferrite element side. The impedance element according to claim 1 or 2, wherein a material of the ferrite element is made of a Ni-Zn system.

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