JP2002344273A - Filter and filter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter for reducing the noise of output signal. SOLUTION: In the filter comprising a plurality of coils L4, L5, and L6 arranged in parallel, the coils L4, L5, and L6 are made up of no-edge coils having a ring-shaped core. The axial directions of the cores of adjoining coils L4 and L5 are made to cross each other, so that the flux leakage from the coil L4 is made difficult to be interlinked with the winding of the coil L5 and the electromotive force caused by the electromagnetic induction of the coil L5 is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a filter and a filter device for passing a signal of a predetermined frequency.
In particular, it relates to a filter and a filter device having a plurality of coils.

[0002]

2. Description of the Related Art A 1-bit signal obtained by performing Δ ア ナ ロ グ modulation processing on an analog audio signal has a very high sampling frequency and a short data length, and can be transmitted by appropriately setting coefficients of an integrator and an adder. The frequency band can be widened. In addition, a high dynamic range can be secured for an audio band that is low with respect to the sampling frequency. For this reason, a frequency corresponding to a sound source can be set, and is adopted for a new standard CD (compact disk), DVD (digital video disk) and the like.

When demodulating a signal extracted from a CD or DVD into an analog audio signal, a 1-bit signal converted by ΔΣ modulation is amplified, and then a low-pass filter (hereinafter, referred to as “LPF”) is used. Noise is cut off. For the LPF, a Butterworth-type filter of a fourth order or higher is generally used in order to steeply cut off a high frequency region other than the pass band of the audio signal. The Butterworth filter has a plurality of coils connected in series, a capacitor connected to the ground is branched from adjacent coils, and a high-frequency signal flows to the ground side to output a low-frequency signal. It has become so.

[0004]

However, according to the above-mentioned conventional filter, when a large current flows through the coil, the leakage magnetic flux from the coil increases. As a result, the leakage magnetic flux links to the adjacent coil, and an electromotive force is generated in the adjacent coil by electromagnetic induction. Therefore, there is a problem that the output signal fluctuates and noise is generated in the demodulated analog audio signal.

An object of the present invention is to provide a filter and a filter device capable of reducing noise of an output signal.

[0006]

In order to achieve the above object, a filter according to the present invention comprises first and second endless coils whose magnetic cores are adjacent to each other at right angles to each other. According to this configuration, the first and second endless coils whose axial directions of the ring-shaped magnetic core are orthogonal to each other are arranged in parallel.
The magnetic flux generated by the first endless coil passes through the magnetic core, and the leakage magnetic flux is generated substantially parallel to the magnetic path surface of the magnetic core and does not easily link with the second endless coil.

Further, the filter of the present invention is characterized in that it has first and second cylindrical coils whose axial directions are orthogonal to each other and adjacent to each other. According to this configuration, the first and second cylindrical coils having an air core or a columnar magnetic core are arranged side by side in the axial direction at right angles, and the magnetic flux generated by the first cylindrical coil is generated by the second cylindrical coil.
Does not easily link with the tubular coil.

Further, the filter of the present invention includes first and second endless coils adjacent to each other in the axial direction of the magnetic core, and the first endless coil and the second endless coil have a step in a direction perpendicular to the axial direction. Doing that.

The filter of the present invention includes first and second endless coils adjacent to each other in a direction perpendicular to the axial direction of the magnetic core, and the first endless coil and the second endless coil have a step in the axial direction. Doing that.

[0010] The filter of the present invention includes first and second cylindrical coils adjacent to each other in the axial direction. The first cylindrical coil and the second cylindrical coil have a step in a direction perpendicular to the axial direction. It is characterized by having.

The filter according to the present invention includes first and second cylindrical coils which are adjacent to each other in a direction perpendicular to the axial direction.
The cylindrical coil and the second cylindrical coil have a step in the axial direction.

The filter according to the present invention is characterized in that it has a plurality of coils connected in series and through which the same current flows.

Further, the filter device of the present invention is characterized in that it has a plurality of filters of any one of the above-mentioned configurations, and a shield plate is provided between each filter.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a 1-bit signal amplifying device. The 1-bit signal amplifying device 1 has an amplifying unit 3 composed of a semiconductor power amplifying element.
Is connected to a modulation unit 2 that performs ΔΣ modulation processing and an LPF 4 that blocks high-frequency noise. An audio signal source 5 composed of a CD device, a DVD device, or the like is connected to the input side of the modulation unit 2, and the output side of the LPF 4 is connected to a speaker 6 or the like.

An RF signal extracted by an optical pickup or the like provided in the audio signal source 5 is input to a 1-bit signal amplifying device 1 and subjected to ΔΣ modulation processing by a modulator 2. In the Δ 処理 modulation processing, for example, the frequency is 64 fs (fs =
44.1 kHz) and performs a process of converting it to a 1-bit signal.

Thereafter, the one-bit signal is amplified by the amplifier 3. The amplifying unit 3 has a noise shaping circuit, and generates noise of unnecessary high frequency components because the noise components are shifted to the high frequency side. Therefore, the LPF 4 blocks high-frequency noise and outputs a demodulated analog audio signal. Thereby, the sound is reproduced from the speaker 6. Since the amplifying unit 3 including the semiconductor power amplifying element is used not in the linear region but in the non-linear region,
Power amplification can be performed with extremely high efficiency.

FIG. 2 is a circuit diagram showing the configuration of the LPF 4. The LPF 4 is capable of inputting / outputting two channels on the L side and the R side, and signals input from the amplifier 3 to the input terminals Lin and Rin are output from the output terminals Lout and Rout, respectively.

The coils L11, L12, L13 are connected in series between the input terminal Lin and the output terminal Lout. A grounded capacitor C11 is connected between the coil L11 and the coil L12. Coil L1
A capacitor C12 connected to the ground is connected between the coil 2 and the coil L13. Coil L13 and output terminal Lou
Between t, the capacitor C13 connected to the ground is connected. This constitutes a sixth-order Butterworth filter.

Similarly, coils L14, L15, L16 are connected in series between the input terminal Rin and the output terminal Rout. A grounded capacitor C14 is connected between the coil L14 and the coil L15. A grounded capacitor C15 is connected between the coil L15 and the coil L16. A grounded capacitor C16 is connected between the coil L16 and the output terminal Rout.

As shown in FIG. 3A, the coils L11 to L16 are an air-core cylindrical coil composed of a winding 21 having no magnetic core, and are wound around a columnar magnetic core 11 as shown in FIG. 2
3 is formed by an endless coil in which a winding 21 is wound around a ring-shaped magnetic core 12 as shown in FIG.

FIG. 4 is a diagram showing an arrangement of coils of the LPF 4 according to the first embodiment. The coils L1, L2, and L3 are connected in series corresponding to the Lch coils L11, L12, and L13 in FIG. 2 described above, and are formed of cylindrical coils having a columnar magnetic core. Note that the Rch has the same configuration.
The axes c1 and c3 of the coil L1 (first cylindrical coil) and the coil L3 are arranged in parallel, and the coil L2
(The second cylindrical coil) is such that the direction of the axis c2 is the coil L1,
It is arranged orthogonal to the direction of the axes c1 and c3 of L3.

The magnetic flux generated by the coil L1 is
Since it passes perpendicular to the second axis c2, it is difficult to link with the winding (not shown) of the coil L2, and the generation of electromotive force due to electromagnetic induction is suppressed. Similarly, the magnetic flux generated by the coil L2 passes perpendicularly to the axes c1 and c3 of the coils L1 and L3, making it difficult to link with the winding 21 and suppressing the generation of electromotive force. Therefore, the output terminal Lou
Noise of the audio signal output from t and Rout can be reduced.

FIG. 5 is a diagram showing an arrangement of coils of the LPF 4 according to the second embodiment. The same parts as those in the first embodiment in FIG. 4 are denoted by the same reference numerals. Coil L1, L2, L3
Are the Lch coils L11, L12, L13 of the aforementioned Lch of FIG.
And a cylindrical coil having a columnar magnetic core. Note that the Rch has the same configuration. Coil L1 (first cylindrical coil) and coil L3 have their respective axes c1 and c3 arranged in parallel, and coil L2 (second cylindrical coil) has its axis c2 oriented in the direction of coils L1 and L3. They are arranged orthogonally in the same plane as c1 and c3.

The magnetic flux generated by the coil L1 is
Since it passes perpendicular to the second axis c2, it is difficult to link with the winding 22 of the coil L2, and the generation of electromotive force due to electromagnetic induction is suppressed. Similarly, the magnetic flux generated by the coil L2 passes perpendicularly to the axes c1 and c3 of the coils L1 and L3, making it difficult to link with the winding 21 and suppressing the generation of electromotive force. Therefore, the output terminals Lout, Rout
Noise of the audio signal output from the audio signal can be reduced. In the first and second embodiments, the coil L
A similar effect can be obtained even when 1, L2 and L3 are air-core coils.

FIG. 6 is a diagram showing an arrangement of coils of the LPF 4 according to the third embodiment. The same parts as those in the first embodiment in FIG. 4 are denoted by the same reference numerals. Coil L4, L5, L6
Are the Lch coils L11, L12, L13 of the aforementioned Lch of FIG.
And is composed of an endless coil having a ring-shaped magnetic core. Note that the Rch has the same configuration. Coil L4 (first endless coil) and coil L
In the coil L5 (second endless coil), the direction of the axis c5 of the magnetic core is the axis c4, c6 of the core of the coils L4, L6.
Are arranged at right angles to the direction of.

The magnetic flux generated by the coil L4 forcibly passes through the magnetic core. When the current flowing through the winding 21 increases,
Leakage magnetic flux is generated due to magnetic saturation of the magnetic core and the like. At this time,
Since the leakage magnetic flux is generated substantially parallel to the magnetic path surface A4 of the magnetic core, it is difficult to link with the winding 22 of the coil L5, and the generation of electromotive force due to electromagnetic induction is suppressed. Similarly, the leakage magnetic flux generated by the coil L5 is generated substantially in parallel with the magnetic path surface A5 of the magnetic core of the coil L5.
It becomes difficult to link with the winding 21 of L3, and generation of electromotive force is suppressed. Therefore, the noise of the audio signal output from the output terminals Lout and Rout can be reduced.

FIG. 7 is a diagram showing an arrangement of coils of the LPF 4 according to the fourth embodiment. The same parts as those in the third embodiment in FIG. 6 are denoted by the same reference numerals. Coil L4, L5, L6
Are the Lch coils L11, L12, L13 of the aforementioned Lch of FIG.
And is composed of an endless coil having a ring-shaped magnetic core. Note that the Rch has the same configuration. Coil L4 (first endless coil) and coil L
6, the axes c4 and c6 of the respective magnetic cores are arranged on the same straight line. In the coil L5 (second endless coil), the axis c5 of the magnetic core is disposed parallel to the axes c4 and c6 of the magnetic cores of the coils L4 and L6, and has a step in a direction perpendicular to the axis c5.

Since the leakage magnetic flux generated by the coil L4 is generated substantially parallel to the magnetic path surface of the magnetic core and along the magnetic core,
Linkage with the winding 22 of the coil L5 becomes difficult, and the generation of electromotive force due to electromagnetic induction is suppressed. Similarly, the leakage magnetic flux generated by the coil L5 is generated along the magnetic core substantially parallel to the magnetic path surface of the magnetic core of the coil L5.
It becomes difficult to link with the winding 21 of L3, and generation of electromotive force is suppressed. Therefore, the noise of the audio signal output from the output terminals Lout and Rout can be reduced.

FIG. 8 is a diagram showing an arrangement of coils of the LPF 4 according to the fifth embodiment. The same parts as those in the third embodiment in FIG. 6 are denoted by the same reference numerals. Coil L4, L5, L6
Are the Lch coils L11, L12, L13 of the aforementioned Lch of FIG.
, And is composed of an endless coil having a magnetic core of a ring. Note that the Rch has the same configuration. Coil L4 (first endless coil), L5 (second
Endless coils), L6 are the axes c4, c5,
c6 are arranged in parallel. Further, the coil L5 is arranged with a step in the directions of the axes c4, c5, c6 with respect to the coils L4, L6.

The leakage magnetic flux generated by the coil L4 is generated substantially parallel to the magnetic path surface of the magnetic core and along the magnetic core.
By arranging the axes c4, c5, and c6 in parallel, it becomes difficult to interlink with the winding 22 of the coil L5. Also, the coil L
Since 5 has a step, the linkage with the winding 22 becomes more difficult, and the generation of electromotive force due to electromagnetic induction is further suppressed. Similarly, the leakage magnetic flux generated by the coil L5
Are generated along the magnetic core substantially parallel to the magnetic path surface of the magnetic core, and it becomes difficult to interlink the windings 21 of the coils L1 and L3, thereby suppressing generation of electromotive force. Therefore, the output terminals Lout, Rout
Noise of the audio signal output from the audio signal can be reduced.

FIG. 9 is a diagram showing an arrangement of coils of the LPF 4 according to the sixth embodiment. The same parts as those in the first embodiment in FIG. 4 are denoted by the same reference numerals. Coil L1, L2, L3
Are the Lch coils L11, L12, L13 of the aforementioned Lch of FIG.
And a cylindrical coil having a columnar magnetic core. Note that the Rch has the same configuration.

Coil L1 (first cylindrical coil), L2, L
3 is such that the axes c1, c2, c3 of the respective magnetic cores are arranged in parallel, and the coil L2 (second cylindrical coil) is
1, L3 has a step in the direction of the axis c2. As a result, it becomes difficult for the magnetic flux generated by the coil L1 to interlink with the winding 22 of the coil L2, and the generation of electromotive force due to electromagnetic induction is suppressed. Similarly, it is difficult for the leakage flux generated by the coil L2 to interlink with the windings 21 of the coils L1 and L3, and the generation of electromotive force is suppressed. Therefore,
Noise of audio signals output from the output terminals Lout and Rout can be reduced.

FIG. 10 is a diagram showing an arrangement of coils of the LPF 4 according to the seventh embodiment. The same parts as those in the first embodiment in FIG. 4 are denoted by the same reference numerals. Coil L1, L2, L
3 is the Lch coils L11, L12, L1 of the Lch of FIG.
3 are connected in series, and are formed of a cylindrical coil having a columnar magnetic core. Note that the Rch has the same configuration. The axes c1 and c3 of the coils L1 (first cylindrical coil) and L3 are arranged on the same straight line.

The axis c2 of the coil L2 (second cylindrical coil) is disposed parallel to the axes c1 and c3, and the coil L2 is the coil L1.
Has a step in a direction perpendicular to the axis c2. As a result, it becomes difficult for the magnetic flux generated by the coil L1 to interlink with the winding 22 of the coil L2, and the generation of electromotive force due to electromagnetic induction is suppressed. Similarly, it is difficult for the leakage flux generated by the coil L2 to interlink with the windings 21 of the coils L1 and L3, and the generation of electromotive force is suppressed. Therefore, the noise of the audio signal output from the output terminals Lout and Rout can be reduced. In the sixth and seventh embodiments, the same effect can be obtained even when the coils L1, L2, L3 are air-core coils.

FIG. 11 is a diagram showing an arrangement of coils of the LPF 4 according to the eighth embodiment. The same parts as those of the fourth embodiment in FIG. 7 are denoted by the same reference numerals, and the winding is omitted.
This embodiment has the same configuration as the fourth embodiment for Lch and R channel.
The filter device has a filter for the channel. Therefore, the Lch coils L4, L5, and L6 are connected in series corresponding to the coils L11, L12, and L13 in FIG. 2, and the Rch coils L7, L8, and L9 are coils L14, L15, and L16 ( (See FIG. 2).

A shield plate S made of a conductive member is provided between the coils L4, L5, L6 and the coils L7, L8, L9. Thereby, the coils L4, L
5, preventing the leakage magnetic flux from L6 from interlinking with the coils L7, L8, L9, and further suppressing the generation of electromotive force due to electromagnetic induction. Therefore, the output terminals Lout, Ro
The noise of the audio signal output from the ut can be further reduced. The same effect can be obtained by providing a shield plate S between the Lch filter and the Rch filter according to the first to third embodiments and the fifth to seventh embodiments. The same applies to the case of using.

FIG. 12 is a partial detailed view showing the arrangement of the coils of the LPF 4 according to the ninth embodiment. In the present embodiment, for example, the coil L4 of the third embodiment (see FIG. 5) is divided, two coils L4a and L4b are connected in series, and the number of turns of the winding 21 is changed so that the inductance matches the coil L4. I do. As a result, the same current flows through the coils L4a and L4b.

By doing so, the coils L4a, L4b
Can be reduced as compared with the coil L4 of the third embodiment, and the leakage magnetic flux generated from each of the coils L4a and L4b is reduced. Therefore, generation of an electromotive force due to electromagnetic induction can be further suppressed, and noise of an output audio signal can be further reduced. The coils L4a and L4b may be arranged in different directions as in the first to seventh embodiments, or may be arranged with steps.
Note that similar effects can be obtained by the same configuration for the coils L5 and L6, and similar effects can be obtained by dividing the coils of the other embodiments. The same applies to the case where an air-core coil is used.

Although the LPF has been described in the first to ninth embodiments, the HPF (high-pass filter) and the BP
Even in the case of another filter such as F (bandpass filter), the same effect can be obtained by configuring the coil in the same manner as described above.

[0040]

According to the present invention, the magnetic core is provided with the first and second endless coils whose axial directions are orthogonal to each other and adjacent, or the first and second cylindrical coils whose axial directions are orthogonal and adjacent to each other. However, it becomes difficult for the magnetic flux generated by one coil to interlink with the winding of the other coil, and the generation of electromotive force due to electromagnetic induction is suppressed. Therefore, noise of the output signal can be reduced.

According to the present invention, since a plurality of coils are arranged so as to have a step in an adjacent direction, it is difficult for the magnetic flux generated by one coil to interlink with the winding of the other coil. And generation of electromotive force due to electromagnetic induction is suppressed. Therefore, noise of the output signal can be reduced.

Further, according to the present invention, by dividing into a plurality of coils connected in series and carrying the same current so as to obtain a predetermined inductance, the number of turns of each coil is reduced, and the leakage magnetic flux is reduced. You. Therefore, noise of the output signal can be reduced.

Further, according to the present invention, since a shield plate is provided between a plurality of filters, it is possible to prevent an electromotive force caused by electromagnetic induction between filters of a plurality of channels which are input and output independently.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a 1-bit switching amplifier.

FIG. 2 is a circuit diagram showing an LPF of the present invention.

FIG. 3 is a diagram showing a form of a coil.

FIG. 4 is a schematic diagram illustrating an arrangement of coils of the filter according to the first embodiment of the present invention.

FIG. 5 is a schematic diagram showing an arrangement of coils of a filter according to a second embodiment of the present invention.

FIG. 6 is a schematic diagram illustrating an arrangement of coils of a filter according to a third embodiment of the present invention.

FIG. 7 is a schematic diagram showing an arrangement of coils of a filter according to a fourth embodiment of the present invention.

FIG. 8 is a schematic diagram showing an arrangement of coils of a filter according to a fifth embodiment of the present invention.

FIG. 9 is a schematic diagram showing an arrangement of coils of a filter according to a sixth embodiment of the present invention.

FIG. 10 is a schematic diagram illustrating an arrangement of coils of a filter according to a seventh embodiment of the present invention.

FIG. 11 is a schematic diagram illustrating an arrangement of coils of a filter according to an eighth embodiment of the present invention.

FIG. 12 is a schematic diagram illustrating a configuration of a coil of a filter according to a ninth embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 1-bit amplifying device 2 Modulating unit 3 Amplifying unit 4 LPF 5 Audio signal source 6 Speaker 21, 22 Winding L1 to L3 Cylindrical coil L4 to L9, L4a, L4b Endless coil L11 to L16 Coil C11 to C16 Capacitor S Shield plate

Claims (8)

[Claims] 1. A filter comprising first and second endless coils whose magnetic cores have axial axes orthogonal to each other and adjacent to each other. 2. The first, first and second axial directions which are orthogonal to each other and adjacent to each other.
A filter comprising a second cylindrical coil. 3. An endless coil having first and second endless coils adjacent to each other in the axial direction of the magnetic core, wherein the first endless coil and the second endless coil have a step in a direction perpendicular to the axial direction. filter. 4. A first and a second endless coil which are adjacent to each other in a direction perpendicular to the axial direction of the magnetic core, wherein the first and second endless coils have a step in the axial direction. filter. 5. A method according to claim 1, further comprising: first and second cylindrical coils adjacent to each other in the axial direction, wherein the first cylindrical coil and the second cylindrical coil have a step in a direction perpendicular to the axial direction. Filter to do. 6. The first, adjacent in a direction perpendicular to the axial direction,
A filter comprising a second cylindrical coil, wherein the first cylindrical coil and the second cylindrical coil have a step in the axial direction. 7. A filter comprising a plurality of coils connected in series and carrying the same current. 8. A filter device comprising a plurality of filters according to claim 1, wherein a shield plate is provided between the filters.