JP2005094611A - Power supply noise reducing filter, power unit, method for designing the power supply noise reducing filter, and choke coil with resistance component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply noise reducing filter which enables a reproduced sound to be surely outputted from a loudspeaker without deteriorating sound quality while reducing power supply noise even when, for example, there is load fluctuation such as output volume fluctuation of the loudspeaker in a car audio system. <P>SOLUTION: Circuit conditions of the filter are designed so that impedance Z<SB>AB</SB>of the filter near a cutoff frequency f<SB>c</SB>does not increase abruptly. Namely, the cutoff frequency f<SB>c</SB>exists within an audible sound band and while carrying out noise reduction, predetermined attenuation characteristics can be satisfactorily realized in a frequency band of or higher than the cutoff frequency f<SB>c</SB>. Furthermore, a power supply noise reducing filter 110A is composed of a choke coil 11a capable of suppressing the abrupt increase in impedance in the frequency of the audible sound band and having new inductance and a capacitor 12a having capacitance. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a power supply noise removing filter and a power supply apparatus having a power supply noise removing filter.
In particular, the present invention relates to an electrical equipment that receives power from an alternator (generator) of a vehicle, such as an in-vehicle audio device, and removes the noise of the alternator and does not become a secondary noise source in a load portion or the like. The present invention relates to a noise removal filter and a power supply apparatus having such a power supply noise removal filter.
The present invention further relates to a method for designing a power supply noise elimination filter.
The present invention also relates to a choke coil with a resistance component that is suitably used for a power supply noise removing filter.

A vehicle electrical system will be described with reference to FIG. 1 as an example in which the power supply noise removing filter and power supply apparatus of the present invention are provided.
The in-vehicle electric system circuit 100 illustrated in FIG. 1 includes a starter (starter) 101 that rotates and starts an engine (internal combustion engine) 102, and a secondary storage battery (battery) 104 that supplies power to the starter 101. An alternator (generator) 103 that generates electric power by rotation, a voltage adjustment circuit 105 that adjusts a voltage generated by the alternator 103, and an electrical load circuit 106 are provided. When the secondary storage battery (battery) 104 is not fully charged, the secondary storage battery 104 is charged with the power generated by the alternator 103.
The voltage adjustment circuit 105 adjusts the voltage generated by the alternator 103 to various levels of voltage required by the electric load circuit 106 (level conversion) and outputs the voltage to the electric load circuit 106. The voltage adjustment circuit 105 can include a smoothing circuit that smoothes the pulsation component of the voltage generated by the alternator 103 as necessary.

There are various loads as the electrical load circuit 106. For example, an air conditioner, an audio device, and a lighting fixture.
FIG. 2 is a diagram illustrating an electric circuit related to an audio device as an example of the electrical load circuit 106.
The audio device 130 includes, for example, a CD changer (not shown), a reproduction unit (player) 131, an amplifier circuit 132, and a speaker 133.
The audio device 130 requires a stable power source that does not contain harmonic components from other electrical loads in order to maintain the CD rotation speed constant and stabilize the clock frequency for signal processing of reproduced sound. Is done.

As a power supply device of such an audio device 130, for example, as described in Japanese Utility Model Laid-Open No. 5-40055, a power supply noise removing filter using a choke coil and a capacitor is provided. The configuration and purpose of the power supply noise removal filter will be described with reference to the power supply noise removal filter 110 illustrated in FIG.
The relationship between the power supply noise removal filter and the power supply device is, for example, as shown in FIG. 2, a combination of the power supply noise removal filter 110 and the voltage adjustment circuit 120 is called a power supply device. The filter 110 itself is referred to as a power supply noise removing filter.

Since the alternator 103 is rotated at a high speed by the engine 102 to generate electric power, noise due to the high speed rotation is generated. As such, since the noise component is an audible sound band, for example, about 1 kHz, and becomes noise of the audio device 130, the power supply of the audio device 130 has a stable power (for example, Voltage) is desired.
As described above, the power supply of the audio device 130 has different conditions from those of an electric load circuit such as an air conditioner, and voltage stabilization and noise countermeasures using the power supply noise removing filter 110 are required. No. 40055 or a power source noise removing filter using a choke coil and a capacitor having a circuit configuration illustrated in FIG.

FIG. 3 is a graph showing an example of attenuation characteristics desired as the power supply noise elimination filter 110 illustrated in FIG.
The power supply noise removal filter 110 is designed to have a characteristic having a cutoff frequency ω _c (or f _c ) and a predetermined attenuation amount G at the first frequency (reference current number frequency) f1.
The power supply cutoff frequency ω _c of the power supply noise removal filter included in the power supply of the in-vehicle audio device 130 is defined based on the frequency of the noise component of the alternator 103. The noise frequency of the audio device 130 is typically in the audible sound band.

  When providing the audio device 130 with the voltage from which noise has been removed by the power supply noise removal filter 110, the voltage adjustment circuit 120 uses various voltages used in the audio device 130, such as voltage levels for driving the playback unit (player) 131, A voltage required at various points in the audio device 130 such as a voltage level for driving the speaker 133 is generated.

Japanese Utility Model Publication No. 5-40055

The values of the choke coil 111 and the capacitor (capacitor) 112 in the power supply noise removal filter 110 are set so as to have the attenuation characteristic illustrated in FIG. 3, and the power supply noise removal filter 110 is used as the power supply of the audio device 130. However, the speaker 133 of the audio device 130 has encountered a phenomenon in which sound with degraded sound quality (deteriorated or lowered) is output. Accordingly, there has been a demand for improving the sound quality to be desired for such deterioration of sound quality.
As will be described in detail later, such deterioration in sound quality is caused by a power supply noise removal filter originally provided for noise countermeasures when the load fluctuates greatly, for example, when the speaker volume changes greatly. There was found.

One of the objects of the present invention is to provide a power supply device for the audio device 130 in which a desired reproduction sound is output from the audio device 130 or a power supply noise removal filter included in the power supply device with respect to the above-described examples. It is in.
Of course, the present invention is not limited to the noise countermeasures of the alternator 103, and is not limited to the audio device 130. However, the present invention is inherently applicable to a device that can remove or reduce various noises but cannot exhibit desired characteristics due to load fluctuations. It is an object of the present invention to provide a power supply device or a power supply noise elimination filter that can exhibit the above characteristics.

The inventor of the present application analyzed the generation of the above-described deteriorated reproduced sound. As a result, although the power supply noise removing filter 110 was originally manufactured to have the characteristics of FIG. 3, the attenuation characteristics are actually satisfied near the cutoff frequency ω _c as illustrated in FIG. It was confirmed that the characteristics were not possible.
The main cause of the attenuation characteristic illustrated in FIG. 4 is that the power supply noise removal filter 110 is secondary to the fluctuation in volume output from the speaker 133, that is, the load fluctuation viewed from the power supply noise removal filter 110. It turned out to be a noise source.
For example, the fluctuation of the current flowing through the speaker 133 due to the magnitude of the sound is 10 times or more. Due to such a large load fluctuation, the power supply noise elimination filter 110 originally provided for the noise countermeasure of the alternator 103 becomes an obstacle to the load fluctuation and becomes a secondary noise source. Has been found by the present inventors.

The detailed analysis results will be described with reference to FIGS.
FIG. 5A is an equivalent circuit diagram of the circuit illustrated in FIG. V1 indicates the secondary storage battery (battery) 104, R1 indicates the resistance value of the feed line 107, L1 indicates the inductance of the choke coil 111, C1 indicates the capacitance of the capacitor (capacitor) 112, and R2 is from the speaker 133. The change in the value of the current flowing through the speaker 133 according to the volume of the output sound (current change ΔI1) is shown as the resistance value of the variable resistor in which the resistance change is replaced.
FIG. 5B is an equivalent circuit diagram of only an AC component in the equivalent circuit illustrated in FIG. The impedance Z _AB viewed from the terminal _AB is expressed by the following formula.

[Equation 1]
Z _AB = (R1 + jωL1) / (1-ω ² L1 · C1 + jωC1 · R1)
... (1)

  In order to reduce power loss as much as possible, the resistance value of the feed line 107 is designed to be as low as possible. Therefore, assuming that R1 is approximately 0, equation (1) can be expressed as the following equation (2).

[Equation 2]
Z _AB = (jωL1) / (1-ω ² L1 · C1)
... (2)

6A is a characteristic diagram showing an attenuation G (vertical axis) when the frequency (horizontal axis) is changed with respect to Equation (2), and FIG. 6B is a characteristic diagram with respect to Equation (2). FIG. 6 is a characteristic diagram showing a change in impedance Z _AB when the axis) is changed.
Illustrated As apparent from FIG. 6 (B), the impedance Z _AB is rapidly increased in the vicinity of the cutoff frequency f _c. As a result, it is understood that the current of the designed value does not flow to the speaker 133 due to the increase of the impedance Z _{AB and} the sound quality of the sound output from the speaker 133 is deteriorated (deteriorated).

A sharp rise in the impedance Z _AB is, it becomes particularly difficult occurring at a cut-off frequency f _c vicinity of audible sound in the band.
For example, simply, the audible sound region, for example, if a rapid rise in impedance Z _AB near the cutoff frequency f _c occurs, as a countermeasure, as a power source noise removing filter for noise suppression of the audio device 130 it can take measures such as removing the cut-off frequency f _c to the outside of the audible sound band.
However, the power supply noise removing filter 110 is originally and provided to remove the noise by the alternator 103 rotates, do not put on the outside of the audible sound band cut-off frequency f _c, to take action as described above I can't.

Accordingly, the inventors have, for example, the power supply noise rejection filter or power supply for an audio device 130, if there is a cut-off frequency f _c to audible sound in the band, for example, while performing noise removal of the alternator 103 , to satisfy that realizes a predetermined attenuation characteristic at the cut-off frequency f _c or more frequency bands, further have found that it must suppress an abrupt rise in impedance at the frequency of the audible sound band.
Of course, as a power supply noise removing filter or power supply device applied to the in-vehicle audio device 130 or the like, naturally, dimensional restrictions and price restrictions are imposed. However, the above-described problem is solved under such restrictions.

As a method for realizing such a problem, the present inventors have found that it can be realized by taking the following measures.
(1) To find a novel circuit configuration capable of suppressing the increase in the impedance Z _AB while removing external noise such as the noise of the alternator 103 and satisfying a predetermined attenuation characteristic.
(2) To find improved circuit conditions capable of suppressing the increase in the impedance Z _AB while removing external noise such as the noise of the alternator 103 and satisfying a predetermined attenuation characteristic.
(3) Combining (1) and (2) above.

  According to a first aspect of the present invention, there is provided a power supply noise removing filter in which an inductance element having inductance and a capacitor element having capacitance are connected in series, wherein the inductance of the inductance element and the capacitor of the capacitor element are: The audible sound region has a cut-off frequency for removing power supply noise, exhibits a predetermined attenuation characteristic, and has little change in impedance with respect to fluctuations in the load subsequent to the filter for removing power supply noise. Provided is a power supply noise removing filter that is defined to have low sharpness.

Preferably, the capacitor component is increased and the inductance component is decreased within a range that satisfies the resonance condition of the cutoff frequency so that the shape of the sharpness becomes a predetermined shape. .
By doing so, the original attenuation characteristic of the power supply noise removing filter can be maintained.

  According to a second aspect of the present invention, there is provided a power supply noise removal filter in which a resistance element having a predetermined resistance value is connected in series with the inductance element of the power supply noise removal filter.

Preferably, in the inductance element and the resistance element, an inductance component is canceled, and a bifilar winding portion showing the predetermined resistance value and a single winding portion showing the inductance value are wound around a magnetic core, As a choke coil with components, it is integrally configured.
When such an integrally configured choke coil with a resistance component is used, the mounting dimensions are reduced and the assembling work is simplified.

  According to the third aspect of the present invention, a first filter unit in which a first inductance element having a first inductance and a first capacitor element having a first capacitance are connected in series, and a second filter having a second inductance. A power source noise removing filter having an inductance element and a second capacitor element having a second capacitance connected in series, and having a second filter part connected in series with the first filter part. It has a cutoff frequency for power supply noise removal, exhibits a predetermined attenuation characteristic, has little change in impedance with respect to fluctuations in the subsequent stage of the power supply noise removal filter, and has low sharpness at the cutoff frequency As described above, the first inductance of the first inductance element and the first capacitor of the first capacitor element. Sita, and said second inductance and the second second capacitor is defined, the power supply noise rejection filter capacitor element of the second inductance element is provided.

  According to the 4th viewpoint of this invention, the power supply device which has a filter for power supply noise removal in any one of the above is provided.

According to the present invention, the above-described problems can be solved without increasing the size of the power supply noise removing filter or the power supply device and without increasing the price.
For example, when the power supply noise removing filter of the present invention is applied to an in-vehicle audio device, deterioration of sound quality from a speaker can be improved.

[First embodiment]
A first embodiment of the power supply noise elimination filter of the present invention will be described with reference to FIG.
The power supply noise removing filter 110A illustrated in FIG. 7 includes a choke coil 11a and a capacitor (capacitor) 12a.
The power supply noise removal filter 110A illustrated in FIG. 7 has the same circuit configuration as the power supply noise removal filter 110 illustrated in FIG. 2, but the circuit design conditions are completely different as described in detail below.
That is, the power supply noise removal filter 110 illustrated in FIG. 2 assumes that the impedance of the power supply noise removal filter does not change over the frequency domain, and the inductance of the choke coil 111 is the circuit constant with only the noise countermeasure of the alternator 103 taken. The capacitance of the capacitor (capacitor) 112 is set.
On the other hand, the power supply noise removal filter 110A illustrated in FIG. 7 is completely different in the design concept of the power supply noise removal filter. That is, as described above, (1) under the condition that the cut-off frequency f _c is present in audible sound in band, (2) while performing noise removal of the alternator 103, (3) cut-off frequency f _c or more (4) In addition, an inductance L1 of the choke coil 11a and a capacitor (capacitor) so as to suppress a sudden increase in impedance at a frequency within the audible sound. The capacitance C1 of 12a is defined, and (5) severe conditions are imposed to design a power supply noise elimination filter comprising such a choke coil 11a and a capacitor 12a.
Incidentally, the cut-off frequency f _c is defined by equation (3) indicating the resonance frequency below.

[Equation 3]
Cut-off frequency f _c = 1 / (2π (L1 · C1) ^1/2 )
... (3)

FIG. 8 is a characteristic diagram of an experimental example of the power supply noise elimination filter of FIG.
The inductance L1 of the choke coil 11a and the capacitance C1 of the capacitor 12a constituting the power supply noise elimination filter 110A are shown under the following circuit conditions shown in [Table 1] and with the cutoff frequency f _c = 250 kHz fixed. As shown in 2], the attenuation characteristics were obtained by changing as appropriate.
As a result of using such a power supply noise removing filter 110A, the sound quality of the speaker 133 is normal without deterioration (deterioration) as in the prior art.

[Table 1]
Circuit condition 1
Resistance value of power supply line 107 = 50 mΩ
Load resistance of speaker 133 = 10Ω

[Table 2]
Inductance L1 (μH) Capacitance C1 (μF)
Curve A1 180 2200
Curve A2 80 4700
Curve A3 50 7500
Curve A4 25 15000

In the present embodiment, since the fixed cutoff frequency f _c, a range of conditions of the formula (3), conceivable various combinations and inductance L1 and capacitance C1. However, it is necessary to consider the practical use of aspects such as price, dimensions, and manufacturable range. The combination of the inductance L1 and the capacitance C1 in [Table 2] shows an example selected by the present inventor through trial and error under such consideration.

While satisfying the same resonance condition, the attenuation characteristic curves are different as A1 to A4.
In the exemplary illustration, the cut-off frequency f abnormal attenuation due to a sharp rise in the impedance Z _AB mentioned above in the vicinity of _c (attenuation shortage) does not occur, the attenuation reference frequency f1, for example, 20 dB at 1kHz The above attenuation is realized.
In this example, it has been found that the circuit constant of the power supply noise removing filter 110A may be set in the range of inductance L1 = 50 to 25 (μH) and capacitance C1 = 7500 to 15000 (μF).

The inventor of the present application considers the case of the curves A3 and A4 in which preferable attenuation characteristics are obtained while satisfying the circuit condition of the expression (3), and the curves A1 and A2 in which sufficient attenuation is not obtained. It has been found that this is due to the sharpness Q value.
In general, the sharpness Q is defined by Equation (4).

[Equation 4]
Q = 1 / R × (L / C) ^1/2
... (4)

  In the first embodiment, the resistance value of the power supply line 107 is 0 and the resistance component R in the equation (4) is not considered, but as illustrated in FIG. 9, the value of the capacitance C1 is increased, If various combinations of reducing the value of the inductance L1 are appropriately performed, for example, while satisfying the resonance characteristic of the expression (3), for example, while realizing the noise countermeasure of the alternator 103, the secondary to the audio device 130 is achieved. A power supply noise removing filter 110A that does not become a noise source can be realized.

Thus, the circuit constants of the power source noise removing filter 110A of the first embodiment, while satisfying the resonance condition frequency noise to be removed as a cut-off frequency f _c, the shape of the sharpness Q, curve Q1 It has been found that it is desirable to set the circuit constant so that the width is wide and the peak is low as shown by the curve Q2.
Therefore, as the first embodiment of the present invention, a power supply noise removing filter is realized with such circuit constants.

  As described above, the power supply noise removal filter of the first embodiment is the same as the conventional power supply noise removal filter in the equivalent circuit configuration. However, as described above, the circuit design method is completely different from the conventional technology. Such a novel circuit design method of the present invention is a novel technical idea that a person skilled in the art cannot easily conceive. Therefore, the values of the inductance L1 of the choke coil 11a and the capacitance C1 of the capacitor 12a constituting the power supply noise elimination filter are not merely a matter of design.

[Second Embodiment]
A second embodiment of the power supply noise removing filter of the present invention will be described with reference to FIG.
A power supply noise elimination filter 110B as the second embodiment illustrated in FIG. 10 includes a choke coil 11b, a capacitor (capacitor) 12b, and a resistance component (element) 13.
The power supply noise removing filter 110B as the second embodiment illustrated in FIG. 10 is different from the power supply noise removing filter 110A as the first embodiment illustrated in FIG. Component) 13 is added. The significance of this will be described below.

In the above-described consideration, since the resistance component of the feeder line 107 is assumed to be almost zero (actually, as illustrated in the first embodiment, the resistance value of the feeder line 107 is about 50 mΩ, but this is ignored as zero. It has been found that the impedance Z _AB suddenly increases near the cutoff frequency ω _{c and} the phenomenon occurs because the current flowing through the speaker 133 is limited (or suppressed).
Therefore, in the second embodiment, the additional resistance component (element) 13 is intentionally provided in the power supply noise elimination filter 110B to suppress a rapid increase in the impedance Z _AB within the audible sound band. Such a technical idea is an invention that cannot be easily conceived by those skilled in the art because it is a reversal of the common general knowledge that resistance components usually cause power loss and bring about undesirable results of heating.

Of course, the power supply line 107 desirably has a value close to 0 in order to reduce power loss in the power supply path as much as possible. As described above, the resistance value of the power supply line 107 is about 50 mΩ.
However, the inventor of the present application has found that a resistance value of the power supply line 107 of about 50 mΩ is insufficient for the measures of the present invention. Therefore, the second embodiment is applied only to each power supply portion that requires countermeasures, such as only the power supply device for the audio device 130, or to the power supply noise removal filter portion, and the additional resistance component (element) 13 is applied. Decided to establish.

  Also in the second embodiment, the series resonance condition is defined by Expression (3). The sharpness Q is defined by equation (4).

With reference to FIGS. 11A and 11B, a preferred resistance component choke coil 14 in which the additional resistance component (element) 13 and the choke coil 11b are combined will be described.
As illustrated in FIG. 11A, as the resistance component choke coil 14, a winding composed of a bifilar (turned twice) winding portion 14a and a single winding portion 14b is prepared and wound around a magnetic core (not shown). To do.
The bifilar winding portion 14a is folded with the winding start portion w3 as a reference, and the folded bifilar winding portion 14a is wound, for example, for the first winding number T1. When the winding of the bifilar winding portion 14a is completed, the single winding portion 14b is wound, for example, for the second winding number T2. Then, the choke coil 14 with a resistance component illustrated in FIG. 11B is completed.

FIG. 12 is an equivalent circuit diagram of the choke coil 14 with a resistance component.
Since the bifilar winding portion 14a wound around the magnetic core by the first winding number T1 is folded back, the winding direction is reversed and cancels, and the inductance component is zero. However, a predetermined length corresponding to the first winding number T1 is present as the resistance component R.
On the other hand, the single winding portion 14b is wound around the magnetic core by the second winding number T2 so as to satisfy the inductance L1.
Such a choke coil 14 with a resistance component has the same shape as a conventional choke coil, and has a smaller size and a simpler connection man-hour than when an additional resistance component (element) 13 is added. There are also advantages in terms of implementation.

As a method of producing the same effect as the choke coil 14 with resistance component described above, a choke coil is manufactured using a wire having a large resistance value, for example, iron, and the resistance value and inductance similar to those of the choke coil 14 with resistance component are obtained. A choke coil can be manufactured. Alternatively, the choke coil can be manufactured using a wire having a smaller cross section and a larger resistance value.
Normally, it is desirable that the choke coil has a small resistance component and a desired inductance is obtained. However, in the second embodiment of the present invention, it is desirable to use a choke coil having a predetermined resistance value as described above. .

FIG. 13 is a characteristic diagram of the power supply noise elimination filter according to the second embodiment of the present invention with reference to FIG.
In this example, the choke coil 11b as shown in [Table 3] is used under the same circuit conditions as shown in [Table 1] and the condition where the cutoff frequency f _c = 250 kHz is fixed. In the state where the inductance L1 of the capacitor and the capacitance C1 of the capacitor 12b are fixed to the circuit condition 2 satisfying the expression (3), the resistance value R of the additional resistance component (element) 13 is changed as shown in [Table 4]. The attenuation characteristics were obtained for the cases.
Even when such a power supply noise removing filter 110B of the second embodiment is used, the deterioration of the sound quality of the speaker 133 is improved.

[Table 3]
L1 = 180μH
C1 = 2200μF

[Table 4]
Resistance value R (mΩ) Remarks
Curve B1 0 Same as conventional technology
Curve B2 150
Curve B3 300
Curve B4 500

Curve B1 is an example of the prior art and is illustrated as a comparative example.
In the exemplary curve B2 to B4, when adding additional resistance component (element) 13 of a certain size of the resistance value, the attenuation due to a sharp rise in impedance Z _AB described above the cut-off frequency f _c vicinity Abnormality (insufficient attenuation) does not occur, and an attenuation amount of 20 dB or more is realized at the attenuation reference frequency f1, for example, 1 kHz. This 1 kHz is the frequency of noise to be removed in the present embodiment.

When the resistance value R of the additional resistive component (element) 13 is too large, for example, it becomes more than the resistance value R = 500Emuomega curves B4, the cut-off frequency f _c is reduced to about 100 Hz. Thus, when imposing the condition that to maintain the cut-off frequency f _c, the resistance value R of the additional resistive component (element) 13 is also, in the exemplary illustration, it is understood that a range of about 150~500mΩ is optimal.
Such a condition can be understood by applying the second embodiment with respect to the sharpness Q of Equation (4). That is, it can be seen that the relationship between the resistance value R, the inductance L1, and the capacitance C1 includes a range of conditions that satisfy the desired sharpness Q.

Modified Example of Second Embodiment The example described above with reference to FIG. 13 shows that the inductance L1 of the choke coil 11b and the capacitance C1 of the capacitor 12b are fixed as shown in [Table 3]. 4], the case where the resistance value of the additional resistance component (element) 13 is changed has been described. However, in the present invention, the inductance L1 of the choke coil 11b, the capacitance C1 of the capacitor 12b, and the additional resistance The resistance value R of the component (element) 13 can be set as appropriate as long as the conditions of the expressions (2) and (3) are satisfied.
For example, from the viewpoint of reducing power loss, it is desirable that the resistance value R of the additional resistance component (element) 13 is as small as possible within the range allowed by the above conditions. Under such conditions, the inductance L1 of the choke coil 11b and the capacitance C1 of the capacitor 12b can be appropriately determined.

[Third Embodiment]
A third embodiment of the power supply noise elimination filter of the present invention will be described with reference to FIG.
A power supply noise removal filter 110C as the third embodiment illustrated in FIG. 14 is configured by arranging the power supply noise removal filter 110A of the first embodiment described with reference to FIG. 7 in two stages. The first stage choke coil 11c and the first stage filter (capacitor) 12c are composed of a first stage filter, and the second stage choke coil 11d and the second stage capacitor (capacitor) 12d are composed of a second stage filter.
The power supply noise removal filter 110C in FIG. 14 has a more complicated circuit configuration than the power supply noise removal filter 110A in FIG. 7, but the number of circuit elements is increased. By setting, a circuit suitable for various conditions can be realized.

  Note that the series resonance condition in the third embodiment is different from the equation (3), and the sharpness Q is different from the equation (4), but the same as when the equations (3) and (4) are derived. In principle, the third embodiment is the same as the first and second embodiments because it can be derived.

First Example FIG. 15 is a characteristic diagram of a first example of the power supply noise removing filter according to the third embodiment.
The first example is the same circuit conditions as shown in Table 1 and the conditions for fixing the cutoff frequency f _c = 250 kHz as in the first embodiment. Further, for simplification, the first stage choke coil 11c is used. When the inductance L1 and the second-stage choke coil 11d same west, and the capacitance C1 of the first stage capacitor 12c and the second stage capacitor 12d in the same, the resonance condition (cut-off frequency f _c conditions) and the sharpness Q As shown in [Table 5], combinations of inductance L1 and capacitance C1 for satisfying are shown attenuation characteristics obtained for various changes.
Even when such a power supply noise removing filter 110C is used, the deterioration (deterioration) of the sound quality of the speaker 133 is improved.

[Table 5]
Inductance L1 (μH) Capacitance C1 (μF)
Curve C1 180 1000
Curve C2 80 2200
Curve C3 40 4700
Curve C4 25 6800

Comparing the curves C1 to C4 with the curves A1 to A4 illustrated in FIG. 8, the curves C1 to C4 have a large attenuation at the attenuation reference frequency f1 = 1 kHz. However, the attenuation characteristic of the higher 600~700Hz region than the cutoff frequency f _c is non-linear. Furthermore, the amount of attenuation around the cutoff frequency f _c = 250 Hz is not sufficient.
On the other hand, comparing Table 5 with Table 2, the capacitance C1 (μF) in Table 5 is as small as about half that of the same inductance L1 (μH).

Second Example FIG. 16 is a characteristic diagram of a second example of the power supply noise removing filter of the third embodiment.
Similar to the first example, the second example has the same circuit conditions as shown in [Table 1] as in the first embodiment, and like the second example, the first stage choke coil 11c and the second stage are simplified for the sake of simplicity. When the inductance L1 of the stage choke coil 11d is the same, the capacitance C1 of the first stage capacitor 12c and the second stage capacitor 12d is the same, the value of the capacitance C1 is fixed, and the value of the inductance L1 is changed The obtained attenuation characteristics are shown.
Even when such a power supply noise removing filter 110C is used, the deterioration (deterioration) of the sound quality of the speaker 133 is improved.

[Table 6]
Inductance L1 (μH) Capacitance C1 (μF)
Curve D1 180 1000
Curve D2 50 1000
Curve D3 10 1000
Curve D4 5 1000

Cut-off frequency f _c is varied between the curved D1 to D4.
However, the curve D3, D4 is the cut-off frequency f _c is 1 kHz, show good attenuation characteristic attenuation reference frequency f1 = 10 kHz. That is, in this example, when the capacitance C1 = 1000 (μF), the inductance L1 is preferably in the range of 5 to 10 (μH).

[Modification of Third Embodiment]
In implementing the third embodiment, instead of the first stage choke coil 11c and the second stage choke coil 11d, the additional resistance component (element) 13 illustrated in FIG. 10 is replaced by the same method as in the second embodiment. A circuit connected to the choke coil 11b can be used.

As a preferred embodiment of the present invention described above, the sound quality deterioration of the in-vehicle audio device 130 is exemplified, and the power noise removal filter or the power supply device for the audio device 130 is described as a preferred example. However, the application of the power supply noise removing filter and the power supply apparatus of the present invention is not limited to the audio apparatus 130.
For example, a noise (external noise) from a power supply noise removing filter such as the alternator 103 or a device existing outside the power supply device is not removed, so that a predetermined attenuation characteristic is satisfied. In the case where a power source noise removing filter that can be a secondary noise source is not a noise source, it can be applied as a power source noise removing filter or a power source device for a device having a large load fluctuation.

  The choke coil 14 with a resistance component described in relation to the second embodiment is not limited to application to the embodiment of the present invention, and can be widely used as an inductance element that requires a resistance value.

FIG. 1 is a configuration diagram of an electric circuit for a vehicle as an example to which a power supply noise removing filter and a power supply device of the present invention can be applied. FIG. 2 is a block diagram of an audio device as an example of a load in the vehicle electric circuit illustrated in FIG. FIG. 3 is a diagram of attenuation characteristics desired as a power supply device of the audio device illustrated in FIG. 2 or a filter for removing power supply noise in the power supply device. FIG. 4 is an actual attenuation characteristic diagram as an example of the power supply noise elimination filter of the audio apparatus illustrated in FIG. 5A is an equivalent circuit diagram of the circuit illustrated in FIG. 2, and FIG. 5B is an equivalent circuit diagram of only the AC component in the equivalent circuit illustrated in FIG. 5A. 6A is a diagram showing an example of attenuation characteristics of the equivalent circuit of FIG. 5B, and FIG. 6B is a diagram showing examples of impedance characteristics of the equivalent circuit of FIG. 5B. FIG. 7 is a circuit configuration diagram of a power supply noise removal filter as a first embodiment of the power supply noise removal filter and power supply apparatus of the present invention. FIG. 8 is a diagram showing an example of attenuation characteristics of the power supply noise elimination filter of the first embodiment illustrated in FIG. FIG. 9 is a graph showing the sharpness. FIG. 10 is a circuit configuration diagram of a power supply noise removal filter as a second embodiment of the power supply noise removal filter and power supply apparatus of the present invention. FIGS. 11A and 11B are diagrams illustrating a choke coil with a resistance component by integrating the resistance element and the choke coil illustrated in FIG. 10. FIG. 12 is an equivalent circuit of the choke coil with resistance component illustrated in FIG. FIG. 13 is a diagram showing an example of attenuation characteristics of the power supply noise elimination filter of the second embodiment illustrated in FIG. FIG. 14 is a circuit configuration diagram of a power supply noise removal filter as a third embodiment of the power supply noise removal filter and power supply apparatus of the present invention. FIG. 15 is a diagram illustrating a first attenuation characteristic example of the power supply noise elimination filter of the third embodiment illustrated in FIG. FIG. 16 is a diagram showing a second attenuation characteristic example of the power supply noise elimination filter of the third embodiment illustrated in FIG.

Explanation of symbols

100 ・ ・ In-vehicle electrical circuit
101 ··· Starter, 102 ··· Engine
103 .. Alternator, 104 .. Secondary battery (battery)
105 .. Voltage adjustment circuit, 106 .. Electrical load circuit 110 .. Power supply noise elimination filter
111 .. Choke coil, 112 .. Capacitor
120 .. Voltage adjustment circuit 130 .. Audio device
131 .. Playback unit (player)
132 ·· Amplifier circuit, 133 ·· Speaker 110A ·· Power supply noise elimination filter
11a ... choke coil, 12a ... capacitor (capacitor)
110B ... Filter for removing power supply noise
11b ... choke coil, 12b ... capacitor (capacitor)
13. Additional resistance component (element)
14. Choke coil with resistance component
14a ・ Bifiler winding part
14b ... 1 roll part
w1 .. first takeout part, w2 .. second takeout part
w3 .. Winding start part 110C .. Power supply noise elimination filter
11c .. First stage choke coil, 12c .. First stage capacitor
11d ... Second stage choke coil, 12d ... Second stage capacitor

Claims (13)

A power supply noise removing filter in which an inductance element having inductance and a capacitor element having capacitance are connected in series,
The inductance of the inductance element and the capacitor of the capacitor element have a cutoff frequency for removing power source noise in the audible sound region, exhibit a predetermined attenuation characteristic, and with respect to fluctuations in the load after the power source noise removing filter. Is also defined that the change in impedance is small and the sharpness at the cutoff frequency is low,
Power supply noise filter. The capacitor component of the capacitor element is increased and the inductance component of the inductance element is decreased within a range that satisfies the resonance condition of the cutoff frequency so that the shape of the sharpness becomes a predetermined shape. Features
The power supply noise removing filter according to claim 1. A resistance element having a predetermined resistance value is connected in series with the inductance element of the power supply noise elimination filter.
The power supply noise removing filter according to claim 1. In the inductance element and the resistance element, an inductance component of the inductance element is offset, and a bifilar winding portion showing the predetermined resistance value and a single winding portion showing the inductance value are wound around a magnetic core. Being integrated,
The power supply noise removing filter according to claim 3. The resistance value of the resistance element is set within a predetermined range and not more than a predetermined value so that the shape of the sharpness becomes a predetermined shape,
The power supply noise removing filter according to claim 3 or 4. A first filter unit in which a first inductance element having a first inductance and a first capacitor element having a first capacitance are connected in series;
A power supply noise removing filter comprising: a second inductance element having a second inductance; and a second capacitor element having a second capacitance connected in series; and a second filter part connected in series to the first filter part. There,
It has a cut-off frequency for removing power noise in the audible sound region, shows a predetermined attenuation characteristic, has little change in impedance with respect to fluctuations in the subsequent stage of the filter for removing power noise, and is sharp at the cut-off frequency. So that the degree is low,
A first inductance of the first inductance element and a first capacitor of the first capacitor element; a second inductance of the second inductance element; and a second capacitor of the second capacitor element;
Power supply noise filter. The first capacitor is increased, the first inductance is decreased, the second capacitor is increased, and the second capacitor is increased within a range that satisfies the resonance condition of the cutoff frequency so that the shape of the sharpness becomes a predetermined shape. 2Inductance is reduced,
The power supply noise removing filter according to claim 6. A first resistance element having a predetermined resistance value is connected in series with the first inductance element of the power supply noise elimination filter, and a second resistance element having a predetermined resistance value is connected in series with the second inductance element. ,
The power supply noise removing filter according to claim 6 or 7. The first inductance element and the first resistance element have an inductance component canceled out, and a bifilar winding portion showing the predetermined resistance value and a single winding portion showing the inductance value are wound around a magnetic core to form an integrated structure Has been
The second inductance element and the second resistance element have an inductance component canceled out, and a bifilar winding portion showing the predetermined resistance value and a single winding portion showing the inductance value are wound around a magnetic core and integrated. Being
The power supply noise removing filter according to claim 8. The load includes a speaker of an audio device in which a flow current varies greatly according to a change in output volume,
The cut-off frequency exists in the frequency range of the sound output from the speaker,
The attenuation characteristic is a characteristic indicating a predetermined attenuation amount at an attenuation reference frequency higher than the cutoff frequency.
The filter for power supply noise removal in any one of Claims 1-9.   The power supply device which has a filter for power supply noise removal in any one of Claims 1-10. A design method of a power supply noise removing filter in which an inductance element having inductance and a capacitor element having capacitance are connected in series,
It has a cut-off frequency for removing power noise in the audible sound region, shows a predetermined attenuation characteristic, has little change in impedance with respect to fluctuations in the subsequent stage of the filter for removing power noise, and is sharp at the cut-off frequency. Designing the inductance of the inductance element and the capacitor of the capacitor element so as to reduce the degree,
Design method for power supply noise elimination filter. Inductance is offset, and a bifilar winding portion showing the predetermined resistance value and a single winding portion showing the inductance component are integrally wound around a magnetic core,
Choke coil with resistance component.

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