JP4290644B2 - Filter circuit - Google Patents

Description

  The present invention relates to a filter circuit that suppresses noise propagating on a conductive wire.

  Power electronics devices such as switching power supplies, inverters, lighting circuits for lighting devices, and the like have a power conversion circuit that converts power. The power conversion circuit has a switching circuit that converts direct current into rectangular alternating current. For this reason, the power conversion circuit generates a ripple voltage having a frequency equal to the switching frequency of the switching circuit and noise associated with the switching operation of the switching circuit. This ripple voltage and noise adversely affect other devices. Therefore, it is necessary to provide a means for reducing ripple voltage and noise between the power conversion circuit and another device or line.

  Recently, power line communication has been considered promising as a communication technique used in building a communication network in the home, and its development is being promoted. In power line communication, communication is performed by superimposing a high-frequency signal on the power line. In this power line communication, noise is generated on the power line due to the operation of various electric / electronic devices connected to the power line, which causes a decrease in communication quality such as an increase in error rate. Therefore, a means for reducing noise on the power line is required. In power line communication, it is necessary to prevent a communication signal on the indoor power line from leaking to the outdoor power line.

  Noise that propagates through two conductive lines includes normal mode (differential mode) noise that causes a potential difference between the two conductive lines, and common mode noise that propagates through the two conductive lines in the same phase. There is.

  In order to suppress these noises, it is effective to provide a line filter in a power supply line, a signal line, or the like. As the line filter, a filter including an inductance element (inductor) and a capacitor, a so-called LC filter is often used. The LC filter includes a T-type filter and a π-type filter in addition to one having one inductance element and one capacitor.

  FIG. 11 shows the configuration of a conventional T-type filter. This T-type filter has first and second inductors L101 and L102 connected in series on the conductive wire 103, one end connected between the first and second inductors L101 and L102, and the other end. Is connected to the grounded capacitor C101. The first inductor L101 is formed by winding a first winding 111 made of a conductor around a first core 121 made of a magnetic material. The second inductor L102 is formed by winding a second winding 112 made of a conductor around a second core 122 made of a magnetic material.

  In Patent Document 1, a coil-type inductor having a short ring that is electrically short-circuited is used in a T-type filter in order to realize high-density mounting with less mutual electromagnetic coupling between adjacent inductors. Are listed.

Patent Document 2 describes a low-pass filter composed of three impedance elements. This low-pass filter has the same basic structure as the T-type filter in that three impedance elements are arranged in a T-type. This low-pass filter has two high impedance elements inserted in series on one of two conductive lines, one end connected between the two high impedance elements, and the other end of the two conductive lines. And a low impedance element connected to the other of the two. Each of the two high impedance elements is configured by a parallel connection circuit of a coil and a resistor, and the low impedance element is configured by a capacitor. This low-pass filter reduces normal mode noise.
JP 2003-198305 A (FIG. 1) Japanese Patent Laid-Open No. 5-121988 (FIG. 1)

  However, the conventional LC filter has a specific resonance frequency determined by the inductance and the capacitance, so that a desired attenuation can be obtained only in a narrow frequency range. In particular, in the T-type filter, the attenuation characteristic is changed by changing the degree of coupling between the first inductor L101 and the second inductor L102, and the peak point of the attenuation is changed. Therefore, the peak position of attenuation can be adjusted by changing the values of inductance and capacitance, or by changing the degree of coupling between the inductors. Has the problem of getting worse. Further, in order to bring the peak position to the low frequency side, it is necessary to form a coil having a large inductance value, and the circuit becomes large. With a conventional T-type filter, it is impossible to obtain a broadband attenuation characteristic that maintains a certain amount of attenuation even on the high frequency side with a peak position on the low frequency side. The filters described in Patent Documents 1 and 2 also have the same problems as the conventional T-type filter because the principle of noise reduction is the same as that of the conventional T-type filter.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a filter circuit capable of obtaining a broadband attenuation characteristic that is not obtained with an existing T-type filter or the like with a simple circuit configuration. Is to provide.

A filter circuit according to a first aspect of the present invention includes a first inductor provided on a first conductive line, an inductor and a capacitor connected in series , and one end is connected to one end of the first inductor, A first series circuit connected in parallel to the first inductor by connecting the other end to the other end of the first inductor, one end connected to one end of the first inductor, and the other end grounded And a first capacitor. The first inductor and the inductor of the first series circuit are magnetically coupled.

  In the filter circuit according to the first aspect of the present invention, a series resonant circuit is formed by the inductor and the capacitor of the first series circuit. Since the inductor of the first series circuit is magnetically coupled to the first inductor on the first conductive line, the characteristic of the series resonant circuit is added as a filter characteristic. An attenuation characteristic in a wide band that could not be obtained is obtained.

In the noise suppression circuit according to the first aspect, it is preferable that satisfactory attenuation characteristics in a wide band can be obtained by satisfying the following conditions.
First, when the inductance of the inductor of the first series circuit is L31 and the inductance of the first inductor is L1,
It is preferable that L31 ≧ L1.
Further, when the capacitance of the capacitor of the first series circuit is C31 and the capacitance of the first capacitor is C1,
It is preferable that C1 ≧ C31.

The filter circuit according to the first aspect further includes a second inductor connected in series to the first inductor on the first conductive line, and one end of the first capacitor is the first and second inductors. And the other end may be grounded.
In this case, a T-type filter is constituted by the first and second inductors and the first capacitor. Then, since the inductor of the first series circuit is magnetically coupled to the first inductor, the characteristic of the series resonance circuit can be obtained when the series resonance circuit is connected in parallel to one inductor of the T-type filter. In addition to the filter characteristics of the T-type filter, a broadband attenuation characteristic that was not obtained with the conventional T-type filter can be obtained.

Still further, it includes third and fourth inductors connected in series with each other on the second conductive line, and other inductors and other capacitors connected in series , one end of which is connected to one end of the third inductor. The other end is connected to the other end of the third inductor so that the second series circuit is connected in parallel to the third inductor, and one end is connected between the third and fourth inductors. May be provided with a second capacitor grounded. The second inductor and the fourth inductor are magnetically coupled, and the first inductor, the first series circuit inductor, the third inductor, and the second series circuit inductor are all magnetically coupled to each other. A combined configuration may be used.
In this case, a common mode filter that suppresses common mode noise propagating through the first and second conductive wires in the same phase is configured. In particular, a T-type common mode filter is formed in a portion excluding the first and second series circuits. Since the first inductor, the inductor of the first series circuit, the third inductor, and the inductor of the second series circuit are all magnetically coupled to each other, each conductive line in the T-type common mode filter In a state where a series resonant circuit is connected in parallel to one inductor, the characteristics of the series resonant circuit are added to the filter characteristics of the T-type common mode filter. The attenuation characteristics are obtained.

A filter circuit according to a second aspect of the present invention is a circuit that suppresses normal mode noise that is transmitted by first and second conductive lines and causes a potential difference between these conductive lines. A first inductor and a second inductor connected in series on the conductive line; an inductor and a capacitor connected in series ; one end connected to one end of the first inductor; the other end connected to the other end of the first inductor A first series circuit connected in parallel to the first inductor by being connected to the end, third and fourth inductors connected in series to each other on the second conductive line, and other connected in series It includes inductors and other capacitor has one end connected to one end of a third inductor and the other end connected in parallel to the third inductor by being connected to the other end of the third inductor A second series circuit, one end of which is connected between the first and second inductors, and a capacitor whose other end is connected between the third and fourth inductors. The first inductor and the inductor of the first series circuit are magnetically coupled to each other, and the third inductor and the inductor of the second series circuit are magnetically coupled to each other. is there.

  In the filter circuit according to the second aspect of the present invention, a balanced separation type normal mode filter in which the inductor on the first conductive line and the inductor on the second conductive line are separated is configured. In particular, a balanced separation type T-type normal mode filter is configured in a portion excluding the first and second series circuits. The first inductor and the inductor of the first series circuit are magnetically coupled to each other, and the third inductor and the inductor of the second series circuit are magnetically coupled to each other. When a series resonance circuit is connected in parallel to one inductor on each conductive line in a balanced separation type T-type normal mode filter, the characteristics of the series resonance circuit are added to the filter characteristics of the balanced separation type T-type normal mode filter Thus, it is possible to obtain attenuation characteristics in a wide band that cannot be obtained by the conventional balanced separation type T-type normal mode filter.

In the filter circuit according to the second aspect of the present invention, the first inductor, the inductor of the first series circuit, the third inductor, and the inductor of the second series circuit are all magnetically coupled to each other. May be.
In this case, a balanced coupled normal mode filter in which corresponding inductors between the first and second conductive lines are magnetically coupled to each other is configured. In particular, a balanced-coupled T-type normal mode filter is configured except for the first and second series circuits. The first inductor, the inductor of the first series circuit, the third inductor, and the inductor of the second series circuit are all magnetically coupled to each other, so that each of the balanced coupled T-type normal mode filters In the state where the series resonant circuit is connected in parallel to one inductor on the conductive wire, the characteristic of the series resonant circuit is added to the filter characteristic of the balanced coupled T-type normal mode filter, and the conventional balanced coupled T-type normal is added. A wideband attenuation characteristic not obtained by the mode filter can be obtained.

  According to the filter circuit of the first aspect of the present invention, since the inductor of the first series circuit is magnetically coupled to the first inductor on the first conductive line, the first series circuit is The characteristic of the series resonance circuit by the inductor and capacitor of the first series circuit is added as the filter characteristic to the filter characteristic of the removed portion, and the conventional T with a simple circuit configuration simply by adding the series resonance circuit. It is possible to obtain an attenuation characteristic in a wide band that cannot be obtained with a mold filter or the like.

  According to the filter circuit of the second aspect of the present invention, the first inductor on the first conductive line and the inductor of the first series circuit are magnetically coupled to each other, and the second inductor on the second conductive line is also coupled. Since the inductor 3 and the inductor of the second series circuit are magnetically coupled to each other, the filter characteristics of the normal mode filter excluding the first and second series circuits are the first and second series. The characteristic of the series resonance circuit by the inductor and capacitor of the circuit is added as a filter characteristic, and the conventional T-type normal mode filter has a simple circuit configuration in which a series resonance circuit is added to one inductor on each conductive wire. It is possible to obtain a broadband attenuation characteristic that could not be obtained by the above method.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
First, the filter circuit according to the first embodiment of the present invention will be described. FIG. 1 shows a configuration example of the filter circuit according to the present embodiment. This filter circuit is an unbalanced filter circuit that suppresses normal mode noise. This filter circuit includes first and second inductors L1 and L2 connected in series on the first conductive line 3 between the input / output terminals 1A and 2A, and one end of the first and second inductors L1. , L2 and a first capacitor C1 having the other end grounded. The first inductor L1 is formed by winding the first winding 11 around the first core 21 made of a magnetic material. The second inductor L2 is formed by winding the second winding 12 around the second core 22 made of a magnetic material.

This filter circuit also includes an inductor L31 and a capacitor C31 connected in series, and includes a series circuit 30 connected in parallel to the first inductor L1 as a whole. The inductor L31 and the capacitor C31 constitute a series resonance circuit. The inductor L31 is magnetically coupled to the first inductor L1 by winding the winding 31 around, for example, the first core 21 common to the first winding 11. The series circuit 30 corresponds to a specific example of “first series circuit” in the present invention.
The second inductor L2 may be omitted, and only the first inductor L1 may be provided on the first conductive line 3. In addition, in the series circuit 30, the inductor L31 and the capacitor C31 may be arranged in the opposite manner to the illustrated state. That is, in the illustrated state, one end of the capacitor C31 is connected between the first and second inductors L1 and L2, but the inductor L31 is connected between the first and second inductors L1 and L2. You may do it.

In this filter circuit, the inductance value and capacitance value of each part are set to arbitrary values depending on the purpose of use of the filter and desired characteristics. It is preferable because attenuation characteristics can be obtained. First, when the inductance of the inductor L31 of the series circuit 30 is L31 and the inductance of the first inductor L1 is L1,
L31 ≧ L1
It is preferable that
Further, when the capacitance of the capacitor C31 of the series circuit 30 is C31 and the capacitance of the first capacitor C1 is C1,
C1 ≧ C31
It is preferable that

  As shown in the drawing, when the coupling coefficient indicating the degree of magnetic coupling between the first inductor L1 and the inductor L31 is k1, k1 = 0.99 is preferable. The first and second inductors L1 and L2 are preferably magnetically separated (the coupling coefficient is zero). Note that the superiority of the filter characteristics by satisfying these conditions will be described later with specific examples.

  Next, the operation of this filter circuit will be described.

  In this filter circuit, a portion other than the series circuit 30 (the first and second inductors L1, L2 and the first capacitor C1) constitutes a T-type filter. Since the inductor L31 of the series circuit 30 is magnetically coupled to the first inductor L1, characteristics of the series resonant circuit can be obtained in a state where the series resonant circuit is connected in parallel to one inductor L1 of the T-type filter. Is added to the filter characteristics of the T-type filter. At this time, since the capacitor C31 of the added series resonance circuit does not form a GND (ground) path, the leakage current does not increase in the added circuit portion. As a result, it is possible to obtain an attenuation characteristic in a wide band that cannot be obtained by a conventional T-type filter. In particular, without forming a coil having a large inductance value on the first conductive wire 3 and maintaining the filter characteristics on the high band side well, the peak position of attenuation may be brought on the low band side. It becomes possible. The attenuation characteristics of this filter circuit will be shown below with specific examples.

  FIG. 2 shows that in this filter circuit, the coupling coefficient between the first inductor L1 on the first conductive line 3 and the inductor L31 of the series circuit 30 is k1 = 0.99, and the inductance value of the inductor L31 is changed. It is the figure which calculated and graphed the frequency characteristic of the attenuation amount in the case of. The horizontal axis represents frequency (Hz), and the vertical axis represents attenuation (dB). For comparison, the characteristics of a conventional pure T filter (FIG. 11) without the series resonant circuit 30 are also shown. Note that the inductances of the first and second inductors L1 and L2 are equal to each other, 2 mH, and the capacitance of the first capacitor C1 is set to 2000 pF. 10 pF was set as the stray capacitances of the first and second inductors L1 and L1, respectively. The input / output impedance of the signal was 50Ω. Further, it is assumed that there is no magnetic coupling between the first and second inductors L1 and L2 (the coupling coefficient is zero). The capacitance value of the capacitor C31 in the series circuit 30 was set to 1000 pF so that C1 ≧ C31.

As can be seen from the result of FIG. 2, the presence of the series circuit 30 causes an attenuation peak point on the low frequency side. It can also be seen that the peak position of the attenuation on the low frequency side changes by changing the inductance value of the inductor L31 in the series circuit 30. On the other hand, the high frequency side finally reaches the performance of the conventional pure T filter. Here, when the inductance value of the inductor L31 increases, the peak position of attenuation shifts to the low frequency side, and conversely, the inductance values of the first and second inductors L1 and L2 (in this case, 2 mH) are decreased by decreasing the inductance value. ), The low-frequency peak point approaches the peak point of a pure T-type filter, making it difficult to obtain a broadband attenuation characteristic. From this, it can be seen that L31 ≧ L1 is preferable in order to obtain a good attenuation characteristic in a wide band.
Further, increasing the inductance values of the first and second inductors L1 and L2 means forming a coil having a large inductance value (a large number of turns) on the first conductive wire 3, and increasing the circuit size. In order to avoid this, it is preferable that L1 and L2 are smaller than the inductance value of the series circuit 30.

FIG. 3 shows the attenuation when the coupling coefficient between the first inductor L1 and the inductor L31 of the series circuit 30 is k1 = 0.99 and the capacitance value of the capacitor C31 in the series circuit 30 is changed in this filter circuit. It is the figure which computed and graphed the frequency characteristic of. Inductance value of the inductor L31 in the series circuit 30 was fixed to 4 mH so that L31 ≧ L1. The other calculation conditions are the same as in FIG. As can be seen from the results of FIG. 3, it can be seen that the attenuation peak position on the low frequency side also changes by changing the capacitance value of the capacitor C31 in the series circuit 30. On the other hand, the high frequency side finally reaches the performance of the conventional pure T filter.
Here, when the capacitance value of the capacitor C31 increases and exceeds the capacitance value of the grounded first capacitor C1 (in this case, 2000 pF), in particular, the portion indicated by reference numeral 50 in FIG. Tend to have low attenuation. From this, it can be seen that C1 ≧ C31 is preferable in order to obtain a good attenuation characteristic in a wide band.

FIG. 4 shows the frequency characteristics of the attenuation when the coupling coefficient between the first inductor L1 and the inductor L31 of the series circuit 30 is k1 = 0.999 and the inductance value of the inductor L31 is changed in this filter circuit. It is the figure which computed and graphed. The calculation conditions are the same as in FIG. 2 except that the coupling coefficient k1 is 0.999 and the magnetic coupling degree is set much stronger than in FIG. 2 (k1 = 0.99). . Similarly, FIG. 5 is a graph obtained by calculating the frequency characteristics of attenuation when the coupling coefficient k1 = 0.999 and the magnetic coupling degree is strongly set, and the capacitance value of the capacitor C31 in the series circuit 30 is changed. FIG. The calculation conditions are the same as in the case of FIG. 3 except that the degree of coupling is set strongly.
As can be seen from the results of FIG. 4 and FIG. 5, even when the degree of coupling is set very strong, an attenuation peak appears on the low frequency side as in the case shown in FIG. 2 and FIG. Changing the inductance value or capacitance value at 30 changes its peak position. On the other hand, if the degree of coupling is made too strong in this way, the characteristics indicated by the reference numerals 51 and 52 in FIGS. From this, it can be seen that the coupling coefficient k1 between the first inductor L1 and the inductor L31 of the series circuit 30 is preferably about 0.99 in order to obtain a good attenuation characteristic in a wide band.

FIG. 6 shows the frequency characteristics of attenuation when the coupling coefficient between the first inductor L1 and the inductor L31 of the series circuit 30 is k1 = 0 and the inductance value of the inductor L31 is changed in this filter circuit. FIG. The calculation conditions are the same as in FIG. 2 except that the coupling coefficient k1 is set to 0 and the first inductor L1 and the inductor L31 are magnetically separated. Similarly, FIG. 7 is a graph obtained by calculating the frequency characteristics of the attenuation when the coupling coefficient k1 = 0 is magnetically separated and the capacitance value of the capacitor C31 in the series circuit 30 is changed. Except for the magnetic separation, the calculation conditions are the same as in FIG.
As can be seen from the results of FIG. 6 and FIG. 7, compared to the cases shown in FIGS. 2 and 3 and FIG. 4 and FIG. It turns out that it is hardly obtained. From this, it can be seen that the first inductor L1 and the inductor L31 of the series circuit 30 are preferably magnetically coupled.

As described above, according to the present embodiment, since the inductor L31 of the series circuit 30 is magnetically coupled to the first inductor L on the first conductive wire 3, the series circuit 30 is excluded. The characteristic of the series resonant circuit formed by the inductor L31 and the capacitor C31 of the series circuit 30 is added to the filter characteristic of the portion as the filter characteristic, and the conventional T type can be obtained with a simple circuit configuration simply by adding the series resonant circuit. It is possible to obtain attenuation characteristics in a wide band that could not be obtained with a filter or the like. In particular, it is possible to obtain an attenuation characteristic that forms a peak of attenuation on the low frequency side and that reaches the performance of the T-type filter in the high frequency range.
[Second Embodiment]

  Next, a filter circuit according to a second embodiment of the present invention will be described. The filter circuit according to the present embodiment is a circuit that suppresses common mode noise that propagates through the first and second conductive lines in the same phase.

FIG. 8 shows a configuration example of the filter circuit according to this embodiment. Note that components that are substantially the same as those of the filter circuit in the first embodiment shown in FIG. This filter circuit includes third and fourth inductors L3 and L4 connected in series on the second conductive line 4 between the input / output terminals 1B and 2B in addition to the components shown in FIG. And a second capacitor C2 connected between the third and fourth inductors L3 and L4 and having the other end grounded. The third inductor L3 is formed by winding the third winding 13 around the first core 21 common to the first inductor L1. The fourth inductor L4 is formed by winding the fourth winding 14 around the second core 22 common to the second inductor L2.
The first and third windings 11 and 13 are magnetically coupled to each other so as to cooperate and suppress common mode noise by being wound around a common first core 21. That is, the first and third windings 11 and 13 are oriented so that the magnetic fluxes induced in the first core 21 are offset by the currents flowing through the windings when normal mode current flows through them. Are wound around the first core 21. As described above, the first and third windings 11 and 13 and the first core 21 constitute a common mode choke coil that suppresses common mode noise and allows a normal mode signal to pass. Similarly, the second and fourth windings 12 and 14 are wound around the common second core 22 so as to be magnetically coupled to each other so as to suppress common mode noise in cooperation. The coil is configured.

  This filter circuit also includes another series circuit 40 that includes another inductor L32 and another capacitor C32 connected in series, and is connected in parallel to the third inductor L3 as a whole. The other inductor L32 and the other capacitor C32 form a series resonance circuit, similarly to the inductor L31 and the capacitor C31 in the other series circuit 30. Hereinafter, in the present embodiment, the series circuit 30 connected in parallel to the first inductor L1 is referred to as a first series circuit, and the series circuit 40 connected in parallel to the third inductor L3 is referred to as the second series circuit. This is called a series circuit. In the second series circuit 40, the winding 32 of the inductor L32 has a common first core together with, for example, the first winding 11, the third winding 13, and the winding 31 in the first series circuit 30. 21 is wound. Thereby, the first inductor L1, the inductor L31 of the first series circuit 30, the third inductor L3, and the other inductor L32 of the second series circuit 40 are all magnetically coupled to each other.

  The black circles on each winding in the figure indicate the polarity of the winding and the direction of winding, but the relationship between the windings of the windings and the winding direction of each inductor are combined. As long as it is maintained, it may be reversed to that shown in the figure. Further, the second inductor L2 and the fourth inductor L4 are omitted, and only the first inductor L1 is provided on the first conductive line 3, and the third conductive line 4 is provided with the third inductor L1. A configuration in which only the inductor L3 is provided may be employed. Further, in the first series circuit 30, the inductor L31 and the capacitor C31 may be disposed opposite to the illustrated state. That is, in the illustrated state, one end of the capacitor C31 is connected between the first and second inductors L1 and L2, but the inductor L31 is connected between the first and second inductors L1 and L2. You may do it. The same applies to the other inductor L32 and the other capacitor C32 in the second series circuit 40.

Also in this filter circuit, it is preferable to satisfy the following conditions for the same reason as the filter circuit shown in FIG. That is, when the inductance of the inductor L31 of the first series circuit 30 is L31 and the inductance of the first inductor L1 is L1,
L31 ≧ L1
It is preferable that Similarly, when the inductance of the other inductor L32 of the second series circuit 40 is L32 and the inductance of the third inductor L3 is L3,
L32 ≧ L3
It is preferable that Further, it is preferable that L31 = L32 and L1 = L2 = L3 = L4.

Further, when the capacitance of the capacitor C31 of the first series circuit 30 is C31 and the capacitance of the first capacitor C1 is C1,
C1 ≧ C31
It is preferable that Similarly, when the capacitance of the other capacitor C32 of the second series circuit 40 is C32 and the capacitance of the second capacitor C2 is C2,
C2 ≧ C32
It is preferable that

  Moreover, it is preferable that the set of the first and third inductors L1 and L3 and the set of the second and fourth inductors L2 and L4 are magnetically separated (the coupling coefficient is zero).

In this filter circuit, a T-type common mode filter is configured in a portion excluding the first and second series circuits 30 and 40. Since the first inductor L1, the inductor L31 of the first series circuit 30, the third inductor L3, and the other inductor L32 of the second series circuit 40 are all magnetically coupled to each other, a T-type In a state where the series resonance circuit is connected in parallel to one inductor on each conductive line in the common mode filter, the characteristics of the series resonance circuit are added to the filter characteristics of the T-type common mode filter. As a result, it is possible to obtain a broadband attenuation characteristic that cannot be obtained with a conventional T-type common mode filter. In particular, without forming a coil having a large inductance value on the first and second conductive wires 3 and 4 and maintaining a good filter characteristic on the high band side, the peak position of the attenuation is set on the low band side. It can be brought.
[Third Embodiment]

  Next, a filter circuit according to a third embodiment of the present invention will be described. The filter circuit according to the present embodiment relates to a circuit that suppresses normal mode noise that is transmitted by two conductive lines and causes a potential difference between the conductive lines.

  FIG. 9 shows a configuration example of the filter circuit according to the present embodiment. Note that components that are substantially the same as those of the filter circuit in the first embodiment shown in FIG. This filter circuit includes third and fourth inductors L3 and L4 connected in series on the second conductive line 4 between the input / output terminals 1B and 2B in addition to the components shown in FIG. . The third inductor L <b> 3 is formed by winding the third winding 13 around the third core 23. The fourth inductor L4 is formed by winding the fourth winding 14 around the fourth core 24. In the configuration example of FIG. 1, the other end of the first capacitor C1 is grounded. In this filter circuit, the other end of the first capacitor C1 is connected between the third and fourth inductors L3 and L4. Has been.

  This filter circuit also includes another series circuit 40 that includes another inductor L32 and another capacitor C32 connected in series, and is connected in parallel to the third inductor L3 as a whole. The other inductor L32 and the other capacitor C32 form a series resonance circuit, similarly to the inductor L31 and the capacitor C31 in the other series circuit 30. Hereinafter, in the present embodiment, the series circuit 30 connected in parallel to the first inductor L1 is referred to as a first series circuit, and the series circuit 40 connected in parallel to the third inductor L3 is referred to as the second series circuit. This is called a series circuit. In the second series circuit 40, the winding 32 of the inductor L32 is wound around the common third core 23 together with the third winding 13, for example. Thus, in this filter circuit, the first inductor L1 and the inductor L31 of the first series circuit 30 are magnetically coupled to each other, and the third inductor L3 and the other of the second series circuit 40 The inductor L32 is magnetically coupled to each other.

  The black circles on each winding in the figure indicate the polarity of the winding and the direction of winding, but the relationship between the windings of the windings and the winding direction of each inductor are combined. As long as it is maintained, it may be reversed to that shown in the figure. Further, the second inductor L2 and the fourth inductor L4 are omitted, and only the first inductor L1 is provided on the first conductive line 3, and the third conductive line 4 is provided with the third inductor L1. A configuration in which only the inductor L3 is provided may be employed. Further, in the first series circuit 30, the inductor L31 and the capacitor C31 may be disposed opposite to the illustrated state. That is, in the illustrated state, one end of the capacitor C31 is connected between the first and second inductors L1 and L2, but the inductor L31 is connected between the first and second inductors L1 and L2. You may do it. The same applies to the other inductor L32 and the other capacitor C32 in the second series circuit 40.

Also in this filter circuit, it is preferable to satisfy the following conditions for the same reason as the filter circuit shown in FIG. That is, when the inductance of the inductor L31 of the first series circuit 30 is L31 and the inductance of the first inductor L1 is L1,
L31 ≧ L1
It is preferable that Similarly, when the inductance of the other inductor L32 of the second series circuit 40 is L32 and the inductance of the third inductor L3 is L3,
L32 ≧ L3
It is preferable that Further, it is preferable that L31 = L32 and L1 = L2 = L3 = L4.

Further, when the capacitance of the capacitor C31 of the first series circuit 30 is C31 and the capacitance of the first capacitor C1 is C1,
C1 ≧ C31
It is preferable that Similarly, when the capacitance of the second capacitor C2 is C2,
C2 ≧ C31
It is preferable that

  The first and second inductors L1 and L2 are preferably magnetically separated (coupling coefficient is zero). Similarly, the third and fourth inductors L3 and L4 are preferably magnetically separated (the coupling coefficient is zero).

  In this filter circuit, a balanced-separated normal mode filter in which the inductors L1 and L2 on the first conductive line 3 and the inductors L3 and L4 on the second conductive line 4 are separated is configured. In particular, a balanced separation type T-type normal mode filter is configured in a portion excluding the first and second series circuits 30 and 40. The first inductor L1 and the inductor L31 of the first series circuit 30 are magnetically coupled to each other, and the third inductor L3 and the other inductor L32 of the second series circuit 40 are magnetically coupled to each other. In the state where the series resonance circuit is connected in parallel to one inductor on each conductive line in the balanced separation type T-type normal mode filter, the characteristic of the series resonance circuit is the balanced separation type T type. Added to the filter characteristics of the normal mode filter. As a result, it is possible to obtain an attenuation characteristic in a wide band that cannot be obtained by a conventional balanced separation type T-type normal mode filter. In particular, without forming a coil having a large inductance value on the first and second conductive wires 3 and 4 and maintaining a good filter characteristic on the high band side, the peak position of the attenuation is set on the low band side. It can be brought.

[Fourth Embodiment]

  Next, a filter circuit according to a fourth embodiment of the present invention will be described. The filter circuit according to the present embodiment also relates to a circuit for suppressing normal mode noise, as in the third embodiment. FIG. 10 shows a configuration example of the filter circuit according to the present embodiment. Note that components that are substantially the same as those of the filter circuit according to the third embodiment illustrated in FIG. 9 are denoted by the same reference numerals. This filter circuit is obtained by magnetically coupling the second inductor L2 and the fourth inductor L4 through, for example, the common second core 22 in the filter circuit of FIG. Further, the first inductor L1, the inductor L31 of the first series circuit 30, the third inductor L3, and the other inductor L32 of the second series circuit 40 are all mutually connected, for example, via the common first core 21. It is magnetically coupled. Other configurations are the same as those in FIG.

  In this filter circuit, a balanced coupled normal mode filter in which corresponding inductors between the first and second conductive lines 3 and 4 are magnetically coupled to each other is configured. In particular, a balanced-coupled T-type normal mode filter is configured in a portion excluding the first and second series circuits 30 and 40. Since the first inductor L1, the inductor L31 of the first series circuit 30, the third inductor L3, and the other inductor L32 of the second series circuit 40 are all magnetically coupled to each other, a balanced coupling type When the series resonant circuit is connected in parallel to one inductor on each conductive line in the T-type normal mode filter, the characteristics of the series resonant circuit are added to the filter characteristics of the balanced coupled T-type normal mode filter. As a result, it is possible to obtain an attenuation characteristic in a wide band that cannot be obtained by a conventional balanced coupled T-type normal mode filter. In particular, without forming a coil having a large inductance value on the first and second conductive wires 3 and 4 and maintaining a good filter characteristic on the high band side, the peak position of the attenuation is set on the low band side. It can be brought.

  The filter circuit according to each embodiment reduces the ripple voltage and noise generated by the power conversion circuit, reduces noise on the power line in power line communication, and the communication signal on the indoor power line is applied to the outdoor power line. It can be used as a means for preventing leakage.

  In addition, this invention is not limited to said each embodiment, A various change is possible. For example, the present invention can be applied to all LC filters having an inductor on a line.

1 is a circuit diagram showing a configuration example of a filter circuit according to a first embodiment of the present invention. In the filter circuit according to the first embodiment of the present invention, the frequency of attenuation when the coupling coefficient k1 = 0.99 between the inductor of the series resonant circuit and the inductor on the line is changed and the inductance of the series resonant circuit is changed. It is the figure which calculated the characteristic and made it the graph. In the filter circuit according to the first embodiment of the present invention, the frequency of attenuation when the coupling coefficient k1 of the inductor of the series resonant circuit and the inductor on the line is set to 0.99 and the capacitance of the series resonant circuit is changed. It is the figure which calculated the characteristic and made it the graph. In the filter circuit according to the first embodiment of the present invention, the frequency of attenuation when the coupling coefficient k1 = 0.999 of the inductor of the series resonant circuit and the inductor on the line is changed and the inductance of the series resonant circuit is changed. It is the figure which calculated the characteristic and made it the graph. In the filter circuit according to the first embodiment of the present invention, the frequency of attenuation when the coupling coefficient k1 = 0.999 of the inductor of the series resonant circuit and the inductor on the line is changed and the capacitance of the series resonant circuit is changed. It is the figure which calculated the characteristic and made it the graph. In the filter circuit according to the first embodiment of the present invention, the frequency characteristic of the attenuation when the coupling coefficient k1 = 0 between the inductor of the series resonant circuit and the inductor on the line is changed and the inductance of the series resonant circuit is changed. It is the figure calculated and graphed. In the filter circuit according to the first embodiment of the present invention, the frequency characteristic of the attenuation when the coupling coefficient k1 = 0 between the inductor of the series resonant circuit and the inductor on the line is changed and the capacitance of the series resonant circuit is changed. It is the figure calculated and graphed. It is a circuit diagram which shows one structural example of the filter circuit which concerns on the 2nd Embodiment of this invention. It is a circuit diagram showing an example of 1 composition of a filter circuit concerning a 3rd embodiment of the present invention. It is a circuit diagram which shows one structural example of the filter circuit which concerns on the 4th Embodiment of this invention. It is a circuit diagram which shows the structure of the conventional T type filter.

Explanation of symbols

C1 ... 1st capacitor, L1 ... 1st inductor, L2 ... 2nd inductor, L3 ... 3rd inductor, L4 ... 4th inductor, L31 ... Inductor, C31 ... Capacitor, 3 ... 1st conductive wire DESCRIPTION OF SYMBOLS 4 ... 2nd conductive wire, 11 ... 1st winding, 12 ... 2nd winding, 13 ... 3rd winding, 14 ... 4th winding, 21 ... 1st core, 22 ... 2nd core, 30 ... 1st series circuit, 31 ... Winding, 32 ... Other windings, 40 ... 2nd series circuit.

Claims (7)

A first inductor provided on the first conductive line;
Including an inductor and a capacitor connected in series , one end connected to one end of the first inductor and the other end connected to the other end of the first inductor to be connected in parallel to the first inductor A first series circuit;
A first capacitor having one end connected to one end of the first inductor and the other end grounded;
The filter circuit, wherein the first inductor and the inductor of the first series circuit are magnetically coupled. When the inductance of the inductor of the first series circuit is L31 and the inductance of the first inductor is L1,
L31 ≧ L1
The filter circuit according to claim 1, wherein: When the capacitance of the capacitor of the first series circuit is C31 and the capacitance of the first capacitor is C1,
C1 ≧ C31
The filter circuit according to claim 1 or 2, wherein: A second inductor connected in series with the first inductor on the first conductive line;
4. The filter circuit according to claim 1, wherein one end of the first capacitor is connected between the first and second inductors, and the other end is grounded. 5. Third and fourth inductors connected in series with each other on the second conductive line;
The other inductor and the other capacitor connected in series are included , and one end is connected to one end of the third inductor and the other end is connected to the other end of the third inductor. A second series circuit connected in parallel;
A second capacitor having one end connected between the third and fourth inductors and the other end grounded;
The second inductor and the fourth inductor are magnetically coupled;
5. The first inductor, the inductor of the first series circuit, the third inductor, and the inductor of the second series circuit are all magnetically coupled to each other. Filter circuit. A circuit that suppresses normal mode noise that is transmitted by first and second conductive lines and causes a potential difference between the conductive lines,
First and second inductors connected in series with each other on a first conductive line;
Including an inductor and a capacitor connected in series , one end connected to one end of the first inductor and the other end connected to the other end of the first inductor to be connected in parallel to the first inductor A first series circuit;
Third and fourth inductors connected in series with each other on the second conductive line;
Including the other inductor and the other capacitor connected in series , one end is connected to one end of the third inductor, and the other end is connected to the other end of the third inductor, whereby the third inductor A second series circuit connected in parallel;
A capacitor having one end connected between the first and second inductors and the other end connected between the third and fourth inductors;
The first inductor and the inductor of the first series circuit are magnetically coupled to each other, and the third inductor and the inductor of the second series circuit are magnetically coupled to each other. A filter circuit characterized by that. The first inductor, the inductor of the first series circuit, the third inductor, and the inductor of the second series circuit are all magnetically coupled to each other. Filter circuit.

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