JP2004080436A - Common-mode signal suppressing circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a common-mode signal suppressing circuit capable of efficiently suppressing common mode signals over a wide frequency range, and of being miniaturized. <P>SOLUTION: The common mode signal suppressing circuit is provided with a first winding 11 inserted into a conductive wire 3; a second winding 12 inserted into a conductive wire 4, connected to the first winding 11 via a magnetic core 10 and cooperating with the first winding 11 in suppressing a common mode signal; and a third winding 13 connected to the first and second windings 11, 12 via the magnetic core 10. The common-mode signal suppressing circuit is also provided with an inverse-phase signal transmitting circuit 15, connected to the third winding 13 and connected to the conductive wires 3, 4. The circuit 15 detects the common-mode signals on the conductive wires 3, 4, and supplies inverted signals, having a phase which is to be inverse with respect to the common mode signals, to the third winding 13. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a common mode signal suppression circuit that suppresses a common mode signal that propagates in two conductive lines with the same phase.
[0002]
[Prior art]
Power electronics devices such as switching power supplies, inverters, and lighting circuits of lighting devices have power conversion circuits that convert power. The power conversion circuit has a switching circuit that converts a direct current into a rectangular wave alternating current. Therefore, the power conversion circuit generates a ripple voltage having a frequency equal to the switching frequency of the switching circuit and noise accompanying the switching operation of the switching circuit. The 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.
[0003]
As means for reducing ripple voltage and noise, a filter including an inductance element (inductor) and a capacitor, a so-called LC filter, is often used. LC filters include a T-type filter, a π-type filter, and the like, in addition to a filter having one inductance element and one capacitor. A general noise filter for electromagnetic interference (EMI) is also a kind of LC filter. A general EMI filter is configured by combining discrete elements such as a common mode choke coil, a normal mode choke coil, an X capacitor, and a Y capacitor.
[0004]
In recent years, power line communication has been regarded as promising as a communication technology used when constructing a communication network in a home, and its development is being promoted. In power line communication, communication is performed by superimposing a high frequency signal on a 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 an error rate. Therefore, means for reducing noise on the power line is required. In power line communication, it is necessary to prevent a communication signal on an indoor power line from leaking to an outdoor power line. An LC filter is also used as a means for reducing such noise on a power line or preventing a communication signal on an indoor power line from leaking to an outdoor power line.
[0005]
The noise that propagates through two conductive lines includes a normal mode noise that causes a potential difference between the two conductive lines and a common mode noise that propagates the two conductive lines in the same phase.
[0006]
Here, FIG. 10 shows an example of a configuration of an LC filter for reducing common mode noise. This LC filter includes a pair of terminals 101a and 101b, another pair of terminals 102a and 102b, a common mode choke coil 103 provided between the terminals 101a and 101b and the terminals 102a and 102b, and one end of the terminal 101a. And a capacitor 104 having the other end grounded, and a capacitor 105 having one end connected to the terminal 101b and the other end grounded.
[0007]
The common mode choke coil 103 has one magnetic core 103a and two windings 103b and 103c wound around the magnetic core 103a. One end of the winding 103b is connected to the terminal 101a, and the other end is connected to the terminal 102a. One end of the winding 103c is connected to the terminal 101b, and the other end is connected to the terminal 102b. The windings 103b and 103c are oriented in such a manner that when a normal mode current flows through the windings 103b and 103c, the magnetic fluxes induced in the magnetic core 103a by the currents flowing through the windings 103b and 103c cancel each other. Wound around the core 103a.
[0008]
The LC filter shown in FIG. 10 is inserted in the middle of two conductive wires that transport power. The terminals 101a and 102a are connected to one conductive line, and the terminals 101b and 102b are connected to the other conductive line.
[0009]
[Problems to be solved by the invention]
A conventional LC filter has a problem that a desired attenuation amount can be obtained only in a narrow frequency range because the LC filter has a unique resonance frequency determined by inductance and capacitance.
[0010]
In addition, a filter inserted into a conductive wire for power transport is required to obtain desired characteristics while a current for power transport is flowing and to take measures against temperature rise. Therefore, in such a filter, there is a problem that the inductance element becomes large in order to realize desired characteristics.
[0011]
The present invention has been made in view of such a problem, and an object of the present invention is to provide a common mode signal suppressing circuit that can effectively suppress a common mode signal in a wide frequency range and that can be downsized.
[0012]
[Means for Solving the Problems]
The common mode signal suppression circuit of the present invention is a circuit that suppresses a common mode signal that propagates two conductive lines in the same phase,
A first winding inserted into one of the conductive wires at a predetermined first position;
A second winding inserted into the other conductive line and coupled to the first winding at a second position corresponding to the first position and cooperating with the first winding to suppress a common mode signal. Lines and,
A third winding coupled to the first and second windings such that mutual inductance occurs between the first and second windings;
The third winding is connected to one of the conductive wires at a third position different from the first position, and further corresponds to the third position and is different from the second position at a fourth position. And a reverse-phase signal transmitting means for transmitting a reverse-phase signal for suppressing a common mode signal at a position indicated by the reference numeral.
[0013]
In the common mode signal suppression circuit according to the present invention, the source of the common mode signal is a position other than the position between the first position and the third position and the position between the second position and the fourth position. If the first and second positions are closer to the third and fourth positions than the first and second positions, the negative-phase signal transmitting means detects the common mode signal and outputs a negative-phase signal to the detected common mode signal. Is supplied to the third winding, and the third winding injects the reversed-phase signal into the two conductive lines via the first winding and the second winding. Thereby, in the two conductive lines, the common mode signal is suppressed in the traveling direction of the common mode signal from the first and second positions.
[0014]
Further, in the common mode signal suppressing circuit according to the present invention, the generation source of the common mode signal excludes a position between the first position and the third position and a position between the second position and the fourth position. When the third winding is located closer to the first and second positions than the third and fourth positions, the third winding detects the common mode signal, An antiphase signal having an antiphase to the common mode signal detected by the winding is injected into the two conductive lines. Thereby, in the two conductive lines, the common mode signal is suppressed ahead of the third and fourth positions in the traveling direction of the common mode signal.
[0015]
The common mode signal suppression circuit of the present invention is further provided at a position between the first position and the third position and a position between the second position and the fourth position on the two conductive lines. And an impedance element for reducing the peak value of the passing common mode signal.
[0016]
Further, in the common mode signal suppressing circuit of the present invention, the anti-phase signal transmission means may have a high-pass filter for passing the common mode signal. This high-pass filter may include a capacitor.
[0017]
In the common mode signal suppressing circuit according to the present invention, the impedance element is connected to the fourth winding inserted into the one conductive line and the fourth winding inserted into the other conductive line and connected to the fourth winding. A fifth winding that suppresses a common mode signal in cooperation with the fourth winding may be provided. Each inductance of the fourth winding and the fifth winding may be 0.3 μH or more.
[0018]
Further, in the common mode signal suppression circuit of the present invention, the coupling coefficient between the first winding, the second winding, and the third winding may be 0.7 or more.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[First Embodiment]
FIG. 1 is a circuit diagram showing a basic configuration of a common mode signal suppression circuit according to a first embodiment of the present invention. The common mode signal suppression circuit according to the present embodiment includes a pair of terminals 1a and 1b, another pair of terminals 2a and 2b, a conductive line 3 connecting the terminals 1a and 2a, and a connection between the terminals 1b and 2b. And a conductive line 4 to be connected. The common mode signal suppression circuit is connected to a power line that transports AC power or DC power. The power line includes two power conductive lines. The common mode signal suppression circuit is inserted between the two power conductive lines. Terminals 1a and 2a are connected to one power conductive line, and terminals 1b and 2b are connected to the other power conductive line. The source of the common mode signal to be suppressed by the common mode signal suppression circuit is connected to the terminals 1a and 1b or the terminals 2a and 2b. Therefore, the common mode signal to be suppressed is input to the common mode signal suppression circuit from the terminals 1a and 1b or the terminals 2a and 2b.
[0020]
Here, the common mode signal is a signal that propagates through two power conductive lines in the same phase. Common mode signals to be suppressed include noise and unnecessary communication signals.
[0021]
The common mode signal suppression circuit further includes a first winding 11 inserted into the conductive line 3 at a predetermined first position A, and a conductive line 4 at a second position B corresponding to the first position A. A second winding 12 that is inserted and coupled to the first winding 11 through the magnetic core 10 and cooperates with the first winding 11 to suppress a common mode signal; And a third winding 13 coupled to the first winding 11 and the second winding 12 via the magnetic core 10 so that mutual inductance is generated between the first winding 11 and the second winding 12. It has. For example, the winding numbers of the windings 11, 12, 13 are equal. The magnetic core 10, the first winding 11, and the second winding 12 constitute a common mode choke coil. That is, the windings 11 and 12 are oriented in such a manner that when a normal mode current flows through the windings 11 and 12, the magnetic fluxes induced in the magnetic core 10 by the currents flowing through the windings 11 and 12 cancel each other. , Wound around the magnetic core 10. Thereby, the windings 11 and 12 suppress the common mode signal and allow the normal mode signal to pass.
[0022]
The common mode signal suppression circuit is further connected to the third winding 13 and to the conductive line 3 at a third position C different from the first position A, and further connected to the third position C. And a negative-phase signal transmission circuit 15 connected to the conductive line 4 at a fourth position D different from the second position B and transmitting a negative-phase signal for suppressing a common mode signal. The anti-phase signal transmission circuit 15 has first to third terminals. The first terminal is connected to the conductive line 3 at a third position C. The second terminal is connected to the conductive line 4 at a fourth position D. The third terminal is connected to one end of the third winding 13. The other end of the third winding 13 is grounded. The reverse phase signal transmission circuit 15 corresponds to the reverse phase signal transmission means of the present invention.
[0023]
FIG. 2 is a circuit diagram showing an example of a specific configuration of the common mode signal suppression circuit shown in FIG. In this example, the negative-phase signal transmission circuit 15 includes a high-pass filter 15A that passes a signal having a frequency equal to or higher than a predetermined value among common mode signals or negative-phase signals. The high-pass filter 15A includes capacitors 151 and 152. One end of the capacitor 151 is connected to the conductive line 3 at a position C. One end of the capacitor 152 is connected to the conductive line 4 at the position D. The other end of the capacitor 151 and the other end of the capacitor 152 are connected to one end of the third winding 13.
[0024]
Next, the operation of the common mode signal suppression circuit according to the present embodiment will be described. First, except for the position between the first position A and the third position C and the position between the second position B and the fourth position D, the common mode signal The operation of the common mode signal suppression circuit in the case where the position is closer to the third and fourth positions C and D than the positions A and B of FIG. In this case, the anti-phase signal transmission circuit 15 detects the common mode signal at the third and fourth positions C and D, and outputs the anti-phase signal having the anti-phase to the detected common mode signal to the third and fourth positions C and D. 3 winding 13. The third winding 13 transmits the negative-phase signal to the two conductive lines 3 and 4 via the first winding 11 and the second winding 12 at the first and second positions A and B. inject. As a result, in the two conductive lines 3 and 4, the common mode signal is suppressed ahead of the first and second positions A and B in the traveling direction of the common mode signal.
[0025]
Next, the sources of the common mode signal are the third and the third except for the position between the first position A and the third position C and the position between the second position B and the fourth position D. The operation of the common mode signal suppression circuit when the position is closer to the first and second positions A and B than the fourth positions C and D will be described. In this case, the third winding 13 detects a common mode signal on the conductive lines 3 and 4 at the first and second positions A and B. The negative-phase signal transmission circuit 15 outputs a negative-phase signal having a reverse phase to the common mode signal detected by the third winding 13 at the third and fourth positions C and D to the two conductive lines 3. , 4. As a result, in the two conductive lines 3 and 4, the common mode signal is suppressed ahead of the third and fourth positions C and D in the traveling direction of the common mode signal.
[0026]
Next, with reference to FIG. 3, the principle of suppressing the common mode signal by the common mode signal suppressing circuit according to the present embodiment will be described. Here, a case where the source of the common mode signal is located closer to the third and fourth positions C and D than the first and second positions A and B will be described. FIG. 3 shows a common mode signal suppression circuit having a configuration similar to that of FIG. In the following description, the impedance of the high-pass filter 15A (capacitors 151 and 152) is 0, the number of turns of each of the windings 11 to 13 is equal, and the coupling coefficient between the windings 11 and 12 and the winding 13 is Assume that it is 1.
[0027]
Here, in the common mode signal suppression circuit shown in FIG. 3, a case where a common mode signal causing a potential difference Vin with respect to the potential of the ground GND is input to the terminals 1a and 1b will be considered. When the frequency of the common mode signal is within the pass band of the high-pass filter 15A, the common mode signal passes through the high-pass filter 15A, and at that time, the phase is shifted by 180 ° due to the action of the capacitors 151 and 152. As a result, a potential difference -Vin occurs between both ends of the third winding 13. In accordance with the potential difference -Vin generated between both ends of the third winding 13, a potential difference -Vin is also generated between both ends of the first winding 11 and between both ends of the second winding 12. Assuming that the difference between the potential of the ground GND and the potentials of the terminals 2a and 2b is Vo, this is represented by the following equation.
[0028]
Vo = Vin + (− Vin) = 0
[0029]
Thus, according to the common mode signal suppressing circuit shown in FIG. 3, if the impedance of the high-pass filter 15A is 0 and the coupling coefficient between the windings 11, 12 and 13 is 1, The common mode signal can be completely removed regardless of the frequency within the pass band of 15A. However, in practice, the impedance of the high-pass filter 15A does not become 0, and the coupling coefficient between the windings 11, 12 and the winding 13 becomes smaller than 1. Therefore, the common mode signal cannot be completely removed by the common mode signal suppression circuit shown in FIG. Nevertheless, according to the present embodiment, it is possible to realize a common mode signal suppression circuit that can effectively suppress a common mode signal in a wide frequency range and can be reduced in size with a simple configuration.
[0030]
Hereinafter, the operation of the common mode signal suppression circuit according to the present embodiment will be described in detail with reference to FIG. FIG. 4 shows only a part of the common mode signal suppression circuit shown in FIG. 2 which is related to suppression of a signal passing through the conductive line 3. The circuit shown in FIG. 4 includes terminals 1a and 2a, a first winding 11, a third winding 13, and a capacitor 151. Further, a common mode signal generation source 21 and a load 22 are connected to the circuit shown in FIG. The common mode signal generation source 21 is connected between the terminal 1a and the ground GND, and generates a potential difference Vin between the two. The load 22 is connected between the terminal 2a and the ground GND, and has an impedance Zo.
[0031]
In the circuit shown in FIG. 4, the inductance of the third winding 13 is L11, the inductance of the first winding 11 is L12, and the capacitance of the capacitor 151 is C1. The current passing through the capacitor 151 and the third winding 13 is represented by i1, and the total impedance of the path of the current i1 is represented by Z1. The current passing through the first winding 11 is denoted by i2, and the total impedance of the path of the current i2 is denoted by Z2.
[0032]
The mutual inductance between the first winding 11 and the third winding 13 is represented by M, and the coupling coefficient between them is represented by K. The coupling coefficient K is represented by the following equation (1).
[0033]
K = M / √ (L11 · L12) (1)
[0034]
The sums Z1 and Z2 of the impedances are expressed by the following equations (2) and (3), respectively. Note that j represents √ (−1), and ω represents the angular frequency of the common mode signal.
[0035]
Z1 = j (ωL11-1 / ωC1) (2)
Z2 = Zo + jωL12 (3)
[0036]
The potential difference Vin is represented by the following equations (4) and (5).
[0037]
Vin = Z1 · i1 + jωM · i2 (4)
Vin = Z2 · i2 + jωM · i1 (5)
[0038]
Hereinafter, based on the expressions (2) to (5), an expression representing the current i2 without including the current i1 is obtained. For this purpose, first, the following equation (6) is derived from the equation (4).
[0039]
i1 = (Vin−jωM · i2) / Z1 (6)
[0040]
Next, when the equation (6) is substituted into the equation (5), the following equation (7) is obtained.
[0041]
i2 = Vin (Z1-jωM) / (Z1 · Z2 + ω ² ・ M ² …… (7)
[0042]
It can be said that suppressing the common mode signal by the circuit shown in FIG. 4 means reducing the current i2 represented by the equation (7). According to equation (7), if the denominator on the right side of equation (7) increases, the current i2 decreases. Therefore, the denominator (Z1 · Z2 + ω) ² ・ M ² ) Is considered.
[0043]
First, since Z1 is represented by equation (2), Z1 increases as the inductance L11 of the third winding 13 increases, and Z1 increases as the capacitance C1 of the capacitor 151 increases.
[0044]
Next, since Z2 is represented by Expression (3), the larger the inductance L12 of the first winding 11 is, the larger Z2 is. Therefore, if the inductance L12 is increased, the current i2 can be reduced.
[0045]
Also, the denominator on the right side of equation (7) is ω ² ・ M ² Is included, the current i2 can be reduced by increasing the mutual inductance M. As can be seen from equation (1), the coupling coefficient K is proportional to the mutual inductance M. Therefore, if the coupling coefficient K is increased, the effect of suppressing the common mode signal by the circuit shown in FIG. 4 increases. Since the mutual inductance M is included in the denominator on the right side of the equation (7) in the form of a square, the effect of suppressing the common mode signal greatly changes depending on the value of the coupling coefficient K.
[0046]
The above description similarly applies to a part of the common mode signal suppression circuit shown in FIG. 2 which relates to suppression of a signal passing through the conductive line 4.
[0047]
When the source of the common mode signal is located closer to the first and second positions A and B than the third and fourth positions C and D, the phase of the third winding 13 is reversed. The role of the signal transmission circuit 15 is reversed from that described with reference to FIGS. However, in this case as well, the above description applies equally.
[0048]
As described above, according to the present embodiment, it is possible to realize a common mode signal suppression circuit that can effectively suppress a common mode signal in a wide frequency range and that can be downsized.
[0049]
Further, according to the present embodiment, it is possible to realize a common mode signal suppressing circuit having a large effect of suppressing a common mode signal while having a reduced number of components and being inexpensive as compared with a conventional EMI filter.
[0050]
Further, in the present embodiment, when the anti-phase signal transmission circuit 15 is configured using the capacitors 151 and 152, the detection of the common mode signal and the detection of the common mode signal are performed only by the capacitors 151 and 152. On the other hand, it is possible to generate a reverse-phase signal having a reverse phase. Therefore, in this case, the number of parts can be further reduced.
[0051]
Note that the common mode signal suppression circuit according to the present embodiment includes a means for reducing ripple voltage and noise generated by the power conversion circuit, a method for reducing noise on a power line in power line communication, and a method for reducing a communication signal on an indoor power line. It can be used as a means for preventing leakage to the outdoor power line.
[0052]
[Second embodiment]
FIG. 5 is a circuit diagram showing a basic configuration of a common mode signal suppression circuit according to the second embodiment of the present invention. The common mode signal suppression circuit according to the present embodiment has a configuration in which an impedance element 16 is added to the common mode signal suppression circuit according to the first embodiment. The impedance element 16 is provided at a position between the first position A and the third position C and a position between the second position B and the fourth position D on the conductive wires 3 and 4. Further, the impedance element 16 reduces the peak value of the common mode signal passing therethrough. Thereby, in the common mode signal suppressing circuit according to the present embodiment, the peak value of the common mode signal propagating via the impedance element 16 and injected into the conductive lines 3 and 4 via the antiphase signal transmission circuit 15 The difference from the peak value of the inverted phase signal to be performed is reduced. As a result, according to the common mode signal suppression circuit according to the present embodiment, it becomes possible to more effectively suppress the common mode signal in a wider frequency range.
[0053]
FIG. 6 is a circuit diagram showing an example of a specific configuration of the common mode signal suppression circuit shown in FIG. In this example, as in the example shown in FIG. 2, the anti-phase signal transmission circuit 15 includes a high-pass filter 15A. The high-pass filter 15A includes capacitors 151 and 152.
[0054]
In the example shown in FIG. 6, the impedance element 16 includes a fourth winding 161 inserted into the conductive wire 3 and a fourth winding 161 inserted into the conductive wire 4 and via the magnetic core 160. And a fifth winding 162 which cooperates with the fourth winding 161 to suppress the common mode signal. For example, the winding numbers of the windings 161 and 162 are equal. The magnetic core 160 and the windings 161 and 162 constitute a common mode choke coil. That is, the windings 161 and 162 are oriented in such a manner that when a normal mode current flows through the windings 161 and 162, the magnetic fluxes induced in the magnetic core 160 by the currents flowing through the windings 161 and 162 cancel each other. Are wound around the magnetic core 160. Thus, the windings 161 and 162 suppress the common mode signal and allow the normal mode signal to pass.
[0055]
Hereinafter, the operation of the common mode signal suppression circuit according to the present embodiment will be described in detail with reference to FIG. FIG. 7 shows only a part of the common mode signal suppression circuit shown in FIG. 6 which is related to suppression of a signal passing through the conductive line 3. The circuit shown in FIG. 7 includes terminals 1a and 2a, a first winding 11, a third winding 13, a capacitor 151, and a fourth winding 161. Further, a common mode signal generation source 21 and a load 22 are connected to the circuit shown in FIG. The common mode signal generation source 21 is connected between the terminal 1a and the ground GND, and generates a potential difference Vin between the two. The load 22 is connected between the terminal 2a and the ground GND, and has an impedance Zo.
[0056]
In the circuit shown in FIG. 7, the inductance of the third winding 13 is L11, the inductance of the first winding 11 is L12, the capacitance of the capacitor 151 is C1, and the inductance of the fourth winding 161 is L21. And The current passing through the capacitor 151 and the third winding 13 is represented by i1, and the total impedance of the path of the current i1 is represented by Z1. The current passing through the fourth winding 161 and the first winding 11 is denoted by i2, and the total impedance of the path of the current i2 is denoted by Z2. The mutual inductance between the first winding 11 and the third winding 13 is represented by M, and the coupling coefficient between them is represented by K. The coupling coefficient K is represented by the above equation (1).
[0057]
In the present embodiment, the total impedance Z1 is represented by the above equation (2), and the total impedance Z2 is represented by the following equation (8).
[0058]
Z2 = Zo + jω (L12 + L21) (8)
[0059]
Further, the potential difference Vin is represented by the above-described equations (4) and (5). Similarly to the first embodiment, in the present embodiment, the equation representing the current i2 without including the current i1 is the above-described equation (7).
[0060]
It can be said that suppressing the common mode signal by the circuit shown in FIG. 7 is to reduce the current i2 represented by the equation (7). According to equation (7), if the denominator on the right side of equation (7) increases, the current i2 decreases. Therefore, the denominator (Z1 · Z2 + ω) ² ・ M ² ) Is considered.
[0061]
First, since Z1 is represented by equation (2), Z1 increases as the inductance L11 of the third winding 13 increases, and Z1 increases as the capacitance C1 of the capacitor 151 increases. This is the same as in the first embodiment.
[0062]
Next, in the circuit shown in FIG. 7, since Z2 is represented by equation (8), Z2 increases as the sum of the inductance L12 of the first winding 11 and the inductance L21 of the fourth winding 161 increases. . Therefore, if at least one of the inductance L12 and the inductance L21 is increased, the current i2 can be reduced. From the equation (7), it can be seen that the common mode signal can be suppressed by only the first winding 11, but the common mode signal can be further suppressed by adding the fourth winding 161.
[0063]
As in the first embodiment, the current i2 can be reduced by increasing the mutual inductance M.
[0064]
The above description similarly applies to a part of the common mode signal suppression circuit shown in FIG. 6 which relates to suppression of a signal passing through the conductive line 4.
[0065]
Further, when the source of the common mode signal is located closer to the first and second positions A and B than the third and fourth positions C and D, the phase of the third winding 13 is reversed. The role of the signal transmission circuit 15 is reversed from that described with reference to FIG. However, in this case as well, the above description applies equally.
[0066]
Next, with reference to FIG. 8, a description will be given of a result of a simulation of the relationship between the inductances of the windings 161 and 162 and the common mode signal suppressing effect in the common mode signal suppressing circuit illustrated in FIG. 6. FIG. 8 shows the frequency characteristics of the gain obtained by simulation for each of the circuit of the comparative example and the common mode signal suppression circuit shown in FIG.
[0067]
The circuit of the comparative example includes a pair of terminals 1a and 1b, another pair of terminals 2a and 2b, a first inductance element having one end connected to the terminal 1a and the other end connected to the terminal 2a, and one end connected to the terminal 2a. A second inductance element connected to the terminal 1b and the other end connected to the terminal 2b. In FIG. 8, a line indicated by reference numeral 31 represents the characteristics of the circuit of the comparative example when the inductances of the first and second inductance elements are both set to 33 μH. The line indicated by reference numeral 32 in FIG. 8 represents the characteristics of the circuit of the comparative example when the inductances of the first and second inductance elements are both 90 μH.
[0068]
In FIG. 8, each of the lines indicated by reference numerals 33 to 38 represents the characteristic of the common mode signal suppression circuit shown in FIG. In the simulation, the capacitances of the capacitors 151 and 152 are both set to 1000 pF, the inductances of the first winding 11, the second winding 12 and the third winding 13 are all set to 30 μH, and the windings 11 and 12 are connected to the windings. The coupling coefficient with the line 13 was set to 0.995. Note that the value of 0.995 is a value that can be realized as a coupling coefficient.
[0069]
In the simulation, the source of the common mode signal is located near the first and second positions A and B, and the source of the common mode signal is located near the third and fourth positions C and D. There was no difference between the cases and the characteristics of the common mode signal suppression circuit.
[0070]
The line indicated by the reference numeral 33 represents the characteristic when the inductances of the windings 161 and 162 are both set to 0. The configuration of the common mode signal suppression circuit shown in FIG. 6 in this case is the same as that of the common mode signal suppression circuit shown in FIG. The line indicated by reference numeral 34 represents the characteristics when the inductances of the windings 161 and 162 are both set to 0.3 μH. The line indicated by reference numeral 35 indicates the characteristics when the inductances of the windings 161 and 162 are both set to 3 μH. The line indicated by reference numeral 36 represents the characteristics when the inductance of the windings 161 and 162 is 30 μH. The line indicated by reference numeral 37 represents the characteristics when the inductance of the windings 161 and 162 is set to 60 μH. The line indicated by reference numeral 38 represents the characteristics when the inductance of the windings 161 and 162 is 600 μH.
[0071]
Hereinafter, the result of the simulation shown in FIG. 8 will be considered. First, comparing the lines indicated by reference numerals 31, 32, and 35 reveals the following. The common mode signal suppression circuit in which the inductance of the first winding 11 is 30 μH, the inductance of the fourth winding 161 is 3 μH, and the sum of these is 33 μH is smaller than the circuit of the comparative example in which the inductance of the inductance element is 33 μH. Also, in the frequency range of about 1 MHz or more, the effect of suppressing the common mode signal is large. Further, this common mode signal suppression circuit has a greater effect of suppressing the common mode signal in a frequency range of about 3 MHz or more than the circuit of the comparative example in which the inductance of the inductance element is 90 μH. From this, according to the present embodiment, the inductance element can be reduced in size as compared with the comparative example, and as a result, the circuit itself can be reduced in size.
[0072]
Also, comparing the line indicated by the reference numeral 31 with the line indicated by the reference numeral 33, the effect of suppressing the common mode signal is suppressed even when the inductance of the windings 161 and 162 is 0, that is, even when the impedance element 16 is not provided. Obtainable.
[0073]
However, as can be seen by comparing the lines indicated by reference numerals 33 to 38, the effect of suppressing the common mode signal is greater when the impedance element 16 is provided than when the impedance element 16 is not provided. Moreover, as the inductance of the windings 161 and 162 increases, the effect of suppressing the common mode signal increases. However, as the inductance of the windings 161 and 162 increases, the shape of the impedance element 16 increases. Therefore, if the inductance of the windings 161 and 162 exceeds 600 μH, the practicality is reduced. When the inductance of the windings 11 to 13 is 30 μH, it is understood that a sufficient common mode signal suppressing effect can be obtained if the inductance of the windings 161 and 162 is 30 μH or 60 μH. From these facts, it is considered that the inductance of the windings 161 and 162 is sufficient if it is 30 μH or 60 μH. Further, it is considered that the inductance of the windings 161 and 162 is preferably substantially equal to the inductance of the windings 11 to 13.
[0074]
Considering from FIG. 8, the inductance of the windings 161 and 162 is preferably 0.3 μH or more and 600 μH or less, more preferably 3 μH or more and 60 μH or less, and further preferably 3 μH or more and 30 μH or less. preferable.
[0075]
Next, with reference to FIG. 9, a result of examining the relationship between the coupling coefficient between the windings 11 and 12 and the winding 13 and the common mode signal suppressing effect in the common mode signal suppressing circuit illustrated in FIG. 6 by simulation. explain. FIG. 9 shows gain frequency characteristics obtained by simulation for each of the circuit of the comparative example and the common mode signal suppression circuit shown in FIG.
[0076]
Lines indicated by reference numerals 41 and 42 in FIG. 9 represent the characteristics of the circuit of the comparative example under the same conditions as those of the lines indicated by reference numerals 31 and 32 in FIG.
[0077]
In FIG. 9, each line indicated by reference numerals 43 to 46 represents the characteristic of the common mode signal suppressing circuit shown in FIG. In the simulation, the capacitance of the capacitors 151 and 152 was set to 1000 pF, and the inductances of the windings 11, 12, 13, 161, and 162 were all set to 30 μH. Lines denoted by reference numerals 43 to 46 represent characteristics when the coupling coefficients between the windings 11 and 12 and the winding 13 are 0.7, 0.9, 0.995, and 1, respectively.
[0078]
Hereinafter, the result of the simulation shown in FIG. 9 will be considered. First, if the coupling coefficient is 0.7 or more in the common mode signal suppression circuit, a greater common mode signal suppression effect can be obtained than in the circuit of the comparative example. As the coupling coefficient increases, the effect of suppressing the common mode signal increases. Considering from FIG. 9, the coupling coefficient is preferably 0.7 or more, more preferably 0.9 or more, and even more preferably 0.995 or more.
[0079]
As described above, according to the common mode signal suppression circuit according to the present embodiment, the common mode signal can be more effectively reduced over a wider frequency range than the common mode signal suppression circuit according to the first embodiment. Can be suppressed.
[0080]
Other configurations, operations, and effects of the present embodiment are the same as those of the first embodiment.
[0081]
Note that the present invention is not limited to the above embodiments, and various modifications are possible. For example, the anti-phase signal transmission circuit 15 is not limited to a high-pass filter, and may be a band-pass filter.
[0082]
【The invention's effect】
As described above, according to the present invention, it is possible to effectively suppress a common mode signal in a wide frequency range and to realize a common mode signal suppression circuit that can be downsized.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a basic configuration of a common mode signal suppression circuit according to a first embodiment of the present invention.
FIG. 2 is a circuit diagram showing an example of a specific configuration of the common mode signal suppression circuit shown in FIG.
FIG. 3 is a circuit diagram for explaining a principle of suppressing a common mode signal by the common mode signal suppressing circuit according to the first embodiment of the present invention.
FIG. 4 is a circuit diagram for explaining an operation of the common mode signal suppression circuit according to the first embodiment of the present invention.
FIG. 5 is a circuit diagram showing a basic configuration of a common mode signal suppression circuit according to a second embodiment of the present invention.
FIG. 6 is a circuit diagram showing an example of a specific configuration of the common mode signal suppression circuit shown in FIG.
FIG. 7 is a circuit diagram for explaining an operation of a common mode signal suppression circuit according to a second embodiment of the present invention.
8 is a characteristic diagram showing frequency characteristics of gains obtained by simulation for each of the circuit of the comparative example and the common mode signal suppression circuit shown in FIG. 6;
9 is a characteristic diagram illustrating frequency characteristics of gains obtained by simulation for each of the circuit of the comparative example and the common mode signal suppression circuit illustrated in FIG. 6;
FIG. 10 is a circuit diagram illustrating an example of a configuration of an LC filter.
[Explanation of symbols]
3, 4: conductive wire, 11: first winding, 12: second winding, 13: third winding, 15: reverse-phase signal transmission circuit, 15A: high-pass filter, 16: impedance element, 151 , 152... Capacitor, 161... Fourth winding, 162.

Claims (7)

A common mode signal suppression circuit that suppresses a common mode signal that propagates in two conductive lines at the same phase,
A first winding inserted into one of the conductive wires at a predetermined first position;
A second position corresponding to the first position is inserted into the other conductive line and coupled to the first winding and cooperates with the first winding to suppress the common mode signal. A second winding;
A third winding coupled to the first winding and the second winding so that mutual inductance occurs between the first winding and the second winding;
Connected to the third winding, connected to the one conductive wire at a third position different from the first position, and further corresponding to the third position, the second position And a negative-phase signal transmitting means for transmitting a negative-phase signal for suppressing the common mode signal, which is connected to the other conductive line at a fourth position different from the
The source of the common mode signal is higher than the first and second positions except for a position between a first position and a third position and a position between a second position and a fourth position. When the position is close to the third and fourth positions, the anti-phase signal transmitting means detects a common mode signal and outputs the anti-phase signal having an anti-phase to the detected common mode signal. Supplying to the third winding, the third winding injects the opposite-phase signal into the two conductive lines via the first winding and the second winding;
The source of the common mode signal is higher than the third and fourth positions except for a position between the first position and the third position and a position between the second position and the fourth position. The third winding detects a common mode signal when the position is close to the first and second positions, and the anti-phase signal transmission means detects the common mode signal detected by the third winding. A common mode signal suppressing circuit, wherein the opposite phase signal having a phase opposite to a signal is injected into the two conductive lines. Further, in the two conductive wires, the peak value of the common mode signal which is provided at a position between the first position and the third position and at a position between the second position and the fourth position is provided. 2. The common mode signal suppression circuit according to claim 1, further comprising an impedance element for reducing the impedance. 3. The common mode signal suppression circuit according to claim 1, wherein the negative-phase signal transmission unit has a high-pass filter for passing a common mode signal. 4. The circuit according to claim 3, wherein the high-pass filter includes a capacitor. The impedance element is connected to a fourth winding inserted into one conductive line and the fourth winding inserted into the other conductive line and cooperates with the fourth winding. The common mode signal suppressing circuit according to claim 1, further comprising a fifth winding that suppresses the common mode signal. 6. The common mode signal suppression circuit according to claim 5, wherein each of the inductances of the fourth winding and the fifth winding is 0.3 μH or more. The common mode signal suppression according to any one of claims 1 to 6, wherein a coupling coefficient between the first and second windings and the third winding is 0.7 or more. circuit.

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