JP2004080437A - Normal-mode signal suppressing circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a normal-mode signal suppressing circuit capable of efficiently suppressing normal mode signals over a wide frequency range, and of being miniaturized. <P>SOLUTION: The normal-mode signal suppressing circuit is provided with a first inductance element 11 inserted into a conductive wire 3 at a first position A, and a second inductance element 12 connected to the element 11 via a magnetic core 13. The normal-mode signal suppressing circuit is also provided with a negative-phase signal transmission circuit 15, when the circuit is connected to the element 12 at second position B in the conductive wire 3; and an impedance element 16 provided between the positions A and B in the conductive wire 3 and for reducing a peak value of a passing signal. The circuit 15 detects a normal mode signal on the conductive wire 3, and supplies an inverted signal, having a phase inverse of the normal signal with respect to the element 12. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a normal mode signal suppression circuit for suppressing a normal mode signal transmitted by a conductive line.
[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]
FIG. 8 shows an example of the configuration of the LC filter. This LC filter includes a pair of terminals 101a and 101b, another pair of terminals 102a and 102b, a coil 103 as an inductance element, and a capacitor 104. The terminal 102b is connected to the terminal 101b. One end of the coil 103 is connected to the terminal 101a, and the other end is connected to the terminal 102a. One end of the capacitor 104 is connected to the other end of the coil 103 and the terminal 102a. The other end of the capacitor 104 is connected to terminals 101b and 102b.
[0006]
The LC filter shown in FIG. 8 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.
[0007]
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. The LC filter shown in FIG. 8 is for reducing normal mode noise.
[0008]
Further, Japanese Patent Application Laid-Open No. 9-102723 describes a line filter using a transformer. This line filter includes a transformer and a filter circuit. The secondary winding of the transformer is inserted into one of the two conductive wires that carry the power supplied to the load from the AC power supply. Two inputs of the filter circuit are connected to both ends of the AC power supply, and two outputs of the filter circuit are connected to both ends of the primary winding of the transformer. In this line filter, a noise component is extracted from a power supply voltage by a filter circuit, and the noise component is supplied to a primary winding of the transformer. From which the noise component is subtracted. This line filter reduces normal mode noise.
[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]
On the other hand, in the line filter described in Japanese Patent Application Laid-Open No. 9-102723, if the impedance of the filter circuit is 0 and the coupling coefficient of the transformer is 1, the noise component can be theoretically completely removed. Can be. However, in practice, the impedance of the filter circuit does not become zero, and further changes according to the frequency. In particular, when a filter circuit is formed by a capacitor, a series resonance circuit is formed by the capacitor and the primary winding of the transformer. Therefore, the impedance of the signal path including the capacitor and the primary winding of the transformer is reduced only in a narrow frequency range near the resonance frequency of the series resonance circuit. As a result, this line filter can remove noise components only in a narrow frequency range. Also, the coupling coefficient of the transformer is actually smaller than one. Therefore, the noise component supplied to the primary winding of the transformer is not completely subtracted from the power supply voltage. For these reasons, there is a problem that the noise component cannot be effectively removed in a wide frequency range with the actually configured line filter.
[0012]
The present invention has been made in view of such a problem, and an object of the present invention is to provide a normal mode signal suppressing circuit which can effectively suppress a normal mode signal in a wide frequency range and can be downsized.
[0013]
[Means for Solving the Problems]
The normal mode signal suppression circuit of the present invention is a circuit that suppresses a normal mode signal transmitted by two conductive lines and causing a potential difference between the two conductive lines,
A first inductance element inserted into one of the conductive lines at a predetermined first position;
A second inductance element coupled to the first inductance element so that mutual inductance is generated between the first inductance element and the second inductance element;
Anti-phase signal transmission means connected to the second inductance element and connected to one of the conductive wires at a second position different from the first position, for transmitting an anti-phase signal for suppressing a normal mode signal When,
One of the conductive lines includes an impedance element provided between the first position and the second position, the impedance element reducing a peak value of a passing normal mode signal.
[0014]
In the normal mode signal suppressing circuit of the present invention, the source of the normal mode signal is located closer to the second position than the first position except for a position between the first position and the second position. In this case, the anti-phase signal transmission means detects the normal mode signal, and supplies an anti-phase signal having an anti-phase to the detected normal mode signal to the second inductance element. , A negative-phase signal is injected into one conductive line via the first inductance element. Thereby, in one conductive line, the normal mode signal is suppressed from the first position in the forward direction of the normal mode signal.
[0015]
In the normal mode signal suppressing circuit according to the present invention, the source of the normal mode signal is located at a position closer to the first position than the second position except for a position between the first position and the second position. The second inductance element detects a normal mode signal, and the anti-phase signal transmission means outputs one anti-phase signal having an anti-phase to the normal mode signal detected by the second inductance element. Is injected into the conductive wire. Thereby, in one conductive line, the normal mode signal is suppressed in the forward direction of the normal mode signal from the second position.
[0016]
In the normal mode signal suppressing circuit of the present invention, the peak value of the passing normal mode signal is reduced by the impedance element. Thereby, the difference between the peak value of the normal mode signal propagating through the impedance element and the peak value of the negative phase signal injected into one conductive line via the negative phase signal transmission means is reduced.
[0017]
In the normal mode signal suppressing circuit according to the present invention, the anti-phase signal transmitting means may include a high-pass filter for passing the normal mode signal. This high-pass filter may include a capacitor. Further, the high-pass filter may include a plurality of combined capacitors.
[0018]
In the normal mode signal suppressing circuit according to the present invention, the impedance element may include a third inductance element inserted into one of the conductive lines. The inductance of the third inductance element may be 0.3 μH or more.
[0019]
In the normal mode signal suppression circuit according to the present invention, a coupling coefficient between the first inductance element and the second inductance element may be 0.7 or more.
[0020]
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 normal mode signal suppression circuit according to the first embodiment of the present invention. The normal 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 normal 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 normal 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 normal mode signal to be suppressed by the normal mode signal suppression circuit is connected to the terminals 1a and 1b or the terminals 2a and 2b. Therefore, the normal mode signal to be suppressed is input to the normal mode signal suppression circuit from the terminals 1a and 1b or the terminals 2a and 2b.
[0021]
Here, the normal mode signal is a signal transmitted by two power conductive lines and causing a potential difference between the two power conductive lines. Normal mode signals to be suppressed include noise and unnecessary communication signals.
[0022]
The normal mode signal suppressing circuit further causes mutual inductance to be generated between the first inductance element 11 inserted into the conductive line 3 and the first inductance element 11 at the predetermined first position A. And a second inductance element 12 coupled to the first inductance element 11 via a magnetic core 13. Each of the inductance elements 11 and 12 has a winding, and the turns ratio of these windings is, for example, 1: 1.
[0023]
The normal mode signal suppressing circuit is further connected to the second inductance element 12 and connected to the conductive line 3 at a position B different from the first position A, and configured to control the reverse phase signal for suppressing the normal mode signal. Is transmitted. One end of the negative-phase signal transmission circuit 15 is connected to the conductive line 3 at the position B. The other end of the anti-phase signal transmission circuit 15 is connected to one end of the second inductance element 12. The other end of the second inductance element 12 is connected to the conductive line 4. The reverse phase signal transmission circuit 15 corresponds to the reverse phase signal transmission means of the present invention.
[0024]
The normal mode signal suppression circuit further includes an impedance element 16 provided between the first position A and the second position B on the conductive line 3 to reduce the peak value of the normal mode signal passing therethrough. ing.
[0025]
FIG. 2 is a circuit diagram showing an example of a specific configuration of the normal 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 the normal mode signal and the negative-phase signal. The high-pass filter 15A includes a capacitor 15a. One end of the capacitor 15a is connected to the conductive line 3 at a position B. The other end of the capacitor 15a is connected to one end of the second inductance element 12.
[0026]
Further, in the example shown in FIG. 2, the impedance element 16 is constituted by a third inductance element 16A. One end of the third inductance element 16A is connected to the terminal 1a, and the other end is connected to one end of the first inductance element 11.
[0027]
Next, the operation of the normal mode signal suppression circuit according to the present embodiment will be described. First, the normal mode in which the source of the normal mode signal is located closer to the second position B than the first position A except for the position between the first position A and the second position B The operation of the signal suppression circuit will be described. In this case, the anti-phase signal transmission circuit 15 detects the normal mode signal on the conductive line 3 at the second position B, and outputs the anti-phase signal having the anti-phase to the detected normal mode signal to the second position B. To the second inductance element 12. The second inductance element 12 injects a negative-phase signal into the conductive line 3 via the first inductance element 11 at the first position A. Thus, the normal mode signal is suppressed in the conductive line 3 from the first position A in the forward direction of the normal mode signal.
[0028]
Next, a normal mode in which the source of the normal mode signal is located closer to the first position A than the second position B, except for the position between the first position A and the second position B, The operation of the mode signal suppression circuit will be described. In this case, the second inductance element 12 detects the normal mode signal on the conductive line 3 at the first position A. At the second position B, the negative-phase signal transmission circuit 15 injects the conductive line 3 with a negative-phase signal having a reverse phase to the normal mode signal detected by the second inductance element 12. Accordingly, the normal mode signal is suppressed in the conductive line 3 from the second position B in the forward direction of the normal mode signal.
[0029]
In the present embodiment, the peak value of the signal passing therethrough is reduced by the impedance element 16. Thereby, the difference between the peak value of the normal mode signal propagating through the impedance element 16 and the peak value of the negative phase signal injected into the conductive line 3 via the negative phase signal transmission circuit 15 is reduced. .
[0030]
Next, with reference to FIG. 3, a principle of suppressing a normal mode signal by the normal mode signal suppressing circuit according to the present embodiment will be described. Here, a case where the source of the normal mode signal is located closer to the second position B than to the first position A will be described. FIG. 3 shows a configuration excluding the third inductance element 16A from the configuration shown in FIG. In the following description, the impedance of the high-pass filter 15A (capacitor 15a) is 0, the winding ratio of the first inductance element 11 to the second inductance element 12 is, for example, 1: 1 and the first inductance element 11 and the second inductance element 12 are 1: 1. It is assumed that the coupling coefficient between the inductance element 11 and the second inductance element 12 is 1.
[0031]
Here, in the circuit shown in FIG. 3, a case where a normal mode signal causing a potential difference Vin between the terminals 1a and 1b is input to the terminals 1a and 1b will be considered. When the frequency of the normal mode signal is within the pass band of the high-pass filter 15A, the normal 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 capacitor 15a. As a result, a potential difference -Vin occurs between both ends of the second inductance element 12. In accordance with the potential difference -Vin generated between both ends of the second inductance element 12, a potential difference -Vin is also generated between both ends of the first inductance element 11. Assuming that the potential difference between the terminals 2a and 2b is Vo, this is represented by the following equation.
[0032]
Vo = Vin + (− Vin) = 0
[0033]
Thus, according to the circuit shown in FIG. 3, if the impedance of the high-pass filter 15A is 0 and the coupling coefficient between the first inductance element 11 and the second inductance element 12 is 1, the high-pass filter 15A , The normal mode signal can be completely removed regardless of the frequency.
[0034]
However, actually, the impedance of the high-pass filter 15A does not become 0, and further changes according to the frequency. In particular, when the high-pass filter 15A is configured by the capacitor 15a, a series resonance circuit is configured by the capacitor 15a and the second inductance element 12. Therefore, the impedance of the signal path including the capacitor 15a and the second inductance element 12 decreases only in a narrow frequency range near the resonance frequency of the series resonance circuit. As a result, the circuit shown in FIG. 3 can reduce the normal mode signal only in a narrow frequency range.
[0035]
The coupling coefficient between the first inductance element 11 and the second inductance element 12 is actually smaller than 1. Therefore, a voltage having the same value as the voltage supplied to the second inductance element 12 is not generated in the first inductance element 11.
[0036]
For these reasons, it is difficult for the circuit shown in FIG. 3 to effectively suppress the normal mode signal in a wide frequency range.
[0037]
In the normal mode signal suppressing circuit according to the present embodiment, an impedance element 16 for reducing the peak value of the passing normal mode signal is provided between the first position A and the second position B in the conductive line 3. ing. Thereby, in the normal mode signal suppressing circuit, the peak value of the normal mode signal propagating through the impedance element 16 and the peak value of the negative phase signal injected into the conductive line 3 via the negative phase signal transmission circuit 15 Is reduced. As a result, according to the normal mode signal suppressing circuit, it is possible to effectively suppress the normal mode signal in a wide frequency range.
[0038]
Hereinafter, the operation of the normal mode signal suppression circuit according to the present embodiment will be described in detail with reference to FIG. FIG. 4 is a circuit diagram showing a circuit in which a normal mode signal generation source 21 and a load 22 are connected to the normal mode signal suppression circuit shown in FIG. The normal mode signal generation source 21 is connected between the terminals 1a and 1b, and generates a potential difference Vin between the terminals 1a and 1b. The load 22 is connected between the terminals 2a and 2b and has an impedance Zo.
[0039]
In the circuit shown in FIG. 4, the inductance of the second inductance element 12 is L11, the inductance of the first inductance element 11 is L12, the capacitance of the capacitor 15a is C1, and the inductance of the third inductance element 16A is L21. And The current passing through the capacitor 15a and the second inductance element 12 is represented by i1, and the total impedance of the path of the current i1 is represented by Z1. The current passing through the third inductance element 16A and the first inductance element 11 is denoted by i2, and the total impedance of the path of the current i2 is denoted by Z2.
[0040]
The mutual inductance between the first inductance element 11 and the second inductance element 12 is M, and the coupling coefficient between them is K. The coupling coefficient K is represented by the following equation (1).
[0041]
K = M / √ (L11 · L12) (1)
[0042]
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 normal mode signal.
[0043]
Z1 = j (ωL11-1 / ωC1) (2)
Z2 = Zo + jω (L12 + L21) (3)
[0044]
The potential difference Vin is represented by the following equations (4) and (5).
[0045]
Vin = Z1 · i1 + jωM · i2 (4)
Vin = Z2 · i2 + jωM · i1 (5)
[0046]
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).
[0047]
i1 = (Vin−jωM · i2) / Z1 (6)
[0048]
Next, when the equation (6) is substituted into the equation (5), the following equation (7) is obtained.
[0049]
i2 = Vin (Z1-jωM) / (Z1 · Z2 + ω ² ・ M ² …… (7)
[0050]
Suppressing the normal mode signal by the normal mode signal suppression circuit shown in FIG. 4 can be said to reduce the current i2 represented by Expression (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.
[0051]
First, since Z1 is represented by equation (2), Z1 increases as the inductance L11 of the second inductance element 12 increases, and Z1 increases as the capacitance C1 of the capacitor 15a increases.
[0052]
Next, since Z2 is represented by the equation (3), it becomes larger as the sum of the inductance L12 of the first inductance element 11 and the inductance L21 of the third inductance element 16A is larger. 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 normal mode signal can be suppressed only by the first inductance element 11, but the normal mode signal can be further suppressed by adding the third inductance element 16A.
[0053]
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, when the coupling coefficient K is increased, the effect of suppressing the normal mode signal by the normal mode signal suppressing 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 normal mode signal greatly changes depending on the value of the coupling coefficient K.
[0054]
When the source of the normal mode signal is located closer to the first position A than the second position B, the roles of the second inductance element 12 and the negative-phase signal transmission circuit 15 are as shown in FIG. And the description with reference to FIG. However, in this case as well, the above description applies equally.
[0055]
Next, with reference to FIG. 5, a description will be given of a result of a simulation of a relationship between the inductance of the third inductance element 16A and the normal mode signal suppressing effect in the normal mode signal suppressing circuit illustrated in FIG. FIG. 5 shows the frequency characteristics of the gain obtained by simulation for each of the circuit of the comparative example and the normal mode signal suppression circuit shown in FIG.
[0056]
The circuit of the comparative example includes a pair of terminals 1a and 1b, another pair of terminals 2a and 2b, and an inductance element having one end connected to the terminal 1a and the other end connected to the terminal 2a. . In FIG. 5, a line denoted by reference numeral 31 represents the characteristic of the circuit of the comparative example when the inductance of the inductance element is set to 33 μH. The line indicated by reference numeral 32 in FIG. 5 represents the characteristics of the circuit of the comparative example when the inductance of the inductance element is 90 μH.
[0057]
In FIG. 5, the lines denoted by reference numerals 33 to 38 represent the characteristics of the normal mode signal suppression circuit shown in FIG. In the simulation, the capacitance of the capacitor 15a was set to 0.01 μF, the inductance of the first inductance element 11 and the inductance of the second inductance element 12 were both set to 30 μH, and the inductance of the first inductance element 11 and the second inductance element 12 was changed. The coupling coefficient was 0.995. Note that the value of 0.995 is a value that can be realized as a coupling coefficient.
[0058]
In the simulation, the normal mode signal suppression circuit is different between a case where the source of the normal mode signal is located near the first position A and a case where the source of the normal mode signal is located near the second position B. There was no difference in properties.
[0059]
The line indicated by the reference numeral 33 represents the characteristic when the inductance of the third inductance element 16A is set to 0. In this case, the configuration of the normal mode signal suppression circuit shown in FIG. 2 is the same as that of the circuit shown in FIG. The line indicated by reference numeral 34 represents the characteristic when the inductance of the third inductance element 16A is 0.3 μH. The line indicated by the reference numeral 35 represents the characteristics when the inductance of the third inductance element 16A is 3 μH. The line indicated by reference numeral 36 indicates the characteristics when the inductance of the third inductance element 16A is 30 μH. The line indicated by the reference numeral 37 represents the characteristics when the inductance of the third inductance element 16A is set to 60 μH. The line indicated by reference numeral 38 indicates the characteristics when the inductance of the third inductance element 16A is set to 600 μH.
[0060]
Hereinafter, the result of the simulation shown in FIG. 5 will be considered. First, when the line indicated by reference numeral 32 and the line indicated by reference numeral 35 are compared, the following can be understood. The normal mode signal suppression circuit in which the inductance of the first inductance element 11 is 30 μH, the inductance of the third inductance element 16A is 3 μH, and the sum of these is 33 μH is a circuit of a comparative example in which the inductance of the inductance element is 90 μH. In the frequency range of 1 MHz or more, the effect of suppressing the normal mode signal is greater. 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.
[0061]
Comparing the lines indicated by reference numerals 33 to 38, the effect of suppressing the normal mode signal increases as the inductance of the third inductance element 16A increases. However, as the inductance of the third inductance element 16A increases, the shape of the third inductance element 16A increases. Therefore, if the inductance of the third inductance element 16A exceeds 600 μH, the practicality is reduced. When the inductance of the first inductance element 11 is 30 μH, if the inductance of the third inductance element 16A is 30 μH or 60 μH, a sufficient effect of suppressing a normal mode signal can be obtained. From these facts, it is considered that 30 μH or 60 μH is sufficient for the inductance of the third inductance element 16A. Further, it is considered that the inductance of the third inductance element 16A is preferably substantially equal to the inductance of the first inductance element 11.
[0062]
Further, as can be seen by comparing the line indicated by reference numeral 31 with the line indicated by reference numeral 34, even if the inductance of the third inductance element 16A is about 0.3 μH, the effect of suppressing the normal mode signal can be obtained. it can.
[0063]
Considering from FIG. 5, the inductance of the third inductance element 16A is preferably 0.3 μH or more and 600 μH or less, more preferably 3 μH or more and 60 μH or less, and more preferably 3 μH or more and 30 μH or less. More preferred.
[0064]
Next, referring to FIG. 6, the relationship between the coupling coefficient between the first inductance element 11 and the second inductance element 12 and the normal mode signal suppression effect in the normal mode signal suppression circuit shown in FIG. The result of the examination will be described. FIG. 6 shows the frequency characteristics of the gain obtained by simulation for each of the circuit of the comparative example and the normal mode signal suppression circuit shown in FIG.
[0065]
The lines indicated by reference numerals 41 and 42 in FIG. 6 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.
[0066]
In FIG. 6, each line denoted by reference numerals 43 to 46 represents the characteristic of the normal mode signal suppression circuit shown in FIG. In the simulation, the capacitance of the capacitor 15a was 0.01 μF, and the inductances of the first inductance element 11, the second inductance element 12, and the third inductance element 16A were all 30 μH. Lines denoted by reference numerals 43 to 46 represent characteristics when the coupling coefficient between the first inductance element 11 and the second inductance element 12 is 0.7, 0.9, 0.995, and 1, respectively. ing.
[0067]
Hereinafter, the result of the simulation shown in FIG. 6 will be considered. First, in the normal mode signal suppression circuit, if the coupling coefficient is 0.7 or more, a larger normal mode signal suppression effect than the circuit of the comparative example can be obtained. As the coupling coefficient increases, the effect of suppressing the normal mode signal increases. Considering from FIG. 6, the coupling coefficient is preferably 0.7 or more, more preferably 0.9 or more, and even more preferably 0.995 or more.
[0068]
As described above, according to the present embodiment, it is possible to realize a normal mode signal suppression circuit that can effectively suppress normal mode signals in a wide frequency range and that can be downsized.
[0069]
Further, according to the present embodiment, it is possible to realize a normal mode signal suppression circuit having a large effect of suppressing a normal mode signal while having a reduced number of components and being inexpensive as compared with a conventional EMI filter.
[0070]
Further, in the present embodiment, when the anti-phase signal transmission circuit 15 is configured using the capacitor 15a, the detection of the normal mode signal and the anti-phase And the generation of an inverted-phase signal. Therefore, in this case, the number of parts can be further reduced.
[0071]
Note that the normal mode signal suppression circuit according to the present embodiment includes means for reducing ripple voltage and noise generated by the power conversion circuit, noise on power lines in power line communication, and communication signals on indoor power lines. It can be used as a means for preventing leakage to the outdoor power line.
[0072]
[Second embodiment]
FIG. 7 is a circuit diagram showing a configuration of a normal mode signal suppression circuit according to the second embodiment of the present invention. The basic configuration of the normal mode signal suppression circuit according to this embodiment is the same as that of the first embodiment. This embodiment is different from the first embodiment in that a high-pass filter 15A as the anti-phase signal transmission circuit 15 includes a plurality of combined capacitors 151, 152,. Note that the number of capacitors included in the high-pass filter 15A may be two or more.
[0073]
Each end of each of the plurality of capacitors 151, 152,... Is connected to the conductive line 3 at the second position B, and the other end is connected to one end of the second inductance element 12. Are connected in parallel with each other. The capacitances of the capacitors 151, 152,... Are different from each other. According to the high-pass filter 15A including such a plurality of capacitors 151, 152,..., It is possible to design the frequency characteristics of the high-pass filter 15A to have desired characteristics. For example, according to the high-pass filter 15A of the present embodiment, it is possible to design the frequency characteristics of the high-pass filter 15A such that the pass band is wider than that of the high-pass filter 15A of the first embodiment.
[0074]
Other configurations, operations, and effects of the present embodiment are the same as those of the first embodiment.
[0075]
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.
[0076]
【The invention's effect】
As described above, according to the present invention, it is possible to effectively suppress a normal mode signal in a wide frequency range and achieve a normal 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 normal 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 a normal mode signal suppression circuit shown in FIG.
FIG. 3 is a circuit diagram showing a configuration excluding a third inductance element from the configuration shown in FIG. 2;
FIG. 4 is a circuit diagram showing a circuit in which a normal mode signal generation source and a load are connected to the normal mode signal suppression circuit shown in FIG. 2;
FIG. 5 is a characteristic diagram showing frequency characteristics of gains obtained by simulation for each of the circuit of the comparative example and the normal mode signal suppression circuit shown in FIG. 2;
6 is a characteristic diagram showing frequency characteristics of gains obtained by simulation for each of the circuit of the comparative example and the normal mode signal suppression circuit shown in FIG. 2;
FIG. 7 is a circuit diagram showing a configuration of a normal mode signal suppression circuit according to a second embodiment of the present invention.
FIG. 8 is a circuit diagram illustrating an example of a configuration of an LC filter.
[Explanation of symbols]
3, 4: conductive wire, 11: first inductance element, 12: second inductance element, 15: negative-phase signal transmission circuit, 15A: high-pass filter, 15a: capacitor, 16: impedance element, 16A: third Inductance element.

Claims (7)

A normal mode signal suppression circuit that suppresses a normal mode signal transmitted by two conductive lines and causing a potential difference between the two conductive lines,
A first inductance element inserted into the one conductive line at a predetermined first position;
A second inductance element coupled to the first inductance element so that mutual inductance occurs between the first inductance element and the first inductance element;
An opposite terminal connected to the second inductance element and connected to the one conductive line at a second position different from the first position to transmit an opposite-phase signal for suppressing the normal mode signal. Phase signal transmission means;
In the one conductive line, provided between the first position and the second position, an impedance element for reducing the peak value of the passing normal mode signal,
When the source of the normal mode signal is located at a position closer to the second position than the first position except for a position between the first position and the second position, the reverse phase signal transmission is performed. The means detects a normal mode signal, and supplies the anti-phase signal having a phase opposite to the detected normal mode signal to the second inductance element, wherein the second inductance element is configured to detect the normal mode signal. Injecting the opposite-phase signal into the one conductive line via an inductance element,
When the source of the normal mode signal is located closer to the first position than the second position except for a position between the first position and the second position, the second inductance The element detects a normal mode signal, and the opposite-phase signal transmission means injects the opposite-phase signal, which is in opposite phase to the normal mode signal detected by the second inductance element, into the one conductive line. A normal mode signal suppression circuit, characterized in that: 2. The normal mode signal suppression circuit according to claim 1, wherein said anti-phase signal transmission means includes a high-pass filter for passing a normal mode signal. 3. The circuit according to claim 2, wherein the high-pass filter includes a capacitor. 3. The circuit according to claim 2, wherein the high-pass filter includes a plurality of combined capacitors. 5. The normal mode signal suppression circuit according to claim 1, wherein said impedance element has a third inductance element inserted into said one conductive line. 6. The normal mode signal suppression circuit according to claim 5, wherein the inductance of the third inductance element is 0.3 [mu] H or more. 7. The normal mode signal suppression circuit according to claim 1, wherein a coupling coefficient between the first inductance element and the second inductance element is 0.7 or more.

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