JP2005117218A - Noise suppressing circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a noise suppressing circuit capable of suppressing noise over a wide frequency range while reducing the size. <P>SOLUTION: The noise suppressing circuit comprises a pair of terminals 1a and 1b, another pair of terminals 2a and 2b, a conductive wire 3 connecting the terminals 1a and 2a, and a conductive wire 4 connecting the terminals 1b and 2b. The noise suppressing circuit is also provided with a winding 11 inserted into the conductive wire 3. The noise suppressing circuit further comprises a series circuit 15 of an inductor 13 and a capacitor 14 having one end connected with the middle point of the winding 11 and the other end connected with the conductive wire 4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a noise suppression 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.

  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. The LC filter includes a T-type filter and a π-type filter in addition to one having one inductance element and one capacitor. A general noise filter for electromagnetic interference (EMI) countermeasures 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.

  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. The LC filter is also used as means for reducing such noise on the power line or preventing a communication signal on the indoor power line from leaking to the outdoor power line.

  Noise propagating through two conductive lines includes normal 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.

  Patent Document 1 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 transport power supplied from the AC power source to the load. Two input ends of the filter circuit are connected to both ends of the AC power source, and two output ends 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 this noise component is supplied to the primary winding of the transformer, whereby the power supply voltage is applied on the conductive line in which the secondary winding of the transformer is inserted. The noise component is subtracted from. This line filter reduces noise in the normal mode.

  Patent Document 2 describes a low-pass filter composed of three impedance elements. 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.

  Patent Document 3 describes a normal mode noise filter circuit for reducing normal mode noise and a common mode noise filter circuit for reducing common mode noise. The normal mode noise filter circuit is composed of two coils inserted in two conductive wires and a capacitor connecting the middle windings of the coils. The common mode noise filter circuit is composed of two coils inserted into two conductive wires, and two capacitors provided between the windings of each coil and the ground.

JP-A-9-102723 Japanese Patent Laid-Open No. 5-121988 (FIG. 1) Japanese Patent No. 2784833 (FIG. 6)

  Since the conventional LC filter has a specific resonance frequency determined by inductance and capacitance, there is a problem that a desired attenuation can be obtained only in a narrow frequency range.

  In addition, the filter inserted into the power transporting conductive wire is required to obtain desired characteristics in a state where a current for power transporting flows and to take measures against temperature rise. Therefore, a ferrite magnetic core with a gap is usually used as a magnetic core in an inductance element in a filter for a power conversion circuit. However, such an inductance element has a problem that the characteristic of the inductance element approaches that of an air-core inductance element, so that the inductance element is increased in size in order to realize a desired characteristic.

  Moreover, in the line filter described in Patent Document 1, if the impedance of the filter circuit is 0 and the coupling coefficient of the transformer is 1, theoretically, the noise component can be completely removed. 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 constituted by a capacitor, a series resonance circuit is constituted 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. For these reasons, the actually configured line filter has a problem that noise components cannot be effectively removed in a wide frequency range.

  Further, the low-pass filter described in Patent Document 2 and the filter circuit described in Patent Document 3 have the same problems as the conventional LC filter because the principle of noise reduction is the same as that of the conventional LC filter. Have.

  By the way, in each country, various regulations are often provided for noise emitted from an electronic device to the outside via an AC power supply line, that is, a noise terminal voltage. For example, in the standard of CISPR (International Radio Interference Special Committee), the standard of the noise terminal voltage is set in the frequency range of 150 kHz to 30 MHz. When noise is reduced in such a wide frequency range, the following problems occur particularly with respect to noise reduction in a low frequency range of 1 MHz or less. That is, in the low frequency range of 1 MHz or less, the absolute value of the coil impedance is represented by 2πfL, where L is the inductance of the coil and f is the frequency. Therefore, in general, in order to reduce noise in a low frequency range of 1 MHz or less, a filter including a coil having a large inductance is required. As a result, the filter becomes large.

  The present invention has been made in view of such problems, and an object thereof is to provide a noise suppression circuit that can suppress noise in a wide frequency range and can be reduced in size.

The first noise suppression circuit of the present invention is a circuit that suppresses normal mode noise that is transmitted by the first and second conductive lines and causes a potential difference between the conductive lines.
A winding inserted into the first conductive wire;
It comprises an inductor and a capacitor connected in series, and includes a series circuit having one end connected in the middle of the winding and the other end connected to the second conductive line.

  Here, in the winding, the part from the position where the series circuit is connected to one end is called the first part, and the part from the position where the series circuit is connected to the other end is the second part. Call it. In the series circuit, an end connected to the winding is referred to as a first end, and an end connected to the second conductive line is referred to as a second end. In the first noise suppression circuit of the present invention, when a normal mode voltage is applied between one end of the winding and the second end of the series circuit, this voltage is in series with the first portion. And a predetermined voltage is generated between both ends of the first portion and both ends of the series circuit. Since the first portion and the second portion are electromagnetically coupled, a predetermined voltage is generated between both ends of the second portion in accordance with the voltage generated between both ends of the first portion. As a result, the voltage between the other end of the winding and the second end of the series circuit is the voltage applied between the one end of the winding and the second end of the series circuit. Smaller than. Further, in the first noise suppression circuit of the present invention, when a normal mode voltage is applied between the other end of the winding and the second end of the series circuit, the same as described above. Thus, the voltage between one end of the winding and the second end of the series circuit is greater than the voltage applied between the other end of the winding and the second end of the series circuit. Becomes smaller. As examples of the first conductive line and the second conductive line, there are each conductive line in a single-phase two-wire power line, and a single-phase three-wire power line that is currently widely used for power supply. There are two of the three lines.

  In the first noise suppression circuit of the present invention, one end of the series circuit may be connected to the midpoint of the winding.

The second noise suppression circuit of the present invention is a circuit that suppresses normal mode noise that is transmitted by the first and second conductive lines and causes a potential difference between the conductive lines.
A first winding inserted into the first conductive wire;
A second winding inserted into the second conductive line;
It comprises an inductor and a capacitor connected in series, and includes a series circuit having one end connected in the middle of the first winding and the other end connected in the middle of the second winding.

  Here, in the first winding, the part from the position where the series circuit is connected to one end is called the first part, and the part from the position where the series circuit is connected to the other end is the first part. Called part 2. In the second winding, the portion from the position where the series circuit is connected to one end is called the third portion, and the portion from the position where the series circuit is connected to the other end is the fourth portion. Called the part. In the series circuit, an end connected to the first winding is referred to as a first end, and an end connected to the second winding is referred to as a second end. In the second noise suppression circuit of the present invention, when a normal mode voltage is applied between one end of the first winding and one end of the second winding, this voltage is The voltage is divided by the first part, the series circuit, and the third part, and a predetermined voltage is generated between both ends of the first part, both ends of the series circuit, and both ends of the third part. Since the first portion and the second portion are electromagnetically coupled, a predetermined voltage is generated between both ends of the second portion in accordance with the voltage generated between both ends of the first portion. Similarly, since the third part and the fourth part are electromagnetically coupled, a predetermined voltage is generated between both ends of the fourth part according to the voltage generated between both ends of the third part. To do. As a result, the voltage between the other end of the first winding and the other end of the second winding is equal to one end of the first winding and one of the second winding. It becomes smaller than the voltage applied between the ends. In the second noise suppression circuit of the present invention, the normal mode voltage is also applied between the other end of the first winding and the other end of the second winding. In the same manner as described above, the voltage between one end of the first winding and one end of the second winding is the same as that of the other end of the first winding and the second winding. It is less than the voltage applied between the other end of the line.

  In the second noise suppression circuit of the present invention, one end of the series circuit may be connected to the midpoint of the first winding, and the other end of the series circuit may be connected to the midpoint of the second winding.

The third noise suppression circuit of the present invention is a circuit for suppressing common mode noise propagating in the same phase through the first and second conductive lines,
A first winding inserted into the first conductive wire;
A second winding inserted into the second conductive line and coupled to the first winding to cooperate with the first winding to suppress common mode noise;
A first series circuit comprising an inductor and a capacitor connected in series, one end connected to the middle of the first winding and the other end grounded;
It comprises an inductor and a capacitor connected in series, and a second series circuit having one end connected in the middle of the second winding and the other end grounded.

  Here, in the first winding, the part from the position where the first series circuit is connected to one end is called the first part, and the other end from the position where the first series circuit is connected The part up to the part is called the second part. In the second winding, the portion from the position where the second series circuit is connected to one end is called the third portion, and the other end from the position where the second series circuit is connected The part up to is called the fourth part. In the first series circuit, an end connected to the first winding is referred to as a first end, and an end that is grounded is referred to as a second end. In the second series circuit, an end connected to the second winding is referred to as a third end, and an end connected to the ground is referred to as a fourth end. In the third noise suppression circuit of the present invention, when a common mode voltage is applied to one end of the first winding and one end of the second winding, one of the first windings An equal voltage is generated between one end of the second winding and ground and between one end of the second winding and ground. A voltage generated between one end of the first winding and the ground is divided by the first portion and the first series circuit, and is divided between both ends of the first portion and both ends of the first series circuit. A predetermined voltage is generated between them. Similarly, the voltage generated between one end of the second winding and the ground is divided by the third portion and the second series circuit, so that the voltage between both ends of the third portion and the second series is divided. A predetermined voltage is generated between both ends of the circuit. Since the first portion and the second portion are electromagnetically coupled, a predetermined voltage is generated between both ends of the second portion in accordance with the voltage generated between both ends of the first portion. Similarly, since the third part and the fourth part are electromagnetically coupled, a predetermined voltage is generated between both ends of the fourth part according to the voltage generated between both ends of the third part. To do. As a result, the common mode voltage generated at the other end of the first winding and the other end of the second winding is the same as that of the one end of the first winding and the second winding. It becomes smaller than the common mode voltage applied to one end. Further, in the third noise suppression circuit of the present invention, when a common mode voltage is applied to the other end of the first winding and the other end of the second winding, Similarly, the common mode voltage generated at one end of the first winding and one end of the second winding is equal to the other end of the first winding and the second winding. It becomes smaller than the common mode voltage applied to the other end.

  In the third noise suppression circuit of the present invention, one end of the first series circuit is connected to the midpoint of the first winding, and one end of the second series circuit is connected to the midpoint of the second winding. It may be.

  In the third noise suppression circuit of the present invention, of the inductors and capacitors of the first series circuit, the capacitor is disposed closer to the first winding, and among the inductors and capacitors of the second series circuit. The capacitor may be disposed closer to the second winding, and the inductor of the first series circuit and the inductor of the second series circuit may be common.

  According to the noise suppression circuit of the present invention, noise can be suppressed over a wide frequency range, and the noise suppression circuit can be reduced in size.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[First Embodiment]
First, the noise suppression circuit according to the first embodiment of the present invention will be described. The noise suppression circuit according to the present embodiment is a circuit that suppresses normal mode noise that is transmitted through two conductive lines and causes a potential difference between the conductive lines. FIG. 1 is a circuit diagram showing a configuration of a noise suppression circuit according to the present embodiment. This noise suppression circuit 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 conductive line 4 connecting the terminals 1b and 2b. I have. The noise suppression circuit further includes a winding 11 inserted into the conductive wire 3. The winding 11 is wound around the magnetic core 12. The noise suppression circuit further includes a series circuit 15 including an inductor 13 and a capacitor 14 connected in series, one end connected in the middle of the winding 11 and the other end connected to the conductive wire 4. The inductor 13 has a winding 13a wound around a magnetic core 13b. The capacitor 14 functions as a high-pass filter that passes a normal mode signal having a frequency equal to or higher than a predetermined value. In FIG. 1, among the inductor 13 and the capacitor 14, the inductor 13 is disposed at a position closer to the winding 11. However, the positional relationship between the inductor 13 and the capacitor 14 may be opposite to the relationship shown in FIG. One end of the series circuit 15 is preferably connected to the midpoint of the winding 11.

  Next, the operation of the noise suppression circuit according to the present embodiment will be described with reference to FIG. First, in the winding 11, a portion from a position where the series circuit 15 is connected to one end connected to the terminal 1 a is referred to as a first portion 11 a, and from the position where the series circuit 15 is connected to the terminal 2 a. A portion up to the other end to be connected is referred to as a second portion 11b. In the series circuit 15, the end connected to the winding 11 is called a first end, and the end connected to the conductive wire 4 is called a second end.

  First, as shown in FIG. 2, a case where a normal mode voltage Vi is applied between the terminals 1a and 1b will be described. In this case, the voltage Vi is applied between one end of the winding 11 and the second end of the series circuit 15. This voltage Vi is divided by the first portion 11 a and the series circuit 15, and predetermined voltages are generated between both ends of the first portion 11 a and both ends of the series circuit 15. Since the first portion 11a and the second portion 11b are electromagnetically coupled, a predetermined voltage is generated between both ends of the second portion 11b in accordance with the voltage generated between both ends of the first portion 11a. Occur. As a result, the voltage between the other end of the winding 11 and the second end of the series circuit 15, that is, the voltage Vo between the terminals 2a and 2b is greater than the voltage Vi applied between the terminals 1a and 1b. Becomes smaller.

  In the present embodiment, even when a normal mode voltage is applied between the terminals 2a and 2b, the voltage between the terminals 1a and 1b is applied between the terminals 2a and 2b in the same manner as described above. It becomes smaller than the voltage. As described above, according to the noise suppression circuit according to the present embodiment, the normal mode noise is applied to the terminals 1a and 1b and the normal mode noise is applied to the terminals 2a and 2b. Also, normal mode noise can be suppressed.

  Next, the operation of the noise suppression circuit when one end of the series circuit 15 is connected to the middle point of the winding 11 will be described. Here, to make the explanation easier to understand, it is assumed that the coupling coefficient between the first portion 11a and the second portion 11b is 1, and the impedance of the capacitor 14 is zero. Further, it is assumed that the inductances of the first portion 11a, the second portion 11b, and the inductor 13 are equal. In this case, as shown in FIG. 2, when the normal mode voltage Vi is applied between the terminals 1a and 1b, the voltage Vi is divided by the first portion 11a and the inductor 13, and the first A voltage of 1/2 Vi is generated between both ends of the portion 11 a and between both ends of the inductor 13. Note that the arrow in FIG. 2 indicates that the tip is higher in potential. In response to the voltage 1 / 2Vi generated across the first portion 11a, the voltage 1 / 2Vi is also generated across the second portion 11b. As a result, the voltage Vo between the terminals 2a and 2b is theoretically zero because the voltage 1 / 2Vi between both ends of the second portion 11b and the voltage 1 / 2Vi between both ends of the inductor 13 cancel each other. Become. In addition, when the normal mode voltage Vi is applied between the terminals 2a and 2b, the voltage between the terminals 1a and 1b becomes zero in principle as in the above description.

  Here, consider the case where the inductances of the first portion 11a, the second portion 11b, and the inductor 13 are equal as described above. This can be realized by equalizing the windings of the first portion 11a, the second portion 11b, and the winding 13a of the inductor 13. In this case, since the inductance of the winding is proportional to the square of the number of turns, the inductance of the winding 11 is four times the inductance of the inductor 13. In other words, the inductance of the inductor 13 is ¼ of the inductance of the winding 11. As described above, according to the present embodiment, the inductor 13 may have a small inductance.

  Next, the effect of the noise suppression circuit according to the present embodiment will be specifically shown by the following simulation results. In this simulation, the following numerical values were used. The inductance of the winding 11 was 4 mH, and all the inductances of the first part 11a, the second part 11b, and the inductor 13 were 1 mH. The capacitance of the capacitor 14 was 4700 pF.

  FIG. 3 is a characteristic diagram showing the frequency characteristic of the attenuation amount of normal mode noise in the noise suppression circuit obtained by simulation. In FIG. 3, the horizontal axis represents frequency and the vertical axis represents gain. The smaller the gain, that is, the larger the absolute value of the negative gain, the greater the amount of noise attenuation. In FIG. 3, the line indicated by reference numeral 20 represents the frequency characteristic of the attenuation amount of normal mode noise in the noise suppression circuit.

  From FIG. 3, according to the noise suppression circuit according to the present embodiment, it is possible to obtain a high attenuation characteristic with respect to normal mode noise over a wide frequency range of 150 kHz to 30 MHz including a low frequency range of 150 kHz to 1 MHz. I understand.

  As can be seen from FIG. 3, according to the noise suppression circuit according to the present embodiment, the amount of noise attenuation is large in a low frequency range of 1 MHz or less where normal mode noise is a problem. Therefore, according to the present embodiment, it is possible to effectively suppress normal mode noise in a low frequency range of 1 MHz or less.

  In addition, according to the present embodiment, a coil having a large inductance and a simple configuration in which a series circuit 15 including an inductor 13 and a capacitor 14 is added to the winding 11 inserted into the conductive wire 3 is used. Therefore, a noise suppression circuit having the above characteristics can be realized. Therefore, according to the present embodiment, it is possible to reduce the size of the noise suppression circuit.

  As described above, the noise suppression circuit according to the present embodiment can effectively suppress normal mode noise in a wide frequency range including a low frequency range of 1 MHz or less with a relatively simple configuration. In addition, the noise suppression circuit can be reduced in size.

[Second Embodiment]
FIG. 4 is a circuit diagram showing a configuration of a noise suppression circuit according to the second embodiment of the present invention. The noise suppression circuit according to the present embodiment connects a pair of terminals 1a and 1b, another pair of terminals 2a and 2b, a conductive wire 3 connecting the terminals 1a and 2a, and the terminals 1b and 2b. And a conductive wire 4. The noise suppression circuit further includes a winding 11 inserted into the conductive wire 3 and a winding 21 inserted into the conductive wire 4. The winding 11 is wound around the magnetic core 12, and the winding 21 is wound around the magnetic core 22. The noise suppression circuit further includes a series circuit 15 including an inductor 13 and a capacitor 14 connected in series, one end connected in the middle of the winding 11 and the other end connected in the middle of the winding 21. . The inductor 13 has a winding 13a wound around a magnetic core 13b. The capacitor 14 functions as a high-pass filter that passes a normal mode signal having a frequency equal to or higher than a predetermined value. In FIG. 4, among the inductor 13 and the capacitor 14, the inductor 13 is disposed at a position closer to the winding 11. However, the positional relationship between the inductor 13 and the capacitor 14 may be opposite to the relationship shown in FIG. One end of the series circuit 15 is preferably connected to the midpoint of the winding 11, and the other end of the series circuit 15 is preferably connected to the midpoint of the winding 21.

  Next, the operation of the noise suppression circuit according to the present embodiment will be described. First, in the winding 11, a portion from a position where the series circuit 15 is connected to one end connected to the terminal 1 a is referred to as a first portion 11 a, and from the position where the series circuit 15 is connected to the terminal 2 a. A portion up to the other end to be connected is referred to as a second portion 11b. Further, in the winding 21, the portion from the position where the series circuit 15 is connected to one end connected to the terminal 1b is referred to as a third portion 21a, and from the position where the series circuit 15 is connected to the terminal 2b. A portion up to the other end to be connected is referred to as a fourth portion 21b. In the series circuit 15, the end connected to the winding 11 is called a first end, and the end connected to the winding 21 is called a second end.

  First, a case where the normal mode voltage Vi is applied between the terminals 1a and 1b will be described. In this case, the voltage Vi is applied between one end of the winding 11 and one end of the winding 21. This voltage Vi is divided by the first portion 11a, the series circuit 15 and the third portion 21a, and is divided between both ends of the first portion 11a, between both ends of the series circuit 15 and between both ends of the third portion 21a. A predetermined voltage is generated for each. Since the first portion 11a and the second portion 11b are electromagnetically coupled, a predetermined voltage is generated between both ends of the second portion 11b in accordance with the voltage generated between both ends of the first portion 11a. Occur. Similarly, since the third portion 21a and the fourth portion 21b are electromagnetically coupled, a predetermined value is generated between both ends of the fourth portion 21b according to the voltage generated between both ends of the third portion 21a. Is generated. As a result, the voltage between the other end of the winding 11 and the other end of the winding 21, that is, the voltage Vo between the terminals 2a and 2b is higher than the voltage Vi applied between the terminals 1a and 1b. Get smaller.

  In the present embodiment, even when a normal mode voltage is applied between the terminals 2a and 2b, the voltage between the terminals 1a and 1b is applied between the terminals 2a and 2b in the same manner as described above. It becomes smaller than the voltage. As described above, according to the noise suppression circuit according to the present embodiment, the normal mode noise is applied to the terminals 1a and 1b and the normal mode noise is applied to the terminals 2a and 2b. Also, normal mode noise can be suppressed.

  Next, the operation of the noise suppression circuit when one end of the series circuit 15 is connected to the midpoint of the winding 11 and the other end of the series circuit 15 is connected to the midpoint of the winding 21 will be described. Here, in order to make the explanation easier to understand, the coupling coefficient between the first part 11a and the second part 11b is 1, and the coupling coefficient between the third part 21a and the fourth part 21b is also 1. Assume that the impedance of capacitor 14 is zero. Further, it is assumed that the inductances of the first portion 11a, the second portion 11b, the third portion 21a, and the fourth portion 21b are equal to each other and are ½ of the inductance of the inductor 13.

  In this case, when a normal mode voltage Vi is applied between the terminals 1a and 1b, the voltage Vi is divided by the first portion 11a, the series circuit 15 and the third portion 21a, and the first portion 11a is divided. A voltage of 1/4 Vi is generated between both ends of the third portion 21 a and the both ends of the third portion 21 a, and a voltage of 1/2 Vi is generated between both ends of the series circuit 15. Note that the arrow in FIG. 4 indicates that the potential ahead is higher. In response to the voltage 1 / 4Vi generated across the first portion 11a, the voltage 1 / 4Vi is also generated across the second portion 11b. Similarly, according to the voltage 1 / 4Vi generated between both ends of the third portion 21a, the voltage 1 / 4Vi is also generated between both ends of the fourth portion 21b. As a result, the voltage Vo between the terminals 2a and 2b is equal to the voltage 1 / 4Vi between both ends of the second portion 11b, the voltage 1 / 4Vi between both ends of the fourth portion 21b, and the voltage between both ends of the inductor 13. By canceling 1 / 2Vi, in principle it becomes zero. In addition, when the normal mode voltage Vi is applied between the terminals 2a and 2b, the voltage between the terminals 1a and 1b becomes zero in principle as in the above description.

  The noise suppression circuit according to the present embodiment is configured so that the impedance characteristics of the conductive wires 3 and 4 are balanced. Therefore, according to this noise suppression circuit, it is possible to suppress an increase in the radiation electric field intensity from the conductive wires 3 and 4 and suppress the generation of radiation noise. Other configurations, operations, and effects in the present embodiment are the same as those in the first embodiment.

[Third Embodiment]
Next, a noise suppression circuit according to a third embodiment of the present invention will be described. The noise suppression circuit according to the present embodiment is a circuit that suppresses common mode noise that propagates through two conductive wires in the same phase. FIG. 5 is a circuit diagram showing a configuration of the noise suppression circuit according to the present embodiment. The noise suppression circuit 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, a conductive line 4 connecting the terminals 1b and 2b, A ground terminal 5 and a ground line 6 connected to the ground terminal 5 are provided.

  The noise suppression circuit further includes a winding 31 inserted into the conductive wire 3 and a winding 32 inserted into the conductive wire 4. The winding 31 and the winding 32 are wound around the magnetic core 33 and are coupled to each other so as to suppress common mode noise in cooperation. That is, the windings 31 and 32 are arranged in such a direction that the magnetic fluxes induced in the magnetic core 33 by the currents flowing through the windings 31 and 32 when the currents in the normal mode flow through them cancel each other. It is wound around. As described above, the windings 31 and 32 and the magnetic core 33 constitute a common mode choke coil that suppresses common mode noise and allows a normal mode signal to pass.

  The noise suppression circuit further includes a capacitor 35 having one end connected in the middle of the winding 31, a capacitor 36 having one end connected in the middle of the winding 32, and one end connected to the other ends of the capacitors 35 and 36. The other end of the inductor 37 is connected to the ground line 6. The inductor 37 has a winding 37a wound around a magnetic core 37b.

  The capacitor 35 and the inductor 37 connected in series constitute a first series circuit having one end connected in the middle of the winding 31 and the other end grounded. The capacitor 36 and the inductor 37 connected in series constitute a second series circuit having one end connected in the middle of the winding 32 and the other end grounded. As described above, in the present embodiment, among the inductor 37 and the capacitor 35 of the first series circuit, the capacitor 35 is disposed closer to the winding 31, and the inductor 37 and the capacitor 36 of the second series circuit. Among them, the capacitor 36 is arranged at a position closer to the winding 32, and the inductor 37 of the first series circuit and the inductor 37 of the second series circuit are common.

  However, the inductor of the first series circuit and the inductor of the second series circuit may be provided separately without being shared. In this case, in each series circuit, the positional relationship between the inductor and the capacitor may be opposite to the relationship shown in FIG.

  Next, the operation of the noise suppression circuit according to the present embodiment will be described. First, in the winding 31, the part from the position where the first series circuit is connected to one end connected to the terminal 1a is referred to as the first part 31a, and the position where the first series circuit is connected. To the other end connected to the terminal 2a is referred to as a second portion 31b. Further, in the winding 32, a portion from a position where the second series circuit is connected to one end connected to the terminal 1b is referred to as a third portion 32a, and a position where the second series circuit is connected. To the other end connected to the terminal 2b is referred to as a fourth portion 32b. In the first series circuit, the end connected to the winding 31 is called a first end, and the end connected to the ground is called a second end. In the second series circuit, an end connected to the winding 32 is referred to as a third end, and an end that is grounded is referred to as a fourth end.

  First, the case where the common mode voltage Vi is applied to the terminals 1a and 1b will be described. In this case, an equal voltage Vi is generated between one end of the winding 31 and the ground and between one end of the winding 32 and the ground. The voltage Vi generated between one end of the winding 31 and the ground is divided by the first portion 31a and the first series circuit, and the voltage Vi between the both ends of the first portion 31a and the first series circuit is divided. A predetermined voltage is generated between both ends. Similarly, the voltage Vi generated between one end of the winding 32 and the ground is divided by the third portion 32a and the second series circuit, and between the both ends of the third portion 32a and the second portion. A predetermined voltage is generated between both ends of the series circuit. Since the first portion 31a and the second portion 31b are electromagnetically coupled, a predetermined voltage is generated between both ends of the second portion 31b in accordance with the voltage generated between both ends of the first portion 31a. Occur. As a result, a voltage between the other end of the winding 31 and the ground, that is, a voltage Vo between the terminal 2a and the ground is a voltage generated between one end of the winding 31 and the ground, that is, between the terminal 1a and the ground. It becomes smaller than the voltage Vi generated at. Similarly, since the third portion 32a and the fourth portion 32b are electromagnetically coupled to each other, a predetermined value is generated between both ends of the fourth portion 32b according to the voltage generated between both ends of the third portion 32a. Is generated. As a result, a voltage Vo between the other end of the winding 32 and the ground, that is, a voltage Vo between the terminal 2b and the ground is a voltage generated between one end of the winding 32 and the ground, that is, between the terminal 1b and the ground. It becomes smaller than the voltage Vi generated at. Thus, when a common mode voltage is applied to the terminals 1a and 1b, the common mode voltage generated at the terminals 2a and 2b is smaller than the common mode voltage applied to the terminals 1a and 1b. Become.

  In the present embodiment, when a common mode voltage is applied to the terminals 2a and 2b, the common mode voltage generated at the terminals 1a and 1b is applied to the terminals 2a and 2b in the same manner as described above. It becomes smaller than the applied common mode voltage. As described above, according to the noise suppression circuit according to the present embodiment, the common mode noise is applied to the terminals 1a and 1b and the common mode noise is applied to the terminals 2a and 2b. In addition, common mode noise can be suppressed.

  Next, the operation of the noise suppression circuit particularly when one end of the first series circuit is connected to the midpoint of the winding 31 and one end of the second series circuit is connected to the midpoint of the winding 32. explain. Here, in order to make the explanation easier to understand, the coupling coefficient between the first part 31a and the second part 31b is 1, and the coupling coefficient between the third part 32a and the fourth part 32b is 1. Assume that the impedances of the capacitors 35 and 36 are zero. In addition, it is assumed that the inductances of the first portion 31a, the second portion 31b, the third portion 32a, the fourth portion 32b, and the inductor 37 are equal.

  In this case, when a common mode voltage Vi is applied to the terminals 1a and 1b, an equal voltage Vi is generated between one end of the winding 31 and the ground and between one end of the winding 32 and the ground. The voltage Vi generated between one end of the winding 31 and the ground is divided by the first portion 31a and the inductor 37, and 1 / between both ends of the first portion 31a and both ends of the inductor 37, respectively. A voltage of 2 Vi is generated. Similarly, the voltage Vi generated between one end of the winding 32 and the ground is divided by the third portion 32 a and the inductor 37, and between the both ends of the third portion 32 a and the both ends of the inductor 37. A voltage of 1/2 Vi is generated in each case. Note that the arrow in FIG. 5 indicates that the potential ahead is higher. In response to the voltage 1 / 2Vi generated across the first portion 31a, the voltage 1 / 2Vi is also generated across the second portion 31b. As a result, the voltage Vo between the terminal 2a and the ground is zero in principle because the voltage 1 / 2Vi between both ends of the second portion 31b and the voltage 1 / 2Vi between both ends of the inductor 37 cancel each other. Become. Similarly, a voltage 1 / 2Vi is generated between both ends of the fourth portion 32b in response to a voltage 1 / 2Vi generated between both ends of the third portion 32a. As a result, the voltage Vo between the terminal 2b and the ground is zero in principle because the voltage 1 / 2Vi between both ends of the fourth portion 32b and the voltage 1 / 2Vi between both ends of the inductor 37 cancel each other. Become. In this way, the common mode voltage generated at the terminals 2a and 2b is theoretically zero. Also, when the common mode voltage Vi is applied to the terminals 2a and 2b, the common mode voltage generated at the terminals 1a and 1b is zero in principle as in the above description.

  The characteristics of the noise suppression circuit according to the present embodiment are the same as those of the noise suppression circuit according to the first embodiment except for the difference between the normal mode and the common mode. Therefore, according to the noise suppression circuit according to the present embodiment, the common mode choke coil is simply configured by adding two series circuits composed of an inductor and a capacitor, and without using a coil having a large inductance. Common mode noise can be effectively suppressed in a wide frequency range. Further, according to the present embodiment, it is possible to reduce the size of the noise suppression circuit.

  Note that the noise suppression circuit according to each embodiment includes means for reducing ripple voltage and noise generated by the power conversion circuit, noise on the power line in power line communication, and communication signals on the indoor power line are connected 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 noise suppression circuit of the present invention may include the normal mode noise suppression circuit according to the first or second embodiment and the common mode noise suppression circuit according to the third embodiment. Good.

It is a circuit diagram which shows the structure of the noise suppression circuit which concerns on the 1st Embodiment of this invention. It is a circuit diagram for demonstrating the effect | action of the noise suppression circuit which concerns on the 1st Embodiment of this invention. It is a characteristic view which shows an example of the characteristic of the noise suppression circuit which concerns on the 1st Embodiment of this invention. It is a circuit diagram which shows the structure of the noise suppression circuit which concerns on the 2nd Embodiment of this invention. It is a circuit diagram which shows the structure of the noise suppression circuit which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

3, 4 ... conductive wire, 11 ... winding, 11a ... first part, 11b ... second part, 13 ... inductor, 14 ... capacitor, 15 ... series circuit.

Claims (7)

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,
A winding inserted into the first conductive wire;
A noise suppression circuit comprising: a series circuit including an inductor and a capacitor connected in series, one end connected in the middle of the winding, and the other end connected to the second conductive wire.   The noise suppression circuit according to claim 1, wherein one end of the series circuit is connected to a midpoint of the winding. 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,
A first winding inserted into the first conductive line;
A second winding inserted into the second conductive line;
A series circuit including an inductor and a capacitor connected in series, one end connected to the middle of the first winding and the other end connected to the middle of the second winding; Noise suppression circuit.   The one end of the series circuit is connected to the midpoint of the first winding, and the other end of the series circuit is connected to the midpoint of the second winding. Noise suppression circuit. A circuit for suppressing common mode noise propagating in the same phase through the first and second conductive lines,
A first winding inserted into the first conductive line;
A second winding inserted into the second conductive line and coupled to the first winding to suppress common mode noise in cooperation with the first winding;
A first series circuit comprising an inductor and a capacitor connected in series, one end connected to the middle of the first winding and the other end grounded;
A noise suppression circuit comprising: a second series circuit including an inductor and a capacitor connected in series, one end connected in the middle of the second winding and the other end grounded.   One end of the first series circuit is connected to the midpoint of the first winding, and one end of the second series circuit is connected to the midpoint of the second winding. The noise suppression circuit according to claim 5. Of the inductor and capacitor of the first series circuit, the capacitor is disposed closer to the first winding, and of the inductor and capacitor of the second series circuit, the capacitor is the second. 7. The noise suppression circuit according to claim 5, wherein the inductor of the first series circuit is common to the inductor of the second series circuit.

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