JP2012109292A - Common mode noise filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a common mode noise filter capable of removing noise generated by differential signals.SOLUTION: In this common mode noise filter, the other end 11b of a first coil conductor 11 is connected to the other end 12b of a second coil conductor 12, and the other end 13b of a third coil conductor 13 is connected to the other end 14b of a fourth coil conductor 14. Common mode noise flows from a first external electrode 15 and a fourth external electrode 18, and flows from a second external electrode 16 and a third external electrode 17. Furthermore, against the common mode noise, the first coil conductor 11 is magnetically coupled with the third coil conductor 13, and the second coil conductor 12 is magnetically coupled with the fourth coil conductor 14.

Description

  The present invention relates to a common mode noise filter used in various electronic devices such as digital devices, AV devices, and information communication terminals.

  As shown in FIG. 6, this type of conventional common mode noise filter includes nonmagnetic layers 1a to 1c and a plurality of magnetic layers 2 formed above and below the nonmagnetic layers 1a to 1c. A laminated body 3 formed by laminating magnetic layers 1a to 1c and a magnetic layer 2, and spiral first coils 4 and second coils 5 formed on the nonmagnetic layers 1a to 1c; And the winding direction of the first coil 4 and the winding direction of the second coil 5 are the same in top view.

  As prior art document information relating to the invention of this application, for example, Patent Document 1 is known.

JP 2001-60514 A

  In the above-described conventional common mode noise filter, the common mode noise can be removed by the impedance generated by the first coil 4 and the second coil 5 when the common mode noise is passed. Since the differential signal cancels out between the first coil 4 and the second coil 5, the noise component (normal mode noise) of the differential signal cannot be removed.

  The present invention solves the above-described conventional problems, and an object of the present invention is to provide a common mode noise filter capable of removing normal mode noise.

  In order to achieve the above object, the present invention has the following configuration.

  According to the first aspect of the present invention, the first and second coils, the first and second external electrodes connected to both ends of the first coil, and both ends of the second coil are provided. And third and fourth external electrodes connected to each other, and common mode current flows in from the first external electrode and the fourth external electrode, and flows out from the second external electrode and the third external electrode In addition, the first coil and the second coil are magnetically coupled by a common mode current, and an impedance portion is provided between the second coil and the fourth external electrode. Therefore, according to this configuration, common mode noise can be removed by the first coil and the impedance unit, and the second coil and the impedance unit, and further, differential signals having a phase difference of 180 ° from each other can be obtained. External electrode and When flowing from the fourth external electrode, the signal reaching the second coil to flow impedance section above, together with the high-frequency component of the signal is attenuated by the impedance, it can be removed normal mode noise of the signal. In addition, the high frequency signal in the second coil is out of phase with the other high frequency signal, so that the generated magnetic flux is completely reduced due to the phase shift and amplitude level difference between the first coil and the second coil. Since they do not cancel each other, impedance is generated between the first coil and the second coil. As a result, the high-frequency component of the differential signal is attenuated, so that normal mode noise of the signal can be removed. Further, since the differential signal that has passed through the first coil passes through the impedance portion before reaching the third external electrode, the high-frequency component is attenuated by the impedance, and the high-frequency signal in the second coil is shifted in phase. Occurs. At this time, when the impedance value and the phase of the impedance part connected to the first coil and the impedance part connected to the second coil are equal, the phase difference and amplitude difference generated between the differential signals are corrected, It returns to a normal differential signal and has the effect of removing only the noise component of the differential signal.

  According to a second aspect of the present invention, the first coil and the second coil, first and second external electrodes connected to both ends of the first coil, and both ends of the second coil are provided. And third and fourth external electrodes connected to each other, and common mode current flows in from the first external electrode and the fourth external electrode, and flows out from the second external electrode and the third external electrode And common mode currents flow in opposite directions to the first coil and the second coil, and the first coil and the second coil are positively magnetized by the common mode current. According to this configuration, common mode noise can be removed by the common mode impedance of the first coil and the second coil, and further, the second coil on the second external electrode side of the first coil can be removed. The signal reaching the edge is Since it is after having passed through the first coil first, the phase of the high-frequency signal at the location of the first coil relative to the second coil is shifted, thereby causing the first coil and the second coil to be shifted. Since the magnetic flux generated by the signal is not completely canceled out, an impedance of a differential signal is generated between the first coil and the second coil. As a result, since the high-frequency differential signal is attenuated, the normal mode noise generated by the differential signal can be removed.

  Invention of Claim 3 of this invention is provided in the edge part of the laminated body, the 1st-4th coil conductor formed in this laminated body, and the said laminated body, and said 1st-1st First to fourth external electrodes connected to one end of each of the four coil conductors, connecting the other end of the first coil conductor and the other end of the second coil conductor, And while connecting the other end of the third coil conductor and the other end of the fourth coil conductor, a common mode current flows from the first external electrode and the fourth external electrode, The first coil conductor and the third coil conductor are magnetically coupled to each other by a common mode current, and the second coil conductor and the third coil electrode The fourth coil conductor is magnetically coupled, According to the configuration, common mode noise can be removed by the common mode impedance of the first to fourth coil conductors, and further, differential signals having a phase difference of 180 ° can be obtained from the first external electrode and the fourth coil conductor. Since the signal that reaches the second coil conductor first flows through the first coil conductor when flowing from the external electrode, the high-frequency signal in the second coil conductor is shifted in phase, and thereby the fourth coil Since the conductor and the second coil conductor do not completely cancel the magnetic flux generated by the signal, an impedance of the differential signal is generated between the fourth coil conductor and the second coil conductor. As a result, since the high-frequency differential signal is attenuated, the normal mode noise generated by the differential signal can be removed.

  As described above, the common mode noise filter of the present invention connects the other end of the first coil conductor and the other end of the second coil conductor, and connects the other end of the third coil conductor to the fourth. A common mode current flows from the first external electrode and the fourth external electrode, and flows out from the second external electrode and the third external electrode, and The first coil conductor and the third coil conductor are magnetically coupled by the common mode current, and the second coil conductor and the fourth coil conductor are magnetically coupled. When a differential signal having a phase difference of ° flows from one end of the first coil conductor and one end of the fourth coil conductor, the signal that reaches the second coil conductor is the first coil conductor first. This will cause the second Since the phase of the high-frequency signal in the wire conductor is shifted, the magnetic flux generated by the signal is not completely canceled between the fourth coil conductor and the second coil conductor, so that the fourth coil conductor and the second coil conductor do not cancel each other. An impedance of a differential signal is generated between the coil conductors. As a result, since the high-frequency differential signal is attenuated, the normal mode noise generated in the differential signal can be removed.

The disassembled perspective view of the common mode noise filter in one embodiment of this invention Perspective view of the common mode noise filter Equivalent circuit diagram of the common mode noise filter Equivalent circuit diagram of another example of the common mode noise filter Equivalent circuit diagram of another example of the common mode noise filter Exploded perspective view of a conventional common mode noise filter

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is an exploded perspective view of a common mode noise filter according to an embodiment of the present invention, and FIG. 2 is a perspective view of the common mode noise filter.

  As shown in FIGS. 1 and 2, the common mode noise filter according to one embodiment of the present invention includes a multilayer body 10 and first to fourth coil conductors 11 to 14 formed inside the multilayer body 10. And first to fourth external electrodes 15 to 18 provided at end portions of the multilayer body 10 and connected to one end portions 11a to 14a of the first to fourth coil conductors 11 to 14, respectively. The other end 11b of the first coil conductor 11 and the other end 12b of the second coil conductor 12 are connected, and the other end 13b of the third coil conductor 13 and the fourth coil are connected. The other end portion 14b of the conductor 14 is connected, and a common mode current flows from the first external electrode 15 and the fourth external electrode 18, and the second external electrode 16 and the third external electrode Spill out of the 17 The first coil conductor 11 and the third coil conductor 13 are magnetically coupled by a common mode current, and the second coil conductor 12 and the fourth coil conductor 14 are magnetically coupled. It is.

  The said structure WHEREIN: The said 1st-4th coil conductors 11-14 are each formed by plating electrically conductive materials, such as silver, in a spiral shape. The first and second coil conductors 11 and 12 are both formed on the upper surface of the second insulator layer 21b, and the third and fourth coil conductors 13 and 14 are both the third insulator layer 21c. It is formed on the upper surface.

  Further, one end 11a of the first coil conductor 11 and one end 12a of the second coil conductor 12 are exposed from the end face of the second insulator layer 21b, and the other end 11b of the first coil conductor 11 is exposed. The other end 12b of the second coil conductor 12 is connected via a first connection conductor 22a provided on the first insulator layer 21a.

  At this time, the other end 11b of the first coil conductor 11 and the first connection conductor 22a are connected via the first via electrode 23a formed in the second insulator layer 21b, and the second The other end 12b of the coil conductor 12 and the first connection conductor 22a are connected via a second via electrode 23b formed in the second insulator layer 21b.

  And the one end part 11a of the 1st coil conductor 11 exposed from the end surface of the 2nd insulator layer 21b and the one end part 12a of the 2nd coil conductor 12 are the 1st provided in the edge part of the laminated body 10, respectively. The second external electrodes 15 and 16 are directly connected.

  Furthermore, one end 13 a of the third coil conductor 13 and one end 14 a of the fourth coil conductor 14 are both provided on the upper surface of the third insulator layer 21 c, and one end 13 a of the third coil conductor 13. Is connected to a second connection conductor 22b provided in the fourth insulator layer 21d, and one end portion 14a of the fourth coil conductor 14 is connected to a third connection provided in the fourth insulator layer 21d. The conductor 22c is connected. The other end 13b of the third coil conductor 13 and the other end 14b of the fourth coil conductor 14 are connected to each other on the upper surface of the third insulator layer 21c.

  At this time, the one end portion 13a of the third coil conductor 13 and the second connection conductor 22b are connected via the third via electrode 23c formed in the fourth insulator layer 21d, and the fourth coil The one end portion 14a of the conductor 14 and the third connection conductor 22c are connected via a fourth via electrode 23d formed in the fourth insulator layer 21d.

  The one end portion 13a of the third coil conductor 13 is connected to the third external electrode 17 provided at the end portion of the multilayer body 10 via the second connection conductor 22b, and one end of the fourth coil conductor 14 is connected. The part 14a is connected to the fourth external electrode 18 provided at the end of the multilayer body 10 via the third connection conductor 22c.

  A fifth insulator layer 21e is provided on the upper surfaces of the second and third connection conductors 22b and 22c. These first to fifth insulator layers 21a to 21e are, from below, a first insulator layer 21a, a second insulator layer 21b, a third insulator layer 21c, a fourth insulator layer 21d, The fifth insulator layer 21e is laminated in this order, and the second to fourth insulator layers 21b to 21d are formed in a sheet shape from a nonmagnetic material such as Cu-Zn ferrite, and the first insulator layer 21a and the 5th insulator layer 21e are comprised in the sheet form with magnetic materials, such as Ni-Cu-Zn ferrite. Further, the number of the first to fifth insulator layers 21a to 21e is not limited to the number shown in FIG.

  Further, the first to fourth external electrodes 15 to 18 are formed by printing silver on the end face of the laminate 10, and a nickel plating layer is formed on these surfaces by plating. A low melting point metal plating layer such as tin or solder is formed on the surface of the substrate by plating. The first and fourth external electrodes 15 and 18 are provided on the same surface, and the second and third external electrodes 16 and 17 are provided on the other same surface.

  Further, the first to fourth via electrodes 23a to 23d are drilled with laser at two predetermined locations of the second insulator layer 21b and the fourth insulating layer 21d, and silver is formed in the holes. To form.

  Here, when viewed from above, the first coil conductor 11 and the third coil conductor 13 are arranged at substantially the same position, and the winding direction is also the same direction. Similarly, the second coil conductor 12 and the fourth coil conductor 14 are arranged at substantially the same position in a top view, and the winding direction is also the same direction. With this configuration, common mode noise flows in from the first external electrode 15 and the fourth external electrode 18, and the common mode noise flows out of the second external electrode 16 and the third external electrode 17 in the first mode. The coil conductor 11 and the third coil conductor 13 are magnetically coupled, and the second coil conductor 12 and the fourth coil conductor 14 are magnetically coupled, so that common mode noise can be removed. On the other hand, for the differential signal, the magnetic field generated in the first coil conductor 11 and the magnetic field generated in the third coil conductor 13 cancel each other, and the magnetic field generated in the second coil conductor 12 and the fourth Since the magnetic field generated in the coil conductor 14 cancels out, it normally passes through without being attenuated. However, in the high frequency band, as will be described later, the fourth coil conductor 14 and the second coil conductor 12 do not completely cancel out the magnetic flux generated by the signal, and the fourth coil conductor 14 and the second coil conductor 12 A differential signal impedance is generated between them, and normal mode noise is removed.

  FIG. 3 is an equivalent circuit diagram of the common mode noise filter according to the embodiment of the present invention.

  As is clear from FIG. 3, the common mode noise flowing from the first external electrode 15 flows to the second coil conductor 12 after the first coil conductor 11 and flows from the fourth external electrode 18. The common mode noise flows to the third coil conductor 13 after the fourth coil conductor 14. Therefore, with respect to the second coil conductor 12 and the fourth coil conductor 14 that are magnetically coupled to each other, the signal enters the second coil conductor 12 after flowing through the first coil conductor 11 once. A signal directly enters the coil conductor 14.

  As described above, in the common mode noise filter according to the embodiment of the present invention, the other end 11b of the first coil conductor 11 and the other end 12b of the second coil conductor 12 are connected, and the third The other end 13b of the coil conductor 13 and the other end 14b of the fourth coil conductor 14 are connected, and a common mode current flows from the first external electrode 15 and the fourth external electrode 18, The first coil conductor 11 and the third coil conductor 13 are magnetically coupled to each other by the common mode current, and the second coil conductor 12 and the third outer electrode 17 flow out of the second outer electrode 16 and the third outer electrode 17. Since the fourth coil conductor 14 is magnetically coupled, differential signals having a phase difference of 180 ° from each other are transmitted to the one end portion 11a (first external electrode 15) of the first coil conductor 11 and the first coil conductor 11. When flowing from one end portion 14a (fourth external electrode 18) of the fourth coil conductor 14, the signal that reaches the second coil conductor 12 first passes through the first coil conductor 11 as shown in FIG. This causes a shift in the phase of the high-frequency signal in the second coil conductor 12, and the fourth coil conductor 14 and the second coil conductor 12 do not completely cancel out the magnetic flux generated by the signal. The differential signal impedance is generated between the four coil conductors 14 and the second coil conductor 12. As a result, the high-frequency differential signal is attenuated, so that an effect of removing normal mode noise can be obtained.

That is, since the differential signal has a phase difference of 180 °, the differential signal having the phase difference of 180 ° flows in from the same direction, that is, the first and fourth external electrodes 15 and 18. The magnetic field generated by the second coil conductor 12 and the magnetic field generated by the fourth coil conductor 14 cancel each other, but before the signal flows into the second coil conductor 12, the first coil conductor 11. Will flow into. Then, an L component (inductance component) and an R component (resistance component) are generated in the first coil conductor 11, and when the phase difference between the L component and the R component is Φ, Φ = tan ⁻¹ (ωL / R) (Ω is the phase of the signal, L is the inductance value, and R is the resistance value). At this time, the higher the frequency, the more the phase of the L component shifts. Therefore, the phase difference between the second coil conductor 12 and the fourth coil conductor 14 becomes larger from 180 °. As the frequency becomes higher, the second coil conductor 12 and the fourth coil conductor 14 do not cancel each other out, so that the high-frequency differential signal attenuates. Therefore, high frequency noise generated in the differential signal can be removed, and a signal having a frequency lower than this noise can be passed. At this time, since the frequency of the differential signal is lower than the frequency of the noise, the influence of the differential signal itself is small.

  Furthermore, since the signal that reaches the third coil conductor 13 first flows through the fourth coil conductor 14 and the signal directly enters the first coil conductor 11, the high-frequency signal in the third coil conductor 13 A phase shift occurs, and accordingly, the high-frequency differential signal is also attenuated in the first coil conductor 11 and the third coil conductor 13.

  In the above configuration, an impedance unit 23 having a constant inductance, resistance value, or capacitance value may be used instead of the second coil conductor 12 and the fourth coil conductor 14 (the equivalent circuit shown in FIG. 4 is obtained). ). In this case, if the common mode current flows from the first external electrode 15 and the fourth external electrode 18 and flows out from the second external electrode 16 and the third external electrode 17 as described above, The first coil 21 (first coil conductor 11) and the second coil 22 (third coil conductor 13) are magnetically coupled, and differential signals having a phase difference of 180 ° from each other are transmitted to the first outer electrode 15. And flows from the fourth external electrode 18. At this time, both ends of the first coil 21 are connected to the first and second external electrodes 15 and 16 via the impedance part 23, and both ends of the second coil 22 are connected via the impedance part 23. The third and fourth external electrodes 17 and 18 are connected.

  Since the signal that reaches the second coil 22 first flows through the impedance unit 23, the high-frequency component of the signal is attenuated by the impedance, and the normal mode noise of the signal can be removed. Further, the high-frequency signal in the second coil 22 has a phase shift or amplitude difference with respect to the high-frequency signal in the first coil 21, thereby causing a phase shift or amplitude level between the first coil 21 and the second coil 22. Due to the difference, the generated magnetic fluxes are not completely canceled out, and an impedance is generated between the first coil 21 and the second coil 22. As a result, the high frequency component of the differential signal is attenuated, so that normal mode noise of the signal can be removed.

  Furthermore, common mode noise can be removed by the first coil 21 and the impedance unit 23, and the second coil 22 and the impedance unit 23.

  In FIG. 4, the impedance portion 23 formed between the fourth external electrode 18 and the second coil 22 and the second external electrode 16 and the first coil 21 are formed. If the respective resistance values, inductance values, and capacitance values of the impedance unit 23 are made substantially the same and the impedances are made substantially the same, the phase difference and amplitude difference generated between the differential signals are corrected, and a normal differential signal is obtained. Only the noise component of the differential signal is removed. Further, as the impedance portion 23, a resistor provided by forming a conductive material in a linear shape or a meandering shape on an insulating layer, and a coil provided by forming a conductive material in a spiral shape or a spiral shape on the insulating layer A capacitor provided by forming a plate-like conductor made of a conductive material on a plurality of insulating layers can be used.

  Here, if the two impedance portions 23 are coils and are magnetically coupled to each other, the configuration is the same as that of the common mode noise filter according to the embodiment of the present invention shown in FIGS.

  Further, as shown in FIG. 5, the common mode currents flowing from the first external electrode 15 and the fourth external electrode 18 are caused to flow in opposite directions in the first coil 21 and the second coil 22. Also good. At this time, the first coil 21 and the second coil 22 are positively magnetically coupled by the common mode current, that is, the magnetic flux generated in the first coil 21 and the magnetic flux generated in the second coil 22 are strengthened to each other. To fit. In this case, when differential signals having a phase difference of 180 ° from each other flow, the signal that reaches the end of the first coil 21 on the second external electrode 16 side first passes through the first coil 21. Therefore, the phase of the high-frequency signal at the corresponding portion of the first coil 21 is shifted with respect to the second coil 22, thereby attenuating the high-frequency differential signal as in the above-described configuration. Therefore, normal mode noise generated by the differential signal can be removed.

  In the common mode noise filter described above, the second coil conductor 12 and the fourth coil conductor 14 (impedance portion 23) are respectively connected to the first coil conductor 11 and the third coil conductor 13 (first and second coil conductors). Although formed on the upper surface of the same insulating layer as the second coils 21 and 22), they may be formed on the upper surfaces of separate insulating layers.

  Moreover, although the 1st-4th coil conductors 11-14 (the 1st, 2nd coils 21, 22 and the impedance part 23) were formed in the inside of the laminated body 10, these were comprised with a conducting wire, These conductors may be wound around a magnetic core so as to form an equivalent circuit shown in FIGS. 3 to 5, and each of these conductors is constituted by one coil or a multilayer inductor. It may be arranged on the mounting substrate so as to be an equivalent circuit shown in FIG.

  The common mode noise filter according to the present invention has an effect of removing noise generated by a differential signal, and is used particularly as a noise countermeasure for various electronic devices such as digital devices, AV devices, and information communication terminals. This is useful in common mode noise filters and the like.

DESCRIPTION OF SYMBOLS 10 Laminated body 11 1st coil conductor 11a One end part of 1st coil conductor 11b Other end part of 1st coil conductor 12 2nd coil conductor 12a One end part of 2nd coil conductor 12b The other end portion 13 The third coil conductor 13a One end portion of the third coil conductor 13b The other end portion of the third coil conductor 14 The fourth coil conductor 14a The one end portion of the fourth coil conductor 14b The fourth coil conductor Other end portion 15 First external electrode 16 Second external electrode 17 Third external electrode 18 Fourth external electrode 21 First coil 22 Second coil 23 Impedance portion

Claims (3)

First and second coils, first and second external electrodes connected to both ends of the first coil, and third and fourth externals connected to both ends of the second coil A common mode current flows in from the first external electrode and the fourth external electrode and flows out from the second external electrode and the third external electrode. The first coil and the second coil are magnetically coupled to each other, and are substantially the same between the second coil and the fourth external electrode, and between the first coil and the second external electrode. A common mode noise filter provided with an impedance part having an impedance value. First and second coils, first and second external electrodes connected to both ends of the first coil, and third and fourth externals connected to both ends of the second coil And a common mode current flows in from the first external electrode and the fourth external electrode and flows out from the second external electrode and the third external electrode, and the first coil and the first external electrode A common mode noise filter in which a common mode current flows into the two coils in opposite directions, and the first coil and the second coil are positively magnetically coupled by the common mode current. A laminated body, first to fourth coil conductors formed inside the laminated body, and provided at an end of the laminated body and connected to one end of the first to fourth coil conductors, respectively. First to fourth external electrodes, connecting the other end of the first coil conductor and the other end of the second coil conductor, and the other end of the third coil conductor; The other end of the fourth coil conductor is connected, and a common mode current flows from the first external electrode and the fourth external electrode, and the second external electrode and the third external electrode And the first coil conductor and the third coil conductor are magnetically coupled by the common mode current, and the second coil conductor and the fourth coil conductor are magnetically coupled. Common mode noise filter.

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