JP7049201B2 - Noise filter and manufacturing method of noise filter - Google Patents

Description

The present invention relates to a noise filter provided with a ground conductor.

For example, Non-Patent Document 1 discloses a pseudo-distributed constant type line filter which is a noise filter of this type.

The noise filter of Non-Patent Document 1 includes a toroidal-shaped magnetic core, an insulating case accommodating the magnetic core, two windings (coils) wound around the insulating case, and a ground conductor. A part of the ground conductor is housed in an insulating case together with the magnetic core, and is located between the magnetic core and the coil. The other part of the ground conductor is drawn out of the insulating case to form a ground end. Each of the coils has two ends (first terminal and second terminal). A winding capacitance Cw is generated between the first terminal and the second terminal of the coil, and a grounding capacitance Cg is generated between the coil and the grounding conductor. For example, if the number of turns of the coil is adjusted so that the ratio between the grounding capacitance Cg and the winding capacitance Cw is a value larger than 3.0 and smaller than 4.3, the noise flowing through the coil spreads over a wide band. It attenuates by 40 dB or more. That is, a wide attenuation bandwidth is obtained.

Harada, 4 outsiders, "Broadband of line filter by pseudo-distributed constant type structure", IEICE Technical Report, IEICE Technical Report, April 8, 2016, Vol. 116, No. 4. , P. 23-27

The noise filter of Non-Patent Document 1 is attached to a circuit board at the time of use. When the attenuation bandwidth in which the noise is attenuated by 40 dB or more is actually measured with the noise filter attached to the circuit board, the actually measured value of the attenuation bandwidth is considerably smaller than the theoretical value.

Therefore, an object of the present invention is to provide a noise filter capable of widening the attenuation bandwidth in which noise is attenuated by 40 dB or more according to a theoretical value.

Considering the invention of Non-Patent Document 1, the circuit board to which the noise filter is attached is provided with a first electrode for connecting the first terminal and a second electrode for connecting the second terminal for each of the coils. .. A predetermined capacitance (pattern capacitance Cp) is generated between the first electrode and the second electrode of the circuit board. Therefore, the inventor of the present application has considered adding the pattern capacitance Cp in the invention disclosed in Non-Patent Document 1. Specifically, by setting the ratio between Cp + Cw, which is the combined capacitance of the pattern capacitance Cp and the winding capacitance Cw, and the grounding capacitance Cg to a value larger than 3.0 and smaller than 4.3, noise can be generated. I thought that the attenuation bandwidth could be widened. However, the theoretical value of the attenuation bandwidth based on this consideration was also considerably different from the measured value.

As a result of further research by the inventor of the present application, it has been found that the relationship between the synthetic volume Cp + Cw and Cg should not be regarded as a proportional relationship. More specifically, the combined capacitance Cp + Cw is set to a × Cg + b1 or more and a × Cg + b2 or less for predetermined real numbers a, b1, b2 (a> 0, b1 ≠ 0, and b2 ≠ 0). As a result, it was found that the noise of 10 MHz can be attenuated by about 40 dB, whereby the attenuation bandwidth of the noise can be widened. Based on the above findings, the present invention provides a noise filter manufactured by the following manufacturing method.

The present invention comprises the first method of manufacturing a noise filter.
It is a manufacturing method of a noise filter attached to a circuit board.
The noise filter includes a magnetic core, a ground conductor, and two coils.
Each of the coils has a coil portion wound around the magnetic core and two terminals drawn out from the coil portion.
The ground conductor has a conductor main portion disposed apart from the coil portion and a ground terminal drawn out from the conductor main portion.
The circuit board is provided with four electrodes each connected to the terminal of the coil and a ground electrode connected to the ground terminal of the ground conductor.
The manufacturing method includes an adjustment step and includes an adjustment step.
In the adjustment step, Cp + Cw, which is the combined capacitance of the pattern capacitance Cp between the electrodes of the circuit board and the winding capacitance Cw of the coil, is the relationship between the grounding capacitance Cg between the grounding conductor and the coil. When it is not in the first predetermined range of 0.29 × Cg −3.06 or more and 0.29 × Cg + 2.15 or less, Cp, so that the synthetic capacity Cp + Cw is included in the first predetermined range. A manufacturing method for adjusting at least one of Cw and Cg is provided.

Further, the present invention is a first manufacturing method as a second manufacturing method of a noise filter.
The manufacturing method includes a measurement step and includes a measurement step.
In the measurement step, the pattern capacitance Cp of the circuit board is measured, and the pattern capacitance Cp is measured.
In the adjustment step, when the synthetic capacity Cp + Cw is not in the first predetermined range, a manufacturing method for adjusting at least one of Cw and Cg so that the synthetic capacity Cp + Cw is included in the first predetermined range is used. offer.

Further, the present invention is a first manufacturing method as a third manufacturing method of a noise filter.
In the adjustment step, when the synthetic capacity Cp + Cw is not in the second predetermined range of 0.29 × Cg-1.86 or more and 0.29 × Cg + 0.95 or less, the synthetic capacity Cp + Cw is the second predetermined. Provided is a manufacturing method for adjusting at least one of Cp, Cw and Cg so as to be included in the range.

Further, the present invention is a third manufacturing method as a fourth manufacturing method of a noise filter.
The manufacturing method includes a measurement step and includes a measurement step.
In the measurement step, the pattern capacitance Cp of the circuit board is measured, and the pattern capacitance Cp is measured.
In the adjustment step, when the synthetic capacity Cp + Cw is not in the second predetermined range, a manufacturing method for adjusting at least one of Cw and Cg so that the synthetic capacity Cp + Cw is included in the second predetermined range is used. offer.

Further, the present invention is any one of the first to fourth manufacturing methods as the fifth manufacturing method of the noise filter.
The two terminals in each of the coils are composed of a first terminal and a second terminal.
The four electrodes of the circuit board consist of two first electrodes corresponding to the first terminals of the two coils and two second electrodes corresponding to the second terminals of the two coils. Become,
The grounding capacitance Cg is a capacitance between the terminal short-circuit point in which the two first terminals and the two second terminals are short-circuited and the grounding terminal.
The pattern capacitance Cp includes a first electrode short-circuit point in which the two first electrodes are short-circuited and a second electrode in which the two second electrodes are short-circuited in a state where the noise filter is not attached to the circuit board. The capacitance between the short circuit point and
The combined capacitance Cp + Cw has a first terminal short-circuit point in which the two first terminals are short-circuited and a second terminal short-circuit in which the two second terminals are short-circuited in a state where the noise filter is attached to the circuit board. Provided is a manufacturing method which is a capacitance between points.

Further, according to the present invention, as the first noise filter,
A noise filter that can be attached to a circuit board.
The noise filter includes a magnetic core, a ground conductor, and two coils.
Each of the coils has a coil portion wound around the magnetic core and two terminals drawn out from the coil portion.
The ground conductor has a conductor main portion disposed apart from the coil portion and a ground terminal drawn out from the conductor main portion.
The circuit board is provided with four electrodes each connected to the terminal of the coil and a ground electrode connected to the ground terminal of the ground conductor.
Cp + Cw, which is the combined capacitance of the pattern capacitance Cp between the electrodes of the circuit board and the winding capacitance Cw of the coil, is 0.29 in relation to the grounding capacitance Cg between the grounding conductor and the coil. Provided is a noise filter having × Cg −3.06 or more and 0.29 × Cg +2.15 or less.

Further, the present invention is a first noise filter as a second noise filter.
The combined capacity Cp + Cw provides a noise filter having 0.29 × Cg-1.86 or more and 0.29 × Cg + 0.95 or less.

Further, the present invention is a first or second noise filter as the third noise filter.
The noise filter includes a dielectric member and has a dielectric member.
The dielectric member provides a noise filter that is at least partially located between the conductor main portion and the coil portion.

Further, the present invention is any one of the first to third noise filters as the fourth noise filter.
The two terminals in each of the coils are composed of a first terminal and a second terminal.
The four electrodes of the circuit board consist of two first electrodes corresponding to the first terminals of the two coils and two second electrodes corresponding to the second terminals of the two coils. Become,
The grounding capacitance Cg is a capacitance between the terminal short-circuit point in which the two first terminals and the two second terminals are short-circuited and the grounding terminal.
The pattern capacitance Cp includes a first electrode short-circuit point in which the two first electrodes are short-circuited and a second electrode in which the two second electrodes are short-circuited in a state where the noise filter is not attached to the circuit board. The capacitance between the short circuit point and
The combined capacitance Cp + Cw has a first terminal short-circuit point in which the two first terminals are short-circuited and a second terminal short-circuit in which the two second terminals are short-circuited in a state where the noise filter is attached to the circuit board. Provided is a noise filter which is a capacitance between points.

Further, according to the present invention, as the first device,
A device equipped with any of the first to fourth noise filters and a circuit board.
The circuit board is provided with a device provided with four electrodes each connected to the terminal of the coil and a ground electrode connected to the ground terminal of the ground conductor.

According to the manufacturing method of the present invention, Cp + Cw, which is the combined capacitance of the pattern capacitance Cp of the circuit board and the winding capacitance Cw of the coil, is at least 0.29 × Cg-3 in relation to the grounding capacitance Cg of the grounding conductor. It is adjusted so as to be included in the first predetermined range of .06 or more and 0.29 × Cg + 2.15 or less. By this adjustment, the noise of 10 MHz can be attenuated by about 40 dB, and thereby the noise attenuation bandwidth can be widened.

It is a perspective view which shows the noise filter and the circuit board in embodiment of this invention. It is a top view which shows the noise filter and the circuit board of FIG. The outline of the coil of the noise filter is schematically drawn with a broken line. The noise filter is not drawn except for the outlines of the outer peripheral portion and the protruding portion of the case shown by the alternate long and short dash line. It is a figure which shows the equivalent circuit of the noise filter of FIG. 1 and a circuit board. It is a figure which shows the winding capacity Cw of the noise filter of FIG. It is a figure which shows the pattern capacitance Cp of the circuit board of FIG. It is a figure which shows the combined capacitance Cp + Cw of the pattern capacitance Cp and the winding capacitance Cw in the noise filter and the circuit board of FIG. It is a figure which shows the grounding capacity Cg of the noise filter of FIG. It is a figure which shows the relationship between the grounding capacity Cg and the synthetic capacity Cp + Cw. It is a flowchart which shows an example of the manufacturing method of the noise filter of FIG. It is a flowchart which shows the modification of the manufacturing method of FIG. It is a figure which shows the noise filter of Examples 1 to 6 of this invention. It is a figure which shows the relationship between the frequency and the attenuation in the noise filter of Example 1. FIG. It is a figure which shows the relationship between the frequency and the attenuation in the noise filter of Example 2. FIG. It is a figure which shows the relationship between the frequency and the attenuation in the noise filter of Example 3. FIG. It is a figure which shows the relationship between the frequency and the attenuation amount in the noise filter of Example 4. FIG. It is a figure which shows the relationship between the frequency and the attenuation amount in the noise filter of Example 5. It is a figure which shows the relationship between the frequency and the attenuation amount in the noise filter of Example 6. It is a figure which shows the relationship between the synthesis capacity Cp + Cw and the attenuation amount with respect to the noise of 10MHz for each of the noise filters of Examples 1-6. It is a figure which shows the relationship between the grounding capacity Cg and the combined capacity Cp + Cw about the noise filter of Examples 1-6.

Referring to FIGS. 1 and 2, the apparatus 10 according to the embodiment of the present invention includes a noise filter 20 and a circuit board 80. The noise filter 20 is used by being attached to the circuit board 80 of the apparatus 10. The device 10 is, for example, a part of a power conversion device, and the common mode noise generated in the power supply line is attenuated by the noise filter 20. That is, the noise filter 20 of the present embodiment is a common mode choke coil that attenuates common mode noise. However, the present invention can also be applied to a normal mode choke coil that attenuates normal mode noise.

In the present embodiment, two first electrodes (electrodes) 82, two second electrodes (electrodes) 84, and a ground electrode 88 are formed on the upper surface (+ Z side surface) of the circuit board 80. There is. The first electrode 82 and the second electrode 84 are connected to a circuit (not shown) of the device 10. The ground electrode 88 is grounded. The circuit board 80 of the present embodiment is a part of the circuit board (not shown) of the device 10 (for example, a power conversion device), and has the shape and size shown in the figure. However, as long as the circuit board 80 is provided with the four electrodes 82, 84 and the ground electrode 88, the shape and size of the circuit board 80 are not particularly limited.

The noise filter 20 of the present embodiment includes a case 30 made of an insulator, a magnetic core 40 made of a soft magnetic material, a ground conductor 50 made of a conductor, and two coils 60. However, the present invention is not limited to this. For example, the case 30 may be provided as needed. Further, the noise filter 20 may further include another member in addition to the above-mentioned member.

Referring to FIG. 2, the magnetic core 40 of the present embodiment is, for example, a powder magnetic core composed of a soft magnetic metal powder and a binder such as a resin. Further, the magnetic core 40 has a toroidal shape. Specifically, the magnetic core 40 is formed with a central hole 42. The central hole 42 penetrates the magnetic core 40 in the vertical direction (Z direction). The magnetic core 40 has an annular shape centered on the central hole 42 in a horizontal plane (XY plane) orthogonal to the Z direction. However, the present invention is not limited to this. For example, the magnetic core 40 is not limited to the dust core. Further, the shape of the magnetic core 40 in the XY plane is not limited to the annular shape. For example, the magnetic core 40 may have a rectangular frame shape or a magnetic gap in the XY plane.

The ground conductor 50 has a conductor main portion 52 and a ground terminal 58. The grounding conductor 50 of the present embodiment is, for example, a thin metal plate made of copper, and the conductor main portion 52 and the grounding terminal 58 are integrally formed with each other. In other words, each of the conductor main portion 52 and the ground terminal 58 is a part of one ground conductor 50. The conductor main portion 52 extends along the outer circumference of the magnetic core 40 while keeping a slight distance from the outer circumference of the magnetic core 40 in the XY plane. The ground terminal 58 is drawn out from the conductor main portion 52 in the front-rear direction (X direction) in the front (+ X direction), and is connected to and fixed to the ground electrode 88 of the circuit board 80 when the noise filter 20 is used. However, the present invention is not limited to this. For example, the conductor main portion 52 may cover the upper surface (+ Z side surface) and the lower surface (−Z side surface) of the magnetic core 40. Further, the ground terminal 58 is a member formed separately from the conductor main portion 52, and may be welded to the conductor main portion 52.

Referring to FIG. 1, the case 30 of the present embodiment has a base portion 32 and a main body portion 34. The main body portion 34 is located above the base portion 32 (+ Z side). The base 32 is fixed to the upper surface of the circuit board 80 when the noise filter 20 is used. The base 32 is formed with four passage holes 322 corresponding to the four electrodes 82 and 84 of the circuit board 80, respectively. Each of the passage holes 322 penetrates the base 32 in the Z direction and is located above the corresponding electrodes 82, 84 when the noise filter 20 is used.

Referring to FIGS. 1 and 2, the main body 34 of the case 30 has a shape corresponding to an internal structure composed of a magnetic core 40 and a ground conductor 50, and the internal structure (magnetic core 40 and ground conductor 50). ) Is housed inside the main body 34. Specifically, the main body portion 34 has an outer peripheral portion (dielectric member) 36 and a protruding portion 38. Referring to FIG. 2, the outer peripheral portion 36 covers the conductor main portion 52 of the ground conductor 50 from the outside in the XY plane, whereby the conductor main portion 52 is sandwiched between the conductor main portions 52 in the XY plane and the magnetic core 40. It covers the outer circumference from the outside. In other words, the conductor main portion 52 is located between the outer periphery of the magnetic core 40 and the outer peripheral portion 36 of the case 30 in the XY plane. Further, the protrusion 38 covers the ground terminal 58 of the ground conductor 50 from the outside in the XY plane. That is, the ground terminal 58 is connected to the ground electrode 88 of the circuit board 80 inside the case 30.

The case 30 of this embodiment has the above-mentioned structure. However, the structure of the case 30 can be variously deformed according to the structure of the internal structure (magnetic core 40 and ground conductor 50). Further, the internal structure may be partially exposed to the outside of the case 30. For example, the ground terminal 58 may be connected to the ground electrode 88 outside the case 30.

Referring to FIGS. 1 and 2, each of the coils 60 has a coil portion 62, a first terminal (terminal) 66, and a second terminal (terminal) 68. Each of the coils 60 of the present embodiment is, for example, a coated conductor wire made of an insulatingly coated copper. Further, in each of the coils 60, the coil portion 62, the first terminal 66, and the second terminal 68 are each a part of one coated conducting wire. However, the present invention is not limited to this. For example, in each of the coils 60, each of the first terminal 66 and the second terminal 68 is a member formed separately from the coil portion 62, and may be welded to the end of the coil portion 62. Further, the coil 60 may be a round conductor or a flat conductor.

According to the present embodiment, the two coils 60 are wound on both sides of the main body 34 of the case 30 in the Y direction (lateral direction) apart from each other. Specifically, the coil portion 62 of one coil 60 is wound around the + Y side of the main body portion 34 for one turn or more, and the coil portion 62 of the other coil 60 is wound around the −Y side of the main body portion 34 for one turn or more. It is being wound.

According to the present embodiment, each of the coil portions 62 is wound around the main body portion 34 of the case 30, whereby the main body portion 34 is sandwiched between the coil portions 62 and the coil portions 62 are indirectly wound around the magnetic core 40. ing. That is, the coil portion 62 is arranged outside the case 30. Referring to FIG. 2, the outer peripheral portion 36 of the case 30 is located between the coil portion 62 and the conductor main portion 52 of the ground conductor 50 in the XY plane. That is, the conductor main portion 52 is separated from the coil portion 62.

The arrangement of the coil portion 62 and the arrangement of the conductor main portion 52 in the present invention are not limited to the above-mentioned arrangement. For example, each of the coil portions 62 may be arranged inside the case 30. More specifically, each of the coil portions 62 may be wound directly around the magnetic core 40. In this case, the conductor main portion 52 may be disposed apart from the coil portion 62 on the XY plane so as to cover the coil portion 62 from the outside with the outer peripheral portion 36 of the case 30 sandwiched between them. However, when it is necessary to adjust the number of turns (number of turns) of each coil portion 62 after the noise filter 20 is once manufactured, this embodiment is preferable.

According to the present embodiment, each of the coil portions 62 is wound so that the turns do not overlap each other. In other words, each of the coil portions 62 is further wound in a certain direction in the circumferential direction on the XY plane centered on the central hole 42 of the magnetic core 40. However, the winding method of the coil portion 62 according to the present invention is not particularly limited. For example, each of the coil portions 62 may be wound in multiple layers by winding in the clockwise direction in the circumferential direction and then in the counterclockwise direction.

Referring to FIGS. 1 and 2, the first terminal 66 of the two coils 60 corresponds to the two first electrodes 82 of the circuit board 80, respectively, and the second terminal 68 of the two coils 60 corresponds to the circuit board. It corresponds to each of the two second electrodes 84 of 80. In each of the coils 60, the two terminals 66 and 68 are respectively drawn out from both ends of the coil portion 62. Specifically, each of the first terminals 66 is pulled out forward (+ X direction) in the X direction, and when the noise filter 20 is used, it passes through the passage hole 322 of the case 30 and reaches the corresponding first electrode 82. Connected and fixed. Each of the second terminals 68 is pulled out rearward (-X direction) in the X direction, passes through the passage hole 322 of the case 30, and is connected to the corresponding second electrode 84 when the noise filter 20 is used. It is fixed.

As described above, the circuit board 80 includes four electrodes 82, 84 connected to the four terminals 66, 68 of the two coils 60, respectively, and a ground electrode 88 connected to the ground terminal 58 of the ground conductor 50. Is provided. According to the present embodiment, the two terminals 66 and 68 in each of the coils 60 are composed of a first terminal 66 and a second terminal 68. Further, the four electrodes 82 and 84 of the circuit board 80 each correspond to two first electrodes 82 corresponding to the first terminal 66 of the two coils 60 and two corresponding to the second terminal 68 of the two coils 60, respectively. It is composed of a second electrode 84.

Referring to FIGS. 2 and 3, the noise filter 20 of the present embodiment is a pseudo-distributed constant type line filter provided with a ground conductor 50, and is effective not only for low frequency band noise but also for high frequency band noise. Attenuate. In other words, the noise filter 20 has excellent attenuation characteristics in the high frequency band. The noise filter 20 forms the equivalent circuit shown in FIG. 3 together with the circuit board 80.

Referring to FIG. 3, each of the coils 60 has a self-inductance Lw and an equivalent series resistance Rw. In addition, in each of the coils 60, a partial winding capacity Cwx is formed between the first terminal 66 and the second terminal 68, and the first electrode 82 to which the first terminal 66 is connected is formed. A partial pattern capacitance Cpx is formed between the second electrode 84 and the second electrode 84 to which the second terminal 68 is connected. Further, a distributed grounding capacitance Cgx is formed between the coil 60 and the grounding conductor 50. The distributed grounding capacitance Cgx is dispersed and parasitized between each of the coil portions 62 and the conductor main portion 52 of the grounding conductor 50. However, in FIG. 3, the distributed grounding capacitance Cgx is drawn collectively at both ends of each of the coil portions 62.

As can be seen from FIGS. 3 and 4, the noise filter 20 is formed with a winding capacitance Cw (see FIG. 4) due to the partial winding capacitance Cwx drawn in FIG. The winding capacitance Cw is the first terminal short-circuit point ST1 in which the two first terminals 66 are short-circuited and the second terminal 68 in which the two second terminals 68 are short-circuited in a state where the noise filter 20 is not attached to the circuit board 80. Capacitance between the terminal short circuit point ST2. Generally, the winding capacitance Cw lowers the self-resonant frequency of the noise filter 20 and deteriorates the frequency characteristics of the noise filter 20. More specifically, the frequency range (attenuation bandwidth) capable of attenuating noise by 40 dB or more is narrowed.

In addition, as can be seen from FIGS. 3 and 5, the circuit board 80 is formed with a pattern capacitance Cp (see FIG. 5) resulting from the partial pattern capacitance Cpx drawn in FIG. The pattern capacitance Cp is the first electrode short-circuit point SE1 in which the two first electrodes 82 are short-circuited and the second electrode in which the two second electrodes 84 are short-circuited in a state where the noise filter 20 is not attached to the circuit board 80. It is the electrostatic capacity between the short circuit point SE2 and the short circuit point SE2. That is, the pattern capacitance Cp can be measured by measuring the capacitance between the first electrode short-circuit point SE1 and the second electrode short-circuit point SE2 in a state where the noise filter 20 is not attached to the circuit board 80. The capacitance such as the pattern capacitance Cp may be measured by, for example, an impedance analyzer or an LCR meter.

Referring to FIGS. 2 and 3, the pattern capacitance Cp is formed in parallel with the noise filter 20 in a state where the noise filter 20 is attached to the circuit board 80. Specifically, due to the capacitive coupling between the first electrode 82 and the second electrode 84, a path through which noise passes is formed parallel to the noise filter 20. As the frequency of the noise increases, the proportion of noise that passes through this path increases, which makes it impossible for the noise filter 20 to attenuate the noise. In particular, the noise filter 20, which is a pseudo-distributed constant type line filter, has excellent attenuation characteristics in a high frequency band, and therefore has a pattern capacitance as compared with a noise filter (not shown) that does not have a ground conductor 50. Susceptible to Cp.

In the present invention, the pattern capacitance Cp, together with the winding capacitance Cw, has a non-negligible effect on the frequency characteristics of the noise filter 20. In other words, referring to FIGS. 3 and 6, the frequency characteristic of the noise filter 20 may be deteriorated by Cp + Cw, which is the combined capacitance of the pattern capacitance Cp and the winding capacitance Cw of the coil 60.

The combined capacitance Cp + Cw in the present embodiment short-circuits the first terminal short-circuit point ST1 in which the two first terminals 66 are short-circuited and the two second terminals 68 in a state where the noise filter 20 is attached to the circuit board 80. It is the capacitance between the second terminal short-circuit point ST2 and the second terminal. That is, the combined capacitance Cp + Cw can be measured by measuring the capacitance between the first terminal short-circuit point ST1 and the second terminal short-circuit point ST2 in a state where the noise filter 20 is attached to the circuit board 80.

As described above, the frequency characteristics of the noise filter 20 may be deteriorated by the combined capacitance Cp + Cw. On the other hand, referring to FIGS. 3 and 7, a grounding capacitance Cg due to the distributed grounding capacitance Cgx is formed in the noise filter 20. The grounding capacitance Cg is the capacitance between the terminal short-circuit point ST in which the two first terminals 66 and the two second terminals 68 are short-circuited, and the grounding terminal 58. That is, the grounding capacitance Cg can be measured by measuring the capacitance between the terminal short-circuit point ST and the grounding terminal 58.

According to the present invention, the ground contact capacitance Cg functions as if the combined capacitance Cp + Cw is canceled by a certain amount. More specifically, the frequency characteristics of the noise filter 20 can be improved by adjusting the noise filter 20 so that the combined capacitance Cp + Cw satisfies a suitable relationship with respect to the grounding capacitance Cg. For example, the frequency characteristics of the noise filter 20 can be improved by adjusting the number of turns of the coil portion 62 in each of the coils 60 and adjusting the size of the conductor main portion 52 of the ground conductor 50.

Generally, the measured value of the grounding capacitance Cg is slightly different between the case where the noise filter 20 is measured without being attached to the circuit board 80 and the case where the noise filter 20 is measured when the noise filter 20 is attached to the circuit board 80. However, when adjusting the noise filter 20, no practical problem occurs regardless of which value is used. The measured values of the combined capacity Cp + Cw (measured combined capacity: see FIG. 6) are the measured values of the pattern capacity Cp (measured Cp: see FIG. 5) and the measured values of the winding capacity Cw (measured Cw: see FIG. 4). It may be slightly different from the simple sum of. "Synthetic capacity Cp + Cw" in the following description is a measured synthetic capacity. However, when adjusting the noise filter 20, no practical problem occurs regardless of whether the measured combined capacity or the measured Cp + the measured Cw is used.

With reference to FIGS. 3 and 8, as will be described later, the inventor of the present application has measured and considered a suitable relationship between the combined capacitance Cp + Cw and the ground contact capacitance Cg using various examples. As a result, this suitable relationship could be identified. More specifically, it was found that the frequency characteristics of the noise filter 20 can be improved when the combined capacitance Cp + Cw is included in a predetermined range with respect to the grounding capacitance Cg.

The above-mentioned predetermined range for the synthetic capacity Cp + Cw is the synthetic capacity Cp + Cw ≧ 0.29 × Cg-3.06 (first lower limit formula) and the synthetic capacity Cp + Cw ≦ 0.29 × Cg + 2.15 (first upper limit formula). It is the first predetermined range that satisfies. That is, Cp + Cw, which is the combined capacitance of the pattern capacitance Cp and the winding capacitance Cw of the coil 60, is 0.29 × Cg-3.06 or more and 0 in the first predetermined range in relation to the grounding capacitance Cg. It is .29 × Cg + 2.15 or less. When the combined capacitance Cp + Cw is in the first predetermined range, the noise of 10 MHz can be attenuated by 35 dB or more, whereby the attenuation bandwidth capable of attenuating the noise by 40 dB or more can be widened. That is, the frequency characteristics of the noise filter 20 can be improved.

Further, more preferable predetermined ranges for the synthetic capacity Cp + Cw are the synthetic capacity Cp + Cw ≧ 0.29 × Cg-1.86 (second lower limit formula) and the synthetic capacity Cp + Cw ≦ 0.29 × Cg + 0.95 (second upper limit formula). It is the second predetermined range that satisfies the formula). That is, the combined capacity Cp + Cw is 0.29 × Cg-1.86 or more and 0.29 × Cg + 0.95 or less in relation to the ground contact capacity Cg in the second predetermined range included in the first predetermined range. be. When the combined capacitance Cp + Cw is in the second predetermined range, the noise of 10 MHz can be attenuated by 40 dB or more, whereby the attenuation bandwidth capable of attenuating the noise by 40 dB or more can be further widened. That is, the frequency characteristics of the noise filter 20 can be further improved.

As will be described later, according to the measurement and consideration using various examples, the preferable value of the synthetic capacity Cp + Cw with respect to the ground contact capacity Cg is the formula (suitable formula) of the synthetic capacity Cp + Cw = 0.29Cg-0.45. It is a value to be satisfied. This preferred equation is not a proportional relational expression between the synthetic capacity Cp + Cw and the ground contact capacity Cg, but a linear relational expression having an intercept (−0.45). The attenuation characteristic of the noise filter 20 is influenced by various factors (for example, the parasitic inductor component of the magnetic core 40, the coil 60 and the ground conductor 50) in addition to the grounding capacitance Cg and the combined capacitance Cp + Cw. The intercept in the preferred formula is believed to result from these factors. Further, since the preferred equation has an intercept, each of the first lower limit equation, the first upper limit equation, the second upper limit equation, and the second upper limit equation is a linear relational expression having an intercept.

Referring to FIGS. 2 and 3, for example, increasing the number of turns of each coil 60 increases the combined capacity Cp + Cw, and decreasing the number of turns of each coil 60 decreases the combined capacity Cp + Cw. Therefore, by adjusting the number of turns of each of the coils 60, the combined capacitance Cp + Cw can be adjusted so as to be included in the first predetermined range or the second predetermined range. In addition, by increasing the size (thickness) centered on the center hole 42 in the XY plane of the conductor main portion 52 of the grounding conductor 50 and the size (height) in the Z direction, the grounding capacity Cg increases, and the conductor main By reducing the thickness and height of the portion 52, the ground contact capacity Cg is reduced. Therefore, by adjusting the thickness and height of the conductor main portion 52, the combined capacitance Cp + Cw can be adjusted so as to be included in the first predetermined range or the second predetermined range.

As described above, the noise filter 20 of the present embodiment has the physical structure shown in FIGS. 1 and 2. However, as long as the noise filter 20 and the circuit board 80 have the grounding capacitance Cg and the combined capacitance Cp + Cw, that is, as long as the noise filter 20 forms the equivalent circuit shown in FIG. 3 when connected to the circuit board 80. The physical structure of the noise filter 20 is not particularly limited. For example, the noise filter 20 of the present embodiment includes an outer peripheral portion (dielectric member) 36, which increases the ground contact capacity Cg as compared with the case where the dielectric member 36 is not provided. However, the dielectric member 36 may be provided as needed. On the other hand, in addition to the dielectric member 36, a dielectric member (not shown) made of a dielectric having a higher dielectric constant may be provided. The dielectric member including the dielectric member 36 may be located at least partially between the conductor main portion 52 and the coil portion 62.

Referring to FIG. 9 in conjunction with FIGS. 1, 2 and 8, the noise filter 20 of this embodiment can be manufactured, for example, as shown in FIG. The manufacturing process shown in FIG. 9 includes an adjustment process.

First, the noise filter 20 and the circuit board 80 to be adjusted are prepared. The noise filter 20 and the circuit board 80 to be adjusted may be manufactured, for example, in a primary manufacturing process (not shown) before the adjustment process. Next, in the adjustment step, the prepared noise filter 20 and the circuit board 80 are used to measure Cp + Cw, which is the combined capacitance of the pattern capacitance Cp and the winding capacitance Cw (STEP 1). Specifically, the combined capacitance Cp + Cw is measured with the noise filter 20 attached to the circuit board 80.

In the adjustment step, next, the combined capacity Cp + Cw is 0.29 × grounding capacity Cg + Bmin (Bmin is −3.06 or -1.86) or more and 0.29 × grounding in relation to the grounding capacity Cg. It is confirmed whether or not the volume is within the predetermined range (first predetermined range or second predetermined range) of Cg + Bmax (Bmax is 2.15 or 0.95) or less (first half of STEP 2). When it is within the predetermined range (first predetermined range or second predetermined range), the noise filter 20 and the circuit board 80 manufactured in the primary manufacturing process (not shown) are used as they are. On the other hand, when it is not within the predetermined range (first predetermined range or second predetermined range), at least one of the pattern capacity Cp, the winding capacity Cw, and the grounding capacity Cg is set so that the combined capacity Cp + Cw is included in the predetermined range. Adjust (second half of STEP2). Through the above adjustment steps, the noise filter 20 suitable for the circuit board 80 can be manufactured.

According to the above-mentioned manufacturing method, when it is desired to manufacture the noise filter 20 in which the combined capacity Cp + Cw is included in the first predetermined range, the noise filter 20 may be adjusted so as to be included in the first predetermined range in the adjusting step. On the other hand, when it is desired to manufacture the noise filter 20 in which the combined capacity Cp + Cw is included in the second predetermined range, the noise filter 20 may be adjusted so as to be included in the second predetermined range in the adjusting step.

More specifically, when the combined capacity Cp + Cw> 0.29 × Cg + Bmax (Bmax is 2.15 or 0.95), at least one of the pattern capacity Cp and the winding capacity Cw is lowered, or The grounding capacity Cg may be increased. On the other hand, when the combined capacitance Cp + Cw <0.29 × Cg + Bmin (Bmin is −3.06 or -1.86), at least one of the pattern capacitance Cp and the winding capacitance Cw is increased, or the grounding capacitance is increased. The Cg may be lowered.

Each of the winding capacity Cw and the grounding capacity Cg can be adjusted by changing the structure of the noise filter 20 as described above. For example, the winding capacity Cw can be lowered by reducing the number of turns of the coil portion 62, and can be increased by increasing the number of turns. The winding capacity Cw can be adjusted by changing the winding method such as single-layer winding and multi-layer winding. The ground contact capacity Cg can be increased, for example, by increasing the area of the conductor main portion 52 or by inserting a dielectric member (not shown) having a high dielectric constant between the conductor main portion 52 and the coil portion 62. On the other hand, the ground contact capacitance Cg can be lowered, for example, by reducing the area of the conductor main portion 52.

When adjusting the winding capacity Cw or the grounding capacity Cg, if the winding capacity Cw is adjusted, the grounding capacity Cg also changes slightly, and if the grounding capacity Cg is adjusted, the winding capacity Cw also changes slightly. However, in general, the adjustment of the winding capacity Cw and the grounding capacity Cg changes significantly. Therefore, the combined volume Cp + Cw can be included in the first predetermined range or the second predetermined range by adjusting at most several times.

In addition to adjusting the winding capacity Cw and the grounding capacity Cg, the pattern capacity Cp can be adjusted by changing the structure of the circuit board 80. The pattern capacitance Cp can be reduced, for example, by reducing the size (area) of the electrodes 82 and 84 of the circuit board 80 on the XY plane. In particular, the pattern capacitance Cp reduces the size (edge size) of the edges of the electrodes 82 and 84 sandwiching the noise filter 20 in the X direction in the Y direction, and reduces the size (edge size) of the edges of the first electrode 82 and the second electrode 84. It can be lowered by increasing the distance between the edges in the X direction (distance between edges). On the other hand, the pattern capacitance Cp can be increased, for example, by increasing the area of the electrodes 82, 84 (particularly, the edge size) or reducing the distance between the edges.

As described above, by adjusting at least one of the pattern capacitance Cp, the winding capacitance Cw, and the grounding capacitance Cg, the noise filter 20 in which the combined capacitance Cp + Cw is included in the first predetermined range or the second predetermined range can be manufactured. However, it is not easy to change the electrodes 82 and 84 of the circuit board 80 that have already been prepared. In addition, it is not easy to change the conductor main portion 52 arranged inside the noise filter 20 already prepared. In particular, it is difficult to increase the size of the manufactured conductor main portion 52. Further, while it is relatively easy to reduce the number of turns of the coil portion 62, it is difficult to increase the number of turns of the coil portion 62. In addition, the adjustment of the number of turns of the coil portion 62 affects the self-inductance Lw. In consideration of the above points, at least one of the pattern capacitance Cp, the winding capacitance Cw, and the grounding capacitance Cg may be adjusted.

Generally, the circuit board 80 is a part of a circuit board on which various electronic components (not shown) other than the noise filter 20 are mounted, and may have already been prepared when the noise filter 20 is manufactured. many. In such a case, it is difficult to change the structure of the circuit board 80 according to the noise filter 20. Therefore, it is preferable to make adjustments by slightly changing the structure of the noise filter 20. That is, in the adjustment step, when the combined capacity Cp + Cw is not in the first predetermined range (second predetermined range), the combined capacity Cp + Cw is included in the first predetermined range (second predetermined range) among Cw and Cg. It is preferable to adjust at least one of the above.

According to the above-mentioned manufacturing method, Cp + Cw, which is a combined capacitance of the pattern capacitance Cp of the circuit board 80 and the winding capacitance Cw of the coil 60, is at least 0.29 × Cg in relation to the grounding capacitance Cg of the grounding conductor 50. It is adjusted so as to be included in the first predetermined range of −3.06 or more and 0.29 × Cg + 2.15 or less. By this adjustment, the noise of 10 MHz can be attenuated by about 40 dB, and thereby the noise attenuation bandwidth can be widened.

By attaching the noise filter 20 manufactured by the manufacturing method including the above-mentioned adjustment step to the circuit board 80, the noise filter 20 and the apparatus 10 having excellent frequency characteristics can be obtained. Further, by manufacturing the noise filter 20 having the same structure as the noise filter 20, the noise filter 20 and the apparatus 10 manufactured through the adjustment step indirectly without directly going through the adjustment step. Is obtained.

The manufacturing method shown in FIG. 9 can be variously modified. For example, referring to FIG. 10 together with FIGS. 1, 2, 8 and 9, the manufacturing method shown in FIG. 10 includes a measurement step, a preparation step, and an adjustment step. STEPM3 and STEP4 of the adjustment step of FIG. 10 are the same steps as STEP1 and STEP2 of the adjustment step of FIG. According to the manufacturing method shown in FIG. 9, when the combined capacity Cp + Cw is significantly out of the first predetermined range, adjustment in the adjusting step may be difficult. As will be described below, according to the manufacturing method shown in FIG. 10, adjustment in the adjustment step becomes easy.

According to the manufacturing method shown in FIG. 10, first, in the measurement step, the circuit board 80 to which the noise filter 20 is attached is prepared, and the pattern capacitance Cp of the prepared circuit board 80 is measured (STEPM1).

Next, in the preparation step, a noise filter 20 having a grounding capacitance Cg satisfying the conditional expression of the measured pattern capacitance Cp <0.29 × Cg + Cmax is prepared (STEPM2). The Cmax in this conditional expression is 2.15 when the noise filter 20 in which the combined capacity Cp + Cw is included in the first predetermined range is desired to be manufactured, and the noise filter 20 in which the combined capacity Cp + Cw is included in the second predetermined range is desired to be manufactured. In some cases, it is 0.95.

More specifically, referring to FIG. 8, a straight line satisfying the equation of synthetic capacity Cp + Cw = measured pattern capacity Cp and synthetic capacity Cp + Cw = 0.29 × Cg + Cmax (Cmax is 2.15 or 0.95). Find the intersection with a straight line that satisfies the formula (first upper limit formula or second upper limit formula). For example, the intersection 1 or the intersection 2 shown in FIG. 8 is obtained. Next, a noise filter 20 having a grounding capacitance Cg higher than the grounding capacitance Cg at this intersection is prepared. For example, in a primary manufacturing process (not shown) prior to the measurement step, a plurality of noise filters 20 having various ground contact capacities Cg may be manufactured in advance. In this case, in the preparation step, the noise filter 20 that satisfies the conditions may be selected according to the measured pattern capacitance Cp. On the other hand, in the preparation step, the noise filter 20 satisfying the conditions may be manufactured according to the measured pattern capacitance Cp.

As described above, it is difficult to increase the ground contact capacitance Cg of the noise filter 20 manufactured in the primary manufacturing process (not shown). Therefore, it is difficult to manufacture the noise filter 20 included in the first predetermined range or the second predetermined range by using the noise filter 20 having a grounding capacitance Cg lower than the grounding capacitance Cg at the above-mentioned intersection. According to the manufacturing method of FIG. 10, since the noise filter 20 having a relatively high ground contact capacity Cg is prepared in the preparation step, the adjustment in the adjustment step becomes easy.

The present invention could be obtained by measurement and consideration using various examples including Examples 1 to 6 described below.

With reference to FIG. 11, six noise filters of Examples 1 to 6 were prepared. The features of Examples 1 to 6 are shown in Table 1. The noise filters of Examples 1 to 6 had the same basic structure as the noise filters 20 shown in FIGS. 1 and 2. In particular, Example 3 and Example 5 had the same shape and size except that the width of the ground conductor was different.

The frequency characteristics of each of Examples 1 to 6 were measured with each of Examples 1 to 6 attached to the circuit board. Specifically, for each of Examples 1 to 6, the amount of noise attenuation (dB) at various frequencies was measured while variously changing the value of the combined capacitance Cp + Cw. In particular, in the first embodiment, the pattern capacitance Cp is variously set for the two winding capacitance Cw, which is the winding capacitance Cw in the initial state of 1.65 pF and the adjusted winding capacitance Cw of 0.55 pF. Measured while changing. Similarly, in the second embodiment, the pattern capacitance Cp is various for the two winding capacitance Cw, which is the winding capacitance Cw in the initial state of 2.25 pF and the adjusted winding capacitance Cw of 2.15 pF. It was measured while changing to. On the other hand, for each of Examples 3 to 6, the measurement was performed while maintaining the winding capacity Cw at the value shown in Table 1 and changing the pattern capacity Cp in various ways.

12 to 17 show the measurement results for Examples 1 to 6, respectively. As can be understood from FIGS. 12 to 17, it was found that the noise in a wide frequency band can be attenuated by 40 dB or more by adjusting the combined capacitance Cp + Cw so that the amount of attenuation of the noise of 10 MHz is maximized.

Based on the measurement results shown in FIGS. 12 to 17, a graph of the amount of noise attenuation at 10 MHz with respect to the combined capacitance Cp + Cw was created for each of Examples 1 to 6. FIG. 18 shows the created graph.

Table 2 shows the change range (measurement range) of the combined capacitance Cp + Cw in the above-mentioned measurement of the frequency characteristics for each of Examples 1 to 6 together with the measurement results. As a measurement result, a suitable value of the combined capacitance Cp + Cw, a first predetermined range (a range of the first lower limit value or more and a first upper limit value or less) and a second predetermined range (a range of the second lower limit value or more and a second upper limit value or less). Is shown together with the amount of attenuation. The preferable value of the combined capacitance Cp + Cw is the value when the noise of 10 MHz can be attenuated to the maximum. The first predetermined range of the combined capacitance Cp + Cw is a range of not more than the lower limit value (first lower limit value) and not more than the upper limit value (first upper limit value) when the noise of 10 MHz can be attenuated by 35 dB or more. The second predetermined range of the combined capacitance Cp + Cw is a range of not more than the lower limit value (second lower limit value) and not more than the upper limit value (second upper limit value) when the noise of 10 MHz can be attenuated by 40 dB or more.

FIG. 19 plots and shows the measurement results of Table 2. The preferred values in Table 2 are plotted in the double white circles in FIG. 19, the second upper limit value and the second lower limit value in Table 2 are plotted in the black circles in FIG. 19, and the first upper limit value in Table 2 is plotted. And the first lower limit are plotted in the white circles in FIG. With reference to Table 2 and FIG. 19, an attenuation of 40 dB or more is obtained for 10 MHz noise in the range of +1.6 to −1.6 pF with reference to the preferable value of the combined capacitance Cp + Cw. Further, based on the preferable value of the combined capacitance Cp + Cw, an attenuation amount of 35 dB or more is obtained for a noise of 10 MHz in the range of +2.8 to -2.9 pF.

The relationship between the value of the suitable value of the combined capacity Cp + Cw with respect to the grounding capacity Cg was approximated to a linear formula by the least squares method, and the formula (provisional suitable formula) of the combined capacity Cp + Cw = 0.2904Cg −0.4519 was obtained. With the number of significant digits of the provisional suitable formula being 2 digits, a formula (suitable formula) with a combined capacity of Cp + Cw = 0.29 Cg-0.45 was obtained. Further, for each of the first upper limit value, the first lower limit value, the second upper limit value, and the second lower limit value of the combined capacity Cp + Cw, the relationship with respect to the grounding capacity Cg was approximated by a linear equation with the combined capacity Cp + Cw = 0.29 Cg + x. .. As a result, for each of the first upper limit value, the first lower limit value, the second upper limit value, and the second lower limit value of the combined capacity Cp + Cw, the first upper limit formula with the combined capacity Cp + Cw = 0.29 Cg + 2.15, the combined capacity Cp + Cw = The first lower limit formula with 0.29 Cg-3.06, the second upper limit formula with synthetic capacity Cp + Cw = 0.29 Cg + 0.95, and the second lower limit formula with synthetic capacity Cp + Cw = 0.29 Cg-1.86 are obtained. rice field.

As described above, from the measurement results and considerations of various examples, the second predetermined range of the synthetic capacity Cp + Cw ≧ 0.29 × Cg-1.86 and the synthetic capacity Cp + Cw ≦ 0.29 × Cg + 0.95 is set. Obtained. Further, the first predetermined range of the synthetic capacity Cp + Cw ≧ 0.29 × Cg-3.06 and the synthetic capacity Cp + Cw ≦ 0.29 × Cg + 2.15 was obtained. According to the above measurements and considerations, when the combined capacitance Cp + Cw is included in the first predetermined range in relation to the grounding capacitance Cg, noise in a wide frequency band can be attenuated by 40 dB or more. Further, when the combined capacitance Cp + Cw is included in the second predetermined range in relation to the grounding capacitance Cg, noise in a wider frequency band can be attenuated by 40 dB or more.

10 Equipment 20 Noise filter 30 Case 32 Base 322 Passing hole 34 Main body 36 Outer circumference (dielectric member)
38 Protrusion 40 Magnetic core 42 Center hole 50 Ground conductor 52 Conductor main part 58 Ground terminal 60 Coil 62 Coil part 66 First terminal (terminal)
68 Second terminal (terminal)
80 Circuit board 82 First electrode (electrode)
84 Second electrode (electrode)
88 Ground electrode ST terminal short circuit point ST1 1st terminal short circuit point ST2 2nd terminal short circuit point SE1 1st electrode short circuit point SE2 2nd electrode short circuit point

Claims (10)

It is a manufacturing method of a noise filter attached to a circuit board.
The noise filter includes a magnetic core, a ground conductor, and two coils.
Each of the coils has a coil portion wound around the magnetic core and two terminals drawn out from the coil portion.
The ground conductor has a conductor main portion disposed apart from the coil portion and a ground terminal drawn out from the conductor main portion.
The circuit board is provided with four electrodes each connected to the terminal of the coil and a ground electrode connected to the ground terminal of the ground conductor.
The manufacturing method includes an adjustment step and includes an adjustment step.
In the adjustment step, Cp + Cw, which is the combined capacitance of the pattern capacitance Cp between the electrodes of the circuit board and the winding capacitance Cw of the coil, is the relationship between the grounding capacitance Cg between the grounding conductor and the coil. When it is not in the first predetermined range of 0.29 × Cg −3.06 or more and 0.29 × Cg + 2.15 or less, Cp, so that the synthetic capacity Cp + Cw is included in the first predetermined range. A manufacturing method for adjusting at least one of Cw and Cg. The manufacturing method according to claim 1.
The manufacturing method includes a measurement step and includes a measurement step.
In the measurement step, the pattern capacitance Cp of the circuit board is measured, and the pattern capacitance Cp is measured.
A manufacturing method in which at least one of Cw and Cg is adjusted so that when the synthetic capacity Cp + Cw is not within the first predetermined range in the adjustment step, the synthetic capacity Cp + Cw is included in the first predetermined range. The manufacturing method according to claim 1.
In the adjustment step, when the synthetic capacity Cp + Cw is not in the second predetermined range of 0.29 × Cg-1.86 or more and 0.29 × Cg + 0.95 or less, the synthetic capacity Cp + Cw is the second predetermined. A manufacturing method that adjusts at least one of Cp, Cw, and Cg so as to be included in the range. The manufacturing method according to claim 3.
The manufacturing method includes a measurement step and includes a measurement step.
In the measurement step, the pattern capacitance Cp of the circuit board is measured, and the pattern capacitance Cp is measured.
A manufacturing method in which at least one of Cw and Cg is adjusted so that when the synthetic capacity Cp + Cw is not in the second predetermined range in the adjustment step, the synthetic capacity Cp + Cw is included in the second predetermined range. The manufacturing method according to any one of claims 1 to 4.
The two terminals in each of the coils are composed of a first terminal and a second terminal.
The four electrodes of the circuit board consist of two first electrodes corresponding to the first terminals of the two coils and two second electrodes corresponding to the second terminals of the two coils. Become,
The grounding capacitance Cg is a capacitance between the terminal short-circuit point in which the two first terminals and the two second terminals are short-circuited and the grounding terminal.
The pattern capacitance Cp includes a first electrode short-circuit point in which the two first electrodes are short-circuited and a second electrode in which the two second electrodes are short-circuited in a state where the noise filter is not attached to the circuit board. The capacitance between the short circuit point and
The combined capacitance Cp + Cw has a first terminal short-circuit point in which the two first terminals are short-circuited and a second terminal short-circuit in which the two second terminals are short-circuited in a state where the noise filter is attached to the circuit board. A manufacturing method that is the capacitance between points. A noise filter that can be attached to a circuit board.
The noise filter includes a magnetic core, a ground conductor, and two coils.
Each of the coils has a coil portion wound around the magnetic core and two terminals drawn out from the coil portion.
The ground conductor has a conductor main portion disposed apart from the coil portion and a ground terminal drawn out from the conductor main portion.
The circuit board is provided with four electrodes each connected to the terminal of the coil and a ground electrode connected to the ground terminal of the ground conductor.
Cp + Cw, which is the combined capacitance of the pattern capacitance Cp between the electrodes of the circuit board and the winding capacitance Cw of the coil, is 0.29 in relation to the grounding capacitance Cg between the grounding conductor and the coil. A noise filter having × Cg −3.06 or more and 0.29 × Cg +2.15 or less. The noise filter according to claim 6.
The combined capacity Cp + Cw is 0.29 × Cg-1.86 or more and 0.29 × Cg + 0.95 or less. The noise filter according to claim 6 or 7.
The noise filter includes a dielectric member and has a dielectric member.
The dielectric member is a noise filter that is at least partially located between the conductor main portion and the coil portion. The noise filter according to any one of claims 6 to 8.
The two terminals in each of the coils are composed of a first terminal and a second terminal.
The four electrodes of the circuit board consist of two first electrodes corresponding to the first terminals of the two coils and two second electrodes corresponding to the second terminals of the two coils. Become,
The grounding capacitance Cg is a capacitance between the terminal short-circuit point in which the two first terminals and the two second terminals are short-circuited and the grounding terminal.
The pattern capacitance Cp includes a first electrode short-circuit point in which the two first electrodes are short-circuited and a second electrode in which the two second electrodes are short-circuited in a state where the noise filter is not attached to the circuit board. The capacitance between the short circuit point and
The combined capacitance Cp + Cw has a first terminal short-circuit point in which the two first terminals are short-circuited and a second terminal short-circuit in which the two second terminals are short-circuited in a state where the noise filter is attached to the circuit board. A noise filter that is the capacitance between points. A device including the noise filter and the circuit board according to any one of claims 6 to 9.
A device provided with four electrodes connected to the terminals of the coil and a ground electrode connected to the ground terminal of the ground conductor on the circuit board.

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