JP4012553B2 - Inductance element and signal transmission circuit - Google Patents

Description

  The present invention relates to an inductance element and a signal transmission circuit.

  One method for transmitting digital signals between electronic devices is a differential transmission method. The differential transmission system is a system in which digital signals in opposite directions are input to a pair of lines, and radiation noise generated from the signal line and external noise can be canceled by differential transmission. Since the noise is reduced by canceling out the external noise, the signal can be transmitted with a small amplitude. Further, since the signal has a small amplitude, the rise and fall times of the signal are shortened, and the signal transmission speed is increased. There is an advantage that is realized.

  Examples of interface standards using this differential transmission method include USB (Universal Serial Bus), IEEE 1394, LVDS (Low Voltage Differential Signaling), DVI (Digital Visual Interface), HDMI (High-Definition Multimedia Interface), and the like. Among these, HDMI is an interface that enables transmission of more digital signals, and is a source device (for example, a DVD player or a set-top box) and a sink device (for example, a digital TV or a projector). Etc.) is a high-speed interface that enables transmission of uncompressed digital signals. According to HDMI, a video signal and an audio signal can be transmitted at a high speed with a single cable.

By the way, with an increase in transmission speed, noise is also generated due to a minute shift of a differential signal between signal lines. In order to solve this problem, a transmission circuit that reduces noise by inserting a common mode choke coil in an interface such as a cable has been proposed (for example, see Patent Document 1).
JP 2001-85118 A JP 2004-40444 A

  In high-speed interfaces such as HDMI, the structure of the IC itself is becoming vulnerable to ESD (Electrostatic Discharge) in order to realize high speed. For this reason, there is an increasing demand for ESD countermeasures in high-speed transmission ICs, and capacitive elements such as varistors and Zener diodes are used as ESD countermeasure components.

  However, when a capacitive element as an ESD countermeasure component is inserted into a transmission line, a problem arises that a signal transmitted through the transmission line, particularly a high frequency (200 MHz or higher) or a high-speed pulse signal is reflected and attenuated. found. This is because when a capacitive element is inserted into a transmission line, the capacitive component of the capacitive element reduces the characteristic impedance at the position where the capacitive element is inserted in the transmission line, and impedance matching is performed at that position. This is due to the absence. If there is a portion of the transmission line that is not impedance matched, a high frequency component of the signal is reflected at the mismatched portion of the characteristic impedance, resulting in a return loss. As a result, the signal is greatly attenuated. In addition, unnecessary radiation may be generated in the transmission line due to reflection, which may cause noise.

  In HDMI, the specified value (TDR standard) of the characteristic impedance of the transmission line is defined as 100Ω ± 15% (High-Definition Multimedia Interface Specification Version 1.1).

  An object of the present invention is to provide a signal transmission circuit that can suppress a decrease in characteristic impedance even when a capacitive element is used as an ESD countermeasure, and an inductance element that can be used in such a signal transmission circuit. There is to do.

  An inductance element according to the present invention includes a drum core having a core portion and first and second flange portions provided at both ends of the core portion, and first and second portions formed on the first flange portion. Terminal electrode, the third and fourth terminal electrodes formed on the second collar, and the first region of the winding core portion wound in the first direction from one end to the other end, Is wound in the same direction as the first direction from one end to the other end in the first region of the core portion and the first coil connected to the first terminal electrode, and one end is the second terminal The second coil connected to the electrode and the second region different from the first region of the core portion are wound in the second direction from one end to the other end, and one end is the third terminal electrode A third coil connected to the other end of the first coil and the other end from the other end in the second region of the core portion. And a fourth coil that is wound in a direction different from the second direction, having one end connected to the fourth terminal electrode and the other end connected to the other end of the second coil. It is characterized by.

  Thus, the inductance element according to the present invention includes the first and second coils whose winding directions are the same as each other, and the third and fourth coils whose winding directions are opposite to each other. From the fourth, the first capacitive element is connected to the third terminal electrode so as to be in parallel with the first and third coils, and in parallel with the second and fourth coils. Even when the second capacitive element is connected to the terminal electrode, a decrease in characteristic impedance can be suppressed.

  Further, in the inductance element according to the present invention, the third and fourth coils are magnetically coupled to each other, and the winding directions are opposite to each other. A sufficient inductance value can be ensured with a smaller number of turns. For this reason, it is possible to suppress a decrease in characteristic impedance due to the first and second capacitive elements with a smaller inductance element.

  In addition, since the first to fourth coils are not separate components, but the paired coils are each one component that is magnetically coupled, not only the number of components can be reduced, but also the inductance value can be accurately set. As a result, the symmetry of the differential signal supplied to the first and second terminal electrodes can be maintained.

  In the present invention, the first coil and the third coil are continuous conductors, and the second coil and the fourth coil may be continuous conductors, or may be different conductors. Absent. If a continuous conductor is used, it is possible to reduce the number of conducting wires to be used. Also, a relay point between the first coil and the third coil, a relay point between the second coil and the fourth coil, etc. Since it is not necessary to provide the device, the size of the element can be reduced.

  On the other hand, when using different conductors, the fifth and sixth terminal electrodes are provided between the first region and the second region of the core part, and the other end of the first coil is connected to the fifth region. It is preferable to connect to the terminal electrode and connect the other end of the second coil to the sixth terminal electrode. If such a relay terminal is provided, more various connections are possible, and the degree of freedom in circuit design can be increased.

  In the present invention, it is preferable that the third coil and the fourth coil intersect at a plurality of locations. If the third coil and the fourth coil are wound around the second region of the core portion so as to intersect at a plurality of locations, one end of the third and fourth coils is pulled out to the second flange side, And since it becomes easy to pull out the other end of the 3rd and 4th coil to the 1st field side of a core part, it becomes possible to connect these coils, a terminal electrode, etc. easily.

  In this case, the number of crossings between the third coil and the fourth coil is preferably larger than the number of turns of the third coil and the number of turns of the fourth coil, and the number of crossings is the number of turns of the third coil and the number of turns of the third coil. It is particularly preferred to be equal to the sum of the number of turns of the coil. According to these, it becomes possible to connect the third and fourth coils and the terminal electrodes more easily.

  In addition, the inductance element according to the present invention preferably further includes a separation unit that separates the third coil and the fourth coil in the intersection region between the third coil and the fourth coil. By using such a separation means, short circuit failure or disconnection due to contact between coils does not occur, and the reliability of the product can be improved.

  In this case, the separating means may be constituted by unevenness provided in the second region of the core part, and is an insulator provided between the third coil and the fourth coil. It doesn't matter. In the case where the separating means is constituted by the unevenness of the core part, the unevenness includes a first portion for allowing the third coil to pass over the fourth coil while being separated, and the fourth coil is the third coil. It is particularly preferable that the second portion is included so as to pass while being spaced apart. According to this, the lengths of the third coil and the fourth coil can be made equal, and the influence of the core portion on the third and fourth coils can be made equal. Thereby, since the symmetry of the 3rd coil and the 4th coil becomes higher, it becomes possible to improve signal quality.

  Thus, the signal transmission circuit according to the present invention can suppress a decrease in characteristic impedance even when a capacitive element is used as an ESD countermeasure. In addition, the inductance element inserted into the signal transmission circuit is formed by integrating the first and second coils whose winding directions are the same with each other and the third and fourth coils whose winding directions are opposite to each other. Therefore, the number of parts can be greatly reduced. In addition, since the winding directions of the third and fourth coils are opposite to each other, a sufficient inductance value can be ensured with a smaller number of turns. For this reason, it is possible to suppress a decrease in characteristic impedance due to the capacitive element by a smaller inductance element.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  (First embodiment of signal transmission circuit)

  First, based on FIG.1 and FIG.2, the structure of the signal transmission circuit which concerns on 1st Embodiment is demonstrated. FIG. 1 is a schematic diagram illustrating a signal transmission circuit according to the first embodiment. FIG. 2 is a circuit diagram showing the signal transmission circuit according to the first embodiment.

  As shown in FIG. 1, the digital television 1 and the DVD player 2 are connected by an HDMI cable 3. The HDMI cable 3 is a cable using a differential transmission method, and includes connection terminal portions 5 and 6 (connectors). The connection terminal portion 5 of the HDMI cable 3 is connected to the output portion of the DVD player 2. The connection terminal portion 6 of the HDMI cable 3 is connected to the input portion of the digital television 1. The digital signal output from the DVD player 2 is transmitted at high speed to the digital television 1 through the HDMI cable 3.

  The digital television 1 has a signal transmission circuit SC1 at its input. As shown in FIG. 2, the signal transmission circuit SC1 includes a common mode filter 10 having first and second inductors 11 and 12 magnetically coupled to each other, and a third and fourth inductor 21 magnetically coupled to each other. , 22 and an inductance element 100 integrated with each other, and first and second varistors 31, 32. The input terminals 13 and 15 of the inductance element 100 are connected to corresponding terminals of the connection terminal portion 6 via the signal lines 91 and 92 when the connection terminal portion 6 of the HDMI cable 3 is connected to the input portion of the digital television 1. Will be connected.

  Here, the structure and operation of the common mode filter 10 will be described with reference to FIGS. 3A and 3B are schematic diagrams for explaining the operation of the common mode filter.

  The common mode filter 10 has a configuration in which two conductive wires (coils) 17 and 18 insulated from each other are wound around a ferrite core 19 a plurality of times in the same direction. The conducting wire 17 constitutes the first inductor 11, and the conducting wire 18 constitutes the second inductor 12. The shape of the ferrite core 19 shown in FIG. 3 is a schematic shape for explaining the operation of the common mode filter 10, and is not the ring shape shown in the present embodiment. The actual specific structure will be described later.

  In the present embodiment, the common mode filter 10 is used in a differential mode for signals. In the differential mode, as shown in FIG. 3A, the signal SI is input to the conducting wires 17 and 18 as signals in opposite directions. Therefore, the magnetic fluxes F1 and F2 generated in the ferrite core 19 by the conductive wires 17 and 18 become magnetic fluxes in opposite directions, and act so as to cancel each other. Accordingly, since there is almost no impedance (inductance) caused by the magnetic field MF generated by the conducting wires 17 and 18, the signal SI is output with almost no attenuation.

  On the other hand, for the common mode noise CN, the common mode filter 10 is used in the common mode. In the common mode, as shown in FIG. 3B, common mode noise CN occurs in the same direction of the conducting wires 17 and 18. Therefore, the magnetic fluxes F1 and F2 generated in the ferrite core 19 by the conductive wires 17 and 18 become magnetic fluxes in the same direction, and act to strengthen each other. Therefore, the impedance (inductance) generated by the magnetic field MF generated by the conducting wires 17 and 18 is increased, and the common mode noise CN is hardly output. In this way, the common mode filter 10 can attenuate noise.

  Reference is again made to FIG. As described above, the inductance unit 20 includes the third and fourth inductors 21 and 22, and the third inductor 21 is connected in series to the first inductor 11 included in the common mode filter 10, and The inductor 22 is connected in series to the second inductor 12 included in the common mode filter 10. Similar to the common mode filter 10 described above, the inductance section 20 has a configuration in which two inductors 21 and 22 that are insulated from each other are wound around a ferrite core a plurality of times, whereby the third and fourth inductors are formed. 21 and 22 are magnetically coupled to each other. However, unlike the common mode filter 10, the inductance part 20 is configured such that the winding directions of two conductive wires (coils) constituting two inductors are opposite to each other. For this reason, the inductance part 20 becomes a common mode with respect to a signal, and becomes a differential mode with respect to common mode noise.

  The first varistor 31 has input / output terminals 33 and 34. The input terminal 33 of the first varistor 31 is connected to the output terminal 24 of the inductance element 100 through a signal line 93. The output terminal 34 of the first varistor 31 is connected to the ground potential. As a result, the first varistor 31 is positioned after the first inductor 11 and the third inductor 21 and is electrically connected in parallel to the first inductor 11 and the third inductor 21. . In addition, the third inductor 21 is located between the first inductor 11 and the first varistor 31.

  The second varistor 32 has input / output terminals 35 and 36. The input terminal 35 of the second varistor 32 is connected to the output terminal 26 of the inductance element 100 through a signal line 94. The output terminal 36 of the second varistor 32 is connected to the ground potential. Thus, the second varistor 32 is positioned after the second inductor 12 and the fourth inductor 22 and is electrically connected in parallel to the second inductor 12 and the fourth inductor 22. . In addition, the fourth inductor 22 is located between the second inductor 12 and the second varistor 32.

  As described above, in the first embodiment, the common mode filter 10 (first and second inductors 11 and 12) is inserted in front of the first and second varistors 31 and 32, and the common mode filter 10. And the first and second varistors 31 and 32, the third and fourth inductors 21 and 22 constituting the inductance section 20 are inserted, respectively, so that the first and second varistors 31 and 32 are inserted. A decrease in characteristic impedance due to can be suppressed.

  In addition, since the inductance element 100 in which the common mode filter 10 and the inductance unit 20 are integrated is used, the size of the signal transmission circuit SC1 can be reduced.

  In addition, the third and fourth inductors 21 and 22 are magnetically coupled to each other, and the winding directions of the two conductors constituting the inductors 21 and 22 are opposite to each other. A sufficient inductance value can be ensured with a smaller number of turns than in the case of no coupling. For this reason, it is possible to reduce the size of the inductance section 20 constituting the third and fourth inductors 21 and 22. Furthermore, since the third and fourth inductors 21 and 22 are not separate components but part of one component that is magnetically coupled, the inductance value can be accurately balanced. It becomes possible to maintain the symmetry of the signal.

  In the first embodiment, since the common mode filter 10 is inserted in front of the first and second varistors 31 and 32, the signal output from the DVD player 2 is hardly accompanied by external noise. , And input to the digital television 1 through the HDMI cable 3 and the signal transmission circuit SC1.

  Next, a specific configuration of the inductance element 100 will be described.

  (First Embodiment of Inductance Element)

  FIG. 4 is a schematic perspective view showing the structure of the inductance element 100 according to the first embodiment. FIG. 5A is a top view of the inductance element 100, and FIG. 5B is a side view of the inductance element 100.

  As shown in FIGS. 4 and 5, the inductance element 100 according to the present embodiment includes a drum core 110 and first to fourth coils 121 to 124. The drum core 110 includes a rod-shaped core portion 130 and first and second flange portions 141 and 142 provided at both ends thereof. First and second terminal electrodes 151 and 152 are formed on the first flange 141, and third and fourth terminal electrodes 153 and 154 are formed on the second flange 142. In an actual use state, the first and second terminal electrodes 151 and 152 are used as the pair of input terminals 13 and 15 shown in FIG. 2, and the third and fourth terminal electrodes 153 and 154 are 2 is used as a pair of output terminals 24 and 26 shown in FIG. The material of the drum core 110 is not particularly limited, but it is preferable to use a material having high magnetic permeability, such as ferrite.

  The first to fourth coils 121 to 124 are wiring members obtained by coating the periphery of a conductor such as copper (Cu) with an insulator, and are all wound around the core portion 130 of the drum core 110. Further, the first and second coils 121 and 122 are coils constituting the first and second inductors 11 and 12 shown in FIG. 2, respectively, and the third and fourth coils 123 and 124 are respectively It is a coil which comprises the 3rd and 4th inductors 21 and 22 shown in FIG.

  More specifically, the first and second coils 121 and 122 are wound around the first region 130a of the core portion 130, and the third and fourth coils 123 and 124 are wound around the core. It is wound around the second region 130b of the part 130. As shown in FIGS. 4 and 5, the first region 130 a of the core portion 130 is located on the first flange portion 141 side (the left side of the paper surface in FIG. 1) when viewed from a predetermined portion of the core portion 130. On the other hand, the second region 130b of the core portion 130 is a region located on the second flange 142 side (right side in FIG. 1) when viewed from the predetermined portion.

  In the present embodiment, the first coil 121 and the third coil 123 are constituted by one continuous conductor, and the second coil 122 and the fourth coil 124 are constituted by one continuous conductor. Has been. Therefore, of these two conductors, the portion wound around the first region 130a of the core portion 130 is called the first and second coils 121 and 122, and the second region of the core portion 130 is called the second region. The portion wound around 130b is simply called the third and fourth coils 123 and 124. However, in this specification, for the sake of convenience, the first to fourth coils 121 to 124 will be described separately.

  The first to fourth coils 121 to 124 have one ends 121a to 124a connected to the first to fourth terminal electrodes 151 to 154, respectively. The other end 121 b of the first coil 121 and the other end 123 b of the third coil 123 are boundaries between the first coil 121 and the third coil 123. Similarly, the other end 122 b of the second coil 122 and the other end 124 b of the fourth coil 124 are boundaries between the second coil 122 and the fourth coil 124.

  Further, when viewed from the arrow A shown in FIG. 4, the first and second coils 121 and 122 are both wound counterclockwise (counterclockwise) from the one end 121a and 122a toward the other end 121b and 122b. Has been. In other words, the winding direction of the first coil 121 starting from the first terminal electrode 151 and the winding direction of the second coil 121 starting from the second terminal electrode 152 are the same direction. is there.

  Note that the winding directions of the first and second coils 121 and 122 are not particularly limited as long as they are the same as each other. Therefore, both may be clockwise (clockwise). In the present embodiment, the first and second coils 121 and 122 are wound around the core portion 130 four times by bifilar. Of course, in the present invention, the number of turns of the first and second coils 121 and 122 is not limited to this, and may be any number of turns. However, in order to maintain the symmetry of the first and second coils 121 and 122, the number of turns of the first coil 121 and the number of turns of the second coil 122 need to be the same.

  On the other hand, when viewed from the arrow A shown in FIG. 4, the third coil 123 is wound counterclockwise (counterclockwise) from the one end 123a to the other end 123b, while the fourth coil 124 is wound. Is wound clockwise (clockwise) from one end 124a to the other end 124b. In other words, the winding direction of the third coil 123 starting from the third terminal electrode 153 and the winding direction of the fourth coil 124 starting from the fourth terminal electrode 154 are opposite to each other. is there.

  The winding directions of the third and fourth coils 123 and 124 are not particularly limited as long as they are opposite to each other. Therefore, the directions are opposite to those described above, that is, the third coil rotates clockwise ( (Clockwise) and the fourth coil may be counterclockwise (counterclockwise). Further, the relationship between the winding direction of the first and second coils 121 and 122 and the winding direction of the third or fourth coils 123 and 124 is not particularly limited.

  In the present embodiment, every time the third and fourth coils 123 and 124 make one round of the core part 130, the third and fourth coils 123 and 124 intersect once on the upper surface 131 of the core part 130. At the same time, the third and fourth coils 123 and 124 intersect once on the lower surface 132 of the core portion 130. In the present embodiment, since the number of turns of the third coil 123 and the number of turns of the fourth coil 124 are both four, the total number of crossings between the third coil 123 and the fourth coil 124 is 8 in total. Times. That is, the number of intersections is equal to the sum of the number of turns of the third coil 123 (four times) and the number of turns of the fourth coil 124 (four times). According to such a winding method, the third and fourth coils 123 and 124 are uniformly wound, so that high symmetry can be ensured.

  Of course, in the present invention, the number of turns of the third and fourth coils 123 and 124 is not limited to this and may be any number. However, in order to maintain the symmetry of the third and fourth coils 123 and 124, the number of turns of the third coil 123 and the number of turns of the fourth coil 124 need to be the same. In order to prevent the signal from being excessively attenuated, the number of turns of the third and fourth coils 123 and 124 may be sufficiently smaller than the number of turns of the first and second coils 121 and 122. However, in this specification and the drawings, for convenience, each coil has four turns.

  FIG. 6 is a diagram for explaining a wiring pattern on a substrate on which the inductance element 100 is mounted.

  Although the inductance element 100 according to the present embodiment includes the third and fourth coils 123 and 124 whose winding directions are opposite to each other, the two terminals used as the pair of input terminals 13 and 15 are used. Two terminal electrodes (third and fourth terminal electrodes 153 and 154), which are formed on the same flange portion, and used as a pair of output terminals 24 and 26, are electrodes (first and second terminal electrodes 151 and 152). ) Are formed on the same flange, as shown in FIG. 6, the pair of signal lines 91 and 92 can be laid in parallel on the substrate 190, and the pair of signal lines 93 and 94 are parallel to each other. Can be laid. This eliminates the need for bypassing the wiring pattern on the substrate 190. Therefore, the occupied area of the wiring pattern on the substrate 190 does not increase more than necessary, and high symmetry can be ensured. As a result, it is possible to simultaneously reduce the size of the entire apparatus and improve the signal quality.

  In addition, the inductance element 100 according to the present embodiment can reduce the number of parts because the first to fourth coils are not separate parts, but the paired coils are each one part magnetically coupled. It becomes possible.

  The above is the specific configuration of the inductance element 100 according to the first embodiment.

  Next, a configuration of a modification of the signal transmission circuit SC1 according to the first embodiment will be described with reference to FIGS. 7 to 9 are diagrams illustrating modifications of the signal transmission circuit according to the first embodiment.

  In the modification shown in FIG. 7, the HDMI cable 3 includes a signal transmission circuit SC1.

  In the modification shown in FIG. 8, the DVD player 2 has a signal transmission circuit SC1 at its output.

  In the modification shown in FIG. 9, the connection terminal portion 6 (connector) of the HDMI cable 3 includes a signal transmission circuit SC1. Instead of the connection terminal portion 6 of the HDMI cable 3 including the signal transmission circuit SC1, the connection terminal portion 5 (connector) of the HDMI cable 3 may include the signal transmission circuit SC1.

  In any of the modifications shown in FIGS. 7 to 9, it is possible to suppress a decrease in characteristic impedance due to the first and second varistors 31 and 32.

  (Second Embodiment of Inductance Element)

  FIG. 10 is a schematic perspective view showing the structure of the inductance element 60 according to the second embodiment. FIG. 11A is a top view showing the main part of the inductance element 60, and FIG. 11B is a bottom view showing the main part of the inductance element 60. Further, FIG. 12A is a cross-sectional view taken along line A1-A1 in FIG. 11A, and FIG. 12B is a cross-sectional view taken along line B1-B1 in FIG. Since the inductance element 60 according to the present embodiment is the same as the inductance element 100 according to the first embodiment in the configuration of the winding core portion 130 on the first region 130a side, it is the same in FIGS. 11A and 11B. The part is omitted.

  As shown in FIGS. 10 to 12, in the inductance element 60 according to the present embodiment, the third flange portion 143 is provided between the first region 130 a and the second region 130 b of the core portion 130. The third flange 143 is provided with fifth and sixth terminal electrodes 155 and 156. The fifth and sixth terminal electrodes 155 and 156 are formed for the purpose of increasing the degree of freedom in circuit design by using them as relay terminals.

  In the present embodiment, the first coil 121 and the third coil 123 are not a single conductor, and the other ends 121b and 123a of the first and third coils 121 and 123 are both the fifth terminal electrodes. It has the structure connected to. Similarly, the second coil 122 and the fourth coil 124 are not one conductor, and the other ends 122b and 124a of the second and fourth coils 122 and 124 are both connected to the sixth terminal electrode. It has a configuration.

Furthermore, in the present embodiment, in the second region 130b of the core portion 130, four groove portions 131a _{1 to} 131a ₄ (these are collectively referred to as groove portions 131a) are formed on the upper surface 131, and four grooves are formed on the lower surface 132. Groove portions 132a _{1 to} 132a ₄ (collectively referred to as groove portions 132a) are formed. A third coil 123 is accommodated in the grooves 131a and 132a. As a result, the fourth coil 124 passes over the third coil 123 while being separated from each other in the crossing region X1 on the upper surface side and the crossing region X2 on the lower surface side. Since the other points are the same as those of the inductance element 100 according to the above-described embodiment, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 12B, the depth D1 of the grooves 131a and 132a is set to be at least equal to or larger than the diameter D2 of the third coil 123. As a result, in the intersecting regions X1 and X2, the third coil 123 and the fourth coil 124 are separated by a distance D3 (= D1-D2).

  As described above, the inductance element 60 according to the present embodiment accommodates the third coil 123 in the groove portions 131a and 132a formed in the second region 130b of the core portion 130, so that the first coil in the intersecting regions X1 and X2 is obtained. Since the contact between the third coil 123 and the fourth coil 124 is prevented, short circuit failure or disconnection due to the contact between the coils does not occur, and the reliability of the product can be improved. . The coil accommodated in the grooves 131a and 132a is not limited to the third coil 123, and may be the fourth coil 124.

  Furthermore, since the inductance element 60 according to the present embodiment includes the fifth and sixth terminal electrodes 155 and 156 serving as relay terminals, various connections are possible, and the degree of freedom in circuit design can be increased. It becomes.

  13 and 14 are process diagrams for explaining a method for manufacturing the inductance element 60.

  First, as shown in FIG. 13, a drum core 110 on which first to sixth terminal electrodes 151 to 156 are formed is prepared. In the second region 130b of the core part 130 of the drum core 110, the above-described grooves 131a and 132a are formed in advance.

  Next, the first coil 121 and the second coil 122 are wound around the first region 130a of the core portion 130 in a state where the first coil 121 and the second coil 122 are aligned in parallel. That is, so-called bifilar winding is performed. The one end 121a and the other end 121b of the first coil 121 are connected to the first and fifth terminal electrodes 151 and 155, respectively, and the one end 122a and the other end 122b of the second coil 122 are respectively connected to the first and second terminal electrodes 151 and 155. The second and sixth terminal electrodes 152 and 156 are connected.

  Next, as shown in FIG. 14, the third coil 122 is wound around the second region of the core 130 along the grooves 131 a and 132 a. Then, one end 123 a of the third coil 123 is connected to the third terminal electrode 153, and the other end 123 b is connected to the fifth terminal electrode 155.

  Then, as shown in FIG. 10, the fourth coil 124 is wound around the second region 130 b of the core part 130 while intersecting with the third coil 123. If one end 124a of the fourth coil 124 is connected to the fourth terminal electrode 154 and the other end 124b is connected to the sixth terminal electrode 156, the inductance element 60 according to the present embodiment is completed. As described above, the inductance element 60 according to the present embodiment winds the fourth coil 124 around the core portion 130 after winding the third coil 123 around the second region 130 b of the core portion 130. Therefore, it is possible to easily assemble with high work efficiency.

  (Third embodiment of inductance element)

  FIGS. 15A and 15B are a top view and a bottom view, respectively, showing the main part of the inductance element 70 according to the third embodiment. 16A is a cross-sectional view taken along line A2-A2 in FIG. 15A, and FIG. 16B is a cross-sectional view taken along line B2-B2 in FIG. A perspective view of the inductance element 70 according to the third embodiment viewed obliquely from above is the same as FIG. Further, since the inductance element 70 according to the present embodiment is the same as the inductance element 100 according to the first embodiment in the configuration on the first region 130a side of the winding core portion 130, in FIGS. The same part is omitted.

  As shown in FIGS. 15 and 16, the inductance element 70 according to the present embodiment has a groove 131 a formed on the upper surface 131 of the second region 130 b of the core 130 and a groove 132 a formed on the lower surface 132. The third embodiment is similar to the inductance element 60 according to the second embodiment described above, except that the third coil 123 is accommodated in the groove 131a and the fourth coil 124 is accommodated in the groove 131b. Different from the element 60. Since the other points are the same as those of the inductance element 60, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  With such a configuration, in the crossing region X3 on the upper surface 131 side of the core portion 130, the fourth coil 124 passes over the third coil 123 while being separated, and the crossing on the lower surface 132 side of the core portion 130 is performed. In the region X4, the third coil 123 passes over the fourth coil 124 while being separated. For this reason, in the present embodiment, not only the contact between the third coil 123 and the fourth coil 124 in the intersecting regions X3 and X4 is prevented, but also the lengths of the third coil 123 and the fourth coil 124. Can be made equal, and the influence of the winding core portion 130 on the third and fourth coils 123 and 124 can be made equal. For this reason, according to this embodiment, since the symmetry of the 3rd coil 123 and the 4th coil 124 becomes higher, it becomes possible to improve signal quality.

  FIG. 17 is a process diagram for explaining a method of manufacturing the inductance element 70.

  First, as shown in FIG. 13, a drum core 110 in which first to sixth terminal electrodes 151 to 156 are formed is prepared, and the first and second coils 121 and 122 are connected to the first core portion 130. The bifilar is wound around the first area 130a. The one end 121a and the other end 121b of the first coil 121 are connected to the first and fifth terminal electrodes 151 and 155, respectively, and the one end 122a and the other end 122b of the second coil 122 are respectively connected to the first and second terminal electrodes 151 and 155. The second and sixth terminal electrodes 152 and 156 are connected. Next, as shown in FIG. 17, the other end 123 b of the third coil 123 is connected to the fifth terminal electrode 155, and the other end 124 b of the fourth coil 124 is connected to the sixth terminal electrode 156.

From this state, after winding the third coil 123 around the second region 130b of the core part 130 along the _first groove 131a ₁ closest to the third flange 143, the third flange 143 is wound. The fourth coil 124 is wound around the second region 130b of the core 130 along the _first groove 132a ₁ (not shown in FIG. Subsequently, the third coil 123 is wound along the _second groove portion 131a ₂ , and further, the fourth coil 124 is wound along the second groove portion 132a ₂ (not shown because of the back surface in FIG. 17). To do. In this way, the third coil 123 and the fourth coil 124 are alternately wound around the second region 130b of the core portion 130. Then, as shown in FIG. 10, one end 123 a of the third coil 123 is connected to the third terminal electrode 153, and further, one end 124 a of the fourth coil 124 is connected to the fourth terminal electrode 154.

  Thus, the inductance element 70 according to the present embodiment is completed. Note that the winding method of the third and fourth coils 123 and 124 in the inductance element 70 is not limited to the method of alternately winding as described above, and one coil (for example, the third coil 123) is connected. After winding all around the second region 130b of the core part 130, the other coil (for example, the fourth coil 124) is wound around the core part 130 so as to pass through the corresponding groove part (for example, the groove part 132b). You can turn it.

  (Fourth Embodiment of Inductance Element)

  FIG. 18 is a schematic perspective view showing the structure of the inductance element 80 according to the fourth embodiment. FIGS. 19A and 19B are a top view and a bottom view showing the main part of the inductance element 80, respectively. Further, FIG. 20 is a cross-sectional view taken along line B3-B3 in FIG. In addition, since the inductance element 80 according to the present embodiment is the same as the inductance element 100 according to the first embodiment in the configuration on the first region 130a side of the winding core portion 130, in FIGS. The same part is omitted.

As shown in FIGS. 18 to 20, in the inductance element 80 according to the present embodiment, four protrusions 131 b _{1 to} 131 b ₄ (collectively these protrusions 131 b are formed on the upper surface 131 of the second region 130 b of the core part 130. And four protrusions 132b _{1 to} 132b ₄ (collectively referred to as protrusions 132b) are formed on the lower surface 132. The protrusions 131b and 132b may be a part of the core part 130, or may be another member added to the core part 130.

  On the upper surface 131 side of the second region 130b of the core portion 130, the fourth coil 124 is wound so as to be in contact with the upper surface of the protruding portion 131b. The third coil 123 is wound around the fourth coil 124 so as to avoid the protrusion 131b. On the contrary, on the lower surface 132 side of the second region 130b of the core part 130, the third coil 123 is wound so as to be in contact with the upper surface of the protrusion part 132b. The fourth coil 124 is wound around the gap between the lower surface 132 and the third coil 123 while avoiding the protrusion 132b. Since the other points are the same as those of the inductance element 100 according to the above-described embodiment, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 20, the heights D4 of the protrusions 131b and 132b are set to be at least the diameter D2 of the third and fourth coils 123 and 124. That is, in the intersecting regions X5 and X6, a gap of a distance D4 is generated at the maximum between the third or fourth coil 123, 124 and the flat surface of the core part 130. If the fourth coils 123 and 124 are passed, the third coil 123 and the fourth coil 124 can be separated by a distance D5 (= D4-D2) at the maximum.

  With such a configuration, in the intersection region X5 on the upper surface 131 side of the core portion 130, the fourth coil 124 passes over the third coil 123 while being separated, and the intersection on the lower surface 132 side of the core portion 130 is achieved. In the region X6, the third coil 123 passes over the fourth coil 124 while being separated. For this reason, also in the present embodiment, short circuit failure or disconnection due to contact between the coils does not occur, and the reliability of the product can be improved.

  Furthermore, the inductance element 80 according to the present embodiment can make the lengths of the third coil 123 and the fourth coil 124 equal to each other and the third and fourth coils, similarly to the inductance element 70 according to the third embodiment. The influence of the core part 130 on the coils 123 and 124 can be made uniform. Therefore, the signal quality can be improved as in the inductance element 70 according to the third embodiment.

  However, when the protrusion is used, it is not essential to employ the above-described configuration, and the third coil 123 (or the fourth coil 124) is provided on both the upper surface 131 and the lower surface 132 of the core portion 130. You may wind so that it may touch the upper surface of protrusion part 131b, 132b.

  The shape of the protrusion is not particularly limited, but in order to prevent the coil wound on the protrusion from falling off and to increase the work efficiency of the winding operation, it is shown in FIG. Thus, it is preferable to provide a recess 131x on the upper surface of each protrusion 131b, 132b, or to provide a guide 131y on the upper surface of each protrusion 131b, 132b as shown in FIG.

  In the second and third embodiments, the core portion 130 is provided with a groove portion, and in the fourth embodiment, the core portion 130 is provided with a protruding portion, whereby the third and fourth coils 123 and 124 in the intersecting region are provided. Although the contact is prevented, in short, any shape may be adopted as long as the third and fourth coils 123 and 124 can be separated by the unevenness provided in the core portion 130. In addition, the distinction between a concave portion and a convex portion is only relative. Therefore, in the second and third embodiments, a region where the groove is not formed can be regarded as a convex portion, and in the fourth embodiment, a region where the protrusion is not formed can be regarded as a concave portion. it can.

  Furthermore, as shown in FIG. 22 which is a front view and a side view, when the cross section of the core portion 130 is a hexagon, a plurality of slits 138a and 139a are formed in the opposite corner portions 138 and 139, respectively. If it puts in, the effect similar to 2nd-4th embodiment can be acquired. That is, as shown in FIG. 23 which is a top view, if the third coil 123 is wound along the slit 138a and the fourth coil 124 is wound so as to straddle the slit 138a, two coils are wound. Can be separated. Similarly, the fourth coil 124 may be wound along the slit 139a on the opposite side of the surface shown in FIG. 23, and the third coil 123 may be wound so as to straddle the slit 139a.

  (Fifth Embodiment of Inductance Element)

  FIG. 24 is a schematic perspective view showing the structure of the inductance element 90 according to the fifth embodiment.

  As shown in FIG. 24, the inductance element 90 according to the present embodiment is provided between the third coil 123 and the fourth coil 124 on the upper surface 131 side of the second region 130b of the core portion 130. An insulating film 131 c is added, and an insulating film 132 c provided between the third coil 123 and the fourth coil 124 is added to the lower surface 132 side of the core portion 130. Since the other points are the same as those of the inductance element 100 according to the first embodiment, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  In the inductance element 90 according to the present embodiment, the third and fourth coils 123 and 124 are not separated by the projections and depressions provided on the core portion 130, but are separated by the insulating films 131 c and 132 c. Also by such a method, it is possible to prevent short-circuit failure or disconnection due to contact between coils, so that the reliability of the product can be improved. The material of the insulating films 131c and 132c is not particularly limited, but it is preferable to select a material that is thin and difficult to break.

  25 and 26 are process diagrams for explaining a method of manufacturing the inductance element 90. FIG.

  First, as shown in FIG. 25, a drum core 110 in which first to sixth terminal electrodes 151 to 156 are formed is prepared, and the first and second coils 121 and 122 are connected to the first core portion 130. The bifilar is wound around the area 130a. The one end 121a and the other end 121b of the first coil 121 are connected to the first and fifth terminal electrodes 151 and 155, respectively, and the one end 122a and the other end 122b of the second coil 122 are respectively connected to the first and second terminal electrodes 151 and 155. The second and sixth terminal electrodes 152 and 156 are connected.

  Next, as shown in FIG. 25, the third coil 123 is wound around the second region 130b of the core portion 130, one end 123a is connected to the third terminal electrode 153, and the other end 123b is connected to the fifth region 130b. The terminal electrode 155 is connected. Then, as shown in FIG. 26, the third coil 123 located on the upper surface 131 of the core part 130 is covered with an insulating film 131c. Similarly, the third coil 123 located on the lower surface 132 of the core part 130 is covered with the insulating film 132c.

  Then, as shown in FIG. 24, the fourth coil 124 is wound around the core 130 from above the insulating films 131c and 132c, one end 124a is connected to the fourth terminal electrode 154, and the other end 124b is connected. When connected to the sixth terminal electrode 156, the inductance element 90 according to the present embodiment is completed. As described above, the inductance element 90 according to the present embodiment winds the fourth coil 124 around the core portion 130 after winding the third coil 123 around the second region 130 b of the core portion 130. Therefore, it is possible to easily assemble with high work efficiency.

  As mentioned above, although several embodiment regarding an inductance element was described, the inductance element by any embodiment is the common mode filter 10 comprised by the 1st and 2nd coils 121 and 122, and 3rd and 4th. Since the inductance part 20 constituted by the coils 123 and 124 is integrated, it is possible to reduce the number of parts used in the signal transmission circuit.

  Moreover, since the third and fourth coils 123 and 124 are magnetically coupled to each other and the winding directions are opposite to each other, the number of turns is smaller than that in the case where they are not magnetically coupled. A sufficient inductance value can be ensured, and the size of the inductance element can be reduced. Moreover, the inductance elements according to the respective embodiments can balance the inductance values with high accuracy, and can maintain the symmetry of the differential signal. For this reason, if the inductance element according to each embodiment is used, it is possible to simultaneously reduce the size of the entire apparatus and improve the signal quality.

  (Second Embodiment of Signal Transmission Circuit)

  Next, the configuration of the signal transmission circuit according to the second embodiment will be described with reference to FIG. FIG. 27 is a circuit diagram showing a signal transmission circuit according to the second embodiment.

  As in the first embodiment, the digital television 1 includes a signal transmission circuit SC2 at its input section. As shown in FIG. 27, the signal transmission circuit SC2 includes an inductance element 100 in which the common mode filter 10 and the inductance unit 20 are integrated, first and second varistors 31, 32, and fifth and sixth. Inductors 41 and 42 are provided.

  The fifth inductor 41 has input / output terminals 43 and 44. The input terminal 43 of the fifth inductor 41 is connected to the output terminal 24 of the third inductor 21, and is electrically connected in series to the first inductor 11 and the third inductor 21. As a result, the fifth inductor 41 is positioned downstream of the first varistor 31.

  The sixth inductor 42 has input / output terminals 45 and 46. The input terminal 45 of the sixth inductor 42 is connected to the output terminal 26 of the fourth inductor 22, and is electrically connected in series to the second inductor 12 and the fourth inductor 22. As a result, the fifth inductor 42 is positioned downstream of the second varistor 32.

  As described above, in the second embodiment, since the fifth and sixth inductors 41 and 42 are inserted after the first and second varistors 31 and 32, respectively, the first and second varistors are provided. A decrease in characteristic impedance due to 31 and 32 can be further suppressed.

  As shown in FIGS. 7 to 9, the signal transmission circuit SC2 may be provided in the HDMI cable 3, the DVD player 2, or the connection terminal portions 5 and 6 (connectors). Even in this case, a decrease in characteristic impedance due to the first and second varistors 31 and 32 can be further suppressed.

  Subsequently, it will be specifically shown that the first and second embodiments of the signal transmission circuit can suppress a decrease in characteristic impedance caused by the first and second varistors. Here, the characteristic impedance of the signal transmission circuit is measured by a TDR (Time Domain Reflectometry) method. The TDR method is a measurement method for measuring the characteristic impedance of the transmission line by sending a step pulse to the transmission line and measuring the pulse reflected at the discontinuous portion of the characteristic impedance.

  First, the measurement environment by the TDR method will be described with reference to FIG. In each measurement environment shown in FIG. 28, a high-speed oscilloscope 50 and a receiver IC 52 are connected via a transmission line 54. The transmission path 54 includes a coaxial cable 56 and a signal transmission circuit 58. The high-speed oscilloscope 50 has a TDR module 51. The high-speed oscilloscope 50 is connected to the coaxial cable 56 through the TDR module 51, and the other end of the coaxial cable 56 is connected to the signal transmission circuit 58. A receiver IC 52 is connected to the other end of the signal transmission circuit 58.

  As the high-speed oscilloscope 50, an Agilent 86100 broadband oscilloscope manufactured by Agilent Technologies, Inc. is used. As the TDR module 51, a 54754 differential TDR plug-in module manufactured by Agilent Technologies is used. The receiver IC 52 has an infinite input impedance when the power is off, and 100% of the signal from the high-speed oscilloscope 50 is reflected. The coaxial cable 56 is composed of two differential signal lines, each having a characteristic impedance of 50Ω. For this reason, the characteristic impedance of the entire coaxial cable 56 is 100Ω.

  Next, a measurement method by the TDR method will be described based on FIGS. First, the high-speed oscilloscope 50 generates an incident voltage step Ei, and outputs this incident voltage step Ei to the transmission line 54. When there is no discontinuous characteristic impedance on the transmission line 54, the incident voltage step Ei is reflected by the receiver IC 52 as it is, and the high-speed oscilloscope 50 receives the incident voltage step Ei as shown in FIG. Only displayed. On the other hand, when a discontinuous portion exists in the characteristic impedance of the transmission line 54, a part of the incident voltage step is reflected at the discontinuous portion. In this case, as shown in FIG. 29B, the reflected wave Er is algebraically added to the incident voltage step Ei and displayed on the high-speed oscilloscope 50. From this result, the position of the characteristic impedance discontinuity and the value of the characteristic impedance can be obtained. That is, the position of the discontinuous part of the characteristic impedance can be obtained from the time T until the reflected wave Er is measured, and the characteristic impedance at the discontinuous part can be obtained from the value of the reflected wave Er.

  ACM2012D-900 (manufactured by TDK Corporation) was used as the common mode filter. The characteristic impedance of ACM2012D-900 is 100Ω. The cutoff frequency of ACM2012D-900 is 3.5 GHz. As the first and second varistors, AVR161A1R1 (manufactured by TDK Corporation) was used. The capacitance of AVR161A1R1 is 1.1 pF. The MLK1005 series (manufactured by TDK Corporation) was used for the third to sixth inductors.

  The measurement results are shown in FIGS.

  Refer to FIG. The characteristic I1 is a measurement result when the signal transmission circuit 58 includes the first and second varistors and does not include the common mode filter and the third to sixth inductors. As can be seen from the characteristic I1, the characteristic impedance is reduced under the influence of the first and second varistors, and impedance mismatch occurs.

  The characteristic I2 is a measurement result when the signal transmission circuit 58 includes the first and second varistors and the common mode filter, and does not include the third to sixth inductors. In configuring the signal transmission circuit 58, the distance on the transmission line between the output terminal of the common mode filter and the input terminals of the first and second varistors, that is, the output terminal of the common mode filter and the first and second varistors. The time length with respect to the input terminal was set to 23 ps.

  As can be seen from the characteristic I2, the characteristic impedance of the signal transmission circuit 58 is in the range of 100Ω ± 15%, but the characteristic impedance is still lowered due to the influence of the first and second varistors.

  Characteristics I3 to I5 indicate that the signal transmission circuit 58 includes the first and second varistors, the common mode filter, and the third and fourth inductors, that is, the signal transmission circuit 58 according to the first embodiment described above. It is a measurement result in the case of having the same configuration as the transmission circuit SC1. The characteristic I3 is a measurement result when the inductance values of the third and fourth inductors are 1.0 nH. Characteristic I4 is a measurement result when the inductance values of the third and fourth inductors are 1.5 nH. Characteristic I5 is a measurement result when the inductance values of the third and fourth inductors are set to 2.2 nH. In configuring the signal transmission circuit 58, the interval on the transmission line between the output terminal of the common mode filter and the input terminals of the third and fourth inductors, that is, the output terminal of the common mode filter and the third and fourth inductors. The time length with respect to the input terminal was set to 20 ps. Similarly, the distance on the transmission line between the output terminals of the third and fourth inductors and the input terminals of the first and second varistors, that is, the output terminals of the third and fourth inductors and the first and second output terminals. The time length between the varistor input terminals was set to 0 ps.

  As can be seen from the characteristics I3 to I5, a decrease in characteristic impedance due to the influence of the first and second varistors is suppressed.

  As can be seen from the characteristic I5, when the inductance values of the third and fourth inductors are set to 2.2 nH, the characteristic impedance is reduced at the positions of the first and second varistors, but at other places. The characteristic impedance becomes high. The occurrence of the portion where the characteristic impedance becomes high in this way is considered to be caused by the inductance values of the third and fourth inductors. Therefore, the inductance values of the third and fourth inductors are preferably 1 to 2 nH.

  Reference is now made to FIG. Characteristic I6 and characteristic I7 indicate that the signal transmission circuit 58 includes the first and second varistors, the common mode filter, and the third to sixth inductors, that is, the signal transmission circuit 58 according to the second embodiment described above. It is a measurement result in the case of the same configuration as the signal transmission circuit SC2. Characteristic I6 is a measurement result when the inductance values of the third to sixth inductors are set to 1.0 nH. Characteristic I7 is a measurement result when the inductance values of the third and fourth inductors are set to 1.0 nH and the fifth and sixth inductors are bypassed. In configuring the signal transmission circuit 58, the interval on the transmission line between the output terminal of the common mode filter and the input terminals of the third and fourth inductors, that is, the output terminal of the common mode filter and the third and fourth inductors. The time length with respect to the input terminal was set to 0 ps. Similarly, the distance on the transmission line between the output terminals of the third and fourth inductors and the input terminals of the first and second varistors, that is, the output terminals of the third and fourth inductors and the first and second output terminals. The time length between the varistor input terminals was set to 0 ps. Similarly, the distance between the input terminals of the first and second varistors and the input terminals of the fifth and sixth inductors on the transmission line, that is, the input terminals of the first and second varistors and the fifth and sixth varistors. The time length between the inductor input terminals was set to 0 ps.

  As can be seen from the characteristic I6, a decrease in characteristic impedance due to the influence of the first and second varistors is further suppressed.

  Reference is now made to FIG. The characteristics I8 to I10 indicate that the signal transmission circuit 58 includes the first and second varistors, the common mode filter, and the third to sixth inductors, that is, the signal transmission circuit 58 according to the second embodiment described above. It is a measurement result in the case of the same configuration as the transmission circuit SC2. Characteristic I8 is a measurement result when the inductance values of the third and fourth inductors are 1.5 nH and the inductance values of the fifth and sixth inductors are 1.0 nH. It is a measurement result in the case of. Characteristic I9 is a measurement result when the inductance values of the third to sixth inductors are 1.5 nH. The characteristic I10 is a measurement result when the inductance values of the third and fourth inductors are 1.5 nH and the fifth and sixth inductors are bypassed. In configuring the signal transmission circuit 58, the interval on the transmission line between the output terminal of the common mode filter and the input terminals of the third and fourth inductors, that is, the output terminal of the common mode filter and the third and fourth inductors. The time length with respect to the input terminal was set to 0 ps. Similarly, the distance on the transmission line between the output terminals of the third and fourth inductors and the input terminals of the first and second varistors, that is, the output terminals of the third and fourth inductors and the first and second output terminals. The time length between the varistor input terminals was set to 0 ps. Similarly, the distance between the input terminals of the first and second varistors and the input terminals of the fifth and sixth inductors on the transmission line, that is, the input terminals of the first and second varistors and the fifth and sixth varistors. The time length between the inductor input terminals was set to 0 ps.

  As can be seen from the characteristics I8 and I9, a decrease in characteristic impedance due to the influence of the first and second varistors is further suppressed.

  From the above, the usefulness of the signal transmission circuit according to the first and second embodiments was confirmed.

  As can be seen from the measurement results described above, the inductance values of the third to sixth inductors are preferably smaller than 10 nH, and more preferably 1 to 2 nH. This is because, as described above, a portion where the characteristic impedance increases due to the inductance values of the third to sixth inductors occurs, and impedance matching becomes insufficient.

  The distance on the transmission line between the output terminal of the common mode filter and the input terminals of the third and fourth inductors, and the transmission between the output terminals of the third and fourth inductors and the input terminals of the first and second varistors. The distance on the transmission line and the distance on the transmission line between the input terminals of the first and second varistors and the input terminals of the fifth and sixth inductors are preferably as short as possible. This is because the transmission line between the terminals (for example, the conductor pattern of the substrate) has an inductance component and a capacitance component, and these inductance component and capacitance component are factors that impede impedance matching.

  Note that when a common mode filter is used as a noise filter, a capacitor may be connected between signal lines (see, for example, Patent Document 2). However, when a capacitor is connected between the signal lines in the first and second embodiments of the signal transmission circuit, an unnecessary capacitance component is generated, and impedance matching cannot be achieved. Therefore, the first and second embodiments of the signal transmission circuit do not include a capacitor for connecting the signal lines.

  The preferred embodiments of the present invention have been described above, but the present invention is not necessarily limited to these embodiments. For example, the signal transmission circuits SC <b> 1 and SC <b> 2 are not limited to the positions described above, and may be provided before the first circuit of the digital television 1 after output from the DVD player 2. The DVD player 2 may be another source device such as a personal computer or a set top box. The HDMI cable 3 may be a cable corresponding to a standard such as DVI, USB, or IEEE. The digital television 1 may be another sink device such as an LCD monitor or a projector.

  In the first and second embodiments of the signal transmission circuit, varistors are used as the first and second capacitive elements, but capacitive elements such as Zener diodes may be used as the first and second capacitive elements. Good.

  In addition, in the inductance elements 60, 70, and 80 according to the second to fourth embodiments, the contact between the coils is prevented by the groove and the protrusion provided in the core 130, but the coils are provided in the core. Other shapes can be used as long as the contact between the coils can be prevented by the unevenness.

  Furthermore, in the inductance element 90 according to the fifth embodiment, the insulating films 131c and 132c are used to prevent the coils from contacting each other. However, the member interposed between the coils is limited to a film member as long as it is an insulator. It is not something. Therefore, for example, after winding one coil, it is also possible to prevent the contact between the coils by applying an ultraviolet curable resin or the like and curing it, and then winding the other coil.

  The application range of the inductance elements 100, 60, 70, 80, 90 described as the first to fifth embodiments is not limited to the signal transmission circuits SC1, SC2 described above, and is used for other purposes. can do.

1 is a schematic diagram illustrating a signal transmission circuit according to a first embodiment. 1 is a circuit diagram illustrating a signal transmission circuit according to a first embodiment. FIG. It is a schematic diagram explaining operation | movement of a common mode filter. 1 is a schematic perspective view showing a structure of an inductance element 100 according to a first embodiment. (A) is a top view of the inductance element 100, and (b) is a side view of the inductance element 100. It is a figure for demonstrating the wiring pattern on the board | substrate which mounts the inductance element. It is a schematic diagram which shows the modification of the signal transmission circuit which concerns on 1st Embodiment. It is a schematic diagram which shows the modification of the signal transmission circuit which concerns on 1st Embodiment. It is a schematic diagram which shows the modification of the signal transmission circuit which concerns on 1st Embodiment. It is a schematic perspective view which shows the structure of the inductance elements 60 and 70 by 2nd and 3rd embodiment. (A) is a top view showing the main part of the inductance element 60, and (b) is a bottom view showing the main part of the inductance element 60. (A) is sectional drawing along the A1-A1 line of Fig.11 (a), (b) is sectional drawing along the B1-B1 line of FIG.11 (b). 6 is a process diagram for explaining a method of manufacturing the inductance element 60. FIG. 6 is a process diagram for explaining a method of manufacturing the inductance element 60. FIG. (A) is a top view which shows the principal part of the inductance element 70 by 3rd Embodiment, (b) is a bottom view which shows the principal part of the inductance element 70 by 3rd Embodiment. (A) is sectional drawing along the A2-A2 line | wire of Fig.15 (a), (b) is sectional drawing along the B2-B2 line | wire of FIG.15 (b). 6 is a process diagram for explaining a method of manufacturing the inductance element 70. FIG. It is a schematic perspective view which shows the structure of the inductance element 80 by 4th Embodiment. (A) is a top view which shows the principal part of the inductance element 80 by 4th Embodiment, (b) is a bottom view which shows the principal part of the inductance element 80 by 4th Embodiment. It is sectional drawing along the B3-B3 line | wire of Fig.19 (a). It is a schematic perspective view which shows the modification of protrusion part 131b, 132b. It is the front view and side view which show the modification of the core part. It is a top view which shows the state which wound the coil around the core part 130 by the modification. It is a schematic perspective view which shows the structure of the inductance element 90 by 5th Embodiment. 6 is a process diagram for explaining a method of manufacturing the inductance element 90. FIG. 6 is a process diagram for explaining a method of manufacturing the inductance element 90. FIG. It is a circuit diagram which shows the signal transmission circuit which concerns on 2nd Embodiment. It is a figure for demonstrating the measurement environment by TDR method. It is a figure for demonstrating the measuring method by TDR method. It is a diagram which shows the measurement result by TDR method. It is a diagram which shows the measurement result by TDR method. It is a diagram which shows the measurement result by TDR method.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Digital television, 2 ... DVD player, 3 ... HDMI cable, 5, 6 ... Connection terminal part, 10 ... Common mode filter, 11 ... 1st inductor, 12 ... 2nd inductor, 21 ... 3rd inductor, 22 ... 4th inductor, 31 ... 1st varistor, 32 ... 2nd varistor, 41 ... 5th inductor, 42 ... 6th inductor, SC1, SC2 ... Signal transmission circuit, 20 ... Inductance part, 60, 70, 80, 90, 100 ... inductance elements, 91-94 ... signal lines, 110 ... drum core, 121 ... first coil, 121a ... one end of the first coil, 121b ... other end of the first coil, 122 ... second coil, 122a ... one end of the second coil, 122b ... the other end of the second coil, 123 ... a third coil, 123a ... one end of the third coil, 1 3b: the other end of the third coil, 124: the fourth coil, 124a: one end of the second coil, 124b: the other end of the fourth coil, 130: the core portion, 130a: the first of the core portion , 130b ... second region of the core, 131 ... upper surface of the core, 132 ... lower surface of the core, 131a, 132a ... groove, 131b, 132b ... projection, 131c, 132c ... insulating film, 131x ... recess, 131y ... guide part, 138, 139 ... corner part, 138a, 139a ... slit, 141 ... first collar part, 142 ... second collar part, 143 ... third collar part, 151 ... first Terminal electrode 152, second terminal electrode, 153, third terminal electrode, 154, fourth terminal electrode, 155, fifth terminal electrode, 156, sixth terminal electrode, 190, substrate

Claims (11)

A drum core having a core part and first and second flanges provided at both ends of the core part;
First and second terminal electrodes formed on the first flange;
Third and fourth terminal electrodes formed on the second flange;
A first coil wound in a first direction from one end to the other end in the first region of the winding core, the one end being connected to the first terminal electrode;
A second coil wound in the same direction as the first direction from one end to the other end in the first region of the winding core, and the one end connected to the second terminal electrode;
In the second region different from the first region of the core, the one end is wound in the second direction from the one end to the other end, the one end is connected to the third terminal electrode, and the other end A third coil connected to the other end of the first coil;
In the second region of the winding core portion, it is wound in a direction different from the second direction from one end to the other end, the one end is connected to the fourth terminal electrode, and the other end is An inductance element comprising: a fourth coil connected to the other end of the second coil.   The inductance element according to claim 1, wherein the first coil and the third coil are continuous conductors, and the second coil and the fourth coil are continuous conductors.   It further comprises fifth and sixth terminal electrodes provided between the first region and the second region of the core portion, and the other end of the first coil is the fifth terminal. The inductance element according to claim 1, wherein the inductance element is connected to an electrode, and the other end of the second coil is connected to the sixth terminal electrode.   The inductance element according to any one of claims 1 to 3, wherein the third coil and the fourth coil intersect at a plurality of locations.   5. The inductance element according to claim 4, wherein the number of crossings between the third coil and the fourth coil is greater than the number of turns of the third coil and the number of turns of the fourth coil.   6. The inductance element according to claim 5, wherein the number of crossings is equal to the sum of the number of turns of the third coil and the number of turns of the fourth coil.   7. The apparatus according to claim 1, further comprising a separation unit that separates the third coil from the fourth coil in an intersection region between the third coil and the fourth coil. The inductance element according to item.   The inductance element according to claim 7, wherein the separation unit is configured by unevenness provided in the second region of the core portion.   The concave and convex portions are a first portion for allowing the third coil to pass over the fourth coil while being spaced apart from each other, and for allowing the fourth coil to pass while being spaced apart from the third coil. The inductance element according to claim 8, further comprising a second portion.   The inductance element according to claim 7, wherein the separation unit is an insulator provided between the third coil and the fourth coil.   A first element connected to the third terminal electrode of the inductance element so as to be parallel to the inductance element according to any one of claims 1 to 10 and the first and third coils. A signal comprising: a capacitive element; and a second capacitive element connected to the fourth terminal electrode of the inductance element so as to be in parallel with the second and fourth coils. Transmission circuit.

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