Patent Application
20200402706
This application claims benefit of priority to Japanese Patent Application No. 2019-116249, filed Jun. 24, 2019, and to Japanese Patent Application No. 2020-016645, filed Feb. 3, 2020, the entire contents of each are incorporated herein by reference.
The present disclosure relates to a winding-type coil component and a direct-current superimposing circuit using the same.
There have been market demands for the superimposition of a direct current on a differential transmission signal line for the transmission of not only data but also power. To meet the demands, in particular, there are automotive communication standards such as Power over Data Lines (PoDL) and Automotive Audio Bus® (A2B). In a typical direct-current superimposing circuit compliant with this kind of communication standard, a direct-current (DC) power supply is connected to a differential transmission signal line for transmitting a differential signal transmitted/received by a differential communication integrated circuit (IC) via an inductor. The inductor is used for alternating-current (AC) cut and prevents an AC signal passing through the signal line from leaking into the DC power supply.
Examples of usage of such an inductor include the case where an independent coil with no magnetic coupling is used on each of the positive and negative sides of a DC power supply, and the case where a pair of coils with magnetic coupling is used. A coil component using the latter coil with magnetic coupling prevents a differential-mode signal from transmitting to a DC power supply using the high impedance thereof and allows common-mode noise to transmit to the DC power supply using the low impedance thereof.
Japanese Unexamined Patent Application Publication No. 8-186034 discloses a winding-type coil component as this kind of coil component.
This winding-type coil component includes a core, two wires (a first wire and a second wire), and two pairs of a first terminal electrode and a second terminal electrode. The core includes a winding core portion and a pair of flange portions formed at both ends of the winding core portion. The two wires, the first wire and the second wire, are wound around the winding core portion of the core in a pair. The first terminal electrode and the second terminal electrode in one of the two pairs are formed apart from each other on one side surface of one of the flange portions of the core, and the first terminal electrode and the second terminal electrode in the other one of the two pairs are formed apart from each other on the opposite side surface of the flange portion. Respective end portions of the first wire are electrically connected to the first terminal electrode and the second terminal electrode formed on the one side surface of the flange portion. Respective end portions of the second wire are electrically connected to the first terminal electrode and the second terminal electrode formed on the opposite side surface of the flange portion.
However, it is known that, when the winding-type coil component disclosed in Japanese Unexamined Patent Application Publication No. 8-186034 is used in a direct-current superimposing circuit, a differential signal passing through a signal line is converted into common-mode noise and unnecessary noise is emitted.
The reason for this is that, in a winding-type coil component 1 illustrated in
In a direct-current superimposing circuit using the winding-type coil component 1 illustrated in
Accordingly, the present disclosure provides a winding-type coil component capable of preventing the occurrence of the above-described problem and suppressing the degradation in signal quality and a direct-current superimposing circuit using the winding-type coil component.
According to preferred embodiments of the present disclosure, there is provided a winding-type coil component including a core including a flange portion having an end surface brought into contact with a mounting surface of a circuit board and a winding core standing in a vertical direction with respect to the end surface, a pair of a first terminal electrode and a second terminal electrode that are placed to face each other across a winding core axis of the winding core on the end surface, and a pair of a third terminal electrode and a fourth terminal electrode that are placed to face each other across the winding core axis of the winding core on the end surface. The winding-type coil component further includes a first winding having one end portion, which is a winding start or a winding end, connected to the first terminal electrode and the other end portion, which is a winding start or a winding end, connected to the second terminal electrode, and a second winding having one end portion, which is a winding start or a winding end, connected to the third terminal electrode and the other end portion, which is a winding start or a winding end, connected to the fourth terminal electrode. The first winding and the second winding are wound around the winding core. The second terminal electrode to which the other end portion of the first winding is connected is connected to one of a pair of differential signal lines. The third terminal electrode to which the one end portion of the second winding is connected is connected to the other one of the pair of differential signal lines.
According to preferred embodiments of the present disclosure, there is also provided a direct-current superimposing circuit including a communication circuit that communicates with an external circuit via a pair of differential signal lines, the above-described winding-type coil component that is connected to the pair of the differential signal lines between the communication circuit and an external connection terminal that connects the pair of the differential signal lines to the external circuit, and a direct-current (DC) power supply that is connected between the first terminal electrode and the fourth terminal electrode in the winding-type coil component and superimposes a direct current on the pair of the differential signal lines. The communication circuit, the winding-type coil component, and the DC power supply are disposed at a circuit board.
With this configuration, the first winding and the second winding are wound around the winding core of the core. The one end portion and the other end portion of the first winding are connected to the terminal electrodes in one of the two pairs of terminal electrode which are placed to face each other across the winding core axis of the winding core on the end surface of the flange portion. The one end portion and the other end portion of the second winding are connected to the terminal electrodes in the other one of the two pairs of terminal electrode which are placed to face each other across the winding core axis of the winding core on the end surface of the flange portion. The numbers of turns of the first winding and the second winding wound around the winding core are the same. The difference between inductances formed by the first winding and the second winding is reduced. The degree of mode conversion in the winding-type coil component therefore decreases, a signal passing through the differential signal lines is unlikely to be converted from a differential-mode signal into common-mode noise, and unnecessary noise caused by the winding-type coil component is unlikely to be emitted.
Other features, elements, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of preferred embodiments of the present disclosure with reference to the attached drawings.
Next, a winding-type coil component according to an embodiment of the present disclosure and a direct-current superimposing circuit using the winding-type coil component will be described.
The direct-current superimposing circuit 21 is provided between a differential communication IC 22 that is a communication circuit for performing bidirectional communication including transmission and reception and a connector 23, includes a pair of differential signal lines 24a and 24b, two capacitors 25, a common mode choke coil 26, the winding-type coil component 27A, and a DC power supply 28, and is disposed on a circuit board (See also, e.g., mounting surface 38 of a circuit board as shown in
Through the pair of the differential signal lines 24a and 24b, a differential signal transmitted from the differential communication IC 22 and a differential signal to be received by the differential communication IC 22 pass. A direct current is superimposed on the differential signal lines 24a and 24b and the cable 29 by the DC power supply 28 and passes therethrough. The two capacitors 25 are provided at the respective differential signal lines 24a and 24b at the input/output ends of the differential communication IC 22 and prevent a direct current superimposed on the differential signal lines 24a and 24b from inputting into the differential communication IC 22. A common mode choke coil 26 is inserted into the differential signal lines 24a and 24b and attenuates common-mode noise passing through the differential signal lines 24a and 24b. Between the DC power supply 28 and the pair of the differential signal lines 24a and 24b on the side of an external circuit from the capacitors 25, the winding-type coil component 27A is connected to the pair of the differential signal lines 24a and 24b between the capacitors 25 and the connector 23. The winding-type coil component 27A prevents a differential signal passing through the differential signal lines 24a and 24b from leaking into the DC power supply 28.
The winding-type coil component 27A includes a core 31, a pair of a first terminal electrode 32a and a second terminal electrode 32b, a pair of a third terminal electrode 33a and a fourth terminal electrode 33b, and two windings (a first winding 34 and a second winding 35). Like in the common mode choke coil 26, in the winding-type coil component 27A, the two windings 34 and 35 are wound to strengthen a magnetic flux that a signal current i flowing through the two windings 34 and 35 in the same direction generates at the core 31. However, the way of the connection of the winding-type coil component 27A to a circuit is different from the way of the connection of the common mode choke coil 26 to a circuit. The winding-type coil component 27A is used as a differential-mode inductor. That is, the winding-type coil component 27A is connected to a circuit such that the signal current i in the differential mode flows through the two windings 34 and 35 in opposite directions and impedance increases with respect to the signal current i in the differential mode.
The core 31 includes a pair of flange portions 31a and 31b and a winding core 31c made of an insulating material such as ferrite or alumina. The flange portion 31a placed below the flange portion 31b has an end surface 31a1 that is brought into contact with the mounting surface of a circuit board, such as mounting surface 38 of a circuit board as shown, for example, in
Each of the terminal electrodes 32a, 32b, 33a, and 33b has a two-layer structure including a base electrode made of, for example, Ag, an Cr—Cu alloy, or a Cr—Ni alloy and an external electrode made of, for example, Sn or an Sn—Pb alloy. An intermediate layer made of, for example, Ni or Cu may be inserted between the base electrode and the external electrode.
The windings 34 and 35 are formed of copper wires with the same diameter. On each of the surfaces of the windings 34 and 35, an insulating film made of polyurethane is provided. A winding start 34a and a winding end 34b, which are the end portions of the first winding 34 represented by a hollow line in the drawing, are connected to the first terminal electrode 32a and the second terminal electrode 32b, respectively, in one of the pairs of terminal electrodes. That is, the winding start 34a of the first winding 34 is connected to the first terminal electrode 32a and the winding end 34b of the first winding 34 is connected to the second terminal electrode 32b. The first winding 34 is connected between the first terminal electrode 32a and the second terminal electrode 32b in one of the pairs of terminal electrodes placed to face each other at positions that are symmetric with respect to the winding center C of the winding core 31c. The one end portion of the first winding 34 that is the winding start 34a and the other end portion of the first winding 34 that is the winding end 34b are located at positions that are symmetric with respect to the winding center C of the winding core 31c.
A winding start 35a and a winding end 35b, which are the end portions of the second winding 35 represented by a black line in the drawing, are connected to the third terminal electrode 33a and the fourth terminal electrode 33b, respectively, in the other one of the pairs of terminal electrodes. That is, the winding start 35a of the second winding 35 is connected to the third terminal electrode 33a and the winding end 35b of the second winding 35 is connected to the fourth terminal electrode 33b. The second winding 35 is connected between the third terminal electrode 33a and the fourth terminal electrode 33b in the other one of the pairs of terminal electrodes placed to face each other at positions that are symmetric with respect to the winding center C of the winding core 31c. The one end portion of the second winding 35 that is the winding start 35a and the other end portion of the second winding 35 that is the winding end 35b are located at positions that are symmetric with respect to the winding center C of the winding core 31c. The connection between the first winding 34 and each of the terminal electrodes 32a and 32b and the connection between the second winding 35 and each of the terminal electrodes 33a and 33b are performed by, for example, thermocompression bonding.
Although the winding start 34a and the winding end 34b, which are one end portion and the other end portion of the first winding 34, respectively, are connected to the first terminal electrode 32a and the second terminal electrode 32b, respectively and the winding start 35a and the winding end 35b, which are one end portion and the other end portion of the second winding 35, respectively, are connected to the third terminal electrode 33a and the fourth terminal electrode 33b, respectively as above, the relationship between the winding start and winding end of the first winding 34 and the relationship between the winding start and winding end of the second winding 35 may be opposite to those described above. That is, the other end portion of the first winding 34 that is the winding end 34b may be a winding start and connected to the second terminal electrode 32b, the one end portion of the first winding 34 that is the winding start 34a may be a winding end and connected to the first terminal electrode 32a, the other end portion of the second winding 35 that is the winding end 35b may be a winding start and connected to the fourth terminal electrode 33b, and one end portion of the second winding 35 that is the winding start 35a may be a winding end and connected to the third terminal electrode 33a.
In the first embodiment, as illustrated in
In the winding-type coil component 27A according to the first embodiment, the first winding 34 and the second winding 35 are wound around the winding core 31c of the core 31 in a pair. The winding start 34a and the winding end 34b of the first winding 34 and the winding start 35a and the winding end 35b of the second winding 35 are connected to the two pairs of terminal electrodes, the terminal electrodes 32a and 32b and the terminal electrodes 33a and 33b, respectively, symmetrically placed with respect to the winding center C of the winding core 31c on a straight line passing through the winding center C on the end surface 31a1 of the flange portion 31a. That is, the winding start 34a and the winding end 34b of the first winding 34 are placed to face each other across the winding center C of the winding core 31c on the end surface 31a1 of the flange portion 31a and are connected to the first terminal electrode 32a and the second terminal electrode 32b, respectively in one of the pairs of terminal electrodes placed on a straight line passing through the winding center C. The winding start 35a and the winding end 35b of the second winding 35 are placed to face each other across the winding center C of the winding core 31c on the end surface 31a1 of the flange portion 31a and are connected to the third terminal electrode 33a and the fourth terminal electrode 33b, respectively in the other one of the pairs of terminal electrodes placed on a straight line passing through the winding center C.
Since the numbers of turns of the first winding 34 and the second winding 35 wound around the winding core 31c are the same, the difference between inductances formed by the first winding 34 and the second winding 35 becomes small. The degree of mode conversion in the winding-type coil component 27A is therefore suppressed, a differential signal passing through the differential signal lines 24a and 24b is unlikely to be converted into common-mode noise, and unnecessary noise caused by the winding-type coil component 27A is unlikely to be emitted.
In the direct-current superimposing circuit 21 according to the first embodiment, as illustrated in
Accordingly, even if the winding-type coil component 27A is used in the direct-current superimposing circuit 21 and the respective wiring patterns of a signal line and a power line and components are placed on a single plane of a circuit board, the wiring pattern of a power line 30a on the positive (+) side of the DC power supply 28 and the wiring pattern of a power line 30b on the negative (−) side of the DC power supply 28 can be connected to the winding start 34a of the first winding 34 that is one of the windings and the winding end 35b of the second winding 35 that is the other one of them, respectively without intersecting with the respective wiring patterns of the pair of the differential signal lines 24a and 24b as illustrated in
As illustrated in
In the winding-type coil component 27A according to the first embodiment in which the first winding 34 and the second winding 35 are wound around the winding core 31c while being parallel to each other and being brought into contact with each other, the first winding 34 and the second winding 35 wound around the winding core 31c of the core 31 have the same diameter and the cross-sectional areas of the windings 34 and 35 are equal. In addition, the distance between the two windings 34 and 35 is reduced and the total amount of crossing of a magnetic flux generated at one of the windings 34 and 35 over the other one of them increases. This leads to the reduction in a leakage inductance. Since the amount of share of magnetic fluxes between the two windings 34 and 35 corresponds to the degree of magnetic coupling, the degree of magnetic coupling between the windings 34 and 35 increases and the respective windings 34 and 35 are magnetically coupled in a winding direction with the same degree of coupling in the winding-type coil component 27A. Accordingly, the symmetry of inductances formed by the respective windings 34 and 35 is enhanced, there is almost no difference between inductances formed by the respective windings 34 and 35, the degree of mode conversion of the winding-type coil component 27A is further reduced, and unnecessary noise caused by the winding-type coil component 27A is highly unlikely to be emitted.
A direct-current superimposing circuit according to the second embodiment differs from the direct-current superimposing circuit 21 according to the first embodiment only in that a winding-type coil component 27B illustrated in
In the winding-type coil component 27A, the first winding 34 and the second winding 35 are wound around the winding core 31c while being parallel to each other and being brought into contact with each other as illustrated in
In a direct-current superimposing circuit according to the second embodiment using the winding-type coil component 27B according to the second embodiment, like in the direct-current superimposing circuit 21 according to the first embodiment, the first winding 34 and the second winding 35 wound around the winding core 31c of the core 31 have the same diameter, the cross-sectional areas of the windings 34 and 35 are equal, the degree of magnetic coupling between the windings 34 and 35 increases, and the respective windings 34 and 35 are magnetically coupled in a winding direction with the same degree of coupling. In the second embodiment, since the windings 34 and 35 are twisted, the positional relationship between the windings 34 and 35 in a winding radial direction is alternately changed and a point where a winding diameter distance is small and a point where the winding diameter distance is large are mixed. As a result, a stray capacitance does not locally increase at each of the windings 34 and 35 and is made uniform and the distribution of a stray capacitance generated at each of the windings 34 and 35 becomes uniform. The degree of mode conversion in the winding-type coil component 27B is further reduced and unnecessary noise caused by the winding-type coil component 27B is more highly unlikely to occur as compared with the case where the windings 34 and 35 are wound around the winding core 31c while being parallel to each other and being brought into contact with each other in the first embodiment. Also in a direct-current superimposing circuit according to the second embodiment, the routing of the wiring patterns at a circuit board is simplified like in the direct-current superimposing circuit 21 according to the first embodiment.
A characteristic line 41 represented by a dotted line in this graph represents the mode conversion characteristics of a winding-type coil component in a direct-current superimposing circuit that is a comparative example. In this winding-type coil component, the number of turns of the first winding 3, which is one of the pair of the windings 3 and 4 illustrated in
A characteristic line 43 represented by a broken line in this graph represents the mode conversion characteristics of the winding-type coil component 27A in the direct-current superimposing circuit 21 according to the first embodiment illustrated in
The graph indicates that, as represented by the characteristic line 42 of a circuit that is a comparative example using a winding-type coil component in which windings are separately wound around the winding core 31c in a pair, the level of a mode-converted signal is up to approximately 10 [dB] lower than that represented by the characteristic line 41 of a direct-current superimposing circuit that is a comparative example using a winding-type coil component in which the number of turns of one winding is larger than that of the other winding by 0.5 and unnecessary noise is unlikely to be emitted. The graph also indicates that, as represented by the characteristic line 43 of the direct-current superimposing circuit 21 according to the first embodiment using the winding-type coil component 27A in which the two windings 34 and 35 are wound around the winding core 31c while being parallel to each other and being brought into contact with each other, the level of a mode-converted signal is up to approximately 20 [dB] lower than that represented by the characteristic line 42 of a circuit that is a comparative example and unnecessary noise is highly unlikely to be emitted. The graph also indicates that, as represented by the characteristic line 44 of a direct-current superimposing circuit according to the second embodiment using the winding-type coil component 27B in which the two windings 34 and 35 are twisted and wound around the winding core 31c, the level of a mode-converted signal is up to approximately 20 [dB] lower than that represented by the characteristic line 43 of a circuit according to the first embodiment and unnecessary noise is more highly unlikely to be emitted as compared with a circuit according to the first embodiment.
In the above embodiments, the description has been made of the case where the terminal electrodes 32a and 32b in one of the two pairs of terminal electrodes and the terminal electrodes 33a and 33b in the other one of them face each other at opposite corners of the end surface 31a1 of the flange portion 31a which are symmetric with respect to the winding center C of the winding core 31c as illustrated in
The terminal electrodes 32a and 32b and the terminal electrodes 33a and 33b, which are two pairs of terminal electrodes, do not necessarily have to be placed to face each other at positions that are perfectly symmetric with respect to the winding center C of the winding core 31c as illustrated in
In the first embodiment, the description has been made of the case where the first winding 34 and the second winding 35 are wound around the winding core 31c while being parallel to each other and being brought into contact with each other throughout the lengths of their winding portions in the winding-type coil component 27A. However, these windings may be wound around the winding core 31c while being parallel to each other and being brought into contact with each other throughout the lengths of at least parts of their winding portions. For example, even in the case where the first winding 34 and the second winding 35 are wound around the winding core 31c while being parallel to each other and being brought into contact with each other throughout the lengths of halves or more of their winding portions, an operational effect similar to that obtained in the above-described first embodiment can be obtained.
In the above second embodiment, the description has been made of the case where the first winding 34 and the second winding 35 are twisted and wound around the winding core 31c throughout the lengths of their winding portions in the winding-type coil component 27B. However, these windings may be twisted and wound around the winding core 31c throughout the lengths of at least parts of their winding portions. For example, even in the case where the first winding 34 and the second winding 35 are twisted and wound around the winding core 31c throughout the lengths of halves or more of their winding portions, an operational effect similar to that obtained in the above-described second embodiment can be obtained.
In the above embodiments, the description has been made of the case where the difference between the inductances of the two windings 34 and 35 in the winding-type coil components 27A and 27B is reduced or almost eliminated. It is most desirable that the inductances of the first winding 34 and the second winding 35 be equal to each other. The term of “being equal to each other” means that the difference between the inductances is less than or equal to 1%. For example, in the case where the inductance value of the first winding 34 is 10.1 H, the inductance value of the second winding 35 is 9.9 H, the difference between the inductance values is 0.2 H, and the average value of the inductance values is 10.0 H, the percentage of the difference between the inductance values of 0.2 H to the average value of the inductance values of 10.0 H is 2% and the difference between the inductance values of 0.2 H is within the range of ±1% of the average value of the inductance values of 10.0 H. In this case, since the difference between the inductances is less than or equal to 1% defined above, it can be said that the inductances of the first winding 34 and the second winding 35 are equal to each other.
In the above embodiments and the above modifications, the description has been made of the winding-type coil components 27A and 27B in which the two windings 34 and 35 are vertically wound around the winding core 31c. The application of the present disclosure to a vertically wound winding-type coil component is suitable and the application of the present disclosure to, for example, a horizontally wound winding-type coil component 37 illustrated in
In the horizontally wound winding-type coil component 37, the winding core axis of the winding core 31c of the core 31 around which the two windings 34 and 35 are wound is placed parallel to a component mounting surface 38. At the top end of the flange portion 31a on the left side, the first terminal electrode 32a is provided to which the winding start 34a of the first winding 34 represented by a dotted line is connected. At the bottom end of the flange portion 31a, the third terminal electrode 33a is provided to which the winding start 35a of the second winding 35 represented by a solid line is connected. At the top end of the flange portion 31b on the right side, the fourth terminal electrode 33b is provided to which the winding end 35b of the second winding 35 is connected. At the bottom end of the flange portion 31b, the second terminal electrode 32b is provided to which the winding end 34b of the first winding 34 is connected. The first winding 34 connects the first terminal electrode 32a and the second terminal electrode 32b. The second winding 35 connects the third terminal electrode 33a and the fourth terminal electrode 33b.
In the horizontally wound winding-type coil component 37, the number of turns of the first winding 34 represented by the dotted line wound around the winding core 31c of the core 31 is larger than that of the second winding 35 represented by the solid line by 0.5 like in the winding-type coil component 1 illustrated in
While preferred embodiments of the disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the disclosure. The scope of the disclosure, therefore, is to be determined solely by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-116249 | Jun 2019 | JP | national |
| 2020-016645 | Feb 2020 | JP | national |
