WO2020026640A1 - Inductor, composite inductor, dc/dc converter, and circuit - Google Patents

Abstract

The inductor of the disclosure comprises: a core having at least a first through hole and a second through hole penetrating in the same direction; a first conductor through which a first current passes, the first conductor having a portion inserted through the first through hole; and a second conductor through which a second current passes, the second conductor having a portion inserted through the second through hole. One of the first current and the second current is a current by which the other current returns to the inductor after passing through the exterior of the inductor. The direction of the second current in the second through hole is the opposite of the direction of the first current in the first through hole.

Description

Inductors, composite inductors, DC / DC converters and circuits

The present disclosure relates to an inductor, a composite inductor, a DC / DC converter, and a circuit. This application claims the priority based on Japanese Patent Application No. 2018-142503 filed on July 30, 2018 and the priority based on Japanese Patent Application No. 2018-192846 filed on October 11, 2018. All the contents described in the above are used.

2. Description of the Related Art DC / DC converters (hereinafter, also simply referred to as converters) for raising and lowering a DC voltage are widely used as power supplies for in-vehicle equipment and industrial equipment. Converters are classified into an insulated type and a non-insulated type depending on whether or not the input and output are insulated by a transformer. The control method of the insulated converter is divided into a forward method and a flyback method.

In general, in an insulated forward converter, a single choke coil (inductor) having a winding wound around a core is interposed on the high potential side of a secondary circuit through which an output current flows (Japanese Patent Application Laid-Open No. H11-163873). 1).

JP-A-11-206118

An inductor according to an embodiment of the present disclosure includes a core having at least a first through hole and a second through hole penetrating in the same direction, and a portion inserted into the first through hole, and a first current flowing therethrough. A first conductor having a portion inserted into the second through-hole and having a second conductor through which a second current flows, wherein one of the first current and the second current is: The other current is a current that returns to the inductor via the outside of the inductor, and the direction of the second current in the second through hole is opposite to the direction of the first current in the first through hole. It is.

A composite inductor according to an aspect of the present disclosure is a composite inductor including the above-described inductor, wherein the first conductor is inserted into the first through hole, and the second conductor is inserted into the second through hole. A plurality of said cores.

A DC / DC converter according to an aspect of the present disclosure includes the above-described inductor or composite inductor, a switching element, and a transformer having a primary winding connected in series to the switching element, wherein the first conductor includes: The outflow current flowing out of the secondary winding of the transformer to the outside is connected so as to flow as a first current, and the second conductor is a return current returning from the outside to the secondary winding as the second current. Connected.

The present application can be realized not only as an inductor, a composite inductor, and a DC / DC converter having such a characteristic configuration, but also as a part of the DC / DC converter as a semiconductor integrated circuit, Or may be implemented as a composite inductor or other system including a DC / DC converter.

FIG. 1 is a block diagram illustrating a configuration example of the DC / DC converter according to the first embodiment. FIG. 2 is an explanatory diagram illustrating an example of an operation state during a period in which power is transmitted from the primary side to the secondary side of the transformer. FIG. 3 is an explanatory diagram illustrating an example of an operation state during a period in which the load current flows back on the secondary side of the transformer. FIG. 4 is a perspective view of the inductor according to the first embodiment as viewed obliquely from above. FIG. 5A is a cross-sectional view taken along line VV of FIG. 4, and is a longitudinal cross-sectional view schematically illustrating a state after assembly of the inductor according to the first embodiment. FIG. 5B is a diagram illustrating a magnetic flux generated in the core of the inductor according to the first embodiment. FIG. 6 is a perspective view of the inductor according to the second embodiment as viewed obliquely from above. FIG. 7 is a cross-sectional view taken along line VII-VII of FIG. 6, and is a longitudinal cross-sectional view schematically illustrating a state after assembly of the inductor according to the second embodiment. FIG. 8A is a plan view showing a first conductor inserted into both of the through holes according to the second embodiment. FIG. 8B is a plan view illustrating the second conductor inserted into both of the through holes according to the second embodiment. FIG. 9A is a plan view showing the first conductor inserted into all of the through holes according to the first modification. FIG. 9B is a plan view showing the second conductor inserted through all of the through holes according to the first modification. FIG. 10A is a plan view showing a first conductor inserted into one of the through holes according to the second modification. FIG. 10B is a plan view showing the second conductor inserted into both of the through holes according to the second modification. FIG. 11A is a plan view showing a first conductor inserted into a part of a through hole according to Modification 3. FIG. 11B is a plan view showing a second conductor inserted through all of the through holes according to the third modification. FIG. 12A is a plan view schematically illustrating a first conductor according to Modification Example 4. FIG. FIG. 12B is a plan view schematically illustrating a second conductor according to Modification 4. FIG. 14 is a perspective view of an inductor according to Modification Example 5 as viewed obliquely from above. It is a side view which shows the inductor attached to the housing | casing typically. FIG. 11 is a block diagram illustrating a configuration example of a DC / DC converter according to a third embodiment. FIG. 2 is a plan view schematically showing a transformer and an inductor formed on a printed wiring board. FIG. 17A is a graph illustrating frequency components of switching noise caused by the DC / DC converter according to the first embodiment. FIG. 17B is a graph illustrating frequency components of switching noise caused by the DC / DC converter according to the third embodiment. FIG. 18 is a circuit diagram illustrating a configuration example of a DC / DC converter according to the fourth embodiment.

[Problems to be solved by embodiments of the present disclosure]
As described above, in the converter described in Patent Literature 1, the inductor is interposed on the high voltage side of the secondary circuit. Since the magnitude of the inductance required for this inductor is inversely proportional to the switching frequency at which the switch is turned on / off, the switching frequency must be relatively high in order to reduce the size of the inductor.

However, as the switching frequency of the switch in the converter increases, there is a trade-off in that the switching loss increases and the wiring becomes difficult, and there is a problem in increasing the switching frequency to the point required for downsizing of the inductor. Many. In particular, it is difficult to secure a necessary inductance unless the conductor portion inserted into the core is formed in a wound shape.

It is desired that the required inductance can be ensured even when the conductor inserted into the core is not wound.

[Description of Embodiment of the Present Disclosure]
First, embodiments of the present disclosure will be listed and described. Further, at least some of the embodiments described below may be arbitrarily combined.

(1) An inductor according to an aspect of the present disclosure includes a core having at least a first through hole and a second through hole penetrating in the same direction, and a portion inserted into the first through hole, and a first current. A first conductor through which the second current flows, and a second conductor through which a second current flows, the first conductor having one of the first current and the second current. The current is a current in which the other current returns to the inductor via the outside of the inductor, and the direction of the second current in the second through hole is the direction of the first current in the first through hole. The opposite is true.

In this aspect, at least two through holes including the first through hole and the second through hole facing in the same direction are formed in the core. The first conductor and the second conductor inserted into two adjacent through holes are connected to the outside such that the first current and the second current flow in opposite directions. Thus, the magnetic flux does not cancel each other in the core between the adjacent first through-hole and the second through-hole. Compared to a case where one conductor is inserted into one through hole in a core having only one through hole, the core of the present embodiment has an inductance that is increased by the number of through holes. Therefore, it is possible to secure necessary inductance even when the conductor inserted into the core is not wound. The first current is, for example, an outflow current from a predetermined current source. The second current is, for example, a return current to the current source.

(2) The first conductor may further include a portion inserted into the second through hole. It is preferable that the first current flows in the same direction as the second current in the second through hole.

In this aspect, both the first conductor and the second conductor are inserted into the second through-hole. Then, the first current and the second current flow in the same direction in the second through hole. Thereby, at a portion where both the first conductor and the second conductor are inserted into the second through hole, the magnetomotive force F (F = NI: N is the number of turns, I is the current) is doubled, and the inductance is increased. It is about 4 times.

(3) The first conductor has a first U-shaped portion, and the first U-shaped portion includes the portion where the first conductor is inserted into the first through hole and the second through hole. It is preferable to include the above-mentioned part penetrated.

In this aspect, the portions inserted into the first through-hole and the second through-hole and the portions connecting these portions are U-shaped. As a result, the conductor partially U-shaped has a relatively simple shape close to point symmetry or line symmetry in plan view.

(4) The second conductor has a second U-shaped portion disposed so as to be opposite to the first U-shaped portion, and the second U-shaped portion is formed of the second conductor. Includes a portion inserted into the first through hole and the portion inserted into the second through hole, wherein the second current flows in the same direction as the first current in the first through hole. preferable.

In this aspect, the U-shaped portions of the first conductor and the second conductor are configured to be opposite to each other. Accordingly, one end and the other end of the first conductor and the second conductor are separated from each other on both sides in the through direction of the through hole, so that connection to the outside is facilitated.

(5) The core is preferably any of EE type, EI type and ER type.

In this embodiment, any of the EE type, EI type and ER type cores having two through holes in abutted state is used, so that widely used cores can be used.

(6) It is preferable that each of the first conductor and the second conductor has a rectangular cross section.

In this aspect, since the cross section of each of the first conductor and the second conductor is rectangular, the thickness of the cross section in the short side direction can be suppressed. In addition, since the surface area with respect to the cross-sectional area of each of the first conductor and the second conductor is large, heat dissipation is good.

(7) Preferably, the first conductor and the second conductor are conductor patterns included in a printed wiring board.

In this aspect, since the conductor pattern included in the printed wiring board is used as the first conductor and the second conductor, the first conductor and the second conductor including the peripheral circuit can be easily formed. it can.

(8) The core is preferably a ferrite core or a dust core. The ferrite core is formed by sintering a magnetic material. The dust core is formed by pressing powder containing a magnetic material.

In this embodiment, since the core is a ferrite core or a dust core, high-frequency characteristics are good. Note that the core may be a nanocrystalline soft magnetic material core or an amorphous core.

(9) The inductor may further include a heat transfer layer containing a heat transfer material, wherein the heat transfer layer is disposed between the first conductor and the second conductor, and the core. preferable.

In this aspect, since the heat transfer material is interposed between the first conductor and the second conductor and the core, heat generated in the conductor is transferred to the outside of the through hole. Get heated.

(10) The core includes a pair of core members that can abut each other, and the first through hole and the second through hole penetrate in a direction along the abutting surface in a state where the pair of the core members abut each other. Is preferred.

(11) The core is located at an intermediate portion between the first through hole and the second through hole, and is located around the first through hole on the first through hole side of the intermediate portion. It can have a 1st outer peripheral part and a 2nd outer peripheral part located around the said 2nd through-hole in the said 2nd through-hole side rather than the said intermediate part. It is preferable that a cross-sectional area of the intermediate portion is larger than a cross-sectional area of the first outer peripheral portion and a cross-sectional area of the second outer peripheral portion.

In this aspect, the intermediate portion is a magnetic path through which a magnetic flux passes between the first through hole and the second through hole. Such a large cross-sectional area of the intermediate portion can increase the inductance.

(12) A composite inductor according to an aspect of the present disclosure is a composite inductor including the above-described inductor, wherein the first conductor is inserted into the first through-hole, and the second conductor is connected to the second through-hole. A plurality of the cores are inserted through the holes.

According to the present aspect, since the entire inductance is distributed to the plurality of inductors by the plurality of cores, the size of each core can be reduced.

(13) A two-terminal pair circuit formed by an inductor formed by inserting the first conductor into the first through hole of each core and inserting the second conductor into the second through hole of each core. Are preferably cascaded.

In this aspect, the inductor formed by inserting the first conductor and the second conductor into the first through hole and the second through hole of the core is regarded as a two-terminal pair circuit including two inductance elements. , Each two-terminal pair circuit is cascaded. As a result, the output from each inductor is taken over by the input of the subsequent inductor.

(14) It is preferable that a capacitor is connected to one terminal pair in at least one of the two-terminal pair circuits.

In this embodiment, since the capacitor is connected to at least one terminal pair in the cascade-connected two-terminal pair circuit, a low-pass filter is formed.

(15) A DC / DC converter according to an aspect of the present disclosure includes the above-described inductor, a switching element, and a transformer having a primary winding connected in series to the switching element. The outflow current flowing out of the secondary winding of the transformer to the outside is connected so as to flow as a first current, and the second conductor is a return current returning from the outside to the secondary winding as the second current. Connected.

In this embodiment, the switching element is connected in series to the primary winding of the transformer, and the outflow current and return current to the secondary winding of the transformer flow through the first and second conductors of the inductor. As a result, when the switching element is turned on / off, a current is induced in the secondary winding of the transformer, and this current flows through the first conductor and the second conductor of the inductor, so that the output current is effectively reduced. Smoothed.

(16) A DC / DC converter according to an aspect of the present disclosure includes the above-described composite inductor, a switching element, and a transformer having a primary winding connected in series to the switching element. The second conductor is connected such that a return current returning from the outside to the secondary winding flows as the second current. Have been.

In this embodiment, the switching element is connected in series to the primary winding of the transformer, and the outflow current and return current to the secondary winding of the transformer flow through the first conductor and the second conductor of the composite inductor. Thereby, when the switching element is turned on / off, a current is induced in the secondary winding of the transformer, and this current flows through the first conductor and the second conductor in the above-described composite inductor, so that the output current is effectively reduced. Is smoothed.

(17) The first conductor is formed integrally with the secondary winding, and at least one of the first conductor and the second conductor is formed integrally with an output-side electric path. Is preferred.

In this aspect, the first conductor is formed integrally with the secondary winding of the transformer, and at least one of the first conductor and the second conductor is formed integrally with the output-side electric circuit. Thus, the number of joints between components can be reduced. Note that both the first conductor and the second conductor may be formed integrally with the electric circuit on the output side.

(18) A DC / DC converter according to an aspect of the present disclosure includes the above-described inductor, a switching element, and a transformer having a primary winding, and at least the switching element, the inductor, and the primary winding. And are connected in series.

In this aspect, since the inductor, the switching element, and the primary winding are connected in series, when the switching element is turned on / off, a current flows to the primary winding of the transformer via the inductor. Flows.

(19) A circuit according to an aspect of the present disclosure includes the above-described inductor, and a circuit element connected in series to the first conductor and the second conductor outside the inductor.

In the present aspect, since the first conductor, the circuit element, and the second conductor are connected in series, one of the first current and the second current flows through the circuit element. Passing it becomes the second current.

[Details of Embodiment of the Present Disclosure]
Specific examples of the inductor, the composite inductor, and the DC / DC converter according to the embodiment of the present disclosure will be described below with reference to the drawings. It should be noted that the present invention is not limited to these exemplifications, but is indicated by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. Further, the technical features described in each embodiment can be combined with each other.

(Embodiment 1)
FIG. 1 is a block diagram illustrating a configuration example of the DC / DC converter 100 according to the first embodiment. The DC / DC converter 100 includes a transformer 10, and the potential of the input-side terminals A and B and the potential of the output-side terminals C and D are separated by the transformer 10. A capacitor 20 is connected between the terminals A and B on the input side, and a predetermined voltage is applied from an external DC power supply (not shown). A capacitor 21 is connected between the output side terminals C and D, and an external load is further connected. The terminal D is connected to, for example, the ground potential.

The DC / DC converter 100 also includes an Nch-type MOSFET (Metal Oxide Semiconductor Connector Field Effect Transistor: hereinafter referred to as an FET) 31 (corresponding to a switching element) connected between one end of the primary winding 11 of the transformer 10 and the terminal B. ), A series circuit of the FET 32 and the capacitor 22 connected between one end of the primary winding 11 and the terminal A, and a control unit 4 for controlling on / off of the FETs 31 and 32. The other end of the primary winding 11 is connected to the terminal A. The FETs 31 and 32 may be other switching elements such as a bipolar transistor and an IGBT (Insulated Gate Bipolar Transistor).

The FET 31 has a drain connected to one end of the primary winding 11, a source connected to the terminal B, and a gate connected to the control unit 4. The FET 32 has a drain connected to one end of the capacitor 22, a source connected to one end of the primary winding 11, and a gate connected to the control unit 4. The other end of the capacitor 22 is connected to the terminal A. Each of the FETs 31 and 32 has a body diode connected in anti-parallel at both ends. The order in which the FET 32 and the capacitor 22 constituting the active clamp circuit are connected in series may be changed.

The secondary winding 12 of the transformer 10 has one end connected to the cathode of the diode 51 and the other end connected to the cathode of the diode 52. The cathode of the diode 52 is further connected to one end of the capacitor 21 and the terminal C via a conductor 61 included in the inductor 6 as a choke coil. The anodes of the diodes 51 and 52 are connected to the other end of the capacitor 21 and the terminal D via a conductor 62 included in the inductor 6.

The inductor 6 is integrated with the core and the conductors 61 and 62. In the circuit diagram, the inductor 6 is represented as if a coil is wound around a core. However, in the first embodiment, the conductors 61 and 62 correspond to the coil. Details of the inductor 6 will be described later.

The DC / DC converter 100 having the above-described configuration is a so-called single-rock type forward converter, and multiplies a predetermined voltage supplied from the terminals A and B by {(duty ratio of the FET 31) / (turn ratio of the transformer 10)}. Are output from terminals C and D. The DC / DC converter 100 is not limited to a single-stone type, and may be any of a multi-stone type push-pull type, a half-bridge type, and a full-bridge type. The description of the example of the multiple stone type is omitted since the type itself is known.

In the first embodiment, voltage conversion is performed by performing PWM (Pulse Width Modulation) control on the FET 31 at a predetermined cycle. Therefore, the voltage conversion operation of the DC / DC converter 100 will be described first. 2 and 3, the illustration of the capacitor 20, the control unit 4, and the terminals C and D is omitted.

FIG. 2 is an explanatory diagram illustrating an example of an operation state during a period in which power is transmitted from the primary side to the secondary side of the transformer 10. During this period, the FET 31 is turned on and the FET 32 is turned off under the control of the control unit 4. Then, a predetermined voltage is applied to the primary winding 11 of the transformer 10 from the terminals A and B to induce a constant voltage in the secondary winding 12, the diode 51 conducts, and the load current that increases linearly in the inductor 6. Flows. During this time, a current (substantial output current) flowing from the secondary winding 12 (corresponding to a predetermined current source) to the capacitor 21 and the load via the conductor 61 is set as an outflow current, and the conductor 62 is transferred from the capacitor 21 and the load. (Current flowing through a so-called return path) that returns to the secondary winding 12 via the control circuit is defined as a return current. The magnitudes of the outflow current and the return current are the same.

On the other hand, a current obtained by adding the load current (more precisely, the current obtained by dividing the magnitude of the load current on the secondary side by the turns ratio of the transformer 10) and the exciting current is applied to the primary winding 11 in a straight line. Flows to increase gradually. The magnetic flux due to the load current flowing through each of the primary winding 11 and the secondary winding 12 cancels each other, while the exciting current creates a magnetic flux in the core of the transformer 10. The capacitor 22 is charged with a voltage that makes the drain side of the FET 32 positive until the current PWM cycle. Hereinafter, for the sake of explanation, a case where the potential of the other end is higher than the one end of the primary winding 11 is defined as a positive voltage. The current flowing from the other end of the primary winding 11 to one end is defined as a positive current.

FIG. 3 is an explanatory diagram showing an example of an operation state during a period in which the load current flows on the secondary side of the transformer 10. At the beginning of this period, the FET 31 is turned off, the load current and the exciting current stop flowing through the FET 31, and the positive exciting current commutates to the body diode of the FET 32 (see the solid line). Although the commutated exciting current decreases linearly, the capacitor 22 is charged while the direction of the exciting current is positive. The load current flowing through one secondary winding 12 via the diode 51 flows back through the diode 52.

(4) Thereafter, the FET 32 is turned on by the control of the control unit 4, and the exciting current flowing through the body diode of the FET 32 flows through the channel region, but the exciting current continues to decrease. Since a negative voltage is applied from the capacitor 22 to the primary winding 11 throughout the period shown in FIG. 3, the exciting current decreases linearly and the polarity is inverted from positive to negative in the middle of the entire period. (See broken line). At this time, the capacitor 22 starts discharging. Then, at the end of the period in which the FET 32 is on, the release of the energy stored in the transformer 10 ends. The load current on the secondary side of the transformer 10 continues to flow back through the diode 52.

Next, details of the inductor 6 will be described. FIG. 4 is a perspective view of the inductor 6 according to the first embodiment viewed obliquely from above, and FIG. 5A is a longitudinal sectional view schematically illustrating a state after the assembly of the inductor 6 according to the first embodiment. In the inductor 6, through holes 60a and 60b whose through directions are aligned in the same direction are formed along the mating surface XX of the EI type cores 63 and 64. One of the pair of through holes 60a and 60b is referred to as a first through hole 60a, and the other is referred to as a second through hole 60b. A pair of conductors 61 and 62 are respectively inserted into the through holes 60a and 60b. Of the pair of conductors 61 and 62, the conductor inserted through the first through hole 60a is referred to as a first conductor 61, and the conductor inserted through the second through hole 60b is referred to as a second conductor 62.

電流 A current flowing through the first conductor 61 is called a first current, and a current flowing through the second conductor 62 is called a second current. Here, the first current is an outflow current, and the second current is a return current. The second current is a current in which the first current returns to the inductor 6 via a load which is a circuit element outside the inductor 6. Further, the first current may be considered to be a current that returns to the inductor 6 via the secondary winding 12 or the diode 52 that is a circuit element outside the inductor 6.

The cores (magnetic cores) 63 and 64 include a magnetic material. The cores 63 and 64 are configured by abutting a pair of core members 63 and 64. One of the pair of core members 63 and 64 is referred to as a first core member 63, and the other is referred to as a second core member. Hereinafter, the first core member 63 may be simply referred to as a core 63, and the second core member 64 may be simply referred to as a core 64. Further, the pair of core members 63 and 64 may be referred to as a pair of cores 63 and 64. The pair of cores 63 and 64 may have other shapes such as an EE type and an ER type.

FIG. 5B shows the magnetic flux generated in the cores 63 and 64 in the first embodiment. The core includes an intermediate portion 160 located between the first through hole 60a and the second through hole 60b. Further, the core includes a first outer peripheral portion 161 located around the first through hole 60a on the first through hole 60a side with respect to the intermediate portion 160. Further, the core includes a second outer peripheral portion 162 located around the first through hole 60b on the second through hole 60b side of the intermediate portion 160.

5B, in FIG. 5B, the outflow current flowing through the first conductor 61 flows from the back side to the front side in FIG. 5B. The return current flowing through the second conductor 62 flows from the near side to the far side in FIG. 5B. The magnetic path through which the magnetic flux M1 generated by the outflow current flowing through the first conductor 61 passes is formed so as to go around the intermediate portion 160 and the first outer peripheral portion 161. The magnetic path through which the magnetic flux M2 generated by the return current flowing through the second conductor 62 passes is formed so as to go around the intermediate portion 160 and the second outer peripheral portion 161.

The core is configured such that the cross-sectional area S1 of the intermediate portion 160 is larger than the cross-sectional area S2 of the first outer peripheral portion 161 and the cross-sectional area S2 of the second outer peripheral portion 162. By increasing the cross-sectional area of the intermediate portion 160 through which a large amount of magnetic flux passes, the inductance of the inductor 6 can be increased. The cross-sectional area S1 of the intermediate portion 160 is preferably 1.5 times or more and 3 times or less the cross-sectional area S2. The cross-sectional area S1 is more preferably twice or more and three or less times the cross-sectional area S2.

The conductors 61 and 62 are rectangular copper wires or bus bars having a rectangular cross section, and the aspect ratio (the ratio of the long side to the short side) is, for example, in the range of 2: 1 to 20: 1. It is not limited. By thus increasing the aspect ratio by making the cross section rectangular, heat dissipation of the conductors 61 and 62 becomes easy.

(4) Since the cores 63 and 64 are made of a powder compact formed by pressing a powder containing a ferrite or a magnetic material formed by sintering a magnetic material, the cores 63 and 64 have good high-frequency characteristics. That is, the cores 63 and 64 are ferrite cores or dust cores. The material of the cores 63 and 64 is not limited to these, and may be, for example, a composite material containing a powder of a soft magnetic material and a resin, or may be a laminate in which plate-like magnetic materials are laminated. The cores 63 and 64 may be nanocrystalline soft magnetic material cores or amorphous cores.

絶 縁 An insulating layer 66 is provided between the conductors 61 and 62 and the cores 63 and 64. When the material of the insulating layers 65 and 66 is a heat dissipation material such as a silicon sheet, the heat dissipation of the conductors 61 and 62 is improved. Here, between the conductors 61, 62 and the insulating layer 66, that is, between the conductors 61, 62 and the cores 63, 64, for example, the heat transfer layers 67, 67 containing a heat transfer material such as a carbon sheet. Is further provided.

At the stage of assembling the inductor 6, the conductors 61 and 62 are placed at positions where the through holes 60 a and 60 b are to be formed in the core 64 before butting the cores 63 and 64. Are assembled together. When the inductor 6 is connected to the peripheral circuit, it is considered that the outflow current flowing through the conductor 61 and the return current flowing through the conductor 62 flow in directions opposite to each other with respect to the direction in which the through holes 60a and 60b penetrate.

Next, the applicable range and performance of the inductor 6 configured as described above will be described. Generally, in a choke coil of a forward type DC / DC converter, required inductance is inversely proportional to a switching frequency, and when the switching frequency is low, the coil cannot be replaced with a conductor having no winding shape. Therefore, in the first embodiment, it is assumed that the switching frequency of the FETs 31 and 32 by the control unit 4 is in the range of 300 kHz to 3 MHz, and that the inductance required for the inductor 6 is in the range of 0.1 μH to 3 μH.

(4) It is assumed that the magnitude of the outflow current and return current flowing through each of the conductors 61 and 62 is in the range of 30A to 250A. Even when such a large current flows, the conductors 61 and 62 of the inductor 6 do not need to be formed in a winding shape, so that heat radiation is relatively easy.

As shown in FIG. 4, the currents flowing through the conductors 61 and 62 inserted in the through holes 60a and 60b are opposite to each other, and the magnetic flux does not cancel out in the core between the through holes 60a and 60b. . Therefore, if the size of the pair of cores 63 and 64 is substantially equal to the size of two other cores having one through hole arranged side by side, the inductance of the inductor 6 will be one conductor Is approximately twice as large as the inductance of the inductor through which.

In the first embodiment, the number of the through holes 60a and 60b is two, but may be three or more. For example, a third through-hole adjacent to the through-hole 60b is formed with the two cores abutting each other, and the conductor 61 is inserted through the third through-hole. Further, when a fourth through-hole adjacent to the through-hole 60a is formed, the conductor 62 is also inserted through the fourth through-hole. When the number of through-holes is increased in this way, focusing on the state where one conductor is inserted into each through-hole, the inductance increases substantially in proportion to the number of through-holes.

Although rectangular copper wires or bus bars are used as the conductors 61 and 62, the conductors 61 and 62 may be formed by a conductor pattern on a printed wiring board. In this case, a part of the insulating layer 66 can be replaced with a prepreg containing epoxy resin and glass fiber, or a part of the insulating layer 66 can be replaced with a resist layer on the substrate surface.

As described above, according to the first embodiment, the through- holes 60a and 60b are formed so as to face in the same direction along the butting surface XX where the pair of cores 63 and 64 including the magnetic material are butted. The outflow current from the secondary winding 12 of the transformer 10 and the return current to the secondary winding 12 are supplied to the pair of conductors 61 and 62 inserted into the two adjacent through holes 60a and 60b, respectively. It flows in a direction opposite to the penetration direction of 60a, 60b. As a result, the magnetic flux does not cancel out in the core between the adjacent through holes 60a and 60b, and the number of through holes is smaller than when one conductor is inserted into one through hole in another core. , The inductance increases substantially in proportion to. Therefore, even when the conductor inserted into the cores 63 and 64 is not wound, it is possible to secure necessary inductance.

Further, according to the first embodiment, since the cross section of each of the pair of conductors 61 and 62 is rectangular, the thickness of the cross section in the short side direction can be suppressed, and the height of the inductor 6 can be suppressed. . Further, since the surface area with respect to the cross-sectional area of each of the pair of conductors 61 and 62 is large, the heat dissipation is improved.

Further, according to the first embodiment, when the conductor pattern included in the printed wiring board is used as the pair of conductors 61 and 62, the pair of conductors 61 and 62 including the peripheral circuit can be easily formed. .

According to the first embodiment, since the ferrite or the compact is used as the material of the cores 63 and 64, the high frequency characteristics are good.

Furthermore, according to the first embodiment, since the heat transfer layers 67, 67 are interposed between the pair of conductors 61, 62 and the cores 63, 64, the heat generated in the conductors 61, 62 penetrates. Heat is preferably transferred to the outside of the holes 60a and 60b.

Further, according to the first embodiment, the FET 31 is connected in series to the primary winding 11 of the transformer 10, and the outflow current and the return current to the secondary winding 12 of the transformer 10 are each a pair of conductors 61 and 62 of the inductor 6. Flows to As a result, when the FET 31 is turned on / off, a current is induced in the secondary winding 12 of the transformer 10, and this current flows through the pair of conductors 61 and 62 of the inductor 6, thereby effectively reducing the output current. Can be smoothed.

(Embodiment 2)
Embodiment 1 is a mode in which a pair of conductors 61 and 62 are separately inserted into two adjacent through holes 60a and 60b, respectively, whereas Embodiment 2 is a mode in which two adjacent through holes 601 and 60b are inserted. In this embodiment, both the pair of conductors 61b and 62b are inserted into each of the conductors 602. Since the block configuration of the DC / DC converter according to the second embodiment is the same as that of the DC / DC converter 100 according to the first embodiment, the illustration is omitted, and the portions corresponding to the first embodiment are denoted by the same reference numerals. The description is omitted.

6 is a perspective view of the inductor 6b according to the second embodiment viewed obliquely from above, and FIG. 7 is a vertical cross-sectional view schematically showing a state after the inductor 6b is assembled. 8A and 8B are plan views respectively showing conductors 61b and 62b inserted into both through holes 601 and 602 according to the second embodiment. FIG. 8A shows the first conductor 61b, and FIG. 8B shows the second conductor 62b. In the inductor 6b, through holes 601 and 602 whose through directions are aligned in the same direction are formed along the abutting surfaces Xb-Xb of the EE- type cores 63b and 64b, and a pair of conductive holes are respectively formed in the through holes 601 and 602. The bodies 61b and 62b are inserted so as to overlap each other. The vertical relationship between the conductors 61b and 62b may be opposite to that shown in FIGS. The pair of cores 63b and 64b may have another shape such as, for example, an EI type or an ER type.

The first conductor 61b has a first U-shaped portion 61bu including a portion inserted into the through holes 601 and 602 and a portion connecting these portions. Similarly, the second conductor 62b has a second U-shaped portion 62bu including a portion inserted into the through holes 601 and 602 and a portion connecting these portions. Therefore, the conductors 61b and 62b have a simple shape that is line-symmetric in plan view. In the examples shown in FIGS. 6, 8A and 8B, the portions including one end and the other end of the conductors 61b and 62b in the direction in which the current flows are bent in opposite directions in the direction intersecting the through holes 601 and 602, respectively. However, it may not be bent in this way. Hereinafter, the portions bent in this manner are referred to as one end and the other end.

When compared with the inductor 6 of the first embodiment shown in FIG. 4, as shown in FIG. 8B, the through-hole 601 has another part of the second U-shaped part 62bu partially inserted in the through-hole 602. Can be seen to have been further inserted. As shown in FIG. 8A, it can be seen that another part of the first U-shaped portion 61bu partially inserted through the through hole 601 is further inserted into the through hole 602.

絶 縁 An insulating layer 65 is provided between the conductors 61b and 62b. An insulating layer 66 is provided between the conductors 61b and 62b and the cores 63b and 64b. Here, heat transfer layers 67, 67 are further provided between the conductors 61b, 62b and the insulating layer 66. A heat transfer layer (not shown) may be further provided between the conductors 61b and 62b.

At the stage of assembling the inductor 6b, the conductors 61b and 62b are placed at positions where the through holes 601 and 602 are to be formed in the core 64b before the cores 63b and 64b are abutted. Are assembled together. When the inductor 6b is connected to a peripheral circuit, the outflow current flowing through the conductor 61b and the return current flowing through the conductor 62b flow in the same direction as the through direction of the through-hole 601 and pass through the through-hole 602. It is taken into consideration that the fluid flows in the same direction.

In this case, as shown in FIGS. 8A and 8B, since the U-shaped portions 61bu and 62bu are configured to be opposite to each other, one ends of the conductors 61b and 62b and the other ends of the conductors 61b and 62b are connected to each other. , The through holes 601 and 602 are separated on both sides in the penetrating direction, thereby facilitating connection with peripheral circuits. Specifically, in the examples shown in FIGS. 1 and 6, an electric path from the other end of the secondary winding 12 is connected to one end of a conductor 61 b into which an outflow current flows, and one end of a conductor 62 b from which a return current flows is a diode 51. , 52 are connected to the anodes. The other end of the conductor 61b from which the outflow current flows is connected to the electric path to the terminal C, and the electric path from the terminal D is connected to the other end of the electric conductor 62b into which the return current flows.

Here, it is generally known that the inductance L of a single-layer solenoid coil having no leakage magnetic flux is expressed by the following equation (1).

^{L = μSN 2/1 ························ (} 1)
However,
μ: magnetic permeability S: cross-sectional area of coil N: number of turns of coil l: magnetic path length of coil

According to the equation (1), when the shape and size of the cores 63b and 64b are constant, the inductance of the inductor 6b is determined by the number of turns of the conductors 61b and 62b, that is, the conductor 61b inserted through each of the through holes 601 and 602. And 62b are proportional to the square of the number (= 2). Therefore, the inductance of the inductor 6b is substantially four times as compared with the case of Embodiment 1 in which the conductors 61 and 62 are individually inserted into the through holes 60a and 60b, respectively, and the conductors 61b and 62b are not formed into a winding shape. Switching frequency can be reduced to 1/4.

In the second embodiment, the U-shaped portions 61bu and 62bu are configured to be opposite to each other with respect to the direction in which the through holes 601 and 602 penetrate. Even if there is some change in the connection with the peripheral circuit, a similar effect can be obtained as the inductor 6b.

In the second embodiment, the insulating layer 66 is disposed between the conductors 61b and 62b and the cores 63b and 64b. However, the cylindrical portion inserted into the through holes 601 and 602 and the through holes 601 and 602 respectively The conductors 61b and 62b may be separately inserted into two bobbins made of an insulator having a flange-shaped flange along the opening surfaces of the two openings. Further, the conductors 61b and 62b may be formed by conductor patterns in different inner layers or outer layers of the multilayer wiring board. In this case, a part of the insulating layer 66 and the insulating layer 65 can be replaced with a prepreg containing an epoxy resin and glass fiber, or a part of the insulating layer 66 can be replaced with a resist layer on the substrate surface.

As described above, according to the second embodiment, the pair of conductors 61b and 62b are connected to each of the two through holes 601 and 602 such that the outflow current and the return current flow in the same direction with respect to the through direction. Both are inserted. Therefore, the magnetomotive force F is doubled and the inductance is substantially quadrupled at the portion where both of the pair of conductors 61b and 62b are inserted, so that the inductance is substantially four times as compared with the inductor 6 according to the first embodiment. Double.

Further, according to the second embodiment, for each of the pair of conductors 61b and 62b, a portion inserted into two adjacent through holes 601 and 602 and a portion connecting these portions have a U-shape. . Therefore, each of the pair of conductors 61b and 62b can have a relatively simple shape that is line-symmetric in plan view.

According to the second embodiment, the U-shaped portions 61bu and 62bu of the pair of conductors 61b and 62b are configured to be opposite to each other. Therefore, one end and the other end of the pair of conductors 61b, 62b are separated on both sides in the through direction of the through holes 601 and 602, so that the connection with the secondary winding 12 and the terminals C and D is easily performed. be able to.

According to the second embodiment, an EE-type, EI-type, or ER-type core having two through holes 601 and 602 in abutted state can be used.

Further, according to the second embodiment, when the conductor patterns included in different inner layers or outer layers of the multilayer wiring board are used as the pair of conductors 61b and 62b, the pair of conductors 61b and 62b including the peripheral circuit can be easily formed. Can be formed.

(Modification 1)
Embodiment 2 is a mode in which two through holes 601 and 602 are formed in a state where a pair of cores 63b and 64b are abutted, whereas Modification 1 is a state where a pair of cores 63c and 64c are abutted. In this embodiment, three through holes 601, 602, and 603 are formed. The configuration of the pair of cores 63c and 64c according to the first modification is the same as that of the second embodiment except that the through- holes 601, 602, and 603 are formed in the same direction. Detailed description is omitted. The case where the number of through holes formed in the pair of cores is four or more is the same as in the case of the second embodiment or the first modification.

FIGS. 9A and 9B are plan views respectively showing the conductors 61c and 62c inserted into all of the through holes 601, 602, and 603 according to the first modification. FIG. 9A shows the first conductor 61c, and FIG. 9B shows the second conductor 62c. The first conductor 61c includes a first U-shaped portion 61cu including a portion inserted into the through holes 601 and 602 and a portion connecting these portions, a portion inserted into the through holes 602 and 603, and these portions. And a first U-shaped portion 61cu including a portion to be connected. The two U-shaped portions 61cu partially overlap. Similarly, the second conductor 62c includes a second U-shaped portion 62cu including a portion inserted into the through holes 601 and 602 and a portion connecting these portions, a portion inserted into the through holes 602 and 603, and And a second U-shaped portion 62cu including a portion connecting the portions.

Thus, the conductors 61c and 62c have a simple point-symmetrical shape in plan view. Further, for each of the conductors 61c and 62c, the current flowing in the portion inserted into the adjacent through- holes 601 and 602 is necessarily in the opposite direction, and the magnetic flux cancels out in the core between the through- holes 601 and 602. It doesn't fit. Similarly, the currents flowing in the portions inserted into the adjacent through holes 602 and 603 are necessarily in opposite directions, and the magnetic flux does not cancel out in the core between the through holes 602 and 603. Therefore, if the size of the pair of cores 63c and 64c is approximately equal to the size of the pair of cores 63b and 64b according to the second embodiment expanded 1.5 times laterally, the inductance of the inductor according to the first modification is: This is approximately 1.5 times the inductance of the inductor 6b according to the second embodiment.

Further, as in the case of the second embodiment, the corresponding U-shaped portions 61cu and 62cu are configured to be opposite to each other, so that one ends of the conductors 61c and 62c and the other ends of the conductors 61c and 62c are opposite to each other. These are separated from each other on both sides of the through- holes 601, 602, and 603 in the direction of penetration, so that connection with peripheral circuits is facilitated. Specifically, an electric path from the other end of the secondary winding 12 is connected to one end of the conductor 61c, and one end of the conductor 62c is connected to anodes of the diodes 51 and 52. The other end of the conductor 61c is connected to the electric path to the terminal C, and the electric path from the terminal D is connected to the other end of the electric conductor 62c.

As described above, according to the first modification, a pair of conductors 61c, 61c, and 603 is formed so that the outflow current and the return current flow in the same direction with respect to the three through holes 601, 602, and 603, respectively. Both of 62c are inserted. Accordingly, the magnetomotive force F is doubled and the inductance is substantially quadrupled at the portion where both of the pair of conductors 61c and 62c are inserted, so that the inductance is approximately 6 compared to the inductor 6 according to the first embodiment. (4x1 + 4x1 / 2)).

According to the first modification, for each of one and the other of the pair of conductors 61c and 62c, a portion inserted into two adjacent through holes 601 and 602 (or the through holes 602 and 603) and these portions. Are U-shaped. Therefore, each of the pair of conductors 61c and 62c can have a relatively simple shape that is point-symmetric in plan view.

According to the first modification, the U-shaped portions 61cu and 62cu on one and the other of the pair of conductors 61c and 62c are configured to be opposite to each other. Therefore, one end and the other end of the pair of conductors 61c, 62c are separated from each other on both sides of the through- holes 601, 602, 603 in the penetrating direction. Can be done.

(Modification 2)
Embodiment 2 is a mode in which both a pair of conductors 61b and 62b are inserted into two through- holes 601 and 602, respectively. 62b, and only the conductor 62b is inserted into the through hole 602. The configuration of the pair of cores 63b and 64b according to the second modification is similar to that of the second embodiment. The conductor 62b is the same as that used in the second embodiment.

10A and 10B are plan views respectively showing conductors 61d and 62b inserted into one and both of through holes 601 and 602 according to the second modification. FIG. 10A shows the first conductor 61d, and FIG. 10B shows the second conductor 62b. FIG. 10B is a reproduction of FIG. 8B. When compared with the inductor 6 of the first embodiment shown in FIG. 4, the other part of the second U-shaped portion 62bu partially inserted in the through hole 602 is further inserted in the through hole 601. You can see.

Thus, the conductor 61d has a simple shape that is substantially point-symmetric in plan view. Further, regarding the conductor 62b, the currents flowing in the portions inserted into the adjacent through holes 601 and 602 are necessarily in opposite directions, and the magnetic flux does not cancel out in the core between the through holes 601 and 602. . Therefore, focusing on a portion where both of the conductors 61d and 62b are inserted, the magnetomotive force F is doubled and the inductance is quadrupled.

Furthermore, one ends of the conductors 61d and 62b are separated from each other on both sides of the through holes 601 and 602 in the direction of penetration, so that connection to peripheral circuits becomes easy. Specifically, an electric path from the other end of the secondary winding 12 is connected to one end of the conductor 61d, and one end of the conductor 62b is connected to anodes of the diodes 51 and 52. The other ends of the conductors 61d and 62b are connected to terminals C and D, respectively.

As described above, according to the second modification, both the pair of conductors 61d and 62b are inserted into one through hole 601 such that the outflow current and the return current flow in the same direction with respect to the through direction. ing. Therefore, the magnetomotive force F is doubled and the inductance is substantially quadrupled at a portion where both of the pair of conductors 61d and 62b are inserted, so that the inductance is approximately 2 in comparison with the inductor 6 according to the first embodiment. .5 times (4 times 1/2 1/2 times 1/2).

(Modification 3)
Modification Example 1 is a mode in which both of a pair of conductors 61c and 62c are inserted into three through holes 601, 602 and 603, respectively. In this embodiment, both the pair of conductors 61e and 62c are inserted, and only the conductor 62c is inserted into the through hole 603. The configuration of the pair of cores 63c and 64c according to the third modification is the same as that of the first modification. The conductor 62c is the same as that used in the first modification.

11A and 11B are plan views respectively showing conductors 61e and 62c inserted through part and all of through holes 601, 602, and 603 according to the third modification. FIG. 11A shows the first conductor 61e, and FIG. 11B shows the second conductor 62c. FIG. 11B is a reproduction of FIG. 9B. When compared with the inductor 6 of the first embodiment shown in FIG. 4, the conductor 62c is further inserted into the through hole 603. Another part of the first U-shaped portion 61eu, part of which is inserted through the through hole 602, is further inserted through the through hole 601. Part of the through hole 603 is inserted through the through hole 602. It can be seen that another part of the second U-shaped portion 62cu is further inserted.

Thus, the conductor 61e has a simple shape that is substantially line-symmetric in plan view. Further, for each of the conductors 61e and 62c, the current flowing in the portion inserted into the adjacent through- holes 601 and 602 is necessarily in the opposite direction, and the magnetic flux cancels out in the core between the through- holes 601 and 602. It doesn't fit. Then, in the conductor 62c, the currents flowing in the portions inserted into the adjacent through holes 602 and 603 are necessarily in opposite directions, and the magnetic flux does not cancel out in the core between the through holes 602 and 603. . Therefore, focusing on a portion where both the conductors 61e and 62c are inserted, the magnetomotive force F is doubled and the inductance is quadrupled.

Further, one ends of the conductors 61e and 62c are separated from each other on both sides of the through holes 601 and 602 in the penetrating direction, thereby facilitating connection with peripheral circuits. Specifically, an electric path from the other end of the secondary winding 12 is connected to one end of the conductor 61e, and one end of the conductor 62c is connected to anodes of the diodes 51 and 52. The other ends of the conductors 61e and 62c are connected to terminals C and D, respectively.

As described above, according to the third modification, a pair of conductors 61e, 61e, and 362 is formed so that outflow current and return current flow in the two through holes 601 and 602 in the same direction. Both of 62c are inserted. Therefore, the magnetomotive force F is doubled and the inductance is substantially quadrupled at the portion where both of the pair of conductors 61e and 62c are inserted, so that the inductance is substantially four times as compared with the inductor 6 according to the first embodiment. 0.5 times (4 × 1 + 1 times × １ ／).

(Modification 4)
Embodiment 2 is a form in which the pair of conductors 61b and 62b are formed separately from the peripheral circuit, whereas Modification 2 is a form in which the pair of conductors 61f and 62f are formed integrally with the peripheral circuit. is there. The configuration of the pair of cores 63b and 64b according to Modification 4 is exactly the same as that of the second embodiment.

FIGS. 12A and 12B are plan views schematically showing a pair of conductors 61f and 62f according to the fourth modification. One end of the conductor 61f is formed integrally with the one-turn secondary winding 12 of the transformer 10, and the other end is formed integrally with the terminal C, as compared with the conductor 61b according to the second embodiment. Have been. The conductor 61f may not be integrated with the terminal C. The other conductor 62f has the other end formed integrally with the terminal D as compared with the conductor 62b according to the second embodiment, but does not necessarily have to be so integrated.

In the fourth modification, the conductor 61b shown in FIG. 6 of the second embodiment is integrated with the secondary winding 12 and the terminal C, and the conductor 62b is integrated with the terminal D. , But is not limited to this. For example, the conductor 61 shown in FIG. 4 of the first embodiment may be integrated with the secondary winding 12 and the terminal C, and the conductor 62 may be integrated with the terminal D, or the conductor shown in FIG. 9C may be integrated with the secondary winding 12 and the terminal C, and the conductor 62c shown in FIG.

As described above, according to the fourth modification, the conductor 61f is formed integrally with the secondary winding 12 and the terminal C of the transformer 10, and the conductor 62f is formed integrally with the terminal D. The number of joints between them can be reduced.

(Modification 5)
Embodiment 2 is a mode in which the mounting method of the inductor 6b is not specified, whereas Modification Example 5 is a mode in which the inductor 6c is mounted on the housing 7. The configuration of the pair of cores 63b and 64b according to Modification 5 is exactly the same as that of the second embodiment.

FIG. 13 is a perspective view of the inductor 6c according to the fifth modification viewed from obliquely above, and FIG. 14 is a side view schematically showing the inductor 6c attached to the housing 7. The inductor 6c is different from the inductor 6b according to the second embodiment in that the conductor 61b is replaced by a conductor 61g. The pair of cores 63b and 64b and the conductor 62b are the same as those in the second embodiment. is there.

If the inductor 6b according to the second embodiment is laid flat on a plane, the lower surface of the conductor 61b is higher than the lower surface of the conductor 62b (see FIGS. 6 and 7). Therefore, in the fifth modification, as shown in FIG. 13, one end and the other end of the conductor 61 g bent in opposite directions are bent stepwise in a thickness direction at a position not overlapping with the conductor 62 b. It is. Thus, when the inductor 6c is placed flat on the housing 7 with the core 64b facing down, the lower surface of one end and the other end of the conductor 61g and the lower surface of the one end and the other end of the conductor 62b. , And the height from the housing 7 becomes the same.

突出 As shown in FIG. 14, projecting portions 71 and 72 having the same height are provided on the upper surface of the housing 7. The protrusion 71 is disposed at a position overlapping one end and the other end of the conductor 62b. The protrusion 72 is arranged at a position overlapping one end and the other end of the conductor 61g. An insulating layer 68 is provided between the upper surface of the protrusion 71 and the lower surfaces of the one end and the other end of the conductor 62b. An insulating layer 69 is provided between the upper surface of the protrusion 72 and the lower surfaces of the one end and the other end of the conductor 61g. An insulating layer 65 is provided between portions where the conductor 61g and the conductor 62b overlap.

As described above, according to the fifth modification, the inductor 6c can be easily attached to the housing 7.

(Embodiment 3)
Embodiment 1 is a mode in which only a pair of cores 63 and 64 are provided, whereas Embodiment 3 is a mode in which a plurality of pairs of cores 63 and 64 are provided. In other words, the third embodiment includes a composite inductor including a plurality of inductors 6 in which a pair of conductors 61 and 62 are inserted into through holes 60a and 60b formed by abutting a pair of cores 63 and 64, respectively. It is. FIG. 15 is a block diagram illustrating a configuration example of a DC / DC converter 100b according to the third embodiment. The DC / DC converter 100b is connected between the transformer 10 for separating the potentials of the input-side terminals A and B and the potentials of the output-side terminals C and D, a pair of conductors 61 and 62, and between the terminals C and D. And a capacitor 23 connected between the conductors 61 and 62.

The secondary winding 12 of the transformer 10 has one end connected to the drain of the FET 51b and the other end connected to the drain of the FET 52b. The drain of the FET 52b is further connected to one end of the capacitor 23 via a conductor 61 included in one inductor (hereinafter, referred to as a first inductor) 6. One end of the capacitor 23 is further connected to one end of the capacitor 21 and a terminal C via a conductor 61 included in the other inductor (hereinafter, referred to as a second inductor) 6. The sources of the FETs 51 b and 52 b are connected to the other end of the capacitor 23 via a conductor 62 included in the first inductor 6. The other end of the capacitor 23 is further connected to the other end of the capacitor 21 and the terminal D via a conductor 62 included in the second inductor 6. The gates of the FETs 51b and 52b are connected to the control unit 4.

In addition, the same reference numerals are given to portions corresponding to the first embodiment, and description thereof will be omitted. Note that the FETs 51b and 52b may be replaced with the diodes 51 and 52 used in the first embodiment. The number of inductors 6 is not limited to two, and may be three or more.

The above-described inductors 6 and 6 correspond to the composite inductor 600. Each inductor 6 is regarded as a two-port pair circuit, and these two-port pair circuits are cascaded. Outflow current flows through the conductor 61 included in the composite inductor 600, and return current flows through the conductor 62. Although a capacitor is not connected to one terminal pair of the two-terminal pair circuit formed by the first inductor 6, a capacitor may be connected here. The capacitor 23 may be regarded as being connected to the other terminal pair of the two-terminal pair circuit formed by the first inductor 6 or connected to one terminal pair of the two-terminal pair circuit formed by the second inductor 6. May be considered. The capacitor 21 may be deleted and included in an external load. It is not always necessary to connect a capacitor between the conductors 61 and 62 at the connection portion of the two-terminal pair circuit adjacent by the inductors 6, 6,.

Next, an example in which the inductors 6 and 6 are formed using a conductor pattern will be described. FIG. 16 is a plan view schematically showing the transformer 10 and the inductors 6 and 6 formed on the printed wiring board 8. The printed wiring board 8 uses a six-layer multi-layer substrate having four inner layers, but the number of inner layers may be three or less or five or more. Although a so-called PQ type core is used for the transformer 10 and EI type cores 63 and 64 are used for the inductors 6 and 6, the present invention is not limited to this.

In the transformer 10, three legs of a PQ-type core are separately inserted into three openings provided at equal intervals in a direction intersecting the longitudinal direction at one longitudinal end of the printed wiring board 8. . The first inductor 6 has three legs of the EI type cores 63 and 64 in three openings provided at regular intervals in a direction intersecting the longitudinal direction at a substantially central portion in the longitudinal direction of the printed wiring board 8. Are inserted separately. The second inductor 6 includes three legs of the EI- type cores 63 and 64 at three openings provided at equal intervals in a direction intersecting the longitudinal direction at the other end in the longitudinal direction of the printed wiring board 8. Are inserted separately. A column portion 91 is provided at one side edge in the longitudinal direction of the printed wiring board 8 and a cutout provided between the inductors 6 and 6 from a casing (not shown) to which the entire printed wiring board 8 is fixed. An L-shaped leaf spring 9 for pressing and fixing the cores 63 and 63 of the inductors 6 and 6 is screwed to the pillar portion 91. The cores 63 and 64 of each inductor 6 may be fixed by an adhesive or the like without using the leaf spring 9.

(4) On one outer layer of the printed wiring board 8, a conductor 61 to be inserted into the through holes 60a, 60a of the inductors 6, 6 is formed by a conductor pattern. This conductor pattern is integrated with the one-turn secondary winding 12 of the transformer 10 and the terminal C. On one outer layer of the printed wiring board 8, a conductor 62 that is inserted into the through holes 60b and 60b of the inductors 6 and 6, respectively, is formed by a conductor pattern. This conductor pattern is integrated with the terminal D. The primary winding 11 of the transformer 10 is formed on an inner layer of the printed wiring board 8. The number of turns (number of turns) of the primary winding 11 may be two or more, for example, by a spiral conductor pattern formed on an arbitrary inner layer. The windings may be connected in series by via holes connecting the inner layers. In addition, the primary winding 11 is shown by a broken line except for an overlapping portion with the conductor 61 and the secondary winding 12.

An FET 51b is surface-mounted between the {secondary winding 12 and the conductor 62} at a location between the transformer 10 and the first inductor 6. An FET 52b is surface-mounted between the conductors 61 and 62 at a location between the transformer 10 and the first inductor 6. The capacitor 23 is surface-mounted between the conductors 61 and 62 at a position between the inductors 6 and 6. The capacitor 23 is formed by connecting three capacitors in parallel, but is not limited to this. For example, one capacitor may be used. The capacitor 21 is surface-mounted between the conductors 61 and 62 at a portion closer to the terminals C and D than the second inductor 6 is. The capacitor 21 is formed by connecting three capacitors in parallel, but is not limited to this. For example, one capacitor may be used. Although the capacitors 21 and 23 are multilayer ceramic capacitors, for example, a lead type ceramic capacitor or a film capacitor may be used.

Next, the result of comparing and verifying the effect of noise reduction by the DC / DC converter 100b according to the third embodiment and the effect of noise reduction by the DC / DC converter 100 according to the first embodiment by simulation will be described. FIG. 17A is a graph illustrating frequency components of switching noise caused by the DC / DC converter 100 according to the first embodiment. FIG. 17B is a graph illustrating frequency components of switching noise caused by the DC / DC converter 100b according to the third embodiment. 17A and 17B, the vertical axis represents the noise level (dB μV), and the horizontal axis represents the relative frequency to the switching frequency (fundamental wave). A broken line indicated by a dashed line in the drawing is a series of peaks of a fundamental wave and a harmonic wave of noise.

The volumes of the cores 63 and 64, the inductance of the inductor 6, and the capacitances of the capacitors 21 and 23 used in the simulation are as follows.
(A) DC / DC converter 100 according to the first embodiment
Volume of cores 63 and 64 = Lml (L is a constant)
Inductance of inductor 6 = MμH (M is a constant)
Capacitance of capacitor 21 = NμF (N is a constant)
(B) DC / DC converter 100b according to the third embodiment
Core 63b, 64b volume = 0.2Lml
Inductance of inductor 6b = 0.2MμH
Capacitance of capacitors 21 and 23 = 0.4 NμF

As shown in FIG. 17B, according to the DC / DC converter 100b according to the third embodiment, as compared with the DC / DC converter 100 according to the first embodiment shown in FIG. (Second harmonic and third harmonic) Noise levels at frequencies corresponding to the respective harmonics are lower by about 10 dB and 20 dB. That is, according to the DC / DC converter 100b according to the third embodiment, even when the cores 63 and 64 according to the first embodiment use the cores 63 and 64 having a volume ratio smaller than 1/4, the harmonics are increased. Wave noise levels can be reduced by 10 dB to 20 dB or more. Such an effect is realized by the first inductor 6 and the capacitor 23 and the second inductor 6 and the capacitor 21 because the two two-terminal pair circuits including the inductors 6 and 6 are cascaded. This is due to the fact that the attenuations of the two low-pass filters are added.

In the third embodiment, since the pair of conductors 61 and 62 are formed by the conductor pattern of the printed wiring board 8, an increase in the number of components, an increase in connection points, an increase in processing steps, and the like are suppressed, and noise is reduced. An effect is obtained that a DC / DC converter having a high reduction effect can be easily manufactured. For example, a bus bar can be used for the pair of conductors 61 and 62. However, in this case, soldering or welding is separately performed between the conductors 61 and 62 and the capacitor 23 and between the conductors 61 and 62 and the capacitor 21 without depending on the connection on the printed wiring board 8. Connection and the number of connection points and man-hours increase.

As described above, according to the third embodiment, the inductance of the composite inductor 600 is distributed to the two inductors 6 and 6 by two pairs of the pair of cores 63 and 64. The volume can be reduced.

According to the third embodiment, each of the inductors 6 formed by inserting the pair of conductors 61 and 62 into the through holes 60a and 60b of the pair of cores 63 and 64 respectively has a two-terminal pair including two inductance elements. The circuits are regarded as circuits, and each two-terminal pair circuit is cascaded. Therefore, the output of the first inductor 6 can be taken over by the input of the second inductor 6.

Furthermore, according to the third embodiment, since the capacitors 23 and 21 are connected to the output-side terminal pairs of the two cascade-connected two-port pair circuits, a two-stage low-pass filter can be formed. it can.

Further, according to the third embodiment, the FET 31 is connected in series to the primary winding 11 of the transformer 10, and the outflow current and return current to the secondary winding 12 of the transformer 10 are controlled by the pair of conductors 61 and 62 of the composite inductor 600. Flows to As a result, when the FET 31 is turned on / off, a current is induced in the secondary winding 12 of the transformer 10, and this current flows through the pair of conductors 61 and 62 in the composite inductor 600, so that the output current is effectively reduced. Can be smoothed.

Further, according to the third embodiment, since the conductor 61 is formed integrally with the secondary winding 12 and the terminal C of the transformer 10 and the conductor 62 is formed integrally with the terminal D, the joining between the components is performed. The number of parts can be reduced.

(Embodiment 4)
FIG. 18 is a circuit diagram illustrating a configuration example of the DC / DC converter 100 according to the fourth embodiment. In the fourth embodiment, the inductor 6 is provided on the input side (the primary winding 11 side) of the transformer 10. The details of the inductor 6 of the fourth embodiment are the same as those of the inductor 6 described above. Also in the inductor 6 of the fourth embodiment, the same inductance (for example, 1 to 3 μH) as the above-described inductor 6 is required.

The DC / DC converter 100 according to the fourth embodiment is a full-bridge type, and four switching elements 35, 36, 37, and 38 constituting a full bridge are provided on the input side (the primary winding 11 side) of the transformer 10. Have been. The full bridge is configured by connecting switching elements 35 and 36 connected in series and switching elements 37 and 38 connected in series.

The inductors 6 of the first to third embodiments are provided on the output side (the secondary winding 12 side) of the transformer 10 included in the DC / DC converter 100. The inductors 6 according to the first to third embodiments are used for smoothing an alternating current and converting it into a direct current. On the other hand, in the fourth embodiment, the inductor 6 is provided on the input side (the primary winding 11 side) of the transformer 10 included in the DC / DC converter 100. The inductor 6 according to the fourth embodiment is used for performing a ZVS (Zero Voltage Switching) operation due to a resonance phenomenon.

In the fourth embodiment, one end of the first conductor 61 is connected between the switching element 35 and the switching element 36 connected in series. The other end of the first conductor 61 is connected to one end of the primary winding 11 of the transformer 10. Therefore, the switching element 35, the first conductor 61 (the inductor 6), and the primary winding 11 are connected in series.

{Circle around (2)} One end of the second conductor is connected between the switching element 35 and the switching element 36 connected in series. The other end of the second conductor 62 is connected to the other end of the primary winding 11 of the transformer 10. Therefore, the switching element 37, the second conductor 62 (the inductor 6), and the primary winding 11 are connected in series.

The switching element 35, the first conductor 61, the first winding 11, the second conductor 62, and the switching element 38 are connected in series. Therefore, when the switching element 35 and the switching element 38 are turned on, a current flows from the switching element 35 to the switching element 38 in the order of the first conductor 61, the first winding 11, and the second conductor 62. In this case, the first current flows through the first conductor 61 and goes to the primary winding 11 which is a circuit element outside the inductor 6. The second current is a current that returns to the second conductor 62 via the primary winding 11.

The switching element 37, the second conductor 62, the first winding 11, the first conductor 61, and the switching element 36 are connected in series. Therefore, when the switching element 37 and the switching element 36 are turned on, a current flows from the switching element 37 to the switching element 36 in the order of the second conductor 62, the first winding 11, and the first conductor 61. In this case, the second current flows through the second conductor 62 and goes to the primary winding 11 which is a circuit element outside the inductor 6. The first current is a current in which the second current returns to the first conductor 61 via the primary winding 11.

In the fourth embodiment, the magnitude of the current flowing through the first conductor 61 and the second conductor 62 is assumed to be in the range of 5 to 20 A, and is a relatively small current. However, in the fourth embodiment, there is a loss (so-called AC loss) caused by an alternating current such as a skin effect or a proximity effect. Therefore, also in the fourth embodiment, it is effective to secure the heat dissipation by the heat transfer layer 67 shown in FIG.

100, 100b DC / DC converter 10 Transformer 11 Primary winding 12 Secondary winding 20, 21, 22, 23 Capacitors 31, 32, 35, 36, 37, 38 FET
4 Controllers 51, 52 Diodes 51b, 52b FET
6, 6b, 6c Inductors 60a, 60b, 601, 602, 603 Through holes 61, 61b, 61c, 61d, 61e, 61f, 61g Conductors 62, 62b, 62c, 62f Conductors 61bu, 61cu, 61eu, 62bu, 62cu U-shaped portions 63, 63b, 63c, 64, 64b, 64c Cores 65, 66, 68, 69 Insulation layer 67 Heat transfer layer 600 Composite inductor 7 Housings 71, 72 Projection 8 Printed wiring board 9 Plate spring 160 Middle part 161 first outer peripheral part 162 second outer peripheral part A, B, C, D terminal S1 intermediate part area S2 outer peripheral area

Claims (19)

1. An inductor,
   A core having at least a first through hole and a second through hole penetrating in the same direction;
   A first conductor having a portion inserted into the first through hole, through which a first current flows;
   A second conductor having a portion inserted through the second through hole, through which a second current flows;
   With
   One of the first current and the second current is a current in which the other current returns to the inductor via the outside of the inductor,
   The direction of the second current in the second through hole is opposite to the direction of the first current in the first through hole.
2. The first conductor further has a portion inserted into the second through-hole,
   The inductor according to claim 1, wherein the first current flows in the second through hole in the same direction as the second current.
3. The first conductor has a first U-shaped portion,
   The inductor according to claim 2, wherein the first U-shaped portion includes the portion where the first conductor is inserted through the first through hole and the portion where the first conductor is inserted through the second through hole.
4. The second conductor has a second U-shaped portion disposed to be opposite to the first U-shaped portion,
   The second U-shaped portion includes a portion where the second conductor is inserted through the first through hole and the portion where the second conductor is inserted through the second through hole.
   The inductor according to claim 3, wherein the second current flows in the same direction as the first current in the first through hole.
5. The inductor according to any one of claims 1 to 4, wherein the core is one of an EE type, an EI type, and an ER type.
6. 6. The inductor according to claim 1, wherein each of the first conductor and the second conductor has a rectangular cross section. 7.
7. The inductor according to any one of claims 1 to 6, wherein the first conductor and the second conductor are conductor patterns included in a printed wiring board.
8. The inductor according to any one of claims 1 to 7, wherein the core is a ferrite core or a dust core.
9. The heat transfer layer further comprising a heat transfer material, wherein the heat transfer layer is disposed between the first conductor and the second conductor, and the core. An inductor according to any one of the preceding claims.
10. The core includes a pair of core members that can abut each other,
    The inductor according to any one of claims 1 to 9, wherein the first through hole and the second through hole penetrate in a direction along an abutting surface in a state where the pair of core members abut each other.
11. The core is
    An intermediate portion located between the first through hole and the second through hole;
    A first outer peripheral portion located around the first through hole on the first through hole side with respect to the intermediate portion;
    A second outer peripheral portion located around the second through hole closer to the second through hole than the intermediate portion;
    Has,
    The inductor according to any one of claims 1 to 10, wherein a cross-sectional area of the intermediate portion is larger than a cross-sectional area of the first outer peripheral portion and a cross-sectional area of the second outer peripheral portion.
12. A composite inductor including the inductor according to any one of claims 1 to 11,
    A composite inductor comprising a plurality of the cores, wherein the first conductor is inserted through the first through-hole, and the second conductor is inserted through the second through-hole.
13. The first conductor is inserted into the first through hole of each core, and the two-terminal pair circuit formed by the inductors formed by inserting the second conductor into the second through hole of each core is cascaded. 13. The composite inductor according to claim 12, wherein:
14. 14. The composite inductor according to claim 13, wherein a capacitor is connected to one terminal pair of the at least one two-terminal pair circuit.
15. An inductor according to any one of claims 1 to 11, and
    A switching element;
    A transformer having a primary winding connected in series with the switching element,
    The first conductor is connected such that an outflow current flowing out of the secondary winding of the transformer to the outside flows as the first current, and the second conductor returns from the outside to the secondary winding. A DC / DC converter connected so that current flows as the second current.
16. A composite inductor according to any one of claims 12 to 14, and a switching element;
    A primary winding comprising a transformer connected in series to the switching element,
    The first conductor is connected such that an outflow current flowing out of the secondary winding of the transformer to the outside flows as the first current, and the second conductor returns from the outside to the secondary winding. A DC / DC converter connected so that current flows as the second current.
17. The first conductor is formed integrally with the secondary winding,
    17. The DC / DC converter according to claim 15, wherein at least one of the first conductor and the second conductor is formed integrally with an electric circuit on an output side.
18. An inductor according to any one of claims 1 to 11, and
    A switching element;
    A transformer having a primary winding;
    With
    A DC / DC converter in which at least the switching element, the inductor, and the primary winding are connected in series.
19. An inductor according to any one of claims 1 to 11, and
    A circuit element connected in series to the first conductor and the second conductor outside the inductor;
    A circuit comprising:

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