WO2017068831A1 - Inductor and dc-dc converter - Google Patents

Inductor and dc-dc converter Download PDF

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Publication number
WO2017068831A1
WO2017068831A1 PCT/JP2016/072310 JP2016072310W WO2017068831A1 WO 2017068831 A1 WO2017068831 A1 WO 2017068831A1 JP 2016072310 W JP2016072310 W JP 2016072310W WO 2017068831 A1 WO2017068831 A1 WO 2017068831A1
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WIPO (PCT)
Prior art keywords
inductor
coil
shield
substrate
converter
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PCT/JP2016/072310
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French (fr)
Japanese (ja)
Inventor
寛之 高辻
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株式会社村田製作所
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Priority to JP2017546426A priority Critical patent/JP6485553B2/en
Publication of WO2017068831A1 publication Critical patent/WO2017068831A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F17/00—Fixed inductances of the signal type 
    • H01F17/04—Fixed inductances of the signal type  with magnetic core
    • H01F17/06—Fixed inductances of the signal type  with magnetic core with core substantially closed in itself, e.g. toroid
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
    • H01F27/36—Electric or magnetic shields or screens
    • H01F27/363—Electric or magnetic shields or screens made of electrically conductive material
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only

Definitions

  • the present invention relates to an inductor and a DC-DC converter.
  • the DC-DC converter mainly includes a switching element, an inductor (power inductor), a capacitor, a diode, and the like, and steps down or boosts (converts) an arbitrary DC voltage to a desired DC voltage.
  • an inductor power inductor
  • a capacitor capacitor
  • a diode diode
  • steps down or boosts boosts (converts) an arbitrary DC voltage to a desired DC voltage.
  • an inductor having a noise suppressing effect for example, there is a multilayer noise filter disclosed in Patent Document 1.
  • This multilayer noise filter is provided on the surface of a laminate in which a plurality of magnetic layers and conductor pattern layers are laminated and the conductor pattern layers are connected to each other to form a spiral inner conductor.
  • a terminal electrode connected to both ends of the internal conductor, and a ground electrode provided on the surface of the multilayer body so as to surround the internal conductor and not to contact the terminal electrode.
  • the ground electrode functions as a low-pass filter by forming a parasitic capacitance with the inductor and suppresses high-frequency noise.
  • the multilayer noise filter disclosed in Patent Document 1 has insufficient effect of suppressing electric field noise because ground electrodes connected to the ground are not provided at both ends of the multilayer body in which the terminal electrodes are arranged. It is.
  • the multilayer body is a coil having an open magnetic circuit structure, the eddy current loss increases when the magnetic flux leaking from the multilayer body hits the electrode (metal).
  • the efficiency of the DC-DC converter decreases.
  • the present invention has been made to solve the above-described problems, and can suppress the noise of the electric field radiated to the outside of the inductor and can suppress the efficiency reduction of the power supply circuit on which the inductor is mounted on the substrate. And a DC-DC converter.
  • An inductor according to the present invention is an inductor mounted on a substrate for a power supply circuit, and has a closed magnetic circuit structure having a core made of a magnetic material and a winding, and an external electrode electrically connected to the coil. And a conductive shield that is electrically connected to the ground of the substrate and is provided so as not to contact the external electrode at least at a part of the periphery of the coil.
  • the inductor of the present invention since the conductive shield connected to the ground is provided around the coil, this shield shields the noise of the electric field generated in the coil, and the electric field radiated to the outside. Noise can be suppressed.
  • the coil since the coil has a closed magnetic circuit structure, magnetic flux does not leak from the coil. Therefore, in this inductor, since the magnetic flux does not hit the conductive shield provided around the coil, eddy current loss does not occur. Thereby, the efficiency fall of the power supply circuit by which the inductor which concerns on this invention was mounted in the board
  • the shield is preferably provided on the entire surface around the coil. In this way, it is possible to block the noise of the electric field in all directions generated by the coil, and to improve the effect of suppressing the noise of the electric field radiated to the outside.
  • the shield has a sufficiently small opening with respect to the wavelength of the noise to be shielded. In this way, even when a shield is provided on the entire surface around the coil, the heat dissipation is improved by the opening, and the heat transmitted to the substrate can be reduced.
  • the substrate is a multilayer wiring substrate, the inductor is mounted on one surface of the multilayer wiring substrate, and the multilayer wiring substrate has an external electrode electrically connected to the first layer on one surface side.
  • a wiring layer may be disposed, and a ground plane to which the shield is electrically connected may be disposed in the third layer with the second insulating layer interposed therebetween.
  • the substrate is a multilayer wiring substrate, the inductor is mounted on one surface of the multilayer wiring substrate, and the multilayer wiring substrate has external electrodes on the first layer on one surface side.
  • a configuration in which an electrically connected wiring layer is disposed and a ground plane in which a shield is electrically connected so as not to contact the wiring layer is disposed.
  • a ground plane in which a shield is electrically connected is disposed. Also good.
  • ground plane is disposed on the lower surface side of the inductor, this ground plane functions as a conductive shield. For this reason, according to the inductor of each configuration, it is not necessary to provide a conductive shield on the lower surface side of the inductor, and electric field noise can be shielded by the ground plane.
  • the DC-DC converter according to the present invention includes a substrate on which any of the above-described inductors is mounted. According to the DC-DC converter according to the present invention, as described above, the noise of the electric field radiated to the outside from the inductor mounted on the substrate can be suppressed, and the decrease in the efficiency of the DC-DC converter can be suppressed.
  • the noise of the electric field radiated to the outside of the inductor can be suppressed, and the efficiency reduction of the power supply circuit (in particular, the DC-DC converter) in which the inductor is mounted on the substrate can be suppressed.
  • FIG. 1 is a perspective view of an inductor according to a first embodiment. It is a perspective view of the coil which concerns on embodiment. 1 is a circuit diagram of a DC-DC converter according to an embodiment. It is a comparative table of the efficiency of a DC-DC converter. It is a perspective view of the inductor which concerns on 2nd Embodiment. It is a sectional side view which shows a part of inductor and board
  • the present invention is applied to an inductor mounted on a substrate of a DC-DC converter (corresponding to the power supply circuit described in claims) used in an automobile.
  • a DC-DC converter corresponding to the power supply circuit described in claims
  • FIG. 1 is a perspective view of the inductor according to the first embodiment.
  • FIG. 2 is a perspective view of the coil according to the embodiment.
  • FIG. 3 is a circuit diagram of the DC-DC converter according to the embodiment.
  • the inductor 1 is a power inductor used as one of electronic components of the DC-DC converter 4.
  • the inductor 1 is mounted on the substrate 5 of the DC-DC converter 4.
  • the inductor 1 includes a coil 10, a pair of external electrodes 20, and a shield 31.
  • the coil 10 has a core 11 and a winding 12.
  • the coil 10 has a closed magnetic circuit structure, and is, for example, a toroidal type coil.
  • the coil 10 may be a winding type coil or a laminated type coil.
  • the core 11 is made of a magnetic material.
  • the core 11 is, for example, an annular toroidal core.
  • the winding 12 is made of a conductor.
  • the winding 12 is wound around the core 11.
  • the coil 10 includes a toroidal core 11 made of ferrite or the like and a winding wire 12 made of copper wire or the like wound spirally.
  • the pair of external electrodes 20 are electrode terminals for mounting the inductor 1 on the substrate 5.
  • the pair of external electrodes 20 are electrically connected to predetermined wiring locations on the substrate 5.
  • the external electrode 20 is made of a conductor.
  • One external electrode 20 of the pair is electrically connected to one end of the winding 12 and is connected to a wiring portion on the input side of the DC-DC converter 4.
  • the other external electrode 20 is electrically connected to the other end of the winding 12 and is connected to a wiring location on the output side of the DC-DC converter 4.
  • the pair of external electrodes 20 are arranged to face each other with the coil 10 interposed therebetween.
  • the shield 31 is a member for shielding electric field noise generated in the coil 10.
  • the shield 31 is made of a conductor (for example, metal) and has conductivity.
  • the shield 31 is provided around the coil 10 so as not to contact the external electrode 20.
  • the shield 31 is preferably provided on at least a part of the periphery of the coil 10 and provided on the entire surface (all parts) of the periphery of the coil 10.
  • the shield 31 may be provided on the entire surface (six surfaces) of the rectangular parallelepiped, or a part of one surface (upper surface) and two surfaces (upper surface and lower surface) of the rectangular parallelepiped. It may be provided on the surface. In the case of the example shown in FIG.
  • the external electrode 20 is disposed on two opposing side surfaces of the six surfaces of the rectangular parallelepiped, so a conductor that serves as a shield at a portion that does not contact the external electrode 20 (substantially concave shape)
  • the remaining four surfaces are all provided with a conductor serving as a shield (rectangular shape).
  • the shield 31 may be provided in close contact with the surface of the coil 10, or may be provided in a state of being formed in a box shape or the like and having a space between the coil 10.
  • the shield 31 is electrically connected (grounded) to the ground of the substrate 5 in order to bypass electric field noise to the ground.
  • a connection terminal 31 a is formed on the shield 31.
  • the connection terminal 31a is electrically connected to the ground of the substrate 5 (for example, a predetermined location on the ground plane).
  • the form using the connection terminal 31 a is shown, but various forms can be applied as a form for connecting the shield 31 to the ground of the substrate 5.
  • the DC-DC converter 4 in which the inductor 1 is used will be briefly described.
  • the DC-DC converter 4 steps down or boosts (converts) an arbitrary DC voltage input from the power supply 40 to a desired DC voltage, and outputs electric energy of the converted voltage to the load 50.
  • the DC-DC converter 4 is used in an automobile and, for example, steps down 12V of a battery (power supply 40) to 5V and outputs it to a load 50.
  • the DC-DC converter 4 is a chopper type (switching type) DC-DC converter.
  • the DC-DC converter 4 mainly includes an input side capacitor 4a, a switching element 4b, a diode 4c, an inductor 1 (coil 10), and an output side capacitor 4d. These electronic components are mounted on the substrate 5.
  • the switching element 4b is subjected to switching control by a controller (not shown) or the like, and is turned on / off. This switching frequency is, for example, 100 kHz to 1 MHz.
  • the shield 31 of the inductor 1 is connected to the ground as shown in FIG.
  • the inductor 1 (particularly, the coil 10) in the DC-DC converter 4 will be described.
  • the switching element 4b When the switching element 4b is turned on, a current flows into the coil 10. At this time, the coil 10 generates an electromotive force and stores energy so as to prevent an inflowing current due to a self-induction action.
  • the switching element 4b When the switching element 4b is turned off, the inflow of current to the coil 10 is stopped. At this time, the coil 10 flows the stored energy as a current to the output side in an attempt to maintain the current.
  • the current flowing by this switching is smoothed by the coil 10 and the capacitor 4d and output to the load 50.
  • the operation of the shield 31 in the inductor 1 will be described.
  • the coil 10 of the inductor 1 generates electric field noise. Since the conductive shield 31 connected to the ground is provided around the coil 10, the shield 31 shields the noise of the electric field generated in the coil 10. Thereby, the noise of the electric field radiated
  • the shield 31 when the shield 31 is provided on the entire surface around the coil 10, the shield 31 blocks electric field noise generated in the coil 10 in all directions, so that electric field noise radiated to the outside is most reduced.
  • the shield 31 is provided on a part of the periphery of the coil 10 (for example, one surface), the noise of the electric field radiated to the outside is reduced.
  • the coil 10 generates a magnetic field when a current flows, and forms a magnetic flux. Since the coil 10 has a closed magnetic circuit structure, the magnetic flux circulates in the core 11 and ideally the magnetic flux does not leak from the coil 10. Therefore, in the inductor 1, the shield 31 is provided around the coil 10, but magnetic flux does not strike the shield 31. Thereby, an eddy current generated when the magnetic flux hits the conductive (metal) shield does not occur, and a loss due to Joule heat (eddy current loss) generated by the eddy current does not occur. Therefore, in the DC-DC converter 4, there is no efficiency reduction due to eddy current loss. Incidentally, in the case of a coil having an open magnetic circuit structure, the magnetic flux leaks from the end of the core of the coil, so that the eddy current is generated when the magnetic flux hits the conductive shield, resulting in eddy current loss.
  • FIG. 4 is a comparison table of efficiency of DC-DC converters.
  • Efficiency is expressed in percent (%) and is 100% when the DC-DC converter has no loss.
  • the efficiency was obtained by obtaining the input power and output power of the DC-DC converter, dividing the output power by the input power, and multiplying the divided value by 100.
  • the DC-DC converter is a DC-DC converter that steps down from 12V to 5V.
  • the DC-DC converter has a switching frequency of 200 kHz and a power supplied from a power source of 3 W.
  • the four different inductors include an inductor without a conductive shield around a coil with an open magnetic circuit structure (for example, an open magnetic circuit structure with magnetic powder), and a conductive shield around a coil with an open magnetic circuit structure.
  • the conductive shield is provided by, for example, winding a copper foil tape around the entire surface of the coil.
  • the inductor 1 since the conductive shield 31 connected to the ground of the substrate 5 is provided around the coil 10, the electric field generated in the coil 10 by the shield 31 is reduced. Noise can be prevented from being radiated to the outside of the inductor 1. As a result, the noise radiated from the inductor 1 (and hence the DC-DC converter 4) is converted into a radiated emission standard (for example, CISPR25 (International Radio Interference Special Committee (CISPR)) Recommended limit value and measurement method) Class 5) can be reduced to a satisfactory level.
  • a radiated emission standard for example, CISPR25 (International Radio Interference Special Committee (CISPR)) Recommended limit value and measurement method
  • the conductive shield 31 is provided around the coil 10, but since the coil 10 has a closed magnetic circuit structure, eddy current loss can be suppressed. As a result, the efficiency reduction of the DC-DC converter 4 in which the inductor 1 is mounted on the substrate 5 can be suppressed.
  • the inductor 1 according to the first embodiment when the conductive shield 31 is provided on the entire surface around the coil 10, electric field noise generated in the coil 10 can be blocked and radiated to the outside. The effect of suppressing noise in the electric field can be improved. Further, in the inductor 1 according to the first embodiment, when the conductive shield 31 is provided only in a part around the coil 10, heat generated in the coil 10 is suppressed while suppressing noise of an electric field radiated to the outside. Can be dissipated. Thereby, the heat transmitted from the inductor 1 to the substrate 5 can be reduced.
  • FIG. 5 is a perspective view of the inductor according to the second embodiment.
  • the inductor 2 according to the second embodiment is different from the inductor 1 according to the first embodiment in that a conductive shield has a heat dissipation function.
  • the inductor 2 according to the second embodiment is limited to the case where the shield is provided on the entire surface around the coil 10.
  • the inductor 2 includes a coil 10, a pair of external electrodes 20, and a shield 32.
  • the conductive shield 32 is provided on the entire surface (all parts) around the coil 10 so as not to contact the external electrode 20.
  • the shield 32 is formed with a connection terminal 32 a, and the connection terminal 32 a is electrically connected to the ground of the substrate 5.
  • the shield 32 has an opening 34 formed therein.
  • the opening 34 is a hole penetrating from the inner (coil 10 side) surface to the outer surface of the shield 32.
  • the shape of the opening 34 is not particularly limited, and is, for example, a slit shape, a rectangular shape, a circular shape, or an elliptical shape.
  • the number of openings 34 is not particularly limited, and may be one or plural.
  • the shield 32 includes a plurality of openings 34 formed in a slit shape on one surface (upper surface 32 b). The length of one opening 34 needs to be sufficiently small with respect to the wavelength of noise to be shielded.
  • the operation of the shield 32 in the inductor 2 will be described.
  • the coil 10 generates heat when energized.
  • the shield 32 is provided on the entire surface around the coil 10, since the opening 34 is formed in the shield 32, the heat generated in the coil 10 is dissipated to the outside from the opening 34.
  • the inductor 2 according to the second embodiment has the same effects as the inductor 1 according to the first embodiment, and also has the following effects.
  • the shield 32 is provided on the entire surface around the coil 10, but by providing the opening 34 in the shield 32, heat dissipation from the inside of the shield 32 to the outside is improved. To do. Thereby, the heat transferred from the inductor 2 to the substrate 5 can be reduced.
  • FIG. 6 is a side sectional view showing a part of the inductor and the substrate according to the third embodiment.
  • the inductor 3 according to the third embodiment is different from the inductor 1 according to the first embodiment in that a shield function is provided on the substrate of the DC-DC converter 4.
  • the inductor 3 is a power inductor mounted on the substrate 6 of the DC-DC converter 4.
  • the inductor 3 includes a coil 10, a pair of external electrodes 20, and a shield 33.
  • the shield 33 having conductivity is provided so as not to come into contact with the external electrode 20 at least at a part other than the lower surface (mounting surface) side around the coil 10.
  • the shield 33 may be provided on five surfaces excluding the lower surface of the rectangular parallelepiped, or may be provided on a part of the five surfaces. In the case of the example shown in FIG. 6, the shield 33 is provided only on the upper surface.
  • a connection terminal 33 a is formed on the shield 33.
  • the connection terminal 33a is electrically connected to a ground plane 9 of the substrate 6 described later.
  • the connection terminal 33a is formed, for example, by forming vias in the inductor 3 and the substrate 6 and connecting the vias with solder.
  • the substrate 6 is a multilayer wiring substrate.
  • the inductor 3 is mounted on one surface of the substrate 6.
  • the wiring layer 7 is disposed in the first layer
  • the insulating layer 8 is disposed in the second layer
  • the ground plane 9 is disposed in the third layer.
  • a power layer and a signal layer to which other electronic components of the DC-DC converter 4 are connected are stacked with an insulating layer interposed therebetween.
  • the wiring layer 7 is a layer on which the inductor 3 is mounted.
  • the wiring layer 7 is formed with a wiring pattern to which the pair of external terminals 7 of the inductor 3 are connected.
  • the wiring pattern of the wiring layer 7 is made of, for example, copper foil.
  • the insulating layer 8 is a layer that electrically insulates the wiring layer 7 and the ground plane 9.
  • the insulating layer 8 has a thin plate shape made of, for example, insulating resin, dielectric, ceramics, or the like.
  • the ground plane 9 is a so-called solid ground layer in which a ground pattern made of copper foil or the like is formed on substantially one surface.
  • the operation of the shield 33 in the inductor 3 and the ground plane 9 of the substrate 6 will be described.
  • the coil 10 generates electric field noise. Since the conductive shield 33 connected to the ground pattern 9 is provided around the coil 10, the shield 33 shields electric field noise generated in the coil 10. Further, since the ground plane 9 is disposed on the lower surface side of the coil 10, the ground plane 9 shields electric field noise generated by the coil 10 (particularly noise radiated downward from the coil 10). Since no signal layer to which electronic components other than the inductor 3 of the DC-DC converter 4 are connected is arranged between the coil 10 and the ground plane 9, the signal layer and the electronic component are connected from the coil 10. Unaffected by electric field noise.
  • the inductor 3 according to the third embodiment has the same effects as the inductor 1 according to the first embodiment, and also has the following effects. According to the inductor 3 according to the third embodiment, since the ground plane 9 is disposed on the lower surface side of the coil 10, the ground plane 9 functions as a shield, and electric field noise generated in the coil 10 by the ground plane 9. Can be prevented from being radiated to the outside of the inductor 3 (particularly, inside the substrate 6).
  • the present invention is not limited to the above-described embodiments, and various modifications can be made.
  • the present invention is applied to an inductor of a DC-DC converter used in an automobile.
  • the present invention can also be applied to an inductor (power inductor) used in other power supply circuits, and also to a DC-DC converter used in other than an automobile. Applicable.
  • the present invention can also be applied to other closed magnetic circuit structure coils such as the EI type.
  • the rectangular parallelepiped shield was shown in the said embodiment, other shapes, such as a hemispherical shape and a cylindrical shape, may be sufficient as a shape of a shield.
  • the wiring layer is disposed on the first layer on one side of the multilayer wiring board on which the inductor is mounted, the insulating layer is disposed on the second layer, and the ground plane is disposed on the third layer.
  • the ground plane may be arranged in the first layer on one side of the multilayer wiring board.
  • a wiring layer (wiring pattern) to which the external electrode of the inductor is electrically connected is disposed in the first layer, and a shield is electrically connected so as not to contact the wiring layer. Is placed.
  • the first-layer ground plane functions as a shield.

Abstract

This inductor (1) which is mounted on a substrate (5) for a power supply circuit (for example, for a DC-DC converter) is provided with: a coil (10) of a closed magnetic path structure having a core (11) that is formed of a magnetic body and a winding wire (12); an external electrode (20) that is electrically connected to the coil (10); and a conductive shield (31) that is electrically connected to the ground of the substrate (5), while being provided on at least a part of the periphery of the coil so as not to be in contact with the external electrode (20).

Description

インダクタ及びＤＣ－ＤＣコンバータInductor and DC-DC converter
　本発明は、インダクタ及びＤＣ－ＤＣコンバータに関する。 The present invention relates to an inductor and a DC-DC converter.
　ＤＣ－ＤＣコンバータは、主として、スイッチング素子、インダクタ（パワーインダクタ）、コンデンサ、ダイオード等を備え、任意の直流電圧を所望の直流電圧に降圧又は昇圧（変換）する。ＤＣ－ＤＣコンバータが自動車等で用いられる場合、ノイズを遮蔽できない樹脂ケース等にＤＣ－ＤＣコンバータが収納されていると、ＤＣ－ＤＣコンバータ（特に、インダクタ）から放射されるノイズが問題となる。 The DC-DC converter mainly includes a switching element, an inductor (power inductor), a capacitor, a diode, and the like, and steps down or boosts (converts) an arbitrary DC voltage to a desired DC voltage. When the DC-DC converter is used in an automobile or the like, noise radiated from the DC-DC converter (particularly an inductor) becomes a problem if the DC-DC converter is housed in a resin case or the like that cannot shield noise.
　ノイズ抑制効果のあるインダクタとしては、例えば、特許文献１に開示された積層型ノイズフィルタがある。この積層型ノイズフィルタは、磁性体層と導体パターン層とが複数積層されかつ導体パターン層が互いに接続されることで螺旋状の内部導体が形成された積層体と、積層体の表面に設けられかつ内部導体の両端部に接続された端子電極と、積層体の表面に内部導体を囲むようにかつ端子電極に接触しないように設けられた接地電極と、を備えている。この構成により、接地電極がインダクタとの寄生容量を形成することでローパスフィルタとして機能し、高周波のノイズを抑制する。 As an inductor having a noise suppressing effect, for example, there is a multilayer noise filter disclosed in Patent Document 1. This multilayer noise filter is provided on the surface of a laminate in which a plurality of magnetic layers and conductor pattern layers are laminated and the conductor pattern layers are connected to each other to form a spiral inner conductor. And a terminal electrode connected to both ends of the internal conductor, and a ground electrode provided on the surface of the multilayer body so as to surround the internal conductor and not to contact the terminal electrode. With this configuration, the ground electrode functions as a low-pass filter by forming a parasitic capacitance with the inductor and suppresses high-frequency noise.
特開平１１－１８６０４０号公報Japanese Patent Laid-Open No. 11-186040
　しかしながら、特許文献１に開示の積層型ノイズフィルタは、端子電極が配置される積層体の両端部にはグランドに接続される接地電極が設けられていないので、電界のノイズの抑制効果が不十分である。また、この積層型ノイズフィルタは、積層体が開磁路構造のコイルとなっているので、積層体から漏れ出た磁束が電極（金属）に当たると渦電流損が大きくなる。このような渦電流損の大きいインダクタがＤＣ－ＤＣコンバータで用いられた場合、ＤＣ－ＤＣコンバータの効率が低下する。 However, the multilayer noise filter disclosed in Patent Document 1 has insufficient effect of suppressing electric field noise because ground electrodes connected to the ground are not provided at both ends of the multilayer body in which the terminal electrodes are arranged. It is. In this multilayer noise filter, since the multilayer body is a coil having an open magnetic circuit structure, the eddy current loss increases when the magnetic flux leaking from the multilayer body hits the electrode (metal). When such an inductor with a large eddy current loss is used in a DC-DC converter, the efficiency of the DC-DC converter decreases.
　本発明は、上記問題点を解消する為になされたものであり、インダクタの外部に放射される電界のノイズを抑制でき、かつ、インダクタが基板に実装された電源回路の効率低下を抑制できるインダクタ及びＤＣ－ＤＣコンバータを提供することを目的とする。 The present invention has been made to solve the above-described problems, and can suppress the noise of the electric field radiated to the outside of the inductor and can suppress the efficiency reduction of the power supply circuit on which the inductor is mounted on the substrate. And a DC-DC converter.
　本発明に係るインダクタは、電源回路用の基板に実装されるインダクタであって、磁性体からなるコアと巻線とを有する閉磁路構造のコイルと、コイルに電気的に接続される外部電極と、基板のグランドに電気的に接続され、コイルの周囲の少なくとも一部分に外部電極と接触しないように設けられる導電性のシールドと、を備えることを特徴とする。 An inductor according to the present invention is an inductor mounted on a substrate for a power supply circuit, and has a closed magnetic circuit structure having a core made of a magnetic material and a winding, and an external electrode electrically connected to the coil. And a conductive shield that is electrically connected to the ground of the substrate and is provided so as not to contact the external electrode at least at a part of the periphery of the coil.
　本発明に係るインダクタによれば、グランドに接続された導電性のシールドがコイルの周囲に設けられているので、このシールドによりコイルで発生した電界のノイズを遮蔽し、外部に放射される電界のノイズを抑制できる。また、本発明に係るインダクタは、コイルが閉磁路構造であるため、コイルから磁束が漏れ出ない。そのため、このインダクタでは、コイルの周囲に設けられた導電性のシールドに磁束が当たらないので、渦電流損が生じない。これにより、本発明に係るインダクタが基板に実装された電源回路の効率低下を抑制できる。 According to the inductor of the present invention, since the conductive shield connected to the ground is provided around the coil, this shield shields the noise of the electric field generated in the coil, and the electric field radiated to the outside. Noise can be suppressed. In the inductor according to the present invention, since the coil has a closed magnetic circuit structure, magnetic flux does not leak from the coil. Therefore, in this inductor, since the magnetic flux does not hit the conductive shield provided around the coil, eddy current loss does not occur. Thereby, the efficiency fall of the power supply circuit by which the inductor which concerns on this invention was mounted in the board | substrate can be suppressed.
　本発明に係るインダクタでは、シールドは、コイルの周囲の全面に設けられることが好ましい。このようにすれば、コイルで発生した全ての方向の電界のノイズを遮断でき、外部に放射される電界のノイズの抑制効果を向上させることができる。 In the inductor according to the present invention, the shield is preferably provided on the entire surface around the coil. In this way, it is possible to block the noise of the electric field in all directions generated by the coil, and to improve the effect of suppressing the noise of the electric field radiated to the outside.
　本発明に係るインダクタでは、シールドには、遮蔽したいノイズの波長に対して十分に小さな開口部が形成されていることが好ましい。このようにすれば、コイルの周囲の全面にシールドが設けられている場合でも、開口部によって放熱性が向上し、基板に伝わる熱を低減できる。 In the inductor according to the present invention, it is preferable that the shield has a sufficiently small opening with respect to the wavelength of the noise to be shielded. In this way, even when a shield is provided on the entire surface around the coil, the heat dissipation is improved by the opening, and the heat transmitted to the substrate can be reduced.
　本発明に係るインダクタでは、基板は、多層配線基板であり、インダクタは、多層配線基板の一方の面に実装され、多層配線基板は、一方の面側の第一層目に外部電極が電気的に接続される配線層が配置されると共に第二層目の絶縁層を挟んで第三層目にシールドが電気的に接続されるグランドプレーンが配置される構成としてもよい。また、本発明に係るインダクタでは、基板は、多層配線基板であり、インダクタは、多層配線基板の一方の面に実装され、多層配線基板は、一方の面側の第一層目に外部電極が電気的に接続される配線層が配置されると共に配線層と接触しないようにシールドが電気的に接続されるグランドプレーンが配置されるシールドが電気的に接続されるグランドプレーンが配置される構成としてもよい。 In the inductor according to the present invention, the substrate is a multilayer wiring substrate, the inductor is mounted on one surface of the multilayer wiring substrate, and the multilayer wiring substrate has an external electrode electrically connected to the first layer on one surface side. In addition, a wiring layer may be disposed, and a ground plane to which the shield is electrically connected may be disposed in the third layer with the second insulating layer interposed therebetween. In the inductor according to the present invention, the substrate is a multilayer wiring substrate, the inductor is mounted on one surface of the multilayer wiring substrate, and the multilayer wiring substrate has external electrodes on the first layer on one surface side. A configuration in which an electrically connected wiring layer is disposed and a ground plane in which a shield is electrically connected so as not to contact the wiring layer is disposed. A ground plane in which a shield is electrically connected is disposed. Also good.
　このいずれの構成でも、グランドプレーンがインダクタの下面側に配置されるので、このグランドプレーンが導電性のシールドとして機能する。そのため、この各構成のインダクタによれば、インダクタの下面側に導電性のシールドを設ける必要がなく、グランドプレーンにより電界のノイズを遮蔽できる。 In any of these configurations, since the ground plane is disposed on the lower surface side of the inductor, this ground plane functions as a conductive shield. For this reason, according to the inductor of each configuration, it is not necessary to provide a conductive shield on the lower surface side of the inductor, and electric field noise can be shielded by the ground plane.
　本発明に係るＤＣ－ＤＣコンバータは、上述した何れかのインダクタが実装された基板を備えていることを特徴とする。本発明に係るＤＣ－ＤＣコンバータによれば、上述したように、基板に実装されたインダクタから外部に放射される電界のノイズを抑制でき、かつ、ＤＣ－ＤＣコンバータの効率の低下を抑制できる。 The DC-DC converter according to the present invention includes a substrate on which any of the above-described inductors is mounted. According to the DC-DC converter according to the present invention, as described above, the noise of the electric field radiated to the outside from the inductor mounted on the substrate can be suppressed, and the decrease in the efficiency of the DC-DC converter can be suppressed.
　本発明によれば、インダクタの外部に放射される電界のノイズを抑制でき、かつ、インダクタが基板に実装された電源回路（特に、ＤＣ－ＤＣコンバータ）の効率低下を抑制できる。 According to the present invention, the noise of the electric field radiated to the outside of the inductor can be suppressed, and the efficiency reduction of the power supply circuit (in particular, the DC-DC converter) in which the inductor is mounted on the substrate can be suppressed.
第１の実施形態に係るインダクタの斜視図である。1 is a perspective view of an inductor according to a first embodiment. 実施形態に係るコイルの斜視図である。It is a perspective view of the coil which concerns on embodiment. 実施形態に係るＤＣ－ＤＣコンバータの回路図である。1 is a circuit diagram of a DC-DC converter according to an embodiment. ＤＣ－ＤＣコンバータの効率の比較表である。It is a comparative table of the efficiency of a DC-DC converter. 第２の実施形態に係るインダクタの斜視図である。It is a perspective view of the inductor which concerns on 2nd Embodiment. 第３の実施形態に係るインダクタと基板の一部を示す側断面図である。It is a sectional side view which shows a part of inductor and board | substrate which concerns on 3rd Embodiment.
　以下、図面を参照して本発明の好適な実施形態について詳細に説明する。なお、図中、同一又は相当部分には同一符号を用いることとする。また、各図において、同一要素には同一符号を付して重複する説明を省略する。 Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals are used for the same or corresponding parts. Moreover, in each figure, the same code | symbol is attached | subjected to the same element and the overlapping description is abbreviate | omitted.
　実施形態では、自動車で用いられるＤＣ－ＤＣコンバータ（請求の範囲に記載の電源回路に相当）の基板に実装されるインダクタに適用する。以下の説明では、３つの実施形態について説明する。 In the embodiment, the present invention is applied to an inductor mounted on a substrate of a DC-DC converter (corresponding to the power supply circuit described in claims) used in an automobile. In the following description, three embodiments will be described.
　図１～図３を参照して、第１の実施形態に係るインダクタ１について説明する。図１は、第１の実施形態に係るインダクタの斜視図である。図２は、実施形態に係るコイルの斜視図である。図３は、実施形態に係るＤＣ－ＤＣコンバータの回路図である。 The inductor 1 according to the first embodiment will be described with reference to FIGS. FIG. 1 is a perspective view of the inductor according to the first embodiment. FIG. 2 is a perspective view of the coil according to the embodiment. FIG. 3 is a circuit diagram of the DC-DC converter according to the embodiment.
　インダクタ１は、ＤＣ－ＤＣコンバータ４の電子部品の一つとして用いられるパワーインダクタである。インダクタ１は、ＤＣ－ＤＣコンバータ４の基板５に実装される。インダクタ１は、コイル１０と、一対の外部電極２０と、シールド３１と、を備えている。 The inductor 1 is a power inductor used as one of electronic components of the DC-DC converter 4. The inductor 1 is mounted on the substrate 5 of the DC-DC converter 4. The inductor 1 includes a coil 10, a pair of external electrodes 20, and a shield 31.
　コイル１０は、コア１１と、巻線１２と、を有している。コイル１０は、閉磁路構造であり、例えば、トロイダル型のコイルである。コイル１０は、巻線タイプのコイルでもよいし、積層タイプのコイルでもよい。コア１１は、磁性体からなる。コア１１は、例えば、円環状であるトロイダル形状のコアである。巻線１２は、導体からなる。巻線１２は、コア１１に巻回されている。コイル１０は、例えば、図２に示すように、フェライト等からなるトロイダル型のコア１１に銅線等からなる巻線１２が螺旋状に巻回されている。 The coil 10 has a core 11 and a winding 12. The coil 10 has a closed magnetic circuit structure, and is, for example, a toroidal type coil. The coil 10 may be a winding type coil or a laminated type coil. The core 11 is made of a magnetic material. The core 11 is, for example, an annular toroidal core. The winding 12 is made of a conductor. The winding 12 is wound around the core 11. For example, as shown in FIG. 2, the coil 10 includes a toroidal core 11 made of ferrite or the like and a winding wire 12 made of copper wire or the like wound spirally.
　一対の外部電極２０は、インダクタ１を基板５に実装するための電極端子である。一対の外部電極２０は、基板５の所定の配線箇所に電気的に接続される。外部電極２０は、導体からなる。一対のうちの一方の外部電極２０は、巻線１２の一方の端部に電気的に接続されており、ＤＣ－ＤＣコンバータ４の入力側の配線箇所に接続される。他方の外部電極２０は、巻線１２の他方の端部に電気的に接続されており、ＤＣ－ＤＣコンバータ４の出力側の配線箇所に接続される。一対の外部電極２０は、例えば、コイル１０を挟んで対向して配置されている。 The pair of external electrodes 20 are electrode terminals for mounting the inductor 1 on the substrate 5. The pair of external electrodes 20 are electrically connected to predetermined wiring locations on the substrate 5. The external electrode 20 is made of a conductor. One external electrode 20 of the pair is electrically connected to one end of the winding 12 and is connected to a wiring portion on the input side of the DC-DC converter 4. The other external electrode 20 is electrically connected to the other end of the winding 12 and is connected to a wiring location on the output side of the DC-DC converter 4. For example, the pair of external electrodes 20 are arranged to face each other with the coil 10 interposed therebetween.
　シールド３１は、コイル１０で発生する電界のノイズを遮蔽するための部材である。シールド３１は、導体（例えば、金属）からなり、導電性を有している。シールド３１は、コイル１０の周囲に外部電極２０と接触しないように設けられる。シールド３１は、コイル１０の周囲の少なくとも一部分に設けられ、コイル１０の周囲の全面（全部分）に設けることが好ましい。シールド３１は、例えば、直方体形状とした場合、直方体の全面（六つの面）に設けられてもよいし、直方体の一つの面（上面）、二つの面（上面と下面）等の一部の面に設けられてもよい。図１に示す例の場合、直方体の六つの面のうちの対向する２つの側面には外部電極２０が配置されているので、外部電極２０と接触しない部分（略凹形状）にシールドとなる導体が設けられ、残りの４つの面には全ての部分（矩形状）にシールドとなる導体が設けられている。シールド３１は、コイル１０の表面に密着した状態で設けられてもよいし、または、箱状等に形成されて、コイル１０との間に空間を有する状態で設けられてもよい。 The shield 31 is a member for shielding electric field noise generated in the coil 10. The shield 31 is made of a conductor (for example, metal) and has conductivity. The shield 31 is provided around the coil 10 so as not to contact the external electrode 20. The shield 31 is preferably provided on at least a part of the periphery of the coil 10 and provided on the entire surface (all parts) of the periphery of the coil 10. For example, when the shield 31 has a rectangular parallelepiped shape, the shield 31 may be provided on the entire surface (six surfaces) of the rectangular parallelepiped, or a part of one surface (upper surface) and two surfaces (upper surface and lower surface) of the rectangular parallelepiped. It may be provided on the surface. In the case of the example shown in FIG. 1, the external electrode 20 is disposed on two opposing side surfaces of the six surfaces of the rectangular parallelepiped, so a conductor that serves as a shield at a portion that does not contact the external electrode 20 (substantially concave shape) The remaining four surfaces are all provided with a conductor serving as a shield (rectangular shape). The shield 31 may be provided in close contact with the surface of the coil 10, or may be provided in a state of being formed in a box shape or the like and having a space between the coil 10.
　シールド３１は、電界のノイズをグランドにバイパスするために、基板５のグランドに電気的に接続される（接地される）。シールド３１には、接続端子３１ａが形成されている。接続端子３１ａは、基板５のグランド（例えば、グランドプレーンの所定箇所）に電気的に接続される。なお、この実施形態では接続端子３１ａによる形態を示したが、シールド３１を基板５のグランドに接続する形態としては種々の形態が適用可能である。 The shield 31 is electrically connected (grounded) to the ground of the substrate 5 in order to bypass electric field noise to the ground. A connection terminal 31 a is formed on the shield 31. The connection terminal 31a is electrically connected to the ground of the substrate 5 (for example, a predetermined location on the ground plane). In this embodiment, the form using the connection terminal 31 a is shown, but various forms can be applied as a form for connecting the shield 31 to the ground of the substrate 5.
　インダクタ１が用いられるＤＣ－ＤＣコンバータ４についても簡単に説明しておく。ＤＣ－ＤＣコンバータ４は、電源４０から入力される任意の直流電圧を所望の直流電圧に降圧又は昇圧（変換）し、この変換した電圧の電気エネルギを負荷５０に出力する。ＤＣ－ＤＣコンバータ４は、自動車で用いられ、例えば、バッテリ（電源４０）の１２Ｖを５Ｖに降圧して負荷５０に出力する。ＤＣ－ＤＣコンバータ４は、チョッパ方式（スイッチング方式）のＤＣ－ＤＣコンバータである。 The DC-DC converter 4 in which the inductor 1 is used will be briefly described. The DC-DC converter 4 steps down or boosts (converts) an arbitrary DC voltage input from the power supply 40 to a desired DC voltage, and outputs electric energy of the converted voltage to the load 50. The DC-DC converter 4 is used in an automobile and, for example, steps down 12V of a battery (power supply 40) to 5V and outputs it to a load 50. The DC-DC converter 4 is a chopper type (switching type) DC-DC converter.
　ＤＣ－ＤＣコンバータ４は、例えば、図３に示すように、主として、入力側のコンデンサ４ａ、スイッチング素子４ｂ、ダイオード４ｃと、インダクタ１（コイル１０）と、出力側のコンデンサ４ｄとを備えており、これらの電子部品が基板５に実装されている。スイッチング素子４ｂは、コントローラ（図示せず）等によってスイッチング制御されて、ＯＮ／ＯＦＦする。このスイッチング周波数は、例えば、１００ｋＨｚ～１ＭＨｚである。なお、インダクタ１のシールド３１は、図３に示すように、グランドに接続されている。 For example, as shown in FIG. 3, the DC-DC converter 4 mainly includes an input side capacitor 4a, a switching element 4b, a diode 4c, an inductor 1 (coil 10), and an output side capacitor 4d. These electronic components are mounted on the substrate 5. The switching element 4b is subjected to switching control by a controller (not shown) or the like, and is turned on / off. This switching frequency is, for example, 100 kHz to 1 MHz. The shield 31 of the inductor 1 is connected to the ground as shown in FIG.
　このＤＣ－ＤＣコンバータ４におけるインダクタ１（特に、コイル１０）の作用について説明する。スイッチング素子４ｂがＯＮすると、コイル１０に電流が流入する。このとき、コイル１０は、自己誘導作用により、流入する電流を妨げるように起電力を発生してエネルギを蓄える。スイッチング素子４ｂがＯＦＦすると、コイル１０への電流の流入が停止する。このとき、コイル１０は、電流を維持しようとして、蓄えたエネルギを出力側に電流として流す。このスイッチングにより流れる電流は、コイル１０とコンデンサ４ｄによって平滑化されて、負荷５０に出力される。 The operation of the inductor 1 (particularly, the coil 10) in the DC-DC converter 4 will be described. When the switching element 4b is turned on, a current flows into the coil 10. At this time, the coil 10 generates an electromotive force and stores energy so as to prevent an inflowing current due to a self-induction action. When the switching element 4b is turned off, the inflow of current to the coil 10 is stopped. At this time, the coil 10 flows the stored energy as a current to the output side in an attempt to maintain the current. The current flowing by this switching is smoothed by the coil 10 and the capacitor 4d and output to the load 50.
　インダクタ１におけるシールド３１の作用について説明する。インダクタ１のコイル１０は、電界のノイズを発生する。このコイル１０の周囲にはグランドに接続された導電性のシールド３１が設けられているので、このシールド３１がコイル１０で発生した電界のノイズを遮蔽する。これにより、インダクタ１の外部に放射される電界のノイズが低減される。特に、コイル１０の周囲の全面にシールド３１が設けられている場合、シールド３１がコイル１０で発生した全ての方向の電界のノイズを遮断するので、外部に放射される電界のノイズが最も低減される。コイル１０の周囲の一部分（例えば、一つの面）にシールド３１が設けられている場合でも、外部に放射される電界のノイズが低減される。 The operation of the shield 31 in the inductor 1 will be described. The coil 10 of the inductor 1 generates electric field noise. Since the conductive shield 31 connected to the ground is provided around the coil 10, the shield 31 shields the noise of the electric field generated in the coil 10. Thereby, the noise of the electric field radiated | emitted outside the inductor 1 is reduced. In particular, when the shield 31 is provided on the entire surface around the coil 10, the shield 31 blocks electric field noise generated in the coil 10 in all directions, so that electric field noise radiated to the outside is most reduced. The Even when the shield 31 is provided on a part of the periphery of the coil 10 (for example, one surface), the noise of the electric field radiated to the outside is reduced.
　また、コイル１０は、電流が流れると磁界を発生し、磁束を形成する。このコイル１０は閉磁路構造であるので、磁束がコア１１で循環し、理想的には磁束がコイル１０から漏れ出ない。そのため、インダクタ１では、コイル１０の周囲にシールド３１が設けられているが、このシールド３１に磁束が当たらない。これにより、磁束が導電性（金属）のシールドに当たることで発生する渦電流が発生せず、渦電流によって発生するジュール熱による損失（渦電流損）が生じない。そのため、ＤＣ－ＤＣコンバータ４では、渦電流損による効率低下がない。ちなみに、開磁路構造のコイルの場合、コイルのコアの端部から磁束が漏れ出るので、磁束が導電性のシールドに当たることで渦電流を発生し、渦電流損を生じる。 The coil 10 generates a magnetic field when a current flows, and forms a magnetic flux. Since the coil 10 has a closed magnetic circuit structure, the magnetic flux circulates in the core 11 and ideally the magnetic flux does not leak from the coil 10. Therefore, in the inductor 1, the shield 31 is provided around the coil 10, but magnetic flux does not strike the shield 31. Thereby, an eddy current generated when the magnetic flux hits the conductive (metal) shield does not occur, and a loss due to Joule heat (eddy current loss) generated by the eddy current does not occur. Therefore, in the DC-DC converter 4, there is no efficiency reduction due to eddy current loss. Incidentally, in the case of a coil having an open magnetic circuit structure, the magnetic flux leaks from the end of the core of the coil, so that the eddy current is generated when the magnetic flux hits the conductive shield, resulting in eddy current loss.
　図４を参照して、ＤＣ－ＤＣコンバータの効率について説明する。図４は、ＤＣ－ＤＣコンバータの効率の比較表である。ここでは、インダクタが異なる４つのＤＣ－ＤＣコンバータの効率を比較した。効率は、パーセント（％）で表し、ＤＣ－ＤＣコンバータに損失がない場合には１００％である。効率は、ＤＣ－ＤＣコンバータの入力電力と出力電力を取得し、出力電力を入力電力で除算して、その除算値に１００を乗算することで得た。ＤＣ－ＤＣコンバータは、１２Ｖから５Ｖに降圧するＤＣ－ＤＣコンバータである。ＤＣ－ＤＣコンバータは、スイッチング周波数が２００ｋＨｚであり、電源からの供給電力が３Ｗである。 The efficiency of the DC-DC converter will be described with reference to FIG. FIG. 4 is a comparison table of efficiency of DC-DC converters. Here, the efficiency of four DC-DC converters with different inductors was compared. Efficiency is expressed in percent (%) and is 100% when the DC-DC converter has no loss. The efficiency was obtained by obtaining the input power and output power of the DC-DC converter, dividing the output power by the input power, and multiplying the divided value by 100. The DC-DC converter is a DC-DC converter that steps down from 12V to 5V. The DC-DC converter has a switching frequency of 200 kHz and a power supplied from a power source of 3 W.
　４つの異なるインダクタは、開磁路構造（例えば、磁性体粉末付き開磁路構造）のコイルの周囲に導電性のシールドが無いインダクタと、開磁路構造のコイルの周囲に導電性のシールドが有るインダクタと、閉磁路構造のコイル１０の周囲に導電性のシールドが無いインダクタと、閉磁路構造のコイル１０の周囲に導電性のシールド３１が有るインダクタ（このインダクタが実施形態に係るインダクタ１に相当）と、である。導電性のシールドは、例えば、銅箔テープをコイルの全面に巻き付けることで設けられる。 The four different inductors include an inductor without a conductive shield around a coil with an open magnetic circuit structure (for example, an open magnetic circuit structure with magnetic powder), and a conductive shield around a coil with an open magnetic circuit structure. An inductor having no conductive shield around the coil 10 having a closed magnetic circuit structure, and an inductor having a conductive shield 31 around the coil 10 having a closed magnetic circuit structure (this inductor is the inductor 1 according to the embodiment). Equivalent). The conductive shield is provided by, for example, winding a copper foil tape around the entire surface of the coil.
　開磁路構造のコイルの周囲に導電性のシールドが無いインダクタを用いたＤＣ－ＤＣコンバータの場合、効率が９０％であった。開磁路構造のコイルの周囲に導電性のシールドが有るインダクタを用いたＤＣ－ＤＣコンバータの場合、効率が８８％であった。これにより、開磁路構造のコイルの場合、導電性のシールドが有るとＤＣ－ＤＣコンバータの効率が低下することが判る。このように効率が低下するのは、閉磁路構造のコイルから漏れ出た磁束が導電性のシールドに当たることで渦電流損が生じるからである。 In the case of a DC-DC converter using an inductor having no conductive shield around a coil with an open magnetic circuit structure, the efficiency was 90%. In the case of a DC-DC converter using an inductor having a conductive shield around a coil having an open magnetic circuit structure, the efficiency was 88%. Thus, it can be seen that in the case of a coil having an open magnetic circuit structure, the efficiency of the DC-DC converter is lowered if there is a conductive shield. The reason why the efficiency is reduced in this way is that eddy current loss occurs when the magnetic flux leaked from the coil having the closed magnetic circuit structure hits the conductive shield.
　閉磁路構造のコイル１０の周囲に導電性のシールドが無いインダクタを用いたＤＣ－ＤＣコンバータの場合、効率が９３％であった。閉磁路構造のコイル１０の周囲に導電性のシールド３１が有るインダクタ１を用いたＤＣ－ＤＣコンバータ４の場合、効率が９３％であった。これにより、閉磁路構造のコイル１０の場合、導電性のシールドが有ってもＤＣ－ＤＣコンバータの効率が低下しないことが判る。このように効率が低下しないのは、閉磁路構造のコイルからは磁束が漏れ出ないので、導電性のシールドが有っても渦電流損が生じないからである。 In the case of a DC-DC converter using an inductor without a conductive shield around the coil 10 having a closed magnetic circuit structure, the efficiency was 93%. In the case of the DC-DC converter 4 using the inductor 1 having the conductive shield 31 around the coil 10 having the closed magnetic circuit structure, the efficiency was 93%. Thus, it can be seen that in the case of the coil 10 having the closed magnetic circuit structure, the efficiency of the DC-DC converter does not decrease even if there is a conductive shield. The reason why the efficiency does not decrease in this way is that magnetic flux does not leak out from the coil having the closed magnetic circuit structure, so that eddy current loss does not occur even if there is a conductive shield.
　この第１の実施形態に係るインダクタ１によれば、基板５のグランドに接続された導電性のシールド３１がコイル１０の周囲に設けられているので、このシールド３１によりコイル１０で発生する電界のノイズがインダクタ１の外部に放射されるのを抑制できる。これにより、インダクタ１（ひいては、ＤＣ－ＤＣコンバータ４）から放射されるノイズを、放射エミッションの規格（例えば、ＣＩＳＰＲ２５（国際無線障害特別委員会（ＣＩＳＰＲ）の車載受信機保護のための妨害波の推奨限度値および測定法）　Ｃｌａｓｓ５）を満足できる程度まで低減できる。 According to the inductor 1 according to the first embodiment, since the conductive shield 31 connected to the ground of the substrate 5 is provided around the coil 10, the electric field generated in the coil 10 by the shield 31 is reduced. Noise can be prevented from being radiated to the outside of the inductor 1. As a result, the noise radiated from the inductor 1 (and hence the DC-DC converter 4) is converted into a radiated emission standard (for example, CISPR25 (International Radio Interference Special Committee (CISPR)) Recommended limit value and measurement method) Class 5) can be reduced to a satisfactory level.
　また、第１の実施形態に係るインダクタ１によれば、コイル１０の周囲に導電性のシールド３１が設けられているが、コイル１０が閉磁路構造であるため、渦電流損を抑制できる。これにより、このインダクタ１が基板５に実装されたＤＣ－ＤＣコンバータ４の効率低下を抑制できる。 In addition, according to the inductor 1 according to the first embodiment, the conductive shield 31 is provided around the coil 10, but since the coil 10 has a closed magnetic circuit structure, eddy current loss can be suppressed. As a result, the efficiency reduction of the DC-DC converter 4 in which the inductor 1 is mounted on the substrate 5 can be suppressed.
　また、第１の実施形態に係るインダクタ１では、コイル１０の周囲の全面に導電性のシールド３１を設けた場合、コイル１０で発生した全ての方向の電界のノイズを遮断でき、外部に放射される電界のノイズの抑制効果を向上させることができる。また、第１の実施形態に係るインダクタ１では、コイル１０の周囲の一部分にのみ導電性のシールド３１を設けた場合、外部に放射される電界のノイズを抑制しつつ、コイル１０で発生する熱を放散できる。これにより、インダクタ１から基板５に伝わる熱を低減できる。 In addition, in the inductor 1 according to the first embodiment, when the conductive shield 31 is provided on the entire surface around the coil 10, electric field noise generated in the coil 10 can be blocked and radiated to the outside. The effect of suppressing noise in the electric field can be improved. Further, in the inductor 1 according to the first embodiment, when the conductive shield 31 is provided only in a part around the coil 10, heat generated in the coil 10 is suppressed while suppressing noise of an electric field radiated to the outside. Can be dissipated. Thereby, the heat transmitted from the inductor 1 to the substrate 5 can be reduced.
　図５を参照して、第２の実施形態に係るインダクタ２について説明する。図５は、第２の実施形態に係るインダクタの斜視図である The inductor 2 according to the second embodiment will be described with reference to FIG. FIG. 5 is a perspective view of the inductor according to the second embodiment.
　第２の実施形態に係るインダクタ２は、第１の実施形態に係るインダクタ１と比較すると、導電性のシールドに放熱機能を持たせる点が異なる。但し、第２の実施形態に係るインダクタ２は、シールドがコイル１０の周囲の全面に設けられた場合に限られる。インダクタ２は、コイル１０と、一対の外部電極２０と、シールド３２と、を備えている。 The inductor 2 according to the second embodiment is different from the inductor 1 according to the first embodiment in that a conductive shield has a heat dissipation function. However, the inductor 2 according to the second embodiment is limited to the case where the shield is provided on the entire surface around the coil 10. The inductor 2 includes a coil 10, a pair of external electrodes 20, and a shield 32.
　導電性を有するシールド３２は、コイル１０の周囲の全面（全部分）に外部電極２０と接触しないように設けられる。シールド３２は、接続端子３２ａが形成され、接続端子３２ａが基板５のグランドに電気的に接続される。 The conductive shield 32 is provided on the entire surface (all parts) around the coil 10 so as not to contact the external electrode 20. The shield 32 is formed with a connection terminal 32 a, and the connection terminal 32 a is electrically connected to the ground of the substrate 5.
　特に、シールド３２には、開口部３４が形成されている。開口部３４は、シールド３２の内側（コイル１０側）の面から外側の面まで貫く穴である。開口部３４の形状は、特に限定されず、例えば、スリット状、矩形状、円形状、楕円形状である。開口部３４の個数は、特に限定されず、１つでもよいし、複数でもよい。例えば、図５に示すように、シールド３２の一つの面（上面３２ｂ）にスリット状に形成された複数の開口部３４からなる。一つの開口部３４の長さは、遮蔽したいノイズの波長に対して十分に小さい必要がある。 In particular, the shield 32 has an opening 34 formed therein. The opening 34 is a hole penetrating from the inner (coil 10 side) surface to the outer surface of the shield 32. The shape of the opening 34 is not particularly limited, and is, for example, a slit shape, a rectangular shape, a circular shape, or an elliptical shape. The number of openings 34 is not particularly limited, and may be one or plural. For example, as shown in FIG. 5, the shield 32 includes a plurality of openings 34 formed in a slit shape on one surface (upper surface 32 b). The length of one opening 34 needs to be sufficiently small with respect to the wavelength of noise to be shielded.
　インダクタ２におけるシールド３２の作用について説明する。コイル１０は、通電すると発熱する。このコイル１０の周囲の全面にシールド３２が設けられているが、シールド３２に開口部３４が形成されているので、この開口部３４からコイル１０で発生した熱が外部に放散される。 The operation of the shield 32 in the inductor 2 will be described. The coil 10 generates heat when energized. Although the shield 32 is provided on the entire surface around the coil 10, since the opening 34 is formed in the shield 32, the heat generated in the coil 10 is dissipated to the outside from the opening 34.
　第２の実施形態に係るインダクタ２は、第１の実施形態に係るインダクタ１と同様の効果を有すると共に、以下の効果も有している。第２の実施形態に係るインダクタ２によれば、コイル１０の周囲の全面にシールド３２が設けられるが、シールド３２に開口部３４を設けることにより、シールド３２の内部から外部への放熱性が向上する。これにより、インダクタ２から基板５に伝わる熱を低減できる。 The inductor 2 according to the second embodiment has the same effects as the inductor 1 according to the first embodiment, and also has the following effects. According to the inductor 2 according to the second embodiment, the shield 32 is provided on the entire surface around the coil 10, but by providing the opening 34 in the shield 32, heat dissipation from the inside of the shield 32 to the outside is improved. To do. Thereby, the heat transferred from the inductor 2 to the substrate 5 can be reduced.
　図６を参照して、第３の実施形態に係るインダクタ３及びＤＣ－ＤＣコンバータ４の基板６について説明する。図６は、第３の実施形態に係るインダクタと基板の一部を示す側断面図である。 With reference to FIG. 6, the substrate 3 of the inductor 3 and the DC-DC converter 4 according to the third embodiment will be described. FIG. 6 is a side sectional view showing a part of the inductor and the substrate according to the third embodiment.
　第３の実施形態に係るインダクタ３は、第１の実施形態に係るインダクタ１と比較すると、ＤＣ－ＤＣコンバータ４の基板にシールド機能を持たせる点が異なる。インダクタ３は、ＤＣ－ＤＣコンバータ４の基板６に実装されるパワーインダクタである。インダクタ３は、コイル１０と、一対の外部電極２０と、シールド３３と、を備えている。 The inductor 3 according to the third embodiment is different from the inductor 1 according to the first embodiment in that a shield function is provided on the substrate of the DC-DC converter 4. The inductor 3 is a power inductor mounted on the substrate 6 of the DC-DC converter 4. The inductor 3 includes a coil 10, a pair of external electrodes 20, and a shield 33.
　導電性を有するシールド３３は、コイル１０の周囲における下面（実装面）側を除く少なくとも一部分に外部電極２０と接触しないように設けられる。シールド３３は、例えば、直方体形状とした場合、直方体の下面を除く五つの面に設けられてもよいし、この５つの面のうちの一部の面に設けられてもよい。図６に示す例の場合、上面にのみシールド３３が設けられている。シールド３３には、接続端子３３ａが形成されている。接続端子３３ａは、後述する基板６のグランドプレーン９に電気的に接続される。接続端子３３ａは、例えば、インダクタ３と基板６にビアをそれぞれ形成し、このビア間を半田で接続することで形成される。 The shield 33 having conductivity is provided so as not to come into contact with the external electrode 20 at least at a part other than the lower surface (mounting surface) side around the coil 10. For example, when the shield 33 has a rectangular parallelepiped shape, the shield 33 may be provided on five surfaces excluding the lower surface of the rectangular parallelepiped, or may be provided on a part of the five surfaces. In the case of the example shown in FIG. 6, the shield 33 is provided only on the upper surface. A connection terminal 33 a is formed on the shield 33. The connection terminal 33a is electrically connected to a ground plane 9 of the substrate 6 described later. The connection terminal 33a is formed, for example, by forming vias in the inductor 3 and the substrate 6 and connecting the vias with solder.
　基板６は、多層配線基板である。基板６の一方の面には、インダクタ３が実装される。この一方の面（実装面）側には、第一層目に配線層７、第二層目に絶縁層８、第三層目にグランドプレーン９（グランド層）が配置されている。第四層目以降には、絶縁層を挟んで電源層やＤＣ－ＤＣコンバータ４の他の電子部品が接続される信号層等が積層されている。 The substrate 6 is a multilayer wiring substrate. The inductor 3 is mounted on one surface of the substrate 6. On the one surface (mounting surface) side, the wiring layer 7 is disposed in the first layer, the insulating layer 8 is disposed in the second layer, and the ground plane 9 (ground layer) is disposed in the third layer. In the fourth and subsequent layers, a power layer and a signal layer to which other electronic components of the DC-DC converter 4 are connected are stacked with an insulating layer interposed therebetween.
　配線層７は、インダクタ３が実装される層である。配線層７は、インダクタ３の一対の外部端子７がそれぞれ接続される配線パターンが形成されている。配線層７の配線パターンは、例えば、銅箔からなる。絶縁層８は、配線層７とグランドプレーン９とを電気的に絶縁する層である。絶縁層８は、例えば、絶縁性の樹脂、誘電体、セラミックス等からなる薄板状である。グランドプレーン９は、例えば、銅箔等からなるグランドパターンが略一面に形成された所謂ベタグランド層である。 The wiring layer 7 is a layer on which the inductor 3 is mounted. The wiring layer 7 is formed with a wiring pattern to which the pair of external terminals 7 of the inductor 3 are connected. The wiring pattern of the wiring layer 7 is made of, for example, copper foil. The insulating layer 8 is a layer that electrically insulates the wiring layer 7 and the ground plane 9. The insulating layer 8 has a thin plate shape made of, for example, insulating resin, dielectric, ceramics, or the like. The ground plane 9 is a so-called solid ground layer in which a ground pattern made of copper foil or the like is formed on substantially one surface.
　インダクタ３におけるシールド３３及び基板６のグランドプレーン９の作用について説明する。コイル１０は、電界のノイズを発生する。このコイル１０の周囲にグランドパターン９に接続された導電性のシールド３３が設けられているので、このシールド３３がコイル１０で発生する電界のノイズを遮蔽する。さらに、コイル１０の下面側にグランドプレーン９が配置されているので、このグランドプレーン９がコイル１０で発生する電界のノイズ（特に、コイル１０から下方に放射されるノイズ）を遮蔽する。なお、コイル１０とグランドプレーン９との間には、ＤＣ－ＤＣコンバータ４のインダクタ３以外の電子部品が接続される信号層が配置されていないので、この信号層や電子部品がコイル１０からの電界のノイズの影響を受けない。 The operation of the shield 33 in the inductor 3 and the ground plane 9 of the substrate 6 will be described. The coil 10 generates electric field noise. Since the conductive shield 33 connected to the ground pattern 9 is provided around the coil 10, the shield 33 shields electric field noise generated in the coil 10. Further, since the ground plane 9 is disposed on the lower surface side of the coil 10, the ground plane 9 shields electric field noise generated by the coil 10 (particularly noise radiated downward from the coil 10). Since no signal layer to which electronic components other than the inductor 3 of the DC-DC converter 4 are connected is arranged between the coil 10 and the ground plane 9, the signal layer and the electronic component are connected from the coil 10. Unaffected by electric field noise.
　この第３の実施形態に係るインダクタ３は、第１の実施形態に係るインダクタ１と同様の効果を有すると共に、以下の効果も有している。第３の実施形態に係るインダクタ３によれば、コイル１０の下面側にグランドプレーン９が配置されているので、グランドプレーン９がシールドとして機能し、グランドプレーン９によりコイル１０で発生する電界のノイズがインダクタ３の外部（特に、基板６の内部）に放射されるのを抑制できる。 The inductor 3 according to the third embodiment has the same effects as the inductor 1 according to the first embodiment, and also has the following effects. According to the inductor 3 according to the third embodiment, since the ground plane 9 is disposed on the lower surface side of the coil 10, the ground plane 9 functions as a shield, and electric field noise generated in the coil 10 by the ground plane 9. Can be prevented from being radiated to the outside of the inductor 3 (particularly, inside the substrate 6).
　以上、本発明の実施の形態について説明したが、本発明は、上記実施形態に限定されるものではなく種々の変形が可能である。例えば、上記実施形態では自動車で用いられるＤＣ－ＤＣコンバータのインダクタに適用したが、他の電源回路に用いられるインダクタ（パワーインダクタ）にも適用でき、自動車以外で用いられるＤＣ－ＤＣコンバータ等にも適用できる。 Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made. For example, in the above embodiment, the present invention is applied to an inductor of a DC-DC converter used in an automobile. However, the present invention can also be applied to an inductor (power inductor) used in other power supply circuits, and also to a DC-DC converter used in other than an automobile. Applicable.
　上記実施形態ではトロイダル型の閉磁路構造のコイルを示したが、ＥＩ型等の他の閉磁路構造のコイルにも適用可能である。また、上記実施形態では直方体形状のシールドを示したが、シールドの形状としては半球形状、円柱形状等の他の形状でもよい。 Although the toroidal type closed magnetic circuit structure coil is shown in the above embodiment, the present invention can also be applied to other closed magnetic circuit structure coils such as the EI type. Moreover, although the rectangular parallelepiped shield was shown in the said embodiment, other shapes, such as a hemispherical shape and a cylindrical shape, may be sufficient as a shape of a shield.
　上記第３の実施形態ではインダクタが実装される多層配線基板の一方の面側の第一層目に配線層、第二層目に絶縁層、第三層目にグランドプレーンが配置される構成としたが、多層配線基板の一方の面側の第一層目にグランドプレーンが配置される構成としてもよい。この構成においては、第一層目にインダクタの外部電極が電気的に接続される配線層（配線パターン）が配置されると共にこの配線層と接触しないようにシールドが電気的に接続されるグランドプレーンが配置される。この構成の場合も、第一層目のグランドプレーンがシールドとして機能する。 In the third embodiment, the wiring layer is disposed on the first layer on one side of the multilayer wiring board on which the inductor is mounted, the insulating layer is disposed on the second layer, and the ground plane is disposed on the third layer. However, the ground plane may be arranged in the first layer on one side of the multilayer wiring board. In this configuration, a wiring layer (wiring pattern) to which the external electrode of the inductor is electrically connected is disposed in the first layer, and a shield is electrically connected so as not to contact the wiring layer. Is placed. Also in this configuration, the first-layer ground plane functions as a shield.
　１，２，３　インダクタ
　４　ＤＣ－ＤＣコンバータ
　５，６　基板
　７　配線層
　８　絶縁層
　９　グランドプレーン
　１０　コイル
　１１　コア
　１２　巻線
　２０　外部電極
　３１，３２，３３　シールド
　３４　開口部 1, 2, 3 Inductor 4 DC- DC converter 5, 6 Substrate 7 Wiring layer 8 Insulating layer 9 Ground plane 10 Coil 11 Core 12 Winding 20 External electrode 31, 32, 33 Shield 34 Opening

Claims (6)

  1. 　電源回路用の基板に実装されるインダクタであって、
    　磁性体からなるコアと巻線とを有する閉磁路構造のコイルと、
    　前記コイルに電気的に接続される外部電極と、
    　前記基板のグランドに電気的に接続され、前記コイルの周囲の少なくとも一部分に前記外部電極と接触しないように設けられる導電性のシールドと、
    　を備えることを特徴とするインダクタ。     An inductor mounted on a power circuit board,
    A coil of a closed magnetic circuit structure having a core made of a magnetic material and a winding;
    An external electrode electrically connected to the coil;
    A conductive shield that is electrically connected to the ground of the substrate and is provided not to contact the external electrode in at least a part of the periphery of the coil;
    An inductor comprising:
  2. 　前記シールドは、前記コイルの周囲の全面に設けられることを特徴とする請求項１に記載のインダクタ。 The inductor according to claim 1, wherein the shield is provided on the entire surface around the coil.
  3. 　前記シールドには、開口部が形成されていることを特徴とする請求項２に記載のインダクタ。 3. The inductor according to claim 2, wherein an opening is formed in the shield.
  4. 　前記基板は、多層配線基板であり、
    　前記インダクタは、前記多層配線基板の一方の面に実装され、
    　前記多層配線基板は、前記一方の面側の第一層目に前記外部電極が電気的に接続される配線層が配置されると共に第二層目の絶縁層を挟んで第三層目に前記シールドが電気的に接続されるグランドプレーンが配置されることを特徴とする請求項１に記載のインダクタ。     The substrate is a multilayer wiring substrate;
    The inductor is mounted on one surface of the multilayer wiring board,
    In the multilayer wiring board, a wiring layer to which the external electrode is electrically connected is arranged on the first layer on the one surface side and the second layer is sandwiched between the insulating layers on the third layer. The inductor according to claim 1, wherein a ground plane to which the shield is electrically connected is disposed.
  5. 　前記基板は、多層配線基板であり、
    　前記インダクタは、前記多層配線基板の一方の面に実装され、
    　前記多層配線基板は、前記一方の面側の第一層目に前記外部電極が電気的に接続される配線層が配置されると共に前記配線層と接触しないように前記シールドが電気的に接続されるグランドプレーンが配置されることを特徴とする請求項１に記載のインダクタ。     The substrate is a multilayer wiring substrate;
    The inductor is mounted on one surface of the multilayer wiring board,
    In the multilayer wiring board, a wiring layer to which the external electrode is electrically connected is disposed on the first layer on the one surface side, and the shield is electrically connected so as not to contact the wiring layer. The inductor according to claim 1, wherein a ground plane is disposed.
  6. 　請求項１～請求項５のいずれか１項に記載のインダクタが実装された基板を備えることを特徴とするＤＣ－ＤＣコンバータ。 A DC-DC converter comprising a substrate on which the inductor according to any one of claims 1 to 5 is mounted.
PCT/JP2016/072310 2015-10-19 2016-07-29 Inductor and dc-dc converter WO2017068831A1 (en)

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