Connection structure

A connection structure includes a circuit board, an insulating member, a housing, and a conductive wire. The insulating member includes a first portion and a second portion. The first portion is fixed to the circuit board. The second portion faces the first portion. The second portion is fixed to the housing. The housing includes a grounded contact. The conductive wire electrically connects the circuit board and the housing while being wound around the insulating member. A shortest distance along a surface of the housing from a position where the conductive wire and the housing are connected to the contact is shorter than a shortest distance along a surface of the housing from the second portion of the insulating member to the contact.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is based on PCT filing PCT/JP2020/033436, filed Sep. 3, 2020, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a connection structure.

BACKGROUND ART

When a power converter such as a switching power supply is mounted on a circuit board, a high-frequency noise current due to a switching operation of the power converter is generated. The high-frequency noise current transmits a place having a low high-frequency impedance. For example, parasitic capacitance of the circuit board has the low high-frequency impedance. The circuit board is connected to a housing grounded for safety by a conductive connection member. For this reason, the high-frequency noise current flows from the circuit board to the ground through the connection member and the housing. The high-frequency noise current flowing out to the ground degrades electromagnetic compatibility (EMC) of an electric apparatus as a common mode current. The high-frequency noise current flowing through the housing induces radiation noise, which degrades the electromagnetic compatibility of the electric apparatus.

For example, in a connection structure between the circuit board and the housing described in Japanese Patent Laying-Open No. 2003433779 (PTL 1), a core of a screw that connects the circuit board and the housing is an insulating material. A tap (screw thread) of the screw has conductivity. For this reason, the connection structure between the circuit board and the housing has a high inductance component. This connection structure between the circuit board and the housing acts as inductance that prevents the high-frequency noise current flowing from the circuit board to the housing, so that unnecessary radiation noise (radiation noise) is reduced.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

In the connection structure between the circuit board and the housing described in PTL 1, the tap (screw thread) having conductivity is fixed to the core of the screw. For this reason, a connection place of the connection structure to the housing is limited to a position where the screw is fixed to the housing. Accordingly, when the position where the screw is fixed to the housing is away from the ground, a distance over which the high-frequency noise current flows along the surface of the housing becomes long.

Solution to Problem

A connection structure of the present disclosure includes a circuit board, an insulating member, a housing, and a conductive wire. The insulating member includes a first portion and a second portion. The first portion is fixed to the circuit board. The second portion faces the first portion. The second portion is fixed to the housing. The housing includes a contact. The contact is grounded. The conductive wire electrically connects the circuit board and the housing while being wound around the insulating member. A shortest distance along a surface of the housing from a position where the conductive wire and the housing are connected to the contact is shorter than a shortest distance along a surface of the housing from the second portion of the insulating member to the contact.

Advantageous Effects of Invention

According to the connection structure of the present disclosure, the shortest distance along the surface of the housing from the position where the conductive wire and the housing are connected to the contact is shorter than the shortest distance along the surface of the housing from the second portion of the insulating member to the contact. Consequently, the distance over which the high-frequency noise current flows along the surface of the housing can be shortened.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments will be described with reference to the drawings. In the following description, the same or corresponding parts are denoted by the same reference numerals, and overlapping description will not be repeated.

First Embodiment

With reference toFIGS.1and2, a configuration of a connection structure100according to a first embodiment will be described below.

As illustrated inFIG.1, connection structure100includes a circuit board1, a housing2, an insulating member3, and a conductive wire4. Circuit board1and housing2are included in an internal structure of an electric apparatus. For example, the electric apparatus is a power conversion device. For example, the power conversion device is an uninterruptible power supply device, a large-capacity air conditioner, or the like. In the first embodiment, circuit board1and housing2face each other. Circuit board1may be accommodated inside housing2.

A power converter11is mounted on circuit board1. For example, power converter11is a switching power supply. Power converter11includes a power conversion semiconductor element (not illustrated). For example, the power conversion semiconductor element is a metal oxide semiconductor field effect transistor (MOSFET) made of silicon (Si). Power converter11is configured to convert a power supply voltage using a switching function of the power conversion semiconductor element. A heat sink (not illustrated) configured to cool the power conversion semiconductor element may be further mounted on circuit board1.

For example, the switching power supply is used as a power supply circuit of the uninterruptible power supply device. In the first embodiment, the uninterruptible power supply device includes the power conversion semiconductor element. For example, circuit board1is used as the power supply circuit of a gate drive circuit configured to drive the power conversion semiconductor element of the uninterruptible power supply device.

Housing2includes a contact21. Contact21is grounded. Contact21is electrically connected to a ground EG. Ground EG is not necessarily disposed at a flat position where circuit board1can be disposed. For example, ground HG may be disposed on a column (not illustrated) of housing2. For this reason, ground EG is not necessarily disposed at a position where insulating member3can be fixed. For example, a material of housing2is metal. Housing2may constitute an outer shape of the electric apparatus.

InFIG.1, four insulating members3and four conductive wires4are disposed between circuit board1and housing2, and at least one insulating member3and at least one conductive wire4may be disposed between circuit board1and housing2. Another connection member may be provided between circuit board1and housing2. For example, the number and positions of insulating member3and conductive wire4may be determined according to a circuit structure of power converter11such as the switching power supply mounted on circuit board1. InFIG.2, one insulating member3and one conductive wire4are disposed between circuit board1and housing2.

As illustrated inFIG.2, insulating member3is sandwiched between circuit board1and housing2. Insulating member3extends from circuit board1toward housing2. Insulating member3extends along an axial direction. In the first embodiment, the axial direction of insulating member3is a direction along a direction from circuit board1toward housing2.

Insulating member3includes a first portion3aand a second portion3b. First portion3ais fixed to circuit board1. A first screw hole3cis made in first portion3a. First screw hole3cconstitutes a female screw. Second portion3bfaces first portion3a. Second portion3bis fixed to housing2. A second screw hole3dis made in second portion3b. Second screw hole3dconstitutes the female screw. Second portion3bis fixed to housing2.

In the first embodiment, insulating member3includes a groove G provided over an entire periphery of the outer periphery. Groove G is provided along a circumferential direction of insulating member3. In the first embodiment, a plurality of grooves G are disposed in insulating member3along the axial direction of insulating member3.

For example, insulating member3is an insulator. The insulator may be a general-purpose product. In the first embodiment, the general-purpose product is a component easily available to general consumers.

Conductive wire4electrically connects circuit board1and housing2while being wound around insulating member3. Conductive wire4is wound along the circumferential direction of insulating member3. In the first embodiment, conductive wire4is wound around insulating member3along groove G. Conductive wire4is configured to be deformable.

Conductive wire4includes a first end4aand a second end4b. First end4ais electrically connected to circuit board1. First end4amay be disposed away from first portion3a. In the first embodiment, first end4ais disposed away from first portion3a. Second end4bis electrically connected to housing2. Second end4bis disposed away from second portion3b. First end4aand second end4bare not fixed to insulating member3.

The shortest distance along a surface of housing2from a position where conductive wire4and housing2are connected to contact21is shorter than the shortest distance along the surface of housing2from second portion3bof insulating member3to contact21. The shortest distance along the surface of housing2is a creepage distance of housing2. The shortest distance from second end4bto contact21along the surface of housing2is shorter than the shortest distance along the surface of housing2from second portion3bof insulating member3to contact21.

Conductive wire4has a winding structure because conductive wire4is wound around the outer periphery of insulating member3. For this reason, conductive wire4has higher self-inductance than the case where conductive wire4extends linearly between circuit board1and housing2. Impedance is proportional to the self-inductance. Accordingly, conductive wire4has high-frequency impedance higher than the case where conductive wire4has the linear shape. In the first embodiment, the high-frequency impedance is impedance in a high frequency region. Thus, a high-frequency noise current can be prevented from propagating from circuit board1to housing2through conductive wire4.

Connection structure100further includes a first fastening body51, a second fastening body52, a third fastening body53, and a fourth fastening body54. The female screw to be screwed with first fastening body51and the female screw to be screwed with third fastening body53are provided in circuit board1. The female screw to be screwed with second fastening body52and the female screw to be screwed with fourth fastening body54are provided in housing2.

First fastening body51fixes first portion3aand circuit board1. First fastening body51is a first screw to be screwed into first screw hole3c. The first screw is a male screw. The first screw may be a general-purpose product. The material of first fastening body51is a magnetic material. For example, first fastening body51is an iron male screw. A first head portion51H of first fastening body51may be exposed to an opposite side to insulating member3with respect to circuit board1. First head portion5111may be exposed to air. When conductive wire4is wound around first fastening body51, the self-impedance of conductive wire4is improved, so that the high-frequency impedance of conductive wire4is improved. When conductive wire4is wound around first fastening body51, heat may be generated in first fastening body51due to iron loss. The heat generated by the iron loss of first fastening body51may be cooled from first head portion51H. The heat generated by the iron loss of first fastening body51may be cooled by either natural air cooling or forced air cooling. Accordingly, quality of connection structure100and the electric apparatus having connection structure100can be improved.

Second fastening body52fixes second portion3band housing2. Second fastening body52is a second screw to be screwed into second screw hole3d. The second screw is the male screw. The second screw may be a general-purpose product. The material of second fastening body52is a magnetic material. For example, second fastening body52is the male screw. When conductive wire4is wound around second fastening body52, the self-impedance of conductive wire4is improved, so that the high-frequency impedance of conductive wire4is improved. When conductive wire4is wound around second fastening body52, the heat may be generated in second fastening body52due to the iron loss. The heat generated by the iron loss of second fastening body52may be radiated to housing2. The heat radiated to housing2is radiated to the outside of housing2. Thus, second fastening body52is effectively cooled. Consequently, the quality of connection structure100and the electric apparatus having connection structure100can be improved.

Third fastening body53fixes first end4aand circuit board1. Third fastening body53is a third screw to be screwed into the female screw provided on circuit board1. The third screw is the male screw. The third screw may be a general-purpose product. The material of third fastening body53may be a magnetic material. For example, third fastening body53is the iron male screw.

Fourth fastening body54fixes second end4band housing2. Fourth fastening body54is a fourth screw to be screwed into the female screw provided in housing2. The fourth screw is the male screw. The fourth screw may be a general-purpose product. The material of the fourth fastening body54may be a magnetic material. For example, fourth fastening body54is the iron male screw.

With reference toFIG.2, the high-frequency noise current flowing through connection structure100will be described below.

Circuit board1has stray capacitance parasitic capacitance) connected to the power conversion semiconductor element of power converter11. When the power conversion semiconductor element such as the metal oxide semiconductor field effect transistor of power converter11performs a switching operation, a steep voltage fluctuation is generated. When the voltage fluctuation is applied to the stray capacitance, the high-frequency noise current is generated. The high-frequency noise current is proportional to time variation of the voltage and a stray capacitance value.

The high-frequency noise current selectively propagates through a place having the low high-frequency impedance. Thus, the high-frequency noise current flows out from power converter11such as the switching power supply. For example, the capacitance between the windings of the transformer in the switching power supply has the low high-frequency impedance. For example, the stray capacitance between the circuit patterns of circuit board1has the low high-frequency impedance. For example, the stray capacitance between the power conversion semiconductor element and a heat sink (not illustrated) has the low high-frequency impedance.

The high-frequency noise current flowing out of power converter11reaches conductive wire4through the place having the low high-frequency impedance. The high-frequency noise current can propagate to housing2through conductive wire4. In order to prevent the propagation of the high-frequency noise current to housing2, conductive wire4needs to have the high high-frequency impedance. In the first embodiment, because conductive wire4is wound around insulating member3, conductive wire4has the high high-frequency impedance.

Effects of the first embodiment will be described below.

According to connection structure100of the first embodiment, as illustrated inFIG.2, the shortest distance along the surface of housing2from the position where conductive wire4and housing2are connected to contact21is shorter than the shortest distance along the surface of housing2from second portion3bof insulating member3to contact21. For this reason, the distance that the high-frequency noise current flows on the surface of housing2can be shortened as compared with the case where conductive wire4is fixed to housing2at the posit n of insulating member3.

Thus, the high-frequency noise current can be prevented from circulating inside housing2. When the high-frequency noise current circulates inside housing2, a current loop is formed to generate radiation noise. According to connection structure100of the first embodiment, the high frequency noise current can be prevented from circulating inside housing2, so that the generation of the radiation noise can be prevented. Accordingly, electromagnetic compatibility (EMC) of the electric apparatus having connection structure100is improved.

As illustrated inFIG.2, connection structure100further includes first fastening body51, second fastening body52, third fastening body53, and fourth fastening body54. For this reason, circuit board1, housing2, insulating member3, and conductive wire4can be fixed by the fastening body.

As illustrated inFIG.2, first fastening body51is the first screw to be screwed into first screw hole3c. Second fastening body52is a second screw to be screwed into second screw hole3d. The first screw and the second screw are male screws. For this reason, the male screw that is a general-purpose product can be used for first fastening body51and second fastening body52. The insulator that is a general-purpose product can be used as insulating member3. Accordingly, the manufacturing cost of connection structure100can be reduced as compared with the case where connection structure100includes a conductive thread, an insulating core material, and a conductive tap spirally wound around the core material.

As illustrated inFIG.2, insulating member3includes groove G provided over the entire circumference of the outer periphery. For this reason, the creepage distance of insulating member3is longer than the case where groove G is not provided in insulating member3. Accordingly, the high-frequency noise current can be prevented from propagating from circuit board1to housing2along the surface of insulating member3. Consequently, the generation of the radiation noise can be prevented.

As illustrated inFIG.2, conductive wire4is configured to be deformable. For this reason, the position where circuit board1and housing2are electrically connected is not limited to the position of insulating member3. Accordingly, the degree of freedom in design is improved.

Second Embodiment

With reference toFIG.3, a configuration of connection structure100according to a second embodiment will be described below. The second embodiment has the same configuration and effect as those of the first embodiment described above unless otherwise specified. Consequently, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will not be repeated.

As illustrated inFIG.3, conductive wire4of the second embodiment is wound around groove G in a multiple manner. Conductive wire4is wound around groove G in the multiple manner along the circumferential direction of insulating member3. For example, conductive wire4is wound in a triple manner along the circumferential direction of the insulating member of groove G. Conductive wire4constitutes a winding structure laminated in multiple layers.

Effects of the first embodiment will be described below.

According to connection structure100of the second embodiment, as illustrated inFIG.3, conductive wire4is wound around groove G in the multiple manner. For this reason, conductive wire4has the higher self-inductance than the case where conductive wire4is singly wound around groove G. Accordingly, conductive wire4has the higher high-frequency impedance than the case where conductive wire4is singly wound around groove G. Accordingly, the high-frequency noise current can be prevented from flowing from circuit board1to housing2through conductive wire4. Thus, electromagnetic environmental compatibility of the electric apparatus having connection structure100is improved.

As illustrated inFIG.3, conductive wire4is wound around groove G in the multiple manner. For this reason, conductive wire4having a stable potential close to ground EG can be wound around insulating member3in a multiple manner. Accordingly, the generation of the high-frequency noise current due to the part of conductive wire4connected to housing2and the stray capacitance of second fastening body52can be prevented. For example, the potential of circuit board1can be displaced by a potential fluctuation during a switching operation of power converter11such as the switching power supply. However, the stray capacitance of the part of conductive wire4connected to circuit board1and the stray capacitance of first fastening body51are smaller than the stray capacitance of the part of conductive wire4connected to housing2and the stray capacitance of second fastening body52. For this reason, the impedance of the part of conductive wire4connected to circuit board1and the impedance of first fastening body51are higher than the impedance of the part of conductive wire4connected to housing2and the impedance of second fastening body52. Accordingly, the generation of the high-frequency noise current can be prevented in circuit board1. Consequently, the electromagnetic compatibility of the electric apparatus having connection structure100is improved.

Third Embodiment

With reference toFIG.4, a configuration of connection structure100according to a third embodiment will be described below. The third embodiment has the same configuration and effect as those of the first embodiment described above unless otherwise specified. Consequently, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will not be repeated.

As illustrated inFIG.4, connection structure100of the third embodiment further includes at least one coupling body6. Insulating member3includes a plurality of insulating portions30. The plurality of insulating portions30are laminated from circuit board1toward housing2. The plurality of insulating portions30are laminated along the axial direction of insulating member3. The plurality of insulating portions30are arranged in series. Adjacent insulating portions30among the plurality of insulating portions30are connected by at least one coupling body6. For example, each of the plurality of insulating portions30is the insulator that is a general-purpose product.

Each of the plurality of insulating portions30includes a plurality of grooves G provided over the entire circumference of the outer periphery. The plurality of insulating portions30may have the same structure.

In the third embodiment, the plurality of insulating portions30include a first insulating portion31, a central insulating portion32, and a second insulating portion33. First insulating portion31, central insulating portion32, and second insulating portion33are sequentially laminated from circuit board1toward housing2. First insulating portion31is fixed to circuit board1. First insulating portion31is connected to central insulating portion32by coupling body6. Central insulating portion32is sandwiched between first insulating portion31and second insulating portion33. Second insulating portion33is fixed to housing2. Second insulating portion33is connected to central insulating portion32by coupling body6. First portion3ais disposed in first insulating portion31. Second portion3bis disposed in second insulating portion33.

The at least one coupling body6is disposed inside the plurality of insulating portions30. Coupling body6connects adjacent insulating portions30to each other. Coupling body6is embedded across adjacent insulating portions30. Coupling body6extends along the axial direction of insulating member3inside adjacent insulating portions30. In the third embodiment, because three insulating portions30are disposed, two coupling bodies6are disposed.

The at least one coupling body6is a magnetic material. Coupling body6may be a general-purpose product. For example, coupling body6may be an iron male screw. The material of coupling body6may be ferrite or the like that is a ferromagnetic material.

Conductive wire4is wound around the plurality of insulating portions30around at least one coupling body6. Conductive wire4is wound around the plurality of insulating portions30across the plurality of insulating portions30. Conductive wire4is wound around each of the plurality of grooves G provided in each of the plurality of insulating portions30.

InFIG.4, the winding is wound around insulating portion30in a single form, but the method for winding conductive wire4is not limited to the single form. As will be described later in a fourth embodiment and a fifth embodiment, conductive wire4may be wound in a multiple manner.

Effects of the first embodiment will be described below.

According to connection structure100of the third embodiment, as illustrated inFIG.4, insulating member3includes the plurality of insulating portions30. The plurality of insulating portions30are laminated from circuit board1toward housing2. For this reason, the axial dimension of insulating member3can be changed more easily than the case where insulating member3is made of only one member. Accordingly, the distance between circuit board1and housing2can be easily changed, so that the degree of freedom in designing connection structure100is improved.

As illustrated inFIG.4, insulating member3includes the plurality of insulating portions30. Each of the plurality of insulating portions30may be the insulator that is a general-purpose product. For this reason, the manufacturing cost of connection structure100can be reduced.

As illustrated inFIG.4, connection structure100includes at least one coupling body6. Coupling body6is a magnetic material. Conductive wire4is wound around the plurality of insulating portions30around at least one coupling body6. For this reason, coupling body6is surrounded by a winding structure constituted by conductive wire4. Thus, coupling body6adds a magnetic path inside the winding structure. Accordingly, the self-impedance of conductive wire4increases. Accordingly, the high-frequency noise current can be prevented from flowing from circuit board1to housing2through conductive wire4. Thus, electromagnetic environmental compatibility of the electric apparatus having connection structure100is improved.

Fourth Embodiment

With reference toFIG.5, a configuration of connection structure100according to a fourth embodiment will be described below. The fourth embodiment has the same configuration and effect as those of the third embodiment described above unless otherwise specified. Consequently, the same components as those in the third embodiment are denoted by the same reference numerals, and the description thereof will not be repeated.

As illustrated inFIG.5, in the fourth embodiment, conductive wire4is wound around at least one of the plurality of insulating portions30in a multiple manner. Conductive wire4is multiply wound around groove G of at least one insulating portion30among the plurality of insulating portions30in a multiple manner. Density of conductive wire4wound around insulating portion30may be appropriately adjusted.

The density of conductive wire4wound around central insulating portion32may be higher than the density of conductive wire4wound around first insulating portion31and the density of conductive wire4wound around second insulating portion33. Conductive wire4may be wound around central insulating portion32by concentrated winding. In the fourth embodiment, conductive wire4being wound around central insulating portion32by concentrated winding means that conductive wire4is wound around central insulating portion32more than first insulating portion.31and second insulating portion33. Conductive wire4may be wound around insulating portion30disposed at the center in the axial direction of insulating member3among the plurality of insulating portions30by concentrated winding.

Effects of the first embodiment will be described below.

According to connection structure100of the fourth embodiment, as illustrated inFIG.5, conductive wire4is wound around at least one of the plurality of insulating portions30in a multiple manner. For this reason, the density of conductive wire4wound around insulating portion30can be appropriately adjusted. Accordingly, conductive wire4can be wound around insulating portion30disposed at the center in the axial direction of insulating member3among the plurality of insulating portions30by concentrated winding. Insulating portion30disposed at the center in the axial direction of insulating member3has higher workability than insulating portion30disposed at the end in the axial direction of insulating member3. As a result, the workability winding conductive wire4around insulating portion30is improved, so that assemblability of connection structure100is improved. Accordingly, the manufacturing cost of connection structure100can be reduced.

Fifth Embodiment

With reference toFIG.6, a configuration of connection structure100according to a fifth embodiment will be described below. The fifth embodiment has the same configuration and effect as those of the third embodiment described above unless otherwise specified. Consequently, the same components as those in the third embodiment are denoted by the same reference numerals, and the description thereof will not be repeated.

As illustrated inFIG.6, conductive wire4of the fifth embodiment is wound around the plurality of insulating portions30in a multiple manner around at least one coupling body6. Conductive wire4is wound around the plurality of insulating portions30along the circumferential direction of the plurality of insulating portions30in a multiple manner around the at least one coupling body6.

Effects of the first embodiment will be described below.

According to connection structure100of the fifth embodiment, conductive wire4is wound around the plurality of insulating portions30in a multiple manner around at least one coupling body6. For this reason, the leakage magnetic flux generated from conductive wire4is concentrated around coupling body6. Accordingly, the leakage magnetic flux generated from conductive wire4forms a magnetic flux loop around coupling body6. When the magnetic flux loop reaches circuit board1, a malfunction of an electronic component (not illustrated) mounted on circuit board1may be induced, so that the malfunction may be generated in the electric apparatus in which circuit board1is incorporated. According to the fifth embodiment, the magnetic flux loop of the leakage magnetic flux is formed around coupling body6, so that the magnetic flux loop can be prevented from reaching circuit board1. Accordingly, the malfunction of circuit board1can be prevented. Consequently, the reliability of the electric apparatus including circuit board1of connection structure100is improved.

It should be considered that the disclosed embodiments are an example in all respects and not restrictive. The scope of the present disclosure is defined by not the description above, but the claims, and it is intended that all modifications within the meaning and scope of the claims and their equivalents are included in the present invention.

REFERENCE SIGNS LIST