Transformer and DC-DC converter having the same

Abstract

Provided are a transformer and a DC-DC converter having the transformer. The novel transformer (10) comprises: a first coil (30); at least one second coil (40, 45), the at least one second coil being magnetically coupled to the first coil; and an electrically insulating holder (20). The first coil (30) and the at least one second coil (40, 45) face each other with the holder (20) sandwiched therebetween. The holder has at least one through hole (80) at a portion (21, 23) sandwiched between the first coil and the at least one second coil. The transformer (10) further comprises at least one electrically insulating heat radiation member (70, 170), the at least one heat radiation member being arranged in the at least one through hole and in contact with the first coil and the at least one second coil. The heat radiation member has a higher thermal conductivity than that of the holder.

Description

Technical Field

[0001] The present disclosure relates to a transformer and a direct current-to-direct current (DC-DC) converter having the same. The transformer includes a first coil and a second coil that are magnetically coupled. Background Art

[0002] A known transformer includes a holder having a cylindrical portion and first to fourth plate-shaped portions radially protruding from the cylindrical portion. The known transformer also includes a primary coil wound around the cylindrical portion between the first plate-shaped portion and the second plate-shaped portion. The known transformer also includes a secondary coil wound around the cylindrical portion while contacting a main surface of the second plate-shaped portion opposite to a surface facing the first plate-shaped portion.

[0003] However, in the known transformer, although the primary coil (ie, the first coil) and the secondary coil (ie, the second coil) are insulated from each other by the holder, the secondary coil is arranged inside the primary coil. As a result, heat radiation from the secondary coil is insufficient. Summary of the invention

[0004] Therefore, one aspect of the present disclosure provides a novel transformer (10), the transformer (10) comprising: a first coil (30); at least one second coil (40, 45), the at least one second coil (40, 45) being magnetically coupled to the first coil; and an electrically insulating holder (20). The first coil (30) and the at least one second coil face each other with the holder sandwiched therebetween. The holder has at least one through hole (80) at a portion (21, 23) sandwiched between the first coil and the at least one second coil. The transformer further comprises at least one heat radiation member (70, 170), the at least one heat radiation member (70, 170) being disposed in the at least one through hole and in contact with the first coil and the at least one second coil. The electrically insulating heat radiation member has a higher thermal conductivity than the holder.

[0005] Therefore, according to one aspect of the above structure, the first coil and the second coil are magnetically coupled in the transformer. The first coil and the second coil are opposite to each other with an electrically insulating holder sandwiched therebetween. In addition, due to the difference in heat radiation in the transformer and the value of the current flowing therein, the temperature of each of the first coil and the second coil is different from each other. In addition, one of the coils may be a primary coil and the other coil may be a secondary coil, and vice versa.

[0006] In addition, a through hole is formed in a portion of the retaining member between the first coil and the second coil. In addition, an insulating heat radiation member having insulating properties and a thermal conductivity higher than that of the retaining member is arranged in the through hole and is in contact with the first coil and the second coil. Therefore, since the heat radiation member has insulating properties, the first coil and the second coil can be insulated from each other by the heat radiation member. In addition, heat conduction is performed between the first coil and the second coil by the heat radiation member having a thermal conductivity higher than that of the retaining member. Therefore, heat can be effectively conducted from one of the first coil and the second coil having a higher temperature to the other of the first coil and the second coil having a lower temperature. As a result, the heat radiation of the coils in the transformer can be improved while ensuring the insulation between these coils.

[0007] Another aspect of the present disclosure provides a novel DC-DC converter, comprising: a heat sink; a transformer as described above; and a converter holder, the holder fixing at least one core to the heat sink. The first coil is arranged between the paired second coils. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Thus, a more complete appreciation of the present disclosure and many of its attendant advantages may be more readily obtained by reference to the following detailed description, so that substantially the same may be better understood when considered in conjunction with the accompanying drawings, wherein:

[0009] Figure 1 is an exploded perspective view showing a transformer according to one embodiment of the present disclosure;

[0010] Figure 2 It is shown Figure 1 A cross-sectional view of a transformer;

[0011] Figure 3 is a cross-sectional view showing a transformer and a heat sink according to one embodiment of the present disclosure;

[0012] Figure 4 is a schematic diagram showing a first heat radiation member and its peripheral structure according to one embodiment of the present disclosure;

[0013] Figure 5 It is shown based on Figure 4 A schematic diagram of a modified example prepared by using the first heat radiation member and its surrounding structure as shown;

[0014] Figure 6 It is shown based on Figure 4 A schematic diagram of another variation of the first heat radiation member and its peripheral structure shown in FIG.

[0015] Figure 7 It is shown that by changing Figure 4Schematic diagram of another variation example prepared by using the first heat radiation component and its surrounding structure as shown. DETAILED DESCRIPTION

[0016] As described in Japanese Patent No. 5522074 (JP-5522074-B), although the primary coil (i.e., the first coil) and the secondary coil (i.e., the second coil) of the known transformer are insulated from each other by a retainer, the secondary coil is arranged inside the primary coil. As a result, heat radiation from the secondary coil is insufficient. Therefore, the present disclosure is made to solve the above-mentioned problem, and its object is to improve heat radiation from the first coil and the second coil constituting the magnetic coupling of the transformer while ensuring insulation therebetween.

[0017] Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views thereof, and reference Figure 1 1 and applicable drawings, an exemplary transformer used in a buck (step-down) type DC-DC converter will be described as one embodiment of the present disclosure.

[0018] Specifically, if Figure 1 and Figure 2 As shown, the transformer 10 includes a cylindrical bobbin 20, a primary coil 30 and a pair of secondary coils 40, 45. The transformer 10 also includes a housing 50 and a pair of cores 60, 65, etc. In the following, the axial direction of the cylindrical bobbin 20 is referred to as an upward direction or a downward direction, corresponding to Figure 1 and Figure 2 The upward direction and the downward direction of each of .

[0019] More specifically, the bobbin 20 (ie, the holder) is made of a resin having insulating properties to serve as an insulator. The bobbin 20 has a cylindrical portion 25, first to third flanges 21 to 23, a peripheral wall portion 27, and the like.

[0020] The cylindrical portion 25 has a cylindrical or elliptical tubular shape. The first to third flanges 21 to 23 protrude from the cylindrical portion 25. Each of the first to third flanges 21 to 23 is in a circular plate shape having approximately the same size. Each of the first to third flanges 21 to 23 is arranged to be approximately parallel to each other and approximately perpendicular to the cylindrical portion 25. However, the cylindrical portion 25 may have a polygonal tubular shape.

[0021] The peripheral wall portion 27 extends downward from the outer edge of the first flange 21. More specifically, the peripheral wall portion 27 extends downward from the circumferential portion of the first flange 21. Therefore, the annular space accommodating the lower secondary coil 40 is partitioned by the cylindrical portion 25, the first flange 21 and the peripheral wall portion 27.

[0022] A first gap corresponding to the thickness (vertical height) of the coil winding of the primary coil 30 is formed between the first flange 21 and the second flange 22. Similarly, a second gap corresponding to the thickness (vertical height) of the coil winding of the primary coil 30 is formed between the second flange 22 and the third flange 23.

[0023] That is, in each of the first gap and the second gap, the coil winding of the primary coil 30 is wound around the cylindrical portion 25 in a spiral shape, respectively. Here, for example, the cross-section of the element of the coil winding is rectangular. In addition, the coil winding wound in the first gap and the coil winding wound in the second gap are connected to each other near the cylindrical portion 25. That is, the primary coil 30 (i.e., the first coil) constitutes a two-layer structure. The surface of the element of the coil winding is covered with an insulating film made of enamel, for example.

[0024] In addition, the primary coil 30 is substantially completely located within the relative range of the first flange 21 and the second flange 22 relative to each other and the relative range of the second flange 22 and the third flange 23 relative to each other. That is, the primary coil 30 is arranged from the inner edge (i.e., the bottom) of the first flange 21 to the third flange 23 to the outer edge (i.e., the top) thereof.

[0025] Furthermore, a pair of secondary coils 40, 45 (ie, a pair of second coils) is employed in the transformer 10. Each of the secondary coils 40, 45 is composed of a metal plate having a given thickness and a substantially U-shape.

[0026] More specifically, the lower secondary coil 40 includes: a main body 40b, which is C-shaped when viewed vertically; and a pair of arms 40a (not shown), 40c, which extend from both ends of the main body 40b. The main body 40b has approximately the same size as the first flange 21. The main body 40b is accommodated in a space separated by the cylindrical portion 25, the first flange 21 and the peripheral wall portion 27. More specifically, the upper surface of the main body 40b is configured to contact the lower surface of the first flange 21. However, the upper surface of the main body 40b is not necessarily configured to contact the lower surface of the first flange 21.

[0027] In addition, the upper secondary coil 45 also includes a main body 45b, which is C-shaped when viewed vertically; and a pair of arms 45a, 45b, which extend from both ends of the main body 45b. The main body 45b has approximately the same size as the third flange 23. The lower surface of the main body 45b is configured to contact the upper surface of the third flange 23. However, the lower surface of the main body 45b is not necessarily configured to contact the upper surface of the third flange 23, and can be configured to be separated from the upper surface of the third flange 23.

[0028] Furthermore, the arm portions 40 a , 45 a are connected to each other to allow current to flow into the lower secondary coil 40 and the upper secondary coil 45 in a given direction.

[0029] Furthermore, the lower layer portion of the primary coil 30 and the lower secondary coil 40 are opposed to each other across the first flange 21 (i.e., a portion of the bobbin 20). More specifically, the lower layer portion of the primary coil 30 and the lower secondary coil 40 are opposed to each other across substantially the entire first flange 21. That is, the first flange 21 as a whole occupies a relative range in which the lower layer portion of the primary coil 30 and the lower secondary coil 40 face each other.

[0030] Similarly, the upper portion of the primary coil 30 and the upper secondary coil 45 are opposite to each other across the third flange 23 (i.e., a portion of the bobbin 20). More specifically, the upper portion of the primary coil 30 and the upper secondary coil 45 are opposite to each other across substantially the entire third flange 23. That is, the third flange 23 as a whole occupies a relative range in which the upper portion of the primary coil 30 and the upper secondary coil 45 face each other.

[0031] In addition, the housing 50 is cylindrical (e.g., an elliptical tubular state) and is made of an insulating material such as a resin (i.e., a resin having insulating properties). More specifically, the housing 50 has a size corresponding to each of the main body portions 40b, 45b of the corresponding secondary coils 40, 45. Therefore, the main body portions 40b, 45b, the bobbin 20, and the primary coil 30 are accommodated in the housing 50. In addition, the housing 50 includes a plurality of claw portions 50a extending alternately from its upper and lower ends. Therefore, the main body portions 40b, 45b are engaged by these claw portions 50a, respectively. However, the housing 50 may be polygonal tubular.

[0032] In addition, the lower core 60 is made of a magnetic material. The lower core 60 includes a main body 61, a cylindrical main leg 62 and a side leg 63. The main body 61 is in the shape of a rectangular tube. The main leg 62 is cylindrical (or elliptical cylindrical) and extends from the center of the main body 61. The side leg 63 extends from both ends of the main body 61 in the same direction as the main leg 62. Therefore, the main leg 62 is inserted into the cylindrical portion 25 of the winding tube 20. However, as long as the main leg 62 can be accommodated in the cylindrical portion 25, the main leg 62 can be in any shape. For example, the main leg 62 can be in the shape of a polygonal column.

[0033] In addition, the upper core portion 65 is also made of a magnetic material and is configured to be substantially symmetrical with the lower core portion 60. More specifically, the upper core portion 65 includes a main body 66, a cylindrical portion 67, and a side wall portion 68. The cylindrical portion 67 is inserted into the cylindrical portion 25 of the bobbin 20. The main leg portion 62 and the cylindrical portion 67 as described above are in contact with each other. The side leg portion 63 and the side wall portion 68 as described above are also in contact with each other.

[0034] like Figure 3 As shown, the lower core 60 and the upper core 65 are temporarily fixed by the tape 69 while roughly sandwiching the bobbin 20, the primary coil 30, the secondary coils 40, 45, and the housing 50. That is, the paired cores 60, 65 surround the primary coil 30 and the secondary coils 40, 45. Therefore, the primary coil 30 and the paired secondary coils 40, 45 are magnetically coupled to each other. The transformer 10 temporarily fixed by the tape 69 in this way is mounted and fixed on the DC-DC converter.

[0035] Furthermore, the paired cores 60, 65 are fixed to the heat sink HS provided in the DC-DC converter by the converter holder HL. However, since the primary coil 30 is vertically arranged inside the paired secondary coils 40, 45 in the transformer 10, the temperature of the primary coil 30 tends to be higher than the temperature of the paired secondary coils 40, 45. As a result, heat radiation from the primary coil 30 becomes insufficient.

[0036] In view of this, according to this embodiment, Figure 4 As shown, the transformer 10 includes a plurality of first heat radiating members 70 that collectively and effectively conduct heat from the primary coil 30 to the pair of secondary coils 40 , 45 .

[0037] Right now, Figure 4 is a schematic diagram showing the first heat radiation member 70 and its peripheral structure. As shown in the figure, a plurality of through holes 80 are formed in each of the first flange 21 and the third flange 23, which are located between the primary coil 30 in the bobbin 20 and one of the paired secondary coils 40, 45. The through hole 80 is rectangular in shape. Each through hole 80 is formed within the relative range of the corresponding one of the primary coil 30 and the paired secondary coils 40, 45, which are opposite to each other. Specifically, four through holes 80 are formed in each flange 21, 23 at approximately the same intervals. In addition, in the flanges 21, 23, the inner peripheral wall 81 of the through hole 80 partially becomes thinner than the portion 82 that is further outward than the inner peripheral wall 81. That is, the portion where the through hole 80 is formed in each flange 21, 23 is thinned by including a stepped or inclined cross section.

[0038] In addition, the first heat radiating members 70 are arranged inside the flanges 21, 23 rather than protruding from the flanges 21, 23. Each of the first heat radiating members 70 includes a first performance member 71 and a second performance member 72.

[0039] More specifically, the first performance member 71 is in the shape of a rectangular sheet made of a heat-resistant insulating material (e.g., a heat-resistant insulating resin). When viewed from above, each first performance member 71 has a shape and size formed and calculated by combining a through hole 80 with an inner peripheral wall 81. Each first performance member 71 contacts one of the paired secondary coils 40, 45.

[0040] In addition, the total thickness of the first performance member 71 and the inner peripheral wall 81 is substantially equal to the thickness of the portion 82 of the first flange 21 that is further outward than the inner peripheral wall 81. Therefore, the first performance member 71 is fitted into the hollowed-out portion (i.e., recess) formed by the inner peripheral wall 81 in the first flange 21. Therefore, the lower surface (and / or upper surface) of the flange 21 (23) and the lower surface (and / or upper surface) of the first performance member 71 coincide with each other. Therefore, the outer edge of the first performance member 71 is laminated on the thinner portion 21a (31a) of the flange 51 of the holder 20 (e.g., the bobbin) while being fitted to the inner peripheral wall 81, thereby completely covering the through hole 80. That is, each first performance component 71 has an outer edge that is completely in contact with the thinner portion 21a (31a) of each through hole 80 of the flanges 21, 23 along a relative direction (i.e., the thickness direction of the flange), which is the relative direction of each of the primary coil 30 and the paired secondary coils 40, 45.

[0041] In addition, each second performance member 72 is in the shape of a rectangular tube (or a rectangular sheet made of a heat-resistant and high thermal conductivity insulating material (e.g., silicone rubber, a high thermal conductivity resin, etc.)). More specifically, each second performance member 72 has a higher thermal conductivity than each bobbin 20 and each first performance member 71. The second performance member 72 is in contact with the primary coil 30. The first performance member 71 and the second performance member 72 are integrated with each other. In addition, the thermal conductivity of the first heat radiation member 70, which is the sum of the thermal conductivities of the first performance member 71 and the second performance member 72, is higher than the thermal conductivity of the bobbin 20.

[0042] In addition, when viewed from above, the second performance member 72 has a shape substantially the same as or similar to the through hole 80 (i.e., a shape fitted to the through hole 80). The first heat radiation member 70 is in contact with the primary coil 30 and the secondary coil 40 (45). In addition, the first heat radiation member 70 is placed to be compressed by the primary coil 30 and the secondary coil 40 (45).

[0043] Furthermore, the first performance member 71 is inserted into the through hole 80. Meanwhile, the second performance member 72 completely covers the first performance member 71 and the through hole 80. However, since the first performance member 71 can insulate each of the secondary coils 40, 45 from the primary coil 30, the second performance member 72 does not require insulation performance.

[0044] In addition, a plurality of second heat radiation members 75 are arranged between the lower secondary coil 40 and the lower core 60, and are in contact with both the lower secondary coil 40 and the lower core 60. Each second heat radiation member 75 has an insulating property and a higher thermal conductivity than the thermal conductivity of the bobbin 20. Each second heat radiation member 75 is in a rectangular tube shape or a rectangular sheet shape. Therefore, each second heat radiation member 75 is formed to be positioned within a range where the lower secondary coil 40 and the lower core 60 face each other. More specifically, four second heat radiation members 75 are arranged at substantially the same intervals relative to the lower secondary coil 40.

[0045] Now, various advantages obtained by the embodiment described above are described below.

[0046] First, according to one aspect of the present disclosure, in the bobbin 20, a through hole 80 is formed in a portion between the primary coil 30 and each of the secondary coils 40, 45 (i.e., the flanges 21, 23). In the through hole 80, a first heat radiation member 70 having a higher thermal conductivity than that of the bobbin 20 is configured to contact the primary coil 30 and one of the paired secondary coils 40, 45. Since it has insulating properties, the first heat radiation member 70 can insulate the primary coil 30 and each of the secondary coils 40, 45 from each other. In addition, heat is conducted between the primary coil 30 and each of the secondary coils 40, 45 through the first heat radiation member 70 having a higher thermal conductivity than that of the bobbin 20. Therefore, heat can be effectively conducted from one of the primary coil 30 and the secondary coil 40 (45) having a higher temperature to the other of the primary coil 30 and the secondary coil 40 (45) having a lower temperature. Therefore, heat radiation from these coils can be improved while ensuring insulation between these coils.

[0047] In addition, according to one aspect of the present disclosure, the through hole 80 is formed to be located within a relative range in which the primary coil 30 and one of the paired secondary coils 40, 45 face each other. Therefore, the through hole 80 can be formed in the bobbin 20 without expanding the bobbin 20 to the outside of the relative range. In addition, the first heat radiation member 70 is arranged within the relative range. Therefore, no additional space is required outside the relative range to accommodate the first heat radiation member 70. Therefore, the first heat radiation member 70 arranged in the transformer 10 does not expand the size of the transformer 10, and the compact size of the transformer 10 can be maintained.

[0048] Furthermore, according to one aspect of the present disclosure, the first heat radiation member 70 has an outer edge that is completely in contact with the inner peripheral wall 81 of the through hole 80 formed in each of the flanges 21, 23 in the opposite direction, which is the direction opposite to the primary coil 30 and one of the secondary coils 40, 45. By such a configuration, the through hole 80 located between the primary coil 30 and each of the secondary coils 40, 45 can be completely occupied by the first heat radiation member 70. Therefore, the insulation performance and thermal conductivity between the primary coil 30 and each of the secondary coils 40, 45 can be effectively improved. Furthermore, in the present embodiment, since the creepage distance (i.e., length) of the through hole 80 along the surface of each of the flanges 21, 23 can be extended, the creepage discharge that is usually generated along the surface can be reduced or suppressed.

[0049] Furthermore, according to one aspect of the present disclosure, since the first heat radiation member 70 completely covers the through hole 80, the through hole 80 disposed between the primary coil 30 and each of the secondary coils 40, 45 may be completely occupied by the first heat radiation member 70. Therefore, the insulation performance and thermal conductivity between the primary coil 30 and each of the secondary coils 40, 45 may be effectively improved.

[0050] Furthermore, according to one aspect of the present disclosure, each of the flanges 21, 23 has a portion 21a (31a) thinner than a portion 82 of an outer side of the through hole 80 around the through hole 80, so that the outer edge of the first heat radiation member 70 can be stacked on the thinner portion 21a (31a) of the flange 21 (23) while being fitted to the inner peripheral wall 81. According to such a configuration, where the thinner portion 21a (31a) of the flange 21 (23) and the first heat radiation member 70 fitted to the inner peripheral wall 81 are stacked on each other, an increase in the total thickness of each of the flanges 21, 23 and the first heat radiation member 70 can be suppressed. Therefore, the insulation between the primary coil 30 and each of the secondary coils 40, 45 can be effectively improved while suppressing an increase in the size of the transformer 10.

[0051] Furthermore, according to one aspect of the present disclosure, the first performance member 71 having an insulating property can insulate the primary coil 30 and each of the secondary coils 40, 45 from each other. Furthermore, heat conduction between the primary coil 30 and each of the secondary coils 40, 45 can be effectively performed by the second performance member 72 having a higher thermal conductivity than the bobbin 20 and the first performance member 71. Furthermore, by assigning the electrical insulation function and the thermal conduction function performed by the first heat radiation member 70 to the first performance member 71 and the second performance member 72, respectively, the first heat radiation member 70 can be easily manufactured by using a common material.

[0052] Furthermore, according to one aspect of the present disclosure, since the first performance member 71 is inserted into the through hole 80, heat conduction between the primary coil 30 and each of the secondary coils 40, 45 can be effectively performed via the through hole 80 and the first performance member 71. Furthermore, since the second performance member 72 completely covers the first performance member 71 and the through hole 80, the second performance member 72 can enhance electrical insulation between the primary coil 30 and each of the secondary coils 40, 45.

[0053] Furthermore, according to one aspect of the present disclosure, the pair of cores 60, 65 are arranged to surround the primary coil 30 and the pair of secondary coils 40, 45. Specifically, the second heat radiation member 75 is arranged between the lower secondary coil 40 and the lower core 60, the second heat radiation member 75 having an insulating property and a higher thermal conductivity than the thermal conductivity of the bobbin 20, and the second heat radiation member 75 is in contact with the lower secondary coil 40 and the lower core 60. Since the second heat radiation member 75 has an insulating property, the second heat radiation member 75 can insulate the lower secondary coil 40 and the lower core 60 from each other. Furthermore, the second heat radiation member 75 having a higher thermal conductivity than the thermal conductivity of the bobbin 20 effectively performs heat conduction between the lower secondary coil 40 and the lower core 60. Therefore, heat conduction from the lower secondary coil 40 to the lower core 60 can be effectively performed. As a result, heat radiation of the coil in the transformer 10 can be further improved.

[0054] In addition, according to one aspect of the present disclosure, the primary coil 30 is coated with enamel. Therefore, since enamel is generally inexpensive, the cost of the transformer 10 can be effectively reduced. In addition, even if enamel having pinholes is coated, since the insulation between the coils is satisfactory, the insulation between the coils can be maintained in the present embodiment.

[0055] Furthermore, according to one aspect of the present disclosure, since the first heat radiation member 70 is configured to be compressed by each of the primary coil 30 and the secondary coils 40 , 45 , heat conduction between the primary coil 30 and each of the secondary coils 40 , 45 may be effectively promoted.

[0056] Now, refer to Figure 5 to Figure 7 Various modified examples obtained by modifying the above-described embodiment will be described.

[0057] First, as Figure 5As shown, the inner peripheral wall 81 of the through hole 80 formed in the first flange 21 (i.e., the retainer) can be formed in a stepped shape. Accordingly, the outer edge of the first heat radiation member 70 can have a shape that matches the inner peripheral wall 81. According to such a configuration, when suppressing or reducing the surface discharge generated along the surface of the first flange 21 in the through hole 80, the first flange 21 does not necessarily become thicker. That is, it is only necessary to extend the surface distance. In addition, the outer edge of the first heat radiation member 70 has a shape that matches the inner peripheral wall 81 of the through hole 80. Through such a deformation, since the outer edge of the first heat radiation member 70 can be stacked on the thinner part 21a (31a) of the flange 21 while being assembled to the inner peripheral wall 81 of the through hole 80, the increase in the total thickness of the first heat radiation member 70 and the first flange 21 can be reduced or suppressed.

[0058] Second, if Figure 6 As shown in FIG. 1 , the inner peripheral wall 81 of the through hole 80 formed in the first flange 21 may be tapered. Accordingly, the outer edge of the first heat radiation member 70 may be shaped to match the inner peripheral wall 81. By means of the configuration of this modified example, the Figure 5 Advantages obtained by the first heat radiation member 70.

[0059] Third, the first performance member 71 and the second performance member 72 may be separated. According to such a configuration, the labor of integrating the first performance member 71 and the second performance member 72 may be reduced or omitted.

[0060] Fourth, if Figures 4 to 6 As shown, the first heat radiation member 70 may be formed of a single member having insulating properties and higher thermal conductivity than that of the bobbin 20 (ie, the holder).

[0061] Fifth, if Figure 7 As shown, the inner peripheral wall 81 of the through hole 80 of the bobbin 20 may have substantially the same thickness as the outer portion of the inner peripheral wall 81. That is, the inner peripheral wall 81 of the through hole 80 of the first flange 21 does not need to adopt a stepped or tapered shape. That is, the first heat radiation member 170 is prepared by a single member in a rectangular plate-like (rectangular sheet-like) state, the single member having a uniform thickness, and made of a material having insulating properties and a thermal conductivity higher than that of the bobbin 20. In addition, it is desirable to form the first heat radiation member 170 to completely cover the through hole 80 to suppress insulation degradation between the primary coil 30 (i.e., the first coil) and the secondary coil 40 (i.e., the second coil). That is, it is desirable that there is no gap between the through hole 80 and the first heat radiation member 170.

[0062] Sixth, the first heat radiation member 70 ( 170 ) is not limited to a plate or sheet shape, but may be a gel shape.

[0063] Seventh, the shape of the through hole 80 is not limited to a rectangle, and may be a polygon, an ellipse, a circle, etc. In addition, in this case, it is desirable that the first heat radiation member 70 (170) has a shape substantially the same as or similar to the through hole 80 when viewed from above (i.e., corresponding to the shape of the through hole 80).

[0064] Eighth, the number of the through holes 80 , that is, the number of the first heat radiation members 70 ( 170 ) arranged in the through holes 80 may be arbitrarily determined.

[0065] Ninth, the first heat radiation member 70 , 170 and the second heat radiation member 75 may be shaped to protrude outward from an opposing range in which each of the primary coil 30 and the secondary coil 40 , 45 is opposed to each other.

[0066] Tenth, each of the bobbin 20 and the primary coil 30 is not limited to a two-layer structure, and may adopt a single-layer structure.

[0067] Eleventh, the coil wire constituting the primary coil 30 is not limited to a square conductor or a round conductor, but a plate-shaped conductor may be used. Similarly, the coil wire constituting each of the secondary coils 40, 45 is not limited to a plate-shaped conductor, but a square conductor having an insulating coating thereon or a round conductor having an insulating coating thereon may be used.

[0068] Twelfth, the insulating coating of the primary coil 30 is not limited to enamel, and resins such as vinyl, polyethylene, etc. may also be used.

[0069] Thirteenth, the DC-DC converter is not limited to the step-down type, but can also be a step-up type. That is, in the transformer 10, the primary coil 30 can be used as the output side coil (i.e., the second coil), and the paired secondary coils 40 and 45 can be used as the input side coil (i.e., the first coil). In addition, the transformer 10 is not limited to the transformer used in the DC-DC converter, but can also be used in a voltage converter, etc.

[0070] As mentioned above, according to one aspect of the present disclosure, a novel transformer (10) includes: a first coil (30); at least one second coil (40, 45), the at least one second coil (40, 45) being magnetically coupled to the first coil; and an electrically insulating holder (20). The first coil (30) and the at least one second coil (40, 45) face each other with the holder (20) sandwiched therebetween. The holder has at least one through hole (80) at a portion (21, 23) sandwiched between the first coil and the at least one second coil. The transformer (10) further includes at least one heat radiation member, the at least one heat radiation member being disposed in the at least one through hole and in contact with the first coil and the at least one second coil. The electrically insulating heat radiation member has a higher thermal conductivity than the holder (70, 170).

[0071] Therefore, according to one aspect of the above structure, the first coil and the second coil are magnetically coupled in the transformer. The first coil and the second coil are opposite to each other with an electrically insulating holder sandwiched therebetween. In addition, due to the difference in heat radiation in the transformer and the value of the current flowing therein, the temperature of each of the first coil and the second coil is different from each other. In addition, one of the coils may be a primary coil and the other coil may be a secondary coil, and vice versa.

[0072] In addition, a through hole is formed in a portion of the retaining member between the first coil and the second coil. In addition, an insulating heat radiation member having insulating properties and a thermal conductivity higher than that of the retaining member is configured in the through hole and is in contact with the first coil and the second coil. Therefore, since the heat radiation member has insulating properties, the first coil and the second coil can be insulated from each other by the heat radiation member. In addition, heat conduction is performed between the first coil and the second coil through the heat radiation member having a thermal conductivity higher than that of the retaining member. Therefore, heat can be effectively conducted from one of the first coil and the second coil having a higher temperature to the other of the first coil and the second coil having a lower temperature. As a result, the heat radiation of the coils in the transformer can be improved while ensuring the insulation between these coils.

[0073] According to another aspect of the present disclosure, at least one through hole is formed in an opposing range in which the first coil and the at least one second coil face each other. In addition, at least one heat radiation member is disposed in the opposing range.

[0074] Therefore, under such a configuration, since the through hole is formed within the relative range in which the first coil and the second coil are relative to each other, it is not necessary to extend the retainer outside the relative range to fix the through hole. In addition, since the heat radiation member is arranged within the relative range, there is no need to arrange the space for the heat radiation member outside the relative range. As a result, even when the heat radiation member is placed in the transformer, the increase in the size of the transformer can be reduced or suppressed.

[0075] According to another aspect of the present disclosure, at least one heat radiation member has an outer edge that is in full contact with an inner peripheral wall (81) of at least one through hole formed in the retainer in a relative direction, the relative direction being a direction in which the first coil and at least one second coil are relative to each other. Therefore, by such a configuration, the through hole can avoid the lack of a heat radiation member between the first coil and the second coil. Therefore, the insulation performance and thermal conductivity between the first coil and the second coil can be more effectively improved. In addition, since the creepage distance along the surface of the through hole in the retainer can be extended, the creepage discharge that is usually generated along the surface can be reduced or suppressed.

[0076] According to another aspect of the present disclosure, at least one heat radiation member substantially completely covers at least one through hole. Therefore, according to such a configuration, since each through hole includes a heat radiation member between the first coil and the second coil, the insulation performance and thermal conductivity between the first coil and the second coil can be further improved.

[0077] According to another aspect of the present disclosure, the inner peripheral wall of at least one through hole formed in the retainer has a portion 21a (31a) thinner than the portion (82) outside the through hole of the retainer. In addition, the outer edge of at least one heat radiation member is stacked on the thinner portion 21a (31a) of the flange 21 (23) while being assembled to the inner peripheral wall of the at least one through hole. Therefore, according to this configuration, in the portion where the retainer and the heat radiation member are vertically stacked on each other, the increase in the total thickness of the retainer and the heat radiation member can be suppressed or reduced. Therefore, the increase in the size of the transformer can be suppressed while improving the insulation between the first coil and the second coil.

[0078] According to yet another aspect of the present disclosure, an inner peripheral wall of at least one through hole of the holder is stepped or tapered, wherein an outer edge of at least one heat radiation member has a shape matching the inner peripheral wall of the at least one through hole.

[0079] Therefore, in the configuration as described above, the inner peripheral wall of the through hole of the holder has a stepped or tapered portion. Therefore, by extending the creeping distance without making the holder thicker, the creeping discharge that is usually generated along the surface of the holder in the through hole can be suppressed or reduced. In addition, the outer edge of the heat radiation member has a shape that matches the inner peripheral wall of the through hole. Therefore, since the outer edge of the heat radiation member can be stacked on the thinner portion 21a (31a) of the flange while being assembled to the inner peripheral wall of the through hole, the increase in the total thickness of the heat radiation member and the holder can be reduced or suppressed.

[0080] According to yet another aspect of the present disclosure, at least one heat radiation member (70) includes: a first performance member (71) having insulation performance; and a second performance member (72) having a thermal conductivity higher than both the thermal conductivity of the retainer and the first performance member.

[0081] Therefore, by the configuration as described above, the first performance member having an insulating property can electrically insulate the first coil and the second coil from each other. In addition, heat conduction between the first coil and the second coil can be effectively performed by the second performance member having a higher thermal conductivity than both the holder and the first performance member. In addition, by assigning the electrical insulation function and the thermal conduction function performed by the heat radiation member to the first performance member and the second performance member, respectively, the heat radiation member can be easily manufactured by using a common material.

[0082] According to yet another aspect of the present disclosure, the first performance component is inserted into the at least one through-hole, and the second performance component substantially completely covers the first performance component and the at least one through-hole.

[0083] Therefore, by the configuration as described above, since the first performance component is inserted into the through hole, heat conduction between the first coil and the second coil can be effectively performed through the first performance component in the through hole. In addition, since the second performance component completely covers the first performance component and the through hole, the insulation between the first coil and the second coil can be enhanced.

[0084] According to another aspect of the present disclosure, the transformer further comprises at least one core (60, 65), wherein the at least one core (60, 65) surrounds the first coil and the at least one second coil (40). In addition, the at least one heat radiating member comprises at least one second heat radiating member. The at least one second heat radiating member (75) is located between the at least one second coil and the at least one core, and contacts the at least one second coil and the at least one core (60). In addition, the at least one second electrically insulating heat radiating member has a higher thermal conductivity than the thermal conductivity of the retaining member.

[0085] Therefore, according to the configuration as described above, the core is configured to surround the first coil and the second coil. In addition, the second heat radiation member having an insulating property and a thermal conductivity higher than that of the holder is configured to contact the second coil and the core. Therefore, since the second heat radiation member has an insulating property, the second heat radiation member can effectively insulate the second coil and the core from each other. In addition, since the heat conduction between the second coil and the core can be performed via the second heat radiation member having a thermal conductivity higher than that of the holder, heat can be effectively conducted from the second coil to the core. Therefore, the heat radiation from the coil in the transformer can be further improved.

[0086] According to another aspect of the present disclosure, the first coil or at least one of the second coils is coated with enamel. Therefore, through the configuration as described above, since enamel is generally relatively cheap, the cost of the transformer can be reduced.

[0087] Furthermore, even when enamel having pinholes that degrades insulation between coils is used as a coating, the transformer as described above can reduce or suppress deterioration of insulation between coils.

[0088] According to another aspect of the present disclosure, at least one heat radiation member is configured to be compressed by the first coil and at least one second coil. Therefore, through such a configuration, heat conduction between the first coil and the second coil can be effectively promoted.

Claims

1. A transformer, comprising: First coil; at least one second coil, the at least one second coil being magnetically coupled to the first coil; an electrically insulating holder, the first coil and the at least one second coil facing each other with the holder sandwiched therebetween, the holder having at least one through hole at a portion sandwiched between the first coil and the at least one second coil; as well as at least one heat radiation member that is electrically insulated, the at least one heat radiation member being disposed in at least one through hole and in contact with the first coil and the at least one second coil, the heat radiation member having a higher thermal conductivity than that of the holder, the at least one through hole being formed in a relative range where the first coil and the at least one second coil face each other, wherein the at least one heat radiation component is arranged within the relative range, The retaining member has a thinner portion around the at least one through hole, wherein the at least one heat radiation member has an outer edge to completely contact a thinner portion formed around the at least one through hole, The at least one through hole has a portion thinner in a vertical direction than a portion radially outside the at least one through hole in the holder, wherein an outer edge of the at least one heat radiation member is laminated on the vertically thinner portion of the holder in the at least one through hole.

2. The transformer according to claim 1, characterized in that The at least one heat radiation member substantially completely covers the at least one through hole.

3. The transformer according to claim 1, characterized in that The inner peripheral wall of the at least one through hole of the retaining member is stepped or tapered to form a thinner portion, Wherein, an outer edge of the at least one heat radiation member has a shape matching the inner peripheral wall of the at least one through hole.

4. The transformer according to claim 1 or 2, characterized in that: The at least one heat radiation member includes: a first performance member having an insulating property; and a second performance member having a thermal conductivity higher than both of the holder and the first performance member.

5. The transformer according to claim 4, characterized in that The first performance component is inserted into the at least one through-hole, and the second performance component substantially completely covers the first performance component and the at least one through-hole.

6. The transformer according to claim 1 or 2, characterized in that: Also includes: at least one core, the at least one core surrounding the first coil and the at least one second coil; wherein the at least one heat radiation member comprises at least one second heat radiation member that is electrically insulated, wherein the at least one second heat radiation member is located between the at least one second coil and the at least one core, and is in contact with the at least one second coil and the at least one core, Wherein, the at least one second heat radiation member has a thermal conductivity higher than a thermal conductivity of the holder.

7. The transformer according to claim 1 or 2, characterized in that: The first coil or the at least one second coil is coated with enamel.

8. The transformer according to claim 1 or 2, characterized in that: The at least one heat radiation member is configured to be compressed by the first coil and the at least one second coil.

9. A DC-DC converter, comprising: heat sink; The transformer according to claim 6; as well as a converter holder securing the at least one core to the heat sink, Wherein, the first coil is arranged between the paired second coils.

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