JP2011009418A - Insulating transformer for switching power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized insulating transformer for a switching power supply having excellent conductive heat-dissipating characteristics.SOLUTION: The insulating transformer 11 includes a core 12 winding a primary-side coil 22 and a secondary-side coil 24, a primary-side terminal 18 for the primary-side coil 22, and a secondary-side terminal 20 for the secondary-side coil 24. The insulating transformer 11 further includes an insulating cover 16 including openings between the primary-side terminal 18 and the core 12 and on a surface brought into contact with the base of the core, and a heat sink 14 installed at a position opposed to the opening 26 of the insulating cover 16 on the base of the core. When the insulating transformer fitting the heat sink 14 is mounted on a metallic base board 40, a pad 30 for conductive heat dissipation is installed at the position opposed to the heat sink 14 fitted on the base of the core on the metallic base board 40. Accordingly, heat generation in the core 12 is conducted to the heat sink 14 and diffused efficiently to the metallic base board 40.

Description

The present invention relates to an insulating transformer of a switching power supply apparatus that conducts and dissipates heat of the insulating transformer using a metal base substrate.

  An insulating transformer that is mounted on a metal base substrate and used as a switching power supply device is desired to have a structure that is small in size, does not take a mounting space, and can easily dissipate heat.

  However, the challenge of miniaturization is that the insulation transformer itself must be miniaturized, and at the same time, it is necessary to ensure an insulation distance according to safety standards. The space distance between the terminal and the transformer measured through the space is determined according to the operating voltage Yes. For this reason, conventionally, the insulation distance has been secured by the creepage distance measured along the surface of the insulator using an insulator. In addition, when an insulating cover that covers the transformer is used, even if the insulation distance can be secured, the heat dissipation is reduced.

An insulating transformer used in a conventional switching power supply device has a structure shown in FIG. 9, for example.
In FIG. 9, 52 is a core, 54 is a primary side terminal, 56 is a secondary side terminal, 58 is a bobbin, and 60 is a metal base substrate.

  As shown in the conventional example of FIG. 9, in order to improve heat dissipation, the core 52 is in direct contact with the metal base substrate 60 to dissipate heat, and the insulation distance is the distance X between the core 52 and the primary terminal 54. It was secured by lengthening.

  As a method for improving the heat conduction efficiency in the method in which the core and the metal base substrate are in direct contact with each other, a minute gap is provided between the core and the metal base substrate, and a high thermal conductivity resin such as gel-like silicon is provided. In other words, a method has been proposed in which the heat generated in the core is efficiently transferred to and dissipated from the metal base substrate by filling the epoxy resin or improving the adhesion through sheet-like silicon (for example, Japanese Patent Laid-Open No. 4-209509). No. publication etc.).

  As a method of ensuring the insulation distance, there is one shown in FIG. In FIG. 10, 72 is a core, 74 is a resin case, 76 is a primary side terminal, 78 is a secondary side terminal, and 80 is a metal base substrate, and the core 72 itself is covered with a resin case 74 filled with an insulating resin. There is a way. There is also an example in which an insulation distance is secured by using a bobbin of a transformer (see, for example, Japanese Patent Application Laid-Open No. 2006-228996).

JP-A-4-209509 JP 2006-228996 A

  However, in the conventional method, even if the core is brought into direct contact with the metal base substrate in an attempt to efficiently conduct and dissipate the heat generated in the core, the insulation distance from the primary side terminal becomes long and the mounting space is reduced. There was a problem that had to be taken widely.

  In addition, in the method of covering the core with insulating resin in order to reduce the mounting space, the heat generated in the core is conducted and dissipated through the insulating resin, resulting in a decrease in heat conduction efficiency and generation of a large amount of heat. There was a problem that could not be used with the product.

SUMMARY OF THE INVENTION An object of the present invention is to provide an insulating transformer for a switching power supply having good conduction and heat dissipation characteristics without taking a long insulation distance in a switching power supply in which an insulating transformer is mounted on a metal base substrate.

  The present invention provides an insulating transformer which is mounted on a metal base substrate and used for a switching power supply device, and which solves the problems of insulating distance and heat dissipation.

  The insulating transformer of the present invention includes a core around which a primary winding and a secondary winding are wound, a primary side terminal of the primary winding, a secondary side terminal of the secondary winding, a primary side terminal, and a core. An insulating cover having openings in the space and a surface in contact with the bottom surface of the core portion, and a heat radiating plate provided at a position facing the insulating cover opening in the core bottom surface portion.

  An insulating transformer for a switching power supply device has a function of converting a DC voltage obtained by rectifying and smoothing an input voltage into an output voltage, and a function of insulating a primary side which is an input side of a switching power supply and a secondary side which is an output side Have together. For this reason, the insulation distance should just consider between a core and a primary side terminal, the insulation cover is provided in this space, and the creeping distance is added.

  In addition, an opening is provided in the portion of the insulating cover that contacts the bottom surface of the core so that the heat sink provided on the bottom surface of the core is in contact with the metal base substrate, and the heat generated in the core is conducted and dissipated to the metal base substrate. It is said.

  It is also possible to employ a structure in which an insulating case is provided between the core and the secondary terminal with the core as the primary potential.

  In the insulating transformer, the heat radiating plate is made of metal. By using a metal, the heat conduction efficiency can be increased.

  Furthermore, in the insulating transformer, the metal heat dissipation plate is made of copper. In order to efficiently conduct and dissipate heat in contact with the metal base substrate, the adhesion can be improved by using copper which can be soldered at low cost.

  In the insulating transformer, the heat radiating plate is subjected to a plating process capable of being soldered to the surface.

  In the insulating transformer, the heat radiating plate may be an insulating transformer characterized in that a part of the core is formed in a protruding shape and is integrally formed with the core. As a heat radiating plate from the opening on the bottom surface of the core, a protrusion having a heat radiating plate shape is integrally formed on the core itself.

  An insulating transformer provided with a heat radiating plate is characterized in that a conductive heat radiating pad is provided on the metal base substrate at a position opposite to the heat radiating plate attached to the bottom surface of the core when mounted on the metal base substrate. Thereby, the heat generated in the core is efficiently diffused to the metal base substrate through the heat sink.

When the heat sink is mounted on the metal base substrate, the heat sink is soldered to a pad on the metal base substrate and mounted on the metal base substrate. The pad is a land for soldering provided on the insulating layer of the metal base substrate. When soldering the primary and secondary terminals of the insulating transformer to the pattern on the metal base substrate, Mounting with good adhesion can be achieved by soldering the pad at the same time.

  According to the present invention, the insulation case is provided between the core and the primary side terminal to ensure the creepage distance, so there is no need to increase the distance between the core and the primary side terminal, and the effect of reducing the mounting space can be achieved. is there.

  Since the heat generated in the core can be conducted and radiated between the core and the metal base substrate through a heat radiating plate, an effect of enabling high-efficiency heat dissipation is obtained even if an insulating case is used.

  By making the heatsink a metal, preferably copper, high heat conduction efficiency is obtained, and the heatsink can be soldered together with the terminals by performing a plating process that enables soldering. Thereby, in addition to improving the adhesion between the heat sink and the metal base substrate, it is possible to manufacture at the same time as the soldering process of the pattern of the primary side terminal and the secondary side terminal, and an improvement in productivity can be expected.

  If the heat sink is formed integrally with the core by providing a protrusion corresponding to the heat sink shape on the bottom surface of the core, the number of parts can be reduced and the cost can be reduced.

  Since the metal base substrate is provided with a pad in contact with the heat radiating plate, conductive heat radiation can be efficiently performed with improved adhesion by soldering.

According to the present invention, in a switching power supply device using an insulating transformer mounted on a metal base substrate, the distance between the core and the primary side terminal can be shortened, so that the size can be reduced and a high conductive heat radiation effect can be obtained.

The perspective view which showed embodiment of the insulation transformer by this invention mounted in the metal base board | substrate Front view of the embodiment of FIG. Explanatory drawing which showed the mounting state which mounted the insulation transformer of FIG. 1 on the heat sink Exploded view of core, heat sink and insulating cover of insulating transformer according to the present invention The perspective view of the insulation transformer by this invention Bottom view of an isolation transformer according to the present invention The perspective view which showed the metal base board which mounts the insulation transformer by this invention Explanatory drawing showing the core molded integrally with the heat sink Explanatory drawing of a conventional example for securing the insulation distance of the insulation transformer Explanatory drawing of a conventional example with an insulating transformer covered with an insulating cover

  An embodiment of an insulating transformer of a switching power supply device according to the present invention will be described below with reference to FIGS.

  FIG. 1 is a perspective view of an embodiment in which the insulating transformer 11 of the present invention is mounted on a metal base substrate 40. The insulating transformer 11 includes a core 12, a primary side terminal 18, a secondary side terminal 20, an insulating cover 16, a primary side coil 22 and a secondary side coil 24. The metal base substrate 40 includes a pattern 32, an insulating layer 42, and a metal plate 44.

  The primary coil 22 is wound as a primary winding from the primary terminal 18 to the core 12. Similarly, the secondary coil 24 is wound around the core 12 from the secondary terminal 20 as a secondary winding. The primary side coil 22 is shown only on the input side, and the secondary side coil 22 is shown only on the lead-out portion from the core 12 on the output side.

  An insulating cover 16 is provided to ensure an insulating distance. The insulating cover 16 is substantially L-shaped and configured to be a high wall with the bottom surface of the core 12 and the core 12 and the primary terminal 18 interposed therebetween. Since the insulation distance between the core 12 and the primary terminal 18 is arranged via the insulation cover 16 that is an insulator, the creepage distance along the creepage of the insulation cover 16 is added in addition to the spatial distance. The insulation distance can be ensured without increasing the distance between the core 12 and the primary terminal 18.

  The primary side terminal 18 and the secondary side terminal 20 are mounted by being soldered to the pattern 32 wired on the insulating layer 42 laminated on the metal plate 44 of the metal base substrate 40. Conductive heat dissipation of the heat generated in the core 12 with the insulating transformer 11 mounted on the metal base substrate 40 to the metal plate 44 will be described with reference to FIG.

  FIG. 2 is a front view of the switching power supply device of the present invention. An opening 26 is provided at a portion in contact with the insulating cover 16 and the bottom surface of the core 12, and the heat dissipation plate 14 in contact with the core 12 is in contact with the metal base substrate 40 through the opening 26. The insulating layer 42 on the metal base substrate 40 is provided with a pad 30 in contact with the heat sink 14. Therefore, the heat generated in the core 12 is conducted and radiated to the metal plate 44 via the heat radiating plate 14, the pad 30 and the insulating layer 42, and is diffused by the metal plate 44. The pad 30 is a land pattern of copper wire used as wiring, and is soldered to the heat sink 14. Soldering is simultaneously performed by reflow together with the primary side terminal 18 and the secondary side terminal 20 when the insulating transformer 11 is mounted on the metal base substrate 40. By soldering in this way, not only productivity is improved, but also the adhesion between the heat radiating plate 14 and the metal base substrate 40 is improved to realize efficient heat radiation.

  FIG. 3 is a front view when the insulating transformer 11 of the present invention is mounted on the heat sink 46. The heat generated in the core 12 is conducted and radiated to the metal plate 44 of the metal base substrate 40 through the heat radiating plate 14, the pad 30 and the insulating layer 42. In order to further increase the heat radiating effect, the insulating transformer 11 is It is mounted on a heat sink 46 for heat dissipation. A flow 48 of heat conduction / radiation generated in the core 12 is indicated by an arrow. The heat conducted from the heat radiating plate 14 and the pad 30 is diffused widely in the lateral direction by the metal plate 44 and conducted to the entire surface of the heat sink 46 to enhance the heat releasing effect.

  FIG. 4 is an exploded view of the insulating transformer 11 according to the present invention excluding the coil relation. Since the coil is wound around the middle leg of the core, the coil does not exist on the upper surface portion and the bottom surface portion of the core 12 and is flat. A flat heat sink 14 is provided in contact with the flat surface of the bottom surface.

  The thickness of the heat radiating plate 14 is equivalent to the thickness of the insulating cover 16 with which the bottom surface of the core 12 contacts. The size is the same as or smaller than the bottom surface of the core 12. The heat radiating plate 14 is provided to conduct and dissipate the heat of the core, and the material is a metal having high thermal conductivity, preferably copper. Since copper can be soldered at low cost, the pad 30 formed on the metal base substrate 40 shown in FIG. 2 can be manufactured with good adhesion by soldering. Further, when another material that cannot be soldered is used for the heat radiating plate 14, the surface of the heat radiating plate 14 can be plated to be solderable. In this case, the surface treatment on the heat sink 14 includes nickel plating, tin plating, nickel palladium plating, and the like.

  The insulating cover 16 has an opening 26 in the bottom plate portion, and allows the heat radiating plate 14 provided in the core 12 to pass therethrough. However, it is necessary to ensure an insulation distance defined by safety standards between the opening 26 and the primary pattern 32. The insulating cover 16 has a structure in which a plate-like insulating wall 16a is provided on the side surface of the core 12 and an insulator is disposed between the core 12 and the primary terminal 18 shown in FIG. The insulation wall 16a has a creeping distance along the insulation wall 16a added to the case where the insulation distance between the core 12 and the primary terminal 18 shown in FIG. The primary side terminal 18 can be disposed at a short distance. The insulating cover 16 also plays a role of supporting the primary side terminal 18 and the secondary side terminal 20 shown in FIG.

  FIG. 5 is a perspective view of the insulating transformer 11, and FIG. 6 is a bottom surface portion of the insulating transformer 11. 5 and 6, the insulating cover 16 in which the primary side terminal 18 and the secondary side terminal 20 are attached to the core 12 and the heat sink 14 around which the primary side coil 22 and the secondary side coil 24 are wound is assembled. The insulating transformer 11 having good heat dissipation can be obtained. The heat sink 14 that has passed through the opening 26 on the bottom surface of the insulating cover 16 contacts the pad of the metal base substrate 40 shown in FIG.

  FIG. 7 is a perspective view of the metal base substrate 40. An insulating layer 42 is laminated on a conductive heat radiating metal plate 44. Further, the insulating layer 42 is soldered to the primary side terminal 18 and the secondary side terminal 20 shown in FIG. Patterns 32 and 34 by copper wiring are provided. And the pad 30 which receives the heat sink 14 shown in FIG. 6 is provided. The pad 30 is a copper wiring pattern similar to the patterns 32 and 34, and is a land having a size corresponding to the heat sink 14 shown in FIG. The insulating layer 42 is thin and has little influence on the heat conduction characteristics. The metal plate 44 uses lightweight aluminum or the like.

  FIG. 8 is a diagram showing the shape of the core 12 when the heat radiating plate 14 is formed integrally with the core 12, and FIG. 8A shows the bottom surface and FIG. 8B shows the side surface. The core 12 is manufactured by molding ferrite or the like in a mold. However, the core 12 may be integrally manufactured by forming a mold for molding into a mold having a shape corresponding to the heat sink 14. As a result, there is no need to prepare the heat sink 14 as a separate component, which is advantageous in terms of cost, and since there is no connection between the core 12 and the heat sink 14, the heat conduction characteristics are good and the heat dissipation is excellent. Structure.

  In the above embodiment, the example in which the core is regarded as the secondary side potential and the insulating cover is provided between the core and the primary side terminal has been described. However, the core is regarded as the primary side potential and the secondary side terminal. An insulating cover may be provided between the two.

Although the present invention has been described above, the present invention includes appropriate modifications that do not impair the object and advantages thereof, and is not limited to the above-described embodiments.

11: insulation transformer 12: core 14: heat sink 16: insulation cover 16a: insulation wall 18: primary side terminal 20: secondary side terminal 22: primary side coil 24: secondary side coil 26: opening 30: pad 32, 34: Pattern 40: Metal base substrate 42: Insulating layer 44: Metal plate 46: Heat sink 48: Flow of conduction heat dissipation

Claims (8)

A core around which a primary winding and a secondary winding are wound;
The primary terminal of the primary winding;
A secondary terminal of the secondary winding;
An insulating cover having an opening on the surface between the primary terminal and the core and on the surface in contact with the core bottom surface;
A heat dissipating plate provided at a position facing the insulating cover opening of the core bottom surface,
Insulation transformer with.
A core around which a primary winding and a secondary winding are wound;
The primary terminal of the primary winding;
A secondary terminal of the secondary winding;
An insulating cover having an opening on a surface between the secondary terminal and the core and in contact with the core bottom surface;
A heat dissipating plate provided at a position facing the insulating cover opening of the core bottom surface,
Insulation transformer with.
The insulation transformer according to claim 1 or 2,
The heat sink is a metal;
Insulation transformer characterized by.
The insulation transformer according to claim 3,
The heat sink is copper;
Insulation transformer characterized by.
The insulation transformer according to claim 1 or 2,
The heat sink is plated on the surface so that it can be soldered,
Insulation transformer characterized by.
The insulation transformer according to claim 1 or 2,
The heat sink is molded integrally with the core with a part of the core as a protruding shape,
Insulation transformer characterized by.
7. The insulating transformer according to claim 1, further comprising a metal base substrate disposed outside the insulating cover, wherein the metal base substrate is opposed to a heat sink attached to the bottom surface of the core. An insulating transformer characterized in that a conductive heat dissipating pad is provided.
  8. The insulating transformer according to claim 7, wherein when mounted on the metal base substrate, the pad is soldered to a pad on the metal base substrate and mounted on the metal base substrate.

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