JP2011181569A - Inductor, transformer, and switching power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inductor, a transformer, and a switching power supply, which achieve high performance, downsizing, and cost reduction. <P>SOLUTION: The inductor comprises: a core having a plurality of magnetic legs; outer magnetic legs formed on both ends of the core, inner magnetic legs formed between the outer magnetic legs; an insulated case attached to the core so that at least the surfaces of some of the outer and inner magnetic legs are exposed; and a planar coil disposed along the side surfaces of the core on the insulated case and the bottom surfaces of grooves between the outer and inner magnetic legs. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an inductor, a transformer, and a switching power supply.

 In recent years, as one of the technologies for improving the fuel efficiency performance and environmental protection performance of a vehicle, the introduction of a hybrid system in which the vehicle is equipped with two power sources, an engine and a motor, and both are coordinated and controlled according to the driving situation. It is out. In this hybrid system, when driving a motor, it is common to convert a DC voltage output from a high-voltage battery into a three-phase AC voltage by an inverter and supply it to the motor.

 In this hybrid system, a switching power supply is connected to a smoothing capacitor provided on the input side of the inverter, and the high voltage power stored in the smoothing capacitor when the motor is driven is converted into low voltage power by the switching power supply. By storing in the battery, energy efficiency is improved and electric shock accidents are prevented.

 As described above, since the switching power supply mounted on the vehicle is required to have high performance, small size, and low cost in addition to high reliability, various improved techniques have been conventionally proposed. For example, as an improved technique that focuses on the configuration of a transformer used for a switching power supply, Patent Document 1 below easily describes the insulation distance between a primary coil and a secondary coil and between a primary coil and a core. The structure of the transformer which can be ensured is disclosed, and the following Patent Document 2 discloses the structure of a transformer having good heat dissipation characteristics.

JP 2001-267152 A JP 2004-303823 A

 What is common in the configurations of the transformers disclosed in Patent Documents 1 and 2 described above is that a flat secondary coil having a ring portion and a hole portion inside thereof is used, and an inner magnetic leg (main magnetic leg or It is the point which combined the core and the secondary coil on both sides of the insulating member so that (synonymous with an axial core part) may penetrate the hole of a secondary coil. When such a configuration is adopted, the following problems occur.

(1) Since the voltage conversion efficiency is reduced (the output voltage is reduced) due to the leakage magnetic flux generated on the side surface of the core, it is difficult to achieve high performance.
(2) Since an annular secondary coil is used, the size of the entire transformer is increased, and the number of assembling steps is also increased.
(3) Since it is necessary to form the hole portion of the secondary coil by punching, a large amount of waste material is generated in the manufacturing process of the secondary coil, resulting in an increase in cost.

   The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide an inductor, a transformer, and a switching power supply that can solve the above-described problems and can realize high performance, downsizing, and low cost. .

In order to solve the above-mentioned problem, in the present invention, as a first solving means related to an inductor, a core having a plurality of magnetic legs, outer magnetic legs formed at both ends of the core, and between the outer magnetic legs An inner magnetic leg formed on the core, an insulating case attached to the core so that at least a part of the outer magnetic leg and the inner magnetic leg are exposed, a side surface of the core on the insulating case, and the A means is provided that includes a flat coil disposed along the bottom surface of the groove between the outer magnetic leg and the inner magnetic leg.
According to the inductor having such a configuration, since the flat coil is disposed along the side surface of the core and the bottom surface of the groove portion, the leakage magnetic flux generated on the side surface of the core can be reduced. That is, by configuring a transformer using this inductor, it is possible to suppress a decrease in voltage conversion efficiency due to leakage magnetic flux, and it is easy to improve the performance of the transformer.
In addition, according to the inductor having such a configuration, the size of the inductor can be reduced as compared with the case of using the annular secondary coil as in the prior art. That is, by configuring the transformer using this inductor, the size of the entire transformer can be reduced, the number of parts can be reduced, and the number of assembly steps can be reduced.
Furthermore, according to the inductor having such a configuration, a flat coil can be formed by bending one continuous flat wiring member, compared with a case where an annular secondary coil is used. The scraps generated in the manufacturing process of the secondary coil (flat coil) can be reduced, and the cost can be reduced.

Further, in the present invention, as a second solving means relating to the inductor, in the first solving means, a plurality of sets of the core, the insulating case, and the flat coil are provided, and the outer magnetic legs and the sets of the sets are provided. A method is adopted in which the exposed surfaces where a part of the inner magnetic legs are exposed are combined to face each other.
According to the inductor having such a configuration, only one type of molding die or molding program is required for each of the core, the insulating case, and the flat coil, and the initial cost can be reduced.

In the present invention, as a third solving means relating to the inductor, in the second solving means, one end of the plurality of flat coils is connected to one side surface on the outer magnetic leg side, and a plurality of the A means is adopted in which the other end of the flat coil is separated from the other side of the outer magnetic leg.
According to the inductor having such a configuration, it is possible to obtain a transformer having a structure that can be easily assembled to a switching power supply.

On the other hand, in the present invention, an inductor that employs the second or third solution is provided as a solution for the transformer, and a core in the inductor is combined to provide a space between the outer magnetic leg and the inner magnetic leg. The primary coil is wound using the space formed in the above, and the flat coil in the inductor is used as the secondary coil.
This makes it possible to obtain a transformer that achieves high performance, downsizing, and low cost.

Furthermore, in the present invention, as a solution relating to the switching power supply, a transformer adopting the above solution, a switching circuit connected to the primary side of the transformer, and a rectifier circuit connected to the secondary side of the transformer The means of preparing is adopted.
This makes it possible to obtain a switching power supply that achieves high performance, miniaturization, and cost reduction.

  According to the present invention, it is possible to provide an inductor, a transformer, and a switching power supply that achieve high performance, downsizing, and low cost.

It is the disassembled perspective view of the inductor 1 in this embodiment, and the perspective view after an assembly. It is the perspective view of the synthetic | combination inductor obtained by combining the two inductors 1, and its equivalent circuit schematic. FIG. 3 is a perspective view showing a state in which two synthetic inductors shown in FIG. 2 are arranged adjacent to each other and an equivalent circuit diagram thereof. FIG. 3 is an exploded perspective view, a perspective view after assembly, and an equivalent circuit diagram of a transformer 100 in the present embodiment. It is a circuit block diagram of the switching power supply 400 in this embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[Inductor]
First, an embodiment of an inductor according to the present invention will be described. FIG. 1A is an exploded perspective view of the inductor 1 in the present embodiment, and FIG. 1B is a perspective view of the inductor 1 after assembly. As shown in these drawings, the inductor 1 in the present embodiment includes a core 10, an insulating case 20, and a flat coil 30.

  The core 10 is, for example, an E-shaped ferrite core having a rectangular shape in a plan view, outer magnetic legs 11 and 12 formed so as to protrude from both ends in the long side direction, and the outer magnetic legs 11 and 12. And an inner magnetic leg 13 formed so as to protrude in parallel at an intermediate position therebetween. The top surfaces 11a and 12a of the outer magnetic legs 11 and 12 and the top surface 13a of the inner magnetic leg 13 are rectangular in plan and are dimensioned to have the same height.

  Further, in the core 10, a groove portion 14 having a bottom surface 14 a is formed between the outer magnetic leg 11 and the inner magnetic leg 13, and a groove portion 15 having a bottom surface 15 a is formed between the outer magnetic leg 12 and the inner magnetic leg 13. Is formed. In the core 10, one E-shaped side surface is 10a, the other E-shaped side surface is 10b, one rectangular side surface is 10c, the other rectangular side surface is 10d, and each magnetic leg top surface 11a. , 12a and 13a, the opposite surface (back surface) is 10e.

  The insulating case 20 is an insulating member that is formed so that the top surfaces 11a, 12a, and 13a of the magnetic legs 10 of the core 10 and the back surface 10e are exposed and the other surfaces are covered. That is, the insulating case 20 is provided with openings 21, 22, and 23 for exposing the top surfaces 11a, 12a, and 13a of the magnetic legs of the core 10 and an opening 24 for exposing the back surface 10e. ing. By mounting such an insulating case 20 on the core 10, the magnetic leg top surfaces 11a, 12a, 13a and the back surface 10e of the core 10 are exposed to the outside, while the groove bottom surfaces 14a, 15a and the side surfaces 10a, 10b. The other surfaces including 10c and 10d are covered with the insulating case 20 (see FIG. 1B).

  The flat coil 30 is a flat wiring member (bus bar) formed by bending along the side surfaces 10a, 10b, and 10d of the core 10 and the groove bottom surfaces 14a and 15a. In other words, the flat coil 30 extends along the conductive path 31 formed along the side surface 10a of the core 10, the conductive paths 32 and 33 formed along the groove bottom surfaces 14a and 15a, and the side surface 10b. The conductive paths 34 and 35 formed in the above and the conductive path 36 formed along the side surface 10d.

  Specifically, the conductive path 31 extends in parallel with the long side direction of the core 10 so as to follow the section from the groove portions 14 to 15 on the side surface 10 a of the core 10. The conductive path 32 is bent from the end on the groove 14 side of the conductive path 31 and extends in parallel with the short side direction of the core 10 so as to follow the entire section of the groove bottom surface 14a. The conductive path 33 is bent from the end on the groove 15 side of the conductive path 31 and extends in parallel with the short side direction of the core 10 along the entire section of the groove bottom surface 15a.

 The conductive path 34 is bent from the end on the side surface 10b side of the conductive path 32 and extends in parallel with the long side direction of the core 10 so as to extend along the section from the groove 14 to the side surface 10d on the side surface 10b of the core 10. ing. The conductive path 35 is bent from the end on the side surface 10b side of the conductive path 33 and extends in parallel with the long side direction of the core 10 so as to extend along the section from the groove 15 to the side surface 10c on the side surface 10b of the core 10. ing. The conductive path 36 is bent from the end portion on the side surface 10d side of the conductive path 34 and extends in parallel with the short side direction of the core 10 so as to follow a section from the side surface 10b to the center position on the side surface 10d of the core 10. ing.

 The flat coil 30 includes a terminal portion 37 formed by bending from an end portion of the conductive path 35 (an end portion on the opposite side to the conductive path 33) in the short side direction of the core 10, and a conductive path 36. Terminal portion 38 formed by bending in the long side direction of the core 10 from the end portion (the end portion on the opposite side to the conductive path 34). The terminal portions 37 and 38 are provided with through holes 37a and 38a that can be fixed with screws. By disposing such a flat coil 30 on the core 10 to which the insulating case 20 is mounted from above the insulating case 20, the inductor 1 shown in FIG. 1B is obtained.

 In FIG. 2A, two inductors 1 having the above-described configuration are used, and two cores 10 are connected to the top surfaces 11a and 12a of the respective magnetic legs in a state where an insulating case 20 and a flat coil 30 are added. And 13a are perspective views showing a combined state so as to face each other and come into contact with each other. In FIG. 2A, in order to distinguish between the two inductors 1, “A” is added to the reference numerals of one inductor 1 and its constituent elements, and “B” is added to the reference numerals of the other inductor 1 and its constituent elements. "Is added. In the following description, when it is not always necessary to distinguish between the two, “A” or “B” may not be added to the reference numerals.

 As shown in FIG. 2A, by combining two inductors 1A and 1B having the same configuration, the terminal portions 38A and 38B of the two flat coils 30A and 30B are arranged at the center of the side surface 10d on the outer magnetic leg 11 side. The terminal portions 37A and 37B of the two flat coils 30A and 30B are separated from each other at the side surface 10c on the outer magnetic leg 12 side. In other words, when the two inductors 1A and 1B are combined, the flat coil 30 is formed so as to be in the state shown in FIG.

 Further, as shown in FIG. 2 (a), by combining the cores 10A and 10B of the two inductors 1A and 1B, a space S1 by the groove portion 14 between the outer magnetic legs 11 and the inner magnetic legs 13 is formed. As a result, a space S <b> 2 is formed by the groove 15 between the outer magnetic leg 12 and the inner magnetic leg 13. By winding the primary coil using these spaces S1 and S2, it becomes possible to obtain a transformer that uses flat coils 30A and 30B as described later as secondary coils.

  FIG. 2B is an equivalent circuit diagram of the inductors 1A and 1B (hereinafter referred to as combined inductors) combined as shown in FIG. As shown in FIG. 2B, the equivalent circuit of the synthetic inductor is wound around the core 10A and wound around the core 10B and the flat coil 30A having one end as a terminal portion 37A and the other end as a terminal portion 38A. Thus, a flat coil 30B having one end as a terminal portion 37B and the other end as a terminal portion 38B is connected in series. That is, the terminal portions 38A and 38B, which are connecting portions of the flat coils 30A and 30B, can be used as center taps when the flat coils 30A and 30B are used as secondary coils of the transformer.

 FIG. 3A is a perspective view showing a state in which another set of the composite inductor shown in FIG. 2A is prepared and arranged adjacent to each other. In FIG. 3A, “C” is added to the reference numerals of one inductor 1 and its constituent elements that constitute another set of added synthetic inductors, and the reference numerals of the other inductor 1 and its constituent elements are “ "D" is appended.

 That is, as an equivalent circuit, as shown in FIG. 3B, a flat coil 30C wound around the core 10C and having one end as a terminal portion 37C and the other end as a terminal portion 38C is wound around the core 10D. Thus, a portion in which a flat coil 30D having one end as a terminal portion 37D and the other end as a terminal portion 38D is connected in series is added. In this case, the terminal portions 38C and 38D, which are connecting portions of the flat coils 30C and 30D, can be used as center taps when the flat coils 30C and 30D are used as secondary coils of the transformer.

 In the configuration in which the two composite inductors are arranged adjacent to each other in this manner, the primary coil is wound using the spaces S1 and S2 formed in the two composite inductors, and the flat coils 30A, 30B, and 30C are wound. , 30D can be used as a secondary coil of the transformer, a divided transformer in which the secondary side is divided into two systems as described later can be obtained.

〔Trance〕
Subsequently, an embodiment of a transformer according to the present invention will be described. 4A is an exploded perspective view of the transformer 100 in the present embodiment, FIG. 4B is a perspective view of the transformer 100 after assembly, and FIG. 4C is an equivalent circuit of the transformer 100. FIG. In the transformer 100 in the present embodiment, a primary coil is wound using spaces S1 and S2 formed in each of the two sets of synthetic inductors shown in FIG. , 30C, 30D are split transformers using secondary coils.

 That is, as shown in FIG. 4A, the transformer 100 according to the present embodiment includes an inductor 1A including a core 10A, an insulating case 20A, and a flat plate coil (hereinafter referred to as a secondary coil) 30A, a core 10B, and an insulation. An inductor 1B composed of a case 20B and a secondary coil 30B, an inductor 1C composed of a core 10C, an insulating case 20C and a secondary coil 30C, and an inductor 1D composed of a core 10D, an insulating case 20D and a secondary coil 30D are wound in an annular shape. The primary coil 40 is formed in a round shape.

 The primary coil 40 has an annular portion 41 and a hole 42 formed inside the annular portion 41, and further, a primary side circuit (switching circuit) is connected to both ends of the primary coil 40. Primary-side connection terminals P11 and P12 are connected.

 The inner magnetic leg 13A of the core 10A of the inductor 1A is fitted into the hole 42 of the primary coil 40 (at the same time, the annular portion 41 of the primary coil 40 is fitted into the grooves 14A and 15A of the core 10A). The inner magnetic leg 13B of the core 10B in the inductor 1B is fitted from the side facing the inductor 1A (at the same time, the annular portion 41 of the primary coil 40 is fitted into the grooves 14B and 15B of the core 10B). 4B is obtained by combining 1B with the primary coil 40 interposed therebetween and similarly combining the inductors 1C and 1D with the primary coil 40 interposed therebetween.

 As shown in FIG. 4B, the secondary coil 30A, 30B, 30C, and 30D have terminal portions 37A, 37B, 37C, and 37D that are connected to the secondary circuit (rectifier circuit). Side connection terminals P21, P22, P23, and P24 are connected. In the following, for convenience of explanation, the terminal portions 38A and 38B that are the connection portions of the secondary coils 30A and 30B are referred to as center taps CT1, and the terminal portions 38C and 38D that are the connection portions of the secondary coils 30C and 30D are the center portions. This is referred to as a tap CT2 (see FIGS. 4B and 4C).

 As shown in FIG. 4C, the equivalent circuit of the transformer 100 is obtained by adding a primary coil 40 having primary side connection terminals P11 and P12 connected to both ends to the equivalent circuit shown in FIG. The secondary side is divided into two systems. That is, when a primary AC voltage is applied to the primary coil 40 via the primary side connection terminals P11 and P12, 2 according to the respective turns ratio of the primary coil 40 and the secondary coils 30A, 30B, 30C, and 30D. The secondary AC voltage is between the secondary connection terminal P21 and the center tap CT1, between the secondary connection terminal P22 and the center tap CT1, between the secondary connection terminal P23 and the center tap CT2, and the secondary. This occurs between the side connection terminal P24 and the center tap CT2.

 According to the transformer 100 in the present embodiment adopting the above-described configuration, it is possible to solve the above-described problems of the related art. That is, in the transformer 100 according to the present embodiment, the secondary coil (flat plate coil) 30 is arranged along the side surfaces 10a and 10b and the groove bottom surfaces 14a and 15a of the core 10 to reduce leakage magnetic flux generated on the core side surface. As a result, a decrease in voltage conversion efficiency is suppressed, and high performance is facilitated.

 Further, in the transformer 100 according to the present embodiment, the plate-shaped secondary coil 30 is arranged along the side surfaces 10a and 10b and the groove bottom surfaces 14a and 15a of the core 10, so that the ring-shaped secondary coil as in the prior art is used. Compared to the case where a coil is used, the size of the entire transformer can be reduced and the number of parts can be reduced, so that the number of assembly steps can be reduced. Furthermore, in the transformer 100 according to the present embodiment, the secondary coil 30 is formed by bending one continuous flat wiring member, so that the secondary coil 30 is compared with a case where an annular secondary coil is used. The scraps generated in the manufacturing process can be reduced, and the cost can be reduced.

 As described above, by configuring the transformer 100 using the inductor 1 in the present embodiment, it is possible to obtain the transformer 100 that achieves high performance, downsizing, and low cost.

[Switching power supply]
Subsequently, an embodiment of a switching power supply according to the present invention will be described. FIG. 5 is a circuit configuration diagram of the switching power supply 400 in the present embodiment. As shown in FIG. 5, the switching power supply 400 in this embodiment is connected to the transformer 100 shown in FIG. 4, the switching circuit 200 connected to the primary side of the transformer 100, and the secondary side of the transformer 100. And the rectifier circuit 300.

 4C, the transformer 100 includes a primary coil 40 having primary side connection terminals P11 and P12 connected to both ends, one end connected to the secondary side connection terminal P21, and the other end center tap. Secondary coil 30A connected to CT1, one end connected to secondary connection terminal P22, the other end connected to secondary coil 30B connected to center tap CT1, and one end connected to secondary connection terminal P23 The secondary coil 30C has the other end connected to the center tap CT2, and the secondary coil 30D has one end connected to the secondary side connection terminal P24 and the other end connected to the center tap CT2.

 The switching circuit 200 is a circuit that converts a DC voltage input from the outside into a primary AC voltage by a switching operation and outputs it to the primary side of the transformer 100. The switching circuit 200 includes a positive input terminal 201 for inputting a DC voltage, and It comprises a negative input terminal 202, four transistors 203, 204, 205, 206, four snubber diodes 207, 208, 209, 210, and a resonance coil 211.

 Each transistor 203, 204, 205, 206 is, for example, an n-type field effect transistor (FET). The drain terminals of the transistors 203 and 205 are connected to the positive input terminal 201, and the source terminals of the transistors 204 and 206 are connected to the negative input terminal 202. The source terminal of the transistor 203 and the drain terminal of the transistor 204 are connected, and the source terminal of the transistor 205 and the drain terminal of the transistor 206 are connected. Note that the drain terminal of the transistor 206 (the source terminal of the transistor 205) is connected to the primary side connection terminal P12 of the transformer 100.

 Although not shown in FIG. 5, the gate terminals of the transistors 203, 204, 205, and 206 are connected to a PWM (Pulse Width Modulation) control circuit. That is, the on / off operation (switching operation) of each of the transistors 203, 204, 205, and 206 is controlled by the PWM signal that is input from the PWM control circuit to each gate terminal.

 The snubber diode 207 is connected in parallel between the drain and source terminals of the transistor 203. The snubber diode 208 is connected in parallel between the drain and source terminals of the transistor 204. The snubber diode 209 is connected in parallel between the drain and source terminals of the transistor 205. The snubber diode 210 is connected in parallel between the drain and source terminals of the transistor 206. One end of the resonance coil 211 is connected to the source terminal of the transistor 203 (the drain terminal of the transistor 204), and the other end is connected to the primary side connection terminal P11 of the transformer 100.

 On the other hand, the rectifier circuit 300 is a circuit that converts the secondary AC voltage output from the transformer 100 into a DC voltage by rectification and outputs the DC voltage to the outside, and includes four rectifier diodes 301, 302, 303, 304, and 2 It comprises two smoothing coils 305 and 306, three smoothing capacitors 307, 308 and 309, and an output terminal 310.

 The anode terminal of the rectifier diode 301 is connected to the secondary side connection terminal P <b> 21 of the transformer 100, and the cathode terminal is connected to one end of the smoothing coil 305. The anode terminal of the rectifier diode 302 is connected to the secondary connection terminal P22 of the transformer 100, and the cathode terminal is connected to one end of the smoothing coil 305. The anode terminal of the rectifier diode 303 is connected to the secondary side connection terminal P <b> 23 of the transformer 100, and the cathode terminal is connected to one end of the smoothing coil 306. The anode terminal of the rectifier diode 304 is connected to the secondary side connection terminal P24 of the transformer 100, and the cathode terminal is connected to one end of the smoothing coil 306.

 The other end of the smoothing coil 305 is connected to one end of the smoothing capacitors 307 and 309 and the output terminal 310. The other end of the smoothing coil 306 is connected to one end of the smoothing capacitors 308 and 309 and the output terminal 310. The other ends of the smoothing capacitors 307, 308 and 309 are connected to a common ground line. Among them, the other end of the smoothing capacitor 307 is also connected to the center tap CT1 of the transformer 100, and the other end of the smoothing capacitor 308 is the transformer. It is also connected to 100 center taps CT2. That is, the center taps CT1 and CT2 of the transformer 100 are connected to a common ground line in the rectifier circuit 300.

 As described above, by adopting the configuration in which the transformer 100 according to the present embodiment is used as the main transformer of the switching power supply 400, it is possible to obtain the switching power supply 400 that realizes high performance, downsizing, and low cost. .

[Modification]
In addition, this invention is not limited to the said embodiment, The following modifications are mentioned.
(1) In the above embodiment, the flat coil (secondary coil) 30 having the shape as shown in FIG. 1 is exemplified, but the shape of the flat coil 30 is appropriately set within the scope of the present invention. It may be changed. That is, the flat coil 30 only needs to have a shape that extends along at least the side surfaces 10a and 10b of the core 10 and the groove bottom surfaces 14a and 15a, and the presence or absence and position of the terminal portions 37 and 38 are not particularly limited.

(2) In the above embodiment, as illustrated in FIG. 4, a distributed transformer using two sets of synthetic inductors (a combination of two inductors 1) as the transformer 100 has been described as an example. The transformer according to the present invention is not limited to this, and a transformer using one set or three or more sets of synthetic inductors may be configured.

(3) In the above embodiment, the switching power supply 400 including the switching circuit 200 and the rectifier circuit 300 having the circuit configuration shown in FIG. 5 has been described as an example. However, these circuit configurations are merely examples, and the switching power supply The circuit configurations of the switching circuit 200 and the rectifier circuit 300 may be appropriately changed according to the performance and specifications required for the 400 or the configuration of the transformer 100.

  DESCRIPTION OF SYMBOLS 1 ... Inductor, 10 ... Core, 20 ... Insulating case, 30 ... Flat plate coil (secondary coil), 40 ... Primary coil, 100 ... Transformer, 200 ... Switching circuit, 300 ... Rectifier circuit, 400 ... Switching power supply

Claims (5)

A core having a plurality of magnetic legs;
Outer magnetic legs formed at both ends of the core;
An inner magnetic leg formed between the outer magnetic legs;
An insulating case attached to the core so that at least a part of the outer magnetic legs and the inner magnetic legs are exposed;
A flat coil disposed along the side surface of the core on the insulating case and the groove bottom surface between the outer magnetic leg and the inner magnetic leg;
An inductor comprising: A plurality of sets of the core, the insulating case and the flat coil,
2. The inductor according to claim 1, wherein exposed surfaces from which a part of the surfaces of the outer magnetic legs and the inner magnetic legs of each set are exposed face each other.   One end of the plurality of flat coils is connected on one side surface on the outer magnetic leg side, and the other end of the plurality of flat plate coils is separated on the other side surface on the outer magnetic leg side. The inductor according to claim 2. An inductor according to claim 2 or 3,
A primary coil is wound using a space formed between the outer magnetic leg and the inner magnetic leg by combining the cores in the inductor, and the flat coil in the inductor is secondary. A transformer characterized by being used as a coil. A transformer according to claim 4;
A switching circuit connected to the primary side of the transformer;
A rectifier circuit connected to the secondary side of the transformer;
A switching power supply comprising:

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