JP2016009704A - Power transformer and power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power transformer and a power supply device capable of miniaturizing a transformer substrate itself and of simultaneously reducing cost.SOLUTION: A power transformer 42 comprises a planar transformer on which winding of a coil is arranged on a plurality of layers of a substrate. The power transformer 42 has: a primary substrate 40a on which a primary coil 80a of the planar transformer is provided; and a secondary substrate 40b configured separately from the primary substrate 40a, and on which a secondary coil 80b of the planar transformer is provided opposedly to the primary coil 80a. On the plurality of layers of the secondary substrate 40b, a secondary circuit connected with the secondary coil 80b is provided.

Description

  Embodiments described herein relate generally to a power transformer and a power supply apparatus.

  For example, AC / DC converters, DC / AC inverters, and the like are known as power supply devices that generate power suitable for electronic devices such as computers and televisions. The power supply device is provided with a power transformer for converting, for example, commercial AC input voltage 100V to 240V into a low DC output voltage. The power transformer includes a single transformer substrate formed by laminating a primary coil and a secondary coil wound in a planar shape.

JP 2011-258876 A

  In power transformers, for example, a secondary circuit for a secondary coil is constructed on a transformer substrate, thereby eliminating a creepage distance for achieving electrical insulation, thereby reducing the size. However, when a secondary circuit is constructed on a single transformer substrate, the number of layers of the substrate in the secondary circuit portion matches the total number of layers of the substrate in the coil portion in which the primary coil and the secondary coil are laminated. In other words, the number of layers of the substrate in the secondary circuit portion includes a surplus portion that exceeds the number of layers necessary to construct the secondary circuit portion. In this case, since the manufacturing cost of the surplus portion is added, there is a limit to the cost reduction of the entire transformer substrate.

  An object of the present invention is to provide a power supply transformer and a power supply device that can reduce the cost of the transformer substrate itself while simultaneously reducing the cost.

  According to the embodiment, the power transformer includes a planar transformer in which coil windings are arranged on a plurality of layers of the substrate, and the power transformer includes a primary substrate provided with a primary coil of the planar transformer, A secondary substrate that is configured separately from the primary substrate and is provided with a secondary coil of a planar transformer facing the primary coil, and the secondary coil is provided on a plurality of layers of the secondary substrate. A secondary circuit connected to is provided.

The perspective view which shows the external appearance of the power supply device which concerns on one Embodiment. The disassembled perspective view of the power supply device which concerns on one Embodiment. The disassembled perspective view of the power supply device which concerns on one Embodiment seen from the direction different from FIG. The perspective view which looked at the transformation structure of the power supply device which concerns on one Embodiment from the surface side of the main circuit board. The top view which looked at the transformation structure of the power supply device which concerns on one Embodiment from the back surface side of the main circuit board. The perspective view which looked at the transformation structure of the power supply device which concerns on one Embodiment from the output cable side. The disassembled perspective view of the power supply transformer provided in the power supply device which concerns on one Embodiment.

Hereinafter, an embodiment will be described with reference to the drawings.
FIG. 1 shows a power supply device 10 that supplies power suitable for electronic devices such as computers and televisions. As the power supply device 10, for example, an AC / DC converter, a DC / AC inverter, and the like are known. In the present embodiment, an AC / DC converter will be described as an example of the power supply device 10.

  The AC / DC converter 10 includes, for example, a case 12 that houses a transformer structure that transforms a commercial AC input voltage 100V to 240V into a low DC output voltage, an input connector 14 that can be connected to a commercial AC power source, and an electronic device. And an output cable 16 capable of outputting a DC voltage. The case 12 has an upper case 12a and a lower case 12b made of, for example, a synthetic resin material, and is configured to be separable. The transformer structure is accommodated between these two cases 12a and 12b.

2 and 3 show an example of the transformation structure of the AC / DC converter 10. The transformer structure includes a main circuit board 20 provided with a primary circuit, a power transformer 42 that transforms a commercial AC input voltage and outputs it as a DC voltage, and a cooling mechanism that cools the transformer structure itself. .
Hereinafter, after describing the “cooling mechanism”, the “main circuit board 20” and the “power transformer 42” will be described in this order.

[Cooling mechanism]
As the cooling mechanism, for example, an intermediate cooling sheet metal 60, an upper cooling sheet metal 70, and a lower cooling sheet metal 72 are provided, and these cooling sheet metals 60, 70, 72 are formed of a material having high heat conductivity, for example, copper, aluminum or the like. Yes. The intermediate cooling sheet metal 60 is provided between the power transformer 42 and the main circuit board 20 and cools the power transformer 42 and the main circuit board 20. The upper cooling metal plate 70 is provided between the power transformer 42 and the upper case 12 a and is configured to cover the power transformer 42. The lower cooling metal plate 72 is provided between the main circuit board 20 and the lower case 12b, and is configured to cover a portion of the main circuit board 20 where the power transformer 42 is disposed.

  First, the intermediate cooling metal plate 60 includes a heat receiving plate portion 60a and a pair of heat radiating plate portions 60b raised from both sides of the heat receiving plate portion 60a. When the intermediate cooling sheet metal 60 is assembled between the power transformer 42 and the main circuit board 20, a heat receiving plate portion 60 a sandwiched between the power transformer 42 and the main circuit board 20 constitutes the main circuit board 20, which will be described later. While being connected to a heat generating element (for example, the switching element 34a), the pair of heat radiating plate portions 60b face each other so as to cover the power transformer 42 from both sides thereof.

  In this state, the heat generated from the heating element of the main circuit board 20 is radiated to the outside from the heat receiving plate portion 60a via the heat radiating plate portions 60b. Thereby, it is possible to efficiently cool all the heating elements or the main circuit board 20 and the power transformer 42.

  In the intermediate cooling sheet metal 60, a connecting portion 62 is formed on one of the heat radiating plate portions 60b (see FIG. 6). The connecting portion 62 is electrically and mechanically connected to a ground (not shown) formed on the main circuit board 20. The intermediate cooling metal plate 60 is grounded to the main circuit board 20 via the connection portion 62.

  Next, the upper cooling metal plate 70 has a substantially flat rectangular shape and covers the entire surface of the power transformer 42 and a part of the surface of the main circuit board 20. When the upper cooling metal plate 70 is assembled between the power transformer 42 and the upper case 12 a, a part of the upper cooling metal plate 70 is connected to the power transformer 42. In this state, the heat generated from the power transformer 42 is radiated to the outside through the upper cooling sheet metal 70. As a result, the power transformer 42 can be efficiently cooled.

  The lower cooling metal plate 72 has a substantially flat rectangular shape and covers the entire back surface of the main circuit board 20. The lower cooling metal plate 72 is provided with a plurality of convex portions 74 formed by drawing the lower cooling metal plate 72. When the lower cooling metal plate 72 is assembled between the main circuit board 20 and the lower case 12b, each convex portion 74 is connected to a heat generating element (for example, a switching element 34a, a control IC 34b) described later constituting the main circuit board 20. . In this state, heat generated from the heating elements of the main circuit board 20 is radiated to the outside through the lower cooling metal plate 72. Thereby, the main circuit board 20 can be efficiently cooled.

[Main circuit board 20]
As shown in FIGS. 2 to 5, the main circuit board 20 includes a printed circuit board 21 having a notch 21 a in part and a plurality of primary-side electronic components mounted on the printed circuit board 21. doing. Here, the printed circuit board 21 and a plurality of primary electronic components mounted on the printed circuit board 21 are referred to as a “primary circuit”.

  On the surface of the main circuit board 20, the printed circuit board 21 is generated from an AC / DC conversion circuit 22 that converts an AC voltage input via the input connector 14 into a DC voltage, and an AC / DC conversion circuit 22. A switching circuit (DC / AC conversion circuit) 24 for converting a DC voltage into a high-frequency AC voltage is provided.

  An input connector 14 is mounted on one side in the longitudinal direction of the printed circuit board 21, and a fuse 19 and a thermistor 23 are mounted adjacent to the input connector 14.

  The AC / DC conversion circuit 22 includes a choke coil 25 and an X capacitor 26 that reduce noise of an input AC voltage, a bridge diode 27 that rectifies the AC voltage to generate a DC voltage, a choke coil 28 that reduces noise in the circuit, A capacitor 29 and an electrolytic capacitor 30 for smoothing the rectified DC voltage are provided.

  These primary-side electronic components are integrated and mounted on one side in the longitudinal direction of the printed circuit board 21 except for the electrolytic capacitor 30. The electrolytic capacitor 30 is accommodated in the notch 21a described above, and is connected to the printed circuit board 21 in this state.

  On the other hand, on the back surface of the main circuit board 20, the printed circuit board 21 includes a plurality of semiconductor elements 32 constituting the AC / DC conversion circuit 22 and a plurality of semiconductor elements constituting the switching circuit 24 as primary electronic components. 34 is implemented. The respective semiconductor elements 32 are arranged in a concentrated manner on one side in the longitudinal direction of the printed circuit board 21, and the respective semiconductor elements 34 are arranged in a concentrated manner on the other side in the longitudinal direction of the printed circuit board 21.

  The plurality of semiconductor elements 34 include a plurality of switching elements 34a and heating elements such as one control IC 34b for controlling the ON / OFF timing of each switching element 34a. For example, a field effect transistor (FET), an insulated gate bipolar transistor (IGBT), or the like can be used as the switching element 34a. In the drawing, as an example, two switching elements 34 a are provided at the center in the longitudinal direction of the main circuit board 20.

[About power transformer 42]
As shown in FIGS. 2 to 4 and 7, the power transformer 42 includes a planar transformer in which coil windings are arranged on a plurality of layers of a substrate. The planar transformer is configured to include a transformer substrate 40 and a transformer unit 46 that is configured on the transformer substrate 40 and changes voltage, and is disposed to face the main circuit substrate 20. The functions of the transformer 46 include both a function for increasing the voltage and a function for decreasing the voltage. Here, as an example, a description will be given assuming that the transformer unit 46 has a function of reducing the voltage.

  The transformer substrate 40 includes a thin plate-like primary substrate 40a provided with a primary coil 80a and a separate primary substrate 40a, and a secondary coil 80b provided opposite the primary coil 80a. A thin plate-like secondary substrate 40b. The primary substrate 40a is formed with one primary through hole 82a that penetrates the central portion of the primary substrate 40a into an elliptical shape. One secondary through hole 82b is formed in the secondary substrate 40b. The secondary through hole 82b penetrates the central portion of the one side region into an elliptical shape. The primary through hole 82a and the secondary through hole 82b have the same size and shape.

  The primary coil 80a is formed of a conductor pattern that is wound in a planar shape along the periphery of the primary through hole 82a. The secondary coil 80b is formed of a conductor pattern wound in a planar shape along the periphery of the secondary through hole 82b. As a method for forming the coils 80a and 80b, for example, a core base material (not shown) in which through holes 82a and 82b are formed in advance is prepared. The surface of the core substrate is plated with copper (first step). Etching is performed along a predetermined pattern on the copper-plated core substrate (second step). An insulating coating is applied to the surface of the etched core base material (third step). By the first to third steps, the first layer conductor pattern is formed.

  By repeating the first to third steps a plurality of times, a multilayer substrate in which a plurality of conductor patterns are laminated is formed. As a result, it is possible to configure the primary substrate 40a composed of a multilayer substrate in which conductor patterns of the required number of layers are stacked as the primary coil 80a. Similarly, a secondary substrate 40b composed of a multilayer substrate in which conductor patterns of the required number of layers are stacked as the secondary coil 80b can be configured. In this embodiment, the number of layers in which the winding of the primary coil 80a is arranged is N1, the number of layers in which the winding of the secondary coil 80b is arranged is N2, and the layer in which the secondary circuit 86 described later is arranged. When the number is N3, the relationship of N1 + N2> N3 is satisfied.

  Here, it is assumed that the voltage is lowered in the transformer 46, and a voltage higher than that of the secondary coil 80b is applied to the primary coil 80a. For this reason, the number of turns of the primary coil 80a is set to be larger than the number of turns of the secondary coil 80b.

  The transformer 46 prevents electromagnetic interference between the primary and secondary coils 80a and 80b described above, the first and second transformer cores 46a and 46b disposed opposite to each other, and the primary and secondary coils 80a and 80b. And a shield member 84. The first and second transformer cores 46a and 46b can be formed of a magnetic material such as ferrite, for example. The shield member 84 can be formed of a material (for example, a copper foil, a metal mesh, an amorphous alloy, or the like) that can avoid the influence of electromagnetic waves that can be noise.

The first transformer core 46a is formed as an E-type core having an E-shaped cross section. That is, in the first transformer core 46a, an elliptical convex portion 46c protruding from the facing surface 46s is provided at the center of the facing surface 46s facing the second transformer core 46b. Furthermore, rectangular leg portions 46d extending in parallel along the protruding direction of the convex portions 46c are provided on both sides of the facing surface 46s. The convex portion 46c has the same shape or a slightly smaller shape as each of the through holes 82a and 82b of the substrates 40a and 40b.
The second transformer core 46b is formed as an I-type core having an I-shaped cross section with no irregularities on the surface. That is, the outline of the second transformer core 46b is rectangular and flat.

  The shield member 84 is provided between the primary substrate 40a and the secondary substrate 40b so as to face both the primary coil 80a and the secondary coil 80b, and includes one shield through hole 84h and one notch. 84g. The shield through-hole 84h is formed by penetrating the central portion of the ruled member 84 into an oblong shape. The cutout 84g is formed by cutting out a part of the ruled member 84 continuously from the outer periphery to the shield through hole 84h. Thereby, the shield member 84 is configured as a thin plate member or a thin film member having a C-shaped outline.

  Here, the primary and secondary substrates 40a, 40b are arranged on both sides of the shield member 84 so that the through holes 84h, 82a, 82b are aligned with each other. The first transformer core 46a is disposed outside the primary substrate 40a. The second transformer core 46b is disposed outside the secondary substrate 40b so as to face the primary substrate 40a. Then, the convex portion 46c of the first transformer core 46a is inserted into each of the through holes 84h, 82a, and 82b, and the tip of the convex portion 46c is brought into contact with the second transformer core 46b. As a result, the primary and secondary coils 80a and 80b wound in a plane are stacked between the first and second transformer cores 46a and 46b connected to each other via the convex portion 46c and the pair of leg portions 46d. The transformer unit 46 is configured.

  According to the transformer unit 46, the primary and secondary coils 80a and 80b are magnetically coupled to each other by the first and second transformer cores 46a and 46b. When the AC voltage generated by the main circuit board 20 having the primary circuit described above is applied to the primary coil 80a, the voltage is stepped down from the secondary coil 80b by the electromagnetic induction action in the transformer 46. AC voltage is output. The AC voltage output from the secondary coil 80b is converted into a low-voltage DC voltage by a secondary circuit 86 (described later) connected to the secondary coil 80b.

  Further, in the secondary substrate 40b, the other side region for providing the entire secondary circuit 86 is set in a region opposite to the one side region where the above-described secondary through hole 82b is formed. The secondary circuit 86 connected to the secondary coil 80b is provided on the secondary substrate 40b in the other side region.

  In this case, an area for providing all or part of the primary circuit connected to the primary coil 80a is not set in the secondary substrate 40b. In other words, not all of the primary circuit may be provided on the secondary substrate 40b, or a part of the primary circuit may be provided. Whether the primary circuit is not provided at all on the secondary substrate 40b or only a part is provided depends on the purpose and environment of use of the power transformer 42 and the AC / DC converter (power supply device) 10. Set accordingly.

  The secondary circuit 86 of the secondary board 40b includes a wiring pattern (not shown) formed at a creeping distance from the transformer unit 46 and a plurality of secondary-side electronic components mounted along the wiring pattern. ing. Examples of the secondary electronic component include a diode 48 mounted on the surface of the secondary substrate 40b, a control IC 50, a capacitor 52, a photocoupler 54, and a plurality of semiconductor elements 56 mounted on the back surface of the secondary substrate 40b. Is included.

  The diode 48 constitutes a rectifier circuit that generates a DC voltage by rectifying the AC voltage output from the transformer 46. The capacitor 52 constitutes a smoothing circuit that smoothes the generated DC voltage. The smoothing circuit smoothes the DC voltage and outputs it to the output cable 16.

  The control IC 50 detects the DC voltage output from the smoothing circuit, and sends a detection signal corresponding to the DC voltage to the photocoupler 54. The photocoupler 54 includes a light emitting unit that emits light based on a detection signal output from the control IC 50, and a light receiving unit that is disposed to face the light emitting unit with a predetermined gap therebetween. When the light receiving unit receives the light emitted from the light emitting unit, the light receiving unit outputs the detection signal to the control IC 34 b of the main circuit board 20. The input terminal of the light emitting unit and the output terminal of the light receiving unit are provided apart from each other by a predetermined creepage distance. A slit 55 is formed in the vicinity of the photocoupler 54, and an insulating plate 57 is provided in the slit 55.

  As shown in FIGS. 2 and 3, the main circuit board 20 is provided with a plurality of connection pins 58a, 58b, 58c, 58d, 58e, and 58f. The power transformer 42 is supported by each connection pin. As a result, the power transformer 42 is positioned on the main circuit board 20 via a slight gap (see FIG. 6).

  Further, each connection pin described above is in contact with the power transformer 42. Thereby, the main circuit board 20 and the power transformer 42 are electrically connected via the connection pins. For example, the output terminal of the switching circuit 24 of the main circuit board 20 and the primary coil 80a of the power transformer 42 are electrically connected via the connection pins 58a, 58b, 58c, and 58d. The control IC 34b of the main circuit board 20 and the output terminal of the light receiving unit of the photocoupler 54 provided in the power transformer 42 are electrically connected via connection pins 58e and 58f.

  According to the AC / DC converter (power supply device) 10 including the power transformer 42 described above, for example, when an AC voltage of 100 V is input via the input connector 14, the AC / DC conversion circuit 22 of the main circuit board 20. Smoothes the input AC voltage and converts it to a DC voltage. This DC voltage is supplied from the AC / DC conversion circuit 22 to the switching circuit 24. The switching circuit 24 switches the supplied DC voltage to generate a high-frequency AC voltage. This AC voltage is supplied from the switching circuit 24 to the power transformer 42.

  In the power transformer 42, the transformer 46 steps down the AC voltage supplied from the switching circuit 24 to about 20V, for example. The rectifier circuit rectifies the AC voltage stepped down by the transformer unit 46. The smoothing circuit smoothes the AC voltage rectified by the rectifier circuit and outputs the smoothed voltage to the output cable 16 as a DC voltage.

  The power transformer 42 is provided with a control circuit for keeping the DC output voltage constant. The control circuit performs feedback control of the switching circuit 24 described above to adjust switching. That is, a detection signal corresponding to the DC output voltage of the power transformer 42 is fed back from the control IC 50 to the control IC 34 b of the main circuit board 20 via the photocoupler 54. Based on this detection signal, the control IC 34b controls the ON / OFF timing of the switching element 34a to adjust the switching. Thereby, the DC voltage output to the output cable 16 is kept constant.

  As described above, according to the present embodiment, it is possible to reduce the size or thickness of the secondary board 40b in the portion where the secondary circuit 86 is provided in the transformer board 40 including the primary and secondary boards 40a and 40b. it can.

More specifically, if the thickness of the substrate layer in the portion where the secondary circuit 86 is provided is T in the apparent thickness of the secondary substrate 40b (distance from the upper end to the lower end of the substrate), the thickness T is calculated by multiplying the number N3 of layers in which the secondary circuit 86 is arranged by the thickness D3 of each layer. That is, T = N3 × D3.
Of the apparent thickness of the primary substrate 40a (distance from the upper end to the lower end of the substrate), when the thickness of the substrate layer in the portion where the winding of the primary coil 80a is disposed is W1, the thickness W1 is It is calculated by multiplying the number N1 of layers in which the windings of the primary coil 80a are arranged by the thickness D1 of each layer. That is, W1 = N1 × D1.
Of the apparent thickness of the secondary substrate 40b (distance from the upper end to the lower end of the substrate), when the thickness of the substrate layer in the portion where the winding of the secondary coil 80b is disposed is W2, the thickness W2 is It is calculated by multiplying the number N2 of layers in which the windings of the secondary coil 80b are arranged by the thickness D2 of each layer. That is, W2 = N2 × D2.

In this case, normally, the thicknesses D1, D2, and D3 of the layers in the secondary circuit 86 and the primary coil 80a and the secondary coil 80b coincide with each other. That is, D1 = D2 = D3.
Therefore, in the present embodiment, when the thicknesses D1, D2, and D3 of the layers coincide with each other, the above-described thicknesses T, W1, and W2 satisfy the relationship of T <W1 + W2.

  Here, a case where a secondary circuit is constructed on one substrate laminated so that the primary coil and the secondary coil face each other will be considered. The number of layers in which the winding of the primary coil is arranged is N1 ′, the number of layers in which the winding of the secondary coil is arranged is N2 ′, and the number of layers in which the secondary circuit is arranged is N3 ′.

  In this case, when the relationship of N1 ′ + N2 ′ ≧ N3 ′ is established, the number of layers of the one substrate coincides with the total number of layers of the substrate in the coil portion where the primary coil and the secondary coil are laminated. . Further, when the relationship N1 ′ + N2 ′> N3 ′ is established in the one substrate, the number of layers of the substrate in the secondary circuit portion is the number of layers necessary to construct the secondary circuit portion. The surplus part exceeding will be included. In such a case, in the specification in which the primary coil, the secondary coil, and the secondary circuit are provided on one board, the manufacturing cost of the surplus portion is always added, so that there is a limit to the cost reduction and miniaturization of the board itself. .

  On the other hand, in this embodiment, the transformer substrate 40 is divided into the primary substrate 40a and the secondary substrate 40b, and the secondary circuit 86 is provided on the secondary substrate 40b. The thickness T can be reduced to the number of layers necessary to construct the secondary circuit 86 or the number of layers necessary to construct the secondary coil 80b. Thereby, in this embodiment, the number of layers in which the winding of the primary coil is arranged is N1, the number of layers in which the winding of the secondary coil is arranged is N2, and the number of layers in which the secondary circuit is arranged is N3. , N1 + N2> N3 is satisfied, the transformer substrate 40 itself can be reduced in cost and size (compact).

  Further, according to the present embodiment, the primary circuit board 40a and the secondary circuit board 40b are configured to overlap only in the above-described transformer unit 46, whereby the secondary circuit 86 is provided on the secondary circuit board 40b. A wide space can be secured. Thereby, the mounting efficiency of the secondary-side electronic component with respect to the secondary circuit 86 can be dramatically improved.

  Furthermore, according to the present embodiment, the secondary coil 80b and the secondary circuit 86 can be directly connected on the secondary substrate 40b. Thereby, the reliability about electrical connection can be improved dramatically.

  Furthermore, according to the present embodiment, the primary substrate 40b provided with the primary coil 80a and the secondary substrate 40b provided with the secondary coil 80b are configured separately from each other. The next coil 80b can be maintained separately and independently. Thereby, in the case of the transformer substrate in which the primary coil and the secondary coil are integrally laminated, since maintenance of only one coil cannot be performed, there is a limit in reducing the maintenance cost. Since the maintenance for each of the coils 80a and 80b can be performed, the maintenance cost can be greatly reduced.

  Furthermore, according to this embodiment, the freedom degree of selection of the shield member 84 can be improved. That is, a shield member applicable to a single transformer substrate in which a primary coil and a secondary coil are laminated is limited to a thin film that can be patterned similarly to each coil. On the other hand, as in the present embodiment, the transformer substrate 40 is divided into the primary substrate 40a and the secondary substrate 40b, and the shield member 84 is sandwiched therebetween, so that the thin-film shield member 84 ( For example, not only a copper foil and a metal mesh) but also a thick film shield member 84 (for example, an amorphous alloy) can be applied.

  In this case, the shield member 84 can be selected in accordance with the purpose and environment of use of the power transformer 42. Thereby, it is possible to reliably prevent electromagnetic noise from flowing from the secondary coil 80b toward the primary coil 80a. As a result, it is possible to realize a highly reliable power supply transformer 42 with excellent transformation accuracy and an AC / DC converter (power supply device) 10 incorporating the power transformer 42.

  The above-described embodiment is presented as an example, and is not intended to limit the scope of the invention. The novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. The one embodiment and its modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  In the above-described embodiment, the power transformer 42 in which the primary substrate 40a is laminated on one side of the secondary substrate 40b is assumed, but instead of this, although not particularly illustrated, the primary transformer 40 is provided on both sides of the secondary substrate 40b. A power transformer in which substrates are stacked can also be applied. In the power transformer according to this modification, the primary coils provided on both the primary boards are connected to each other via through holes formed at positions avoiding the secondary coils. Similarly to the above-described embodiment, a shield member that prevents electromagnetic interference may be provided between the primary substrate and the secondary substrate so as to face both the primary coil and the secondary coil.

10 ... AC / DC converter (power supply), 14 ... input connector, 16 ... output cable,
20 ... main circuit board, 22 ... AC / DC conversion circuit, 24 ... switching circuit,
34a ... switching element, 34b ... control IC, 40 ... transformer substrate,
40a ... primary board, 40b ... secondary board, 42 ... power transformer, 46 ... transformer section,
46a ... first transformer core, 46b ... second transformer core, 60 ... intermediate cooling sheet metal,
60a ... heat receiving plate part, 60b ... heat radiating plate part, 70 ... upper cooling sheet metal, 72 ... lower cooling sheet metal,
80a ... primary coil, 80b ... secondary coil, 82a ... primary through hole, 82b ... secondary through hole,
84 ... Shield member, 84h ... Shield through hole, 84g ... Notch

Claims (10)

A power transformer including a planar transformer in which coil windings are arranged on a plurality of layers of a substrate,
A primary substrate provided with a primary coil of the planar transformer;
A secondary substrate configured separately from the primary substrate and provided with a secondary coil of the planar transformer facing the primary coil;
A power transformer in which a plurality of layers of the secondary substrate are provided with a secondary circuit connected to the secondary coil. The number of layers in which the primary coil is arranged is N1,
The number of layers in which the secondary coil is arranged is N2,
When the number of layers in which the secondary circuit is arranged is N3,
The power transformer according to claim 1, wherein a relationship of N1 + N2> N3 is satisfied.   The power transformer according to claim 1 or 2, wherein each of the primary coil and the secondary coil is formed of a conductor pattern wound in a planar shape.   The power transformer according to any one of claims 1 to 3, wherein a region for providing all or part of the primary circuit connected to the primary coil is not set on the secondary substrate.   The shield member for preventing electromagnetic interference is provided between the primary substrate and the secondary substrate so as to face both the primary coil and the secondary coil. A power transformer according to claim 1. A main circuit board provided with a primary circuit;
A power transformer including a planar transformer in which coil windings are arranged on a plurality of layers of a substrate,
The power transformer is
A primary substrate provided with a primary coil of the planar transformer to which the primary circuit is connected;
A secondary substrate configured separately from the primary substrate and provided with a secondary coil of the planar transformer facing the primary coil;
The power supply apparatus in which the secondary circuit connected to the said secondary coil is provided in the some layer of the said secondary substrate. The number of layers in which the primary coil is arranged is N1,
The number of layers in which the secondary coil is arranged is N2,
When the number of layers in which the secondary circuit is arranged is N3,
The power supply device according to claim 6, wherein a relationship of N1 + N2> N3 is satisfied.   The power supply device according to claim 6 or 7, wherein each of the primary coil and the secondary coil is formed of a conductor pattern wound in a planar shape.   The power supply device according to any one of claims 6 to 8, wherein an area for providing all or part of a primary circuit connected to the primary coil is not set on the secondary substrate.   The shield member for preventing electromagnetic interference is provided between the primary substrate and the secondary substrate so as to face both the primary coil and the secondary coil. The power supply device according to claim 1.

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