JP2023120801A - Transformer - Google Patents

Abstract

To provide a transformer in which a plurality of flat surface coils are laminated, that reduces a parasitic capacitance.SOLUTION: A transformer is a transformer in which eight flat surface coils of a first coil to an eight coil are laminated in this order. When one end of each coil is named as an A end, and the other end is named as a B end, the following relationship is established. The A ends of the first coil and the eight coil are connected to a first input end on a primary side. The B end of the first coil, the B end of the eight coil, the A end of the fourth coil, and the A end of the fifth coil are connected. The B ends of the fourth coil and the fifth coil are connected to a second input end on the primary side. The A ends of the second coil and the sixth coil are connected to a first output end on a secondary side. The B end of the second coil and the A end of the third coil are connected. The B end of the sixth coil and the A end of the seventh coil are connected. The B ends of the third coil and the seventh coil are connected to a second output end on the secondary side. Since the second coil and the third coil which are adjacent become the same electric potential, no parasitic capacitance occurs between them.SELECTED DRAWING: Figure 1

Description

The technology disclosed in this specification relates to transformers. In particular, it relates to a transformer in which a plurality of planar coils are stacked.

Transformers are known in which a plurality of planar coils with windings wound in a plane are stacked (Patent Documents 1 to 3, Non-Patent Document 1). It is known that in a transformer in which planar coils are stacked, the AC resistance of the windings increases as the magnetomotive force of the primary coil (or the secondary coil side) increases (Non-Patent Document 1).

Therefore, Non-Patent Document 1 proposes the following structure in order to suppress the AC resistance. Each of the primary coil and the secondary coil is realized by a plurality of planar coils connected in series. The planar coils on the primary side and the planar coils on the secondary side are alternately laminated. A plurality of primary coils and a plurality of secondary coils are alternately stacked one by one. The magnetomotive force generated in the primary coil is consumed by the adjacent secondary coils. Therefore, the magnetomotive force of the entire primary coil is reduced. By stacking the primary coil and the secondary coil, the magnetomotive force is canceled out, the magnetomotive force in the entire transformer is reduced, and the AC resistance is suppressed. According to Non-Patent Document 1, the above structure also has the effect of reducing leakage inductance.

JP 2019-096725 A JP 2013-168401 A JP 2009-105180 A

Riccardo Pittini, Zhe Zhang, Michael A.E. Andersen : “High Current Planar Transformer for Very High Efficiency Isolated Boost DC-DC Converters”, Proceedings of IEEE The 2014 International Power Electronics Conference, pp. 3905-3912, 2014

When a plurality of planar coils are stacked, a parasitic capacitance is generated due to a potential difference between adjacent planar coils. Parasitic capacitance affects transformer performance. In particular, in a transformer through which high-frequency current flows, parasitic capacitance increases the power loss that occurs in the transformer. Parasitic capacitance also lowers the drive frequency of the transformer. The present disclosure provides a transformer that reduces AC resistance and also reduces parasitic capacitance.

One aspect of the transformer (10, 10a) disclosed in this specification is embodied in a transformer in which eight planar coils from the first coil (11) to the eighth coil (18) are stacked in this order. . For convenience of explanation, one end of each coil will be referred to as the A end and the other end will be referred to as the B end. The electrical connections of the eight planar coils are as follows. The A terminals of the first coil and the eighth coil are connected to the first input terminal on the primary side. The B ends of the first and eighth coils and the A ends of the fourth coil (14) and the fifth coil (15) are connected at one point. The B terminals of the fourth coil and the fifth coil are connected to the second input terminal on the primary side. The A terminals of the second coil (12) and the sixth coil (16) are connected to the first output terminal on the secondary side. The B end of the second coil is connected to the A end of either the third coil (13) or the seventh coil (17). The B end of the sixth coil is connected to the other A end of the third coil or the seventh coil. The B terminals of the third coil and the seventh coil are connected to the second output terminal on the secondary side. As a modification, the B ends of the second and sixth coils and the A ends of the third and seventh coils may be connected.

The first, fourth, fifth and eighth coils correspond to primary coils. A plurality of primary coils can be electrically represented by one equivalent coil. The second, third, sixth and seventh coils correspond to secondary coils. A plurality of secondary coils can be electrically represented by one equivalent coil. The eight-layer transformer described above is electrically equivalent to a transformer composed of one primary coil and one secondary coil.

On the other hand, physically, both the primary coil and the secondary coil are composed of four planar coils, which are stacked. Since the primary coil and the secondary coil are alternately laminated, the AC resistance is reduced. Also, the fourth coil and the fifth coil are electrically connected in parallel. Therefore, the fourth coil and the fifth coil have the same potential, and even if the fifth coil is stacked next to the fourth coil, no parasitic capacitance is generated between them. The above connection relationship reduces parasitic capacitance.

Another aspect of the transformer disclosed herein is embodied in a transformer (20) in which six planar coils from a first coil (21) to a sixth coil (26) are stacked in that order. Also in this case, for convenience of explanation, one end of each coil is called the A end, and the other end is called the B end. The electrical connections of the six planar coils are as follows. The A terminals of the first coil and the sixth coil are connected to the first input terminal on the primary side. The B ends of the first and sixth coils and the A ends of the third coil (23) and the fourth coil (24) are connected at one point. The B terminals of the third coil and the fourth coil are connected to the second input terminal on the primary side. The A terminal of the second coil (22) is connected to the first output terminal on the secondary side. The B end of the second coil and the A end of the fifth coil (25) are connected. The B terminal of the fifth coil is connected to the second output terminal on the secondary side.

In the six-layer transformer described above, the third coil and the fourth coil are stacked next to each other, but they are electrically connected in parallel, so no parasitic capacitance is generated in the third coil and the fourth coil. .

This specification also provides techniques for improving the heat dissipation of stacked planar coils. Each planar coil comprises a winding pattern (11) formed on a substrate and a heat dissipation pattern (34). A heat radiation pattern is formed on the substrate so as to surround the winding pattern. Also, the heat radiation pattern is insulated from the winding pattern. A heat dissipation pattern surrounding the winding pattern diffuses the heat of the winding pattern. It is more preferable to have a thermal connection member (35) in contact with the plurality of laminated heat dissipation patterns. Since a plurality of heat radiation patterns are thermally connected via the thermal connection member, the heat of the winding pattern is diffused in the stacking direction. Winding patterns are effectively cooled.

The transformer disclosed in this specification is particularly suitable for implementation on a multi-layer PCB (Print Circuit Board). Each planar coil is embodied in a conductive pattern on a multi-layer PCB substrate. Details and further improvements of the technique disclosed in this specification are described in the following "Mode for Carrying Out the Invention".

1 is a circuit diagram of a transformer of a first embodiment; FIG. 3 is an equivalent circuit diagram of the transformer of the first embodiment; FIG. 1 is a plan view of a transformer of a first embodiment; FIG. 4 is a cross-sectional view of the transformer cut along line IV-IV of FIG. 3; FIG. 4 is a cross-sectional view of the transformer cut along line VV in FIG. 3; FIG. It is a circuit diagram of a transformer of a second embodiment. It is a circuit diagram of a transformer of a third embodiment. FIG. 11 is a cross-sectional view of a transformer of a third embodiment;

(First Embodiment) A transformer 10 of a first embodiment will be described with reference to FIGS. 1 to 5. FIG. FIG. 1 is a circuit diagram of a transformer 10. As shown in FIG. FIG. 1 shows one application example of the transformer 10, in which a DC/DC converter 2 is configured by the transformer 10, a DC/AC conversion circuit 50, and a rectifier circuit 60. FIG. A DC/AC conversion circuit 50 is connected to the primary side (input terminals 19a, 19b) of the transformer 10, and a rectifying circuit 60 is connected to the secondary side (output terminals 19c, 19d) of the transformer 10. FIG. The rectifier circuit 60 is a bridge type rectifier circuit.

The DC/DC converter 2 is a device that converts the voltage of input DC power. FIG. 1 shows an example in which a DC power supply 98 is connected to the input terminals 50a and 50b of the DC/DC converter 2, and a load device 99 is connected to the output terminals 60a and 60b of the DC/DC converter 2. . In FIG. 1, load device 99 is represented by the symbol of a resistor. Load device 99 is, for example, a DC motor.

As shown in FIG. 1, the DC/AC conversion circuit 50 is composed of four switching elements 51a to 51d, and a DC power supply 98 is connected to the input terminals 50a and 50b thereof. The output terminal of the DC/AC conversion circuit 50 is connected to the input terminals 19 a and 19 b of the transformer 10 . The DC/AC conversion circuit 50 appropriately turns on and off the four switching elements 51 a to 51 d to convert the DC power output from the DC power supply 98 into AC power and supply the AC power to the transformer 10 .

The rectifier circuit 60 is composed of four switching elements 61a to 61d, a reactor 62, and a smoothing capacitor 63, as shown in FIG. The rectifier circuit 60 converts AC power supplied from the transformer 10 into DC power and outputs the DC power from output terminals 60a and 60b. A load device 99 that operates on DC power is connected to the output terminals 60a and 60b.

Since the DC/AC conversion circuit 50 and the rectification circuit 60 in FIG. 1 are well known, detailed description thereof will be omitted.

The transformer 10 will be explained. The transformer 10 is composed of eight coils 11-18, converts the voltage of AC power input to the input terminals 19a and 19b on the primary side, and outputs the converted voltage to the output terminals 19c and 19d on the secondary side. . The coils 11 and 18 are connected in parallel, and the coils 14 and 15 are also connected in parallel. A parallel connection of the coils 11 and 18 and a parallel connection of the coils 14 and 15 are connected in series. Coils 11 , 14 , 15 , and 18 correspond to coils on the primary side of transformer 10 .

Coils 12 , 13 , 16 and 17 correspond to coils on the secondary side of transformer 10 . Coils 12 and 16 are connected in parallel, and coils 13 and 17 are connected in parallel. A parallel connection of the coils 12 and 16 and a parallel connection of the coils 13 and 17 are connected in series.

A circuit that is electrically equivalent to transformer 10 is shown in FIG. Transformer 10 of FIG. 1 is electrically equivalent to transformer 100 of FIG. Transformer 100 is the simplest transformer composed of one primary coil 101 and one secondary coil 102 . The entire circuit of coils 11, 14, 15, 18 of FIG. 1 is electrically equivalent to the primary coil 101 of FIG. 2, and the entire circuit of coils 12, 13, 16, 17 of FIG. It is electrically equivalent to coil 102 . However, a special effect can be obtained by configuring the primary side and the secondary side with a plurality of coils, respectively, as shown in FIG.

The connection relationship of the eight coils 11-18 will be described in detail. An enlarged view of the circuit of transformer 10 is shown at the bottom of FIG. For convenience of explanation, each of the eight coils 11-18 will be referred to as the first coil 11, the second coil 12, the third coil 13, the fourth coil 14, the fifth coil 15, the sixth coil 16, the seventh coil 17, It is called the eighth coil 18 . Each coil has two ends, but for convenience of explanation, one end of the coil will be called the A end and the other end will be called the B end. The terms "A end"/"B end" are used because they are easier to call than simply "one end"/"other end". The A end of the first coil 11 is denoted by reference numeral 11a, and the B end thereof is denoted by reference numeral 11b. The same applies to other coils.

The connection relationship of the eight coils 11-18 is as follows. A-ends 11a and 18a of the first coil 11 and the eighth coil 18 are connected to a first input terminal 19a on the primary side. The B-end 11b of the first coil 11, the B-end 18b of the eighth coil 18, the A-end 14a of the fourth coil 14, and the A-end 15a of the fifth coil 15 are connected. The B ends 14b and 15b of the fourth coil 14 and the fifth coil 15 are connected to the second input end 19b on the primary side. As described above, the first coil 11 and the eighth coil 18 are connected in parallel, and the fourth coil 14 and the fifth coil 15 are also connected in parallel. The parallel connection of coils 11 and 18 and the parallel connection of coils 14 and 15 are connected in series. Coils 11 , 14 , 15 and 18 constitute the primary side of transformer 10 .

The A ends 12a and 16a of the second coil 12 and the sixth coil 16 are connected to the first output end 19c on the secondary side. The B end 12b of the second coil 12 and the A end 13a of the third coil 13 are connected. The B end 16b of the sixth coil 16 and the A end 17a of the seventh coil 17 are connected. The B ends 13b and 17b of the third coil 13 and the seventh coil 17 are connected to the second output end 19d on the secondary side. The second coil 12 and the third coil 13 are connected in series, and the sixth coil 16 and the seventh coil 17 are also connected in series. The series connection of the second coil 12 and the third coil 13 and the series connection of the sixth coil 16 and the seventh coil 17 are connected in parallel. Coils 12 , 13 , 16 and 17 constitute the secondary side of transformer 10 .

All of the eight coils 11-18 are planar type coils (planar coils 30). FIG. 3 shows a plan view of the transformer 10. As shown in FIG. The transformer 10 has a core 39, which is drawn in phantom lines in FIG. 3 so that the structure of the first coil 11 can be seen.

The planar coil 30 is realized by a spiral winding pattern of copper foil on an insulating substrate 31 . To aid understanding, the winding pattern is drawn with a thick line in FIG. The winding pattern in FIG. 3 corresponds to the first coil 11 . The winding pattern is formed on one surface of the substrate 31, and the A-end 11a of the first coil 11 is the outermost end of the spiral winding pattern and is formed on the same surface as the winding pattern. ing. The B end 11b is located at the innermost side of the spiral winding pattern. The B end 11b is led to the outside of the winding pattern through the back surface of the substrate 31. As shown in FIG.

A heat radiation pattern 34 is formed on the substrate 31 so as to surround the winding pattern of the first coil 11 . To aid understanding, the heat dissipation pattern 34 is represented by gray hatching in FIG. The heat radiation pattern 34 is also made of copper foil, but is insulated from the spiral winding pattern corresponding to the first coil 11 .

A through hole 32 is provided in the center of the substrate 31 (the center of the winding pattern), and a through hole 33 is provided in the substrate 31 outside the winding pattern. FIG. 4 shows a cross section taken along line IV--IV of FIG. In FIG. 4, illustration of the right half from the center line CL is omitted. In FIG. 4, some of the planar coils 30 have their component numbers omitted.

A core 39 penetrates the plurality of laminated substrates 31 . The core penetrating through the through-holes 32 and the core 39 penetrating through the through-holes 33 are connected on both sides of the plurality of substrates 31 in the stacking direction.

The substrate 31 , the winding pattern corresponding to the first coil 11 , and the heat radiation pattern 34 are collectively referred to as a planar coil 30 .

All eight coils 11-18 have the same structure as the planar coil 30 of FIG. As shown in FIG. 4, eight planar coils 30 are stacked. In FIG. 4, the helical winding pattern (that is, the coils 11-18) is drawn as a simple rectangle for simplification. The stack of planar coils 30 is preferably implemented on a multi-layer PCB (Print Circuit Board). Each planar coil 30 is embodied in a conductive pattern on a multi-layer PCB board.

The transformer 10 is a laminate of eight planar coils 30 . The eight planar coils 30 all have the same structure, but in order to correspond to the circuit diagram of FIG. They are associated with the eight coils 11-18 in order from the end. That is, the eight coils 11-18 shown in FIG. 1 are stacked in this order.

Advantages of the transformer 10 having the connection relationship shown in FIG. 1 and the structure shown in FIGS. 3 and 4 will be described. In general, when a transformer is realized by stacking a plurality of planar coils, the size of the transformer can be reduced. However, on the other hand, parasitic capacitance is generated between adjacent planar coils. Parasitic capacitance degrades transformer performance. In particular, the higher the frequency of the alternating current flowing through the transformer, the greater the loss due to parasitic capacitance. When the frequency of the alternating current supplied to the transformer exceeds the cutoff frequency defined by the parasitic capacitance and coil inductance, the transformer ceases to function.

In the transformer 10 of the embodiment, as shown in FIG. 4, the fourth coil 14 and the fifth coil 15 are adjacent to each other. Since the fourth coil 14 and the fifth coil 15 are connected in parallel, they have the same potential. Therefore, no parasitic capacitance occurs in the fourth coil 14 and the fifth coil 15 adjacent to each other. The transformer 10 of the first embodiment can suppress parasitic capacitance in a transformer embodied by a laminate of planar coils.

Other advantages of transformer 10 are described. Generally, it is known that the greater the magnetomotive force of the primary coil (or the secondary coil), the greater the influence of the proximity effect in the laminate of planar coils, and the greater the winding AC resistance. By parallelizing the coils of the transformer 10, the magnetomotive force per coil can be reduced while obtaining the same inductance as in the case of a single coil. In addition, the primary side coil and the secondary side coil are alternately laminated. The magnetomotive force generated in the planar coil 30 on the primary side is canceled by the adjacent planar coil 30 on the secondary side. Therefore, winding AC resistance can be suppressed.

Furthermore, the second coil 12 and the third coil 13 connected in series are laminated so as to be adjacent to each other. Since the conduction path connecting the second coil 12 and the third coil 13 is shortened, the internal resistance of the transformer 10 can be reduced. The serially connected sixth coil 16 and seventh coil 17 are also arranged adjacent to each other in the laminate. The conduction path connecting the sixth coil 16 and the seventh coil 17 is shortened, and the internal resistance of the transformer 10 can be further reduced.

The effect of the heat dissipation pattern 34 formed on the substrate 31 of each planar coil 30 will be described. The heat dissipation pattern 34 is made of copper foil and has excellent heat dissipation. The first coil 11 generates heat when alternating current flows. The heat of the winding pattern that constitutes the first coil 11 is diffused to the outside through the heat dissipation pattern 34 that surrounds the winding pattern. The heat radiation pattern 34 has the advantage of effectively diffusing the heat of the first coil 11 .

Each of the plurality of laminated planar coils 30 has a heat radiation pattern 34 . The transformer 10 includes metal pins 35 that pass through a plurality of stacked planar coils 30 . FIG. 5 shows a cross section along line VV of FIG. 5 shows a cross section of the transformer 10 cut along a plane passing through the center CL of the coil 11 (12-18) and the metal pin 35. FIG. In FIG. 5 as well, the illustration of the right side of the center line CL is omitted. The metal pin 35 is in contact with all the laminated heat dissipation patterns 34 . A plurality of heat dissipation patterns 34 are thermally connected via metal pins 35 . The metal pin 35 diffuses the heat of the plurality of winding patterns (coils 11-18) in the stacking direction. The coils 11-18 are effectively cooled by the plurality of heat radiation patterns 34 and the metal pins 35 in contact with them.

The metal pin 35 penetrates the substrate 31 and the heat dissipation pattern 34 in each planar coil 30 . The metal pin 35 corresponds to a thermal connection member that thermally couples with the plurality of heat dissipation patterns 34 .

(Second Embodiment) FIG. 6 shows a circuit diagram of a DC/DC converter 2a including a transformer 10a of a second embodiment. The transformer 10a is different from the first embodiment in that the B-end 12b of the second coil 12, the B-end 16b of the sixth coil 16, the A-end 13a of the third coil 13, and the A-end 17a of the seventh coil 17 are connected. is different from the transformer 10 of Otherwise, the connection structure of the transformer 10a is the same as that of the transformer 10. FIG. The physical structure of the transformer 10a is shown in FIGS. 3 and 4. FIG.

The connection point of the B-end 12b of the second coil 12, the B-end 16b of the sixth coil 16, the A-end 13a of the third coil 13, and the A-end 17a of the seventh coil 17 is the center tap 19e on the secondary side of the transformer 10a. corresponds to

The transformer 10a of the second embodiment has a center tap 19e on the secondary side. Therefore, the secondary side of the transformer 10a is connected with a rectifier circuit 70 having a three-pole input terminal. The rectifier circuit 70 is composed of two switching elements 71 a and 71 b, a reactor 72 and smoothing capacitors 73 and 74 . Rectifier circuit 70 is also a well-known general circuit. The transformer 10a of FIG. 6 also has the same advantages as the transformer 10 of the first embodiment.

(Third Embodiment) A transformer 20 of a third embodiment will be described with reference to FIGS. FIG. 7 is a circuit diagram of the DC/DC converter 2b including the transformer 20. As shown in FIG. Like the DC/DC converter 2 of the first embodiment, the DC/DC converter 2b is also a device that changes the voltage of the input DC power and outputs it. A DC/AC conversion circuit 50 is connected to the primary side of the transformer 20, and a rectifying circuit 70 is connected to the secondary side.

8 is a longitudinal sectional view of the transformer 20. FIG. In FIG. 8 as well, the illustration of the right side of the center line CL is omitted. The transformer 20 has a structure in which six planar coils 30 are stacked. Each of the planar coils 30 has the same structure as the planar coil 30 of the first embodiment. For convenience of explanation, the six planar coils 30 are referred to as the first to sixth coils 21 to 26, respectively. Six planar coils 30 (first coil 21 to sixth coil 26) are stacked in this order (see FIG. 8).

The connection relationship of the six coils 21 to 26 will be described with reference to FIG. The A ends 21a and 26a of the first coil 21 and the sixth coil 26 are connected to the first input end 29a on the primary side. The B end 21b of the first coil 21, the B end 26b of the sixth coil 26, the A end 23a of the third coil 23, and the A end 24a of the fourth coil 24 are connected. The B ends 23b and 24b of the third coil 23 and the fourth coil 24 are connected to the second input end 29b on the primary side. The A end 22a of the second coil 22 is connected to the first output end 29c on the secondary side. The B end 22b of the second coil 22 and the A end 25a of the fifth coil 25 are connected. A connection point between the B end 22b of the second coil 22 and the A end 25a of the fifth coil 25 corresponds to the center tap 29e on the secondary side. The B end 25b of the fifth coil 25 is connected to the second output end 29d on the secondary side.

In the transformer 20 of the third embodiment, the second coil 12 and the sixth coil 16 connected in parallel in the transformer 10 of the first embodiment are replaced with one coil (second coil 22) and connected in parallel. The third coil 13 and the seventh coil 17 are replaced with another coil (the fifth coil 25). That is, the transformer 20 has a simplified secondary side structure in the transformer 10 .

As shown in FIG. 8, the first coil 21 to the sixth coil 26 are laminated in this order. The third coil 23 and the fourth coil 24 are adjacent to each other. On the other hand, as shown in FIG. 7, since the third coil 23 and the fourth coil 24 are connected in parallel, they have the same potential. Therefore, no parasitic capacitance occurs between the third coil 23 and the fourth coil 24 adjacent to each other. The transformer 20 of the third embodiment also has the effect of reducing the parasitic capacitance.

Points to note regarding the technology described in the embodiment will be described. In FIG. 1, the third coil 13 and the seventh coil 17 may be interchanged. That is, the B end 12b of the second coil 12 is connected to the A end of one of the third coil 13 or the seventh coil 17, and the B end 16b of the sixth coil 16 is connected to the third coil 13 or the seventh coil. The other A terminal of 17 should just be connected.

The black dot in the transformer symbol represents the polarity of the coil. In FIG. 1, the first input terminal 19a corresponds to the positive electrode of the primary side, and the second input terminal 19b corresponds to the negative electrode of the primary side. The first output end 19c corresponds to the positive electrode on the secondary side, and the second output end 19d corresponds to the negative electrode on the secondary side.

In FIG. 1, the A terminals of the primary side coils 11, 14, 15 and 18 are positive terminals, and the A terminals of the secondary side coils 12, 13, 16 and 17 are positive terminals. The B ends of the coils 11, 14, 15 and 18 on the primary side may be made positive. Alternatively, the B ends of the secondary coils 12, 13, 16 and 17 may be made positive.

The thermal coupling member represented by the metal pin 35 may be made of a material with high thermal conductivity. The thermal coupling member may be made of a material having thermal conductivity comparable to that of copper or aluminum.

The heat dissipation pattern 34 may be connected to the circuit ground. A heat radiation pattern that is formed of a conductive pattern and surrounds the winding pattern functions as a magnetic shield that blocks electromagnetic waves emitted by the winding pattern (coil).

The DC/DC converter 2 (2a, 2b) of the embodiment can be expressed as follows. The DC/DC converter 2 (2a, 2b) includes a transformer having the characteristics described above, a DC/AC circuit connected to the primary side (input end) of the transformer, and connected to the secondary side (output end) of the transformer. and a rectifier circuit.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or in the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims as of the filing. In addition, the techniques exemplified in this specification or drawings can simultaneously achieve a plurality of purposes, and achieving one of them has technical utility in itself.

2, 2a, 2b: DC/DC converters 10, 10a, 20: transformers 11-18, 21-26: coils 19a, 19b, 29a, 29b: input terminals 19c, 19d, 29c, 29d: output terminals 19e, 29e: Center tap 30: Planar coil 31: Substrate 32, 33: Through hole 34: Heat dissipation pattern 35: Metal pin 39: Core 50: DC/AC conversion circuit 50a, 50b: Input terminal 51a-51d, 61a-61d, 71a-71d : switching element 60, 70: rectifier circuit 60a, 60b: output terminal 62, 72: reactor 63, 73, 74: capacitor 98: DC power supply 99: load device 100: transformer 101: primary coil 102: secondary coil

Claims (5)

A transformer (10, 10a) in which eight planar coils from the first coil (11) to the eighth coil (18) are stacked in this order, one end of each coil is the A end and the other end is the B end. when called
A terminals of the first coil and the eighth coil are connected to a first input terminal on the primary side,
The B end of the first coil, the B end of the eighth coil, the A end of the fourth coil (14) and the A end of the fifth coil (15) are connected,
B terminals of the fourth coil and the fifth coil are connected to the second input terminal on the primary side,
A terminals of the second coil (12) and the sixth coil (16) are connected to the first output terminal on the secondary side,
The B end of the second coil is connected to the A end of one of the third coil (13) or the seventh coil (17),
The B end of the sixth coil is connected to the other A end of the third coil or the seventh coil,
B ends of the third coil and the seventh coil are connected to the second output end of the secondary side,
Trance. The transformer (10a) according to claim 1, wherein the B ends of the second and sixth coils and the A ends of the third and seventh coils are connected. A transformer (20) is formed by stacking six planar coils from a first coil (21) to a sixth coil (26) in this order, and one end of each coil is called an A end and the other end is called a B end. when
A terminals of the first coil and the sixth coil are connected to a first input terminal on the primary side,
The B end of the first coil, the B end of the sixth coil, the A end of the third coil (23) and the A end of the fourth coil (24) are connected,
B terminals of the third coil and the fourth coil are connected to the second input terminal on the primary side,
The A terminal of the second coil (22) is connected to the first output terminal on the secondary side,
The B end of the second coil and the A end of the fifth coil (25) are connected,
the B end of the fifth coil is connected to the second output end of the secondary side;
Trance. Each planar coil is
a winding pattern (11) formed on the substrate;
a heat radiation pattern (34) formed on the substrate so as to surround the winding pattern and insulated from the winding pattern;
4. A transformer according to any one of claims 1 to 3, comprising: 5. A transformer according to claim 4, comprising a thermal coupling member (35) in contact with a plurality of stacked heat dissipation patterns.

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