JP3402573B2 - Transformer and power supply - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer and a power supply, and more particularly to a transformer suitable for noise suppression and a power supply using the same.

[0002]

2. Description of the Related Art A so-called switching power supply utilizing switching such as an inverter or a chopper is widely used as a power supply for electronic equipment. The switching power supply includes a DC (direct current) -DC converter and an AC (alternating current) -D.
There are various types such as C converters, AC inverters, and AC choppers.

A typical switching power supply converts alternating current by switching a direct current power supply input, and
Step up the voltage with a transformer and rectify and smooth it to obtain the required DC power. The DC power supply input may be obtained directly from the DC power supply or may be obtained by rectifying and smoothing the AC power supply output.

This type of switching power supply has the advantage that the required power output can be obtained with high efficiency and stability, and the power supply itself can be made compact. Therefore, the switching power supply is
It is used as a power source for many electronic devices such as computer-related digital devices.

However, this type of switching power supply has a problem that noise generated due to switching is large. The noise generated by the switching power supply will be specifically described. FIG. 13 shows a configuration of a switching power supply that supplies DC power to a load based on AC power of a commercial power supply, and FIG. 14 shows an equivalent circuit of the configuration of FIG.

The switching power supply shown in FIG.
It has a switching circuit 1, a transformer 2 and a rectifying circuit 3. The rectification / switching circuit 1 rectifies an input from a commercial power source once to convert it into a direct current, then switches the input, and supplies it to a rectification circuit 3 via a transformer 2. Rectifier circuit 3
The output that appears on the secondary side of the transformer 2 is rectified again by switching and is supplied to the load 4 as DC power.

In the circuit of FIG. 13, noise sources are the rectification / switching circuit 1 and the commercial power supply. As shown in FIG. 14, the noise current generated from these noise sources is supplied to the load 4 via the coupling capacitance of the transformer 2. Further, the noise current also flows into the commercial power supply.

If the coupling capacitance of the transformer 2 is small, it becomes difficult for the noise current to flow to the load 4. As a result, the noise current itself becomes small, so that the outflow of noise to the commercial power supply also becomes small. Therefore, in the transformer 2 for the switching power supply, it is desirable to reduce the coupling capacitance in order to reduce the influence of noise.

On the other hand, the transformer 2 is constructed by winding a primary coil and a secondary coil around an iron core or core. As the core, for example, an EI type core as shown in FIG. 15 is widely used.

The EI type core is formed by combining the E type core, the I type core and the "H" shape. In the E-shaped core, a pair of upper and lower outer peripheral leg portions 7 and 8 are provided upright at both ends of the yoke portion 5 at right angles to the longitudinal direction of the yoke portion 5. The outer peripheral legs 7 and 8 are arranged parallel to each other and facing each other vertically. A central leg portion 9 is provided at the center of the yoke portion 5 in parallel with the outer peripheral leg portions 7 and 8. The I-shaped core is composed of a linear yoke portion 6.

A magnetic gap is formed between the outer peripheral legs 7 and 8 of the E-shaped core portion 10 and the respective tip surfaces of the central leg portion 9 and the side surface of the I-shaped core 6 to prevent DC magnetic saturation. There is.

As shown in FIG. 16, a primary coil 11 and a secondary coil 12 are wound around the EI type core shown in FIG. The primary coil 11 is wound around the first bobbin 13. The first bobbin 13 around which the primary coil 11 is wound is
The E-shaped core portion 10 has a length substantially equal to that of the central leg portion 9 and an inner dimension slightly larger than the outer dimension of the central leg portion 9, and is fitted to the central leg portion 9.

One or more, for example, four secondary coils 12 are wound around the second bobbin 14. The second bobbin 14 on which the secondary coil 12 is wound has a length substantially equal to that of the primary coil 11 wound on the first bobbin 13 and an inner shape that is slightly larger than the outer dimensions of the primary coil 11. Have dimensions. The second bobbin 14 is fitted on the primary coil 11 on the first bobbin 13.

Each winding end of the first and second coils 11 and 12 is drawn out to a lead-out terminal portion 15 provided on a flange at one end of the first bobbin 13 and connected to an external circuit.

As described above, in addition to the method of winding the primary coil and the secondary coil on different bobbins, a method of winding the secondary coil on the primary coil via an insulating sheet or the like, or A method of winding a primary coil and a secondary coil together with a bifilar has been used.

[0016]

As described above, in the conventional transformer for the switching power supply, the primary coil 11 and the secondary coil 12 are wound so as to be in close contact and overlap with each other as shown in FIG. It was By taking such a structure. The electromagnetic coupling between the primary coil 11 and the secondary coil 12 is improved, and the loss of magnetic flux is reduced.

However, the primary coil 11 and the secondary coil 12
Since and are in close contact, the coupling capacitance between both coils is also large. Therefore, as described above, the influence of noise is increased.

Also, in the transformer, an EI type core as shown in FIG. 15 is mainly used, but in this type of core, a magnetic gap exists in the outer peripheral portion. Therefore, the magnetic flux generated inside the transformer leaks to the outside from the magnetic gap in the outer peripheral portion. This leakage magnetic flux adversely affected adjacent components and circuits arranged near the transformer.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a transformer capable of reducing noise current. Another object of the present invention is to provide a transformer that can prevent direct current magnetic saturation while maintaining high AC magnetic coupling and reduce leakage flux to the outside.

[0020]

In order to achieve the above object, a transformer according to a first aspect of the present invention is a transformer in which a pair of yokes facing each other and a leg portion for connecting and connecting both ends of the pair of yokes. A core composed of a pair of outer peripheral legs made of a piece, an intermediate leg having a magnetic gap and connecting intermediate portions of the pair of yokes, and a core wound around a part of the intermediate leg And a second coil wound around the intermediate leg so as not to overlap with the first coil.

According to this structure, since there is no gap in the outer peripheral portion of the core and the magnetic gap is arranged in the intermediate leg around which the coil is wound, it is possible to prevent magnetic leakage to the outside. Moreover, since the first and second coils are wound so as not to overlap each other, the electrostatic coupling capacitance between the first and second coils is small. Therefore, the noise current can be reduced.

The intermediate leg portion is composed of, for example, a pair of leg pieces that are provided so as to project from the pair of yokes and are arranged substantially parallel to each other with a gap forming a magnetic gap therebetween. In this case, it is preferable that the leg pieces forming the intermediate leg portion face the other yoke with a gap wider than the magnetic gap. With such a structure, magnetic leakage can be reduced.

The core is, for example, a combination of F-shaped cores, a combination of E-shaped cores, an E-shaped core and a T-shaped core.
Combining with a letter-shaped core, etc.

For example, the first coil is wound around a first bobbin forming a first coil layer, and the second coil is wound around a second bobbin forming a second coil layer. It has been turned.

In order to achieve the above object, the transformer according to the second aspect of the present invention is such that between a pair of yokes facing each other, a pair of outer peripheral leg portions for connecting both ends of each yoke and each yoke. A core formed of intermediate legs connecting the intermediate portions of the first coil, a first coil wound to form a first coil layer on a part of the intermediate legs in the longitudinal direction, and the intermediate coil. A second coil wound around the other part of the leg in the longitudinal direction to form a second coil layer on the outer circumference of the first coil layer and wound so as not to overlap the first coil. It is characterized by: Also, the first and second
One or both of the coils may be composed of a plurality of coils.

According to this structure, the first and second coils do not overlap. That is, the layers of the coil are different, and further, the positions of the intermediate leg portions in the longitudinal direction are also different. Therefore, the capacitance between the first coil and the second coil is small, and the coupling between the primary side and the secondary side due to the capacitance is small. Therefore, noise is reduced. For example, the first coil is wound around a first bobbin forming a first coil layer, and the second coil is wound around a second bobbin forming a second coil layer. It will be done.

In the transformer according to the third aspect of the present invention, a pair of yokes facing each other and at least one of the yokes are provided so as to project, and both ends of the pair of yokes are connected to each other and closely coupled to each other. And a pair of outer peripheral leg portions formed of leg pieces, which project from the pair of yokes, are spaced apart from each other in the longitudinal direction to form a magnetic gap, and form a magnetic gap between the intermediate portions of the pair of yokes. It is characterized in that it is provided with a core composed of an intermediate leg portion to be connected.

According to this structure, the magnetic gap is formed by the gap between the side surfaces of the intermediate leg portion projecting from both yokes, and there is no magnetic gap in the outer peripheral portion. Therefore, magnetic leakage can be prevented. In this case, it is preferable that the intermediate leg portion is configured to face the other yoke with a gap wider than the magnetic gap.

In the power source according to the fourth aspect of the present invention, a switching circuit for generating an alternating current by switching a direct current voltage, a pair of yokes facing each other, and both ends of the pair of yokes are connected. And a pair of outer peripheral leg portions formed of leg portions that are coupled together, an intermediate leg portion that has a magnetic gap and connects between the intermediate portions of the pair of yokes, a core that is configured, and a part of the intermediate leg portion First wrapped around
And a second coil wound around the intermediate leg so as not to overlap with the first coil. It is characterized by comprising a transformer to which an AC voltage from a switching circuit is applied and a rectifying circuit for rectifying the output of the second coil.

According to this structure, the electrostatic coupling capacitance between the first coil and the second coil is small. Therefore, it is possible to prevent the noise (high frequency noise) generated by switching from flowing through the electrostatic coupling capacitance. Therefore, a power supply with less noise can be provided.

The rectifier circuit is composed of, for example, a switching circuit.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. A transformer according to a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows the configuration of a transformer according to the first embodiment of the present invention. The transformer shown in FIG. 1 includes a core portion 21 and a coil portion 22. The core portion 21 includes a pair of F-shaped cores 31 and 3 as shown in FIG.
Have two. The coil portion 22 has a primary coil 41, a secondary coil 42, a first bobbin 43, a second bobbin 44, and a lead-out portion 45, as shown in FIGS. 3 and 4.

As shown in FIGS. 1 and 2, the F-type core 31
And 32 are formed by laminating magnetic material plates such as F-shaped ferrite, for example, and yoke portions 33 and 34,
Outer peripheral legs 35 and 36 and central leg pieces 37 and 38 are provided, respectively.

An outer peripheral leg portion 35 is provided at one end of the yoke portion 33 of the first F-shaped core 31, that is, at the upper end in the figure, and the yoke portion 3 is provided.
3 is provided upright at right angles to the longitudinal direction. At the center of the yoke portion 33, a central leg piece 37 is erected in parallel with the outer peripheral leg portion 35. The yoke portion 34 of the second F-shaped core 32
At one end, that is, the lower end in the figure, an outer peripheral leg portion 36 is erected at a right angle to the longitudinal direction of the yoke portion 34. A central leg piece 38 is provided upright in the center of the yoke portion 34 in parallel with the outer peripheral leg portion 36.

These first and second F-type cores 31 and 3
2 are arranged on the left and right sides in the drawing so that the yoke portions 33 and 34 face each other in parallel, and are arranged at the upper and lower sides in the drawing so that the outer peripheral leg portions 35 and 36 face each other in parallel. The tips of the outer peripheral legs 35 and 36 are respectively the F-shaped core 32 of the other party.
And the side surfaces of the yoke portions 34 and 33 of the contact holes 31 and 31, respectively.

The central leg pieces 37 and 38 are arranged in parallel with each other with a gap t forming a magnetic gap. Since the central leg pieces 37 and 38 form the central leg portion, the central leg pieces 37 and 38 have a cross-sectional area of about ½ of the cross-sectional area of the central leg portion to be originally formed, except for the required magnetic gap. That is, the central leg portion has a structure in which it is divided into two parts by the magnetic gap.

Furthermore, the tips of the central leg pieces 37 and 38 face the side surfaces of the yoke portions 34 and 33 of the F-shaped cores 32 and 31 of the opposite sides through the required gaps s1 and s2. In order to effectively prevent magnetic flux leakage, rather than the magnetic gap t formed between the central leg pieces 37 and 38,
It is desirable that the gap s1 between the front end surface of the center leg piece 37 and the yoke portion 34 and the gap s2 between the front end surface of the center leg piece 38 and the yoke portion 33 are formed wider.

In this manner, the F-shaped cores 31 and 32 form a core portion 21 in which a rectangular yoke whose outer peripheral portion is in close contact is formed and a magnetic gap is formed in the middle portion of the central leg portion.

On the other hand, the coil portion 22 has a primary coil 41, a secondary coil 42, a first bobbin 43, a second bobbin 44, and a lead-out portion 45, as shown in FIGS. .

The primary coil 41 is wound around the first bobbin 43, and the secondary coil 42 is wound around the second bobbin 44.

The first bobbin 4 around which the primary coil 41 is wound.
3 is a length substantially equal to the length of the central leg formed by the central leg pieces 37 and 38 of the core 21 and the magnetic gap, that is, the distance between the pair of yoke portions 33 and 34, and the central leg portion. It has an inner dimension that is slightly larger than the outer dimension of. The first bobbin 43 is fitted in close contact with the central leg portion.

The second bobbin 4 around which the secondary coil 42 is wound.
4 has a length substantially equal to the portion of the primary coil 41 wound around the first bobbin 43 and an inner dimension slightly larger than the outer dimension of the primary coil 41. Second bobbin 44
Is closely fitted onto the primary coil 41 on the first bobbin 43.

The primary coil 41 is provided in a part along the axis of the first bobbin 43, that is, in the left-right direction in the drawing.
It is wrapped while leaving the other part. The secondary coil 42 is
The second bobbin 44 is wound in a direction along the axis of the second bobbin 44, that is, in a part in the left-right direction in the drawing while leaving the other part. The secondary coil 42 is wound around a portion corresponding to a portion left unwound from the primary coil 41, and the primary coil 4
The portion where 1 is wound corresponds to the portion where the secondary coil 42 is left unwound. That is, the primary coil 41 and the secondary coil 42 form different coil layers and are wound without overlapping each other.

As shown in FIG. 4, the winding ends of the first and second coils 41 and 42 are drawn out to a lead-out terminal portion 45 provided on the flange portion at one end of the first bobbin 43. In the lead-out terminal portion 45, the winding ends of the first and second coils 41 and 42 are connected to an external circuit.

As described above, the primary coil 41 and the secondary coil 42 form different coil layers and are wound without overlapping each other. Therefore, the coupling capacitance between the primary coil 41 and the secondary coil 42 is sufficiently small, and the effect of noise when used in a switching power supply or the like is effectively reduced. Further, since the outer peripheral portion of the core portion 21 is in close contact and the magnetic gap is arranged inside the coil portion 22, the AC magnetic coupling is kept high and the leakage magnetic flux to the outside is small.

The primary coil 41 and the secondary coil 42 may each be composed of a plurality of coils. For example,
The secondary coil 42 may be composed of a plurality of coils, and the connection point of each coil may be drawn out as an intermediate tap.

FIG. 5 schematically shows the structure of the core portion 21A of the transformer according to the second embodiment of the present invention. The core portion 21A has E-shaped cores 51 and 52.
The E-shaped cores 51 and 52 are made of a magnetic material such as ferrite, and have yoke portions 53 and 54, first outer peripheral leg pieces 55 and 56, second outer peripheral leg pieces 57 and 58, and a central leg piece 5.
9 and 60 respectively.

At both ends of the yoke portion 53 of the first E-shaped core 51, first and second outer peripheral leg pieces 55 and 57 are erected at right angles to the longitudinal direction of the yoke portion 53. A central leg piece 59 is erected at the center of the yoke portion 53 in parallel with the outer peripheral leg pieces 55 and 57. The first and second outer peripheral leg pieces 56 and 58 are provided at both ends of the yoke portion 54 of the second E-shaped core 52, that is, at the lower upper end in the drawing.
Are erected at right angles to the longitudinal direction of each. A central leg piece 60 and an outer peripheral leg piece 56 are provided at the center of the yoke portion 54.
And is provided in parallel with 58.

The first and second E-shaped cores 51 and 52 are
The yoke portions 53 and 54 face each other in parallel, and the outer peripheral leg piece 55
And 58 and 57 and 56 are arranged to abut each other. The tips of the outer peripheral leg pieces 55 and 57 are in close contact with the tips of the corresponding outer peripheral leg pieces 58 and 56, respectively.

The central leg pieces 59 and 60 are the outer leg pieces 55 to 55.
It has a length slightly less than twice that of 58 and is arranged substantially parallel to each other with a gap forming a magnetic gap along the longitudinal direction. Since the central leg piece 59 forms the upper half portion of the central leg portion in the drawing, it has a half cross-sectional area of what is obtained by removing the portion corresponding to the required magnetic gap from the cross-sectional area of the central leg portion to be originally formed. . Since the central leg piece 60 forms the lower half of the central leg portion in the drawing, it has a cross-sectional area that is approximately 1/2 of the cross-sectional area of the central leg portion that should be originally formed, excluding the portion corresponding to the magnetic gap. In other words, the central leg portion has a structure in which it is vertically divided into two with a magnetic gap.

Further, the tips of the central leg pieces 59 and 60 face the side surfaces of the yoke portions 54 and 53 of the opposing E-shaped cores 52 and 51, respectively, with a required gap. Even in this way, it is possible to configure the core portion 21A that is substantially the same as that shown in FIGS.

FIG. 6 schematically shows the structure of the core portion 21B of the transformer according to the third embodiment of the present invention. The core portion 21B has an E-shaped core 61 and a T-shaped core 62. The E-shaped core 61 is made of a magnetic material such as ferrite, and includes a yoke portion 63, a first outer peripheral leg portion 65, a second outer peripheral leg portion 66, and a central leg piece 67. T type core 62
Is made of a magnetic material such as ferrite, and includes a yoke portion 64 and a central leg piece 68.

The first and second outer peripheral leg portions 65 and 6 are provided at both ends of the yoke portion 63 of the E-shaped core 61, that is, at the upper and lower ends in the figure.
6 stand upright at right angles to the longitudinal direction of the yoke portion 63. At the center of the yoke portion 63, the central leg piece 6
7 stands upright in parallel with the outer peripheral legs 65 and 66.
A central leg piece 68 is provided at the center of the yoke portion 64 of the T-shaped core 62.
Are erected at right angles to the longitudinal direction of the yoke portion 64.

The E-type core 61 and the T-type core 62 are
As illustrated, the yoke portions 63 and 64 are arranged on the left and right in the figure so as to face each other in parallel, and the outer peripheral leg portion 6 of the E-shaped core
The tips of 5 and 66 are respectively the yoke portion 6 of the T-shaped core 62.
It adheres to the both side surfaces of 4 respectively.

The central leg pieces 67 and 68 are composed of a pair of yokes 6.
3 and 64 are provided so as to protrude from each other and are arranged substantially parallel to each other along the longitudinal direction so as to form a magnetic gap,
The middle portions of the pair of yokes 63 and 64 are connected. The center leg pieces 67 and 68 are about 1 / th of those obtained by removing the corresponding magnetic gap from the cross-sectional area of the center leg portion to be originally formed.
It has a cross-sectional area of 2.

Further, the tips of the central leg pieces 67 and 68 face the side surface of the yoke portion 64 of the T-shaped core 62 with a required gap. Even in this case, it is possible to configure the core portion 21B that is substantially the same as that shown in FIGS.

FIG. 7 schematically shows the structure of the core portion 21C of the transformer according to the fourth embodiment of the present invention. The core portion 21C has E-shaped cores 71 and 72.
The E-shaped cores 71 and 72 are made of a magnetic material such as ferrite, and have yoke portions 73 and 74, first outer peripheral leg pieces 75 and 76, second outer peripheral leg pieces 77 and 78, and a central leg piece 7.
9 and 80 respectively.

At both ends of the yoke portion 73 of the first E-shaped core 71, first and second outer peripheral leg pieces 75 and 77 are erected at right angles to the longitudinal direction of the yoke portion 73. At the center of the yoke portion 73, a central leg piece 79 is provided upright in parallel with the outer peripheral leg pieces 75 and 77. The first and second outer peripheral leg pieces 76 are provided at both ends of the yoke portion 74 of the second E-shaped core 72.
And 78 are erected at right angles to the longitudinal direction of the yoke portion 74. A central leg piece 80 is provided at the center of the yoke portion 74.
Are erected parallel to the outer peripheral leg pieces 76 and 78.

Since the outer peripheral leg pieces 75 and 78 form the first outer peripheral leg portion, the outer peripheral leg pieces 75 and 78 have a cross-sectional area of approximately 1/2 of the cross-sectional area of the first outer peripheral leg portion which should be originally formed. The tips are in close contact with the side surfaces of the yoke portions 74 and 73 of the other party. It is desirable that the outer leg pieces 75 and 78 also be in close contact with each other.

Since the outer peripheral leg pieces 76 and 77 form the second outer peripheral leg portion, the outer peripheral leg pieces 76 and 77 have a cross-sectional area of about 1/2 of the cross-sectional area of the second outer peripheral leg portion which should be originally formed. The tips are in close contact with the side surfaces of the yoke portions 74 and 73 of the other party. It is desirable that the outer leg pieces 76 and 77 also be in close contact with each other. In other words, each of the first and second outer peripheral legs has a structure in which it is vertically divided into two parts and which are in close contact with each other.

Each of the central leg pieces 79 and 80 has a cross sectional area of about 1/2 of the cross sectional area of the central leg portion to be originally formed, excluding the required magnetic gap, and the tips thereof are The opposite side faces of the yoke portions 74 and 73 are faced with a required gap. Even in this case, the core portion 21C which is almost the same as that shown in FIGS.
Can be configured.

As shown in FIG. 8, the coil portion may be constructed by using the conventional bobbin shown in FIG. The coil portion 22A of the transformer according to the fifth embodiment of the present invention shown in FIG. 8 includes a primary coil 81, a secondary coil 82, and a first coil 81.
It has a bobbin 83, a second bobbin 84, and a lead-out portion 85.

The primary coil 81 is wound around the first bobbin 83, and the secondary coil 82 is wound around the second bobbin 84. The first bobbin 83 has a barrier tape 86 wound around a part of the bobbin 13 shown in FIG. The barrier tape 86 prevents the primary coil 81 from entering a portion corresponding to the secondary coil 82. In the second bobbin 84, a part 87 of the flange portion for partitioning the coil of the bobbin 14 of FIG. 16 is cut off to secure a winding position of the secondary coil 82. Therefore, the primary coil 81 and the secondary coil 82 do not overlap each other on the first coil layer and the second coil layer formed by the first bobbin 83 and the second bobbin 84, respectively. It is wrapped. The winding ends of the first and second coils 81 and 82 are
It is drawn out to a lead-out terminal portion 85 provided on a flange portion at one end of the first bobbin 83.

The first bobbin 83 has a length substantially equal to the length of the central leg portion of the core portion and an inner dimension slightly larger than the outer dimension of the central leg portion, and is in close contact with the central leg portion. Be fitted. The second bobbin 84 has an inner size that is slightly larger than the outer size of the primary coil 81.
It is closely fitted on the primary coil 81 on the upper part 3.

As described above, according to the embodiment of the present invention, the intermediate leg portions are provided so as to project from the pair of yokes and are arranged substantially parallel to each other with a predetermined gap therebetween.
Further, its tip faces the other yoke with a gap. Therefore, a magnetic gap with less magnetic leakage can be formed. Further, since the primary coil and the secondary coil are wound around the intermediate leg so that they do not overlap with each other (different coil layers and different winding positions), AC magnetic coupling is kept high and The electrostatic coupling capacitance between the secondary coil and the secondary coil is small.

The effect of the transformer according to the present invention was verified by experiments. The configuration of the measurement circuit used in the experiment is shown in FIG.
Shown in. In FIG. 9, a DC output is obtained from a commercial power supply of 100 V AC via a switching power supply. A 1 kΩ resistor was inserted between one power supply line of this DC output and a common potential (ground, that is, ground), and a voltage waveform based on noise current appearing at both ends of this resistor was observed with an oscilloscope. The experiment was conducted on the switching power supply.
When the core portion 21 equivalent to that of FIG. 2 is used and the coil portion 22 according to the present invention shown in FIG. 3 is used, and when the primary coil and the secondary coil are overlapped as shown in FIG. I went about.

FIG. 11A shows a voltage waveform when the coil portion 22 according to the present invention shown in FIG. 3 is used, and the vertical axis has a scale of 0.1V. FIG. 11B shows a waveform when the primary coil and the secondary coil are overlapped with each other as shown in FIG. 10, and the vertical axis has a scale of 1V.
Therefore, in the case of FIG. 11A, it can be seen that the noise is much less than in the case of FIG. 11B. Furthermore, in the conventional general switching power supply,
Noise that is one digit larger than that in the case of FIG. 11B, that is, about 10 times more noise is generated.

FIG. 12 shows frequency characteristics when the coupling capacitance between the primary coil and the secondary coil is measured. Characteristic C
0 indicates the coupling capacity of the transformer having the coil structure in which the primary coil and the secondary coil are overlapped as shown in FIG. 10, and the characteristic C indicates the coupling capacity of the transformer having the coil structure of FIG. 3 according to the present invention. ing.

As shown in FIG. 12, for example, at a frequency of 200 kHz, the characteristic C0 is 6.50 pF, while the characteristic C is 3.04 pF. According to the conventional coil structure, the coupling capacitance between the primary coil and the secondary coil is 1
It was about 00 pF, and it was confirmed that the use of the coil structure in FIG. 10 can significantly reduce the coupling capacitance as compared with the conventional structure. It was confirmed that by adopting the coil structure of FIG. 3, the coupling capacitance can be further reduced to half or less, and the coupling capacitance can be dramatically reduced as compared with the conventional one.

[0071]

As described above, according to the transformer of the present invention, it is possible to prevent the DC magnetic saturation while keeping the AC magnetic coupling in the transformer high, and to effectively reduce the leakage magnetic flux to the outside. Can be provided.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a transformer according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing in detail only a core portion of the transformer of FIG.

FIG. 3 is a schematic diagram showing in detail only a coil portion of the transformer of FIG.

FIG. 4 is a schematic diagram showing a more specific configuration of a coil unit of the transformer of FIG.

FIG. 5 is a schematic diagram showing a configuration of a core portion of a transformer according to a second embodiment of the present invention.

FIG. 6 is a schematic diagram showing a configuration of a core portion of a transformer according to a third embodiment of the present invention.

FIG. 7 is a schematic diagram showing a configuration of a core unit of a transformer according to a fourth embodiment of the present invention.

FIG. 8 is a schematic diagram showing a configuration of a coil part of a transformer according to a fifth embodiment of the present invention.

FIG. 9 is a block diagram schematically showing a measurement circuit used in an experiment for verifying the effect of the present invention.

FIG. 10 is a schematic diagram showing a configuration of a coil unit similar to a conventional configuration used in an experiment for verifying the effect of the present invention.

FIG. 11A is a diagram showing a noise waveform of the transformer of the present invention. (B) is a diagram showing a noise waveform of a transformer having a conventional coil structure.

FIG. 12 is a diagram showing frequency characteristics of the coupling capacitance of the primary coil and the secondary coil in the coil structure of the present invention and the conventional coil structure.

FIG. 13 is a block diagram for explaining the principle of noise generation in a switching power supply.

FIG. 14 is an equivalent circuit diagram of FIG.

FIG. 15 is a schematic diagram showing a configuration of a core portion of a conventional general transformer.

FIG. 16 is a schematic diagram showing a configuration of an example of a coil portion of a conventional transformer.

[Explanation of symbols]

21, 21A, 21B, 21C Core part 22, 22A Coil part 31, 32 F type core 33, 34 Yoke part 35, 36, Outer peripheral leg part 37, 38, 59, 60, 67, 68, 79, 80 Central leg piece 41,81 Primary coil 42,82 Secondary coil 43,44,83,84 Bobbin 45,85 Lead-out terminal part 51,52,61,71,72 E type core 55-58,65,66,75-78 Outer periphery Leg 62 T-shaped core 86 Barrier tape

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ identification code FI H01F 31/00 C (58) Fields investigated (Int.Cl. ⁷ , DB name) H01F 27/28 H01F 27/24 H01F 30 / 00 H02M 3/28

Claims (9)

(57) [Claims] 1. A pair of outer peripheral leg portions formed of a pair of yokes facing each other, a pair of leg portions connecting and connecting both ends of the pair of yokes, and a pair of outer peripheral leg portions protruding substantially between intermediate portions of the pair of yokes. Are provided and are spaced apart substantially parallel to each other along the longitudinal direction.
And a pair of intermediate legs that face each other by forming a second gap having a wider gap than the first gap between the second leg and the other yoke, and a core including: A first coil wound around a part of the intermediate leg, and a second coil wound around the intermediate leg so as not to overlap with the first coil; A transformer characterized by being configured. Wherein said core transformer of claim 1, F-shaped core is constructed by <br/> Is I set case, it is characterized. 3. The transformer according to claim 1, wherein the core is configured by combining E-shaped cores. 4. The transformer according to claim 1, wherein the core is configured by combining an E-shaped core and a T-shaped core. 5. The first coil is wound around a first bobbin forming a first coil layer, and the second coil is a second bobbin forming a second coil layer. The transformer according to any one of claims 1 to 4, wherein the transformer is wound around. 6. At least one of the first coil and the second coil is formed of a plurality of coils.
The transformer according to any one of claims 1 to 5, wherein: 7. A pair of yokes facing each other, and a pair of outer peripheral leg portions, which are provided on at least one of the yokes and project from the pair of leg portions, and connect and connect both ends of the pair of yokes to each other. Of the first yoke, the first yokes are provided so as to protrude substantially between intermediate portions of the yokes, and are arranged substantially parallel to each other along the longitudinal direction.
And a pair of intermediate leg portions facing each other by forming a second gap having a wider gap than the first gap between the second leg and the other yoke, and a core including: A first coil wound around a part of the intermediate leg, and a second coil wound around the intermediate leg so as not to overlap the first coil, and a coil comprising: A transformer characterized by being configured. 8. A switching circuit for generating alternating current by switching a direct current voltage, and the alternating voltage from the switching circuit is applied to the first coil, according to claim 1.
And a rectifying circuit that rectifies the output of the second coil. 9. The power supply according to claim 8, wherein the rectifier circuit is composed of a switching circuit.