JP2001345229A - Switching transformer coil structure - Google Patents

Abstract

(57) Abstract: Provided is a coil structure in which a primary transformer coil, a secondary transformer coil, a canceling coil, and a bias coil, which constitute a switching transformer coil, are improved in winding method and number of windings to reduce EMI. A primary transformer coil divided and wound into an innermost layer and an outermost layer adjacent to a ferrite core side, a cancel coil and a bias coil disposed outside the primary transformer coil in the innermost layer, and the cancel coil A secondary transformer coil is provided between the coil and the bias coil and the primary transformer coil in the outermost layer. The number of turns of the cancel coil and the bias coil is the same as the number of the primary transformer coils in the innermost layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a coil structure of a switching transformer, and more particularly to an EMI (Ele) of a Cuk converter in a switching transformer.
ctroMagnetic Interferenc
e) reducing the coil structure of the switching transformer.

[0002]

2. Description of the Related Art As shown in FIG. 5, an integrated magnetic structure for a switching transformer and an input / output inductor used in a Cuk converter according to the prior art surrounds an air gap 10 having a predetermined gap. Ferrite cores 2 arranged in four directions as shown in FIG.
0a, 20b, 20c, and 20d; a primary winding (primary transformer coil) 30 and a secondary winding (secondary transformer coil) 40, which are transformer coils formed by winding one ferrite core 20a in series. The ferrite core 20 on the side opposite to the ferrite core 20a
c, comprising an input inductor 50 wound at a position facing the primary winding and an output inductor 60 wound at a position facing the secondary winding 40, forming a closed magnetic circuit by the air gap 10. I do.

The circuit diagram of the integrated magnetics having such a structure is shown in FIG.
A primary transformer coil (terminals 3 and 4) 30 and a secondary transformer coil (terminals 7 and 8) 40 having a positional relationship facing each other with a transformer interposed therebetween, and a bias coil (5, 6) and a shield coil (line 5) 80, and an input inductor coil (lines 1 and 2) provided opposite to the transformer provided below the shield coil 80 with a transformer interposed therebetween.
90 and output inductor coil (line 9, 10)
91. Bias coil 70 is PW
Power is supplied to an IC or the like that performs M control. The shield coil 80 has a function of reducing the EMI by reducing the capacitance between the primary and the secondary of the transformer by the potential.

FIG. 7 shows a cross-section of a coil wound around a transformer. Half of the total number of turns of the primary transformer coil 30 is arranged from the ferrite core side, and the third terminal on the winding start side is arranged. Is the hot end.
A shield coil 70 and a bias coil 80 are arranged outside the primary transformer coil 30. The upper end is on the cold end side of the sixth terminal, the middle position is the hot end of the fifth terminal of the bias coil, and the lower end is The part becomes the cold end of “No Connect” of the shield coil 80. A secondary transformer coil 70 having a two-layer structure is disposed outside the shield and bias coils 70 and 80. The lower end on the inner side is the hot end of the eighth terminal and the lower end on the outer side is the cold end of the seventh terminal. The other half of the primary transformer coil 30 which forms the outermost layer outside the secondary transformer coil 40 is arranged, and the upper end is a fourth terminal and becomes a cold end.

FIG. 8 shows the winding direction of each coil and the state of the potential at the time of mounting the power supply. The arrow in the figure shows the winding direction. The end indicates the end of the winding. The directions of rotation at the start of winding are all the same. Dotted lines represent internal connection and return wiring. In addition, the numbers described at the ends of the dotted lines are the terminal numbers of the coils. The leftmost arrow indicates the coil area, from track 0 to track 10
This is a measure for expressing the potential state of the coil at a certain point in the coil area.

The manner of winding the windings of the transformer having such a structure will be described with reference to FIG. 7. Referring to FIG. 7, the primary transformer coil 30 is located on the track 10 side from the arrow side (ferrite core side) indicating the track. The winding starts from the terminal No., and reaches 1/2 of the total number of turns to the winding track 0. Then, it is inserted between the shield coil 70, the bias coil 80, and the secondary transformer coil 40 by using the interlayer connection, and the outermost layer starts winding from the track 0 side and the track 1
The winding ends at terminal 0 on the 0 side. When the power supply is mounted, the fourth terminal is on the cold end side.

The secondary transformer coil 40 includes an outermost primary transformer coil 30 and a shield coil 7.
0, sandwiched by the bias coil 80, start winding from the No. 8 terminal on the track 0 side from the center of the layer, and wrap around １ ／ of the total number of turns to reach the track 10. The layer is moved outward by one layer, and the remaining turns start to be wound from the track 10 side and end at the terminal 7 on the track 0 side. When mounting the power supply, 7
Terminal No. is on the cold end side.

[0008] Shield coil 70, bias coil 80
Is sandwiched between the innermost primary transformer coil 30 and the secondary transformer coil 40, and the shield coil 70 and the bias coil 80 are connected from the sixth terminal on the track 10 side, and the shield coil 70 is connected from the fifth terminal on the same side. Starting to wind with a bifilar, and reaching track 0, the shield coil 70 and bias coil 80
Returning to terminal 0 on the 0 side, the shield coil 70
Floating in the layer, the shield coil 80 of FIG.
And the same circuit configuration. When the power supply is mounted, the sixth terminal is on the cold end side.

FIG. 9 shows the potential gradient of each coil in the above-described structure. The hot end side of the primary transformer coil has a potential of 300 at track 0.
The voltage changes linearly to 600 V as it goes to the track 10 at V. The cold end side of the primary transformer coil changes linearly from a potential of 300 V at track 0 to a potential of 0 V toward track 10. On the hot end side of the secondary transformer coil 40, the potential is 100 V at the time of the track 0, but the potential 5
It changes linearly to around 0V. The cold end side of the secondary transformer coil 40 linearly changes from the potential 0 V to the potential 50 V toward the track 10 at the time of the track 0. The shield coil has a potential of −200 V at track 0, but has a potential of 0 V as it goes to track 10.
Changes linearly.

[0010]

However, the effect of EMI improvement can be confirmed to some extent by inserting a shield coil in the above-described transformer configuration in the prior art, but it is necessary to improve power supply efficiency, reduce the size, and reduce the cost when configuring the power supply. To achieve this, it is necessary to further improve EMI and reduce the number of EMI countermeasure components. As one of EMI mitigation measures, there is a problem that the device of the power transformer cannot be neglected.

Therefore, EMI should be improved in consideration of, for example, optimizing the insertion position and winding direction of the shield coil of the transformer and its potential, and focusing on the position and winding direction of another coil to be shielded. There is a problem that must be solved.

[0012]

In order to solve the above-mentioned problems, a switching transformer coil structure according to the present invention has the following structure.

(1) A primary transformer coil divided and wound into an innermost layer and an outermost layer adjacent to the ferrite core side, a cancel coil and a bias coil disposed outside the primary transformer coil in the innermost layer,
A secondary transformer coil provided between the cancel coil and the bias coil and the outermost primary transformer coil, wherein the number of turns of the cancel coil and the shield coil is the same as the number of turns of the innermost primary transformer coil or A coil structure of a switching transformer characterized by being substantially the same. (2) The winding direction of the hot end side of the innermost layer primary transformer coil, the cold end side of the outermost layer primary transformer coil, and the winding start side of the cancel coil and the bias coil are set to the same direction. (3) The canceling coil and the bias coil are divided into the same layer by using 2/3 of the entire winding area as a canceling coil and 1/3 of the entire winding area as a bias coil. The coil structure of the switching transformer according to (1) or (2), wherein the coil is wound. (4) The switching according to (3), wherein the cancel coil and the bias coil are arranged such that the cancel coil is positioned on the winding start side of the primary transformer coil and the bias coil is positioned on the winding end side of the primary transformer coil. Transformer coil structure.

Since the number of turns of the cancel coil and the bias coil is equal to the number of turns of the primary transformer coil and the winding direction is the same, the potential gradient of each coil can be made equal. Therefore, EMI can be reduced.

[0015]

Next, an embodiment of a coil structure of a switching transformer according to the present invention will be described with reference to the drawings.

The coil structure of the switching transformer of the present invention is the same as the structure of the integrated magnetics shown in FIG. 5 described in the prior art, and FIG. 1 shows a specific embodiment. FIG. The circuit configuration of the primary transformer coil 10
0, secondary transformer coils 110a and 110b, a cancel coil (corresponding to a shield coil in the related art) 120, and a bias coil 130.

FIG. 2 shows a cross section of the transformer, and the coil layer structure has a structure of 1/1 of the total number of turns of the primary transformer coil 100 from the ferrite core 150 side.
2, the third terminal on the upper side is a hot end, and the winding start side is arranged. Next, the cancel coil 120 and the bias coil 130 are arranged on the same layer by split winding at positions outside the primary transformer coil 100, the lower fifth terminal is a hot end, the upper fourth terminal is a cold end, and The cold end of "No Connect" of the cancel coil 120 is located at a slightly lower position,
A cold end of the sixth terminal of the bias coil 130 is provided below the lower end. The number of turns of the cancel coil 120 and the bias coil 130 is equal to or substantially equal to the number of turns of the primary transformer coil 100 in the innermost layer. Next, the secondary coils 110a and 110b are arranged in parallel using two layers outside of the cancel coil 120 and the bias coil 130, and the lower terminal 8 is a hot end and the upper terminal 7 is a cold end. Become. Next, the remaining の of the primary transformer coil 100 is arranged on the outermost layer outside the two layers, and the lower fourth terminal becomes a cold end.

FIG. 3 shows the winding direction of each coil and the state of the potential at the time of mounting the power supply in the specific embodiment.
The winding is started from the third terminal on the track 10 side, and is の of the total number of turns (60 turns in the embodiment) (3 in the embodiment).
0 turn) to reach track 0. Here, returning to the track 10 side, the cancellation coil 120, the bias coil 130, and the secondary transformer coils 110a and 110b are inserted therebetween using the interlayer connection. A turn (30 turns in the embodiment) is wound, and return wiring is made to the fourth terminal on the track 0 side. When the power is mounted, the fourth terminal is on the cold end side.

A secondary transformer coil (1 in the embodiment)
0 turns) 110a and 110b are sandwiched between the primary transformer coil 100, the cancel coil 120, and the bias coil 130 on the outermost layer, start winding from the No. 8 terminal on the track 0 side, and finish winding on the track 10 (10 turns in the embodiment). , Return line 7
Terminal. This is performed over two layers to form a parallel coil. When the power supply is mounted, the seventh terminal is on the cold end side.

The cancel coil 120 and the bias coil 130 are connected to the innermost primary transformer coil 100.
Between the secondary transformer coils 110a and 110b and the cancel coil 120
Start winding from terminal No. Here, the number of turns is the same as that of the opposing innermost layer primary transformer coil 100 (30 turns in the embodiment), and the winding area is 2 of the entire winding area.
/ 3, up to track 3. The end of the winding is made to float in the layer. The bias coil 130 starts to be wound from the track 3 where the cancel winding has been wound from the sixth terminal on the track 10 side (10 turns in the embodiment), ends at the track 0, and ends at the track 1 by return wiring.
Connect to terminal 5 on the 0 side. When the power is mounted, the fourth terminal is on the cold end side of the cancel coil 120, and the sixth terminal is on the cold end side of the bias coil 130.
Each coil wound in this manner is connected to the hot end side of the innermost primary transformer coil 100,
The winding direction of the cold end side of the outermost primary transformer coil 100 and the winding start side of the cancel coil 120 and the bias coil 130 are the same.
Also, the cancel coil 120 and the bias coil 130
Has a structure in which two-thirds of the entire winding area is used as the cancel coil 120, and one-third of the entire winding area is used as the bias coil 130, and is wound separately in the same layer. Further, the cancel coil 120 and the bias coil 130 have a structure in which the cancel coil 120 is positioned on the winding start side of the primary transformer coil 100 and the bias coil 130 is positioned on the winding end side of the primary transformer coil 100.

FIG. 4 is a graph in which the potential gradient of each coil is plotted according to the track, and can be compared with FIG. 9 of the prior art. The potential is calculated at 10 V per turn. The outermost primary transformer coil (the cold end side of the fourth terminal) goes from 0 V potential on the track 0 to the potential of 300 V on the track 10, and the innermost primary trans coil (hot end side of the third terminal) goes on the potential of the track 0. From 300 V to the potential 60 of the track 10
There is a potential ramp to 0V. The secondary transformer coil changes the potential of track 0 from 0 V to the potential of track 0 to 100
There is a V slope. As for the cancel coil and the bias coil, the cancel coil occupying 70% of the coil area is approximated as being on the entire surface of the coil area, and the bias coil can be ignored. At this time, the cancel coil changes the potential of the track 10 from 0 V to the potential of the track 0 −3.
The slope is 00V.

As described above, comparing the configuration of the transformer and the potential gradient (see FIG. 9) of the prior art with the configuration of the transformer and the potential gradient (see FIG. 4) of the improved embodiment, the cancellation coil and the shield coil are compared. The direction and inclination of the potential gradient of the primary transformer coil are improved, and in the embodiment, the inclinations are all the same. This means that the EMI can be improved by devising the winding direction and the number of turns of the coil without major structural changes. Ideally, it is desirable to use the entire winding area for the cancel coil and the shield coil, but at this time, the number of layers of the bias coil must be increased, and the transformer size becomes large. However, by configuring the cancel coil, the shield coil, and the bias coil in the same layer under certain conditions as in the improved embodiment, the effect of reducing EMI can be sufficiently obtained, and it is necessary to increase the transformer size. Absent.

As a specific effect, the EMI is improved by about 10 dB as compared with the current transformer when the power supply is mounted.
The improvement of 10 dB is so large that there is a margin even if the size of the inductor used in the EMI filter is reduced by one rank. Generally, the effect is that the projected area of the filter section is about 20% and the volume is about 40% in terms of inductance. Equivalent to shrinking. When mounted on a power supply, the filter occupies about 20% of the power supply, so that the area is reduced by about 4% and the volume is reduced by 8%. In terms of coil resistance, filter losses can be reduced by about 20 percent. When mounted on a power supply, the loss of the filter accounts for about 10% of the power supply loss, resulting in a loss improvement of about 2%. In particular, it is very effective for a power supply with a high power density and an AC adapter that compete for volume reduction and loss improvement of several percent.

[0024]

As described above, in the switching transformer coil structure according to the present invention, the number of turns of the cancel coil and the shield coil is equal to the number of the primary transformer coils in the innermost layer. Further, since the winding directions of the shield coils are set to the same direction, the potential gradient directions of the respective coils can be set to the same direction, so that EMI can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a coil of a switching transformer according to the present invention.

FIG. 2 is a sectional view of the transformer coil structure.

FIG. 3 is an explanatory diagram showing a winding direction of the transformer coil.

FIG. 4 is a graph showing a potential gradient of each coil.

FIG. 5 is an explanatory diagram showing the structure of a Cuk converter and integrated magnetics.

FIG. 6 is an explanatory diagram showing a circuit diagram of a Cuk converter and integrating magnetics in the related art.

FIG. 7 is a cross-sectional view of a coil structure of a Cuk converter and a transformer unit according to the related art.

FIG. 8 is an explanatory diagram showing a Cuk converter and a coil winding direction of a transformer unit in the conventional technique.

FIG. 9 is a graph showing a potential gradient of a coil of a Cuk converter and a transformer unit according to the related art.

[Explanation of symbols]

 100 Primary transformer coil 110a Secondary transformer coil 110b Secondary transformer coil 120 Cancel coil 130 Bias coil

Claims (4)

[Claims] A primary transformer coil divided and wound into an innermost layer and an outermost layer adjacent to a ferrite core side; a cancel coil and a bias coil arranged outside the primary transformer coil in the innermost layer; A secondary transformer coil provided between the cancel coil and the bias coil and the primary transformer coil in the outermost layer, wherein the number of turns of the cancel coil and the shield coil is equal to or substantially equal to the number of turns of the primary transformer coil in the innermost layer. A switching transformer coil structure characterized by the same features. 2. The method according to claim 1, wherein the winding direction of the hot end side of the innermost primary transformer coil, the cold end side of the outermost primary transformer coil, and the winding start side of the cancel coil and the bias coil are the same. The coil structure of a switching transformer according to claim 1, wherein: 3. The split coil according to claim 1, wherein the cancel coil and the bias coil are wound in the same layer with two-thirds of the entire winding area used as a cancel coil and one-third of the entire winding area used as a bias coil. Or the coil structure of the switching transformer according to 2. 4. The canceling coil and the bias coil according to claim 3, wherein the canceling coil is located at the winding start side of the primary transformer coil, and the bias coil is located at the winding end side of the primary transformer coil. Switching transformer coil structure.