JP4394557B2 - Transformers and multilayer boards - Google Patents

Description

  The present invention relates to a transformer having a planar winding used for a switching power supply and a multilayer substrate including at least a part of the transformer having a planar winding.

  Conventionally, a multilayer substrate provided with a transformer is widely used for a switching power supply used in various electronic devices including, for example, an IC (integrated circuit). In recent years, switching power supplies have been required to have a smaller current and higher efficiency as well as a larger current due to a decrease in IC operating voltage and an increase in current accompanying an increase in IC integration. Therefore, transformers used in switching power supplies are also required to be small and thin, improve transmission efficiency, and reduce loss. Recently, in order to reduce the size of a transformer, a printed coil or a planar coil has been used in place of a wound coil formed by winding a wire around a bobbin. For example, as shown in FIG. 10, the printed coil of the transformer 2 forms a multilayer body 4 made of a multilayer substrate in which substrates having flat conductors are stacked in a parallel direction, and a ferrite core 6 is fitted to the multilayer body 4. Configured. The substrate of each layer is a printed circuit board on which a coil is formed by a conductive pattern such as a copper foil on the surface, and the stacked body 4 is configured by laminating this printed circuit board. In addition, the planar coil may be configured by stacking a plurality of thin copper plates punched into a coil shape with an insulating layer interposed therebetween, for example. The coil of the transformer 2 has one turn of the winding of the secondary side conductor 8. In the lead-out portion 10 connected to the outside of the coil, a split groove 12 is provided between a pair of electrodes of the conductor forming the winding. It is separated. The interval between the divided grooves 12 is as narrow as possible to ensure insulation in each layer.

  Furthermore, recently, it has been attempted to reduce the size of the core by increasing the switching frequency in the switching power supply and lowering the maximum magnetic flux density in the core used for the transformer.

  By the way, the increase in the output current in the switching power supply increases the copper loss, which is a loss due to the winding, in the transformer. Further, the current flowing through the circuit also becomes high frequency due to the increase of the switching frequency in the switching power supply, and the AC resistance of the conductor constituting the coil of the transformer is increased due to the skin effect and the proximity effect. Furthermore, the increase in the output current and the increase in the switching frequency in the switching power supply also increase the loss in the conductor pattern connected to the secondary winding of the transformer. This is because as a result of the skin effect, the conductor loss increases around the coil where the effective cross-sectional area of the conductor decreases and the AC resistance increases.

  As a technology to reduce copper loss in transformers, in high-frequency transformers in which primary and secondary windings using copper foil are alternately arranged, primary and secondary windings in which the directions of current flow are opposite to each other Are alternately arranged, current concentration due to the proximity effect is suppressed and AC resistance is reduced.

By the way, as the operating voltage of the IC is reduced and the current is increased, the switching power supply is required to reduce the output voltage and increase the current. Therefore, in the transformer used for the switching power supply, the number of turns of the secondary winding is reduced and the number of turns is often increased. In addition, the demand for a thin power supply increases, the transformer needs to be thin, and the conductor forming the coil may have a flat plate shape for the purpose of suppressing an increase in AC resistance due to the skin effect. The secondary winding of this coil has a flat plate shape, and the shape of the lead wire of the transformer, which is one turn, is formed by narrowing the distance between the pair of electrodes as much as possible to ensure insulation. Also, in the case where a flat conductor is divided into a plurality of layers and connected in parallel, the conductor shape of each layer is made equal, and the position of the dividing groove between the electrodes of each layer is the same as the projected position in the thickness direction of each layer. It was formed in the same place.
JP 2003-272929 A

  In the case of forming the conductor of the secondary winding in the case of the above prior art, in one turn, the lead lines of both poles are formed on the same plane as the coil, so that the opposing areas of the lead lines are increased. There is a problem that cannot be made. Also, as the current flowing through the transformer increases, the copper loss, which is a loss due to the winding, is increased. Furthermore, the AC resistance of the conductor constituting the transformer coil increases as the frequency increases due to the skin effect and proximity effect. And the switching frequency in the switching power supply becomes high frequency, or the current waveform flowing in the circuit including the transformer increases the AC copper loss of the transformer due to the influence of harmonics due to the shape close to a trapezoidal wave or rectangular wave It is.

  Furthermore, as described above, when the number of turns of the secondary winding is reduced, not only the winding portion of the secondary winding but also the structure of the lead-out portion for connecting the secondary winding to a circuit outside the transformer is changed. The effect on the overall characteristics will increase. For example, as in the transformer 2 shown in FIG. 10, the interval between the fitting division grooves 12 is reduced to the minimum that can ensure insulation in each layer. Although it can be reduced, the facing area is small and has a limit. Further, the loss due to the AC resistance caused by the proximity effect and the skin effect is so large that it cannot be ignored in the recent high frequency and high current. Further, in this transformer 2, the shape of the secondary conductor 8 of each layer is made equal, and the position of the dividing groove 12 between the two poles is also formed to be equal to the projection direction in the secondary conductor 8. The density increases, the loss increases, and the transmission efficiency of the transformer 2 decreases. Furthermore, there is a problem that the inductance increases, the concentration of magnetic flux increases, the leakage magnetic flux increases, and it becomes a noise source for the surrounding circuits.

  The present invention has been made in view of the above-mentioned problems of the prior art, and an object thereof is to provide a planar transformer and a multilayer substrate that are small and thin and can reduce internal power loss and noise.

The present invention provides a transformer having a primary winding and a secondary winding formed of a planar conductor, the transformer having a core inserted in the center of the primary winding and the secondary winding, the secondary winding constitutes a one-turn coil which is extended long pair of lead portions in one direction, laminate the secondary winding is a plurality of layers connected in parallel via an insulating layer is formed, respectively wherein the pair of lead-out portion at the end of each pair of lead portions of the plurality of layers are connected respectively to the stacking direction, the position of the dividing groove that divides the pair of lead-out portion of the secondary winding, connected in parallel the Projection positions in the thickness direction differ between the conductors of each lead portion, and one lead portion of one of the secondary windings provided in parallel is the lead portion of the other polarity of the other secondary winding facing each other the have a portion that overlaps in the thickness direction of the laminate, when an electric current is applied to the respective coils and the lead Longitudinal current flows along a current flowing through the respective lead-out portion of the portion overlapping in the thickness direction of the laminate is formed trans to flow in opposite directions.

  The secondary winding is formed of a copper plate or a printed circuit board conductor. Further, the primary winding and the secondary winding may be formed of a conductor of a multilayer substrate.

  The overlapping width of the one polarity lead portion and the other polarity lead portion is 3% or more and 50% or less of the conductor width of the lead portion.

The present invention is also a multilayer substrate used for constituting a switching power supply apparatus, and a transformer is provided in a part of the multilayer substrate, and the transformer is formed of a primary winding and a planar conductor. A one-turn coil having a secondary winding and a core inserted in the center of the primary and secondary windings , wherein the secondary winding has a pair of extended portions extending in one direction. The secondary winding is connected in parallel by a plurality of layers through the insulating layer by the multilayer substrate , and the pair of lead portions are respectively in the stacking direction at the ends of the pair of lead portions of the plurality of layers. is connected, while the position of the dividing groove that divides the pair of lead-out portion of the secondary winding of the multilayer substrate, different projection position in the thickness direction between the conductors of the respective lead portions connected in parallel and provided in parallel Of the secondary winding of one of the secondary windings Possess the other portion overlapping in the thickness direction of the multilayer substrate and the polarity of the lead portion of the winding, when a current flows to each coil, current flows along the longitudinal direction of the lead-out portion, of the laminate This is a multilayer substrate having a structure formed so that currents flowing through the lead portions in the overlapping portion in the thickness direction flow in opposite directions . Further, the plurality of secondary windings are connected to each other by through holes in which one polarity lead portions and the other polarity lead portions penetrate each other in the thickness direction, and an interval between the pair of through holes is , Equal to the diameter of the inner periphery of the coil.

  According to the transformer of the present invention and the multilayer substrate provided with this transformer, the AC resistance of the conductor through which a large current flows can be reduced to reduce the copper loss, and the heat generation of the transformer can also be suppressed. Furthermore, the internal power loss of the transformer can be reduced, and the power supply efficiency of the switching power supply device using this transformer can be improved. Further, by reducing the internal power loss, it is possible to reduce the heat-radiating parts and to reduce the space for heat dissipation, and it is possible to further reduce the size of the switching power supply device.

  Hereinafter, a first embodiment of a transformer and a multilayer substrate according to the present invention will be described with reference to FIGS. The transformer of this embodiment is used as a transformer of a switching power supply.

  The transformer 20 of this embodiment includes a laminated body 22 having a conductor pattern in which a coil is formed. As shown in FIG. 2, the laminated body 22 has a coil formed on its surface with a conductor such as a flat plate shape or copper foil. A plurality of substrates 24 are formed so as to overlap each other. The substrate 24 is provided on the surface with a conductor pattern of a primary side conductor 30 in which a primary winding is formed and a secondary side conductor 46 in which a secondary winding is formed. Then, the ferrite core 26 is fitted with the laminated body 22 so as to sandwich the primary side conductor 30 and the secondary side conductor 46 so as to constitute the transformer 20.

  As shown in FIGS. 1 and 2, the laminated body 22 in which the coil of the transformer 20 is viewed from the upper surface has two rectangular through holes 28 in the vicinity of one end portion of the substrate 24 constituting the laminated body 22. It is provided parallel to the edge of the longitudinal end. Further, the through hole 28 is connected to a primary side terminal portion 32 connected to the primary side conductor 30 on the surface of each substrate 24 forming the multilayer body 22. An L-shaped primary side terminal member 34 shown in FIG. 1A is inserted into the primary side terminal portion 32, and the primary side terminal portion 32 and the primary side inside the laminated body 22 through the through hole 28. The terminal member 34 is electrically connected.

  A circular through hole 36 is provided slightly above the center of the substrate 24 forming the laminate 22, and the longitudinal edges of the substrate 24 located on both sides of the through hole 36 are concentric with the through hole 36. The shape swells in a circle so as to coincide with the circumference of the circle. The middle leg of the ferrite core 26 is inserted into the through hole 36.

  As shown in FIGS. 2 (c) and 2 (d), the primary winding by the primary side conductor 30 is formed on the substrate 24 of the multilayer body 22 around the through hole 36. The primary conductor 30 is formed on each substrate 24 by two turns and connected in series by a through hole 52 in the vicinity of the through hole 36 to form a four-turn coil. 2C and 2D, one end of each primary conductor 30 is connected to the primary terminal 32, and is connected to the pair of primary terminal members 34 through the through holes 28. .

Moreover, as shown in FIGS. 2A and 2B, the secondary side conductor 46 formed on the surface of the substrate 24 is formed along the peripheral portion of the through hole 36 on the secondary side of the multilayer body 22. Each form a secondary winding of one turn. The substrate 24 that forms the multilayer body 22 includes a lead portion 38 that extends from the secondary conductor 46 on the opposite side of the edge on which the primary conductor 30 of the multilayer body 22 is provided. In the vicinity of the end portion of the lead-out portion 38, a rectangular through hole 40 has a dimension substantially equal to the diameter of the inner peripheral edge of the coil portion along the peripheral edge portion of the through hole 36 of the secondary conductor 46 in parallel with the short side direction. Two are provided with an interval of. The through hole 40 is formed so as to penetrate the secondary terminal portion 42 on the surface of the substrate 24 forming the laminated body 22, and the secondary terminal member 44 is fitted and connected thereto. The secondary side terminal portion 42 extends from a secondary side conductor 46 provided on the surface of the substrate 24 forming the multilayer body 22. In this embodiment, the secondary terminal member 44 inserted into the through hole 40 of the secondary terminal portion 42 has a T-shape as shown in FIGS. The secondary terminal member 44 and the two-layer secondary conductor 46 are electrically connected via the through hole 40.

  In this embodiment, a lead-out portion 38 is formed at both ends of the secondary-side conductor 46 that forms the secondary winding of one turn with a split groove 50 that is a slight gap on the surface of the substrate 24. Is the secondary terminal portion 42. As shown in the cross-sectional view of FIG. 1C, the secondary side conductor 46 is provided with two independent layers with an insulating layer interposed therebetween, and the transformer 20 includes a primary winding by the primary side conductor 30 and the secondary side conductor 46. The turn ratio between the wire and the secondary winding is 4: 1. The secondary winding has a two-layer structure shown in FIGS. 2A and 2B. As shown in FIGS. 2A and 2B, the secondary winding has a dividing groove 50 of the lead-out portion 38 of the substrate 24 of each layer. The position is shifted to the right from the center line of the lead-out portion 38 in FIG. 2A and shifted to the left in FIG. 2B so that the projection positions in the thickness direction of the substrate 24 do not overlap each other. Are provided at predetermined intervals. In addition, the layered body 22 may further increase the number of layers by the substrate 24. In that case, the layers in FIG. 2A and the layers in FIG.

Next, the operation of the transformer 20 will be described. When a current is passed through the transformer 20 of this embodiment, a current flows in each of the lead portions 38 of the secondary side conductor 46 through the stacked substrates 24 of the lead portions 38 divided by the dividing grooves 50. Then, within each of the pair of lead portions 38 of the stacked secondary side conductor 46, the lead portion 38 in different directions of current flow to one another, portions facing each other, each drawer of stacked secondary side conductor 46 is the width between the dividing groove 50 of the section 38, reverse current to each other over a wide range, so that the face in close proximity at each leading portion 38 with each other are laminated. For this reason , the operation | movement which cancels out the magnetic flux which each drawer | drawing-out part 38 of each polarity cancels mutually is performed, and the influence of a proximity effect is reduced effectively.

  According to the transformer 20 of this embodiment, the influence of the proximity effect can be reduced and the AC resistance value can be reduced. Further, since the magnetic flux density of the lead-out portion 38 is reduced and the leakage magnetic flux is reduced, the generation of noise can be suppressed with low loss. Therefore, in the switching power supply device using this transformer 20, the internal power loss is reduced, the efficiency is improved and the heat generation can be suppressed, so the number of parts of the heat sink of the switching power supply is reduced, and the size is increased with higher efficiency. Is also possible.

  Next, a second embodiment of the present invention will be described with reference to FIG. Here, the same members as those in the above embodiment are denoted by the same reference numerals, and the description thereof is omitted. In the transformer of this embodiment, as shown in FIG. 3, the secondary conductor 46 has three layers.

  FIGS. 3A to 3C show the secondary conductor 46 formed of copper foil on the surface of each of the three layers of the substrate 24 forming the multilayer body 22. FIG. 3A shows a secondary winding of one turn formed by the secondary conductor 46, and at the lead-out portion 38 of the secondary conductor 46 on the right side in the drawing with respect to the longitudinal center line of the substrate 24. Dividing grooves 50 are provided at shifted positions, and both ends of the secondary winding are connected to the respective secondary side terminal portions 42. In FIG. 3B as well, a secondary winding of one turn is formed by the secondary conductor 46, and the lead-out portion 38 of the secondary conductor 46 is on the left side in the drawing with respect to the longitudinal center line of the substrate 24. Dividing grooves 50 are provided at shifted positions, and both ends of the secondary winding are connected to the respective secondary side terminal portions 42. In FIG. 3C, a secondary winding of one turn is formed by the secondary conductor 46, and the dividing groove 50 is provided along the longitudinal center line of the substrate 24 in the lead-out portion 38 of the secondary conductor 46. Thus, both ends of the secondary winding are connected to each secondary terminal portion 42. A stack 22 is formed by stacking a plurality of the substrates 24 with an insulating layer interposed therebetween. As shown in FIG. 3D, the cross section of the lead-out portion 38 of each substrate 24 of the laminate 22 is provided at a position where the position of the dividing groove 50 in the surface direction of the substrate 24 is different. That is, the lead portions 38 of the secondary conductors 46 connected in parallel in the thickness direction have overlapping projection positions in the thickness direction of the dividing grooves 50 formed in the respective substrates 24 between the adjacent secondary conductors 46. It does not have and is formed in a different position.

  According to the transformer 20 of this embodiment, even when the substrate 24 is stacked on three or more layers, the same effect as that of the above embodiment can be obtained. The dividing grooves 50 of each substrate 24 do not need to be symmetrical with respect to the center line, and the positions of the dividing grooves 50 are such that conductors having different polarities overlap each other between the substrates 24 facing each other in the lead-out portion 38. Any structure may be used as long as it is shifted in the plane direction.

  Next, a third embodiment of the present invention will be described with reference to FIGS. Here, the same members as those in the above embodiment are denoted by the same reference numerals, and the description thereof is omitted. As shown in FIG. 4, the transformer 20 of this embodiment includes a circuit board 58 having a circuit pattern made of a copper foil conductor on the surface, and a multilayer board formed by stacking insulating layers in the thickness direction. The laminated body 56 is formed by combining the ferrite core 26.

  A primary side conductor 30 and a secondary side conductor 46 constituting a coil are formed on the surface of the circuit board 58 forming the multilayer body 56. The lead-out portion 38 of the secondary-side conductor 46 is divided by the dividing groove 50 and connected to the secondary-side terminal portion 42, and each of the two rectifying elements 52 is connected to the secondary-side terminal portion of each layer through the through hole 54. 42. The secondary side conductors 46 of each layer of the multilayer body 56 constitute a coil provided in parallel, and the overlapping secondary side conductors 46 are connected to the circuit in parallel through the through holes 54. Also in this embodiment, in the lead-out portion 38 of the secondary-side conductor 46 of the plurality of layers of the transformer 20, the dividing grooves 50 of the respective layers of the secondary-side conductor 46 adjacent in parallel in the thickness direction are provided at positions where they do not overlap each other. It has been. The primary conductor 30 of the transformer 20 is connected by a through hole 60 in the thickness direction.

  The circuit formed on the circuit board 58 is, for example, a single forward power supply device shown in FIG. 5A or a half-bridge current rectification power supply device shown in FIG. The circuit shown in FIG. 5A includes an input capacitor C1 provided between input terminals and a switch element SW1 connected in series to a primary conductor 30 that is a primary winding of the transformer 20. On the secondary side, diodes D1 and D2 which are rectifying elements connected to the secondary conductor 46 are provided, and the terminal on the cathode side of the diode D2 and having the dots of the secondary conductor 46 is the choke coil L1. The output capacitor C2 is connected between the other end of the choke coil L1 and the anode of the diode D2, and is connected to the output terminal.

  Further, in the half-bridge double current rectification type power supply device shown in FIG. 5B, on the primary side, an input capacitor C3 provided between input terminals and capacitors C4 and C5 connected to both ends of the input capacitor C3 are provided. A series circuit and switch elements SW2 and SW3 provided in series connected to both ends of the series circuit of capacitors C4 and C5 are provided. The side with dots of the primary conductor 30 which is the primary winding of the transformer 20 is connected to the middle point of the capacitors C4 and C5, and the side without dots is connected to the middle points of the switch elements SW2 and SW3. On the secondary side, both ends of the secondary conductor 46 are connected to the cathodes of the diodes D3 and D4, which are rectifier elements, and to the respective ends of the choke coils L2 and L3. The other ends of the choke coils L2 and L3 are both connected to one end of the output capacitor C6, and the anodes of the diodes D3 and D4 are both connected to the other end of the output capacitor C6 and connected to the output terminal.

  The circuit board 58 formed of a multilayer board provided with the transformer 20 of this embodiment can be used for all power supply circuits as long as the number of windings of the secondary conductor 46 can be rectified.

  Next, a fourth embodiment of the present invention will be described with reference to FIG. Here, the same members as those in the above embodiment are denoted by the same reference numerals, and the description thereof is omitted. This embodiment is also provided with a coil composed of a laminate 22 formed of a plurality of substrates, and the substrate 24 is provided with a secondary side conductor 46 and a primary side conductor 30 with copper foil as shown in FIG. It has been. A split groove 50 is provided in the lead portion 38 of the secondary conductor 46 from the through hole 36 to the secondary terminal portion 42. This dividing groove 50 is provided with a refracted curved portion 60, and the position of the dividing groove 50 provided in the lead-out portion 38 of the secondary side conductor 46 is between the adjacent secondary side conductors 46 in the thickness direction. The dividing groove 50 is provided at a position where it does not overlap.

  In the transformer 20 of this embodiment, the same effect as that of the above embodiment can be obtained, and the shape, length, etc. of the dividing groove 50 are not questioned.

  The transformer and the multilayer substrate according to the present invention are not limited to the above-described embodiment, but are divided grooves formed in the lead-out portion of the secondary-side conductor, and secondary electrodes of other poles that are formed in parallel and stacked. The position where the dividing groove of the lead portion of the side conductor is projected in the thickness direction is different, and the overlap of the conductors of the other opposite poles of the lead portion may be 3 to 50% of the conductor width or conductor area.

  In addition, since the present invention only needs to be a transformer in which a coil is formed of a laminated body and a multilayer substrate including the transformer, the shape of the multilayer substrate and the core can be set as appropriate.

  Next, the results of the simulation of the transformer according to one embodiment of the present invention will be described with reference to FIGS. In the transformer 20 according to the first embodiment, as shown in FIG. 7A, the positions of the lead-out portion 38 and the dividing groove 50 of the secondary conductor 46 are shifted symmetrically from the longitudinal center line of the multilayer body 22. Is provided. The secondary side conductors 46 are provided in parallel in four layers with an insulating layer interposed therebetween in the thickness direction. Then, as shown in FIG. 7B, the positions of the first and third layer dividing grooves 50 and the positions of the second and fourth layer dividing grooves 50 are set equal in the horizontal direction on the drawing. is doing.

  For the transformer 20 of this example, the resistance value of the conductor of the lead portion 38 was verified by simulation. In the verification, for each of the secondary conductors 46 and the split grooves 50 of the four layers, the horizontal overlap width w, the thickness of the secondary conductor 46 t, and the horizontal width of the conductor of the lead portion 38 are L. In the calculation by simulation, the overlap width w is changed, the conductor thickness t = 0.105 mm, the division groove width S = 0.2 mm, and the horizontal width L = 11.8 mm of the lead portion 38. Asked.

  The graph of FIG. 8 shows the change of the AC resistance value of Example 1. In this graph, when there is no overlap, the AC resistance value when the current frequency is 600 kHz and 6 MHz is 10 to 40 times the DC resistance value due to the skin effect and the proximity effect. Further, since the dividing groove width S = 0.2 mm, the overlapping width = −0.2 mm when there is no overlap.

  From this graph, the overlap width w = about 5.8 mm and the minimum resistance value is taken. This corresponds to about 50% of the entire horizontal width of the drawer portion of the first embodiment. If the overlap width w is 50% or more, the lead portion of one electrode is too thin and the resistance value of that portion increases, so that the resistance value starts to increase as shown in the graph. Accordingly, it was confirmed that the effect was exhibited when the overlap width w was 50% or less.

  Moreover, the effect of reducing about 20% at 600 kHz and about 30% at 6 MHz was confirmed by simply setting the overlap width w to about 0.3 mm, compared to the conventional AC resistance value without overlap.

  From the above, it has been confirmed that the overlap width w exhibits an effect when it is 3% or more and 50% or less of the horizontal width L of the lead-out portion. In particular, it is preferable to form an overlap in the range of 3% to 25% in terms of conductor pattern design.

  In addition, due to the structure of this example, as shown in the graph of FIG. From the graph of FIG. 9, it can be confirmed that the overlap width w = about 5.8 mm and the minimum value is taken. As in the case of FIG. 8, this corresponds to about 50% of the full width in the horizontal direction of the drawer portion of the first embodiment. Moreover, only by forming the overlap width w as small as 0.3 mm, a significant reduction effect was confirmed as compared with the case where there was no overlap. This indicates that the concentration of the magnetic flux density is small and the leakage magnetic flux is small due to the overlap of the drawn portions. This also reduces noise generated due to leakage magnetic flux.

It is the left view (a), partial fracture top view (b), and AA sectional view (c) showing the transformer of a first embodiment of this invention. It is a top view which shows each board | substrate which forms the laminated body of this embodiment. It is a top view (a) (b) (c) which shows each board | substrate of the laminated body of 2nd embodiment of this invention, and sectional drawing of the drawer | drawing-out part of a laminated body. It is a schematic plan view which shows the multilayer substrate which provided the rectifier in the extraction | drawer part of the secondary side conductor of 3rd embodiment of this invention. It is a circuit diagram of the circuit (a) of the single forward type power supply provided in the multilayer substrate of this embodiment, and the circuit (b) which shows a half bridge double current rectification type power supply. It is a top view which shows the shape of the extraction | drawer part of the secondary side conductor of the board | substrate of 4th embodiment of this invention. It is the schematic plan view (a) and sectional drawing (b) which show the structure of the laminated body of Example 1 of this invention. It is a graph which shows the change of the alternating current resistance ratio of Example 1 of this invention. It is a graph which shows the change of the inductance ratio of Example 1 of this invention. It is the left view (a), partial broken top view (b), and BB sectional drawing (c) which show the trans | transformer by the conventional multilayer substrate.

Explanation of symbols

20 Transformer 22 Laminate 24 Substrate 26 Ferrite Core 30 Primary Side Conductor 38 Leader 42 Secondary Side Terminal 46 Secondary Side Conductor 50 Dividing Groove

Claims (7)

A transformer having a primary winding and a secondary winding formed of a planar conductor, wherein the transformer has a core inserted in the center of the primary winding and the secondary winding, and the secondary winding Constitutes a one-turn coil in which a pair of lead portions are extended in one direction, and the secondary winding is connected in parallel through a plurality of layers through an insulating layer to form a laminate . The pair of lead portions are respectively connected in the stacking direction at the ends of the pair of lead portions, and the positions of the dividing grooves that divide the pair of lead portions of the secondary winding are parallel to each other of the lead portions. Projection positions in the thickness direction differ between conductors, and one polarity lead portion of one of the secondary windings provided in parallel has the other polarity lead portion of the other secondary winding facing the other and the laminate. have a portion overlapping the thickness direction, when an electric current is applied to the respective coils, the longitudinal direction of the lead-out portion Along current flows, transformer current flowing through the respective lead-out portion of the portion overlapping in the thickness direction of the laminate, characterized in that it is formed so as to flow in opposite directions.   The transformer according to claim 1, wherein the secondary winding is formed of a copper plate.   2. The transformer according to claim 1, wherein the secondary winding is formed of a conductor of a printed circuit board.   2. The transformer according to claim 1, wherein the primary winding and the secondary winding are formed of a conductor of a multilayer substrate.   5. The overlap width between the one polarity lead portion and the other polarity lead portion is 3% or more and 50% or less of the width of the conductor of the lead portion. Transformer. In the multilayer substrate used to configure the switching power supply device, said comprising a transformer in a part of the multilayer substrate, the transformer includes a primary winding, a secondary winding formed by conductors planar shape, said primary A core inserted in the center of the winding and the secondary winding, and the secondary winding constitutes a one-turn coil in which a pair of leading portions extend long in one direction, and the secondary winding A plurality of windings are connected in parallel through the insulating layer by the multilayer substrate , and the pair of lead portions are connected in the stacking direction at the ends of the pair of lead portions of the plurality of layers , respectively . position of the dividing groove that divides the pair of lead-out portion of the secondary winding, different projection position in the thickness direction between the conductors of the respective lead portions connected in parallel, the one which is provided in parallel of said secondary winding The lead of one polarity is connected to the other pole of the other secondary winding Parts possess a lead portion overlapping portions in the thickness direction of the multilayer substrate, when an electric current is applied to each coil, current flows along the longitudinal direction of the lead-out portion, which overlaps in the thickness direction of the stack of A multilayer substrate characterized in that it has a structure formed such that currents flowing through the respective lead portions flow in opposite directions . The plurality of secondary windings are connected to each other by a through hole in which one polarity lead portions and the other polarity lead portions penetrate each other in the thickness direction, and the interval between the pair of through holes is The multilayer substrate according to claim 6, wherein the multilayer substrate has a diameter equal to that of the inner periphery of the coil.

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