Matrix transformer

Abstract

The invention provides a matrix transformer which can be configured to be small. The matrix transformer is used for a high-frequency switching power supply, and is characterized in that: two U-shaped ferrite cores each having two leg parts and one connecting part are used, and the abutting surfaces of the leg parts of the U-shaped ferrite cores face each other to form a core body, thereby forming a closed magnetic circuit; in order to configure m magnetic circuits of the transformer, m + 1 magnetic core bodies are provided, the magnetic core bodies are arranged in a one-dimensional manner so as to be adjacent to each other to configure an arrangement row of the magnetic core bodies constituting the magnetic circuits of the transformer, and a primary coil and a secondary coil wound around the leg part are provided.

Description

Technical Field

[0001] The invention relates to a transformer for a high frequency switching power supply. Background Art

[0002] As WBG (Wide Band Gap) semiconductor devices such as SiC and GaN that can perform high-speed switching continue to penetrate the market, research is being conducted on increasing the frequency of resonant converters such as LLC converters.

[0003] As the frequency increases, transformers, which are magnetic components, have the problem of increasing AC loss in the coil due to skin effect and proximity effect. The former can be solved to a certain extent by using twisted wires and printed coils, and the latter by using matrix transformers to disperse the magnetomotive force. However, there has been no progress in miniaturization.

[0004] Prior art literature

[0005] Patent Literature

[0006] [Patent Document 1] US2018-0226182

[0007] [Patent Document 2] US2019-0379292

[0008] [Patent Document 3] US2020-0350117 Summary of the invention

[0009] Problems to be solved by the invention

[0010] The matrix transformer described in Patent Document 1 (US2018-0026182) requires an external resonant inductor for the resonant circuit, which is not suitable for miniaturization of switching power supplies. This results in a large magnetic core with an integrated structure (the magnetic core is expensive and not resistant to vibration).

[0011] The matrix transformer described in Patent Document 2 (US2019-0379292) is a structure that integrates the resonant inductor that requires an external device with the matrix transformer, but it is not suitable for miniaturization of switching power supplies due to its large size. This results in a large magnetic core (expensive magnetic core; not resistant to vibration) that is constructed as an integrated structure.

[0012] The matrix transformer described in Patent Document 3 (US2020-0350117) increases the magnetic resistance by setting a magnetic gap in the magnetic circuit of the transformer, thereby forming a leakage flux and a leakage inductance. Therefore, by using the leakage inductance as a resonant inductor, there is no need to increase the resonant inductor. However, when the magnetic resistance is increased, the self-inductance of the primary and secondary coils also becomes lower, and as a result, the mutual inductance required to transmit magnetic energy also becomes lower. Because of the large-scale, it is not suitable for miniaturization of switching power supplies. This results in a large magnetic core (expensive magnetic core; not vibration-resistant) formed as an integrated structure.

[0013] The present invention is made to solve the problems of the prior art described above, and an object of the present invention is to provide a matrix transformer that can be configured in a small size.

[0014] Methods for solving problems

[0015] The matrix transformer of the present invention is used for a high-frequency switching power supply. The matrix transformer is characterized in that: a magnetic core body is formed by using two U-shaped ferrite cores each having two legs and one connecting portion, and the butt joint surfaces of the legs of each of the U-shaped ferrite cores are made to face each other to form a closed magnetic circuit. In order to form a magnetic circuit of m transformers, m+1 magnetic core bodies are provided.

[0016] The magnetic core bodies are arranged one-dimensionally in an adjacent manner to form an arrangement row of magnetic core bodies that constitutes the magnetic circuit of the transformer.

[0017] A primary coil and a secondary coil are wound around the leg.

[0018] In the matrix transformer of the present invention described above,

[0019] There are n rows of magnetic core bodies arranged,

[0020] By arranging the arrangement rows of the magnetic core bodies in two dimensions in an adjacent manner, a magnetic core matrix that becomes a magnetic circuit of a transformer can be constructed.

[0021] In the matrix transformer of the present invention described above, a magnetic path bypass may be provided between two U-shaped ferrite cores constituting all or part of the core body.

[0022] In the matrix transformer of the present invention described above, in each array row, the length of the connection portion of the U-shaped ferrite cores at both ends can be set to 50 to 70% of the length of the connection portion of the other U-shaped ferrite cores.

[0023] Effects of the Invention

[0024] According to the present invention, a matrix transformer that can be configured in a compact size can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a diagram showing the operating principle of one embodiment of the present invention.

[0026] Figure 2 This is a diagram showing wiring of coils according to one embodiment of the present invention.

[0027] Figure 3 This is a connection line diagram of a transformer according to one embodiment of the present invention.

[0028] Figure 4 It is a figure which shows the U-shaped ferrite core 1 which is one embodiment of this invention.

[0029] Figure 5 This is a diagram of a U-shaped ferrite core 2 according to one embodiment of the present invention.

[0030] Figure 6 It is a top view of one embodiment of the present invention.

[0031] Figure 7 It is a top view of another embodiment of the present invention.

[0032] Figure 8 It is a figure which shows the cross-sectional view of one embodiment of the present invention.

[0033] Fig. 9 This is a perspective view of one embodiment of the present invention.

[0034] Fig.10 It is a side view of one embodiment of the present invention.

[0035] Fig.11 This is a diagram of a strip-shaped ferrite core that serves as a magnetic circuit bypass according to the present invention.

[0036] Fig.12 This is a structural diagram of a printed coil of a transformer according to one embodiment of the present invention.

[0037] Fig.13 This is a connection line diagram of a transformer according to one embodiment of the present invention.

[0038] Fig.14 This is a diagram of a transformer according to one embodiment of the present invention.

[0039] Fig.15 This is a table showing design values ​​of electrical characteristics of a transformer according to one embodiment of the present invention.

[0040] Fig.16 This is a circuit diagram of a full-bridge LLC converter using one embodiment of the present invention.

[0041] Fig.17This is a configuration example on the circuit simulator LTSpice (manufactured by Analog Devices) of the LLC converter.

[0042] Fig.18 It is the operating specification of the LLC converter.

[0043] Fig.19 is a simulated waveform of the transformer when the LLC converter is operating.

[0044] Fig. 20 This is a table showing the losses obtained from the above waveforms.

[0045] Fig.21 This table compares the characteristics of a transformer according to one embodiment of the present invention and a transformer in a single ferrite core shape.

[0046] Fig. 22 This table compares the dimensions of a transformer according to one embodiment of the present invention and a transformer + resonance coil using a single ferrite core of ML29D when they are designed to have the same characteristics.

[0047] Fig.23 It is a figure which shows the cross-sectional view of one embodiment of the present invention.

[0048] Description of Reference Numerals

[0049] 11, 12…U-shaped ferrite core 1

[0050] 111, 121…The leg of the U-shaped ferrite core 1

[0051] 112, 122 ... window portion of U-shaped ferrite core 1

[0052] 113, 123 ... yoke portion of U-shaped ferrite core 1

[0053] 114, 124 ... butt joint surface of U-shaped ferrite core 1 21, 22 ... U-shaped ferrite core 2

[0054] 211, 221…legs of U-shaped ferrite core 2

[0055] 212, 222 ... window portion of U-shaped ferrite core 2

[0056] 213, 223 ... yoke portion of U-shaped ferrite core 2

[0057] 214, 222 ... butt joint surface of U-shaped ferrite core 2

[0058] 3…Primary coil

[0059] 311, 312…1st layer (surface) pad of primary side printed coil

[0060] 321, 322, 323, 324... Second layer coil pattern of the primary side printed coil 331, 332, 333, 334... Third layer coil pattern of the primary side printed coil 341, 342... Fourth layer (inner layer) pad of the primary side printed coil

[0061] 351, 352, 353, 354, 355…primary side printed coil interlayer via 4…secondary coil

[0062] 51…Strip ferrite core 1

[0063] 51b...Strip Ferrite Core

[0064] 52…Strip ferrite core 2

[0065] 52b...Strip Ferrite Core

[0066] 52c…Strip Ferrite Core

[0067] 6a ... Matrix transformer according to the first embodiment of the present invention

[0068] 6b, 6c ... Matrix transformer according to the second embodiment of the present invention

[0069] 6d ... Matrix transformer according to the third embodiment of the present invention

[0070] 6e ... Matrix transformer according to the fourth embodiment of the present invention

[0071] 61 ... Leakage inductor in the third embodiment of the present invention

[0072] 71…Input voltage

[0073] 721… Input filter capacitor 722, 723, 724, 725… MOSFET drain-source capacitance 728… Resonance capacitor

[0074] 727, 7287…Capacitors for output filters

[0075] 731, 732, 733, 734…MOSFET

[0076] 741, 742, 743, 744…rectifier diodes

[0077] 75…Inductor for output filter

[0078] 76…load. DETAILED DESCRIPTION

[0079] Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments at all, and can be implemented with appropriate changes within the scope of the purpose of the present invention.

[0080] (1) The matrix transformer of the present invention can have the following structure.

[0081] (a) Two U-shaped ferrite cores respectively make the butt joint surfaces of the legs (surfaces corresponding to the end surfaces of the legs of the U-shaped ferrite cores) face each other to form a core body, forming a single closed magnetic circuit. It is possible to form an arrangement row of m+1 core bodies in which m+1 core bodies are arranged in one dimension. m is a natural number, which is the number of parts that function as a transformer, and m+1 is the number of core bodies. Here, the wall thickness of the U-shaped ferrite core is preferably about 2.0 mm to 12 mm. From the perspective of mass producibility of ferrite, and from the perspectives of reducing eddy current losses of the core when used as a high-frequency transformer, uniformizing the magnetic flux density distribution, and reducing dimensional resonance, the wall thickness is preferably less than 12 mm, and further, it is preferably a wall thickness of 2.0 mm or more that can ignore the influence of the latter perspective. U-shape refers to, for example, a U-shape, a C-shape (a shape formed by preparing three plate-shaped ferrite plates and joining other ferrite plates at both ends of one ferrite plate in a manner perpendicular to it. The same shape can also be made by press-molding ferrite powder), etc.

[0082] (b) The primary and secondary coils of the transformer are mounted so as to be wound around the legs of the magnetic core.

[0083] (2) The matrix transformer of the present invention described above can have the following structure.

[0084] (a) n magnetic cores are arranged adjacent to each other, and the magnetic cores are arranged two-dimensionally to form a matrix of (m+1)×n magnetic cores, where n is a natural number.

[0085] (b) The primary and secondary coils of the transformer are mounted so as to be wound around the legs of the magnetic core.

[0086] (3) The matrix transformer of the present invention described above can have the following structure.

[0087] A magnetic circuit bypass is provided between the butting surfaces of the legs of the two U-shaped ferrite cores constituting the core body.

[0088] (4) The matrix transformer of the present invention described above can have the following structure.

[0089] In each arrangement, the length of the connection portion of the U-shaped ferrite cores at both ends is 50 to 70% of the length of the connection portion of the other U-shaped ferrite cores.

[0090] The matrix transformer of the present invention described above connects a plurality of arrays and uses them as a unit, and can cope with high-frequency switching. The connection between the U-shaped ferrite cores and the connection of the arrays can be combined using an adhesive, and can also be combined by supporting them using a winding frame. The adhesive will form a magnetic gap depending on the thickness, and from the viewpoint of reducing the use of the adhesive, it is preferable to use a winding frame.

[0091] By combining two types of U-shaped ferrite cores, a scalable transformer that can handle a variety of voltages and electric powers can be constructed. In addition, by making two U-shaped ferrite cores separately, a vibration-resistant structure can be constructed in a small size, so it can also be used in automotive applications.

[0092] The matrix transformer of the present invention can use the ferrites listed below as the U-shaped ferrite core and the magnetic circuit bypass.

[0093] An example of the ferrite used in the present invention is a MnZn-based ferrite sintered body, characterized in that it contains a main component and a subcomponent, wherein the main component is composed of 53.30 to 53.80 mol% of Fe when converted to Fe2O3, 6.90 to 9.50 mol% of Zn when converted to ZnO, and the remainder of Mn when converted to MnO, and the subcomponent is composed of 0.003 to 0.020 mass parts of Si when converted to SiO2, more than 0 mass parts and less than 0.35 mass parts of Ca when converted to CaCO3, 0.30 to 0.50 mass parts of Co when converted to CO3O4, 0.03 to 0.10 mass parts of Zr when converted to ZrO2, and 0 to 0.05 mass parts of Ta when converted to Ta2O5, for a total of 100 mass parts of the main component when converted,

[0094] The average crystal grain size is 3 μm or more and less than 8 μm,

[0095] The density of the sintered body is 4.65g / cm 3 above.

[0096] Here, the Ta content is preferably 0.01 parts by mass or more in terms of Ta2O5.

[0097] Here, preferably: the Fe content is 53.40-53.70 mol% when converted to Fe2O3, the Zn content is 7.00-9.40 mol% when converted to ZnO, the Si content is 0.004-0.015 mass parts when converted to SiO2, the Co content is 0.30-0.45 mass parts when converted to CO3O4, and the Zr content is 0.05-0.09 mass parts when converted to ZrO2.

[0098] Another example of the ferrite used in the present invention is a MnZn-based ferrite, characterized in that it contains Fe, Mn and Zn as main components, and contains at least Co, Si and Ca as auxiliary components, the main component is composed of 53 to 56 moles of Fe when converted to Fe2O3, 3 to 9 moles of Zn when converted to ZnO, and the remainder of Mn when converted to MnO, and the auxiliary components contain 100 mass% of the oxide of the main component when converted to CO3O4. 0.05-0.4 mass of Co, 0.003-0.015 mass of Si when converted to SiO2, 0.06-0.3 mass of Ca when converted to CaCO3, 0-0.1 mass of V when converted to V2O5, and 0-0.3 mass of Nb (Nb2O5 conversion) and / or Ta (Ta2O5 conversion) in total, the core loss Pcv is less than 2180kW / m at a frequency of 1MHz and an operating magnetic flux density of 75mT, between 0 and 140℃ 3 .

[0099] Another example of the ferrite used in the present invention is a MnZn-based ferrite used at a frequency of 1 MHz or more and an operating magnetic flux density of 75 mT or less, comprising as a main component 53 to 56 mol of Fe when converted to Fe2O3, 3 to 9 mol of Zn when converted to ZnO, and the remainder of Mn when converted to MnO, and as a secondary component 0.05 to 0.4 mol of Co when converted to CO3O4 relative to a total of 100 mol of the main component when converted to the oxide. , 0.003 to 0.015 parts by mass of Si as calculated as SiO2, 0.06 to 0.3 parts by mass of Ca as calculated as CaCO3, 0 to 0.1 parts by mass of V as calculated as V2O5, less than 0.05 parts by mass (excluding 0) of Nb as calculated as Nb2O5, and 0 to 0.1 parts by mass of Ta as calculated as Ta2O5, when formed into a magnetic core, the core loss Pcv is less than 1100kW / m at a frequency of 2MHz and an operating magnetic flux density of 50mT between 0 and 120°C 3 .

[0100] Here, preferably, the V content is 0 to 0.05 parts by mass when converted to V2O5, the Nb content is 0.01 to 0.04 parts by mass when converted to Nb2O5, and the Ta content is 0 to 0.05 parts by mass when converted to Ta2O5.

[0101] (First embodiment)

[0102] When a voltage V1 is applied to the primary coil of a transformer formed by connecting m transformers in series, the operating magnetic flux density B in the magnetic core generated by V1 is m It is expressed by the mathematical formula (1).

[0103]

[0104] Here, N represents the number of turns of the primary coil in the single transformer, A e 、f s They represent the effective cross-sectional area of ​​the core and the frequency of V1, respectively. It can be seen from this that the operating magnetic flux density (equivalent to the magnetic flux density in the core) can be reduced to 1 / m.

[0105] Furthermore, if the current flowing in the primary coil is I1 and R m is the magnetic resistance of the magnetic core of the single transformer, then the maximum value of the magnetomotive force generated in the single transformer is expressed by the mathematical formula (2), and the magnetomotive force can also be reduced to 1 / m.

[0106]

[0107] It can be seen that by increasing m, the relationship with B can be reduced. m The core loss increases accordingly, and the copper loss due to the proximity effect increases accordingly with the magnetomotive force.

[0108] In a first embodiment of the present invention, as a matrix transformer for a high-frequency switching power supply, Figure 1 It represents a cross-sectional view when m=4. In order to form the magnetic circuit of m transformers, there are m+1 magnetic core bodies, where m is the number of parts that function as transformers. Let m=4, and m+1=5. n is equivalent to 1 (n=1). The matrix transformer includes: 2 pairs of U-shaped ferrite cores 1 represented by 11 and 12, 3 pairs of U-shaped ferrite cores 2 represented by 21 and 22 arranged in a sandwiched manner, and the primary coil 3 and secondary coil 4 of the transformer. Here, ·, × indicate that the load currents of the coils flowing in the direction perpendicular to the paper are in opposite directions. In addition, the direction of the green arrow written in the core indicates the direction of the magnetic flux generated by the load current flowing in the primary and secondary coils. The primary load current flows in the primary coil in a manner that cancels the magnetic flux generated by the secondary current. Therefore, the magnetic flux inside the magnetic core generated by the load current is canceled. In addition, the dark extension represents the primary coil, and the light extension represents the secondary coil. Two U-shaped ferrite cores each having two legs (also called side legs) and one connecting portion (also called yoke portion) are used, and the mating surfaces of the legs are made to face each other to form a core body, thereby forming a closed magnetic circuit. The core bodies are arranged one-dimensionally in an adjacent manner to form an arrangement row of core bodies that become the magnetic circuit of the transformer. Figure 4 , Figure 5As shown, the length of the yoke portion of the U-shaped ferrite core 2 is twice the length of the yoke portion of the U-shaped ferrite core 1 at both ends, and the lengths of the legs are all the same. The length of the connecting portion of the U-shaped ferrite core at both ends can be 50-70% of the length of the connecting portion of the other U-shaped ferrite cores, and is 50% in the first embodiment. The coil is wound and wired in a manner to form 2 turns for each of the 4 pairs of opposite legs of the U-shaped ferrite core. Here, the so-called opposite means that the butt surfaces (end surfaces) of the legs (side legs) of the U-shaped ferrite core are aligned with each other. The core body is formed by being opposite to each other, forming a closed magnetic circuit. Figure 2 Here, in order to make the wiring of the coil easier to understand, the upper U-shaped ferrite cores 11 and 12 are omitted and only the lower U-shaped ferrite cores 12 and 22 are shown. The wiring reaching (1)-(2) represents the primary coil of the transformer, and the wiring reaching (3)-(4) represents the secondary coil of the transformer.

[0109] The matrix transformer constructed in this way is Figure 3 As shown, four independent transformers with two turns of primary and secondary windings are connected in series, and operate as a transformer with a transformation ratio of 1:1. In addition, like the existing matrix transformer, since the magnetomotive force is dispersed, the increase in AC resistance caused by the proximity effect during high-frequency operation can be reduced. Furthermore, since it is composed of a combination of multiple small and thin magnetic cores, a ferrite can be used that can flexibly respond to the voltage and electric power received, and has little loss even at high frequencies. That is, since it can perform high-frequency operation, the matrix transformer can be used for high-frequency switching power supplies. The matrix transformer can also be made small and low in height. In addition, the combination of small and thin magnetic cores can mass-produce magnetic cores at a low price. As a high frequency, it can be used for high frequencies above 200kHz, such as high frequencies above 500kHz, such as high frequencies above 1MHz.

[0110] In a matrix transformer of one embodiment of the present invention, three groups of U-shaped ferrite cores 2 (21, 22) are arranged between two groups of U-shaped ferrite cores 1 (11, 12) in such a manner that the legs (side legs) make the butt joint faces face each other to form a core body. Here, as the U-shaped ferrite core, ML95S, a high-frequency low-loss material of Proterial Corporation, is used. There are a primary coil and a secondary coil wound on the legs of the U-shaped ferrite core. Specifically, the primary coil and the secondary coil are formed of two turns (equivalent to a structure wound in two turns) using a pattern of the inner two layers of a four-layer substrate (FR4 used as a substrate for a printed circuit board). The copper foil thickness is 50 μm, which can obtain an optimal resistance value based on the trade-off relationship between DC resistance and AC resistance. Since the outermost layer has no patterns other than the terminal parts (1), (2), (3), and (4), it is used as an insulating layer between coils and between coils and cores.

[0111] In this embodiment, the coil uses a printed circuit board-based coil, but a twisted wire with a bare wire diameter of 50 to 100 μm and a bare wire count of about 1000 to 2500 may also be used. The number m of U-shaped ferrite cores 2 may be increased or decreased according to input voltage and power.

[0112] (Second embodiment)

[0113] In the magnetic circuit of a transformer formed by connecting m in series, if n magnetic cores of a single transformer are arranged side by side with their windows facing each other, the effective cross-sectional area of ​​the magnetic core of the single transformer can be increased to n times. The window is equivalent to the hole of the magnetic core body. When the windows are connected to each other, the coil can pass through. At this time, the operating magnetic flux density is expressed by the mathematical formula of formula (3).

[0114]

[0115] It is known that the magnetic flux density can be reduced to 1 / mn. In addition, regarding the magnetomotive force, the effective cross-sectional area of ​​the magnetic core of the single transformer is increased by n times, and its magnetic resistance is reduced to 1 / n. It can be reduced to 1 / mn as shown by the mathematical formula (4).

[0116]

[0117] Thereby, compared with the first embodiment, the core loss depending on the magnetic flux density and the copper loss due to the proximity effect depending on the magnetomotive force can be further reduced.

[0118] In a second embodiment of the present invention, the structure of the first embodiment is used as a matrix transformer for a high-frequency switching power supply. Figure 6 The top view shows the case where m=4 and n=4. A core matrix is ​​formed by arranging n rows of magnetic core bodies in two dimensions in such a way that the rows of magnetic core bodies are adjacent to each other, thereby forming a magnetic core matrix that becomes a magnetic circuit of a transformer. The magnetic circuit of the transformer is m=4, and the magnetic core bodies are m+1=5, so the magnetic circuit of the transformer is 16, and the magnetic core bodies are 20. In the first embodiment, the present matrix transformer adds 3 rows of U-shaped ferrite cores arranged in the same manner as the first embodiment in such a way that the windows of the U-shaped ferrite cores are opposite to each other, thereby forming a matrix of U-shaped ferrite cores with a total of 4 rows. The matrix transformer is capable of high-frequency operation, and the matrix transformer can be used for high-frequency switching power supplies.

[0119] In this embodiment, a ferrite core and a printed coil (equivalent to a primary coil and a secondary coil) made of the same material as in the first embodiment are used. However, when a magnetic core body is formed to form a closed magnetic circuit, the cross-sectional area of ​​the U-shaped ferrite core is increased by 4 times, so the inductance of the coil can be 4 times, the operating magnetic flux density can be reduced to 1 / 4, and high electric power can be handled.

[0120] Furthermore, the number m-1 of the core bodies of the U-shaped ferrite cores 2 (21, 22) and the number n of the rows of the U-shaped ferrite cores can be changed between the core bodies of the two pairs of U-shaped ferrite cores 1 (11, 12) according to the voltage and electric power to be handled. Figure 7 In another embodiment of the second embodiment, a matrix transformer having m×n=3×4 is shown.

[0121] (Third embodiment)

[0122] In the third embodiment of the present invention, Figure 8 The cross-sectional view of the matrix transformer used in the high-frequency switching power supply is shown. This embodiment utilizes the structure of the first embodiment and the structure of the second embodiment. Figure 1 , Figure 2 , Figure 3 , Figure 6 , Figure 8 In the matrix transformer of the embodiment shown, strip ferrite cores 51 and 52 are sandwiched between the butt joint surfaces 114, 124, 214, and 224 (the butt joint surfaces correspond to the end surfaces of the legs of the U-shaped ferrite cores) of each pair of U-shaped ferrite cores 1 and 2, and are provided as magnetic path bypasses. By providing a magnetic path bypass between the two U-shaped ferrite cores constituting the magnetic core body, a part of the magnetic flux generated by the load current of the primary coil and the secondary coil flows through the strip ferrite cores, and the coupling between the primary and the secondary is relaxed, so that leakage inductance can be obtained. This leakage inductance can be formed to a desired value by the gap length of the strip ferrite cores, and can be used as a resonant inductor of a high-frequency switching power supply. Here, considering the operating conditions of the LLC converter, the leakage inductance obtained by the magnetic path bypass is preferably set to about 1 / 12 to 1 / 4 of the mutual inductance obtained by the magnetic flux flowing in the magnetic core body. Furthermore, since the gaps are dispersed in a plurality of places, fringing magnetic flux generated in the gaps can be suppressed, and eddy current loss generated by linkage with the coil can be reduced.

[0123] Fig. 9 A perspective view showing an embodiment of an m×n=3×4 matrix transformer according to the third embodiment. Fig.10 The side view thereof is shown in FIG. U-shaped ferrite cores 1, 2 and Fig.11The strip ferrite core (equivalent to the magnetic circuit bypass) shown in FIG. 1 is made of the high-frequency low-loss material ML95 of Proterial Corporation, as in the first and second embodiments. The strip ferrite cores 51 and 52 have a portion of the gap dispersed in two locations to reduce the loss caused by the edge magnetic flux. In addition, the primary coil and the secondary coil are as shown in FIG. Fig.12 As shown, the patterns of the 2nd and 3rd layers of the 4-layer substrate (FR4 used as the base material of the printed circuit board) form 2 turns (equivalent to a structure of winding 2 turns). The copper foil thickness is 50μm, which can obtain the optimal resistance value based on the trade-off relationship between DC resistance and AC resistance. Since the outermost layer has no patterns other than the terminal parts (1), (2), (3), and (4), it is used as an insulating layer between coils and between coils and magnetic cores.

[0124] Fig.13 The connection line diagram of the matrix transformer obtained by this structure is shown. Leakage inductors 61 and 62 are added on the primary side and the secondary side respectively. Fig.14 , Fig.15 Indicates the design values ​​of its dimensions and electrical characteristics.

[0125] further, Fig.16 The circuit using the matrix transformer as a transformer of an LLC converter as a full-bridge resonant converter is shown. The DC input voltage 71 is converted into a rectangular AC by a full-bridge circuit composed of four MOSFETs 731, 732, 733, and 734, and further transmitted to the secondary side by a resonant circuit of a resonant capacitor 726 and a leakage inductor 61 of the third embodiment 6 of the present invention, so that the load current becomes a sine wave. On the secondary side, it is converted into a DC by a rectifier bridge composed of four diodes 741, 742, 743, and 744, and is smoothed by a smoothing circuit composed of capacitors 727, 728 and a coil 75, and DC power is supplied to the load.

[0126] Fig.17 Indicates the design specifications of this circuit. Fig.18 The circuit diagram input to LTSpice (manufactured by Analog Devices) as its loop simulator is shown. Further, Fig.19 The transformer action waveform obtained by this simulation is shown in Fig. 20 The calculated value of the transformer loss obtained from the waveform is shown.

[0127] As described above, it has been confirmed that the matrix transformer of the present invention can also operate correctly in an LLC converter for a high-frequency switching power supply.

[0128] (Comparison between the third embodiment and the prior art)

[0129] Fig.21The electric power and voltage that can be transmitted by a single transformer in the third embodiment and its main magnetic characteristics are shown. In equations (3) and (4), this embodiment is m×n=3×4, which can make the voltage mn=12 times that of a single transformer, and the electric power has (mn) 2 =144 times the capacity.

[0130] on the other hand, Fig. 22 The third embodiment is compared with the dimensions of a 100 kHz transformer + resonance coil using the ferrite core ML29D manufactured by Proterial Corporation. Fig. 22 The "bottom area" in Figure 6 , Figure 7 When viewed in the direction perpendicular to the paper, it is equivalent to the area occupied by the matrix transformer (occupied area). In the third embodiment, the area is 1.8 times larger, but the height is 0.4 times and the volume is 0.7 times. In particular, the thinness is excellent in terms of improving the heat dissipation of the transformer and the thinning requirements of the power supply. Furthermore, by integrating the resonant coil into the matrix transformer, it is possible to further reduce the price and miniaturize the high-frequency switching power supply.

[0131] (Fourth embodiment)

[0132] Fig.23 1 is a diagram showing a cross-sectional view of an embodiment of the present invention. In the matrix transformer 6e of this embodiment, strip ferrite cores 52b and 52c are sandwiched between the butt joints of each pair of U-shaped ferrite cores 21 and 22 (the butt joints are equivalent to the end faces of the legs of the U-shaped ferrite cores), and the primary coil 3 and the secondary coil 4 are wound around the U-shaped ferrite cores 11, 12, 21, and 22. The strip ferrite cores 52b and 52c are provided as magnetic circuit bypasses. However, the magnetic circuits at both ends of the U-shaped ferrite cores 11 and 12 are used, and there is no magnetic circuit bypass between the strip ferrite cores 51b and 52b.

[0133] Fig.23 The implementation method and Figure 8 The difference of the embodiment is that the magnetic circuit bypass is not provided in all of the m transformers, but in a part of them. This structure is suitable for shortening the magnetic gap length in the magnetic circuit bypass, and it is expected to reduce the edge flux. Fig.23 In the method, m=3, there is no magnetic circuit bypass at the two ends of the magnetic circuit, so the magnetic gap length of the two magnetic circuits in the center can be set smaller. In addition, the so-called edge flux is a phenomenon in which the cross-sectional area through which the magnetic flux passes is larger than the cross-sectional area of ​​the core because it plays a role in reducing magnetic resistance in the magnetic gap, and the magnetic flux expands. When the edge flux increases, it will lead to increased losses.

[0134] The matrix transformer of the present invention described above can convert electric power into magnetic force, and convert the magnetic force into electric power, and transmit energy between circuits via windings. The matrix transformer is different from a reactor. A reactor is a component that uses windings but blocks the flow of current when the voltage changes, but instead generates a magnetic field and temporarily stores energy, and is therefore different from the matrix transformer of the present invention.

Claims

1. A matrix transformer for a high-frequency switching power supply, wherein the matrix transformer is characterized in that: The core body is formed by using two U-shaped ferrite cores each having two legs and one connecting portion, and making the butting surfaces of the legs of each U-shaped ferrite core face each other to form a closed magnetic circuit. In order to form the magnetic circuits of m transformers, there are m+1 magnetic cores. The magnetic core bodies are arranged one-dimensionally in an adjacent manner to form an arrangement row of magnetic core bodies that constitutes the magnetic circuit of the transformer. The matrix transformer has a primary coil and a secondary coil wound around the leg.

2. The matrix transformer according to claim 1, characterized in that: There are n rows of magnetic core bodies arranged, The arrangement rows of the magnetic core bodies are arranged adjacent to each other to form a two-dimensional arrangement of the magnetic core bodies, thereby forming a magnetic core matrix that becomes a magnetic circuit of a transformer.

3. The matrix transformer according to claim 1 or 2, characterized in that: A magnetic circuit bypass is provided between two U-shaped ferrite cores constituting all or part of the core body.

4. The matrix transformer according to claim 1 or 2, characterized in that: In each arrangement row, the length of the connection portion of the U-shaped ferrite cores at both ends is 50 to 70% of the length of the connection portion of the other U-shaped ferrite cores.

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