Matrix transformer

Abstract

To provide a small, configurable matrix transformer.SOLUTION: A matrix transformer for use in a high frequency switching power supply uses two U-shaped ferrite cores each having two legs and one connecting portion, to form a core body by opposing the butt faces of the respective legs, which forms a closed magnetic circuit, m+1 core bodies are provided to form m magnetic circuits of the transformer, the core bodies are arranged one-dimensionally such that each core body is adjacent to another, to form a row of core bodies which make up the magnetic circuits of the transformer, and the matrix transformer has primary and secondary coils wound around the legs.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a transformer used in a high-frequency switching power supply. [Background technology]

[0002] As wide band gap (WBG) semiconductor devices capable of high-speed switching, such as SiC and GaN, penetrate the market, research is underway to increase the frequency of resonant converters, such as LLC converters.

[0003] Transformers, which are magnetic components, have the problem of increased AC loss in the coil due to the skin effect and proximity effect as frequencies increase. The former can be solved to some extent by using Litz wire or a printed coil, and the latter by dispersing the magnetomotive force using a matrix transformer. However, there has been no progress in miniaturizing them. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US2018-0226182 [Patent Document 2] US2019-0379292 [Patent Document 3] US2020-0350117 Summary of the Invention [Problem to be solved by the invention]

[0005] The matrix transformer described in Patent Document 1 (US2018-0026182) requires an external resonant inductor required for the resonant circuit, and is not suitable for miniaturizing switching power supplies. It results in a large, integrated core (which is expensive and vulnerable to vibration).

[0006] The matrix transformer described in Patent Document 2 (US2019-0379292) has a structure in which the resonant inductor, which must be externally attached, is integrated with the matrix transformer, but this makes the transformer large and is not suitable for miniaturizing switching power supplies. It also results in a large, integrated core (which is expensive and vulnerable to vibration).

[0007] The matrix transformer described in Patent Document 3 (US2020-0350117) creates leakage flux by increasing the magnetic resistance by providing a magnetic gap in the magnetic path of the transformer, thereby creating leakage inductance. Therefore, by using this leakage inductance as a resonant inductor, there is no need to add a resonant inductor. However, increasing the magnetic resistance also reduces the self-inductance of the primary and secondary coils, and as a result, the mutual inductance required for transferring magnetic energy also decreases. Since it becomes large, it is not suitable for miniaturizing switching power supplies. It becomes a large, integrated core (the core is expensive and vulnerable to vibration).

[0008] The present disclosure has been proposed to solve the problems of the conventional techniques as described above, and has an object to provide a compact, configurable matrix transformer. [Means for solving the problem]

[0009] The matrix transformer of the present invention is a matrix transformer used in a high-frequency switching power supply, A closed magnetic circuit is formed by using two U-shaped ferrite cores each having two legs and one connecting part, and by arranging the butt surfaces of the legs so as to face each other to form a core body, The transformer has m+1 core bodies to configure m magnetic circuits, The core bodies are arranged one-dimensionally so as to be adjacent to each other to form a row of core bodies which constitute a magnetic circuit of the transformer, It is characterized by having a primary coil and a secondary coil wound around the legs.

[0010] In the matrix transformer of the present invention, The core body has n rows, By arranging the core bodies two-dimensionally so that the rows are adjacent to each other, a core matrix that becomes the magnetic circuit of the transformer can be formed.

[0011] In the matrix transformer of the present invention described above, a magnetic path bypass can be provided between all or some of the two U-shaped ferrite cores that constitute the core body.

[0012] In the matrix transformer of the present invention described above, in each row, the length of the connecting portions of the U-shaped ferrite cores at both ends can be 50 to 70% of the length of the connecting portions of the other U-shaped ferrite cores. Effect of the Invention

[0013] According to the present invention, a compact and configurable matrix transformer can be obtained. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 illustrates the operating principle of one embodiment of the present disclosure. [Diagram 2] FIG. 2 is a diagram showing the wiring of a coil according to an embodiment of the present disclosure. [Diagram 3] FIG. 2 is a wiring diagram of a transformer according to an embodiment of the present disclosure. [Figure 4] FIG. 1 is a diagram of a U-shaped ferrite core 1 according to an embodiment of the present disclosure. [Diagram 5] FIG. 2 is a diagram of a U-shaped ferrite core 2 according to one embodiment of the present disclosure. [Figure 6] FIG. 1 illustrates a top view of an embodiment of the present disclosure. [Figure 7] FIG. 13 is a top view of another embodiment of the present disclosure. [Figure 8] FIG. 1 illustrates a cross-sectional view of one embodiment of the present disclosure. [Figure 9] FIG. 1 is a perspective view of an embodiment of the present disclosure. [Figure 10]FIG. 1 is a side view of one embodiment of the present disclosure. [Figure 11] 1 is a diagram of a bar-shaped ferrite core that serves as a magnetic path bypass according to the present disclosure. [Figure 12] FIG. 2 is a structural diagram of a printed coil of a transformer according to an embodiment of the present disclosure. [Figure 13] FIG. 2 is a wiring diagram of a transformer according to an embodiment of the present disclosure. [Figure 14] 1 is a diagram of a transformer according to one embodiment of the present disclosure. [Figure 15] 1 is a table showing design values ​​of electrical characteristics of a transformer according to an embodiment of the present disclosure. [Figure 16] FIG. 1 is a circuit diagram of a full-bridge LLC converter using an embodiment of the present disclosure. [Figure 17] This is an example of the configuration of the LLC converter on the circuit simulator LTSpice (manufactured by Analog Devices). [Figure 18] 4 shows the operating specifications of the LLC converter. [Figure 19] 4 is a simulation waveform of the transformer during operation of the LLC converter. [Figure 20] 11 is a table showing losses determined from the waveform. [Figure 21] 1 is a table comparing the characteristics of a transformer according to an embodiment of the present disclosure and a transformer having a single ferrite core shape. [Figure 22] 11 is a table comparing the dimensions of a transformer according to an embodiment of the present disclosure and a transformer + resonant coil using a single ferrite core made of ML29D when designed to have the same characteristics. [Figure 23] FIG. 1 illustrates a cross-sectional view of one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of the present disclosure will be described in detail. The present disclosure is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present disclosure.

[0016] (1) The matrix transformer of the present disclosure may have the following configuration. (a) Two U-shaped ferrite cores are formed by facing the butt surfaces of the legs (surfaces corresponding to the end surfaces of the legs of the U-shaped ferrite cores) to form a core body, forming a single closed magnetic circuit. The m+1 core bodies can be arranged in a one-dimensional manner to form a row of m+1 core bodies. m is a natural number and is the number of parts that function as a transformer, and m+1 is the number of core bodies. Here, the thickness of the U-shaped ferrite core is preferably about 2.0 mm to 12 mm. From the viewpoint of mass production of ferrite, and from the viewpoints of reducing eddy current loss of the core when used as a high-frequency transformer, uniformizing the magnetic flux density distribution, and reducing dimensional resonance, the thickness is preferably 12 mm or less, and furthermore, the thickness is preferably 2.0 mm or more, in which the influence of the latter viewpoint can be ignored. The U-shape refers to, for example, a U-shape or a C-shape (a shape in which three plate-shaped ferrite plates are prepared and the other ferrite plates are joined to both ends of one ferrite plate so that they are perpendicular to each other. The same shape can also be produced by pressure molding of ferrite powder). (b) The primary and secondary coils of the transformer are attached by winding them around the legs of the core body.

[0017] (2) The matrix transformer of the present disclosure described above may have the following configuration. (a) A matrix of (m+1)×n core bodies formed by arranging n core bodies adjacent to each other in a two-dimensional array, where n is a natural number. (b) The primary and secondary coils of the transformer are attached by winding them around the legs of the core body.

[0018] (3) The matrix transformer of the present disclosure described above may have the following configuration. A magnetic path bypass is provided between the butted faces of the legs of the two U-shaped ferrite cores that constitute the core body.

[0019] (4) The matrix transformer of the present disclosure described above may have the following configuration. In each arrangement, the length of the connecting portions of the U-shaped ferrite cores at both ends is 50 to 70% of the length of the connecting portions of the other U-shaped ferrite cores. The matrix transformer of the present disclosure is used as a unit by connecting multiple rows, and can handle high frequency switching. The U-shaped ferrite cores can be connected to each other or to rows via adhesive, or can be supported by a bobbin. Depending on the thickness, the adhesive can become a magnetic gap, so it is desirable to use a bobbin to reduce the use of adhesive. Combining two types of U-shaped ferrite cores makes it possible to create a scalable transformer that can handle a wide variety of voltages and powers. In addition, by creating two separate U-shaped ferrite cores, the transformer can be made smaller and more resistant to vibration, making it suitable for use in automotive applications.

[0020] The matrix transformer of the present disclosure can use the following ferrites for the U-shaped ferrite core and magnetic path bypass.

[0021] An example of a ferrite for use in this disclosure is, for example, Fe 2 O 3 A main component consisting of 53.30 to 53.80 mol % Fe calculated as ZnO, 6.90 to 9.50 mol % Zn calculated as ZnO, and the remainder Mn calculated as MnO; SiO relative to 100 parts by mass of the total of the main components in the above conversion 2 Converted to 0.003 to 0.020 parts by mass of Si, CaCO 3 Ca, Co converted to more than 0 parts by mass and 0.35 parts by mass or less 3 O 4 Converted to 0.30 to 0.50 parts by mass of Co and ZrO 2 Converted to 0.03 to 0.10 mass parts of Zr and Ta 2 O 5 and a subcomponent consisting of 0 to 0.05 parts by mass of Ta, The average crystal grain size is 3 μm or more and less than 8 μm, Sintered density is 4.65 g / cm 3The MnZn-based ferrite sintered body is characterized by the above. Here, the Ta content is Ta 2 O 5 It is preferable that the amount is 0.01 parts by mass or more in terms of conversion. Here, the Fe content is Fe 2 O 3 The Zn content is 53.40 to 53.70 mol% in terms of ZnO, the Zn content is 7.00 to 9.40 mol% in terms of ZnO, and the Si content is SiO 2 The Co content is 0.004 to 0.015 parts by mass in terms of Co. 3 O 4 The Zr content is 0.30 to 0.45 parts by mass in terms of ZrO 2 The amount is preferably 0.05 to 0.09 parts by mass in terms of conversion.

[0022] Another example of the ferrite used in the present disclosure is, for example, an MnZn-based ferrite containing Fe, Mn, and Zn as main components and at least Co, Si, and Ca as accessory components, The main component is Fe 2 O 3 53 to 56 mol % Fe calculated as ZnO, 3 to 9 mol % Zn calculated as ZnO, and the remainder Mn calculated as MnO, The auxiliary component is Co with respect to 100 mass % of the oxide of the main component. 3 O 4 Converted to 0.05 to 0.4 mass% Co, SiO 2 Converted to 0.003-0.015 mass% Si, CaCO 3 Converted to 0.06 to 0.3 mass% Ca, V 2 O 5 0 to 0.1 mass% V in total, and 0 to 0.3 mass% Nb (Nb 2 O 5 conversion) and / or Ta (Ta 2 O 5 Conversion) At a frequency of 1 MHz and an operating magnetic flux density of 75 mT, the core loss Pcv between 0 and 140°C is 2180 kW / m 3 The MnZn-based ferrite is characterized in that

[0023] Another example of ferrite used in the present disclosure is, for example, Fe 2 O 3 The main components are 53 to 56 mol % Fe calculated as ZnO, 3 to 9 mol % Zn calculated as ZnO, and the remainder Mn calculated as MnO, and the main components are 53 to 56 mol % Fe calculated as ZnO, 3 to 9 mol % Zn calculated as ZnO, and the remainder Mn calculated as MnO. 3 O 4 Converted to 0.05 to 0.4 parts by mass of Co, SiO 2 Converted to 0.003 to 0.015 parts by mass of Si, CaCO 3 Converted to 0.06 to 0.3 parts by mass of Ca and V 2 O 5 Converted to 0 to 0.1 mass parts of V and Nb 2 O 5 Converted to 0.05 parts by mass or less (excluding 0) of Nb and Ta 2 O 5 When the magnetic core contains 0 to 0.1 parts by mass of Ta as an auxiliary component, the magnetic core loss Pcv is 1100 kW / m at a frequency of 2 MHz and an operating magnetic flux density of 50 mT between 0 and 120°C. 3 It is a MnZn ferrite with a melting point of less than 100 nm. Here, the V content is V 2 O 5 The Nb content is 0 to 0.05 parts by mass in terms of Nb 2 O 5 and the Ta content is 0.01 to 0.04 parts by mass in terms of Ta 2 O 5 The amount is preferably 0 to 0.05 parts by mass in terms of the total amount.

[0024] (First embodiment) The primary coil of a transformer consisting of m transformers connected in series is connected to V 1 When a voltage of V is applied, 1 The operating magnetic flux density B in the core caused by m is given by the formula (1).

[0025]

number

[0026] Here, N is the number of turns in the primary coil of a single transformer, A e ,f s is the effective cross-sectional area of ​​the core, V 1 As a result, it is possible to reduce the operating magnetic flux density (corresponding to the magnetic flux density inside the core) to 1 / m.

[0027] Furthermore, the current flowing through the primary coil is I 1 Then, the maximum value of the magnetomotive force generated in a single transformer is R m If we consider is the magnetic resistance of the core of a single transformer, we get equation (2), and the magnetomotive force can also be reduced to 1 / m.

[0028]

number

[0029] FIG. 1 shows a cross-sectional view of a matrix transformer used in a high-frequency switching power supply in the first embodiment of the present disclosure, where m=4. In order to configure m magnetic circuits of the transformer (m is the number of parts that function as a transformer), there are m+1 core bodies. m=4, so m+1=5. n corresponds to 1 (n=1). The matrix transformer is composed of two pairs of U-shaped ferrite cores 1 consisting of 11 and 12, three pairs of U-shaped ferrite cores 2 consisting of 21 and 22 arranged between them, and further the primary coil 3 and secondary coil 4 of the transformer. Here, · and × indicate that the load currents of the coils flowing perpendicular to the paper surface are in the opposite directions. The direction of the green arrows written inside 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 so as to cancel out the magnetic flux generated by the secondary current. Therefore, the magnetic flux inside the core caused by the load current is canceled out. The dark colors indicate the primary coil, and the light colors indicate the secondary coil. A core body is formed by using two U-shaped ferrite cores each having two legs (also called side legs) and one connecting part (also called yoke part) and by facing the butt faces of the legs to each other, forming a closed magnetic circuit. The core bodies are arranged one-dimensionally so that they are adjacent to each other, forming a row of core bodies that become the magnetic circuit of the transformer. As shown in FIG. 4 and FIG. 5, the length of the yoke part of the U-shaped ferrite core 2 is twice as long as that 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 parts of the U-shaped ferrite cores at both ends may be 50 to 70% of the length of the connecting parts of the other U-shaped ferrite cores, and in the first embodiment, it is 50%. The coil is wired by winding two turns around each of the four pairs of opposing legs of the U-shaped ferrite core. Here, facing refers to butting the butt faces (end faces) of the legs (side legs) of the U-shaped ferrite cores against each other. By facing each other, a core body is constructed, forming a closed magnetic circuit. Figure 2 shows the wiring state. In this figure, the upper U-shaped ferrite cores 11 and 12 are omitted, leaving only the lower U-shaped ferrite cores 12 and 22, so that the coil wiring can be clearly seen.The wiring from (1) to (2) represents the primary coil of the transformer, and the wiring from (3) to (4) represents the secondary coil of the transformer.

[0030] The matrix transformer configured in this way operates as a transformer with a transformation ratio of 1:1, as shown in Figure 3, by connecting four independent transformers in series, each with two turns of primary and secondary windings. As with conventional matrix transformers, the magnetomotive force is distributed, so that the increase in AC resistance due to the proximity effect during high-frequency operation can be reduced. Furthermore, since it is configured with a combination of multiple small and thin cores, it can flexibly respond to the voltage and power being handled, and ferrite, which has low loss even at high frequencies, can be used. In other words, since high-frequency operation is possible, this matrix transformer can be used for high-frequency switching power supplies. The matrix transformer can also be made small and low-profile. In addition, since it is a combination of small and thin cores, it is possible to mass-produce the cores at a low price. As for high frequencies, it can be used for high frequencies of, for example, 200 kHz or more, for example, 500 kHz or more, and for example, 1 MHz or more.

[0031] In the matrix transformer according to an embodiment of the present disclosure, three sets of U-shaped ferrite cores 2 (21, 22) are arranged between two sets of U-shaped ferrite cores 1 (11, 12) so that the legs (side legs) face each other at the butt surface to form a core body. Here, the high-frequency low-loss material ML95S from Proterial Co., Ltd. is used as the U-shaped ferrite core. The primary coil and secondary coil are wound around the legs of the U-shaped ferrite core. Specifically, the primary coil and secondary coil are configured with two turns (corresponding to a configuration in which the coils are wound twice) using an interpolated two-layer pattern of a four-layer board using FR4, which is a material for printed circuit boards. The thickness of the copper foil is 50 μm, which is an optimum resistance value obtained from the trade-off relationship between DC resistance and AC resistance. The most extrapolated pattern is used as an insulating layer between the coils and between the coil and the core, since there is no pattern other than the terminal parts (1), (2), (3), and (4).

[0032] In this embodiment, the coil is a printed coil made of a printed circuit board, but a Litz wire having a wire diameter of 50 to 100 μm and a wire count of about 1,000 to 2,500 may also be used. The number m of the U-shaped ferrite cores 2 may be increased or decreased depending on the input voltage and power.

[0033] Second Embodiment In a magnetic circuit of a transformer consisting of m cores connected in series, if n cores of individual transformers are arranged so that their windows face each other, the effective cross-sectional area of ​​the individual transformer cores can be increased by n times. The windows correspond to the holes in the core body. If the windows are connected to each other, a coil can be passed through. In this case, the operating magnetic flux density is expressed by equation (3).

[0034]

number

[0035] It can be seen that the magnetic flux density can be reduced to 1 / mn. In addition, the effective cross-sectional area of ​​the core of the single transformer becomes n times larger, and the magnetic resistance is reduced to 1 / n, so the magnetomotive force can be reduced to 1 / mn as shown in equation (4).

[0036]

number

[0037] This makes it possible to further reduce the core loss, which depends on the magnetic flux density, and the copper loss due to the proximity effect, which depends on the magnetomotive force, compared to the first embodiment.

[0038] In the second embodiment of the present disclosure, the configuration of the first embodiment is used as a matrix transformer used in a high-frequency switching power supply, and a top view in the case of m=4, n=4 is shown in FIG. 6. The matrix transformer has n rows of core bodies, and the rows of the core bodies are arranged two-dimensionally so that they are adjacent to each other to form a core matrix that becomes a magnetic circuit of the transformer. Since the number of magnetic circuits of the transformer is m=4 and the number of core bodies is m+1=5, the number of magnetic circuits of the transformer is 16 and the number of core bodies is 20. In this matrix transformer, three rows of the same arrangement as the U-shaped ferrite cores of the first embodiment are added so that the windows of the U-shaped ferrite cores face each other in the first embodiment to form a matrix of U-shaped ferrite cores with a total of four rows. High-frequency operation is possible, and this matrix transformer can be used in a high-frequency switching power supply.

[0039] In this embodiment, a ferrite core and a printed coil (corresponding to a primary coil and a secondary coil) made of the same material as those used in the first embodiment are used. However, when forming the core body and forming a closed magnetic circuit, the cross-sectional area of ​​the U-shaped ferrite core is increased four times, so the inductance of the coil can be increased fourfold and the operating magnetic flux density can be reduced to one-quarter, making it possible to handle large power.

[0040] Furthermore, the number m-1 of U-shaped ferrite cores 2 (21, 22) between the two pairs of U-shaped ferrite cores 1 (11, 12) and the number n of rows of the U-shaped ferrite cores can be changed depending on the voltage and power to be handled. Fig. 7 shows another embodiment of the second embodiment, in which an m x n = 3 x 4 matrix transformer is configured.

[0041] (Third embodiment) FIG. 8 shows a cross-sectional view of a matrix transformer used in a high-frequency switching power supply in the third embodiment of the present disclosure. This embodiment utilizes the configurations of the first embodiment and the second embodiment. In this embodiment, in the matrix transformer of the embodiment shown in FIGS. 1, 2, 3, 6, and 8, bar-shaped ferrite cores 51 and 52 are sandwiched between butt surfaces 114, 124, 214, and 224 (the butt 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 a magnetic path bypass. By providing a magnetic path bypass between the two U-shaped ferrite cores that constitute the core body, a part of the magnetic flux generated by the load current of the primary coil and the secondary coil flows bypassing the bar-shaped ferrite core, and the coupling between the primary and secondary coils is relaxed, and a leakage inductance is obtained. This leakage inductance can be set to a desired value by adjusting the gap length of the bar-shaped ferrite core, and can be used as a resonant inductor of a high-frequency switching power supply. Considering the operating conditions of an LLC converter, it is desirable to set the leakage inductance obtained by the magnetic path bypass to about 1 / 12 to 1 / 4 of the mutual inductance obtained by the magnetic flux flowing in the core body. In addition, this gap can be distributed to multiple locations to suppress the fringing of magnetic flux generated in the gap, and it is also possible to reduce eddy current loss generated by linkage to the coil.

[0042] FIG. 9 shows a perspective view of an embodiment of the matrix transformer of m×n=3×4 of the third embodiment. FIG. 10 shows its side view. The U-shaped ferrite cores 1 and 2 and the bar-shaped ferrite cores (corresponding to the magnetic path bypass) shown in FIG. 11 use the high-frequency low-loss material ML95 from Proterial Co., Ltd., as in the first and second embodiments. The bar-shaped ferrite cores 51 and 52 are designed to reduce losses due to fringing by distributing some gaps in two places. The primary coil and the secondary coil are configured with two turns (corresponding to a configuration in which the coils are wound twice) using the patterns of the second and third layers of a four-layer board using FR4, which is a material for printed circuit boards, as shown in FIG. 12. The thickness of the copper foil is set to 50 μm, which is an optimum resistance value obtained from the trade-off relationship between DC resistance and AC resistance. The extrapolation is used as an insulating layer between the coils and between the coil and the core, since there are no patterns other than the terminal parts (1), (2), (3), and (4).

[0043] Fig. 13 shows the wiring diagram of the matrix transformer obtained by this configuration. Leakage inductors 61 and 62 are added to the primary and secondary sides, respectively. Furthermore, the design values ​​of the external dimensions and electrical characteristics are shown in Fig. 14 and Fig. 15.

[0044] 16 shows a circuit in which this matrix transformer is used as a transformer for an LLC converter, which is a full-bridge resonant converter. DC input voltage 71 is converted into rectangular AC by a full-bridge circuit consisting of four MOSFETs 731, 732, 733, and 734, and the load current is converted into a sine wave by a resonant circuit consisting of a resonant capacitor 726 and a leakage inductance 61 of the third embodiment 6 of the present disclosure and transmitted to the secondary side. On the secondary side, the voltage is converted into DC by a rectifier bridge consisting of four diodes 741, 742, 743, and 744, and smoothed by a smoothing circuit consisting of capacitors 727 and 728 and a coil 75, and DC power is supplied to the load.

[0045] The design specifications for this circuit are shown in Fig. 17, the circuit diagram entered into the circuit simulator LTSpice (manufactured by Analog Devices) is shown in Fig. 18, the transformer operating waveforms obtained by this simulation are shown in Fig. 19, and the transformer loss calculation values ​​obtained from these waveforms are shown in Fig. 20.

[0046] From the above, it can be confirmed that the matrix transformer according to the present disclosure can also operate correctly in an LLC converter for a high-frequency switching power supply.

[0047] (Comparison between the third embodiment and the prior art) FIG. 21 shows the third embodiment, the transmittable power and voltage of a single transformer, and its main magnetic characteristics. In equations (3) and (4), this embodiment has m×n=3×4, so compared to a single transformer, the voltage is mn=12 times and the power is (mn) 2 =144 times the power.

[0048] Meanwhile, in FIG. 22, the dimensions of the third embodiment and a 100 kHz transformer + resonance coil using a ferrite core ML29D manufactured by Proterial Co., Ltd. are compared. The "bottom area" in FIG. 22 corresponds to the area (occupied area) occupied by the matrix transformer when viewed in a direction perpendicular to the paper surface of FIG. 6 or FIG. 7, for example. The third embodiment has a larger area of ​​1.8 times, but a height of 0.4 times and a volume of 0.7 times. In particular, the thinness is advantageous in that it improves heat dissipation from the transformer and meets the demand for a thin power supply. Furthermore, by integrating the resonance coil into the matrix transformer, it is possible to further reduce the cost and size of the high-frequency switching power supply.

[0049] (Fourth embodiment) 23 is a diagram showing a cross-sectional view of an embodiment of the present disclosure. In the matrix transformer 6e of this embodiment, bar-shaped ferrite cores 52b and 52c are sandwiched between the butt surfaces of each pair of U-shaped ferrite cores 21 and 22 (the butt surfaces correspond to the end surfaces of the legs of the U-shaped ferrite cores), and a primary coil 3 and a secondary coil 4 are wound around the U-shaped ferrite cores 11, 12, 21, and 22. The bar-shaped ferrite cores 52b and 52c are provided as magnetic circuit bypasses. However, the magnetic circuits at both ends using the U-shaped ferrite cores 11 and 12 do not have a magnetic circuit bypass between the bar-shaped ferrite cores 51b and 52b.

[0050] The embodiment in FIG. 23 differs from the embodiment in FIG. 8 in that a magnetic circuit bypass is provided for some of the m transformers, not for all of them. This configuration is suitable for shortening the magnetic gap length in the magnetic circuit bypass, and is expected to reduce fringing. In the embodiment in FIG. 23, m=3, and since there is no magnetic circuit bypass in the magnetic circuits at both ends, the magnetic gap length in the two central magnetic circuits can be set to be small. Note that fringing is a phenomenon in which the magnetic flux expands in an attempt to make the cross-sectional area through which the magnetic flux passes larger than the cross-sectional area of ​​the core, as the magnetic gap acts to reduce magnetic resistance, and an increase in fringing can lead to an increase in loss.

[0051] The matrix transformer of the present disclosure described above converts electric power into magnetic force, and converts the magnetic force into electric power, transmitting energy between circuits via windings. This matrix transformer is different from a reactor. A reactor uses windings, but is a component that prevents current from flowing when the voltage changes, generating a magnetic field instead to temporarily store energy, and is therefore different from the matrix transformer of the present disclosure. [Explanation of symbols]

[0052] 11,12 … U-shaped ferrite core 1 111,121 … Legs of U-shaped ferrite core 1 112, 122 … Window of U-shaped ferrite core 1 113,123 … Yoke part of U-shaped ferrite core 1 114, 124 … U-shaped ferrite core 1 butt surface 21, 22 … U-shaped ferrite core 2 211, 221 … Legs of U-shaped ferrite core 2 212, 222 … Window of U-shaped ferrite core 2 213,223 … Yoke part of U-shaped ferrite core 2 214, 222 … Butt surface of U-shaped ferrite core 2 3 … Primary coil 311, 312 … Primary side printed coil 1st layer (surface layer) pad 321, 322, 323, 324 … Second layer coil pattern of primary printed coil 331, 332, 333, 334 … Primary side printed coil 3rd layer coil pattern 341, 342 … Primary side printed coil 4th layer (back layer) pad 351, 352, 353, 354, 355 … Primary side printed coil interlayer via holes 4 … Secondary coil 51 ... Bar-shaped ferrite core 1 51b ... Bar-shaped ferrite core 52 ... Bar-shaped ferrite core 2 52b ... Bar-shaped ferrite core 52c ... Bar-shaped ferrite core 6a ... Matrix transformer of the first embodiment of the present disclosure 6b, 6c ... Matrix transformer according to the second embodiment of the present disclosure 6d ... Matrix transformer of the third embodiment of the present disclosure 6e ... Matrix transformer according to the fourth embodiment of the present disclosure 61 ... Leakage inductor in the third embodiment of the present disclosure 71 … Input voltage 721 … Input filter capacitor 722, 723, 724, 725 … MOSFET drain-source capacitance 728 ... Resonant capacitor 727,7287 … Capacitor for output filter 731,732,733,734 … MOSFET 741, 742, 743, 744 … Rectifier diode 75 … Output filter inductor 76 … Load

Claims

1. A matrix transformer for use in a high-frequency switching power supply, A core body is formed by using two U-shaped ferrite cores each having two legs and one connecting part, and by arranging the butt faces of the legs so as to face each other, thereby forming a closed magnetic circuit; The magnetic circuit of the transformer includes m+1 core bodies, The core bodies are arranged one-dimensionally so as to be adjacent to each other to form a row of core bodies which constitute a magnetic circuit of the transformer, A matrix transformer comprising a primary coil and a secondary coil wound around the legs.

2. In the matrix transformer of claim 1, The core body has n rows, A matrix transformer, characterized in that the core bodies are arranged two-dimensionally so that the rows of the respective core bodies are adjacent to each other to form a core matrix that serves as a magnetic circuit of the transformer.

3. 3. The matrix transformer according to claim 1, wherein a magnetic path bypass is provided between all or some of the two U-shaped ferrite cores constituting said core body.

4. 3. The matrix transformer according to claim 1, wherein in each row, the length of the connecting portions of the U-shaped ferrite cores at both ends is 50 to 70% of the length of the connecting portions of the other U-shaped ferrite cores.

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