DC-to-DC mode magnetic integrated flat transformer

Abstract

The invention discloses a DC-to-DC mode magnetic integrated flat transformer, which belongs to the technical field of power electronics, and comprises mirror magnetic cores, N coils and primary wire cakes, the mirror magnetic cores comprise a first mirror magnetic core and a second mirror magnetic core; the primary wire cakes comprise a first primary wire cake, a second primary wire cake and a third primary wire cake, an air gap magnetic core is arranged on the outer side of the first mirror surface magnetic core, and an N coil is arranged between the air gap magnetic core and the first mirror surface magnetic core; a first primary wire cake is arranged on the inner side of the first mirror magnetic core, the inner side of the second mirror magnetic core is connected with one side of an insulating plate, and the other side of the insulating plate is fixedly connected with a third primary wire cake in an attached mode. A first copper sheet group is arranged between the first primary wire cake and the second primary wire cake; and a second copper sheet group is arranged between the second primary wire cake and the third primary wire cake. The device is highly integrated, small in size and low in cost, and the die and material cost is reduced. The overall structure is flat, and the power density is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronics, and particularly relates to a DC-to-DC magnetic integrated planar transformer. BACKGROUND

[0002] With the development of modern electronic devices towards miniaturization, high efficiency and high reliability, higher requirements are put forward for the core power conversion components, i.e. DC-DC converters. LLC resonant converter has become one of the first topologies for medium and high power density power supply because it can realize zero-voltage turn-on ZVS of the primary side switching tube and zero-current turn-off ZCS of the secondary side rectifier tube, significantly reduce switching loss, and thus realize high efficiency and high power density. A typical LLC resonant converter usually includes three key magnetic elements: a resonant inductor Lr, a resonant capacitor Cr and a main transformer T. The resonant inductor Lr, the capacitor Cr and the magnetizing inductance Lm of the transformer constitute a resonant network, which is the core of the soft switching technology. In the traditional design scheme, the resonant inductor Lr and the main transformer T are two independent magnetic elements. This kind of separate design has many inherent shortcomings: first, two independent magnetic cores and winding structures occupy a large amount of circuit board space, limiting the further improvement of power supply power density; second, the material cost, manufacturing time and assembly cost of the two elements are added, resulting in high overall cost; third, the connecting leads between the two elements will introduce additional parasitic inductance, which may affect the accuracy of the resonant circuit and generate more electromagnetic interference EMI; finally, both elements will generate heat, and the dispersed heat sources increase the complexity.

[0003] In order to overcome the shortcomings of separate elements, magnetic integration technology emerges as the times require. This technology aims to integrate the functions of multiple magnetic elements in a single magnetic core structure through clever magnetic circuit and winding design. There are some attempts to integrate resonant inductors and transformers in the prior art, such as using custom magnetic core shapes or complex winding methods. However, these schemes often have new problems: the integrated magnetic core structure may be very complex, leading to difficult processing, high cost, large volume and low conversion efficiency. SUMMARY

[0004] In view of the existing problems, the present application aims to provide a DC-to-DC magnetic integrated planar transformer to solve the problems of very complex magnetic core structure, high cost, large volume and low conversion efficiency.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme: The application discloses a DC-to-DC magnetic integrated flat transformer, which comprises a mirror surface magnetic core, an N coil and primary wire cakes, the mirror surface magnetic core comprises a first mirror surface magnetic core and a second mirror surface magnetic core; the primary wire cakes comprise a first primary wire cake, a second primary wire cake and a third primary wire cake, the outer side of the first mirror surface magnetic core is provided with an air gap magnetic core, the N coil is arranged between the air gap magnetic core and the first mirror surface magnetic core; the inner side of the first mirror surface magnetic core is provided with the first primary wire cake, the inner side of the second mirror surface magnetic core is connected with one side of an insulating plate, and the other side of the insulating plate is fixedly connected with the third primary wire cake; a first copper sheet group is arranged between the first primary wire cake and the second primary wire cake; and a second copper sheet group is arranged between the second primary wire cake and the third primary wire cake.

[0006] As a further scheme of the application, the first mirror surface magnetic core and the second mirror surface magnetic core are arranged in mirror surface symmetry.

[0007] As a further scheme of the application, the first copper sheet group and the second copper sheet group are both composed of two groups of double copper sheets which are fixedly adhered to each other.

[0008] As a further scheme of the application, the input end and the output end of the first primary wire cake, the second primary wire cake and the third primary wire cake are respectively arranged in parallel.

[0009] As a further scheme of the application, the first insulating paper is arranged at the connection position of the N coil and the air gap magnetic core.

[0010] As a further scheme of the application, the second insulating paper is arranged at the connection position of the first primary wire cake and the first mirror surface magnetic core.

[0011] As a further scheme of the application, the polyimide film is arranged on the two sides of the first primary wire cake.

[0012] As a further scheme of the application, the polyimide film is arranged on the two sides of the second primary wire cake.

[0013] As a further scheme of the application, the polyimide film is arranged on the side of the third primary wire cake which is away from the insulating plate.

[0014] As a further scheme of the application, the first primary wire cake, the second primary wire cake and the third primary wire cake are flat wire cake structures which are etched from a multilayer printed circuit board (PCB) or are wound from flat copper wires.

[0015] Compared with the prior art, the application has the following beneficial effects: The application is highly integrated, small in size, low in cost, successfully integrates resonant inductance and main transformer in a compact module, completely saves the magnetic core, winding and assembly cost of independent resonant inductance, reduces the mold and material cost. The overall structure is flat, which greatly improves the power density. The application saves the independent resonant inductor through magnetic integration technology, significantly reduces the volume and cost, and realizes high power density, low leakage inductance, excellent heat dissipation performance and high conversion efficiency by virtue of the flat design and optimized winding process, and is especially suitable for vehicle power supply, communication equipment and other occasions with strict requirements on efficiency, volume and reliability. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is an assembly structure diagram of a DC-to-DC module magnetic integrated flat transformer.

[0017] In the figure: 1, mirror core; 2, air gap core; 3, first insulating paper; 4, N1 coil; 5, second insulating paper; 6, polyimide film; 7, first copper sheet group; 8, second copper sheet group; 9, insulating plate; 10, first primary wire cake; 11, second primary wire cake; 12, third primary wire cake; 13, first mirror core; 14, second mirror core. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the application will be clearly and completely described in the description of the application in combination with the drawings of the embodiments of the application; obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0019] In the description of the application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "provided with", "connected", "connected" should be understood in a broad sense; for example, it can be fixedly connected, or it can be detachably connected, or it can be integrally connected, or it can be mechanically connected, or it can be electrically connected, or it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0020] The purpose of the application is to overcome the shortcomings of the prior art, provide a DC-DC conversion module magnetic integrated flat transformer with novel structure, high integration and excellent performance. It ingeniously integrates resonant inductance and main transformer through the combination of mirror core + air gap core and flat winding design, aiming to effectively solve the problems of large volume, high cost, difficult heat dissipation and complex process existing in discrete magnetic elements and existing integrated solutions.

[0021] Please refer to Figure 1 A DC-to-DC mirror core integrated planar transformer, comprising a mirror core 1, an N1 coil 4 and a primary winding cake, the mirror core 1 comprising a first mirror core 13 and a second mirror core 14; the primary winding cake comprising a first primary winding cake 10, a second primary winding cake 11 and a third primary winding cake 12, the input end and the output end of the first primary winding cake 10, the second primary winding cake 11 and the third primary winding cake 12 being arranged in parallel respectively; the first mirror core 13 and the second mirror core 14 being arranged in mirror symmetry; An air gap core 2 is arranged on the outer side of the first mirror core 13, and the N1 coil 4 is arranged between the air gap core 2 and the first mirror core 13; a first primary winding cake 10 is arranged on the inner side of the first mirror core 13, and a polyimide film 6 is arranged on both sides of the first primary winding cake 10; a second insulating paper 5 is arranged at the connection between the first primary winding cake 10 and the first mirror core 13; a resonant inductor is formed; a physical air gap is prearranged in the magnetic circuit of the air gap core 2, and the inductance of the resonant inductor is accurately adjusted by adjusting the length of the air gap. The mirror core group is composed of a pair of standardized planar cores arranged oppositely, which is used to provide the main magnetic circuit of the main transformer. The air gap core is arranged on the outer side of the first mirror core, and an accurate physical air gap is preprocessed in the magnetic circuit of the air gap core. The air gap core and the N1 coil together form an independent resonant inductor magnetic circuit. The physical separation design of the "main magnetic circuit + resonant magnetic circuit" effectively reduces the coupling interference between the two functional magnetic circuits, so that the resonant inductor inductance can be independently and accurately adjusted by the air gap length.

[0022] The inner side of the second mirror core 14 is connected with one side of an insulating plate 9, and the other side of the insulating plate 9 is fixedly connected with the third primary winding cake 12; A first copper sheet group 7 is arranged between the first primary winding cake 10 and the second primary winding cake 11; a second copper sheet group 8 is arranged between the second primary winding cake 11 and the third primary winding cake 12; The first copper sheet group 7 and the second copper sheet group 8 are both composed of two groups of double copper sheets which are fixedly attached to each other; for realizing low-loss, large-current energy transmission and mechanical support. The N1 coil is directly wound on the air gap core, serving as a resonant inductor winding and being connected in series in the main power circuit. The primary winding cake group is the secondary winding of the main transformer in step-down applications, which is designed with large current and is composed of the first, second and third primary winding cakes in parallel by wires to achieve current sharing and reduce conduction loss. The three winding cakes adopt a planar structure and can be made of multi-layer PCB etching or flat copper strip, having extremely low DC resistance and excellent heat dissipation capacity. The first and second copper sheet groups are arranged between the winding cakes, and they are composed of two groups of double copper sheets, which not only provide reliable electrical interconnection, but also play a role in mechanical support and heat dissipation enhancement.

[0023] A first insulating paper 3 is arranged at the connection between the N1 coil 4 and the air gap core 2; The third primary winding cake 12 is provided with a polyimide film 6 on the side away from the insulating plate 9; The second primary winding cake 11 is provided with a polyimide film 6 on both sides; the first insulating paper is used to isolate the N1 coil and the air-gap magnetic core to prevent turn-to-turn breakdown; the second insulating paper is used to isolate the first primary winding cake and the first mirror magnetic core; and the polyimide films are respectively arranged on both sides and the outermost side of each primary winding cake to provide high-level, high-temperature-resistant interlayer insulation. In addition, an insulating plate is also arranged between the third primary winding cake and the second mirror magnetic core, further strengthening the insulation strength and safe creepage distance between the primary and the secondary.

[0024] The first primary winding cake 10, the second primary winding cake 11 and the third primary winding cake 12 are flat winding cake structures etched from multi-layer printed circuit boards (PCB) or wound from flat copper wires.

[0025] The first mirror magnetic core 13 and the second mirror magnetic core 14 and the air-gap magnetic core 2 are made of soft magnetic ferrite material with high saturation magnetic induction and low power loss.

[0026] In the first embodiment, an LLC resonant converter applied to an on-board charger (OBC) is taken as an example.

[0027] In the embodiment, the first mirror magnetic core 13 and the second mirror magnetic core 14 are PQ50 type soft magnetic ferrite cores, and the material is PC95 or the same type. The air-gap magnetic core 2 is a U-shaped core with a 0.5 mm concentrated air gap ground on the column.

[0028] The N1 coil 4 is wound with 15 turns of Litz wire and directly wound on the air-gap magnetic core 2. After winding, the first insulating paper 3 is pasted on the contact part between the N1 coil 4 and the magnetic core. The final inductance of the winding is about 25 μH.

[0029] The primary winding cake group is made of 4-ounce thick 4-layer PCB, and the winding pattern of multiple turns in series is etched. The electrical parameters of the three winding cakes are consistent. The first copper sheet group 7 and the second copper sheet group 8 are punched from 0.8 mm thick red copper sheets, each group is composed of two superimposed sheets, and is fixed by welding with the solder pads of the upper and lower winding cakes.

[0030] Insulating materials: the first insulating paper 3 and the second insulating paper 5 are 0.1 mm thick green shell paper. The polyimide film 6 is 0.05 mm thick and the temperature resistance grade is greater than 180℃. The insulating plate 9 is 0.5 mm thick epoxy resin plate.

[0031] The assembly process is as follows: place the air-gap magnetic core 2 assembly with the wound N1 coil 4 on the base; paste the second insulating paper 5 on the inside of the first mirror magnetic core 13, and then cover it on the air-gap magnetic core 2 assembly, so that the N1 coil 4 is wrapped in the middle.

[0032] Stacked in order: first polyimide film 6 - first primary pancake 10 - second polyimide film 6 - first copper sheet set 7 - third polyimide film 6 - second primary pancake 11 - fourth polyimide film 6 - second copper sheet set 8 - fifth polyimide film 6 - third primary pancake 12 - sixth polyimide film 6 - insulation board 9.

[0033] The second mirror surface magnetic core 14 is covered on the insulation board 9. The whole assembly is fixed tightly by special fixture, and finally the input and output ends of the three primary pancake are connected in parallel by copper wires.

[0034] The integrated transformer is applied to a vehicle-mounted OBCLLC circuit with an input of 400V and an output of up to 60V / 3000W. The N1 coil 4 is connected in series with a resonance capacitor of 33nF. During operation, the high-frequency alternating current generated by the full-bridge switching circuit passes through the resonance cavity formed by the N1 coil 4 and the resonance capacitor, and the energy is transmitted to the secondary, i.e. the primary pancake set, through magnetic coupling, and is output after synchronous rectification. Thanks to the integrated design and excellent heat dissipation, the temperature rise of the whole transformer module is less than 60K when the full power output, the peak efficiency of the whole machine is greatly increased, and the volume is greatly reduced compared with the traditional discrete scheme.

[0035] Compared with the prior art, the molded magnetic integrated flat transformer provided by the present application has the following advantages: The present application is highly integrated, small in size, and low in cost: the resonant inductor and the main transformer are successfully integrated in a compact module, completely eliminating the magnetic core, winding and assembly cost of the independent resonant inductor. The combination of standardized or approximately standardized magnetic cores reduces the mold and material costs. The overall structure is flat, which greatly improves the power density.

[0036] The present application has excellent performance and extremely high efficiency: the resonant inductance is independently controlled by the air gap of the air gap magnetic core, which is high in precision and good in consistency, and is beneficial to the optimization design of the LLC resonant cavity to realize soft switching. The primary side uses multiple pancake parallel and large cross-section copper sheet interconnection, which greatly reduces the copper loss of the secondary circuit. Excellent heat dissipation design enables the transformer to work at a higher power level with lower temperature rise. The overall efficiency is greatly increased.

[0037] The present application has excellent heat dissipation performance: the pancake, copper sheet set and large area exposed magnetic core surface form a high-efficiency heat conduction path, heat can be quickly conducted from the internal generating site to the surface and dissipated to the environment, which is particularly suitable for low-voltage high-current high-power output applications.

[0038] The present application has a solid structure and high reliability: the use of copper sheet set and insulation board enhances the mechanical strength of the overall structure, making the module more resistant to vibration and impact, suitable for harsh environments such as vehicle-mounted. The comprehensive insulation system ensures high electrical safety and long-term reliability.

[0039] The assembly process of the application is simple and suitable for automatic production: each component is a flat structure, the laminated assembly method is very clear, and it is easy to realize automatic taking and placing and pressing by a mechanical hand, which greatly improves the production efficiency and product consistency and reduces the labor cost. The application reduces cost, reduces volume, has high conversion efficiency, and the manufacturing process of the magnetic integrated transformer is simple. Through the magnetic integration technology, the independent resonant inductor is saved, the volume is significantly reduced, the cost is reduced, and at the same time, the flat design and optimized winding process are realized, high power density, low leakage inductance, excellent heat dissipation performance and high conversion efficiency are realized, and the application is especially suitable for vehicle power supply, communication equipment and other occasions with strict requirements on efficiency, volume and reliability.

[0040] For those skilled in the art, it is obvious that the present application is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, the scope of the present application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0041] In addition, it should be understood that although the present application is described in the specification according to the embodiments, each embodiment does not contain only one independent technical solution, and the description manner of the specification is only for the sake of clarity, and those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be properly combined to form other embodiments which can be understood by those skilled in the art.

Claims

1. A DC-to-DC analog-magnetic integrated planar transformer, characterized in that, The device includes a mirror magnetic core (1), an N (1) coil (4), and a primary coil. The mirror magnetic core (1) includes a first mirror magnetic core (13) and a second mirror magnetic core (14). The primary coil includes a first primary coil (10), a second primary coil (11), and a third primary coil (12). An air gap magnetic core (2) is provided on the outside of the first mirror magnetic core (13). An N (1) coil (4) is provided between the air gap magnetic core (2) and the first mirror magnetic core (13). The first primary coil (10) is provided on the inside of the first mirror magnetic core (13). The inside of the second mirror magnetic core (14) is connected to one side of an insulating plate (9). The other side of the insulating plate (9) is attached and fixedly connected to the third primary coil (12). A first copper sheet group (7) is provided between the first primary coil (10) and the second primary coil (11). A second copper sheet group (8) is provided between the second primary coil (11) and the third primary coil (12).

2. The DC-to-DC analog magnetic integrated flat-plate transformer according to claim 1, characterized in that, The first mirror magnetic core (13) and the second mirror magnetic core (14) are mirror-symmetrically arranged.

3. The DC-to-DC analog magnetic integrated flat-plate transformer according to claim 2, characterized in that, The first copper sheet group (7) and the second copper sheet group (8) are both composed of two groups of double copper sheets that are bonded and fixed together.

4. A DC-to-DC analog magnetic integrated flat-plate transformer according to claim 3, characterized in that, The input and output terminals of the first primary wire cake (10), the second primary wire cake (11), and the third primary wire cake (12) are respectively connected in parallel.

5. A DC-to-DC analog magnetic integrated flat-plate transformer according to claim 4, characterized in that, The connection between the N (1) coil (4) and the air gap core (2) is provided with a first insulating paper (3).

6. A DC-to-DC analog magnetic integrated flat-plate transformer according to claim 5, characterized in that, A second insulating paper (5) is provided at the connection between the first primary coil (10) and the first mirror magnetic core (13).

7. A DC-to-DC analog magnetic integrated flat-plate transformer according to claim 6, characterized in that, The first primary yarn cake (10) has polyimide films (6) on both sides.

8. A DC-to-DC analog magnetic integrated flat-plate transformer according to claim 7, characterized in that, The second primary yarn cake (11) is provided with polyimide film (6) on both sides.

9. A DC-to-DC analog magnetic integrated flat-plate transformer according to claim 8, characterized in that, The third primary coil (12) is provided with a polyimide film (6) on the side away from the insulating plate (9).

10. A DC-to-DC analog magnetic integrated flat-plate transformer according to claim 9, characterized in that, The first primary wire disc (10), the second primary wire disc (11), and the third primary wire disc (12) are all flat wire disc structures formed by etching of multilayer printed circuit boards (PCBs) or by winding of flat copper wires.

Images