Capacitance-sensing integrated transformer with self-healing capability and manufacturing method thereof

Abstract

The application discloses a capacitor-inductor integrated transformer with a self-healing capacity of a capacitor and a preparation method thereof, which can be used in an LLC resonant converter. The transformer introduces an iron-based nanocrystal to replace a conventional ferrite as a magnetic core, so that the saturation magnetic flux density and the Curie temperature of the transformer are improved; a thin-film capacitor is integrated in the transformer, the thin-film capacitor is composed of the iron-based nanocrystal, a zinc-aluminum alloy and an insulating medium, the iron-based nanocrystal and the zinc-aluminum alloy are alternately distributed in intervals, and an insulating film filled between the iron-based nanocrystal and the zinc-aluminum alloy serves as a dielectric, so that an equivalent thin-film capacitor is formed; meanwhile, the zinc-aluminum alloy layer has the characteristics of thin thickness and easy melting, so that the thin-film capacitor can automatically form an isolation area at the time of short circuit, has the self-healing capacity of the capacitor, and significantly improves the power density, the economy and the safety of the device.

Description

Technical Field

[0001] This invention relates to the technical field of transformers, and in particular to an integrated capacitive-inductor transformer with self-healing capacitance and its manufacturing method. Background Technology

[0002] In the field of magnetic core materials, soft magnetic ferrites (such as Mn-Zn and Ni-Zn systems) are widely used due to their high resistivity and low core loss at high frequencies. However, as switching frequencies increase towards the MHz level to meet higher power density requirements, the relatively low saturation magnetic flux density of ferrite materials leads to a significant increase in losses at high frequencies, limiting their application performance. In recent years, iron-based nanocrystalline alloys have been considered ideal alternatives to ferrites for high-frequency magnetic components due to their extremely high saturation magnetic induction, high permeability, low high-frequency core loss, and good temperature stability, aiming to achieve miniaturization and high efficiency of magnetic components.

[0003] On the other hand, current resonant converters typically require discrete components such as film capacitors or ceramic capacitors. The installation of these discrete capacitors necessitates additional space and connection terminals, increasing the system's size and cost. Existing technology (Multilayer flexible printed circuitry planar transformer with integrated series capacitance for LLC converter) utilizes the interlayer parasitic capacitance of the coil windings as the resonant capacitor. However, the magnetic components in this technology are two-port, and the capacitor connection method and capacitance value are not flexible enough, greatly limiting the freedom of circuit design. Therefore, this patent proposes integrating film capacitors into the transformer using iron-based nanocrystals and zinc-aluminum alloys to form an integrated capacitive-inductive transformer, significantly improving the overall power density of the system.

[0004] LLC resonant converters are widely used in high-efficiency, high-power-density switching power supplies due to their ability to achieve zero-voltage turn-on of the primary-side switch and zero-current turn-off of the secondary-side rectifier over a wide load range, making them a typical application scenario for this invention. Their core components typically include a resonant inductor, a resonant capacitor, and a transformer magnetizing inductor. In traditional designs, these magnetic and capacitive components are often independent discrete devices, connected by external circuitry to form a resonant network, which limits further improvements in power density. Using the integrated capacitive-inductor transformer described in this invention, the core components of the LLC resonant converter can be integrated into a single component. Summary of the Invention

[0005] The purpose of this invention is to provide a safer, higher power density integrated capacitive-inductor transformer with capacitor self-healing capability and its fabrication method, applicable to LLC resonant converters. It employs alternating windings of iron-based nanocrystals and zinc-aluminum alloy, with an insulating film filling the spaces between them as the dielectric. The iron-based nanocrystal layer has the highest volume fraction and serves as the transformer core; the high-conductivity nanocrystals and zinc-aluminum alloy together act as plates, and the insulating film between the strips serves as the dielectric, thus integrating the resonant capacitor within the core to form the integrated capacitive-inductor transformer structure. Simultaneously, the extremely thin zinc-aluminum alloy vapor-deposited layer provides capacitor self-healing capability, significantly improving the power density, economy, and safety of the power device.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows: an integrated transformer with capacitive and inductive functions that has self-healing capability, the transformer comprising a magnetic core and a thin-film capacitor, the magnetic core being composed of iron-based nanocrystals to improve the transformer's saturation magnetic flux density and Curie temperature; the thin-film capacitor comprising iron-based nanocrystals and zinc-aluminum alloy as capacitor plates, with an insulating film filling between them as a dielectric.

[0007] Furthermore, the transformer is made of iron-based nanocrystalline strip and zinc-aluminum alloy strip; the iron-based nanocrystalline strip comprises iron-based nanocrystals and an insulating film, which are bonded together by resin adhesive or electrostatic adsorption; the zinc-aluminum alloy strip comprises zinc-aluminum alloy and an insulating film, which are bonded together by vacuum evaporation.

[0008] Furthermore, using a custom-shaped skeleton, two rolls of iron-based nanocrystalline strip and zinc-aluminum alloy strip are simultaneously wound into the desired transformer shape. During winding, the iron-based nanocrystalline strip and zinc-aluminum alloy strip are first fixed at the winding starting point on the skeleton plane. While fixing the initial position, the two rolls of strip are simultaneously offset to both sides of the skeleton plane in the width direction, so that the two rolls of strip have outward protruding areas on both sides of the skeleton plane, called protruding sides, and then wound into a transformer with the required number of layers.

[0009] Furthermore, after the transformer is wound, zinc powder is sprayed onto the outwardly protruding areas to draw out the protruding iron-based nanocrystals or zinc-aluminum alloys, forming the two poles of the thin-film capacitor.

[0010] Furthermore, in the width direction of the iron-based nanocrystalline strip and the zinc-aluminum alloy strip, one side of each is the protruding side, and an insulating film is covered on the other side of the strip. The thickness of the insulating film is less than that of the dielectric insulating film, so as to completely wrap the iron-based nanocrystalline and zinc-aluminum alloy on that side, thereby isolating zinc powder and preventing short circuits between capacitor layers.

[0011] Furthermore, when a short-circuit fault occurs in the dielectric of the film capacitor, the high temperature generated by the electric arc rapidly melts and evaporates the zinc-aluminum alloy in a very small area around the breakdown point, and then re-condenses on the surface of the surrounding dielectric to form an annular isolation zone, thereby achieving self-healing of the short-circuit fault of the film capacitor.

[0012] Furthermore, during normal operation, the iron-based nanocrystals constitute the magnetic core of the transformer, and the iron-based nanocrystals, zinc-aluminum alloy, and insulating film constitute the film capacitor. The electric and magnetic fields in them interact positively without interfering with each other, and the transformer and film capacitor have no internal electrical connection.

[0013] This invention also provides a method for fabricating the above-mentioned integrated capacitive-inductor transformer with self-healing capacitance, comprising the following steps:

[0014] 1) Determine the shape and number of winding layers of the integrated transformer with capacitive and inductive properties, the thickness and width of the iron-based nanocrystals, the thickness and width of the zinc-aluminum alloy, and the thickness and width of the insulating film according to the electrical parameter design objectives under the application scenario, and fabricate the frame according to the shape of the transformer.

[0015] 2) Using iron-based nanocrystalline raw materials, zinc-aluminum alloy raw materials, and insulating film raw materials, iron-based nanocrystalline strips and zinc-aluminum alloy strips of the required width and thickness are prepared. The iron-based nanocrystalline strips contain iron-based nanocrystals and insulating films, which are bonded together by resin adhesive or electrostatic adsorption. The zinc-aluminum alloy strips contain zinc-aluminum alloys and insulating films, which are bonded together by vacuum evaporation.

[0016] 3) Fix the skeleton, iron-based nanocrystalline strip and zinc-aluminum alloy strip on the winding roller respectively. Fix the two rolls of iron-based nanocrystalline strip and zinc-aluminum alloy strip at the starting point of winding at the same time, and make the two rolls of strip misaligned in the strip width direction. At the same time, tighten the iron-based nanocrystalline strip and zinc-aluminum alloy strip to make the strip taut. Then, while rotating the roller, wind the iron-based nanocrystalline strip and zinc-aluminum alloy strip onto the skeleton.

[0017] 4) After the winding is completed, take out the transformer and place it in the spraying equipment. Spray zinc powder on both sides of the strip. Then take it out and remove the skeleton to complete the preparation of the integrated transformer with capacitive and inductive components.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0019] This invention uses iron-based nanocrystals instead of conventional ferrite as the magnetic core, improving the transformer's saturation flux density and Curie temperature. Leveraging the high conductivity of iron-based nanocrystals and zinc-aluminum alloys, a winding process integrates capacitors into the transformer in the form of thin-film capacitors, thereby integrating capacitive and inductive components from various applications (such as LLC resonant converters) into a single component. Simultaneously, utilizing the thinness and volatility of zinc-aluminum alloys, the thin-film capacitors automatically form an isolation region during short circuits, possessing self-healing capabilities, significantly improving the device's power density, cost-effectiveness, and safety. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the integrated transformer with capacitive and inductive functions in Example 1.

[0021] Figure 2 This is a schematic diagram of the component configuration of the LLC resonant converter using an integrated capacitive-inductive transformer in Example 2.

[0022] Figure 3 This is a schematic diagram of an LLC resonant converter circuit using an integrated capacitive-inductor transformer in Example 2. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0024] Example 1

[0025] like Figure 1 As shown, this embodiment discloses an integrated capacitive-inductor transformer with self-healing capacitance. The transformer includes a magnetic core and a thin-film capacitor. The magnetic core is formed by alternating windings of two rolls of strip material. One roll consists of iron-based nanocrystals and an insulating film, while the other roll consists of a zinc-aluminum alloy and an insulating film. The iron-based nanocrystals are 18 micrometers thick, the zinc-aluminum alloy is 10 nanometers thick, and the insulating film is made of polypropylene, with a dielectric portion having a thickness of 10 micrometers and an insulating cover layer portion having a thickness of 2 micrometers. At one end of all the strip material, the width of the metal layer (iron-based nanocrystals and zinc-aluminum alloy) is slightly smaller than that of the insulating film, and the insulating film used as the insulating cover layer is... Figure 1The method shown is applied over the metal layer to achieve isolation between the iron-based nanocrystals and the zinc-aluminum alloy. The iron-based nanocrystal strip and the zinc-aluminum alloy strip are wound alternately and in a staggered manner, forming protruding portions at the top and bottom of the magnetic core, respectively. Zinc powder is then sprayed onto both sides of the magnetic core. Specifically, firstly, using a custom-shaped frame, the two rolls of iron-based nanocrystal strip and zinc-aluminum alloy strip are simultaneously wound into the desired transformer shape. During winding, the iron-based nanocrystal strip and the zinc-aluminum alloy strip are simultaneously fixed at the winding starting point on the frame plane. While fixing the initial position, the two rolls of strip are simultaneously offset towards both sides of the frame plane in the width direction, so that each roll of strip has an outward protruding area on both sides of the frame plane, called the protruding side. Then, the transformer with the required number of layers is wound. After the transformer is wound, zinc powder is sprayed onto the outward protruding areas to lead out the protruding iron-based nanocrystals or zinc-aluminum alloy, forming the two poles of the thin-film capacitor. Because the electrical conductivity of iron-based nanocrystals is approximately 5 × 10⁻⁶. 6 The conductivity of zinc-aluminum alloy is approximately 20 × 10⁻⁶ S / m. 6 S / m, and the insulating film is a superior dielectric material (relative permittivity 3-5), so the two ends of the magnetic core are led out to serve as the two poles of the film capacitor.

[0026] In the embodiment, the coil is based on Figure 1 The magnetic field in the core is distributed circumferentially along the core, while the electric field inside the thin-film capacitor is distributed radially along the core. The two fields are orthogonal to each other and do not affect each other.

[0027] The iron-based nanocrystals used are annealed using a special magnetic field process. In this process, an external magnetic field of a specific direction is added to the FeCuNbSiB alloy during the annealing process, which transforms the FeCuNbSiB alloy from an amorphous state to a nanocrystalline state. By adjusting the direction and amplitude of the external magnetic field, the relative permeability of the nanocrystalline FeCuNbSiB alloy is reduced, and its conductivity is increased. This effectively reduces the core loss of the transformer and prevents the core from operating in a saturated state.

[0028] The zinc-aluminum alloy is extremely thin. When a localized point on the dielectric film is broken down by high voltage due to weaknesses such as microscopic impurities, bubbles, or mechanical damage, the high temperature generated by the electric arc is sufficient to rapidly melt and evaporate the zinc-aluminum alloy in a very small area around the breakdown point. The evaporated zinc-aluminum alloy is blown away from the breakdown point by the energy of the electric arc and re-condenses on the surrounding dielectric surface. Thus, a metal-free annular isolation zone is formed around the original breakdown point, restoring the insulation of the dielectric. Therefore, the thin-film capacitor of the integrated capacitive-inductive transformer of this invention has self-healing capabilities, which improves safety.

[0029] The following is a method for fabricating the integrated capacitive-inductor transformer with self-healing capacitance described in this embodiment, including the following steps:

[0030] 1) Determine the shape and number of winding layers of the integrated transformer with capacitive and inductive properties, the thickness and width of the iron-based nanocrystals, the thickness and width of the zinc-aluminum alloy, and the thickness and width of the insulating film according to the electrical parameter design objectives under the application scenario, and fabricate the frame according to the shape of the transformer.

[0031] 2) Using iron-based nanocrystalline raw materials, zinc-aluminum alloy raw materials, and insulating film raw materials, iron-based nanocrystalline strips and zinc-aluminum alloy strips of the required width and thickness are prepared. The iron-based nanocrystalline strips contain iron-based nanocrystals and insulating films, which are bonded together by resin adhesive or electrostatic adsorption. The zinc-aluminum alloy strips contain zinc-aluminum alloys and insulating films, which are bonded together by vacuum evaporation.

[0032] 3) Fix the skeleton, iron-based nanocrystalline strip and zinc-aluminum alloy strip on the winding roller respectively. Fix the two rolls of iron-based nanocrystalline strip and zinc-aluminum alloy strip at the starting point of winding at the same time, and make the two rolls of strip misaligned in the strip width direction. At the same time, tighten the iron-based nanocrystalline strip and zinc-aluminum alloy strip to make the strip taut. Then, while rotating the roller, wind the iron-based nanocrystalline strip and zinc-aluminum alloy strip onto the skeleton.

[0033] 4) After the winding is completed, take out the transformer and place it in the spraying equipment. Spray zinc powder on both sides of the strip. Then take it out and remove the skeleton to complete the preparation of the integrated transformer with capacitive and inductive components.

[0034] Example 2

[0035] like Figure 2 As shown, this embodiment discloses an LLC resonant converter using the integrated capacitive-inductor transformer described in Embodiment 1, which includes a DC source, an inverter, an integrated capacitive-inductor transformer, a rectifier, and a load. The high-frequency inverter adopts an existing half-bridge or full-bridge inverter circuit; the rectifier is a passive or active rectifier circuit. The integrated capacitive-inductor transformer is equivalent to the transformer, resonant inductor, and resonant capacitor in a conventional LLC resonant converter, all integrated into one component.

[0036] like Figure 3 The diagram shown is of an LLC resonant converter based on a primary-side full-bridge inverter and a secondary-side passive rectifier. It includes a DC source module, an inverter module, an integrated capacitive-inductor transformer module, a rectifier module, and a load module. The DC source module includes a DC source... and input-side filter capacitor The inverter module includes a first switching transistor. Second switching transistor Third switching transistor and the fourth switching transistor The integrated transformer module with capacitive and inductive functions includes a resonant inductor. Magnetizing inductor Resonant capacitor and ideal transformer (Transformation ratio is n:1); the rectifier module includes a first diode. Second diode Third diode Fourth diode and output-side filter capacitor The load module includes a resistive load. Using the iron-based nanocrystalline magnetic core of the aforementioned integrated capacitive-inductive transformer as a transformer is equivalent to... Figure 3 The excitation inductor in and ideal transformer The leakage inductance of the integrated capacitive-inductor transformer is used as the resonant inductance of the LLC resonant converter. It is mainly related to factors such as the winding method and the number of turns of the coil. The thin-film capacitor of the integrated capacitive-inductor transformer is used as the resonant capacitor of the LLC resonant converter. The thickness and number of layers of the insulating film are mainly related to this. During the design process, the parameter range of the LLC resonant converter (mainly referring to the magnetizing inductance, resonant inductance, and resonant capacitor) is first determined based on the design objectives. Then, the thickness and number of layers of the strip are designed according to these parameters. The inverter converts the DC input into a square-wave AC input, which, after passing through the integrated capacitive-inductor transformer, enables step-up or step-down power transmission. The AC signal induced on the secondary side of the integrated capacitive-inductor transformer provides DC power to the resistive load through a rectifier. If the DC input voltage fluctuates, the DC input / output voltage gain of the LLC resonant converter can be changed by adjusting the inverter's operating frequency, thereby maintaining a stable output voltage.

[0037] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. An integrated capacitive-inductor transformer with self-healing capacitance, the transformer comprising a magnetic core and a thin-film capacitor, characterized in that, The magnetic core is made of iron-based nanocrystals to improve the saturation magnetic flux density and Curie temperature of the transformer; the thin-film capacitor is made of iron-based nanocrystals and zinc-aluminum alloy to form capacitor plates, and an insulating film is filled between them as a dielectric.

2. The integrated capacitive-inductor transformer with self-healing capacitance as described in claim 1, characterized in that, The transformer is made of iron-based nanocrystalline strip and zinc-aluminum alloy strip; the iron-based nanocrystalline strip contains iron-based nanocrystals and an insulating film, which are bonded together by resin adhesive or electrostatic adsorption; the zinc-aluminum alloy strip contains zinc-aluminum alloy and an insulating film, which are bonded together by vacuum evaporation.

3. The integrated capacitive-inductor transformer with self-healing capacitance as described in claim 2, characterized in that, Using a custom-shaped skeleton, two rolls of iron-based nanocrystalline strip and zinc-aluminum alloy strip are simultaneously wound into the desired transformer shape. During winding, the iron-based nanocrystalline strip and zinc-aluminum alloy strip are first fixed at the winding starting point on the plane of the skeleton. While fixing the initial position, the two rolls of strip are simultaneously offset to both sides of the skeleton plane in the width direction, so that the two rolls of strip have outward protruding areas on both sides of the skeleton plane, called protruding sides. Then, they are wound into a transformer with the required number of layers.

4. The integrated capacitive-inductor transformer with self-healing capacitance as described in claim 3, characterized in that, After the transformer is wound, zinc powder is sprayed onto the outwardly protruding areas to draw out the protruding iron-based nanocrystals or zinc-aluminum alloys, forming the two poles of the thin-film capacitor.

5. The integrated capacitive-inductor transformer with self-healing capacitance as described in claim 4, characterized in that, In the width direction of the iron-based nanocrystalline strip and the zinc-aluminum alloy strip, one side of each is the protruding side. An insulating film is covered on the other side of the strip, with a thickness less than that of the insulating film serving as a dielectric. This film is used to completely encapsulate the iron-based nanocrystalline material and the zinc-aluminum alloy on that side, thereby isolating zinc powder and preventing short circuits between capacitor layers.

6. The integrated capacitive-inductor transformer with self-healing capacitance as described in claim 5, characterized in that, When a short-circuit fault occurs in the dielectric of a film capacitor, the high temperature generated by the electric arc rapidly melts and evaporates the zinc-aluminum alloy in a very small area around the breakdown point. Subsequently, it re-condenses on the surface of the surrounding dielectric to form an annular isolation zone, thereby achieving self-healing of the short-circuit fault of the film capacitor.

7. The integrated capacitive-inductor transformer with self-healing capacitance as described in claim 6, characterized in that, During normal operation, the iron-based nanocrystals constitute the magnetic core of the transformer, and the iron-based nanocrystals, zinc-aluminum alloy, and insulating film constitute the film capacitor. The electric and magnetic fields in them interact positively without interfering with each other, and the transformer and film capacitor have no internal electrical connection.

8. The method for preparing the integrated capacitive-inductor transformer with self-healing capacitance as described in any one of claims 1-7, characterized in that, Includes the following steps: 1) Determine the shape and number of winding layers of the integrated transformer with capacitive and inductive properties, the thickness and width of the iron-based nanocrystals, the thickness and width of the zinc-aluminum alloy, and the thickness and width of the insulating film according to the electrical parameter design objectives under the application scenario, and fabricate the frame according to the shape of the transformer. 2) Using iron-based nanocrystalline raw materials, zinc-aluminum alloy raw materials, and insulating film raw materials, iron-based nanocrystalline strips and zinc-aluminum alloy strips of the required width and thickness are prepared. The iron-based nanocrystalline strips contain iron-based nanocrystals and insulating films, which are bonded together by resin adhesive or electrostatic adsorption. The zinc-aluminum alloy strips contain zinc-aluminum alloys and insulating films, which are bonded together by vacuum evaporation. 3) Fix the skeleton, iron-based nanocrystalline strip and zinc-aluminum alloy strip on the winding roller respectively. Fix the two rolls of iron-based nanocrystalline strip and zinc-aluminum alloy strip at the starting point of winding at the same time, and make the two rolls of strip misaligned in the strip width direction. At the same time, tighten the iron-based nanocrystalline strip and zinc-aluminum alloy strip to make the strip taut. Then, while rotating the roller, wind the iron-based nanocrystalline strip and zinc-aluminum alloy strip onto the skeleton. 4) After the winding is completed, take out the transformer and place it in the spraying equipment. Spray zinc powder on both sides of the strip. Then take it out and remove the skeleton to complete the preparation of the integrated transformer with capacitive and inductive components.

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