Coupling inductor and voltage conversion circuit
By introducing a third magnetic core structure into the coupled inductor and adjusting the coupling coefficient between the windings, the loss and safety issues of the coupled inductor under different operating modes are solved, achieving miniaturization and low cost of the inductor while improving reliability.
Patent Information
- Application Number
- CN202423305048.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2026-02-17
- Estimated Expiration
- 2034-12-31
AI Technical Summary
Existing coupled inductors have additional winding losses and core losses when operating with a single winding or multiple windings, and may falsely trigger disconnected windings, affecting reliability and safety.
Design a coupled inductor comprising a three-core structure, wherein the magnetic flux of two parallel windings of the cores is in opposite directions, and the third core is saturated when needed to adjust the coupling coefficient and prevent magnetic flux from flowing into unwanted windings.
The coupling coefficient is automatically adjusted at different operating stages to reduce inductor size and cost, reduce losses, and improve reliability and safety.
Smart Images
Figure CN223927193U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of power electronics technology, and in particular to a coupled inductor and a voltage conversion circuit including the coupled inductor. Background Technology
[0002] In voltage conversion circuits (e.g., high-power boost converters) of power generation, transmission, or storage systems, inductors are responsible for storing and transmitting the electromagnetic energy of the main circuit. Therefore, the size, losses, and price of inductors account for a significant portion of the overall system cost. For conventional inductors, the magnetic flux density of the core material is limited due to its nonlinearity. To guide the magnetic flux generated by the inductor windings, there are minimum size constraints on the core, resulting in a large overall size and high cost for the inductor.
[0003] To reduce the size and cost of inductors, magnetic integration is widely used in voltage conversion circuits. Among existing magnetic integration methods, coupled inductors are a popular design. In a coupled inductor, there are two current windings connected in parallel. Because the magnetic flux flows in opposite directions in the two windings, the magnetic flux generated by the two windings cancels each other out. Therefore, the size of each magnetic core can be reduced, thereby further reducing the size and cost of the inductor.
[0004] For coupled inductors, the coupling coefficient is typically used to describe the degree of coupling between the two windings. For example, in DC / DC voltage conversion circuits used in fuel cell systems, the coupling coefficient of a deeply coupled inductor in reverse configuration is preferably -0.6 to -0.9. However, fuel cell systems do not always operate with both windings running simultaneously; sometimes there are periods where only a single winding needs to operate. In this case, only one winding has excitation current, while the other winding is electrically disconnected. However, due to the deep magnetic coupling between the two windings, the magnetic flux generated by one winding will enter the opposite winding, resulting in an induced voltage on the electrically disconnected winding. This will cause additional winding and core losses, and in the worst case, if the induced voltage is too high, it may even falsely trigger the disconnected winding.
[0005] Therefore, existing coupling devices and voltage conversion circuits need to be improved to reduce losses and enhance reliability and safety. Utility Model Content
[0006] The purpose of this application is to provide an improved coupling device and a voltage conversion circuit including the coupling inductor to overcome at least one of the above-mentioned technical problems.
[0007] Therefore, according to one aspect of this application, a coupled inductor is provided, comprising: a first inductor assembly including a first magnetic core and a first winding, the first winding being wound around the first magnetic core; and a second inductor assembly including a second magnetic core and a second winding, the second winding being wound around the second magnetic core; wherein the first winding and the second winding are configured such that when connected in parallel with a power source, the magnetic flux generated in the first magnetic core flows in the opposite direction to the magnetic flux generated in the second magnetic core; wherein the coupled inductor further comprises a third magnetic core disposed between the first magnetic core and the second magnetic core, and configured such that when an excitation current is applied to one of the first winding and the second winding, the magnetic flux generated by the coupled inductor flows through the third magnetic core, while when an excitation current is applied to both the first winding and the second winding simultaneously, the magnetic flux generated by the coupled inductor saturates the third magnetic core and prevents the magnetic flux from flowing through the third magnetic core.
[0008] According to one embodiment of this application, the first magnetic core and the second magnetic core each have a first end and a second end, the first end of the first magnetic core and the first end of the second magnetic core are opposite to each other and spaced apart by a predetermined gap, and the second end of the first magnetic core and the second end of the second magnetic core are opposite to each other and spaced apart by the predetermined gap.
[0009] According to one embodiment of this application, the two ends of the third magnetic core are spaced apart from the first end and the second end of each of the first magnetic core and the second magnetic core by a first distance or are in contact with each other.
[0010] According to one embodiment of this application, the third magnetic core includes a first portion and a second portion opposite to each other, at least one of the first portion and the second portion having a shape that tapers from one end to the other.
[0011] According to one embodiment of this application, the shape of each of the first portion and the second portion is configured such that a maximum magnetic reluctance exists at at least one location from one end to the other.
[0012] According to one embodiment of this application, the first portion and the second portion are spaced apart by a second distance, in contact with each other, or formed as one.
[0013] According to one embodiment of this application, the third magnetic core is made of at least one selected from powder core materials, nanocrystalline materials, amorphous materials and ferrite materials.
[0014] According to one embodiment of this application, the first magnetic core and the second magnetic core have the same shape and are made of the same material.
[0015] According to one embodiment of this application, the predetermined gap is an air gap or is provided with a non-magnetic filler.
[0016] According to another aspect of this application, a voltage conversion circuit is provided, comprising: an input terminal receiving a voltage applied by a power source; a coupling inductor as described above receiving the voltage from the input terminal; an association circuit connected to the coupling inductor; and an output terminal outputting a voltage converted by the coupling inductor and the association circuit.
[0017] The coupled inductor provided in this application can automatically adjust the coupling coefficient between two mutually coupled windings at different operating stages of a voltage conversion circuit (e.g., single winding operation stage or multiple winding operation stage), so that the coupling coefficient increases when multiple windings need to operate and decreases when a single winding needs to operate. Attached Figure Description
[0018] Exemplary embodiments of this application will now be described in detail with reference to the accompanying drawings. It should be understood that the embodiments described below are for illustrative purposes only and are not intended to limit the scope of this application. In the accompanying drawings:
[0019] Figure 1 This is a schematic circuit diagram of a voltage conversion circuit according to an embodiment of this application;
[0020] Figure 2 This is a schematic cross-sectional view of a coupled inductor according to an embodiment of this application;
[0021] Figure 3 This is a schematic cross-sectional view of a coupled inductor according to another embodiment of this application. Detailed Implementation
[0022] Preferred embodiments of this application are described in detail below with reference to examples. Those skilled in the art should understand that these exemplary embodiments do not imply any limitation on this application. Furthermore, features in the embodiments of this application can be combined with each other unless otherwise specified. In different drawings, the same components may be represented by the same reference numerals, and other components are omitted for brevity, but this does not mean that the coupling inductor and voltage conversion circuit of this application cannot include other components or modules. It should be understood that the dimensions, scale relationships, and number of components in the drawings are not intended to limit this application.
[0023] The terms “first”, “second”, etc., used in this application are only used to distinguish different objects, and not to describe a specific order.
[0024] The following reference Figure 1This describes a voltage conversion circuit according to an embodiment of the present application, such as a DC / DC boost circuit for a fuel cell system. Figure 1 As shown, the voltage conversion circuit 100 may include an input terminal 101, a coupling inductor 50, an associated circuit 40, and an output terminal 102.
[0025] Input 101 receives a DC voltage applied by a power source (e.g., a fuel cell, a battery, etc.). It should be noted that input 101 may also receive a DC voltage provided by mains power after rectification and filtering.
[0026] The coupling inductor 50 receives voltage from input terminal 101 and is connected to the associated circuit 40. The associated circuit 40, together with the coupling inductor 50, can constitute the main circuit of the voltage conversion circuit 100, wherein the associated circuit 40 may include electronic components such as power transistors, capacitors, and diodes. As long as the coupling inductor 50 of this application can work with the associated circuit 40 to achieve the required voltage conversion, the associated circuit 40 can have different configurations according to different voltage conversion requirements. The specific configuration of the associated circuit 40 will not be further described herein and will not affect the understanding and implementation of the technical solution of this application.
[0027] Output terminal 102 outputs a voltage transformed by coupling inductor 50 and associated circuit 40. For example, in a fuel cell system, output terminal 102 can be connected to a load (e.g., to a battery to store electrical energy, or to a motor to output power).
[0028] like Figure 1 As shown, the coupling inductor 50 includes a first inductor assembly 10, a second inductor assembly 20, and a third magnetic core 30. The following will refer to... Figure 2 and Figure 3 The coupling inductor 50 is described in further detail.
[0029] Figure 2 A schematic cross-sectional view of a coupled inductor 50 according to one embodiment of this application is shown. Figure 2 As shown, the first inductor assembly 10 of the coupled inductor 50 includes a first magnetic core 11 and a first winding 12, wherein the first winding 12 is wound around the first magnetic core 11, and the second inductor assembly 20 of the coupled inductor 50 includes a second magnetic core 21 and a second winding 22, wherein the second winding 22 is wound around the second magnetic core 21. Thus, the coupled inductor 50 has two current windings, each winding as follows... Figure 2 The dashed box in the image is shown. Figure 2 In the diagram, the direction of current in the first winding 12 and the second winding 22 is schematically indicated by the symbols "x" and "·". The first winding 12 and the second winding 22 are configured to generate magnetic flux (e.g., when connected in parallel with a power source) within the first magnetic core 11. Figure 2 (As indicated by the clockwise arrow in the upper middle part) and the magnetic flux generated in the second magnetic core 21 (such as...) Figure 2 (As indicated by the counter-clockwise arrow in the lower middle section) The flow directions are opposite to each other. Since the magnetic flux generated by the two parallel current windings in the two magnetic cores flows in opposite directions, the generated magnetic fluxes cancel each other out. Therefore, while storing the same amount of energy, the size of each magnetic core of the coupled inductor 50 can be reduced, thereby further reducing the size and cost of the coupled inductor 50.
[0030] To facilitate flux cancellation between the first inductor assembly 10 and the second inductor assembly 20, the first magnetic core 11 and the second magnetic core 21 may have the same shape (e.g., C-shape) and be made of the same material (e.g., a ferromagnetic metal or alloy). It should be noted that the first magnetic core 11 and the second magnetic core 21 may also have different shapes (e.g., C-shape and I-shape) and be made of different materials, achieving flux cancellation in the same way. The first winding 12 and the second winding 22 may have the same or different numbers of turns and may be made of copper, aluminum, or their alloys.
[0031] To prevent additional winding and core losses caused by magnetic flux generated by one winding entering the opposite winding when a single winding of the coupled inductor is operating, or even to falsely trigger the other winding, the coupled inductor 50 of this application further includes a third magnetic core 30. The third magnetic core 30 is disposed between the first magnetic core 11 and the second magnetic core 21, and is configured such that when one of the first winding 12 and the second winding 22 is loaded with an excitation current, the magnetic flux generated by the coupled inductor 50 flows through the third magnetic core 30, while when both the first winding 12 and the second winding 22 are loaded with an excitation current, the magnetic flux generated by the coupled inductor 50 saturates the third magnetic core 30 and prevents it from flowing through.
[0032] Thus, when both windings of the coupled inductor 50 need to operate simultaneously (e.g., during heavy-load operation of a fuel cell system), the third magnetic core 30 saturates, preventing magnetic flux from passing through it. Therefore, the magnetic flux generated by one winding flows directly to the opposite winding, canceling out the fluxes and forming a deeply coupled inductor. Conversely, when only a single winding of the coupled inductor 50 needs to operate (e.g., during light-load operation of a fuel cell system), the third magnetic core 30 is unsaturated. The magnetic flux generated by one winding can flow through the third magnetic core 30 to form a magnetic flux loop, but it will not flow to the opposite winding. This avoids winding and core losses in the other winding and prevents accidental triggering of the other winding. Therefore, the coupled inductor 50 of this application not only possesses the advantages of a deeply coupled inductor (e.g., small size, low cost) but also reduces winding and core losses and improves reliability and safety.
[0033] like Figure 2 As shown, the first magnetic core 11 and the second magnetic core 21 each have a first end (e.g., in...). Figure 2 The right end) and the second end (e.g., in Figure 2 (Left end). Therefore, when only the first inductor assembly 10 is working, the magnetic flux generated in the first magnetic core 11 is in a clockwise direction (see...). Figure 2 The magnetic flux flows from the first end of the first magnetic core 11 into the third magnetic core 30, and after passing through the third magnetic core 30, returns to the second end of the first magnetic core 11, thus forming a magnetic flux loop. In this case, the magnetic flux generated in the first magnetic core 11 will not flow to the second magnetic core 21, thus avoiding the aforementioned disadvantages.
[0034] According to one embodiment of this application, the first end of the first magnetic core 11 and the first end of the second magnetic core 21 are opposite to each other and spaced apart by a predetermined gap D. Figure 2 The diagram only shows the predetermined gap between the first ends, and the second ends of the first magnetic core 11 and the second magnetic core 21 are opposite each other and spaced apart by a predetermined gap D. The predetermined gap D can provide low permeability, thereby affecting the flux flow and inductance value, and can therefore be set differently depending on the application of the coupled inductor and the required flux. Depending on the given application, the predetermined gap D can be an air gap, or it can be filled with a non-magnetic material, such as plastic, rubber, ceramic, wood, paper, etc., to adjust the effective permeability and other properties between the magnetic cores. It should be noted that in the foregoing description, the predetermined gap between the two ends of the first magnetic core 11 and the two ends of the second magnetic core 21 is the same, but it can also be different. Alternatively, the predetermined gap D can be omitted between the first magnetic core 11 and the second magnetic core 21, and the two magnetic cores can be in contact with each other, still achieving the technical concept of this application.
[0035] like Figure 2 As shown, the two ends of the third magnetic core 30 are spaced apart from the first and second ends of each of the first magnetic core 21 and the second magnetic core 22 by a first distance (not shown). This allows the third magnetic core 30 to form a magnetic flux loop with each of the first magnetic core 11 and the second magnetic core 21, enabling a predetermined magnetic flux flow. It should be noted that the two ends of the third magnetic core 30 may be spaced apart from the first and second ends of each of the first magnetic core 21 and the second magnetic core 22 by different distances or may be in contact with each other (see [reference]). Figure 3 The technical concept of this application can still be realized even with [the existing technology].
[0036] like Figure 2As shown, the third magnetic core 30 may include a first portion 31 and a second portion 32 opposite to each other, at least one of the first portion 31 and the second portion 32 having a tapered shape from one end to the other. For example, one end of the first portion 31 and / or the second portion 32 has a larger cross-sectional area, while the other end has a smaller cross-sectional area. In this case, the geometry of the third magnetic core 30 can be used to restrict the flow of magnetic flux. For example, when a single winding of the coupled inductor 50 is operating, the geometry of the third magnetic core 30 can be configured to allow magnetic flux to flow through the portion of the third magnetic core 30 with the smallest cross-section, thus achieving a magnetic flux loop for the single winding. Conversely, when both windings of the coupled inductor 50 are operating, the portion of the third magnetic core 30 with the smallest cross-section becomes magnetically saturated and cannot allow magnetic flux from both windings to pass through, thus achieving deep coupling between the two windings.
[0037] For example, the shape of each of the first portion 31 and the second portion 32 can be configured such that a maximum magnetic reluctance exists at at least one location from one end to the other. That is, the shapes of the first portion 31 and the second portion 32 result in varying magnetic reluctance along their longitudinal axis, with the maximum magnetic reluctance at at least one location and less at other locations. For example, each of the first portion 31 and the second portion 32 can have a conical (e.g., cone or pyramidal) shape, so that the apex of the cone shape can be the portion with the smallest cross-section, thus having the maximum magnetic reluctance. The purpose of setting the maximum magnetic reluctance is to limit the magnitude of the magnetic flux flow when magnetic flux saturation occurs, and the specific value can be determined according to design requirements. It should be noted that the first portion 31 and the second portion 32 can be made of the same or different materials and can have the same or different shapes. Figure 2 As shown, when each of the first portion 31 and the second portion 32 has a conical shape, the end of each of the first portion 31 and the second portion 32 with a larger cross-section is close to the ends of the first magnetic core 11 and the second magnetic core 21, while the end with a smaller cross-section is away from the ends of the first magnetic core 11 and the second magnetic core 21. This facilitates the guidance of the magnetic flux generated when a single inductor component is operating to the third magnetic core 30, and also limits the flow rate of the magnetic flux. It should be noted that the first portion 31 and the second portion 32 are not limited to the shapes described above and shown, but can be any suitable shape, as long as the desired change in magnetic reluctance exists in the longitudinal direction of the third magnetic core 30.
[0038] like Figure 2As shown, the first portion 31 and the second portion 32 can be spaced apart by a second distance (not shown). This allows for further definition of a magnetic flux loop within the third magnetic core 30, permitting the passage of a predetermined magnetic flux. It should be noted that the first portion 31 and the second portion 32 can also be in contact with each other or formed as a single unit, still achieving the technical concept of this application.
[0039] Figure 3 A schematic cross-sectional view of a coupled inductor according to another embodiment of this application is shown. Besides Figure 3 Apart from the different configuration of the third magnetic core shown, Figure 3 The coupled inductor shown is Figure 2 The coupling inductors shown are the same, so the same components will not be described again; only the differences will be described.
[0040] like Figure 3 As shown, the third magnetic core 30 is a monolithic structure with a constant cross-sectional size along its longitudinal direction. In this case, the third magnetic core 30 can be made of a soft magnetic material, such as at least one selected from powder core materials, nanocrystalline materials, amorphous materials, and ferrite materials. It should be noted that the material of the third magnetic core 30 is not limited to those mentioned above, but can also be other existing or future-developed soft magnetic materials. By using a soft magnetic material to make the third magnetic core 30, the flux flow rate when flux saturation occurs can also be limited. For example, when a single winding of the coupled inductor 50 is operating, flux can flow through the third magnetic core 30, thereby realizing a flux loop for the single winding. However, when both windings of the coupled inductor 50 are operating, the third magnetic core 30 made of soft magnetic material becomes flux saturated and cannot allow flux from both windings to pass through, thereby achieving deep coupling between the two windings.
[0041] According to various embodiments of this application, by incorporating a third magnetic core in the coupled inductor, the coupling coefficient between the two mutually coupled windings can be automatically adjusted at different operating stages of the voltage conversion circuit (e.g., when a single winding is operating or when two windings are operating). This increases the coupling coefficient when multiple windings are required to operate and decreases it when a single winding is required to operate. This reduces the size and cost of the coupled inductor, while also reducing losses and improving reliability and safety.
[0042] The present application has been described in detail above with reference to specific embodiments. Obviously, the above description and the embodiments shown in the accompanying drawings should be understood as exemplary and not as limiting the present application. Those skilled in the art can make various modifications or alterations without departing from the spirit of the present application, and such modifications or alterations do not depart from the scope of the present application.
Claims
1. A coupled inductor (50) comprising: a first inductor assembly (10) including a first magnetic core (11) and a first winding (12) wound around the first magnetic core (11); and a second inductor assembly (20) including a second magnetic core (21) and a second winding (22) wound around the second magnetic core (21); wherein the first winding (12) and the second winding (22) are configured to generate magnetic flux in the first magnetic core (11) in a direction opposite to that of the magnetic flux generated in the second magnetic core (21) when connected in parallel with a power supply; characterized in that the coupled inductor (50) further comprises a third magnetic core (30) disposed between the first magnetic core (11) and the second magnetic core (21) and configured such that the magnetic flux generated by the coupled inductor (50) flows through the third magnetic core (30) when one of the first winding (12) and the second winding (22) is loaded with an excitation current, while the magnetic flux generated by the coupled inductor (50) saturates the third magnetic core (30) and cannot flow through the third magnetic core (30) when the first winding (12) and the second winding (22) are simultaneously loaded with excitation currents. the first magnetic core (11) and the second magnetic core (21) each have a first end and a second end, the first ends of the first magnetic core (11) and the second magnetic core (21) are opposite to each other and spaced apart by a predetermined gap (D), and the second ends of the first magnetic core (11) and the second magnetic core (21) are opposite to each other and spaced apart by the predetermined gap (D).
2. The coupled inductor (50) of claim 1, characterized in that, the two ends of the third magnetic core (30) are spaced apart from the first end and the second end of each of the first magnetic core (11) and the second magnetic core (21) by a first distance or in contact with each other.
3. The coupled inductor (50) of claim 2, characterized in that, the third magnetic core (30) includes a first portion (31) and a second portion (32) opposite to each other, at least one of the first portion (31) and the second portion (32) has a shape tapering from one end to the other end thereof.
4. The coupled inductor (50) of claim 3, characterized in that, the shape of each of the first portion (31) and the second portion (32) is configured such that there is a maximum magnetic resistance at at least one position from one end to the other end thereof.
5. The coupled inductor (50) of claim 4, characterized in that, the first portion (31) and the second portion (32) are spaced apart from each other by a second distance, in contact with each other, or formed integrally.
6. The coupled inductor (50) of claim 4, characterized by the third magnetic core (30) is made of at least one selected from a powder core material, a nanocrystalline material, an amorphous material, and a ferrite material.
7. The coupled inductor (50) according to any one of claims 1 to 6, characterized in that the first magnetic core (11) and the second magnetic core (21) have the same shape and are made of the same material.
8. The coupled inductor (50) according to any one of claims 1 to 6, characterized in that the predetermined gap (D) is an air gap or provided with a non-magnetic filling.
9. The coupled inductor (50) of claim 2, characterized by, the voltage conversion circuit (100) comprises:
10. A voltage conversion circuit (100), characterized by an input end (101) receiving a voltage applied by a power supply; the coupled inductor (50) according to any one of claims 1 to 9, receiving the voltage from the input end (101); an associated circuit (40) connected to the coupled inductor (50); and an output (102) that outputs a voltage transformed by the coupled inductor (50) and the associated circuit (40).