Magnetic coupling energy storage element under high duty ratio and obtaining method

Abstract

The invention belongs to the field of power electronic device optimization design, and particularly discloses a magnetic coupling energy storage element under a high duty ratio and an obtaining method. The method comprises the following steps: establishing an output current ripple model; representing the cross sectional area of the magnetic core based on the peak value of the output current ripple, and further constructing a magnetic core volume model and a winding volume model; taking the total volume of the magnetic coupling energy storage element as a target function, solving an optimal coupling coefficient under different duty ratios, matching a magnetic core material and an air gap length according to the optimal coupling coefficient, selecting a magnetic core cross section area according to the maximum flux density of the magnetic core material, and obtaining structural parameters of the magnetic coupling energy storage element; according to the invention, the size of the magnetic coupling energy storage element is reduced to the maximum extent, and the power density of the converter is increased.

Description

Technical Field

[0001] This application belongs to the field of optimal design of power electronic devices, and more specifically, relates to a magnetic coupling energy storage element under a high duty cycle and a obtaining method thereof. Background Art

[0002] The design of non-isolated buck DC-DC power supplies pursues technical indicators such as high power density, high efficiency, and high voltage conversion ratio. The switched-capacitor topology has become a research hotspot due to its advantages such as low switching loss, high energy density, and high conversion ratio. However, the traditional switched-capacitor topology has significant defects when the duty cycle exceeds 0.5; the inductor current balancing mechanism fails, and the voltage conversion ratio deviates from the theoretical value to ..., resulting in the deterioration of the output characteristics. Recent research has proposed to restore current balance and maintain a conversion ratio of D / 2 by an asymmetric modulation method (fixing the duty cycle of one phase at 0.5 and adjusting the duty cycle of the other phase to be above 0.5 (D)). In addition, as an element with low energy density in a power converter, the volume of the inductor directly affects the compactness of the system. In the prior art, although magnetic coupling energy storage elements are widely used in multi-phase interleaved topologies to reduce current ripple, their design methods have the following limitations: 1. Lack of volume optimization: The currently proposed magnetic coupling energy storage elements mainly focus on suppressing current ripple or optimizing transient response, and do not establish a quantitative correlation model between the core and winding volumes, making it difficult to achieve the goal of minimizing volume.

[0003] 2. Insufficient parameter coupling analysis: The traditional design method does not systematically analyze the combined influence of the coupling coefficient ( K ) and the duty cycle (D) on the volume of the magnetic coupling energy storage element. Although existing research has pointed out that an increase in the coupling coefficient can reduce the core volume, the synchronous increase in the winding volume has been ignored, resulting in one-sided conclusions.

[0004] 3. Poor adaptability to high duty cycle scenarios: Existing research mostly targets the conventional operating conditions of ordinary converters, lacking targeted design for the scenario of D > 0.5 under asymmetric modulation, resulting in the volume of the magnetic coupling energy storage element being unable to adapt to the high conversion ratio requirements.

[0005] 4. Low core utilization rate: The traditional core selection depends on empirical formulas and does not combine the magnetic flux distribution characteristics under asymmetric modulation, resulting in suboptimal matching of the cross-sectional area and magnetic path length. Summary of the Invention

[0006] Aiming at the defects of the prior art, the purpose of this application is to provide a magnetic coupling energy storage element under a high duty cycle and a obtaining method thereof, aiming to solve the problem that the traditional design method does not systematically analyze the combined influence of the coupling coefficient ( K ) and the duty cycle (D) on the volume of the magnetic coupling energy storage element, making it difficult to achieve the goal of minimizing volume.

[0007] To achieve the above object, in a first aspect, the present application provides a method for obtaining a magnetic coupling energy storage element under a high duty cycle, including the following steps: Step S1: Establish an output current ripple model; wherein, the output current ripple model describes the peak-to-peak value of the output current ripple through the duty cycle of the switched capacitor converter, the coupling coefficient, the output voltage, the self-inductance of the winding, and the switching frequency; wherein, the magnetic coupling energy storage element is applied to the switched capacitor converter. Step S2: Based on the peak-to-peak value of the output current ripple in Step S1, represent the cross-sectional area of the magnetic core, and then construct a magnetic core volume model and a winding volume model. Step S3: Take the total volume of the magnetic coupling energy storage element as the objective function, solve for the optimal coupling coefficient under different duty cycles, then match the magnetic core material and the air gap length according to the optimal coupling coefficient, and select the cross-sectional area of the magnetic core according to the maximum magnetic flux density of the magnetic core material to obtain the structural parameters of the magnetic coupling energy storage element. Wherein, the total volume of the magnetic coupling energy storage element is the sum of the magnetic core volume and the winding volume.

[0008] Further preferably, Step S1 specifically includes the following steps: Step S1.1: Decouple the voltage equation of the magnetic coupling energy storage element into independent equations, and respectively obtain the equivalent inductance values of each working stage of the switched capacitor converter. Step S1.2: According to the periodic change law of the inductor current in the steady state, divide the working stages of the switched capacitor converter. Step S1.3: According to the relationship between the equivalent inductance and the self-inductance of the winding in each working stage, calculate the rising and falling slopes of the inductor current in each working stage, and obtain the expression of the peak-to-peak value of the output current ripple.

[0009] Further preferably, the method for establishing the magnetic core volume model includes the following steps: Construct an expression of the maximum magnetic flux of the magnetic circuit according to the peak-to-peak value of the output current ripple obtained in Step S1, and then calculate the expression of the cross-sectional area of the magnetic core based on the maximum magnetic flux of the magnetic circuit and the maximum magnetic flux density that the ferromagnetic material can withstand. According to the symmetry of the magnetic core structure, quantify the magnetic core volume model as the product of the cross-sectional area of the magnetic core and the equivalent magnetic circuit length.

[0010] Further preferably, the method for establishing the winding volume model includes the following steps: Determine the cross-sectional area of the wire according to the output current of the converter and the maximum current density allowed by the wire. And obtain the average winding perimeter according to the cross-sectional area of the magnetic core and the winding geometry. And determine the expression of the number of winding turns based on the self-inductance of the winding, the equivalent magnetic circuit length, the equivalent relative permeability, and the cross-sectional area of the magnetic core. Construct a winding volume model based on the cross-sectional area of the wire, the average winding perimeter, and the number of winding turns.

[0011] Further preferably, in step S3, with the total volume of the magnetic coupling energy storage element as the objective function, the optimal coupling coefficient at different duty cycles is solved by the gradient descent method or the numerical iteration method.

[0012] Further preferably, the volume of the magnetic core in step S2 is:

[0013] Wherein, K is the coupling coefficient; is the current ripple coefficient, which is the peak-to-peak value of the current ripple divided by the DC component; represents the equivalent magnetic path length of the magnetic core; represents the output voltage of the converter; is the switching frequency; D is the duty cycle; is the self-inductance of the winding; The winding volume model in step S2 is:

[0014] Wherein, is the output current; is the maximum current density that the wire can withstand; is the permeability of free space; is the equivalent relative permeability of the entire magnetic path; represents the equivalent magnetic path length of the magnetic core; is the self-inductance of the winding; is the magnetic core shape factor; is the winding overlap factor.

[0015] Further preferably, the self-inductance of the winding in step S3 is:

[0016] The cross-sectional area of the magnetic core is:

[0017] Wherein, the coupling coefficient is , m is the ratio of the central magnetic column air gap length to the edge magnetic column air gap length; n is the ratio of the cross-sectional area of the central magnetic column to the cross-sectional area of the edge magnetic column; is the current ripple coefficient, which is the peak-to-peak value of the current ripple divided by the DC component; represents the cross-sectional area of the magnetic core; represents the equivalent magnetic path length of the magnetic core; represents the output voltage of the converter; is the switching frequency;N is the number of turns of the winding; is the permeability of free space; is the maximum magnetic induction intensity that the ferromagnetic material can withstand under unsaturated conditions; is the cross-sectional area of the edge magnetic column; D is the duty cycle.

[0018] In a second aspect, the present application provides a magnetic coupling energy storage element under a high duty cycle. The total volume of the magnetic coupling energy storage element is obtained through the acquisition method of the coupling energy storage element; the magnetic core adopts a symmetric structure, and the cross-sectional area of the central column is twice that of the side column; the winding adopts a multi-strand parallel winding or Litz wire structure; the air gap length is determined by the coupling coefficient and the equivalent magnetic permeability of the magnetic core material.

[0019] In a third aspect, the present application provides a two-phase switched-capacitor converter based on a magnetic coupling energy storage element, including: an input voltage source, a series capacitor, a two-phase magnetic coupling energy storage element, and a switching network; The series capacitor and the two-phase magnetic coupling energy storage element form a loop; the first switching network is located between the series capacitor and the two-phase magnetic coupling energy storage element; the input voltage source is connected in parallel to the series capacitor through the second switching network; The switching network adopts pulse modulation with a phase difference of 180°; the magnetic core in the magnetic coupling energy storage element adopts a symmetric structure, and the cross-sectional area of the central column is twice that of the side column; the winding adopts a multi-strand parallel winding or Litz wire structure; the air gap length is determined by the coupling coefficient and the equivalent magnetic permeability of the magnetic core material.

[0020] Further preferably, the duty cycle of the first-phase switching network is adjustable and greater than 0.5; the duty cycle of the second-phase switching network is fixed at 0.5.

[0021] Generally speaking, compared with the prior art through the above technical solutions conceived by the present application, the following beneficial effects are achieved: The present application provides a magnetic coupling energy storage element under a high duty cycle of a switched capacitor, establishes a quantitative correlation model between the volume of the magnetic core and the winding, establishes an equivalent inductance expression of the switched capacitor, quantitatively describes the output current fluctuation, and gives an optimization method based on the model, which maximally reduces the volume of the magnetic coupling energy storage element by 30% and increases the power density of the converter.

[0022] The present application provides a method for obtaining a magnetic coupling energy storage element under a high duty cycle of a switched capacitor. By establishing a system of nonlinear equations and iteratively solving the structural parameters of the magnetic coupling energy storage element, a guiding method for obtaining the magnetic coupling energy storage element is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the circuit topology diagram of the magnetic coupling energy storage element of the switched-capacitor converter provided by the embodiment of the present application; Figure 2 is the voltage and current waveform diagram of the switched-capacitor converter provided by the embodiment of the present application; Figure 3 is the structural diagram of the magnetic coupling energy storage element provided by the embodiment of the present application; Figure 4 is the current simulation result of the switched-capacitor converter under magnetic coupling energy storage elements with different coupling coefficients. Detailed implementation manners

[0024] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0025] The term "and / or" in the present application is an association relationship describing associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. The symbol " / " in the present application represents an "or" relationship between associated objects. For example, A / B represents A or B.

[0026] The terms "first" and "second" etc. in the description and claims of the present application are used to distinguish different objects, rather than to describe a specific order of the objects.

[0027] In the embodiments of the present application, words such as "exemplary" or "for example" are used to represent examples, illustrations or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the embodiments of the present application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of words such as "exemplary" or "for example" is intended to present relevant concepts in a specific manner.

[0028] In the description of the embodiments of the present application, unless otherwise specified, the meaning of "a plurality of" refers to two or more.

[0029] The embodiments of the present application will be described below with reference to the accompanying drawings in the embodiments of the present application.

[0030] The present application provides a method for obtaining a magnetic coupling energy storage element under a high duty cycle, including the following steps: Establish an equivalent parameter calculation model of the magnetic coupling energy storage element. The equivalent parameter calculation model quantifies the volume of the magnetic coupling energy storage element as a function of the coupling coefficient ( K ), and the duty cycle ( D ). The volume includes the ferromagnetic core size and the copper winding geometric parameters; According to the topological structure of the open capacitor converter, different duty cycles ( The equivalent inductance during each of the following working stages ( ), and the current ripple ( ); Based on the equivalent inductance and current ripple models, construct the magnetic core volume model and winding volume model of the magnetic coupling energy storage element, and use the total volume of the magnetic coupling energy storage element, which is the sum of the magnetic core volume and the winding volume, as the objective function; Solve the objective function through an optimization algorithm to determine the optimal coupling coefficient ( D ) at a specific duty cycle ( ), so as to minimize the total volume of the magnetic coupling energy storage element; Obtain the structural parameters of the magnetic coupling energy storage element according to the optimal coupling coefficient ( ), including the geometric dimensions of the magnetic core, the number of winding turns, and the air gap length.

[0031] Further preferably, the method for obtaining the equivalent inductance includes the following steps: Decouple the voltage equation of the magnetic coupling energy storage element into independent equations to obtain the equivalent inductance values ( , , , , , ) during each working stage (A, B, C); Further preferably, the method for establishing the current ripple model includes the following steps: According to the periodic change law of the inductor current in the steady state, divide the working stages (A - B - A - C); Calculate the rising and falling slopes of the inductor current in each stage, and derive the expressions of the peak current ripple ( , ).

[0032] Further preferably, the method for establishing the magnetic core volume model includes the following steps: Based on the magnetic flux density ( ) and the equivalent magnetic path length ( ), calculate the cross-sectional area of the magnetic core ( ); According to the symmetry of the magnetic core structure (EI / EE type), quantify the magnetic core volume ( ) as the product of the cross-sectional area and the equivalent magnetic path length.

[0033] Further preferably, the method for establishing the winding volume model includes the following steps: According to the self-inductance of the winding ( ), the maximum current density ( ), and the winding geometry, derive the cross-sectional area of the copper wire ( ) and the average winding perimeter; By the correlation between the number of turns ( N ), calculate the total winding volume ( ).

[0034] Further preferably, the optimization method specifically includes the following steps: Define the objective function as the total volume of the magnetic coupling energy storage element ( ); Solve the minimum point of the objective function by the gradient descent method or the numerical iteration method to determine the optimal coupling coefficient ( ); Verify the continuity and volume reduction effect when the duty cycle ( D ) changes.

[0035] The present application provides a magnetic coupling energy storage element applied to a bi-phase switched capacitor converter under a high duty cycle, including: an input voltage source ( ), a series capacitor ( C ), a bi-phase magnetic coupling energy storage element ( , ) and a switching network (S1, S2); The switching network adopts pulse control with a phase difference of 180°, where the duty cycle of is fixed at 0.5, the duty cycle of is adjustable ( D > 0.5).

[0036] Among them, the magnetic core in the magnetic coupling energy storage element adopts a symmetric structure (EI / EE type), and the cross-sectional area of the central column is twice that of the side column; the winding adopts a multi-strand parallel winding or a Litz wire structure to reduce high-frequency losses; the air gap lengths ( , ) are determined by matching and optimizing the coupling coefficient ( K ) with the equivalent magnetic permeability ( ) of the magnetic core material.

[0037] Embodiment The present application provides a method for obtaining a magnetic coupling energy storage element, including the following steps: Step S1: Establish an equivalent parameter calculation model and an output current ripple model; as shown in the magnetic coupling energy storage element applied to the output position of the switched capacitor converter in Figure 1 ; Specifically, the equivalent parameter calculation model of the magnetic coupling energy storage element is to represent the relationship between the equivalent inductance and the self-inductance of the winding through the duty cycle D of the converter and the coupling coefficient K of the magnetic coupling energy storage element in different working stages of the converter; the output current ripple model is through the duty cycle D , coupling coefficientK Output voltage V out Winding self - inductance L s And switching frequency f sw , to describe the peak - to - peak value of the output current ripple.

[0038] Furthermore, when establishing the model, the leakage inductance of the magnetic - coupled energy - storage element, the stray parameters of the circuit, the circuit impedance, and the withstand voltage, etc. should be ignored.

[0039] Specifically, the voltage of the magnetic - coupled energy - storage element is related to the current change rate passing through the magnetic - coupled energy - storage element: (1) Wherein, represents the voltage across the first inductor ; represents the voltage across the second inductor , in volts; represents the current flowing through the first inductor ; represents the current flowing through the second inductor , in amperes; represents the self - inductance of the first winding; represents the self - inductance of the second winding; M represents the first inductor and the second inductor mutual inductance between them, in henries; According to the switch - on state, the converter can be divided into three operating states: A, B, and C, and it satisfies the periodicity of A - B - A - C; the current - voltage waveforms of the specific operating states of the switched capacitor can be seen in Figure 2 as shown; Specifically, when the first switch S1 and the second switch S2 are turned on simultaneously, it is defined as state A, and in state A and satisfy the following relationship: (2) Wherein, represents the input voltage of the converter, represents the output voltage of the converter; represents the capacitor voltage, in volts; Furthermore, assuming that the parameters such as the self - inductance and the number of turns of the first winding and the second winding are the same, substituting formula (2) into formula (1) can obtain and the equivalent inductance in state A: (3) Wherein, is the self-inductance of the first winding and the second winding, with the unit of Henry; Further, when the switch S1 is turned off and the switch S2 is turned on, it is defined as the B state; when the switch S2 is turned off and the switch S1 is turned on, it is defined as the C state. Then, in the B and C states , and its equivalent inductance satisfy the relationship: (4) (5) More specifically, the durations of the three states A, B, and C are: (6) Wherein, is the self-inductance of the first winding and the second winding; K is the coupling coefficient; D is the duty cycle; , , and , , are respectively the equivalent inductances of and in the three states A, B, and C; Further, it can be deduced that the inductor and output current ripple: (7) (8) Wherein, is the output voltage, is the switching frequency; and are respectively and output current peak-to-peak values; Step S2: Determine the core volume and the winding volume ; The volume of the magnetic coupling energy storage element consists of two parts: the core and the coil; The core shape is an EE / EI type core with a symmetrical structure, and the structure is as shown in Figure 3 ; the core volume is equal to the cross-sectional area multiplied by the magnetic path length: (9) Wherein, represents the core cross-sectional area, with the unit of square meter; represents the equivalent magnetic path length of the core, with the unit of meter; the core cross-sectional area is determined by the maximum magnetic flux of the magnetic path and the maximum magnetic density that the ferromagnetic material can withstand; Furthermore, the magnetic flux of the magnetic circuit is determined by the self-inductance, number of turns, mutual inductance of the magnetic coupling energy storage element, and the current flowing through it: (10) Combining the model formulas (7) and (8) established in Embodiment 1, the Φ 1. Φ 2 maximum value in the magnetic circuit: (11) (12) Even further, the cross-sectional area of the magnetic core is: (13) Where is the maximum magnetic induction intensity that the ferromagnetic material can withstand under unsaturated conditions, with the unit of tesla; is the current ripple coefficient, defined as the peak-to-peak value of the current ripple divided by the DC component, dimensionless; Even further, the volume of the magnetic core is expressed as formula (14), with the unit of cubic meters; (14) Where is the equivalent magnetic circuit length; The volume of the copper wire winding is equal to the cross-sectional area of the copper wire multiplied by the length of the copper wire winding, expressed as: (15) Where is the average radius of the winding, with the unit of meter; is the cross-sectional area of the copper wire, with the unit of square meter; N is the number of turns of the winding, dimensionless; Even further, the solenoid inductance is: (16) Where is the permeability of free space, with the unit of henry per meter; is the equivalent relative permeability of the entire magnetic core, dimensionless; Assuming that the cross-sectional area of the magnetic core is circular, it is approximately ; Even further, the cross-sectional area of the wire depends on the maximum current density that the wire can withstand and the current flowing through the wire: (17) Where is the maximum current density that the copper wire can withstand, with the unit of ampere per square meter; Substituting formula (16) and formula (17) into formula (15), the volume of the copper wire winding of the magnetic coupling energy storage element can be obtained as: (18) in, is the output current; The maximum current density that the wire can withstand; is the vacuum permeability; is the equivalent relative permeability of the entire magnetic circuit; The core shape factor is used to correct when the core cross section is not circular. When the cross section is square, the coefficient is taken , dimensionless; The winding overlap coefficient, when the winding overlaps, the equivalent radius increases, usually around 1.4, dimensionless; Furthermore, the volume of the magnetic coupling energy storage element is equal to: (19) More specifically, in the process of solving the optimal volume of the magnetic coupling energy storage element, a gradient descent method or a numerical iteration method is used to solve the minimum point of the objective function; The inductor parameters are designed under the following parameters: input voltage 6V, output voltage 1.8V, output current 5A, current ripple (ratio of output current peak-to-peak value to DC component) 0.3, switching frequency 50kHz; simulation waveform is shown in Figure 4 ; Figure 4 From top to bottom, the coupling coefficients are -0.8, -0.95, and 0, respectively; the corresponding self-inductances are 48.9μH, 168μH, and 24μH, respectively. The left side shows the initial to stable waveform, and the right side shows the amplified waveform. The ripple factor is stable at 0.3.

[0040] Step S3: The total volume of the magnetic coupling energy storage element ( ) is the objective function, and the numerical iteration method is used to solve the different duty cycles ( ) under the optimal coupling coefficient ( ); according to Matching core material and air gap length ( , ), optimize the number of winding turns ( N ) and layout to suppress high-frequency losses; select the core cross-sectional area based on the maximum flux density of the core material; and impose constraints based on the established nonlinear equations;

[0041]

[0042]

[0043] Iteratively solve the structural parameters of the magnetic coupling energy storage element.

[0044] More specifically, to obtain the magnetic coupling energy storage element, it is necessary to determine the cross-sectional area of the magnetic core, the number of winding turns, the air gap length of the edge magnetic column, and the air gap length of the central magnetic column; Specifically, the EE / EI type inductor structure has the characteristic that the cross-sectional area of the central magnetic column is larger than that of the edge magnetic columns; Specifically, for symmetry considerations, the cross-sectional areas and air gaps of the edge magnetic columns should be equal; Specifically, the coupling coefficient of the magnetic coupling energy storage element is adjusted by adjusting the air gap length of the central magnetic column; The self-inductance can be expressed as: (20) where m is the ratio of the air gap length of the central magnetic column to the air gap length of the edge magnetic column, , dimensionless; n is the ratio of the cross-sectional area of the central magnetic column to the cross-sectional area of the edge magnetic columns, , dimensionless; Furthermore, the coupling coefficient is expressed as: (21) Combining formulas (13), (20), and (21), the non-linear equations can be iteratively solved to obtain the structural parameters of the magnetic coupling energy storage element at the minimum volume.

[0045] The finite element simulation results show that the volume of the magnetic coupling energy storage element is reduced by 30% compared to the non-coupled case near the optimal coupling coefficient .

[0046] Compared with the prior art, the present application has the following advantages: The present application provides a magnetic coupling energy storage element under a high duty cycle of a switched capacitor, establishes a quantitative correlation model between the volume of the magnetic core and the winding, establishes an equivalent inductance expression of the switched capacitor, quantitatively describes the output current fluctuation, and gives an optimization method based on the model, which minimizes the volume of the magnetic coupling energy storage element by 30% and increases the power density of the converter.

[0047] The present application provides a method for obtaining a magnetic coupling energy storage element under a high duty cycle. By establishing non-linear equations and iteratively solving the structural parameters of the magnetic coupling energy storage element, it provides a guiding method for obtaining the magnetic coupling energy storage element.

[0048] It should be understood that expressions such as "including" and "may include" that can be used in this application indicate the existence of disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "including" and / or "having" can be interpreted as indicating a specific characteristic, number, operation, constituent element, component, or a combination thereof, but cannot be interpreted as excluding the existence or possibility of addition of one or more other characteristics, numbers, operations, constituent elements, components, or a combination thereof.

[0049] In addition, in this application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" can include A, can include B, or can include both A and B.

[0050] In the description of the embodiments of this application, it should be noted that unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. Among them, "fixed connection" means that they are connected to each other and the relative positional relationship after connection remains unchanged. "Rotational connection" means that they are connected to each other and can rotate relative to each other after connection. "Sliding connection" means that they are connected to each other and can slide relative to each other after connection. The orientation terms mentioned in the embodiments of this application, such as "top", "bottom", "inside", "outside", "left", "right", etc., are only with reference to the direction of the accompanying drawings. Therefore, the orientation terms used are for better and clearer illustration and understanding of the embodiments of this application, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the embodiments of this application.

[0051] In addition, in the embodiments of this application, mathematical concepts such as symmetry, equality, parallelism, and perpendicularity are mentioned. These limitations are all in view of the current technological level, rather than absolute strict definitions in the mathematical sense. A small deviation is allowed, and being approximately symmetric, approximately equal, approximately parallel, approximately perpendicular, etc. are all acceptable. For example, A is parallel to B means that A is parallel to B or approximately parallel to B, and the included angle between A and B can be between 0 degrees and 10 degrees. A is perpendicular to B means that A is perpendicular to B or approximately perpendicular to B, and the included angle between A and B can be between 80 degrees and 100 degrees.

[0052] The above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed by this application can easily think of changes or substitutions, which should all be covered within the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claimed rights.

Claims

1. A method for obtaining a magnetic coupling energy storage element under a high duty cycle, characterized in that It includes the following steps: Step S1: Establish an output current ripple model; wherein, the output current ripple model describes the peak-to-peak value of the output current ripple through the duty ratio of the switched-capacitor converter, the coupling coefficient, the output voltage, the self-inductance of the winding, and the switching frequency; wherein, the magnetic coupling energy storage element is applied to the switched-capacitor converter; Step S2: Based on the peak-to-peak value of the output current ripple in Step S1, represent the cross-sectional area of the magnetic core, and then construct a magnetic core volume model and a winding volume model; Step S3: Take the total volume of the magnetic coupling energy storage element as the objective function, solve for the optimal coupling coefficient under different duty ratios, then match the magnetic core material and the air gap length according to the optimal coupling coefficient, and select the cross-sectional area of the magnetic core according to the maximum magnetic flux density of the magnetic core material to obtain the structural parameters of the magnetic coupling energy storage element; Wherein, the total volume of the magnetic coupling energy storage element is the sum of the magnetic core volume and the winding volume.

2. The obtaining method according to claim 1, wherein Step S1 specifically includes the following steps: Step S1.1: Decouple the voltage equation of the magnetic coupling energy storage element into independent equations, and respectively obtain the equivalent inductance values of each working stage of the switched-capacitor converter; Step S1.2: Divide the working stages of the switched-capacitor converter according to the periodic change law of the inductor current in the steady state; Step S1.3: According to the relationship between the equivalent inductance and the self-inductance of the winding in each working stage, calculate the rising and falling slopes of the inductor current in each working stage, and obtain the expression of the peak-to-peak value of the output current ripple.

3. The acquisition method according to claim 1 or 2, characterized in that The method for establishing the magnetic core volume model includes the following steps: Construct an expression for the maximum magnetic flux of the magnetic circuit according to the peak-to-peak value of the output current ripple obtained in Step S1, and then calculate the expression for the cross-sectional area of the magnetic core based on the maximum magnetic flux of the magnetic circuit and the maximum magnetic flux density that the ferromagnetic material can withstand; According to the symmetry of the magnetic core structure, quantify the magnetic core volume model as the product of the cross-sectional area of the magnetic core and the equivalent magnetic circuit length.

4. The acquisition method according to claim 1 or 2, characterized in that The method for establishing the winding volume model includes the following steps: Determine the cross-sectional area of the wire according to the output current of the converter and the maximum current density allowed to pass through the wire; And obtain the average winding perimeter according to the cross-sectional area of the magnetic core and the winding geometry; And determine the expression for the number of winding turns based on the self-inductance of the winding, the equivalent magnetic circuit length, the equivalent relative permeability, and the cross-sectional area of the magnetic core; Construct a winding volume model according to the cross-sectional area of the wire, the average winding perimeter, and the number of winding turns.

5. The acquisition method according to claim 1, wherein In Step S3, take the total volume of the magnetic coupling energy storage element as the objective function, and solve for the optimal coupling coefficient under different duty ratios by the gradient descent method or the numerical iteration method.

6. The obtaining method according to claim 1, wherein The magnetic core volume in Step S2 is: Among them, K is the coupling coefficient; is the current ripple coefficient, which is the peak-to-peak value of the current ripple divided by the DC component; represents the equivalent magnetic path length of the magnetic core; represents the output voltage of the converter; is the switching frequency; D is the duty cycle; is the self-inductance of the winding; The winding volume model in Step S2 is: Among them, is the output current; is the maximum current density that the wire can withstand; is the vacuum permeability; is the equivalent relative magnetic permeability of the entire magnetic circuit; represents the equivalent magnetic circuit length of the magnetic core; is the self-inductance of the winding; is the shape factor of the magnetic core; is the winding overlap factor.

7. The acquisition method according to claim 6, wherein The self-inductance of the winding in Step S3 is: The cross-sectional area of the magnetic core is: Among them, the coupling coefficient is , m is the ratio of the air-gap length of the central magnetic column to the air-gap length of the edge magnetic column; n is the ratio of the cross-sectional area of the central magnetic column to the cross-sectional area of the edge magnetic column; is the current ripple coefficient, which is the ratio of the peak-to-peak value of the current ripple to the DC component; represents the cross-sectional area of the magnetic core; represents the equivalent magnetic path length of the magnetic core; represents the output voltage of the converter; is the switching frequency; N is the number of turns of the winding; is the permeability of free space; is the maximum magnetic induction intensity that the ferromagnetic material can withstand under the unsaturated condition; is the cross-sectional area of the edge magnetic column; D is the duty cycle.

8. A magnetic coupling energy storage element under a high duty cycle, characterized in that The total volume of the magnetic coupling energy storage element is obtained by the acquisition method of the magnetic coupling energy storage element according to any one of claims 1 to 7; the magnetic core adopts a symmetric structure, and the cross-sectional area of the central column is twice that of the side column; the winding adopts a multi-strand parallel winding or a Litz wire structure; the air gap length is determined by the coupling coefficient and the equivalent magnetic permeability of the magnetic core material.

9. A two-phase switched-capacitor converter based on the magnetic-coupling energy storage element according to any one of claims 1 to 7, characterized in that, It includes: An input voltage source, a series capacitor, a two-phase magnetic coupling energy storage element, and a switching network; The series capacitor and the two-phase magnetic coupling energy storage element form a loop; the first switching network is located between the series capacitor and the two-phase magnetic coupling energy storage element; the input voltage source is connected in parallel to the series capacitor through the second switching network; The switching network uses pulse modulation with a phase difference of 180°; the magnetic core in the magnetic coupling energy storage element adopts a symmetric structure, and the cross-sectional area of the central column is twice that of the side columns; the winding adopts a multi-strand parallel winding or Litz wire structure; the air gap length is determined by the coupling coefficient and the equivalent magnetic permeability of the magnetic core material.

10. The dual-phase switched-capacitor converter according to claim 8, wherein, The duty cycle of the first-phase switching network is adjustable and greater than 0.5; the duty cycle of the second-phase switching network is fixed at 0.5.

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