Method and system for calculating loss of circular litz wire winding of CLLC resonant circuit

Abstract

The invention discloses a CLLC resonance circuit circular litz wire winding loss calculation method and system, and the method comprises the steps: constructing a litz wire internal magnetic field intensity model, and determining a polar coordinate expression of the circular litz wire magnetic field intensity according to the litz wire internal magnetic field intensity model; determining a primary side current effective value and a secondary side current effective value of the CLLC resonance circuit; a proximity effect loss expression is determined, and according to the polar coordinate expression, the primary side current effective value, the secondary side current effective value and the proximity effect loss expression, a proximity effect loss value of the primary side and the secondary side of the CLLC resonance circuit is obtained through calculation; and determining a skin effect loss expression, and calculating the skin effect loss value of the primary side and the secondary side of the CLLC resonant circuit according to the polar coordinate expression, the primary side current effective value, the secondary side current effective value and the skin effect loss expression. The method improves the accuracy of loss calculation of the circular litz wire winding of the CLLC resonance circuit, and can be applied to the technical field of circuit measurement.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit measurement, and in particular to a method and system for calculating the loss of a circular litz wire winding of a CLLC resonant circuit. Background Art

[0002] As an isolated bidirectional DC-DC converter that operates at high frequency and has high power density, the CLLC resonant circuit is widely considered to be a potential topology in bidirectional power conversion technology due to its excellent soft switching capability. The converter has a wide range of applications, covering many important areas such as uninterruptible power supply systems, DC distribution networks, and interconnection systems between electric vehicles and power grids.

[0003] With the advancement of power electronic control technology and the continuous improvement of semiconductor and magnetic material performance, the operating frequency of the converter has increased significantly. This frequency increase leads to an increase in the winding loss of the transformer at high operating frequency, mainly due to the enhancement of skin effect and proximity effect, which in turn causes problems such as rising temperature inside the component and reduced energy conversion efficiency. In order to effectively reduce the winding loss of high-frequency transformers, it is usually chosen to use high-frequency windings with better performance, such as Litz wire, for improvement.

[0004] There are three main analytical models for the high-frequency winding loss of Litz wire: the improved Dowell model, the Ferreira model, and the modified Tourkhani model. Initially, the Dowell model was derived based on the assumption that the long copper foil winding has an ideal one-dimensional magnetic field distribution. Some researchers improved the Dowell model by treating the Litz wire winding as a copper foil winding through the area equivalence principle, but Ferreira pointed out that this simplified method has physical deficiencies, resulting in large calculation errors. Therefore, Ferreira proposed a two-dimensional loss calculation model for circular Litz wire, but the model did not consider the interaction between conductors in the same layer, and there may be large errors when the windings are closely arranged. To solve this problem, Tourkhani equivalentized the Litz wire to a circular real wire with the same diameter, and proposed a loss calculation model that fully considered the internal structure. However, Tourkhani's derivation was wrong, and no accurate analytical expression for the magnetic field was given, resulting in errors in the final model. Liu Ren discovered and pointed out this problem in 2023, and provided the correct derivation process and results. However, the maximum error of the modified Tourkhani model is 11.25%, and there are still some problems. In actual engineering, considering the insulation requirements, the transformer winding height is generally smaller than the core window height. At this time, there will be an obvious end effect at the winding end, which makes it difficult to accurately calculate the additional loss caused by the proximity effect.

[0005] The above problems need to be solved urgently.

[0006] Terminology explanation:

[0007] CLLC resonant circuit: is a power electronic converter, usually used for efficient energy transmission. It uses resonant inductors and resonant capacitors to achieve efficient power transmission by adjusting the resonant frequency of current and voltage.

[0008] Winding loss: refers to the energy loss caused by the heat generated by the current in the coil winding passing through the conductor in a transformer or inductor. It mainly includes DC resistance loss and the loss caused by skin effect and proximity effect under high frequency conditions.

[0009] Skin effect: Under high-frequency current, the current tends to flow on the surface of the conductor rather than the entire cross-section of the conductor, resulting in a reduction in the effective conductor area, an increase in the equivalent resistance of the conductor, and thus an increase in loss.

[0010] Proximity effect: When multiple conductors are close to each other, the current in one conductor will generate a magnetic field, which affects the current distribution in the adjacent conductors, causing the current to concentrate on the nearby surface parts, thereby increasing the loss of the conductor.

[0011] Litz wire: A wire that is made up of many insulated thin wires woven or arranged in parallel, designed to reduce winding losses caused by skin effect and proximity effect. Summary of the invention

[0012] The purpose of the present invention is to solve one of the technical problems existing in the prior art to at least a certain extent.

[0013] To this end, an object of an embodiment of the present invention is to provide a method for calculating the loss of a circular Litz wire winding of a CLLC resonant circuit, which improves the accuracy of calculating the loss of a circular Litz wire winding of a CLLC resonant circuit.

[0014] Another object of an embodiment of the present invention is to provide a system for calculating the loss of a circular Litz wire winding in a CLLC resonant circuit.

[0015] In order to achieve the above technical objectives, the technical solutions adopted by the embodiments of the present invention include:

[0016] In a first aspect, an embodiment of the present invention provides a method for calculating the loss of a circular Litz wire winding of a CLLC resonant circuit, comprising the following steps:

[0017] Constructing a model of the magnetic field strength inside the Litz wire, and determining a polar coordinate expression of the magnetic field strength of the circular Litz wire according to the model of the magnetic field strength inside the Litz wire;

[0018] Determine the effective value of the primary side current and the effective value of the secondary side current of the target CLLC resonant circuit;

[0019] Determine a proximity effect loss expression, and calculate the proximity effect loss values ​​of the primary and secondary sides of the target CLLC resonant circuit according to the polar coordinate expression, the primary side current effective value, the secondary side current effective value, and the proximity effect loss expression;

[0020] Determine a skin effect loss expression, and calculate the skin effect loss values ​​of the primary and secondary sides of the target CLLC resonant circuit according to the polar coordinate expression, the primary side current effective value, the secondary side current effective value, and the skin effect loss expression.

[0021] Furthermore, in one embodiment of the present invention, the magnetic field strength model inside the Litz wire is:

[0022] H=[H ext (Δx,k)+H int (r)cosθ]·e y -H int sinθ·e x

[0023]

[0024] Where H represents the magnetic field strength of each point inside the k-th layer of circular Litz wire, Δx represents the horizontal distance between each point inside the circular Litz wire winding and its leftmost point, r represents the distance between each point inside the circular Litz wire and the center of the circular Litz wire, θ represents the angle between the line segment connecting each point inside the circular Litz wire and the center of the circular Litz wire and the x-axis, e x represents the unit vector of the x-axis, e y represents the unit vector of the y-axis, h w represents the height of the circular Litz wire winding, n represents the number of turns of each layer of circular Litz wire winding, d Litz represents the diameter of the circular Litz wire winding, r Litz represents the radius of the circular Litz wire winding, and I represents the current amplitude passing through the circular Litz wire.

[0025] Further, in one embodiment of the present invention, the polar coordinate expression is:

[0026]

[0027] Here, H(r,θ) represents the polar coordinates of the magnetic field strength at a point (r,θ) inside the circular Litz wire.

[0028] Further, in one embodiment of the present invention, the effective value of the primary side current is determined by the following formula:

[0029]

[0030] The effective value of the secondary current is determined by the following formula:

[0031]

[0032] Among them, I Lr1,rms Indicates the effective value of the primary current, I Lr2.rms Represents the effective value of the secondary current, V o represents the output voltage of the target CLLC resonant circuit, N represents the transformer ratio, L m represents the excitation inductance, R0 represents the load resistance, f s Indicates the operating frequency of the circuit.

[0033] Furthermore, in one embodiment of the present invention, the proximity effect loss expression is:

[0034]

[0035] Among them, P proximity represents the proximity effect loss value, D represents the waveform duty cycle, B p represents the amplitude of the sinusoidal magnetic field, f represents the frequency of the magnetic field change, l represents the length of the circular Litz wire conductor, d represents the diameter of the circular Litz wire conductor, and σ represents the conductivity of the wire;

[0036] The skin effect loss expression is:

[0037]

[0038]

[0039] Among them, P skin represents the skin effect loss value, r represents the distance between each point inside the circular Litz wire and the center of the circular Litz wire, and θ represents the angle between the line segment connecting each point inside the circular Litz wire and the center of the circular Litz wire and the x-axis.

[0040] Furthermore, in one embodiment of the present invention, the proximity effect loss value is calculated by the following formula:

[0041]

[0042] Among them, P 1,proximity Represents the proximity effect loss value of the primary side of the target CLLC resonant circuit, P 2,proximity Represents the proximity effect loss value of the secondary side of the target CLLC resonant circuit, V o represents the output voltage of the target CLLC resonant circuit, N represents the transformer ratio, L m represents the excitation inductance, R0 represents the load resistance, f srepresents the circuit operating frequency, μ0 represents the vacuum permeability, h w represents the height of the circular Litz wire winding, n represents the number of turns of each layer of circular Litz wire winding, r Litz represents the radius of the circular Litz wire winding, and k represents the number of layers of the circular Litz wire.

[0043] Furthermore, in one embodiment of the present invention, the skin effect loss value is calculated by the following formula:

[0044]

[0045] Among them, P 1,skin Represents the skin effect loss value of the primary side of the target CLLC resonant circuit, P 2,skin Represents the skin effect loss value of the secondary side of the target CLLC resonant circuit, V o represents the output voltage of the target CLLC resonant circuit, N represents the transformer ratio, L m represents the excitation inductance, R0 represents the load resistance, f s Indicates the circuit operating frequency, h w represents the height of the circular Litz wire winding, n represents the number of turns of each layer of circular Litz wire winding, r Litz Indicates the radius of a circular Litz wire winding.

[0046] In a second aspect, an embodiment of the present invention provides a CLLC resonant circuit circular Litz wire winding loss calculation system, comprising:

[0047] A polar coordinate expression determination module is used to construct a Litz wire internal magnetic field strength model, and determine a polar coordinate expression of the circular Litz wire magnetic field strength according to the Litz wire internal magnetic field strength model;

[0048] A current effective value determination module, used to determine the primary side current effective value and the secondary side current effective value of the target CLLC resonant circuit;

[0049] A proximity effect loss value calculation module, used to determine a proximity effect loss expression, and calculate the proximity effect loss values ​​of the primary and secondary sides of the target CLLC resonant circuit according to the polar coordinate expression, the primary side current effective value, the secondary side current effective value and the proximity effect loss expression;

[0050] The skin effect loss value calculation module is used to determine the skin effect loss expression, and calculate the skin effect loss value of the primary and secondary sides of the target CLLC resonant circuit according to the polar coordinate expression, the primary side current effective value, the secondary side current effective value and the skin effect loss expression.

[0051] In a third aspect, an embodiment of the present invention provides a device for calculating the loss of a circular Litz wire winding of a CLLC resonant circuit, comprising:

[0052] at least one processor;

[0053] at least one memory for storing at least one program;

[0054] When the at least one program is executed by the at least one processor, the at least one processor implements the above-mentioned method for calculating the circular Litz wire winding loss of a CLLC resonant circuit.

[0055] In a fourth aspect, an embodiment of the present invention further provides a computer-readable storage medium, which stores a program executable by a processor, and the program executable by the processor is used to execute the above-mentioned method for calculating the loss of a circular Litz wire winding in a CLLC resonant circuit when executed by the processor.

[0056] The advantages and beneficial effects of the present invention will be partly given in the following description, partly become apparent from the following description, or be understood through the practice of the present invention:

[0057] The embodiment of the present invention constructs a model of the magnetic field strength inside the Litz wire, determines the polar coordinate expression of the magnetic field strength of the circular Litz wire according to the model of the magnetic field strength inside the Litz wire, determines the effective value of the primary current and the effective value of the secondary current of the target CLLC resonant circuit, determines the proximity effect loss expression, calculates the proximity effect loss value of the primary and secondary sides of the target CLLC resonant circuit according to the polar coordinate expression, the effective value of the primary current, the effective value of the secondary current and the proximity effect loss expression, determines the skin effect loss expression, calculates the skin effect loss value of the primary and secondary sides of the target CLLC resonant circuit according to the polar coordinate expression, the effective value of the primary current, the effective value of the secondary current and the skin effect loss expression. The embodiment of the present invention divides the CLLC high-frequency transformer winding loss into proximity effect loss and skin effect loss and calculates them separately, so that the additional loss caused by the end effect can be taken into account to a certain extent, thereby avoiding the loss calculation error caused by the end effect, and improving the accuracy of the calculation of the circular Litz wire winding loss of the CLLC resonant circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the technical solution in the embodiments of the present invention, the following introduction is made to the drawings required for use in the embodiments of the present invention. It should be understood that the drawings introduced below are only for the convenience of clearly describing some embodiments of the technical solution of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0059] Figure 1A flowchart of a method for calculating the loss of a circular Litz wire winding in a CLLC resonant circuit provided by an embodiment of the present invention;

[0060] Figure 2 Schematic diagram of the CLLC transformer structure and the distribution of the magnetic field inside its circular Litz wire winding;

[0061] Figure 3 It is the schematic diagram of CLLC resonant circuit;

[0062] Figure 4 It is a schematic diagram of the simplified forward fundamental wave equivalent circuit;

[0063] Figure 5 is a schematic diagram of the conductor cross section;

[0064] Figure 6 Schematic diagram of uniformly changing magnetic field;

[0065] Figure 7 This is the dimensioning diagram of the Maxwell simulation model of the CLLC high-frequency transformer;

[0066] Figure 8 It is a comparison chart of the calculated value, simulated value and measured value of the AC resistance of the CLLC transformer winding;

[0067] Fig. 9 A structural block diagram of a circular Litz wire winding loss calculation system for a CLLC resonant circuit provided by an embodiment of the present invention;

[0068] Fig.10 A structural block diagram of a circular Litz wire winding loss calculation device for a CLLC resonant circuit provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0069] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and are not to be construed as limitations of the present invention. For the step numbers in the following embodiments, they are only provided for the convenience of explanation, and the order between the steps is not limited in any way, and the execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0070] In the description of the present invention, the meaning of "a plurality" is two or more than two. If there is a description of "a first" or "a second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features. In addition, unless otherwise defined, all technical and scientific terms used in this document have the same meaning as those commonly understood by those skilled in the art.

[0071] Reference Figure 1 The embodiment of the present invention provides a method for calculating the loss of a circular Litz wire winding of a CLLC resonant circuit, which specifically includes the following steps:

[0072] S101. Construct a model of the magnetic field strength inside the Litz wire, and determine a polar coordinate expression of the magnetic field strength of the circular Litz wire according to the model of the magnetic field strength inside the Litz wire.

[0073] As an optional implementation, the magnetic field strength model inside the Litz wire is:

[0074] H=[H ext (Δx,k)+H int (r)cosθ]·e y -H int sinθ·e x

[0075]

[0076] Where H represents the magnetic field strength of each point inside the k-th layer of circular Litz wire, Δx represents the horizontal distance between each point inside the circular Litz wire winding and its leftmost point, r represents the distance between each point inside the circular Litz wire and the center of the circular Litz wire, θ represents the angle between the line segment connecting each point inside the circular Litz wire and the center of the circular Litz wire and the x-axis, e x represents the unit vector of the x-axis, e y represents the unit vector of the y-axis, h w represents the height of the circular Litz wire winding, n represents the number of turns of each layer of circular Litz wire winding, d Litz represents the diameter of the circular Litz wire winding, r Litz represents the radius of the circular Litz wire winding, and I represents the current amplitude passing through the circular Litz wire.

[0077] As an optional implementation, the polar coordinate expression is:

[0078]

[0079] Here, H(r,θ) represents the polar coordinates of the magnetic field strength at a point (r,θ) inside the circular Litz wire.

[0080] Specifically, before deriving the analytical model, it is assumed that each strand of the circular Litz wire is coated with insulating paint and isolated from each other, and each strand of the wire passes through each point of the cross section of the circular Litz wire continuously. Therefore, it can be assumed that the current of the circular Litz wire is evenly distributed on each strand of the wire, that is, the current of each strand of the wire is the same.

[0081] exist Figure 2 The magnetic field distribution of the circular Litz wire is shown in Figure 2. In addition to being affected by the magnetic field intensity Hext generated by the current in other windings, each point inside the winding is also affected by the magnetic field intensity Hint generated by the current in other strands inside. Among them, Hext can be considered as a one-dimensional distribution along the y-axis, that is, the magnetic core guides the leakage magnetic field to be distributed along the axial direction.

[0082] The magnetic field intensity H at each point inside the k-th circular Litz wire is expressed as:

[0083]

[0084] Where: θ represents the angle between the line segment connecting each point and the center of the circular Litz wire and the x-axis. The direction of H is the tangent direction of the circle with radius r passing through each point. ext and H int Respectively and In formula (1), H ext and H int They can be expressed as formulas (2) and (3) respectively:

[0085]

[0086] Where: x is the horizontal distance from any point inside the circular Litz wire winding to its leftmost point; h w is the height of the circular Litz wire winding; n is the number of turns of each layer of circular Litz wire in the winding; d Litz 、r Litz are the diameter and radius of the circular Litz wire winding respectively; I is the current amplitude passing through the circular Litz wire. Using formulas (1), (2), and (3), the polar coordinate expression of the magnetic field intensity H at any point (r, θ) of the jth circular Litz wire conductor of the kth layer of the transformer can be obtained as follows:

[0087]

[0088] S102: Determine the effective value of the primary-side current and the effective value of the secondary-side current of the target CLLC resonant circuit.

[0089] As an optional implementation, the effective value of the primary current is determined by the following formula:

[0090]

[0091] The effective value of the secondary current is determined by the following formula:

[0092]

[0093] Among them, I Lr1,rms Indicates the effective value of the primary current, I Lr2.rms Represents the effective value of the secondary current, V o represents the output voltage of the target CLLC resonant circuit, N represents the transformer ratio, L m represents the excitation inductance, R0 represents the load resistance, f s Indicates the operating frequency of the circuit.

[0094] Specifically, Figure 3 , Figure 4 They are the schematic diagram of the CLLC resonant circuit and the simplified forward fundamental equivalent circuit, ignoring the dead zone mode and the three-element resonance mode (which occupy a very small proportion of time) when the CLLC is working. At this time, the primary current of the transformer is:

[0095]

[0096] In the formula, I Lr1,rms is i Lr1(t) The effective value of ω r =2πf r , f r is the first resonant frequency, φ is the phase difference relative to the input voltage, V o is the output voltage of the CLLC circuit.

[0097]

[0098]

[0099] According to formulas (5), (7), and (8), we can get I Lr1,rms as follows:

[0100]

[0101] Where N is the transformer ratio, L is m is the magnetizing inductance, and R0 is the load resistance.

[0102] The same method is used to obtain the transformer secondary current:

[0103]

[0104] S103, determining a proximity effect loss expression, and calculating the proximity effect loss values ​​of the primary and secondary sides of the target CLLC resonant circuit according to the polar coordinate expression, the effective value of the primary side current, the effective value of the secondary side current, and the proximity effect loss expression;

[0105] S104, determining a skin effect loss expression, and calculating the skin effect loss values ​​of the primary and secondary sides of the target CLLC resonant circuit according to the polar coordinate expression, the effective value of the primary side current, the effective value of the secondary side current, and the skin effect loss expression.

[0106] As an optional implementation, the proximity effect loss expression is:

[0107]

[0108] Among them, P proximity represents the proximity effect loss value, D represents the waveform duty cycle, B p represents the amplitude of the sinusoidal magnetic field, f represents the frequency of the magnetic field change, l represents the length of the circular Litz wire conductor, d represents the diameter of the circular Litz wire conductor, and σ represents the conductivity of the wire;

[0109] The skin effect loss expression is:

[0110]

[0111] Among them, P skin represents the skin effect loss value, r represents the distance between each point inside the circular Litz wire and the center of the circular Litz wire, and θ represents the angle between the line segment connecting each point inside the circular Litz wire and the center of the circular Litz wire and the x-axis.

[0112] As an optional implementation, the proximity effect loss value is calculated by the following formula:

[0113]

[0114]

[0115] Among them, P 1,proximity Represents the proximity effect loss value of the primary side of the target CLLC resonant circuit, P 2,proximity Represents the proximity effect loss value of the secondary side of the target CLLC resonant circuit, V o represents the output voltage of the target CLLC resonant circuit, N represents the transformer ratio, L m represents the excitation inductance, R0 represents the load resistance, f s represents the circuit operating frequency, μ0 represents the vacuum permeability, h w represents the height of the circular Litz wire winding, n represents the number of turns of each layer of circular Litz wire winding, r Litzrepresents the radius of the circular Litz wire winding, and k represents the number of layers of the circular Litz wire.

[0116] As an optional implementation, the skin effect loss value is calculated by the following formula:

[0117]

[0118] Among them, P 1,skin Represents the skin effect loss value of the primary side of the target CLLC resonant circuit, P 2,skin Represents the skin effect loss value of the secondary side of the target CLLC resonant circuit, V o represents the output voltage of the target CLLC resonant circuit, N represents the transformer ratio, L m represents the excitation inductance, R0 represents the load resistance, f s Indicates the operating frequency of the circuit, h w represents the height of the circular Litz wire winding, n represents the number of turns of each layer of circular Litz wire winding, r Litz Indicates the radius of a circular Litz wire winding.

[0119] Specifically, the relationship between the duty cycle and the proximity effect loss is first calculated.

[0120] When adjacent conductors are carrying high-frequency currents, each conductor is not only in the magnetic field generated by its own high-frequency current, but also in the magnetic field generated by the currents of other conductors. The change in the magnetic field of the currents of adjacent conductors will lead to the generation of induced electromotive force, which in turn causes eddy currents in the conductors, resulting in energy loss. This part of the loss is called proximity loss. When a cylindrical copper conductor with a diameter of d and a length of l is in an alternating magnetic field, assuming that the magnetic field is uniform and perpendicular to the conductor, the cross-section of the wire is as follows: Figure 5 shown.

[0121] At this time, the expression of proximity loss is as follows, where σ is the conductivity of the wire.

[0122]

[0123] At this time, the calculation of proximity effect loss depends on the waveform of the magnetic field. When the waveform of the magnetic field (other periodic waveforms are the same) is as follows Figure 4 As shown, the duty cycle can be used to calculate Figure 6 Taking the magnetic field waveform shown in FIG. 1 as an example, Ts is the magnetic field waveform period, and D is the waveform duty cycle, which is expressed as the ratio of the positive half cycle to the entire cycle. For a complete cycle, it can be divided into two time periods, 0-DT and DT-T, for calculation. Formula (11) can be used to obtain formulas (12) and (13).

[0124]

[0125] In the formula, B p is the amplitude of the sinusoidal magnetic field, and f is the frequency of the magnetic field change. Combining equations (12) and (13), the proximity effect loss expression can be obtained as follows:

[0126]

[0127] Combining formulas (4), (9), (10), and (14), the relationship between the proximity effect loss of the primary and secondary sides of the CLLC resonant circuit and the magnetic field duty cycle is obtained as follows:

[0128]

[0129] Where μ0 is the magnetic permeability of vacuum.

[0130] Next, calculate the loss caused by the skin effect.

[0131] When there is alternating current or an alternating electromagnetic field, the current distribution inside the conductor is uneven. The current is mainly concentrated in a thin layer on the surface of the conductor. Near the surface of the conductor, the current density is large, while inside the conductor the current is actually small. This will increase the resistance of the conductor and increase the power loss. This part of the loss is called skin loss. The polar coordinate relationship between the current density and the magnetic field strength in the conductor is shown in formula (19).

[0132]

[0133] By integrating the current density over the conductor, we can get the formula for skin effect loss per unit length:

[0134]

[0135] Combining formulas (4), (9), (10), (19), and (20), the skin effect loss expression of the primary and secondary sides of the CLLC resonant circuit can be obtained as follows:

[0136]

[0137] The above is a description of the method steps of the embodiment of the present invention. The following is a further description of the embodiment of the present invention in combination with simulation experiments.

[0138] like Figure 7 The figure shows the dimension annotation diagram of the CLLC high-frequency transformer Maxwell simulation model, and the parameters of the CLLC high-frequency transformer used in the simulation are shown in Table 1. In order to verify the CLLC winding loss calculation model proposed in the present invention, a high-frequency wound transformer on a CLLC resonant circuit with a power of 100W is used as the test analysis object, and the bode100 vector network analyzer is used to measure its AC resistance, and Ansys Maxwell simulation is used for verification.

[0139] Table 1

[0140]

[0141] Before testing, the secondary side of the transformer is short-circuited to eliminate the influence of the magnetic core, and the bode100 vector network analyzer needs to be calibrated with open circuit, short circuit and load.

[0142] Comparison of calculated, simulated and measured AC resistance of circular Litz wire winding of CLLC resonant circuit transformer Figure 8 At the resonant frequency of 50.9kHz, the measured value of bode100 is 40.01mΩ, the simulated value of the model of the present invention is 36.41mΩ, and the simulated value of the modified Tourkhani model is 36.31mΩ. Figure 8 The following results can be obtained: ① For the CLLC resonant circuit test transformer, in the full frequency band, the model proposed by the present invention is closer to the experimental measurement value and the Maxwell simulation value than the modified Tourkhani model; ② For the CLLC resonant circuit test transformer, at the resonant frequency point, the error of the modified Tourkhani model is 9.25%, while that of the model of the present invention is 8.99%. In the range of 0 to 100 kHz, the maximum error of the modified Tourkhani model is 9.90%, while that of the model of the present invention is 9.10%.

[0143] In summary, after Ansys Maxwell simulation verification and building a high-frequency transformer AC resistance measurement platform, the measurement results were compared with the calculation results of the model of the present invention and the modified Tourkhani model. The results showed that the Litz wire winding loss model of the CLLC resonant circuit transformer proposed in the present invention can accurately calculate the Litz wire winding loss of the CLLC resonant circuit transformer, and realize the accurate prediction of the Litz wire winding loss of the CLLC resonant circuit transformer.

[0144] It is understandable that the embodiment of the present invention divides the CLLC high-frequency transformer winding loss into proximity effect loss and skin effect loss and calculates them separately, so that the additional loss caused by the end effect can be taken into account to a certain extent. The end effect is mainly manifested as the unevenness of the magnetic field distribution. When the end effect is obvious, if the total loss is calculated directly, it will lead to errors, because the calculation does not take into account the uneven magnetic field caused by the end effect; the embodiment of the present invention calculates these two effects separately, and can better consider the local changes of the magnetic field in each calculation process, and can analyze and process the end effect more carefully, thereby avoiding the loss calculation error caused by the end effect, and improving the accuracy of the calculation of the circular Litz wire winding loss of the CLLC resonant circuit.

[0145] Reference Fig. 9, an embodiment of the present invention provides a CLLC resonant circuit circular litz wire winding loss calculation system, comprising:

[0146] A polar coordinate expression determination module is used to construct a model of the magnetic field strength inside the Litz wire, and determine the polar coordinate expression of the magnetic field strength of the circular Litz wire according to the model of the magnetic field strength inside the Litz wire;

[0147] A current effective value determination module, used to determine the primary side current effective value and the secondary side current effective value of the target CLLC resonant circuit;

[0148] A proximity effect loss value calculation module is used to determine a proximity effect loss expression, and calculate the proximity effect loss values ​​of the primary and secondary sides of the target CLLC resonant circuit according to the polar coordinate expression, the effective value of the primary side current, the effective value of the secondary side current and the proximity effect loss expression;

[0149] The skin effect loss value calculation module is used to determine the skin effect loss expression, and calculate the skin effect loss value of the primary and secondary sides of the target CLLC resonant circuit based on the polar coordinate expression, the effective value of the primary side current, the effective value of the secondary side current and the skin effect loss expression.

[0150] The contents of the above method embodiments are all applicable to the present system embodiments. The functions specifically implemented by the present system embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0151] Reference Fig.10 The embodiment of the present invention provides a CLLC resonant circuit circular litz wire winding loss calculation device, comprising:

[0152] at least one processor;

[0153] at least one memory for storing at least one program;

[0154] When the at least one program is executed by the at least one processor, the at least one processor implements the method for calculating the loss of a circular Litz wire winding in a CLLC resonant circuit.

[0155] The contents of the above method embodiments are all applicable to the present device embodiments. The functions specifically implemented by the present device embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0156] An embodiment of the present invention also provides a computer-readable storage medium, which stores a program executable by a processor. When the program executable by the processor is executed by the processor, it is used to execute the above-mentioned method for calculating the loss of a circular Litz wire winding in a CLLC resonant circuit.

[0157] A computer-readable storage medium according to an embodiment of the present invention can execute a method for calculating the loss of a circular Litz wire winding in a CLLC resonant circuit provided by an embodiment of the method of the present invention, can execute any combination of implementation steps of the method embodiment, and has the corresponding functions and beneficial effects of the method.

[0158] The embodiment of the present invention also discloses a computer program product or a computer program, wherein the computer program product or the computer program includes computer instructions, and the computer instructions are stored in a computer-readable storage medium. A processor of a computer device can read the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, so that the computer device executes Figure 1 The method shown.

[0159] In some selectable embodiments, the function / operation mentioned in the block diagram may not occur in the order mentioned in the operation diagram. For example, depending on the function / operation involved, the two boxes shown in succession can actually be executed substantially simultaneously or the above-mentioned boxes can sometimes be executed in reverse order. In addition, the embodiment presented and described in the flow chart of the present invention is provided by way of example, for the purpose of providing a more comprehensive understanding of technology. The disclosed method is not limited to the operation and logic flow presented herein. Selectable embodiments are expected, wherein the order of various operations is changed and the sub-operation of a part for which is described as a larger operation is performed independently.

[0160] In addition, although the present invention is described in the context of functional modules, it should be understood that, unless otherwise specified to the contrary, one or more of the above-mentioned functions and / or features can be integrated into a single physical device and / or software module, or one or more functions and / or features can be implemented in a separate physical device or software module. It is also understood that a detailed discussion of the actual implementation of each module is unnecessary for understanding the present invention. More specifically, in view of the properties, functions and internal relationships of the various functional modules in the device disclosed herein, the actual implementation of the module will be understood within the conventional skills of the engineer. Therefore, those skilled in the art can implement the present invention set forth in the claims without excessive experimentation using ordinary techniques. It is also understood that the specific concepts disclosed are merely illustrative and are not intended to limit the scope of the present invention, which is determined by the full scope of the appended claims and their equivalents.

[0161] If the above functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the above methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0162] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0163] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and editable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the above-mentioned program is printed, since the above-mentioned program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or processing in other suitable ways as necessary, and then stored in a computer memory.

[0164] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0165] In the above description of this specification, the description with reference to the terms "one embodiment / example", "another embodiment / example" or "certain embodiments / examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0166] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

[0167] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the above embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A method for calculating the loss of a circular Litz wire winding in a CLLC resonant circuit, characterized in that: The following steps are involved: Constructing a model of the magnetic field strength inside the Litz wire, and determining a polar coordinate expression of the magnetic field strength of the circular Litz wire according to the model of the magnetic field strength inside the Litz wire; Determine the effective value of the primary side current and the effective value of the secondary side current of the target CLLC resonant circuit; Determine a proximity effect loss expression, and calculate the proximity effect loss values ​​of the primary and secondary sides of the target CLLC resonant circuit according to the polar coordinate expression, the primary side current effective value, the secondary side current effective value, and the proximity effect loss expression; Determine a skin effect loss expression, and calculate the skin effect loss values ​​of the primary and secondary sides of the target CLLC resonant circuit according to the polar coordinate expression, the primary side current effective value, the secondary side current effective value, and the skin effect loss expression.

2. A method for calculating the loss of a circular Litz wire winding of a CLLC resonant circuit according to claim 1, characterized in that: The magnetic field strength model inside the Litz wire is: H=[H ext (Δx,k)+H int (r)cosθ]·e y -H int sinθ·e x Where H represents the magnetic field strength of each point inside the k-th layer of circular Litz wire, Δx represents the horizontal distance between each point inside the circular Litz wire winding and its leftmost point, r represents the distance between each point inside the circular Litz wire and the center of the circular Litz wire, θ represents the angle between the line segment connecting each point inside the circular Litz wire and the center of the circular Litz wire and the x-axis, e x represents the unit vector of the x-axis, e y represents the unit vector of the y-axis, h w represents the height of the circular Litz wire winding, n represents the number of turns of each layer of circular Litz wire winding, d Litz represents the diameter of the circular Litz wire winding, r Litz represents the radius of the circular Litz wire winding, and I represents the current amplitude passing through the circular Litz wire.

3. A method for calculating the loss of a circular Litz wire winding of a CLLC resonant circuit according to claim 2, characterized in that: The polar coordinate expression is: Here, H(r,θ) represents the polar coordinates of the magnetic field strength at a point (r,θ) inside the circular Litz wire.

4. A method for calculating the loss of a circular Litz wire winding of a CLLC resonant circuit according to claim 1, characterized in that: The effective value of the primary current is determined by the following formula: The effective value of the secondary current is determined by the following formula: Among them, I Lr1,rms Indicates the effective value of the primary current, I Lr2.rms Represents the effective value of the secondary current, V o represents the output voltage of the target CLLC resonant circuit, N represents the transformer ratio, L m represents the excitation inductance, R0 represents the load resistance, f s Indicates the operating frequency of the circuit.

5. The method for calculating the loss of a circular Litz wire winding of a CLLC resonant circuit according to claim 1, characterized in that: The proximity effect loss expression is: Among them, P proximity represents the proximity effect loss value, D represents the waveform duty cycle, B p represents the amplitude of the sinusoidal magnetic field, f represents the frequency of the magnetic field change, l represents the length of the circular Litz wire conductor, d represents the diameter of the circular Litz wire conductor, and σ represents the conductivity of the wire; The skin effect loss expression is: Among them, P skin represents the skin effect loss value, r represents the distance between each point inside the circular Litz wire and the center of the circular Litz wire, and θ represents the angle between the line segment connecting each point inside the circular Litz wire and the center of the circular Litz wire and the x-axis.

6. A method for calculating the loss of a circular Litz wire winding in a CLLC resonant circuit according to claim 5, characterized in that: The proximity effect loss value is calculated by the following formula: Among them, P 1,proximity Represents the proximity effect loss value of the primary side of the target CLLC resonant circuit, P 2,proximity Represents the proximity effect loss value of the secondary side of the target CLLC resonant circuit, V o represents the output voltage of the target CLLC resonant circuit, N represents the transformer ratio, L m represents the excitation inductance, R0 represents the load resistance, f s represents the circuit operating frequency, μ0 represents the vacuum permeability, h w represents the height of the circular Litz wire winding, n represents the number of turns of each layer of circular Litz wire winding, r Litz represents the radius of the circular Litz wire winding, and k represents the number of layers of the circular Litz wire.

7. A method for calculating the loss of a circular Litz wire winding in a CLLC resonant circuit according to claim 5, characterized in that: The skin effect loss value is calculated by the following formula: Among them, P 1,skin Represents the skin effect loss value of the primary side of the target CLLC resonant circuit, P 2,skin Represents the skin effect loss value of the secondary side of the target CLLC resonant circuit, V o represents the output voltage of the target CLLC resonant circuit, N represents the transformer ratio, L m represents the excitation inductance, R0 represents the load resistance, f s Indicates the circuit operating frequency, h w represents the height of the circular Litz wire winding, n represents the number of turns of each layer of circular Litz wire winding, r Litz Indicates the radius of a circular Litz wire winding.

8. A CLLC resonant circuit circular Litz wire winding loss calculation system, characterized in that: include: A polar coordinate expression determination module is used to construct a Litz wire internal magnetic field strength model, and determine a polar coordinate expression of the circular Litz wire magnetic field strength according to the Litz wire internal magnetic field strength model; A current effective value determination module, used to determine the primary side current effective value and the secondary side current effective value of the target CLLC resonant circuit; A proximity effect loss value calculation module, used to determine a proximity effect loss expression, and calculate the proximity effect loss values ​​of the primary and secondary sides of the target CLLC resonant circuit according to the polar coordinate expression, the primary side current effective value, the secondary side current effective value and the proximity effect loss expression; The skin effect loss value calculation module is used to determine the skin effect loss expression, and calculate the skin effect loss value of the primary and secondary sides of the target CLLC resonant circuit according to the polar coordinate expression, the primary side current effective value, the secondary side current effective value and the skin effect loss expression.

9. A device for calculating the loss of a circular Litz wire winding in a CLLC resonant circuit, characterized in that: include: at least one processor; at least one memory for storing at least one program; When the at least one program is executed by the at least one processor, the at least one processor implements a method for calculating the loss of a circular Litz wire winding of a CLLC resonant circuit as described in any one of claims 1 to 7.

10. A computer-readable storage medium storing a program executable by a processor, characterized in that: The program executable by the processor is used to execute the method for calculating the loss of a circular Litz wire winding of a CLLC resonant circuit as claimed in any one of claims 1 to 7 when executed by the processor.

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