A planar transformer optimization design method and system

Abstract

The present invention discloses a planar transformer optimization design method and system, which belongs to the field of planar transformer design. After determining the optimal thickness of the winding and the optimal distance between the winding and the magnetic core air gap, the present invention analyzes other size parameters involved in the planar transformer, selects any two of the other size parameters as independent variables, and the remaining size parameters can be represented by the two independent variables; then, based on the two selected independent variables, the expressions of the total loss and area of ​​the planar transformer are obtained respectively, and multiple total loss contour lines and multiple area contour lines are further obtained; then, the tangent points of the multiple total loss contour lines and the multiple area contour lines are recorded, and the relationship curve between the total loss and the area is obtained based on each tangent point; finally, according to the relationship curve between the total loss and the area, the optimal tangent point is determined, thereby obtaining all the size parameters involved in the planar transformer. In this way, the present invention can improve the power density and efficiency of the planar transformer.

Description

Technical Field

[0001] The present invention belongs to the field of planar transformer design, and more specifically, relates to a planar transformer optimization design method and system. Background Art

[0002] As the operating frequency of the converter continues to increase, the volume of the magnetic components will be significantly reduced. However, increasing the operating frequency of the magnetic components will bring great negative effects. The most important problem is the enhancement of the skin effect and the proximity effect. The skin effect strengthens the current on the surface of the conductor and weakens the current in the center. The proximity effect refers to the changing magnetic field generated by two adjacent conductors, which causes the induced current to flow through the two conductors. If the currents flowing through the two conductors are in the same direction, the currents in the two conductors will be concentrated on the side surface away from the distribution; if the currents flowing through the two conductors are in opposite directions, the currents in the two conductors will be concentrated on the adjacent side surface. The uneven current distribution caused by the skin effect and the proximity effect increases the equivalent resistance value of the conductor, resulting in a significant increase in winding losses. At present, the commonly used method to reduce the losses caused by the skin effect and the proximity effect is to change the winding layout structure. The staggered layout can reduce the magnetic field strength and the magnetic field change rate, thereby reducing the uneven current distribution and reducing losses.

[0003] In actual transformer design, the excitation inductance is adjusted by adjusting the height of the air gap between the transformer magnetic columns to meet the design requirements. Therefore, in addition to the above-mentioned skin effect and proximity effect that will cause a significant increase in winding loss, the edge effect of the magnetic field generated by the core air gap on the winding loss cannot be ignored. If the winding copper layer is within the range of the external magnetic field, the changing magnetic field will pass through the winding copper layer. According to the law of electromagnetic induction and Lenz's law, induced voltage and induced current will be generated in the winding copper layer, thereby changing the distribution of current density in the winding, making the current density distribution more uneven, the equivalent resistance of the winding copper layer will increase, and the winding loss will increase. The loss caused by the external magnetic field of the air gap can be reduced by setting a distributed air gap or moving the air gap away from the winding.

[0004] In high-frequency planar transformers, due to the presence of multiple copper layers, the series and parallel connections between multiple layers need to be realized through through-holes. However, since the currents at the input and output terminals flow in opposite directions, and the currents of the multiple windings before parallel connection flow in the same direction, strong skin effect and proximity effect will be generated, so there will be great losses at the input and output terminals and parallel through-holes, limiting the improvement of the overall efficiency of the transformer. In order to reduce the use of AC parallel through-holes, shorten the length of the input and output terminals, and reduce winding losses, the design can be carried out by rectifying and filtering first and then performing DC parallel connection.

[0005] In the existing traditional planar transformer design cases, most of them still use the same Ap method as ordinary transformer design for design. Ap represents the effective cross-sectional area of ​​the magnetic core A.e and the core window area A w However, this method has the following defects: In order to reduce the core loss, the maximum value of the magnetic flux density inside the core, B max A large margin will be left when selecting. If a relatively small value is taken, the corresponding Ap value will be too large, which is not conducive to improving the power density of traditional planar transformers. The core window utilization K w This is an estimate and is not accurate. The model of commercial planar magnetic cores is fixed. Under certain circumstances, the Ap value of the core model selected deviates greatly from the designed Ap value, resulting in an excessively high Ap value margin, which will also reduce the power density of traditional planar transformers. Summary of the invention

[0006] In view of the defects of the prior art and the need for improvement, the present invention provides a planar transformer optimization design method and system, aiming to solve the technical problem that the existing planar transformer design method is not conducive to improving the power density of the planar transformer.

[0007] To achieve the above objectives, in a first aspect, the present invention provides a planar transformer optimization design method, comprising:

[0008] S1, determine the optimal thickness of the winding and the optimal distance between the winding and the core air gap;

[0009] S2, after determining the optimal thickness and the optimal distance, analyzing other size parameters involved in the planar transformer, selecting any two of the other size parameters as independent variables, and the remaining size parameters can be represented by the independent variables;

[0010] S3, based on the two independent variables selected in S2, respectively obtain expressions for the total loss and area of ​​the planar transformer, wherein the total loss includes the winding loss and the core loss;

[0011] S4, based on the expressions of the total loss and area of ​​the planar transformer, obtaining a plurality of total loss contour lines and a plurality of area contour lines; recording the tangent points of the plurality of total loss contour lines and the plurality of area contour lines, and obtaining a relationship curve between the total loss and the area based on the tangent points;

[0012] S5, determining an optimal tangent point according to the relationship curve between the total loss and the area, thereby obtaining all size parameters involved in the planar transformer.

[0013] Further, the S1 includes:

[0014] S11, based on the Dowell model, obtain the relationship curve between winding loss and winding thickness, and select the winding thickness corresponding to the lowest winding loss as the optimal winding thickness;

[0015] S12, using magnetic simulation, obtain a curve of the relationship between the winding loss and the distance between the winding and the air gap of the magnetic core, and select the distance corresponding to the lowest winding loss as the optimal distance.

[0016] Furthermore, in S5, an optimal tangent point is selected according to the relationship curve between the total loss and the area, combined with the efficiency and power density requirements that the planar transformer needs to meet.

[0017] Further, when the planar transformer determined in S5 is the tallest device in the converter, the method further includes:

[0018] S6, obtaining a relationship curve between the total loss and the height of the planar transformer, and determining an optimal tangent point by combining the relationship curve between the total loss and the area.

[0019] Furthermore, when the planar transformer is a fractional-turn planar transformer, the other dimensional parameters are transformer length, transformer height, transformer width, magnetic core width, width of magnetic columns on both sides of the magnetic core, height of upper and lower covers of the magnetic core, radius of magnetic column at the center of the magnetic core, width of the primary winding, width of the secondary winding, and the center angle corresponding to the arc segment of each magnetic column;

[0020] The center angle corresponding to the arc segment of each side magnetic column and the core width are selected as two independent variables.

[0021] Furthermore, when the planar transformer is an integrated matrix planar transformer, the other size parameters are transformer length, transformer height, transformer width, magnetic core width, magnetic column width on both sides of the magnetic core, height of the upper and lower covers of the magnetic core, radius of the magnetic column at the center of the magnetic core, primary winding width, and secondary winding width;

[0022] The width of the secondary winding and the radius of the circular magnetic column of the core are selected as two independent variables.

[0023] In a second aspect, the present invention provides a planar transformer optimization design system, comprising: a computer-readable storage medium and a processor;

[0024] The computer-readable storage medium is used to store executable instructions;

[0025] The processor is used to read the executable instructions stored in the computer-readable storage medium to execute the planar transformer optimization design method as described in the first aspect.

[0026] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0027] After determining the optimal thickness of the winding and the optimal distance between the winding and the air gap of the magnetic core, the present invention analyzes other dimensional parameters involved in the planar transformer, selects any two of the other dimensional parameters as independent variables, and the remaining dimensional parameters can be represented by these two independent variables; then, based on the two selected independent variables, the expressions of the total loss and area of ​​the planar transformer are obtained respectively, and multiple total loss contour lines and multiple area contour lines are further obtained; then, the tangent points of the multiple total loss contour lines and the multiple area contour lines are recorded, and based on each tangent point, the relationship curve between the total loss and the area is obtained; finally, according to the relationship curve between the total loss and the area, the optimal tangent point is determined, thereby obtaining all the dimensional parameters involved in the planar transformer. In this way, after analyzing the key points and difficulties faced by the design of the planar transformer, the present invention proposes a new planar transformer optimization design method that can improve the power density and efficiency of the planar transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic flow chart of a planar transformer optimization design method provided in an embodiment of the present invention.

[0029] Figure 2 A simplified model of a fractional-turn planar transformer is provided in an embodiment of the present invention, wherein (a) is a cross-sectional view of a secondary winding of a fractional-turn planar transformer; (b) is a cross-sectional view of a primary winding of a fractional-turn planar transformer; and (c) is a longitudinal cross-sectional view of the entire fractional-turn planar transformer.

[0030] Figure 3 for Figure 2 There are multiple total loss contour lines and multiple area contour lines of the fractional-turn planar transformer in the figure; the curved line represents the total loss contour line of the fractional-turn planar transformer, and the oblique line tangent to it represents the area contour line of the fractional-turn planar transformer.

[0031] Figure 4 for Figure 2 The relationship between the total loss and area of ​​a fractional-turn planar transformer.

[0032] Figure 5 A simplified model of an integrated matrix planar transformer is provided in an embodiment of the present invention, wherein (a) is a cross-sectional view of the secondary winding of the integrated matrix planar transformer; (b) is a cross-sectional view of the primary winding of the integrated matrix planar transformer; and (c) is a longitudinal cross-sectional view of the entire integrated matrix planar transformer.

[0033] Figure 6 for Figure 5 The figure shows multiple total loss contour lines and multiple area contour lines of the integrated matrix planar transformer; the curved line represents the total loss contour line of the fractional-turn planar transformer, and the oblique line tangent to it represents the area contour line of the fractional-turn planar transformer. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] In the present invention, the terms "first", "second", etc. (if any) in the present invention and the accompanying drawings are used to distinguish similar objects but not necessarily to describe a specific order or sequence.

[0036] See also Figure 1 , is a flow chart of a planar transformer optimization design method provided by the present invention, comprising:

[0037] S1, determine the optimal thickness of the winding and the optimal distance between the winding and the core air gap;

[0038] Specifically, based on the Dowell model, a curve showing the relationship between winding loss and winding thickness is obtained, and the winding thickness corresponding to the lowest winding loss is selected as the optimal winding thickness; using magnetic simulation (such as Maxwell simulation), a curve showing the relationship between winding loss and the distance between the winding and the air gap of the magnetic core is obtained, and the distance corresponding to the lowest winding loss is selected as the optimal distance.

[0039] S2, after determining the optimal thickness and the optimal distance, analyzing other size parameters involved in the planar transformer, selecting any two of the other size parameters as independent variables, and the remaining size parameters can be represented by the independent variables;

[0040] In this embodiment, when the planar transformer is a fractional-turn planar transformer, the other dimensional parameters are transformer length, transformer height, transformer width, core width, core column width, core upper and lower cover plate height, core center column radius, primary winding width, secondary winding width, and the center angle corresponding to each side magnetic column arc segment; by analyzing the relationship between the variables and combining the constraints, the independent variables are reduced to 2. Preferably, the center angle corresponding to each side magnetic column arc segment and the core width W1 are selected as two independent variables.

[0041] When the planar transformer is an integrated matrix planar transformer, the other size parameters are transformer length, transformer height, transformer width, core width, core column width, core upper and lower cover plate height, core center column radius, primary winding width, and secondary winding width; by analyzing the relationship between the variables and combining the constraints, the independent variables are reduced to 2. Preferably, the secondary winding width and the core circular side column radius are selected as two independent variables.

[0042] S3, based on the two independent variables selected in S2, respectively obtain expressions for the total loss and area of ​​the planar transformer, wherein the total loss includes the winding loss and the core loss;

[0043] In this embodiment, the winding loss is calculated using the Dowell loss model, and the core loss is calculated using the Steinmetz empirical formula combined with the material characteristic parameters provided by the manufacturer. The area of ​​a planar transformer refers to the total area occupied by the planar transformer core and windings. In the discussion of converter power density, the transformer area is the most important indicator.

[0044] S4, based on the expressions of the total loss and area of ​​the planar transformer, obtaining a plurality of total loss contour lines and a plurality of area contour lines; recording the tangent points of the plurality of total loss contour lines and the plurality of area contour lines, and obtaining a relationship curve between the total loss and the area based on the tangent points;

[0045] In this embodiment, the point where the total loss contour line is tangent to the area contour line is the minimum transformer area under the same transformer total loss size, and is also the minimum transformer total loss under the same transformer area. The point line formed by connecting several of the tangent points can be considered as the optimized design guidance curve (i.e., the relationship curve between total loss and area).

[0046] S5, determining an optimal tangent point according to the relationship curve between the total loss and the area, thereby obtaining all size parameters involved in the planar transformer.

[0047] In this embodiment, the optimal tangent point is selected according to the relationship curve between the total loss and the area, combined with the efficiency and power density requirements that the planar transformer needs to meet.

[0048] In addition, since the converter has a large horizontal area, if the tallest device in the converter structure is the transformer, changes in the transformer height will have a significant impact on the overall power density of the converter. In this case, the transformer height needs to be used as an auxiliary indicator.

[0049] Further, when the planar transformer determined in S5 is the tallest device in the converter, the method further includes:

[0050] S6, obtaining a relationship curve between the total loss and the height of the planar transformer, and determining an optimal tangent point by combining the relationship curve between the total loss and the area.

[0051] The present invention is further described in detail below in conjunction with two specific embodiments.

[0052] It should be noted that the transformation ratio of the planar transformer in all the following embodiments is 16:1, and the SPPS winding layout is adopted. The original secondary winding copper layer thickness h′ and h″ remain unchanged, and the total thickness of the four-layer PCB, the spacing between each turn of the winding, the spacing d at the cutting point between the winding and the PCB edge, the side magnetic column height h1, etc., do not change due to the change of the overall structure of the transformer, and therefore remain unchanged.

[0053] Example 1: A fractional-turn planar transformer is used as an example for specific description. A single-turn secondary winding in a transformer does not contain all the main magnetic flux, but only 1 / i of the main magnetic flux. i turns of secondary windings are connected in parallel to contain all the main magnetic flux. At this time, 1 turn of the secondary winding is equivalent to 1 / i turns of the secondary winding, and the number of primary windings is correspondingly reduced to n / i turns, so the transformer equivalent transformation ratio is still n:1. Take the side magnetic column N t =4 for design description.

[0054] Follow the steps below to optimize the design:

[0055] according to Figure 2 , first list the relationship between each quantity and the constraints:

[0056] A e =πr 2

[0057] φ=90°-θ

[0058] r q =r+a

[0059] a=a2+2d

[0060] L1=W1=2(w+a)

[0061] L=W=2(w+2a-d)

[0062] H=h1+2h2

[0063] Among them, A e is the cross-sectional area of ​​the central magnetic column, r is the radius of the central magnetic column, φ is the central angle of the chord corresponding to the two adjacent side magnetic columns, θ is the central angle of each side magnetic column arc segment, r qis the distance between the side magnetic column and the center of the central magnetic column, a is 1 / 2 of the distance between the two side magnetic columns, a2 is the width of the secondary winding, d is the spacing between each turn of the winding and the spacing between the winding and the edge of the PCB, L1 is the length of the core, W1 is the width of the core, w is the outer width of the side magnetic column, L is the overall length of the planar transformer, W is the overall width of the planar transformer, H is the overall height of the planar transformer, h1 is the height of the core side column, and h2 is the height of the upper and lower covers of the core.

[0064] Assume that the radius of the dividing point between the inner and outer turns of the circular primary winding is x.

[0065]

[0066]

[0067] Where a1′ is the width of the inner turn primary winding, and a1″ is the width of the outer turn primary winding.

[0068] After integration, the DC resistance of the inner and outer two turns of the circular primary winding can be obtained as follows:

[0069]

[0070]

[0071] Where h′ is the thickness of the primary winding copper layer.

[0072] make:

[0073] R(x)=R 内 (x)+R 外 (x)

[0074] Differentiate R with respect to x, and when the derivative is 0, it is the minimum resistance of one layer of primary winding, which is also the optimal width design of the circular primary winding.

[0075]

[0076] From this we can find the optimal value of x:

[0077]

[0078] It can be seen that when the resistance of the inner and outer turns is the same, the total resistance is the smallest, and the corresponding total winding loss is also the lowest. Finally, the optimal width of the inner and outer turns of the primary winding is obtained.

[0079] The h2 expression is also derived as:

[0080]

[0081] There are too many independent variables in the above relationship, so it is necessary to improve the relationship between the various dimensions through angles θ and φ. First, we can get:

[0082]

[0083]

[0084] set up:

[0085]

[0086] Then r can be expressed as:

[0087]

[0088] Since the sum of the areas of the four side magnetic columns is equal to the effective cross-sectional area of ​​the magnetic core, the following relationship can be obtained:

[0089]

[0090] After sorting, the expression of w is:

[0091]

[0092] After finishing, we can get:

[0093]

[0094] Therefore, only two variables, the central angle θ corresponding to each magnetic column arc segment and the magnetic core width W1, can be used to represent the size of all magnetic cores and primary and secondary windings. Therefore, θ and W1 will be selected as independent variables for subsequent optimization design.

[0095] The Dowell model is used to calculate the DC resistance and AC resistance coefficient, and then the expression for the winding loss of the fractional-turn planar transformer is obtained based on the effective value of the primary and secondary winding currents.

[0096] According to the derived optimal width of the primary winding, the DC resistance of the two-turn annular primary winding on the same layer of the fractional-turn planar transformer is:

[0097]

[0098] Due to N t =4The fractional-turn planar transformer contains a total of 4 turns of primary winding, which is divided into two groups of inner and outer turns with the same structure. Therefore, the mathematical expression of the DC resistance of the primary winding of the fractional-turn planar transformer can be obtained:

[0099]

[0100] The structure of the secondary winding of the fractional-turn planar transformer is irregular, but the cross-sectional area of ​​the secondary winding is the same everywhere, so the resistance of the winding can be calculated in sections and added to get the DC resistance of a single turn of the secondary winding. The number of parallel turns of the secondary winding is 4, so the DC resistance of the secondary winding of the fractional-turn planar transformer can be derived:

[0101]

[0102] Calculate the AC resistance according to the Dowell model: The ratio of the actual width of the primary and secondary windings to the total width of the windings is:

[0103] η2=1

[0104]

[0105] M1=α1h′cothα1h′=M1′+jM″1 M2=α2h″cothα2h″=M2′+jM″2

[0106]

[0107] Where ω is the operating angular frequency of the converter. From this, it can be deduced that the AC resistance coefficients of the primary winding and the secondary winding of the fractional-turn planar transformer are:

[0108]

[0109] Where m1 is the number of layers of a single primary winding, m1 = 2; m2 is the number of layers of a single secondary winding, m2 = 1. The DC resistance multiplied by the AC resistance coefficient can be obtained to obtain the AC resistance of the primary and secondary windings of the planar transformer, and the expressions are:

[0110] R 1_ac =F R1 R 1_dc R 2_ac =F R2 R 2_dc

[0111] Finally, the expression of the fractional-turn planar transformer winding loss can be obtained as:

[0112] P winding =I1 2 R 1_ac +I1 2 R 1_dc +I2 2 R 2_ac +I2 2 R 2_dc

[0113] Based on the size relationship, the volume of the fractional-turn planar transformer core is derived as:

[0114] V core =2h1A e +2h2L1W1

[0115] Then, the Steinmetz empirical formula is used to calculate the core loss per unit volume of the fractional-turn planar transformer:

[0116] P v =kf s α B m β

[0117] Where P v It indicates the unit volume loss of a certain core material under certain working conditions. This empirical formula shows that P v is the repetitive magnetization frequency f s and the magnetic induction intensity amplitude B max exponential function. k, α, β are constants that define the working characteristics of magnetic materials. They are all empirical parameters, and their values ​​are provided by the core manufacturer.

[0118] The core loss of the fractional-turn planar transformer is obtained as follows:

[0119] P core =P v *V core

[0120] The total loss of the fractional-turn planar transformer is:

[0121] P loss =P core +P winding

[0122] Thus, a complete loss mathematical model of fractional-turn planar transformer is obtained.

[0123] Based on the expressions for the total loss and area of ​​the planar transformer, we get Figure 3 The multiple total loss contour lines and multiple area contour lines are shown in Figure 1. Record the tangent points of the multiple total loss contour lines and multiple area contour lines, and based on each tangent point, obtain the following Figure 4 The relationship between total loss and area is shown.

[0124] Finally, according to Figure 4 The relationship curve between total loss and area shown is combined with the efficiency and power density requirements that the planar transformer must meet to determine the optimal tangent point, thereby obtaining all the size parameters involved in the planar transformer.

[0125] Embodiment 2: Taking the integrated matrix planar transformer as an example, the simplified model is as follows Figure 5 The basic dimensional relationship and constraints are as follows:

[0126] A e =πr 2

[0127] W1=L1=4r+2a2+3d

[0128] L=W=4a2+4r+5d

[0129] H=h1+2h2

[0130]

[0131] Among them, A e is the area of ​​the core column, r is the radius of the core column, L1 is the total distance between the edges of the two magnetic columns, W1 is the diameter of the core column, a2 is the width of the secondary winding, d is the spacing between each turn of the winding and the spacing between the winding and the edge of the PCB, L is the total length of the matrix planar transformer, W is the total width of the matrix planar transformer, H is the total height of the matrix planar transformer, h1 is the height of the core side column, and h2 is the height of the upper and lower covers of the core.

[0132] Finally, the secondary winding width a2 and the circular magnetic column radius r of the core are selected as two independent variables.

[0133] The magnetic flux density in the center area of ​​the upper and lower covers of the integrated matrix planar transformer core is basically zero. From this, the mathematical expression of the effective volume of the integrated matrix planar transformer core is derived as follows:

[0134] V core =2h2(L1W1-(2a+3d) 2 -(4r 2 -A e ))+4h1A e

[0135] Similar to Example 1, the winding loss expression and the core loss of the integrated matrix planar transformer are derived. The winding loss is calculated by the Dowell model.

[0136] The optimal width design of the primary winding of the matrix transformer is optimized by adopting the design idea of ​​the primary winding width of the fractional-turn planar transformer. It can be obtained:

[0137]

[0138]

[0139]

[0140]

[0141] Where a1′ is the width of the inner turn primary winding, a1″ is the width of the outer turn primary winding, and h′ is the thickness of the primary winding copper layer.

[0142] make:

[0143] R(x)=R 内 (x)+R 外 (x)

[0144] Take the derivative of x. When the derivative is 0, it is the minimum resistance of the primary winding of the matrix planar transformer. At this time, the value of x is as follows:

[0145]

[0146] The DC resistance expression of the circular primary winding of the inner and outer turns of the matrix planar transformer can be obtained:

[0147]

[0148] Finally, the mathematical expression of the overall DC resistance of the primary winding is derived:

[0149]

[0150] Similarly, the mathematical expression of the DC resistance of the secondary winding is derived:

[0151]

[0152] Calculate the AC resistance according to the Dowell model: The ratio of the actual width of the primary and secondary windings to the total width of the windings is:

[0153] η2=1

[0154]

[0155] M1=α1h′cothα1h′=M1′+jM″1 M2=α2h″cothα2h″=M2′+jM″2

[0156]

[0157] Where ω is the operating angular frequency of the converter. From this, it can be deduced that the AC resistance coefficients of the primary winding and the secondary winding of the planar transformer are:

[0158]

[0159] Where m1 is the number of layers of a single primary winding, m1 = 2; m2 is the number of layers of a single secondary winding, m2 = 1. The DC resistance multiplied by the AC resistance coefficient can be obtained to obtain the AC resistance of the primary and secondary windings of the planar transformer, and the expressions are:

[0160] R1_ac =F R1 R 1_dc R 2_ac =F R2 R 2_dc

[0161] Finally, the expression of planar transformer winding loss can be obtained as:

[0162] P winding =I1 2 R 1_ac +I1 2 R 1_dc +I2 2 R 2_ac +I2 2 R 2_dc

[0163] Based on the size relationship, the volume of the integrated matrix planar transformer core is derived as:

[0164] V core =2h2(L1W1-(2a+3d) 2 -(4r 2 -A e ))+4h1A e

[0165] Then, the Steinmetz empirical formula is used to calculate the core loss per unit volume of the integrated matrix planar transformer:

[0166] P v =kf s α B m β

[0167] The core loss of the integrated rectangular planar transformer is obtained as:

[0168] P core =P v *V core

[0169] The total loss of the integrated rectangular planar transformer is:

[0170] P loss =P core +P winding

[0171] Thus, we can get Figure 6 The multiple total loss contour lines and multiple area contour lines are shown. The tangent points of the multiple total loss contour lines and the multiple area contour lines are recorded, and based on each tangent point, the final relationship curve between the total loss and the area is obtained.

[0172] In particular, based on the comprehensive comparison of the transformer indicators of the designed converter, the efficiency and power density of different planar transformers (traditional planar transformers, fractional-turn planar transformers, integrated matrix planar transformers) can be compared during the design to obtain the best planar transformer structure and the optimal design point.

[0173] In particular, if the transformer is not the tallest device in the converter, the optimal design can be obtained based on the total loss and area curve. If the transformer is the tallest device in the converter, it is necessary to comprehensively consider the relationship curves between total loss and area and total loss and height, select the height, area, and total loss compromise design point, and obtain the optimal design.

[0174] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A planar transformer optimization design method, characterized in that: include: S1, determine the optimum thickness of the winding and the optimum distance between the winding and the core air gap; including: S11, based on the Dowell model, obtain the relationship curve between winding loss and winding thickness, and select the winding thickness corresponding to the lowest winding loss as the optimal winding thickness; S12, using magnetic simulation, obtaining a curve of the relationship between the winding loss and the distance between the winding and the air gap of the magnetic core, and selecting the distance corresponding to the lowest winding loss as the optimal distance; S2, after determining the optimal thickness and the optimal distance, analyze other dimensional parameters involved in the planar transformer, select any two of the other dimensional parameters as independent variables, and the remaining dimensional parameters can be represented by the independent variables; when the planar transformer is a fractional-turn planar transformer, the other dimensional parameters are transformer length, transformer height, transformer width, core width, width of magnetic columns on both sides of the core, height of the upper and lower covers of the core, radius of the magnetic column at the center of the core, primary winding width, secondary winding width, and the center angle corresponding to the arc segment of each side magnetic column; The center angle of each magnetic column arc segment and the core width are selected as two independent variables; S3, based on the two independent variables selected in S2, respectively obtain expressions for the total loss and area of ​​the planar transformer, wherein the total loss includes the winding loss and the core loss; S4, based on the expressions of the total loss and area of ​​the planar transformer, obtaining a plurality of total loss contour lines and a plurality of area contour lines; recording the tangent points of the plurality of total loss contour lines and the plurality of area contour lines, and obtaining a relationship curve between the total loss and the area based on the tangent points; S5, determining an optimal tangent point according to the relationship curve between the total loss and the area, thereby obtaining all size parameters involved in the planar transformer.

2. The planar transformer optimization design method according to claim 1, characterized in that: In S5, the optimal tangent point is selected according to the relationship curve between the total loss and the area, combined with the efficiency and power density requirements that the planar transformer needs to meet.

3. The planar transformer optimization design method according to claim 1, characterized in that: When the planar transformer determined in S5 is the tallest device in the converter, the method further includes: S6, obtaining a relationship curve between the total loss and the height of the planar transformer, and determining an optimal tangent point by combining the relationship curve between the total loss and the area.

4. The planar transformer optimization design method according to claim 1, characterized in that: When the planar transformer is an integrated matrix planar transformer, the other size parameters are transformer length, transformer height, transformer width, magnetic core width, magnetic column width on both sides of the magnetic core, height of the upper and lower covers of the magnetic core, radius of the magnetic column at the center of the magnetic core, primary winding width, and secondary winding width; The width of the secondary winding and the radius of the circular magnetic column of the core are selected as two independent variables.

5. A planar transformer optimization design system, characterized in that: include: A computer readable storage medium and a processor; The computer-readable storage medium is used to store executable instructions; The processor is used to read the executable instructions stored in the computer-readable storage medium to execute the planar transformer optimization design method as described in any one of claims 1-4.

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