A design method for optimizing high-frequency inductors

Abstract

This invention discloses a design method for optimizing high-frequency inductors. The technical solution of the present invention calculates the core size by multiplying the inductance and the square of the current, then calculates the minimum permeability and maximum number of turns. The magnetic field strength is then used to calculate the rate of decrease in permeability. The number of turns is then adjusted, and copper wire loss and core loss are calculated. Furthermore, the temperature rise is calculated to ultimately optimize the specification values. This method can quickly and accurately calculate the corresponding performance parameters of high-frequency inductors, determine the rationality and reliability requirements of the inductor, and further efficiently and quickly optimize the design of high-frequency inductors.

Description

Technical Field

[0001] The present invention relates to a method for optimizing the design of a high-frequency inductor. The present invention relates to a method for optimizing the design of a high-frequency inductor. Background Art

[0002] When designing a high-frequency inductor, the number of turns and wire diameter can be determined using simple methods and experiments. However, optimizing and achieving a cost-effective inductor that meets safety regulations is not straightforward. This is because as the load current increases, the magnetic field strength also increases, causing the magnetic permeability to decrease. Adjusting the magnetic permeability accordingly to ensure the load inductance meets the specified value, as well as theoretically calculating the temperature rise required to meet safety regulations, are both challenging issues in high-frequency inductor design.

[0003] This invention introduces the design method and ideas of high-frequency inductors in detail. First, the inductance and the square of the current are multiplied to calculate the core size. Then, the minimum magnetic permeability and the maximum number of turns are calculated. The magnetic field strength is then used to calculate the magnetic permeability drop rate. The number of turns is adjusted, and the copper wire loss and the core loss are calculated. Finally, the temperature rise is calculated to achieve the ultimate optimization of the specification value. Summary of the Invention

[0004] The present invention first calculates the core size by multiplying the inductance and the square of the current, then calculates the minimum magnetic permeability and the maximum number of turns, and then calculates the magnetic permeability decrease rate by performing magnetic field strength calculation. The number of turns is adjusted, and then the copper wire loss and the core loss are calculated, and then the temperature rise is calculated to reach the specification value.

[0005] In order to solve the above technical problems, one embodiment of the present invention adopts the following technical solutions:

[0006] A design method for optimizing high-frequency inductors includes the following steps:

[0007] S1: known design specifications;

[0008] The design specifications include: output rated current I0, required inductance value L, ripple rate ε% (generally set at 20-40%), current density J (unit A / cm 2 ), core window occupancy K U ; Core temperature rise (generally set to ≤75~85K), switching frequency f;

[0009] S2: Calculate the peak current I P ;

[0010]

[0011] S3: Calculate the initial core size AP;

[0012]

[0013] L min is the inductance of the minimum load, L min =L×(1-10%), Bm is the magnetic flux density;

[0014] AP = Ae × Aw, where Ae is the core cross-sectional area; Aw is the core winding area;

[0015] S4: Select the material whose core size AP value is greater than the calculated AP value from the material list;

[0016] According to the material core size, the core outer diameter OD, core inner diameter ID and core height HT are obtained;

[0017] S5: Calculate the core cross-sectional area Ae, core winding area Aw, and core average magnetic path length le based on the selected material;

[0018]

[0019] S51: Calculate the core surface area S 表 ;

[0020]

[0021] Among them, OD', ID', and HT' are the OD, ID, and HT after coating;

[0022] S52: Peak current through load I p And the current density J is used to calculate the corresponding wire diameter Φ;

[0023] Wire diameter Where N is the number of shares;

[0024] For example, when single strand, the wire diameter

[0025] 2 strands, wire diameter

[0026] S6: Select wire diameter: Φ;

[0027] Awb 实 is the core winding area after plating;

[0028] S61: Calculate the maximum number of circles N allowed max ;

[0029]

[0030] Among them Ku max ' is the maximum space utilization, take Ku max '=0.45;

[0031] S7: According to the core size, LI 2 curve graph, and μ min Requirements, select the core size and corresponding magnetic permeability μ r Metal powder core;

[0032]

[0033] Selected μ r Must be greater than μ min , otherwise the inductance will not reach the specified value;

[0034] According to the minimum value μ min , select the corresponding relative permeability μ r

[0035] S8: Calculate the minimum number of turns N min , calculate the remaining percentage μ after the magnetic permeability decreases r ', no-load inductance L0 and load inductance L L ;

[0036] S81: Minimum turns calculation

[0037] N min With N max The value of N is compared. min <N max , go to the next step, if N min >N max , you need to return to step S7 and reselect μ r or Ae;

[0038] S82: Calculate H dc ;

[0039]

[0040] H dc is the estimated magnetic field strength;

[0041] μ r ' is the estimated remaining percentage after the permeability decreases;

[0042] Where a, b, c are the material and relative magnetic permeability μ r The corresponding constants, a, b, and c are determined by the metal powder core;

[0043] At this time μ e '=μ r ×μ r ';

[0044] S83: No-load inductor

[0045] S84: Load inductance L L =L0×μ e ';

[0046] S9: Minimum turns comparison and adjustment

[0047] L L and the required minimum inductance value L min Compare, if L L <L min , it does not meet the specification value and needs to increase N min ; The increased value N min 'Re-enter S81 calculation until L L ≥L min , at this time, the estimated turns value N' is obtained, where L min =L×(1-10%).

[0048] Through the above calculations, the metal powder core material can be preliminarily selected and the core size can be optimized. Further calculations can also be used to quickly and accurately calculate the corresponding performance parameters of the high-frequency inductor, thereby achieving optimized design of the high-frequency inductor.

[0049] A further technical solution is to perform the following steps after executing S9:

[0050] S10: Calculate the comparative occupancy rate Ku';

[0051]

[0052] The calculated Ku' and Ku max (Generally, Ku' is set at 45% to allow winding without bag expansion) For comparison, if Ku'>Ku max (45%), then increase the primary core size AP' and recalculate, or select a larger current density J and reduce the wire diameter and recalculate;

[0053] If Ku'<Ku max (45%), it meets the design requirements.

[0054] A further technical solution is to perform the following steps after executing S9:

[0055] S11: Calculate the temperature rise value and compare. If the temperature rise value meets the corresponding level requirement, the requirement is met. If not, return to S4 and reselect the primary core size.

[0056] A further technical solution is that the specific step S11 includes:

[0057] S111: Calculate core loss, P core =Ve×(d×fe ×ΔB g );

[0058] Among them, P core is the core loss; Ve is the core volume Ve=Ae×le; f is the frequency;

[0059] ΔB is the AC magnetic flux density (in kilogauss);

[0060] d, e, and g are material parameters;

[0061] ΔB needs to be calculated based on the circuit conditions:

[0062] When the circuit is a coexistent AC and DC load:

[0063] When the circuit is an AC load:

[0064] According to the determined material and magnetic permeability μ r , we can get d; e; g by looking up the table;

[0065] Calculate the wattage per unit volume P AV ;

[0066] P AV =d×f e ×ΔB g ;

[0067] P core =Ve×P AV (unit: W);

[0068] S112: Calculate copper wire loss;

[0069] Calculate the average winding length L 平 ,

[0070] 1.3 is defined as the length factor;

[0071] Calculate the DC resistance R DCR ;

[0072]

[0073] ρ is the resistivity of copper wire when the temperature rise is 75 degrees, ρ = 2.06 × 10 -8 (Ω.m), N' is the final estimated number of turns;

[0074] S113: Calculate effective current I RMS ;

[0075]

[0076] S114: Calculate copper loss P CU ;

[0077] P CU =I RMS 2 R DCR (W);

[0078] S115: Calculate temperature rise;

[0079]

[0080] S116: Compare the theoretical temperature rise value with the safety specification temperature rise value. If the temperature rise value is less than the safety specification temperature rise value, it is safe.

[0081] If not, return to S4 to reselect the primary core size and execute subsequent steps.

[0082] A further technical solution is that the safety specification temperature rise value is:

[0083] For Class F insulated inductors, the general temperature rise is 110K (insulation temperature is 155℃, minus 45℃ ambient temperature), and for Class B it is 85K (insulation temperature is 130℃, minus 45℃ ambient temperature).

[0084] If the temperature does not meet the requirements, return to S4 and select a material with a larger AP to recalculate.

[0085] The above steps can accurately calculate the temperature rise value, thereby determining the rationality and reliability requirements of the inductor, and further optimizing the design of high-frequency inductors efficiently and quickly.

[0086] Compared with existing technologies, this method offers the following advantages: By initially selecting the metal powder core material, optimizing the core size, and further calculating the corresponding performance parameters of high-frequency inductors, this method can quickly and accurately calculate the corresponding performance parameters, thereby achieving optimized design of high-frequency inductors. Furthermore, this method uses theoretical magnetic loss, copper loss, and heat dissipation area to more accurately calculate the temperature rise value, thereby determining the rationality and reliability requirements of the inductor, and can further efficiently and quickly optimize the design of high-frequency inductors. DETAILED DESCRIPTION

[0087] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the 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.

[0088] A design method for optimizing high-frequency inductors includes the following steps:

[0089] S1: Known design specifications:

[0090] a) Output rated current I0 (unit: A). In this embodiment, I0 = 10A

[0091] b) Required inductance value L (unit: H) In this embodiment, L = 0.0002H = 200μH + / - 10%

[0092] c) Ripple rate ε% (unit: %). In this embodiment, the ripple rate is 30%

[0093] d) Current density J, in this embodiment, J = 500 A / cm 2 ; (Unit is A / cm 2 )

[0094] e) Magnetic core window occupancy rate. In this embodiment, the occupancy rate is ≤ 45%

[0095] f) In this embodiment, the core temperature rise is ≤80K, and the core temperature rise value can be adjusted according to customer requirements;

[0096] S2: Calculate the peak current I P ;

[0097]

[0098] S3 calculates the preliminary core size; the preliminary core size AP;

[0099]

[0100] Where: L min is the inductance of the minimum load, L min = L × (1-10%), Ku is the occupancy rate, set Ku = 0.45; Bm is the magnetic flux density, set Bm = 0.6T; J is the current density, set J = 500A / cm 2 ;

[0101] AP = Ae × Aw;

[0102]

[0103] S4: In the material list, select the material whose core size AP value is greater than the calculated AP value;

[0104] The material list is as follows. In this example, AP = 2.14 cm 4 materials;

[0105]

[0106] Select the core size as follows: core outer diameter OD = 34.8 mm, core inner diameter ID = 23.4 mm, and core height HT = 9 mm;

[0107] S5: Calculate the core cross-sectional area Ae, core winding area Aw, and core average magnetic path length le based on the selected material:

[0108] According to the core size, the following corresponding core parameters are obtained:

[0109] Core cross-sectional area

[0110] Among them, OD=34.8mm is the outer diameter of the core (mm), ID=23.4mm is the inner diameter of the core (mm), and HT=9mm is the height of the core (mm);

[0111] Core winding area

[0112] Average magnetic path length of the core

[0113] S51: Calculate the core surface area S 表 ;

[0114]

[0115] Before coating, OD = 34.8, ID = 23.4, and HT = 9.0 correspond to OD' = 35.6 mm, ID' = 22.59 mm, and HT' = 9.81 mm after coating, respectively;

[0116] S52: Peak current through load I p and current density J = 5A / mm 2 The corresponding wire diameter Φ is calculated;

[0117] Wire diameter Where N is the number of shares;

[0118] When single strand, wire diameter Φ1=1.56 (for non-standard enameled wire, select Φ1=1.5);

[0119] 2 strands, wire diameter Φ2=1.11x2;

[0120] S6: Select single strand wire diameter: Φ1=1.5

[0121] Awb 实 is the core winding area after plating;

[0122]

[0123] S61: Calculate the maximum number of circles N allowed max ;

[0124]

[0125] Among them Ku max ' is the maximum space utilization, take Ku max '=0.45;

[0126] S7: According to the core size, LI 2 curve graph, and μ min Requirements, select the core size and corresponding magnetic permeability μ r Metal powder core;

[0127] Selected μ r Must be greater than μ min , otherwise the inductance will not reach the specified value;

[0128]

[0129] According to the minimum value μ min , select the corresponding relative permeability μ r ;

[0130] In this calculation, μ r =60, using the best performance-price ratio metal powder core iron silicon series products, μ r =60, generally as follows:

[0131] 1) Conventional iron silicon GF60;

[0132] 2) Low-loss gas-atomized iron silicon GFH60;

[0133] 3) Super atomized low-loss iron silicon GFL60, etc.

[0134] In this embodiment, the load current I p is 11.5A, so the magnetic permeability μ is selected r =60 metal powder core, made of aerosolized iron silicon GFH60.

[0135] S8: Calculate the minimum number of turns N min , calculate the remaining percentage μ after the magnetic permeability decreases r ', no-load inductance L0 and load inductance L L ;

[0136] S81: Minimum turns calculation:

[0137]

[0138] N min With N max The value of N is compared. min <N max , go to the next step, if N min >N max, you need to return to step S7 and reselect μ r or Ae;

[0139] In this embodiment, N max =101T,N min <N max , proceed to the next step;

[0140] S82: Calculate H dc ;

[0141]

[0142]

[0143] Among them H dc is the estimated magnetic field strength;

[0144] μ r ' is the estimated remaining percentage after the permeability decreases;

[0145]

[0146] Where a, b, c are relative magnetic permeabilities μ r Corresponding constants; where a, b, and c are determined by the metal magnetic powder core. In this embodiment, a, b, and c are 1, 2.13×10 -4 , 2.056;

[0147]

[0148] μ e '=μ r ×μ r = 60 × 72.5% = 43.5

[0149] S83: No-load inductor

[0150] S84: Load inductance L L =L0×μ e '=201.4×72.5%=146.0μH

[0151] S9: Comparison and adjustment of minimum number of turns;

[0152] L L The minimum inductance value L is required min Compare, at this time L L =146.0μH and minimum inductance value L min (L min = L × (1-10%) = 180 μH) compared to L L <L min , then you need to increase N min, the increased value N min 'Re-enter S81 calculation;

[0153] Now increase the number of turns from 69T to an estimated value of 86T(N'), and bring it back into S82 to calculate H dc ',ur%' and L L '

[0154] S91:

[0155]

[0156] S92:μ e ”=μ r ×μ r =60×62.7%=37.6

[0157] S93:

[0158] S94:L L '=L0'×μ e ”=312.9×62.7%=196.2μH,L min =200μH(1-10%)=180μH,

[0159] L L '>L min , meeting the requirements.

[0160] S10: Calculate the comparative occupancy rate Ku';

[0161]

[0162] Compare the calculated Ku' with the maximum value of 0.45, which meets the requirements.

[0163] S11: Calculate the temperature rise value and compare. If the temperature rise value meets the corresponding level requirement, the requirement is met. If not, return to S4 and reselect the primary core size.

[0164] The specific steps of S11 include:

[0165] S111: Calculate core loss, P core =Ve×(d×f e ×ΔB g );

[0166] Among them, P core is the core loss; Ve is the core volume Ve=Ae×le; f is the frequency;

[0167] ΔB is the AC magnetic flux density (in kilogauss);

[0168] d, e, and g are material parameters;

[0169] ΔB needs to be calculated based on the circuit conditions:

[0170] When the circuit is a coexistent AC and DC load:

[0171] When the circuit is an AC load:

[0172] In this embodiment, since the circuit ripple current is 3.0A (about 30%) and it belongs to AC and DC loads:

[0173]

[0174] By material GFH, μ r =60, we can get d = 3.876; e = 1.262; g = 2.047;

[0175] P AV =d×f e ×ΔB g ;

[0176] P AV =3.876×40 1.262 ×0.6 2.047 =0.353W / cm 3 ;

[0177] P AV is the wattage per unit volume;

[0178] P core =Ve×P AV =4689.9 / 1000×0.353=1.656W;

[0179] S112: Calculate copper wire loss;

[0180] Calculate the average winding length L 平 ,

[0181]

[0182] R DCR is the DC resistance; ρ is the resistivity at 80°C;

[0183] When ρ changes from 0℃ to 80℃, R DCR(80℃) =1.557×10 -8 ×(1+0.0043×80)=2.092×10 -8 Ω.m;

[0184] RDCR =42.43×86×2.092x10 -8 / (π / 4×1.5 2 )=0.0432(Ω)(80℃);

[0185] S113: Calculate effective current I RMS ;

[0186]

[0187] S114: Calculate copper loss P CU ;

[0188] P CU(80℃) =I RMS 2 R DCR =10.04 2 × 0.0432 = 4.354 (W);

[0189] S115: Calculate the theoretical temperature rise, where P CU(80℃) =4.353(W);

[0190] P Fe =1.656W, surface area = 35.808cm 2 ;

[0191]

[0192] S116: Compare the theoretical temperature rise value with the safety specification temperature rise value. If the temperature rise value is less than the safety specification temperature rise value, it is safe.

[0193] If not, return to S4 to reselect the primary core size and execute subsequent steps.

[0194] Although the present invention has been described herein with reference to illustrative embodiments of the present invention, it will be appreciated that those skilled in the art may devise numerous other modifications and implementations that fall within the scope and spirit of the principles disclosed herein. More specifically, within the scope disclosed herein, various variations and improvements may be made to the components and / or layout of the subject combination layout. In addition to variations and improvements made to the components and / or layout, other uses will be apparent to those skilled in the art.

Claims

1. A design method for optimizing high-frequency inductance, characterized in that: The following steps are involved: S1: known design specifications; The design specifications include: output rated current I0, required inductance value L, ripple rate ε%, current density J, core window occupancy K U , vacuum permeability μ0, core temperature rise, switching frequency f; S2: Calculate the peak current I P ; S3: Calculate the initial core size AP; L min is the inductance of the minimum load, L min =L×(1-10%), Bm is the magnetic flux density; AP = Ae × Aw, where Ae is the core cross-sectional area; Aw is the core winding area; S4: Select the material whose core size AP value is greater than the calculated AP value from the material list; According to the core size, the core outer diameter OD, the core inner diameter ID and the core height HT are obtained; S5: Calculate the core cross-sectional area Ae, core winding area Aw, and core average magnetic path length le based on the selected material; S51: Calculate the core surface area S 表 ; Among them, OD', ID', and HT' are the OD, ID, and HT after coating; S52: Peak current through load I p And the current density J is used to calculate the corresponding wire diameter Φ; Wire diameter Where N is the number of shares; S6: Select wire diameter: Φ; Awb 实 is the core winding area after plating; S61: Calculate the maximum number of circles N allowed max ; Among them Ku max ' is the maximum space utilization; S7: According to the core size, LI 2 curve graph, and μ min Requirements, select the core size and corresponding magnetic permeability μ r Metal powder core; Selected μ r Must be greater than μ min ; According to the minimum value μ min , select the corresponding relative permeability μ r S8: Calculate the minimum number of turns N min , calculate the remaining percentage μ after the magnetic permeability decreases r ', no-load inductance L0 and load inductance L L ; S81: Minimum turns calculation N min With N max The value of N is compared. min <N max , go to the next step, if N min >N max , you need to return to step S7 and reselect μ r or Ae; S82: Calculate H dc ; H dc is the estimated magnetic field strength; μ r ' is the estimated remaining percentage after the permeability decreases; Where a, b, c are the material and relative magnetic permeability μ r The corresponding constants, a, b, and c are determined by the metal powder core; At this time μ e '=μ r ×μ r '; S83: No-load inductor S84: Load inductance L L =L0×μ e '; S9: Comparison and adjustment of minimum number of turns; L L The minimum inductance value L is required min Compare, if L L＜ L min , it does not meet the specification value and needs to increase N min ; The increased value N min 'Re-enter S81 calculation until L L ≥L min , at this time, the estimated turns value N' is obtained, where L min =L×(1-10%).

2. A design method for optimizing high-frequency inductance according to claim 1, characterized in that: After executing S9, perform the following steps: S10: Calculate the comparative occupancy rate Ku'; The calculated Ku' and Ku max For comparison, if Ku'>Ku max , then increase the primary core size AP' and recalculate, or select a larger current density J and reduce the wire diameter and recalculate; If Ku'<Ku max , it meets the design requirements.

3. The design method for optimizing high-frequency inductance according to claim 1, wherein: After executing S9, perform the following steps: S11: Calculate the temperature rise value and compare. If the temperature rise value meets the corresponding level requirement, the requirement is met. If not, return to S4 and reselect a larger core size.

4. A design method for optimizing high-frequency inductance according to claim 3, characterized in that: The specific steps of S11 include: S111: Calculate core loss, P core =Ve×(d×f e ×ΔB g ); Among them, P core is the core loss; Ve is the core volume; f is the frequency; ΔB is the AC magnetic flux density (in kilogauss); d, e, and g are material parameters; ΔB needs to be calculated based on the circuit conditions: When the circuit is a coexistent AC and DC load: When the circuit is an AC load: According to the determined material and magnetic permeability μ r , we can get d; e; g by looking up the table; calculate the wattage per unit volume P AV ; P AV =d×f e ×ΔB g ; P core =Ve×P AV ; S112: Calculate copper wire loss; Calculate the average winding length L 平 , Calculate the DC resistance R DCR ; ρ is the resistivity of the copper wire, N' is the final estimated number of turns; S113: Calculate effective current I RMS ; S114: Calculate copper loss P CU ; P CU =I RMS 2 R DCR ; S115: Calculate temperature rise; S116: Compare the theoretical temperature rise value with the safety specification temperature rise value. If the temperature rise value is less than the safety specification temperature rise value, it is safe.

5. The design method for optimizing high-frequency inductance according to claim 4, wherein: The safety specification temperature rise value is: For Class F insulated inductors, the general temperature rise is 110K, and for Class B it is 85K; If the temperature does not meet the requirements, return to S4 and select a material with a larger AP to recalculate.

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