Design method for optimizing high-frequency inductor

Abstract

The invention discloses a design method for optimizing a high-frequency inductor. According to the technical scheme, the size of the magnetic core is calculated by multiplying inductance and current square calculation, then the minimum magnetic conductivity and the maximum number of turns are calculated, then the magnetic conductivity decrease rate is calculated by performing magnetic field intensity, the number of turns is adjusted, then copper wire loss and magnetic core loss are calculated, temperature rise is calculated, and the temperature rise is calculated. And the purpose of finally optimizing the specification value is achieved. Corresponding use performance parameters of the high-frequency inductor can be quickly and accurately calculated, the reasonability and reliability requirements of the inductor are judged, and the design of the high-frequency inductor can be further efficiently and quickly optimized.

Description

Technical Field

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

[0002] When designing a high-frequency inductor, the number of inductor turns and wire diameter can be designed using simple methods and experiments. However, it is not easy to optimize and meet the safety requirements of a cost-effective inductor, because as the load current increases, the magnetic field strength will also increase, causing the magnetic permeability to decrease. How to make the magnetic permeability change accordingly so that the load inductance reaches the specified value, and how to meet the theoretical calculation of the safety temperature rise are all difficult problems in the design of high-frequency inductors.

[0003] The present invention introduces the design method and ideas of high-frequency inductor in detail. First, the inductance and the square of the current are multiplied to calculate the size of the magnetic core, and 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 then the copper wire loss and the magnetic core loss are calculated, and then the temperature rise is calculated to achieve the final optimization of the specification value. Summary of the invention

[0004] The present invention first calculates the size of the magnetic core 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, adjusts the number of turns, and then calculates the copper wire loss and the magnetic core loss, and then calculates the temperature rise to reach the specification value.

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

[0006] A design method for optimizing high-frequency inductance 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 cross-sectional area of ​​the core; Aw is the winding area of ​​the core;

[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, the core winding area Aw, and the core average magnetic path length le according to 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] AW 实 is the core winding area after plating;

[0028] S61: Calculate the maximum permissible number of turns N 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 the 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 specification value;

[0034] According to the minimum value of 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 is compared, if N 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 remaining percentage after the estimated 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 inductance

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

[0046] S9: Minimum turns comparison and adjustment

[0047] L L The minimum required 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. Through further calculations, the corresponding performance parameters of the high-frequency inductor can be quickly and accurately calculated to achieve 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 it. If the temperature rise value meets the corresponding level requirement, the requirement is met. If not, return to S4 to 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 according to the circuit conditions:

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

[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 the effective current I RMS ;

[0075]

[0076] S114: Calculate copper loss P CU ;

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

[0078] S115: Calculate the temperature rise value;

[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 it is not satisfied, return to S4 to reselect the primary core size and execute the 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°C, minus ambient temperature 45°C), and for Class B it is 85K (insulation temperature is 130°C, minus ambient temperature 45°C).

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

[0085] Through the above steps, the temperature rise value can be accurately calculated, so as to determine the rationality and reliability requirements of the inductor, and the design of the high-frequency inductor can be further optimized efficiently and quickly.

[0086] Compared with the prior art, the present invention has the following beneficial effects: the present method can quickly and accurately calculate the corresponding performance parameters of the high-frequency inductor by preliminarily selecting the material of the metal magnetic powder core, optimizing the selection of the magnetic core size, and further calculating, thereby realizing the optimized design of the high-frequency inductor. Furthermore, the present invention can more accurately calculate the temperature rise value through theoretical magnetic loss, copper loss and heat dissipation area, thereby determining the rationality and reliability requirements of the inductor, and can further efficiently and quickly optimize the design of the high-frequency inductor. DETAILED DESCRIPTION

[0087] In order to make the purpose, technical solution 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 used to limit the present invention.

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

[0089] S1: Known design specifications:

[0090] a) Output rated current I0 (in 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 = 500A / cm 2 ; (Unit: 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: Select the material whose core size AP value is greater than the calculated AP value in the material list;

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

[0105]

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

[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, ID=23.4mm is the inner diameter of the core, and HT=9mm is the height of the core.

[0111] Core winding area

[0112] Average magnetic path length of core

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

[0114]

[0115] OD = 34.8, ID = 23.4, HT = 9.0 before plating correspond to OD' = 35.6 mm, ID' = 22.59 mm, HT' = 9.81 mm after plating;

[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] AW 实 is the core winding area after plating;

[0122]

[0123] S61: Calculate the maximum permissible number of turns N 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 the 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 specification value;

[0128]

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

[0130] In this calculation, μ r =60, using metal magnetic powder core iron silicon series products with good cost performance, 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 is compared, if N 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 remaining percentage after the estimated 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 and 2.13×10 -4 , 2.056;

[0147]

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

[0149] S83: No-load inductance

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

[0151] S9: minimum turns comparison and adjustment;

[0152] L L The minimum required inductance value L min In comparison, 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, and it meets the requirements.

[0163] S11: Calculate the temperature rise value and compare it. If the temperature rise value meets the requirements of the corresponding level, the requirements are met. If not, return to S4 to 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 according to the circuit conditions:

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

[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 the 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 it is not satisfied, return to S4 to reselect the primary core size and execute the subsequent steps.

[0194] Although the present invention is described herein with reference to the illustrative embodiments of the present invention, it should be understood that those skilled in the art can design many other modifications and implementations, which will fall within the scope and spirit of the principles disclosed in the present application. More specifically, within the scope disclosed in the present application, multiple variations and improvements can be made to the components and / or layout of the subject combination layout. In addition to the variations and improvements made to the components and / or layout, other uses will also 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 cross-sectional area of ​​the core; Aw is the winding area of ​​the core; 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, the core winding area Aw, and the core average magnetic path length le according to 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 I through the load 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; AW 实 is the core winding area after plating; S61: Calculate the maximum permissible number of turns N 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 the corresponding magnetic permeability μ r Metal powder core; Selected μ r Must be greater than μ min ; According to the minimum value of 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 is compared, if N 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 remaining percentage after the estimated 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 inductance S84: Load inductance L L =L0×μ e '; S9: minimum turns comparison and adjustment; L L The minimum required 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%).

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. A design method for optimizing high-frequency inductance according to claim 1, characterized in that: After executing S9, perform the following steps: S11: Calculate the temperature rise value and compare it. 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 as claimed in 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 according to the circuit conditions: When the circuit is a coexistent load of AC and DC: 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 the effective current I RMS ; S114: Calculate copper loss P CU ; P CU =I RMS 2 R DCR ; S115: Calculate the temperature rise value; 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. A design method for optimizing high-frequency inductance as claimed in claim 4, characterized in that: 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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