Magnetic Problems Magnetics Group DPEC 2004 4 28
Magnetic Problems Magnetics Group DPEC 2004 -4 -28 1
Consideration of Core Material Selection 1. 如何正確建議 程師使用鐵心? Material performance factor f*B EPCOS Pc △T Pcv=500 kw/m 3 core material Pcv=300 kw/m 3 3) Pcv=300(kwm 3) Pcv=300(kw/m Pcv=100(kwm 3) 3) Pcv=100(kw/m N 97 Pcv=500 kw/m 3 Ferroxcube Pcv=500(kwm 3) 3) Pcv=500(kw/m fs Pcv=100 kw/m 3 N 49 3 F 4 3 F 35 T=100℃ 1000 3 C 96 ℃ T=100� 1000 2000 f*B vs. frequency 2
2. 設計頻率200 KHZ~500 KHZ, 應如何選擇適用的的鐵芯材質. High Frequency Ferrite Material Class v 100 k. Hz~300 k. Hz-----3 C 94, PC 40, 3 C 96, PC 44, PC 47…. v 300 k. Hz~500 k. Hz----3 F 3, P 5, 2 M, MBF 4, BH 5…. v 500 k. Hz~1 MHz------3 F 35, N 49, MC 2, PC 50, BH 40…. v 1 MHz~2 MHz-------3 F 4, 3 F 45, N 59, 7 H 20…. . v 2 MHz~4 MHz-------3 F 5 v 4 MHz~10 MHz------4 F 1, F 2(Ni. Zn) 3
300 k. Hz~500 k. Hz Material Comparison 4
3. ADP在使用Half Bridge Circuit設計變壓器時, 使用 3 C 96鐵心材質會有 好的溫度表現；使用Fly. Back Circuit則使用 2 HM 5會有較好的溫度表現。 3 C 96 Bs = 0. 37 T 2 HM 5 Bs = 0. 41 T ADP-150 BP (AHB) Bac = 112 m. T ADP-75 HB (Flyback) Bac = 103 m. T Bdc = 230 m. T Bm = 333 m. T 5
4. 如何有效利用鐵心(鐵心開模的建議) Ø LLC integrated magnetics core Original design Uneven flux Optimal design Even flux 6
Ø Modified PJ core v Even flux v Winding consideration (winding space, terminal) 7
How to Calculate Gap Length? Ø Challenges in gapped inductance calculation Winding location Gap length Core area Many inaccurate formula! Window size Inductance with gap A lot of time spending! Frequency Core length Gap location Ø More accurate formula Error comparison of the Equations 60 Error (%) Other equations 40 20 0 Measured 0. 0 0. 5 1. 0 1. 5 Our Eq. 2. 0 2. 5 3. 0 -20 -40 Air gap (mm) 8
Ø Suitable cases EE core EI core Winding near gap Winding far from gap Ø Calculation tool interface 9
Core and Circuit Type Selection 在多少瓦特數時 (FLYBACK 、FORWARD 、FULL BRIDGE、 HALF BRIDGE等) ，如何選用何種TYPE形式最有效益。 Ø Characteristics of converters Ø Common used core shape Flyback: High output current ripple Po<150 W Poor cross regulation High Bm (Bac + Bdc) High turns number PJ, RM core Forward: low voltage, high current PJ, RM: large Ae, good EMI EE, ETD: large Aw, good heat emission, poor EMI PQ: large Ae, good EMI, poor terminal and high power application Half bridge: high input voltage application Full bridge: high power application EE, ER, ETD, PQ core 10
Safety Problem of Transformer 家電類POWER SUPPLY需作PLD測試, (6. 6 KVac, 500 A), 對X‘FMR會有什麼影響? Good insulation! Good withstand voltage capability! 11
EMI Problem 1. 變壓器正繞、反繞及腳位互換時, 對於ADP的影響(EMI、特性. …等)? D + N 1 N 2 Vin C Jumped voltage point: most inside the bobbin Vo - S Constant voltage point: far away from the jumped voltage point Constant voltage point Jumped voltage point Test result of 75 W adaptor Jumped point P 2 S P 1 Original design EMI/d. Bu. V 70 70 60 60 50 50 40 40 20 20 10 10 0 0 -10 100 k 1 M 100 k P 2 S P 1 Jumped point 1 M Optimal design 12
2. 變壓器的EMI 、NOISE過大時該如何改善…? C 1: Switch to Heatsink C 2: Heatsink to Ground C 3: Secondary to Ground CPS: Transformer Parasitic Capacitance Ø If heatsink is connected to the minus, C 1, C 2 0. Ø CPS<<C 3, CP CPS. Ø Cps is a key parameter to be minimum. v Add shielding: decrease Cps v Jumped voltage point: most inside the bobbin v Constant voltage point: far away from the jumped voltage point v Filter component: far away from transformer 13
3. DIFFER&COMMON CHOKE對於EMI, RFI的抑制, 基本設計關係式? (CORE TYPE) CM choke as an example LISN 50 ohm Filter Power supply CM choke L LISN C Vd 25 ohm With filter: VLISN = Vs Without filter: VLISN = Vs’ IL = 20 lg(Vs/Vs’) Characteristics of filter Vs’ < EMI limit L EMI filter design tool developed by DPEC can help engineers to design filter easily. 14
4. 雜散電容的定義與測試方法? C 1: Switch to Heatsink C 2: Heatsink to Ground C 3: Secondary to Ground CPS: Transformer Parasitic Capacitance Cps is a key parameter to be minimum. The impedance analyzer can not be used to measure the Cps because of the transformer shielding and non-constant voltage distribution along the primary winding turns. 15
Cps Test Device Shielding Step 1: Getting the C-EMI curve Shielding Step 2: Getting the Cps with interpolation 16
ADP-10 UB Ø Thailand transformer TP – EMI passed TF – EMI failed ØTaiwan transformers are similar to the yellow curves. v Cps is a key factor for EMI level v Cps can be tested by our fixture 17
Magnetics Design Problem 18
1. Design tools中也有AC WINDING LOSS的分析程式, 是否 可告訴我們原計算公式為何? 有哪些是必要的影響參數? Ø For copper foil 1 D Dowell Model Wcu Ø For solid wire Key parameters: f, D, Wcu, structure (H), current waveform 19
2. Design tools是否可加入漏感的計算及告知我們影響參數有哪些? Ø Leakage calculation by out tool Ø Effect factor From a circuit point of view, the energy storage capability of the magnetic field between the windings is called leakage inductance. Leakage Energy = H Simple, sandwich B Air, low u core P Low u core Space between windings S 20
3. 當X’FMR GAP過大時, 圈數比的測量將會失真, Design tools 是否可加入計算功能, 告知我們當GAP多大時? 會產生此現象!! i 1 i 2 Lk Lp im V 1 Ø If Ls is low enough N 1 Lm Ls N 2 V 2 Ø If Ls is relative high If Lk<<Ls, the effect of Lk can be neglected. If gap is high, Lm will be low, and then the Lk can’t be neglected compared with the Lm. v Open Lp, measure Ls v Short Ls, measure Lk 21
4. Design tools是否可加入LLC線路的設計? Design parameter: Vin-min, Vin-max, Vin-nor, Vo, Io, fmin, Vc-max 1. Transformer effect turn ratio, n 5. Coupling coefficient, k 2. Resonant capacitance, Cs 6. Secondary inductance, L 2 3. Resonant inductance, Ls 4. Transformer magnetizing inductance, Lm 7. Transformer physical turn ratio, na 8. Highest operating frequency, fmax 22
Ø Model of Tr with Ls Effect turn ratio Np: Ns Lk Physical turn ratio Lm Common used model Measure method: Lk = Lpsshort Lm = Lp – Lk n = (Lm/Ls)1/2 n: 1 Convenient for circuit analysis model Simulation method: i L 1 L 2 U 1 Lp Lpsshort: short circuit inductance Lp: primary self inductance i L 1 L 2 U 2 Ln Ls: secondary self inductance Lk = (1 -k 2)*L 1 Lm = L 1 - Lk L 1, L 2, M (k) n = (Lm/L 2)1/2 23
Ø DC gain of output to input voltage D 1 Cs Ls Vo Cs n. Vo Ls Lm Lm n 2 R D 2 Different requirements (low profile, low cost, low loss…) need various LLC magnetics design. 24
Ø LLC magnetics design for low cost requirement Challeges of LLC magnetics: • Many magnetic components (Tr, Ls) • High AC component for Ls • High winding loss x Lm S n (P: S) Adjust gap position to obtain certain circuit performance Lk h P r h h Influence of gap position on magnetic parameters 25
5. Design tools是否可加入INVERTER X’FMR及低頻(60 Hz)變壓器的設計? Vi Vin Cs C 1 N Cp Rlamp Basic schematic diagram of the backlight inverter v Backlight inverter for a 14’’ notebook as an example 220 mm long CCFL • Ignition voltage of 1400 Vrms • Lamp voltage and current in burning state: 600 Vrms and 5 m. A C: DC blocking capacitor Cp: Lamp’s parasitic capacitor ( 15 p. F for 14’’ lamp ) Cs: Ballast capacitor, normal start with 47 p. F 26
Inverter Transformer Design Ø Circuit analysis Ls 1 Vin Cs Ls 2 1: N Vs Lm Vsec Rlamp Cp ( k: coupling factor, 0. 4~0. 7 ) Transfer primary components to secondary L Vs Cs Cp Vsec L, Lsec N, Lpri Rlamp Before ignition Vs L Vsec C ( fo = 55 k. Hz ) 27
Ø Transfer function Burning state: Ignition frequency Burning frequency 28
Ø Turns number of primary and secondary Ø Core and winding loss Core material: 3 C 91 (minimum loss around 50 degree) Winding design based on winding space in the bobbin Ø Temperature rise ( for frame&bar T) 29
The end ! Thanks ! 30
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