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Alland Chee, Elvis Lin, Joe Wong and Jeffrey H. Hwang

Design a 100W PFC Boost Inductor. Alland Chee, Elvis Lin, Joe Wong and Jeffrey H. Hwang. Criteria of Selection. Size Efficiency Cost. R =S: [ ] Magnetic Reluctance=The resistance of a material to a magnetic field

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Alland Chee, Elvis Lin, Joe Wong and Jeffrey H. Hwang

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  1. Design a 100W PFC Boost Inductor Alland Chee, Elvis Lin, Joe Wong and Jeffrey H. Hwang

  2. Criteria of Selection Size Efficiency Cost

  3. R=S: [ ] Magnetic Reluctance=The resistance of a material to a magnetic field Φ: [Weber] Magnetic Flux=A measure of quantity of magnetism. B: [Tesla]=[ Gauss] Magnetic Field=Flux Density=Magnetic Induction H: [ ] Magnetic Field Strength=Magnetic Force=MMF per length 1[Tesla]=1[Weber/Meter2]=104 [Gauss]=1[Newton/(Ampere x Meter)] 1[Weber]=1[Wb]=108Maxwell [L]=1[henry]=1[Volt x Sec/Ampere]=1[Wb/Amp] μ0=Air Permeability Constant=4π x 10-7 [Tesla Meter/Ampere] Review Important Magnetic VariablesandImportant Magnetic Constants

  4. R=mmf /ΦB=NI/ΦB= ιm/(Acμ) Re=Rl + Rair= ιm/(Acμ) + ιair/(Acμair)= ΦB= L=N ΦB/I=N2/Re= B=μ H= μ x mmf/leff= ΦB/Ac= μ x N x I/leff= L x I/(N x Aac) Important Magnetic Formula

  5. Bmax= Constant @ given material PC95:Bmax~350mT PC44:Bmax~300mT PC40:Bmax~270mT

  6. NImax= Constant @ lair, air gap is fixed

  7. Sundest, MPP, Ferrite…?Experiment 1st:Selecting the best Magnetic Material

  8. Selecting Magnetic Materials Ferrite and MPP have the higher efficiency performance. Ferrite is our selection.

  9. Ferrite is our selection for Po=100W Ferrite is Cost Effective and Ferrite Core Loss (AC Loss) is much less DCR seems dominates the efficiency with Ferrite Core! Let us prove it here!

  10. 290uH or 1mH?Experiment 2nd:DCR and switching frequency is fixedWinding Factor is not optimal.

  11. With fixed DCR=0.46 ohm and fixed fsw=67.5Khz, Po=100 W and Vo=19V AC Adapter Higher Efficiency with Higher Inductor? but it is miss-leading!

  12. We have learned:Without the Space Limit,Higher inductance will have the higher efficiency.

  13. Should we go higher frequency to solve the space issue?Experiment 3th:With RM8 and RM6, we fixed crest factor, r=0.95andWinding Factor isOptimal with the giving bubbin.

  14. Po=100W, PFC boost OnlyConstant r=crest factor=Ip-p/Irms=0.95 with Constant r=0.95 Higher Efficiency with Higher Inductance? Higher Efficiency with Lower Frequency? Again, it is miss-leading! From above data, to improve efficiency, we only know that we should reduce frequency to trade efficiency.

  15. We have learned:With the given space, frequency should be as low as possible before the core is saturated.The Lower Frequency provides the Higher Efficiency

  16. What will happen with fixed switching frequency?Experiment 4th:Optimal Winding Factor for RM8 and fsw = 67.5Khz

  17. fsw=67.5Khz with CM6800 100W demo board L=442uH is the Highest Efficiency one; Crest Factor, r~1

  18. fsw=100Khz with CM6800 100W demo board L=295uH is the Highest Efficiency one; Crest Factor, r~1

  19. fsw=100Khz with CM6800 100W demo board L=295uH is the Highest Efficiency one; Crest Factor, r~1

  20. fsw=67.5Khz with CM6805 100W AC Adapter L=295uH is the Highest Efficiency one; Crest Factor, r~1.55

  21. We have learned:Crest Factor, r~1 to 1.55L=442uH to 295uH for 67.5Khz and L=295uH for 100Khzgives the best efficiency;It means without saturating the coreReducing DCR,Reducing lg , Reducing N, all will improve the efficiency.

  22. Conclusion:Ferrite: PC95 RM8 (67.5Khz) --- > RM6 (100Khz)295uHwith CM6805 (PFC+PWM combo IC)

  23. lg = 24 mil N = 52.5 turns Pin max = 146.56W L = 400.58uH x 1.09 Al = 0.1584uH/turn^2 Ipeak at Sat = 2.3A DCR = 0.09 ohm P core loss ~ 0.39W at Pin max P copper loss ~ 0.228W at Pin max Total P loss ~ 0.62W at Pin max Wire Area = 0.44 mm^2 => AWG=21 442uH with fsw = 67.5Khz Vout = 220V, Po = 100W, RM8and PC 95

  24. lg = 20 mil N = 40.5 turns Pin max = 138.6W L = 285uH Al = 0.1738uH/turn^2 Ipeak at Sat = 2.178A DCR = 0.05 ohm P core loss ~ 0.39W at Pin max P copper loss ~ 0.12W at Pin max Total P loss ~ 0.51W at Pin max Wire Area = 0.57mm^2 =>AWG=20 295uH with fsw = 67.5Khz, Vout = 220V, Po = 100W, RM8 and PC 95

  25. lg = 32 mil N = 64.5 turns Pin max = 118.93W L = 229uH x 1.23 Al = 0.068uH/turn^2 Ipeak at Sat = 1.87A DCR = 0.19 ohm P core loss ~ 0.15W at Pin max P copper loss ~ 0.33W at Pin max Total P loss ~ 0.48W at Pin max Wire Area = 0.18mm^2 =>AWG=25 295uH with fsw > 100Khz, Vout = 220V, Po = 100W, RM6 and PC 95

  26. 100W AC Adapter without SREfficiency vs. LoadWith 295uH(RM8), 442uH(RM8) and 303uH(RM6)at fsw = 67.5Khz

  27. 100W AC Adapter without SREfficiency vs. VinWith 295uH(RM8), 442uH(RM8) and 303uH(RM6)at fsw = 67.5Khz Po=100W Po=66W

  28. 100W AC Adapter with SR and without SREfficiency vs. VinWith 442uH(RM8)at fsw = 67.5Khz Measure the Efficiency Data at the end of cables.

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