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Ripple EMI cancellation techniques

Power e Lab HKU. Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 1. Ripple EMI cancellation techniques. Franki N.K. Poon Power Electronics Laboratory, Hong Kong University nkpoon@eee.hku.hk.

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Ripple EMI cancellation techniques

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  1. Power eLab HKU Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 1 Ripple EMI cancellation techniques Franki N.K. Poon Power Electronics Laboratory, Hong Kong University nkpoon@eee.hku.hk

  2. Power eLab HKU Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 2 What is it all about ? • Forget about traditional filtering • Figure out ways of canceling input ripple current • Using ideal circuit elements Nullator and Norator pair to start analysis • Generalization of active cancellation approaches • Passive cancellation methods

  3. Power eLab HKU Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 3 First of all –ideal nullor element v = 0 i = 0 vnor inor Nullator Zero voltage Zero current Norator Any voltage Any curent Nullator and Norator Pair An example of applying nullator and norator pair

  4. Power eLab HKU iS1 C1 Zin C1 LISN iS1 Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 4 Complex or Simple ? Real Circuit AC Equivalent Circuit

  5. Power eLab HKU v = 0 i = 0 v = 0 i = 0 vnor = -vC1 i = 0 Zin C1 iS1 Zin C1 iS1 Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 5 Type I cancellation –Null the current Null the current Null by counter acting

  6. Power eLab HKU Zin C1 iS1 vnor = 0 inor = -iS1 Zin C1 iS1 Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 6 Type II cancellation –Null the voltage v = 0 i = 0 v = 0 i = 0 Null the current Null by counter acting

  7. Power eLab HKU Zin C1 iS1 v = 0 i = 0 Zin C1 iS1 Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 7 Type III cancellation –Null the current vnor = -vC1 inor = 0 v = 0 i = 0 Null the voltage Null by bypassing

  8. Power eLab HKU Zin C1 iS1 v = 0 i = 0 Zin C1 iS1 Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 8 Type IV cancellation –Null the current v = 0 i = 0 vnor = 0 inor = -iS1 Null the voltage Null by bypassing

  9. Power eLab HKU Zin C1 iS1 Zin C1 is1 Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 9 When idea meets practice–Type I

  10. Power eLab HKU Zin C1 iS1 Zin C1 is1 Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 10 When idea meets practice–Type II

  11. Power eLab HKU Zin C1 iS1 Zin C1 is1 Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 11 When idea meets practice–Type III

  12. Power eLab HKU Zin iS1 C1 Zin C1 is1 Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 12 When idea meets practice–Type IV

  13. Power eLab HKU Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 13 The Gain does matter

  14. Power eLab HKU Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 14 Zin does matter Zin=100W || 100mH Zin=0.1W Open-loop gain of sensing network/amplifier=2*10^6/(1+jf/15)

  15. Power eLab HKU Zin Zin C1 is1 C1 is1 vcancel = vC1 - + Zin C1 is1 vcancel = iS1*1/sC1 vcancel = vC1*1 - + - + Zin Zin C1 is1 C1 is1 Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 15 Feedback or Feedforward ? current to voltage Voltage to voltage

  16. Power eLab HKU Zin Zin C1 is1 C1 is1 Zin C1 is1 icancel = is1 Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 16 Feedback or Feedforward ? Zin C1 is1 icancel = is1 voltage to current Zin C1 is1 icancel = vC1*sC1 current to current

  17. Power eLab HKU C1 Zin C1 is1 vcancel = iS1*1/sC1 Z1 - + Z1 Zin Zin Zin vs1 C1 C1 is1 C1 is1 icancel = is1 Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 17 Passive & Feedforward

  18. Power eLab HKU Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 18 Feedback works, of course. no nothing 20uH Type I Type II Type III Type IV

  19. Power eLab HKU Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 19 Passive feedforward circuit works - work better? no nothing Current to voltage Current to current

  20. Power eLab HKU Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 20 Last page • Another way of suppressing noise current. • It is not confined to ripple current. • It can apply to all EMI (six) paths. • A generalization of active cancellation is discussed. • Passive cancellation circuit is also proposed. • A new area to explore

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