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

2. 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 What is it all about ? Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 2 Power e Lab HKU

3. v = 0 i = 0 Nullator Zero voltage Zero current v nor i nor Norator Any voltage Any curent Nullator and Norator PairAn example of applying nullator and norator pair First of all – ideal nullor element Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 3 Power e Lab HKU

4. LISN C1C1 i S1 Z in C1C1 i S1 Complex or Simple ? Real CircuitAC Equivalent Circuit Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 4 Power e Lab HKU

5. v = 0 i = 0 v nor = -v C1 i = 0 Z in C1C1 i S1 Type I cancellation – Null the current Null the currentNull by counter acting Z in C1C1 i S1 v = 0 i = 0 Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 5 Power e Lab HKU

6. v = 0 i = 0 Z in C1C1 i S1 v nor = 0 i nor = -i S1 Z in C1C1 i S1 Type II cancellation – Null the voltage Null the current v = 0 i = 0 Null by counter acting Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 6 Power e Lab HKU

7. v nor = -v C1 i nor = 0 Z in C1C1 i S1 v = 0 i = 0 Z in C1C1 i S1 Type III cancellation – Null the current Null the voltage v = 0 i = 0 Null by bypassing Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 7 Power e Lab HKU

8. Z in C1C1 i S1 Type IV cancellation – Null the current Null the voltage v = 0 i = 0 Null by bypassing v = 0 i = 0 Z in C1C1 i S1 v nor = 0 i nor = -i S1 Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 8 Power e Lab HKU

9. Z in C1C1 i S1 When idea meets practice – Type I Z in C1C1 i s1 Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 9 Power e Lab HKU

10. Z in C1C1 i S1 When idea meets practice – Type II Z in C1C1 i s1 Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 10 Power e Lab HKU

11. Z in C1C1 i S1 Z in C1C1 i s1 When idea meets practice – Type III Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 11 Power e Lab HKU

12. Z in C1C1 i S1 Z in C1C1 i s1 When idea meets practice – Type IV Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 12 Power e Lab HKU

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

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

15. Z in C1C1 i s1 Z in C1C1 i s1 Z in C1C1 i s1 v cancel = v C1 - + Z in C1C1 i s1 v cancel = i S1 *1/sC 1 - + Z in C1C1 i s1 v cancel = v C1 *1 - + Feedback or Feedforward ? Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 15 Power e Lab HKU

16. Z in C1C1 i s1 Z in C1C1 i s1 Z in C1C1 i s1 i cancel = i s1 Z in C1C1 i s1 i cancel = v C1 *sC 1 i s1 Z in C1C1 i cancel = i s1 Feedback or Feedforward ? Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 16 Power e Lab HKU

17. Z in C1C1 i s1 v cancel = i S1 *1/sC 1 - + i s1 Z in C1C1 i cancel = i s1 Z in C1C1 i s1 C1C1 v s1 Z in C1C1 Z1Z1 Z1Z1 Passive & Feedforward Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 17 Power e Lab HKU

18. Feedback works, of course. no nothing20uHType I Type II Type III Type IV Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 18 Power e Lab HKU

19. Passive feedforward circuit works - work better? no nothingCurrent to voltage Current to current Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 19 Power e Lab HKU

20. 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 Last page Prepared by Franki Poon EMC and Design Issues for Switching Power Supplies 21/June/03 www.eee.hku.hk/power_electronics_lab/ 20 Power e Lab HKU