1. A Low Output Ripple DC to DC converter topology using voltage overlapping technique The Power Electronics Lab., Hong Kong University C. P. Liu N. K. Poon M. H. Pong SpeakerC.P.Liu Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 1

2. Low output ripple solutions – Interleaving Input voltage = 36V Duty cycle = 0.5 Ripple current p-p = 0A !! f 1x I pp L=300nH Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 2

3. Low output ripple solutions – Interleaving Input voltage = 72V Duty cycle = 0.25 Ripple current p-p = 20.833A ?? f 1x L=300nH I pp L=300nH Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 3

4. Low output ripple solutions – Interleaving f 1x L L I pp Ripple current vs. Input voltage Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 4

5. Low output ripple solutions – Single phase f 2x L = 266nH I pp Even better than Multi-phase Question: Why 266nH and freq = 2 x f ? Interleave converter Single phase converter Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 5

6. 2(1+1+1+1)=8(1+2+1+2)=6 One inductor reduces resistance 1 1 Ae 1 2 For same copper loss: N = 4/3 N = 1 For same flux density: L = 300nH L = (16/9 x 300/2) nH Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 6

7. Ultimate interleaving – 50%+50% = 1 2 Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 7

8. What if more than 50% ? Vp Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 8

9. VpVp VpVp VpVp No regulation - stupid! Vp Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 9

10. V p (1-D) VpVp D VpVp D Simplest Amplitude Modulator Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 10

11. Worlds first wide range & wide loading output capacitorless DCDC regulator. VaVa VbVb VoVo VoVo VaVa VbVb Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 11

12. More components than a already good interleaving converter ! ! Worlds first wide stupid DCDC regulator. Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 12

13. Isolated Overlap VS Isolated Interleave Compare with the more complicated approach Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 13

14. VoVo VaVa VbVb No perfect DC blocking capacitor Ripple voltage introduced VaVa VbVb Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 14

15. VoVo I Co Of course an O/P capacitor is needed Resonate current pulse VaVa VbVb Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 15

16. Final configuration – add a current source L s << L o LoLo L s1 L s2 I Ls2 VaVa VbVb I Ls1 Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 16

17. Overlapping + Sync-Rect I Ls2 VaVa VbVb I Ls1 L s1 L s2 Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 17

18. Overlapping + Active Diode 300 nH 50 nH 100 uF 50 nH 0.33 uF 36V-72V O/P Inductor current O/P diodes current Gate drive 2.5V@15A Efficiency = 88% O/P ripple = 50mV fs = 200kHz Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 18

19. Overlapping or Interleaving 300 nH 2A p-p 20.8A p-p 300 nH Same O/P Inductor Same 72V I/P voltage Same D=0.5 at 36V I/P Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 19

20. After all... Good reasons to look for more low output ripple configurations A simple configuration producing very low output ripple current is proposed ZVS of primary switches is possible Output ripple is independent on input voltage Low stress on MOSFET Good for low voltage high current applications Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 20

21. Potential application Intermediate bus in 48V system 2.8 x 4.5 inches 2 500W output 14V, 36A with tight regulation Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 21

22. Thank you Power e Lab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 22