A ZVS approach for AC/DC converter with PFC PowereLab HKU A ZVS approach for AC/DC converter with PFC The Power Electronics Lab., Hong Kong University N. K. Poon C. P. Liu M. H. Pong Speaker Bryan M. H. Pong Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 1

Some basic concepts Load Input rectifiers and capacitor produce Pulsating input current Harmonic currents are generated Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 2

A conventional method A boost converter and a DC/DC converter Ipfc Idc Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 3

A popular method among researchers Ipfc Idc Single stage design which combines the boost and the DCDC converters Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 4

Is single stage design always better? Let us take a look Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 5

Why two-stage design? Advantage Losses  Ipfc2 + Idc2 Fix DCDC input voltage Controllable bulk voltage Disadvantage Need two controllers One more MOSFET Ipfc Idc Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 6

Why single-stage design? Advantage One controller One MOSFET less Disadvantage Losses  (Ipfc + Idc)2 High Idc at low line Higher Ipfc High current stress High voltage stress Ipfc Idc Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 7

Good reasons for two-stage Advantages Losses  Ipfc2 + Idc2 Fix DCDC input voltage Controllable bulk voltage Disadvantages Need two controller One more MOSFET Single Stage Advantages One controller One MOSFET less Disadvantages Losses  (Ipfc + Idc)2 High Idc at low line Higher Ipfc High current stress High voltage stress Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 8

Our new idea Boost + Asymmetric half-bridge with soft switching DMpfc > DM2 M1 Mpfc M2 Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 9

Zero voltage state - M2 M1 turn off then . . Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 10

Zero voltage state - Mpfc After M2 turn on Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 11

Two separate converters M2 turn on Mpfc turn on Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 12

Zero voltage state – M1 M2 turn off Mpfc turn on Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 13

One cycle on asymmetric M1 turn on Mpfc turn on Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 14

One cycle on PFC M1 turn on Mpfc turn off Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 15

It’s great, but . . . No control for PFC !! If DMpfc < DM2 Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 16

After all – small Maux added For all DMpfc and all DM2 M1 Maux Mpfc M2 Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 17

Final timing arrangement ZVS too M2 gate drive A M1 gate drive B Maux gate drive Mpfc gate drive VA = VB VMaux_ds = VA-VB =0 Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 18

guarantee a path for Laux current when M2 off at any time Practical consideration M1 Maux Mpfc Doff M2 guarantee a path for Laux current when M2 off at any time Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 19

Two diodes are used to clamp ringing Practical circuit – O/P 12V@10A 250uH IRF840A Two diodes are used to clamp ringing STD5NM50 12uH 8uH STPS12NM50 STPS12NM50 Power eLab HKU Active Diode Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 20

Simplified timing circuit M2 gate O/P Sync M1 gate Maux gate Sync L4981 Mpfc gate O/P Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 21

How does it look? A 120W, 12V10A AC adapter Width = 12.6cm Depth = 6.3cm Height = 1.9cm Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 22

ZVS on M2 Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 23

ZVS on Mpfc Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 24

ZVS on Mpfc & M2 Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 25

Losses and Efficiency < 1W at no load 91% efficiency 12V@10A Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 26

Finally . . . Simple Boost + Asymmetric Half-bridge configuration – Good Combination. All ZVS behaviors – Very little added cost. Two separate converter – Easy to control Active diode can be incorporated – <1W no load power Simple PWM controller – simple ASIC Power eLab HKU Prepared by Franki Poon www.eee.hku.hk/power_electronics_lab/ 27