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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
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Some basic concepts Load
Input rectifiers and capacitor produce Pulsating input current Harmonic currents are generated Power eLab HKU Prepared by Franki Poon
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A conventional method A boost converter and a DC/DC converter Ipfc Idc
Power eLab HKU Prepared by Franki Poon
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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
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Is single stage design always better?
Let us take a look Power eLab HKU Prepared by Franki Poon
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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
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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
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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
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Our new idea Boost + Asymmetric half-bridge with soft switching
DMpfc > DM2 M1 Mpfc M2 Power eLab HKU Prepared by Franki Poon
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Zero voltage state - M2 M1 turn off then . . Power eLab HKU
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Zero voltage state - Mpfc
After M2 turn on Power eLab HKU Prepared by Franki Poon
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Two separate converters
M2 turn on Mpfc turn on Power eLab HKU Prepared by Franki Poon
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Zero voltage state – M1 M2 turn off Mpfc turn on Power eLab HKU
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One cycle on asymmetric
M1 turn on Mpfc turn on Power eLab HKU Prepared by Franki Poon
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One cycle on PFC M1 turn on Mpfc turn off Power eLab HKU
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It’s great, but . . . No control for PFC !! If DMpfc < DM2
Power eLab HKU Prepared by Franki Poon
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After all – small Maux added
For all DMpfc and all DM2 M1 Maux Mpfc M2 Power eLab HKU Prepared by Franki Poon
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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
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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
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Two diodes are used to clamp ringing
Practical circuit – O/P 250uH IRF840A Two diodes are used to clamp ringing STD5NM50 12uH 8uH STPS12NM50 STPS12NM50 Power eLab HKU Active Diode Prepared by Franki Poon
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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
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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
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ZVS on M2 Power eLab HKU Prepared by Franki Poon
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ZVS on Mpfc Power eLab HKU
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ZVS on Mpfc & M2 Power eLab HKU
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Losses and Efficiency < 1W at no load 91% efficiency 12V@10A
Power eLab HKU Prepared by Franki Poon
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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
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