Download - 1182 apec2011
![Page 1: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/1.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
A ZVS-PWM Full-Bridge Converter with ReducedConduction Losses (T22)
IEEE Applied Power Electronics Conference and Exposition (APEC)Fort Worth, TX, USA
Dunisha Wijeratne & Gerry Moschopoulos
University of Western Ontario, London, ON, Canada
2011 March 9th
![Page 2: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/2.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Outline
• Introduction
![Page 3: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/3.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Outline
• Introduction
• Proposed Converter
![Page 4: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/4.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Outline
• Introduction
• Proposed Converter
• Steady-State Operation
![Page 5: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/5.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Outline
• Introduction
• Proposed Converter
• Steady-State Operation
• Converter Features
![Page 6: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/6.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Outline
• Introduction
• Proposed Converter
• Steady-State Operation
• Converter Features
• Design Guidelines
![Page 7: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/7.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Outline
• Introduction
• Proposed Converter
• Steady-State Operation
• Converter Features
• Design Guidelines
• Experimental Results
![Page 8: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/8.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Outline• Introduction
• Proposed Converter
• Steady-State Operation
• Converter Features
• Design Guidelines
• Experimental Results
• Conclusion
![Page 9: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/9.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Outline• Introduction
• Proposed Converter
• Steady-State Operation
• Converter Features
• Design Guidelines
• Experimental Results
• Conclusion
![Page 10: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/10.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Introduction• Generally there is a need to design the fastest, most efficient and compactpower converter.
• With soft switching in the switches (e.g. ZVS) it is possible to operatethe converter with high switching frequencies.
• Under light load conditions, MOSFETs cannot turn on with ZVS as thereis insufficient current to discharge Coss.
• Many researchers, therefore, have proposed variations on the basicZVS-PWM-FB topology to extend the load range.
![Page 11: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/11.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Introduction• Some topologies use extra passive components to generate current in theconverter’s primary side to discharge Coss of MOSFETs;
• But any efficiency gain is offset by additional conduction losses.
![Page 12: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/12.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Introduction• Another approach is to add active components to the standard topology.
• Current needed to discharge Coss of MOSFET at light loads is generatedwithout increasing conduction losses because the auxiliary circuit conductsonly for a shorter duration.
• None of these approaches decrease conduction losses.
![Page 13: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/13.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Introduction• Therefore, zero-voltage-zero-current-switching (ZVZCS) PWM FBconverters have been proposed.
• A passive auxiliary circuit extinguishes circulating current in thetransformer primary.
• ZCS, however, prevents the lagging leg switches turning on with ZVS.• As a result, IGBTs (which have lower Coss than MOSFETs) are preferredover MOSFETs.
• But IGBTs are slower than MOSFETs - switching frequency must belimited.
![Page 14: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/14.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Proposed Converter• The ZVZCS FB section consists of switches S1-S4, main transformer(Tm), secondary side rectifier diodes, Aux. 2 and the output filter.
• Aux. 1: Switches Sa, Sb, blocking diodes DSa , DSb , resonant componentsLr, Cr and transformer (Ta).
• Aux. 2: Capacitor Cx and diodes Dc, Dd.
![Page 15: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/15.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Proposed Converter• Aux. 1: Becomes active just before a lagging leg switch is turned on andlasts till iLr = 0.
• Aux. 1: Provides a path for Coss of the lagging leg switches to discharge,so that they can be turned on with ZVS.
![Page 16: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/16.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Steady-State OperationMode 1 (t0 < t < t1)
• Converter behaves as a standardZVZCS FB converter.
• Mode forms part of the powertransfer mode.
• iin flows through Llk and Llkresonates with Cx.
• Cx reaches its peak voltage at theend of the mode.
![Page 17: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/17.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Steady-State OperationMode 2 (t1 < t < t2)
• Vin is applied entirely across theprimary winding of Tm.
• Cx remains at its peak voltage.
![Page 18: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/18.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Steady-State OperationMode 3 (t2 < t < t3)
• S1 is turned off at t = t2.
• ip charges and discharges switchcapacitors CS1 and CS3
respectively.
• Discharging and charging is linearuntil the primary voltage of Tmdrops to a level that equals thereflected Cx voltage.
![Page 19: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/19.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Steady-State OperationMode 4 (t3 < t < t4)
• The non-linear dead time betweenS1 and S3.
• Tm’s primary voltage decreases butthe secondary side rectifier voltageis held by Cx.
• The difference of Vin and Tmprimary voltage is applied acrossLlk.
• ip starts to decrease.
• When ip falls below the reflectedload current, Cx starts to dischargeto bridge the gap.
![Page 20: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/20.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Steady-State OperationMode 5 (t4 < t < t5)
• S3 can be turned on with ZVS.
• Converter starts to freewheel.
• Towards the end of the mode, ip= 0 and S2 can be turned offwith ZCS at t = t5.
![Page 21: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/21.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Steady-State OperationMode 6 (t5 < t < t6)
• After S2 is turned off, Sa can beturned on with ZCS.
• Sa allows CS4 to discharge intoAux. 1.
• Part of iin charges CS2 and theremainder enters Tm.
• CS4 is fully discharged at t = t6.
![Page 22: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/22.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Steady-State OperationMode 7 (t6 < t < t7)
• At t = t6, iin = ip.
• Vin is applied across Llk; thus ipincreases linearly until it equalsthe reflected load current.
• Current in the secondary side ofTm freewheels.
• In Aux. 1, iLr comprises of theTm’s primary current ip and thecurrent of DS4 .
![Page 23: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/23.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Steady-State OperationMode 8 (t7 < t < Ts/2)
• ip starts to increase beyond Io/nm.
• Resonance of Cr and Lr decreasesiLr .
• As ip is increasing while iLr isdecreasing, the window ofopportunity for the lagging legswitches to turn on with ZVS laststill ip <= iLr.
• At t = Ts/2, iLr = 0, Sa is turnedoff with ZCS sometime thereafter.
![Page 24: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/24.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Converter Features
• Main switches:• S1-S4 turn on with ZVS.
• S2 and S4 turn off with ZCS.• Aux. switches:
• Sa and Sb turn on and off with ZCS.
![Page 25: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/25.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Converter Features
• Freewheeling current in Tm is extinguished so that conduction losses arereduced.
• Llk in Tm can be minimized; thus duty cycle loss is minimized.
![Page 26: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/26.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Converter Features
• Aux. 1 conducts for a very short duration.
• Its components can be implemented with lower power rated devices.
• When Aux. 1 is implemented with a small transformer, energy inthe circuit can be transferred to the load.
![Page 27: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/27.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Design Guidelines
![Page 28: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/28.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Design GuidelinesMain transformer (Tm) turns ratio nm
• Since the input to output voltage conversion ratio is fixed, nm should beselected simultaneously with the duty ratio D.
• nm should not be too low as that will increase the current in Tm and theconverter will need to be in the freewheeling mode for a longer time tocompletely remove iLlk .
• A higher nm can have a negative influence on the voltage regulation ofthe converter.
![Page 29: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/29.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Design GuidelinesMain transformer (Tm) Leakage Llk
• Lo aids ZVS operation in S1 and S3.• Therefore Llk can be minimized.• A lower Llk will decrease the duty ratio loss from the primary to thesecondary side.
• A low Llk also aids the ZCS.
![Page 30: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/30.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Design GuidelinesAux. 2 Capacitor(Cx)
• Main function of Cx is to create a counter voltage across Llk to ensurethat the primary current decreases to zero within the freewheeling time.
• If Cx is too small, it will not have sufficient energy stored in it todischarge Llk.
• If Cx is too big, then unnecessary conduction losses will occur in Aux. 2.
![Page 31: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/31.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Design GuidelinesAux. 1 Inductor(Lr)
• Higher Lr increases, the characteristic impedance in Aux. 1 and thusreduces the peak current stress.
• This allows use of lower current rated switches in Aux. 1.• A lower Lr in Aux. 1 means the time at which iLlk = iLr in Mode 2 getscloser to t2; hence the window of opportunity narrows, making the ZVSoperation difficult.
![Page 32: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/32.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Experimental ResultsConverter Design
Design SpecificationInput voltage: 380 Vin
Output voltage: Vo = 48Vdc
Output power: 500 kW
Switching frequency: fs=125 kHz
Maximum power: Po,max=500 W
Converter ParametersTm turns ratio: nm= 4
Ta turns ratio: na= 0.1
Aux 2 capacitor: Cx=0.1 µF
Aux 1 capacitor: Cr=100 nF
Aux 1 inductor: Lr=1 µH
![Page 33: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/33.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Experimental ResultsLagging Leg Switching
• Lagging leg switches turn on with ZVS and turn off with ZCS.
• Current in the switch is negative so that it has a ZVS turn on.
• Current in the switch is zero as the freewheeling current is extinguishedbefore it is turned off, so that it has a ZCS turn off.
![Page 34: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/34.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Experimental ResultsLeading Leg Switching
• Leading leg switches turn on with ZVS.
![Page 35: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/35.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Experimental ResultsAux. 2 Diode Waveforms
(a) Dc voltage and current (b) Dd voltage and current.
• Voltage and current waveforms of the two diodes in Aux. 2.
• Both diodes Dc and Dd turn on and off softly.
![Page 36: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/36.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Experimental ResultsAux. 1 Switch Waveform
• The top figure is the switch voltage, the middle is the gate pulse and thebottom is the switch current.
• Switch turns on and off with ZCS.
• Aux. 1 conducts current for only a very short duration.
![Page 37: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/37.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Conclusion• A novel dc-dc PWM ZVS FB converter was proposed.
• The converter is a ZVZCS PWM converter with fewer conduction lossesthan the standard ZVS-PWM FB converter, but with an extended ZVSload range.
• Features:• All the benefits of ZVZCS converters.• All switches operate with ZVS.• Can be implemented with MOSFETs hence operating in high switching
frequencies.
• The operation of the converter, general design guidelines and featureswere explained and its feasibility is proved with experimental resultsobtained from a lab prototype.
![Page 38: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/38.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
T
![Page 39: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/39.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Th
![Page 40: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/40.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Tha
![Page 41: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/41.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Than
![Page 42: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/42.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Thank
![Page 43: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/43.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Thank y
![Page 44: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/44.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Thank yo
![Page 45: 1182 apec2011](https://reader034.vdocuments.mx/reader034/viewer/2022042615/55b89cdbbb61ebf4068b45ee/html5/thumbnails/45.jpg)
Outline Introduction Proposed Converter Operation Features Design Guidelines Experimental Results Conclusion
Thank you