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Published byKatelyn Soto Modified over 2 years ago

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Bi-directional DC-DC converter with Soft Switching Cell Student: Marek Ryłko Co-ordinators: Dr. Michael G. Egan Dr. John G. Hayes EPE-PEMC 2006, Portoroz 31 th Aug 2006

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Topology basics Introduce Soft Switching Cell 5 extra elements –2 aux. Switches –2 aux. Diodes –Autotransformer Hard Switching Soft Switching Topology Fundamentals BOOST ZCCM BUCK SS Boundary Turn ratio Duty – ideal Duty – damped Summary Further plans END

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Fundamentals of operation Continous conduction mode Fixed bus-voltages Operating frequency – above audible noise Maximum frequency limited by system topology and devices properties Efficiency 92-98% Hardware overcurrent protection Main switches operates as thyristor-dual Fully ZVCS switch-on main switches and snubber assisted switch-off ZCS switch-on and ZVCS turn-off of auxiliaries Main diodes reverse recovery limited by soft-switching cell inductance Topology Fundamentals BOOST ZCCM BUCK SS Boundary Turn ratio Duty – ideal Duty – damped Summary Further plans END

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Main inductor current Resonant ind. current Main switch current Flywheeling diode current Pole voltage Low voltage bus current Main inductor voltage Basic waveforms - BOOST Topology Fundamentals BOOST ZCCM BUCK SS Boundary Turn ratio Duty – ideal Duty – damped Summary Further plans END

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Main inductor current Resonant ind. current Main switch current Flywheeling diode current Pole voltage Low voltage bus current Zero Current Crossing Mode Basic waveforms - ZCCM Topology Fundamentals BOOST ZCCM BUCK SS Boundary Turn ratio Duty – ideal Duty – damped Summary Further plans END

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Main inductor current Resonant ind. current Main switch current Flywheeling diode current Pole voltage Low voltage bus current Main inductor voltage Basic waveforms - BUCK Topology Fundamentals BOOST ZCCM BUCK SS Boundary Turn ratio Duty – ideal Duty – damped Summary Further plans END

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Soft Switching boundary Topology Fundamentals BOOST ZCCM BUCK SS Boundary Turn ratio Duty – ideal Duty – damped Summary Further plans END Pole voltage swing (boost): Minimum value is achieved for: Pole voltage must reach zero: Soft Switching boundary is:

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Transformer turn ratio Presented boundary for soft switching refer to auxiliary voltage V S Damp resistance is present R d and take part as voltage drop Initial conditions are significant factor when main current is large Diodes voltage drop affect soft switching Voltage swing must be overestimated to take into account main-switch turn- on time Topology Fundamentals BOOST ZCCM BUCK SS Boundary Turn ratio Duty – ideal Duty – damped Summary Further plans END

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Duty factor Hard switching (square pole voltage) Soft switching r r = 0 (deformation of rising and falling edge) Because bus voltages are fixed, the duty factor depends on main inductor current as derivative of average value of pole voltage Topology Fundamentals BOOST ZCCM BUCK SS Boundary Turn ratio Duty – ideal Duty – damped Summary Further plans END

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System characteristic DvsI Topology Fundamentals BOOST ZCCM BUCK SS Boundary Turn ratio Duty – ideal Duty – damped Summary Further plans END

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Damped Cell – non ideal case r r 0 Damped cell Duty factor Topology Fundamentals BOOST ZCCM BUCK SS Boundary Turn ratio Duty – ideal Duty – damped Summary Further plans END

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System characteristic DvsI Topology Fundamentals BOOST ZCCM BUCK SS Boundary Turn ratio Duty – ideal Duty – damped Summary Further plans END

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Difference between ideal and damped system Topology Fundamentals BOOST ZCCM BUCK SS Boundary Turn ratio Duty – ideal Duty – damped Summary Further plans END

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Summary of soft switching system EMI improvement Good efficiency Decreased switching losses Distributed heat radiation Silent operation (over audible frequencies) No significant volume improvement More complex system Gain affected due to cell operation Topology Fundamentals BOOST ZCCM BUCK SS Boundary Turn ratio Duty – ideal Duty – damped Summary Further plans END

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Further research plan Development of systems above 10kW Compare with other bi-directional topologies –Interleaved, multiphase converters –Comparison of high ripple current and low ripple current cases –Investigation of IGBT operation in soft-switched regimes –MOSFETs in interleaved systems for high power –Inductor design –Coupled inductor approaches –Fully resonant approach –Hardware, FPGAs for control –Conference papers Topology Fundamentals BOOST ZCCM BUCK SS Boundary Turn ratio Duty – ideal Duty – damped Summary Further plans END

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THE END Thank you for your attention! Topology Fundamentals BOOST ZCCM BUCK SS Boundary Turn ratio Duty – ideal Duty – damped Summary Further plans END

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