Design Of Wide Range Isolated Bidirectional SiC DC/DC Converter

DC/DC converters are widely used in various fields of production and life,such as new energy power generation,electric vehicles and rail transit.In the above case,the DC/DC converters are required to withstand a relatively wide input voltage,and the DC/DC converters are also required to ensure their high efficiency.In order to meet these requirements,a novel two-stage isolated bidirectional DC/DC converter based on phase-shifted isolated bidirectional DC/DC converter is designed,and the wide bandgap device SiC MOSFET is used as the main power switching device.Based on this,this thesis focuses on the application of SiC MOSFET,the topology of wide-range isolated bidirectional DC/DC converter and the overvoltage suppression of the switch caused by leakage inductance of the transformer.Firstly,the static and dynamic characteristics and some important parameters of SiC MOSFET and Si MOSFET are compared.According to the different characteristics of SiC MOSFET and Si MOSFET,the driving requirements of SiC MOSFET are analyzed,and the driving circuit is designed for the SiC MOSFET used in this thesis.Then the double pulse test is carried out to verify that the driver used in this thesis can meet the design requirements.Secondly,according to the requirement of wide range parameters of the system,a two-level topology is proposed to deal with this special working condition.Then,taking the voltage and current stress of the switch tube as the cut-in point,compared with the common power topology,the two-stage converter topology with the Buck/Boost converter as the input and the isolated bidirectional DC/DC converter as the output is determined.,and the working principle of the topology used is analyzed in detail,then the system scheme is designed according to the parameters.Finally,the simulation results show that the designed converter can meet the requirements of the system.Next,the influence of the leakage inductance of the transformer on the forward and reverse operation of the phase-shifted isolated bidirectional DC/DC converter is discussed.The formation process of the over-voltage spike of the secondary-side switch is analyzed in detail.In order to reduce the influence of leakage inductance in the commutation process,the active clamp is desigened to suppress the overvoltage of the switch tube.Then the working process of the active clamp is analyzed in detail,and the simulation is performed,the simulation results show that the active clamp circuit can eliminate the overvoltage of the switch.Finally,the transformer parameters,inductance and capacitance values of the converter are calculated according to the parameter requirements,and the main power devices of the converter are selected.The experimental prototype and control system are designed.Finally,the experimental prototype verifies that the system meets the design requirements,the function of the converter can meet the requirements of various working conditions,and the active clamp can effectively eliminate the switching tube overvoltage spike.