Research On And Design Of A Modular Parallel-input DC-DC Converter For High Voltage Power Supply

As the development of power electronics technique,the demand of high-voltage DC-DC converter in high-voltage and high-power application continues to increase in recent years,and the converter needs to have high-reliability,high power density and low cost.Traditional non-modular high-voltage DC-DC converters have the disadvantages of large input and output current ripple fluctuation,large voltage stresses,losses of the power devices,high electromagnetic interference,and other defects,the input-parallel output-series(IPOS)converter is very suitable to address the problems above.The main advantages of the IPOS converter include: the small volume and high power density;low voltage and current stresses of the power devices;the simple design of the converter module leading to reduce the development cost and shorten the development cycle etc.The main circuit of the basic module employs full-bridge series-parallel resonant converter,which has good characteristics of frequency-voltage regulation,high output voltage,and simple control method working under the discontinuous conduction mode(DCM).First,this thesis analyzes the working principle and switch states of modular converters,gives the mathematical description and circuit characteristics of the resonant converter in DCM mode.The resonant parameters of basic module are designed,and the characteristic of frequency-voltage regulation of unit module is verified through simulation and experiment.Then,this thesis illustrates the operating principles and the characteristics of IPOS converter,which is consisted by two basic modules.And this thesis detailly analyzes the stability of the system,and reveals the relationship between the input current sharing and the output voltage sharing of the modules in IPOS converter.Through the analysis in this paper,input current sharing is automatically achieved as long as output voltage sharing is controlled.The impact of resonant parameters of the basis module to the output voltage sharing is analyzed,which is verified through simulation Interleaving technique is adopted in the system,with the ripple canceling effect,the input current ripple and the output voltage ripple can be reduced.On the basis of theoretical analysis,the control strategy of the system is proposed in this paper.Finally,the hardware of the modules in IPOS converter is designed,including soft-starting circuit,driving circuit and sampling circuit.The simulation results and experimental results are analyzed to demonstrated the correctness of the research.