Research On Combined Full-bridge DC/DC Conversion System With Dual Mode Control

Full-bridge converters are widely employed in medium or high power applications.With the rapid development of power semiconductor devices,high frequency and soft-switching techniques,isolated full-bridge topology has become one of the most popular DC/DC conversion topologies.Therefore,it is important to further study full-bridge converters.In this paper,operation principle and control technology of full-bridge converter under dual-mode control are analyzed,and loss analysis and design of heat dissipation under different control modes are expatiated based on the combined full-bridge converter with parallel input and series output structure.According to the project demands,an isolated full-bridge DC/DC topology with input parallel output series is proposed.The operation of the full-bridge converter under phase shift and duty cycle control is analyzed.Then,the calculation of switching loss and conduction loss of primary power switches and secondary rectifier diode are given.Moreover,the efficiency of full-bridge converter under two control methods are compared and a dual-mode control technique is adapted in the final.In order to satisfy the functional requirements and performance indexes of the equipment,parameters of the main circuit of the full bridge DC/DC are designed.The design of key devices and the parameter values are given,including:input filter,input capacitor,power MOSFET,high frequency transformer,rectifier diodes,output inductor,output capacitor,etc.Based on the analysis of small-signal model of Buck circuit,a small-signal model of full-bridge DC/DC converter is established.The control parameter design process of two modes is given,and the stability and dynamic performance of the system are simulated by MATLAB.In order to optimize the overall efficiency of the converter,the efficiency advantage of the duty cycle control under light load and the soft switching advantage of the phase shift control under heavy load are combined.Finally,the software control architecture of dual mode control is given.To ensure the safe and reliable operation of the module,combined with the overload and heat dissipation problem encountered in engineering practice,this paper gives the design of full bridge converter cooling system,the test shows that the module heat design is effective and reasonable.Performance tests and functional tests on the prototype show that the main circuit parameters are suitable to meet the system performance.Thus,the validity of the circuit design and control scheme are verified.