Design And Parallel Research Of Phase Shifted Full Bridge Converter

In order to adapt to today’s increasing demand on efficiency, the power level and density, this project intends to design a multi-module parallel power system and meet the various indicators with Suitable circuit topology and control method.Comparing the advantages and disadvantages of various isolation topology, select phase-shifted full-bridge as power system topology. Combined with the working principle of phase-shifted full-bridge converter, the duty cycle loss and soft switching implementation of key problems are analyzed and analysis the ZVS(Zero Voltage Switch) implementation in different conditions of the lagging arms. Finally, the phase-shifted full-bridge converter are modeled, and gives the small signal model and its open-loop transfer function.Completed the design of parameters and device selection of the main circuit. Using UC3875 as the core chip of the control system, and use the peak current mode as the control mode, completed the design of control circuit. In order to reduce the ripple of output voltage and output current, the ripple cancellation strategy based on coupled inductors are studied, and completed the design of ripple cancellation circuit. In order to verify the circuit can work stably and reliably, we have the stability analysis and sof tware simulation for it.According to the requirements of phase-shifted full-bridge converter, based on the analysis of the principle of parallel current sharing, completed the modeling and analysis of maximum current automatic current sharing and inner-loop current control method, and use the inner loop regulation method to complete the design. Finally in order to verify the parallel system can work stably and reliably, we have the simulation for it.Finally we design the hardware circuit and do the experi ment for the single module circuit and the parallel system, test the efficiency of the parallel system. The conduction of abundant simulations and experiments has proved the feasibility of design in this paper. No matter the load is constant or varying, the circuit can work properly. The parallel system can reach 3000 W when it works satble and reliable and its power and efficiency can meet the design requirements.