Research On The Control Technology For Soft Switch DC-source

With the continuous innovation of power electronic power switch device, switching power supply is gradually moving towards the direction of high frequency, miniaturization,digitalization and intelligence. However, to improve the operating frequency of the switching power supply, it can increase the switching losses, reduce the efficiency of the switching power supply, and even lead to serious consequences. In order to solve the problem of switching losses, soft switching technology is widely used in the DC switching mode power supply,which has become a hot research topic at home and abroad. With the rapid development of ARM, DSP, digital control circuit has the advantages of simple structure, convenient control,high control accuracy, digital control technology has become the mainstream of switching power supply control, and gradually replace the traditional analog control. Based on several kinds of soft switch phase-shift full bridge analysis and comparison, choose the lag bridge ARM series diode ZVZCS phase-shift full bridge converter topology, the digital control mode based on ARM, transformation of phase-shift full bridge soft switching implementation and control technology is studied.In view of the problem of the voltage on the rectifier diode and the current waveform of the transformer,the cause of the oscillation is analyzed,and the solution of the auxiliary circuit is put forward. Through the detailed analysis of the main topology of the auxiliary circuit, the paper summarizes the conditions of zero current switching for the advanced bridge arm of the converter, and expounds the cause of the loss of the duty cycle of the transformer.Aiming at the problem that the traditional PI controller does not have the function of on-line auto setting function,the load voltage drop and the control effect is not ideal,the control strategy is proposed to combine the traditional PI control and fuzzy control with PI parameters.A small signal model of the phase shifted full bridge converter is derived by establishing the small signal model of the BUCK circuit. The design process of the current controller, voltage controller and fuzzy adaptive PI controller is presented. In order to verify the rationality of the controller design and the realization of the soft switch, the MATLAB simulation model is built.The simulation results show that the zero voltage switch and the lagging leg of the PI controller are less than the traditional PI controller.The digital control system based on STM32F407 is designed, which is based on the input and output of the converter. On the basis of this, a 1.2kW experimental prototype is built.Through the detailed analysis of the experimental waveforms, the conclusion is obtained that the zero voltage switch and the lagging leg of the advanced bridge arm are realized. The experimental results verify the correctness of the theoretical analysis and the rationality of the software and hardware design.