Design Of Single Phase AC/DC Power Supply For Medium Power

Power supply is responsible for the important supply of the entire system,whether it can be safe and reliable work will directly affect the performance of the whole system.With the development of technology,the performance requirements for power supply are getting higher and higher,switching mode power supply has replaced the traditional linear power supply in many areas and has become more and more widely used because of its high efficiency,small size,light weight,high degree of integration.Based on research of the theory and key technologies of switching mode power supply,combined with the characteristics of Flyback power conversion circuit,a single phase AC/DC power supply for medium Power density is designed in this article.The power supply can provide a 35 W 24V output,which can maintain a constant starting time for universal input and adjust the duty cycle to the change of the input voltage in order to ensure a stable output voltage.According to the requirements of the design,the working mechanism and control mode of the Flyback topology are analyzed,and the overall circuit structure of the system is designed.A set of design process is summarized,which has universal applicability in the flyback high frequency transformer.The parameter calculations of the high frequency Flyback transformer for this design are completed.According to electromagnetic compatibility and security requirements,the design of EMI filter circuit,input and output filter circuit,the protection circuit and RCD clamp Circuit have been completed to ensure the overall circuit performance and security.Based on the view of control stability and security,UC3842 is selected as the main control chip,and the feedback and control module is constructed by PC817 and TL431.In order to keep the constant start-up time,and to ensure the controllability of the system loop gain,a new chip startup circuit and feedback circuit for UC3842 is designed.The loop compensation theory is briefly analyzed,and the structure of the compensation circuit by using TL431 is given.The design is modeled and simulated by LTspice and Matlab,the simulation waveform is analyzed.The rationality of the design parameters is verified.In the simulation analysis,the voltage accuracy is within the error range of 1%,which shows high voltage stability;load adjustment rate is-1.1%,meet the design requirements of ±3%;the ripple of output voltage is 70 m V,the ripple coefficient is 0.3%,meet the design requirements the index is less than 1%.All of the circuit modules of the power supply show good applicability,each module can work stably in the preset working mode,and achieve the expected functional requirements.The simulation results show: the switching mode power supply which designed in this article has good stability,less ripple,low load regulation rate and high efficiency,and has high application value.