Research And Design Of High Power Factor Switching Power Supply

With the development of power electronics tec.hnology,the performance requirements of switching power supply become more and more strict.But that input rectifier circuit of the traditional switching power supply is uncontrollable full bridge rectifier.Although the circuit design technology is ordinary,but it can cause serious distortion of input current,harmonic content is large,low power factor,bring seious pollution and energy waste to the power grid.In order to solve these problems,PWM controlled rectifier is used to replace the uncontrolled rectifier in the previous stage of the switching power supply,which makes the input current sinusoidal and harmonic content is low,so as to improve the power factor of the Switching power supply.Based the working principle of the single-phase PwM rectifier circuit in the front stage of the switching power supply is analyzed,and the mathematical model described by the switching function is established.The control strategy of triangular wave current comparison is proposed,and the sinusoidal current at the input side is realized by SPWM modulation technology Secondly,the working principle and working mode of the flyback c.irc.uit with post-stage power conversion of switching power supply are analyzed and studied,the flyback circuit is designed to work in DCM working mode,and the current-mode control mode is adopted to realize double closed-loop control of the flyback circuit.According to the circuit structure and control strategy proposed by the system circuit,MATLAB/Simuaink is used as a mathematical tool to establish a simulation model for verification.the results show that the network side current and the network side voltage achieve in-phase and regular sine wave shape,and the harmonic content is.small,the circuit output,voltage is stable,change the input voltage and load,the system ou.tput will quickly restore the set value.Finally,according to the simulation parameters and existing conditions,a switch power supply control system based orn DSP control is built.Comprise a main circuit,a voltage and current sampling condition circuit,an isolation driving circuit and other auxiliary circuits.According to combinated test of hardware and software.The experimental results show that the ripple of the output voltage,the power factor of the switching power supply and the anti-disturbance ability are all within the design requirements,which proves the rationality and feasibility of the designed hardware parameters and control strategy.