Design And Realization Of AC-DC Constant Current Source With High Power Factor

With the development of science and technology,a wide variety of electrical equipment into the power grid,the harmonic pollution of the power grid caused by the rectifier and filter circuit of these devices,and poor power factor,leading to low utilization of energy,so people have higher requirements for the power factor of the power supply,therefore,the power factor correction technology has been developed by leaps and bounds.At present,the passive power factor correction technique and the active power factor correction technology are widely used.In this paper,the structure,principle and characteristics of power factor correction technology are deeply studied.The AC-DC constant current source with simple structure,low cost and high power factor is designed,for driving LEDs or other place with high power factor and high current stability requirements.The design adopts single-stage flyback converter structure without input filter capacitor.When flyback converter is operating in discontinuous current mode(DCM),the power factor will be automatic correction.The design of high power factor constant current source is complete.Firstly,the principle and basic characteristics of single-stage power factor correction are analyzed in detail,and the negative effect of the input filter capacitor on the whole circuit is pointed out.Secondly,the control strategy of the design is described in detail.With the ARM-STM32 chip as the control core,the input voltage and the output voltage are sampling,and the sampled data is sent to ARM.The corresponding duty cycle pulse is generated by program processing,through the isolation drive circuit to control the turn on and turn off of the switch tube to make the output current stabilize,so as to achieve the purpose of high power factor and the intelligent control of output current.Then in the Simulink environment,the system model of the flyback converter with capacitor-less is established.The simulation results verify the feasibility and reliability of the control.Finally,according to the design requirements,the software program is complete and hardware circuit is built,through integrated hardware debugging with ARM-STM32 chip as the control core,the input voltage and the output voltage are sampling,and the sampled data is sent to ARM.The corresponding duty cycle pulse is generated by program processing,through the isolation drive circuit to control the turn on and turn off of the switch tube to make the output current stabilize,so as to achieve the purpose of high power factor and the intelligent control of output current.High power factor constant current source using LED energy-saving lamps for constant current and power factor test,the results show that the design scheme is correct and feasible,the circuit can effectively carry out the power factor correction,and reduce the influence of high pulse input voltage on the output voltage ripple,and the function of constant current output is realized,the performance index of the converter meets the design requirements.