Research And Design Of Two-stage Low Cross Regulation Power Suppl

With the rapid development of power electronic technology,electronic equipment has higher requirements for the performance of two-stage multiplex output power supply.The front stage of a two-stage low cross-regulation rate power supply is usually a Boost PFC converter and the rear stage is a multiway output flyback converter.When the former Boost PFC converter works in DCM mode,the non-ideal characteristics of the components are easy to cause the input current distortion.The back-stage flyback converter realizes multiple output by adding transformer windings.Under this implementation mode,influenced by transformer leakage inductance,diode on-voltage drop and control mode,when the circuit load changes,there is a problem of cross-regulation rate for the output of the auxiliary circuit.In view of the above problems,this paper studies the two-stage low cross rate power supply.Firstly,the input current distortion suppression scheme of the front Boost PFC is studied.The equivalent circuit model of Boost PFC in the front DCM mode is constructed,and the main parasitic parameters affecting the circuit are determined.On this basis,the average inductance current model of single switch cycle is established to analyze the influence of parasitic parameters on input current.According to the influence factors of input current distortion,the suppression effect of CRM working mode on input current distortion was analyzed by changing the working mode of Boost PFC.The THD of the two working modes is compared,and the comparison results verify the feasibility of the CRM working mode to suppress the input current distortion.The simulation results show that the correlation analysis is correct.Then,the improvement scheme of the cross-regulation rate of the multiplex output flyback converter is studied.The circuit model of multioutput flyback converter is constructed and the influencing factors of cross-regulation rate are analyzed from multiple angles.Aiming at the causes of cross-regulation rate,the traditional improvement of cross-regulation rate is studied by optimizing transformer winding and adopting synchronous rectification technology.In view of the poor improvement effect of the cross-regulation rate of auxiliary paths in the traditional improvement scheme,a variable weighted feedback scheme was proposed,a power level model was established,and the output voltage was derived by DC.The cross-adjustment rate of auxiliary paths in the two schemes was compared,and the comparison results verified the effectiveness of the variable weighted feedback scheme.Under the PSIM simulation software,the causes of cross-regulation rate and the effectiveness of variable weighted feedback scheme to improve the cross-regulation rate of side roads were simulated,and the simulation results verified the correctness of the correlation analysis.Finally,according to the project design index,a 220 V AC input,24V/5A and 12V/2.5A DC output two-stage low cross-regulation rate power supply prototype is developed.The experimental results show that the PF and THD of the circuit are 0.951,10.57%,and the crossregulation rates of 24 V output and 12 V output are 7% and-11.67%,respectively.The experimental results verify the correctness of the theoretical analysis and the feasibility of the design scheme.The correlation analysis and conclusion have a certain reference value for the engineering application design of the two-stage low cross-regulation rate power supply.