A General Method for Deciding the Input Filter Capacitance of Flyback Switching AC-DC Converter with Peak Current-Controlled Mode

This paper presents a general method for deciding the input filter capacitance of flyback switching ac- dc converters with peak current-controlled mode. Firstly, a simulation model for flyback ac-dc converter is obtained by adding the rectifier and filter circuit to a flyback dc-dc converter model developed by the authors. The simulation results show that the processes of capacitor charging and discharging are independent, their boundary is near the maximal value of input voltage, and the part of flyback dc- dc converter can be seen as an approximately constant power load. Secondly, an analytic model for deciding the input power of flyback dc-dc converter with rated load and different input dc voltages is presented. Furthermore, the effect caused by the parasitical parameters in the electronic parts is studied, and the corresponding analytical method for deciding the input filter capacitance is given. The effect on the capacitance caused by the control delay is analyzed qualitatively.