Dynamic Analysis of the Forward-Flyback Converter Considering the ESR of the Output Capacitor and Comparing it with the Flyback Converter

In this paper, the dynamic of a flyback converter is investigated by considering the effect of the output capacitor equivalent  series resistance (ESR) based on the calculation of the control input to output transfer function and based on the average value modeling method. The dynamic behavior of the non-minimum phase is an inherent behavior of the flyback converter, which by replacing it with the forward-flyback converter, for some values ​​of the parameters of the converter, it is possible to minimize the dynamic behavior. Calculating the transfer function of this converter is complicated due to the dependence of the state variables, so here a new method is used to calculate the transfer function by considering the effect of the series resistance of the output capacitor. The dynamic behavior of both flyback and forward-flyback converters have been compared by computer simulation results considering the effect of series resistance of the output capacitor. Also, a laboratory sample of both converters has been made and the results of laboratory measurements have shown the improvement of the dynamic response in the forward-flyback converter.