Small signal models of a zero-voltage-switched SEPIC dual converter with a coupled inductor

Several small signal models are developed for the coupled-inductor zero-voltage-switched SEPIC dual power converter via the extended circuit averaging method and compared to the measured response. Although the ideal model shows only a two-pole response because of the coupled inductor action, the final model must include the parasitic resistances and the leakage inductances of the coupled inductor to match the actual measured four-pole power converter response. The parasitic resistances are found to affect the location of the transfer function zeros. The turns ratio and the leakage inductances of the coupled inductor, which determine the large signal zero current ripple condition, are found to influence the transfer function response. Therefore, the DC and AC design of the power converter are forced to be interdependent because of the coupled inductor operation