Discontinuous inductor current in the optimum topology switching converter

Abstract

It is demonstrated, first, how the complex modular converter structures (such as cascade of the boost and buck converters) can be easily modelled in the discontinuous current mode by use of the state-space averaging method and equivalent circuit approach and by taking advantage of the known properties and circuit models of the individual converter modules (boost and buck converters). Then, the recently introduced new optimum topology switching dc-to-dc converter is analyzed in the discontinuous inductor current mode. Unlike other converters with two inductors (such as cascaded boost-buck), the new converter has a unique feature that both inductor currents become discontinuous at the same instant, and remain so with the same second (decay) interval. Moreover, for the first time, the discontinuity of the inductor current takes place at a nonzero inductor current level, with dc current, passing through both inductors in the remaining third part of the switching period. It is shown how this peculiar behaviour can be successfully modelled and a simple analytic criterion for determination of the boundary between the continuous and discontinuous inductor current mode is obtained.