Modeling of linear-assisted DC-DC converters

This paper shows the modeling of a linear-assisted or hybrid (linear & switching) DC-DC converters. In this kind of converters, an auxiliary linear regulator is used, which objective is to cancel the ripple at the output voltage and provide fast responses for load variations. On the other hand, a switching converter, connected in parallel with the linear regulator, allows to supply almost the whole output current demanded by the load. The objective of this topology is to take advantage of the suitable regulation characteristics that series linear voltage regulators have, but almost achieving the high efficiency that switching DC-DC converters provide. Linear-assisted DC-DC converters are feedback systems with potential instability. Therefore, their modeling is mandatory in order to obtain design guidelines and assure stability of the implemented power supply system.