The paper introduces a step-down converter that exhibits a static conversion ratio of cubic nature, providing an output voltage which is much closer to the input voltage, and at the same duty cycle, compared to a wide class of one-transistor buck-type topologies. Although the proposed topology contains many components, its control is still simple, as it employs only one transistor. A dc analysis is performed, the semiconductor stresses are derived in terms of input and output voltages and output power, revealing that the semiconductor voltage stresses remain acceptable and anyway lower than in other cubic buck topology. All detailed design equations are provided. The state-space approach is used to analyze the converter in the presence of conduction losses and a procedure for calculating the individual power dissipation is provided. The feasibility of the proposed cubic buck topology is first validated by computer simulation and finally confirmed by an experimental 12 V–10 W prototype.

This paper presents an in-depth analysis of a non-isolated buck–boost DC–DC converter which uses coupled inductors. The converter is designed to achieve a high static conversion ratio while using a moderate number of semiconductor devices. The proposed topology, originally introduced in a former paper of the authors, under ideal operating conditions, is now evaluated taking into account non-ideal components, modeling the conduction losses of the semiconductor devices and the equivalent series resistance of the output capacitor. In order to get a regulated output voltage, closed-loop behavior is also investigated. By using the state-space modeling approach, the calculation of the converter static conversion ratio and control-to-output transfer functions is performed. Because the topology is of fourth order, a procedure for controller design is provided. A type III error amplifier is chosen, and the pole-zero placement technique is used for its design, demonstrating that the classical control strategy still works even with this fourth-order converter. Thus, a good phase margin of 62.3 degrees is achieved. The theoretical results are validated both on open-loop and closed-loop operation, in the presence of conduction losses. Furthermore, a laboratory prototype is implemented, and it validates the theoretical and simulation results. The study demonstrates that the proposed coupled inductors buck–boost converter is a good choice for step-up applications that need a large difference between input and output voltages.