Exploiting Saturable Inductors in SEPIC Regulators

This paper discusses the use of saturable power inductors in Separated Inductor Single-Ended Primary Inductor Converter (SI-SEPIC) regulators. To ensure control stability, the input and output inductors in a SI-SEPIC regulator must be selected with an inductance ratio fitting suitable constraints, which may lead in turn to large output inductance in applications with step-up voltage conversion ratio. The method and the results presented in this paper show that using saturable ferrite inductors allows to reduce the size of these components, while providing larger inductance in low-load operation, thus helping in discontinuous conduction mode prevention and overall efficiency increase. The results are validated by means of simulation tests performed on a 9V/1.5A SI-SEPIC regulator.