Multi-level configurations for three-phase AC-DC 48V power supply

International standards impose several constraints concerning the electric power quality and require that the harmonic content of the line current of grid connected equipment is below assigned limits. The most commonly used structure of a grid connected power supply consists of a diode bridge rectifier, a dc-dc converter used to shape the input current to sinusoidal form and a second dc-dc converter for output voltage regulation. In this paper the prototypal realization of a three-phase ac-dc 48V power electronic converter for telecom system supplying is described and experimental testing results are discussed. The carried out investigation is focused on the power supply second stage converter topologies; three-level configurations are considered in order to reduce voltage rating of power switches. As a result of the reduced voltage, low on-resistance MOSFETs can be used in the power stage, solution which allows to achieve improved efficiency as well increased switching frequency with respect to the IGBT based two-level topologies.