A comparison of single-phase transformer-less PWM frequency changers with unity input power factor

Several single-phase frequency changer topologies are presented. Six of these are synthesized by cascading one of three unity input power factor rectifier stages (buck, boost, and flyback derived) with either a full or half-bridge inverter output stage. Also presented, is a novel and quite different topology, which is referred to as the symmetrical boost half-bridge frequency changer. It is shown that the symmetrical boost converter has the lowest switch and reactive component counts. Unlike the other converters presented in this paper, the symmetrical boost converter preserves the mains neutral connection from input to output without the use of a transformer