Ibrahim Ab Abdelsalam
An improved single-phase ac-dc buck-boost converter operating in a discontinuous conduction mode
This paper presents two single-phase, single-stage, ac-dc buck-boost converter topologies (A and B), for low-voltage low-power applications. The proposed converters draw sinusoidal input currents from the ac grid at unity power factor, and generate stable step up/down dc output voltage from an ac voltage with fixed variable magnitude and frequency. Topology `A' connects its two dc inductors in series during the energising mode and in parallel during the discharging mode. Topology 'B' connects its two dc side inductors in parallel during charging and discharging modes. Parallel connection of the dc side inductors during the discharging mode reduces the discharging time and the duty cycle, thus allowing the duty cycle to be varied over a wider range than existing single-phase ac-dc buck-boost converters. The validity of the proposed converters is confirmed using PSCAD/EMTDC simulation and experimentation.