A Soft-switching Single-stage Zeta-/SEPIC-based Inverter/Rectifier

In this paper, two soft-switching single-stage converters are proposed: A Zeta-based inverter and a SEPIC-based rectifier. These two converters are capable of both stepping up and stepping down the voltage in a wide range. Moreover, these converters use a very small film capacitor at the link, instead of electrolytic capacitors that are used in most of the conventional two-stage inverters and rectifiers. Electrolytic capacitors have a shorter lifetime compared to other components of a power electronic converter and their elimination significantly improves the reliability of a converter. This feature is feasible due to having an ac link voltage instead of a dc link. All the semiconductor switches in the proposed converters benefit from zero-current-switching with the help of a very small inductor placed in series with the link capacitor with no auxiliary/additional active switch/diode. Due to the small size of the link capacitor, which is the main energy transferring component of the converters, the dynamic response of both converters is very fast, making these converters suitable for very fast response (VFR) applications. Furthermore, a high-frequency transformer can be employed at the link in case galvanic isolation is needed, thanks to the high-frequency ac voltage of the link. In this paper the principles of the operation of these converters are explained, and their performance is evaluated through simulation and experiments.