A Single-Stage Power Converter for DC UPS Applications

A single-stage power converter for dc uninterruptible power supply (UPS) is proposed in this paper. Basically the proposed converter is an integration result of a power factor correction circuit with a dc-to-dc converter to achieve simple hardware circuit, high efficiency, and low cost for extra UPS function. Under normal operation, a two-switch CUK converter operates as an ac to dc converter with sinusoidal input current and unity power factor. Since both the input boost supply and the output supply can be controlled independently, a fast transient response can be maintained at both the input for active current wave shaping and at the output for good output regulation. When the ac source is outage, the proposed converter functions as a dc-to-dc buck converter, therefore the desired dc output voltage can be provided. Theoretical analysis and some experimental results are also detailed in this paper.