Techniques to obtain single-stage power supplies with power factor correction (PFC)

In order to comply with the standards, the input current of the switch mode power supplies (SMPS) must be almost sinusoidal, i.e. the SMPS must achieve power factor correction. This requirement is normally reached with the use of an additional input converter, typically a boost, resulting in a two-stage SMPS with the inherent drawbacks: high cost and the necessity of high efficiency in each stageto obtain a reasonable global efficiency. This article introduces two simple techniques together with the control strategies that can be used to obtain single-stage SMPS, that allow the control of the output voltage and the sinusoidal input current wave shaping, without any additional stage. Another objective of this article is to investigate and to evaluate the performance of each topology that emerged from the chosen technique. Considering high-power applications, experimental results of two single-stage full-bridge topologies are also presented, in order to verify the concepts introduced in the article.