True bridgeless PFC - stages with advanced current measuring circuit

Compared with conventional CCM PFC converters, bridgeless PFC converters can achieve higher efficiency because of reduced conduction losses. However, since boost inductor lies in ac side, there are some difficulties in the control of such a circuit. Inductor current measuring and input voltage sensing are two main issues. Usually, current measuring techniques in bridgeless PFC are either very expensive or with losses or complicated. Besides this also the input voltage sensing is more complicated than in a conventional PFC converter. In this paper, a digital controlled bridgeless PFC converter is presented. A new cost-effective current measuring method is proposed, which is simple, lossless and realized only with a few components. Power losses and circuit complexity are reduced because of this. The new control scheme that does not require input voltage sensing is realized with an 8-bit microcontroller. As a result, the system has a simple structure and a good performance. The paper closes with experimental results, which show the performance of the new system.