Practical Implementation and Verification of Simple-to-Implement Digital Current Observer for Half-Bridge Topologies

A novel and simple-to-implement digital current observer concept for PFC rectifiers based on half-bridge topologies is presented in this paper with the practical implementation and verification. The method makes use of only one current transformer and an auxiliary winding on the main inductor to estimate the whole inductor current. Moreover, compared to conventional shunt and dual current transformer (CT)-based solutions, the practical implementation of the proposed method results in less losses in the current measurement and in less influence on the switching characteristics of the power switches. The new method is verified with dedicated prototypes of a standard boost PFC rectifier and a bridgeless boost PFC variant, controlled by a low-cost digital signal processor (DSP).