A smart primary side current sensing strategy for single stage isolated PFC controller

A novel primary side current sensing strategy is presented in this paper, which is especially suitable for the primary side controlled high power factor single-stage flyback LED controller. In order to avoid the constant-current regulation accuracy error caused by electromagnetic interference (EMI) issue, the proposed current sensing technique utilizes the switched-capacitor interleaved sample and hold circuit to obtain the middle point of the primary side current sensing period. The single-stage LED driver utilizing the proposed current sensing scheme has been implemented in CZ6H 0.35 um standard CMOS process, simulation results show that load regulation and line regulation accuracy can be improved greatly.