In this paper an attempt has been made to analysis the operation of an ac/dc converter with quasi-active power factor correction. This investigation has been made in two steps. In the first step, an analytical investigation is made considering some logical assumptions. In the second step, one of the assumptions has been neglected for a more precise analysis and the principal operation of the circuit has been investigated analytically again. To confirm the accuracy of the theoretical analysis results, the circuit operation has been analyzed numerically and simulated. The obtained results admit the previous assessments.