An improved switch for power factor correction circuits includes a six-terminal switch which has a first inductor connecting to a selection line which has a first switch terminal and a second switch terminal, and a second inductor connecting to a conductive line. When the switch is at a first position, the selection line is connected to the first switch terminal, and the conductive line is closed to determine the first and second inductors in a parallel coupling condition and the power conversion circuit in a first duty condition. When the switch is at a second position, the selection line is connected to the second switch terminal and the conductive line is open to determine the first and second inductors in a serial coupling condition, and the power conversion circuit in a second duty condition.