Abstract: A switching power conversion circuit includes a pre-regulator circuit that is operated in buck, boost, or bypass mode and that includes a first switching circuit that receives an input DC voltage and outputs a first DC voltage; a resonant circuit including a second switching circuit that receives the first DC voltage and outputs an output DC voltage; a resonant control circuit that regulates the output DC voltage by transmitting a link min set control signal and a link max set control signal and by controlling a switching frequency of the second switching circuit; and a pre-regulator control circuit that receives the link min set control signal and the link max set control signal and that controls the first switching circuit based on the link min set control signal and the link max set control signal to regulate the first DC voltage.