A controller for a synchronous switching regulator is arranged to control a switch with a control signal, and to control a synchronous switch with a synchronous switch control signal. The controller disables the synchronous switch control signal at power-up so that the regulator operates with asynchronous rectification. Also, the controller is arranged to detect whether the regulator is in discontinuous or continuous conduction mode by determining whether a switch node voltage at the switch node a switch node stays negative. The regulator keeps operating with asynchronous rectification until the switch node voltage stays negative for the entire off period of the switch, which indicates the regulator is operating in continuous conduction mode. At this point, the controller enables assertion of the synchronous switch control signal, so that the regulator operates with synchronous rectification. The controller is arranged to enable the output voltage to rise monotonically when driving a prebiased load.