Apparatus and methods are provided for starting up an isolated power converter. In an example, an integrated circuit for controlling an isolated power converter can include a control circuit configured to control a duty cycle of a primary switch according to an startup schedule during an initial interval of a start-up period of the isolated power supply, and to switch to a closed-loop control mode of the primary switch during a second interval of the start-up period after a voltage level of the DC output power signal is above a start-up threshold.