A flyback power converter includes a transformer having an auxiliary winding for generating an auxiliary voltage and providing a supply voltage on a supply node; a primary side controller circuit which is powered by the supply voltage from the supply node; and a high voltage (HV) start-up circuit. The HV start-up circuit is coupled to an high voltage signal through a HV input terminal and generates the supply voltage through a supply output terminal, wherein when the supply voltage does not exceed a start-up voltage threshold, a HV start-up switch conducts the HV input terminal and the supply output terminal to provide the supply voltage, and when the supply voltage exceeds a start-up voltage threshold, the HV start-up switch is OFF. The HV start-up circuit and the primary side controller circuit are packaged in two separate integrated circuit packages respectively.