A high voltage power supply method and apparatus is disclosed. An apparatus according to aspects of the present invention includes a power supply circuit having a rectifier circuit coupled to input terminals of the power supply circuit that are to be coupled to receive an AC input voltage. A switchmode power converter circuit is coupled to the rectifier circuit to receive a rectified input voltage to generate a regulated output voltage in response to the rectified input voltage. A switch is coupled between the rectifier circuit and the switchmode power converter circuit. A sense circuit is coupled to detect the AC input voltage. The switch is coupled to be switched in response to the sense circuit. The switch is coupled to be switched off when an absolute value of the AC input voltage exceeds a first threshold value. The switch is coupled to be switched on when the absolute value of the AC input voltage is below a second threshold value.