A high voltage power supply method and apparatus is disclosed. An apparatus according to aspects of the present invention includes a power supply circuit (200) having a rectifier circuit (203) coupled to input terminals (201, 202) of the power supply circuit (200) that are to be coupled to receive an AC input voltage. A switchmode power converter circuit (204) is coupled to the rectifier circuit (203) to receive a rectified input voltage to generate a regulated output voltage in response to the rectified input voltage. A switch (207) is coupled between the rectifier circuit (203) and the switchmode power converter circuit (204). A sense circuit (208) is coupled to detect the AC input voltage. The switch (207) is coupled to be switched in response to the sense circuit (208). The switch (207) is coupled to be switched off when an absolute value of the AC input voltage exceeds a first threshold value. The switch(207) is coupled to be switched on when the absolute value of the AC input voltage is below a second threshold value.