An integrated circuit including a power supply including an AC input, an AC to DC rectifier, a DC output of the rectifier, a switch for shunting the AC input, and a controller including a first connection to the DC output, a second connection to the AC input, wherein the controller is configured to monitor the DC output, determine if the DC output is within a first threshold of a desired output, monitor instantaneous AC voltage across the AC input, determine if an absolute difference of the AC input from zero voltage is less than a second threshold, and if the DC output is within the first threshold and the absolute difference of the instantaneous AC input from zero voltage is less than the second threshold, then provide a command to the switch to shunt the AC input. Related apparatus and methods are also described.