An example controller for use in a power supply includes a zero crossing detection (ZCD) circuit and a punctuated switching control circuit. The ZCD circuit is coupled to generate a ZCD signal in response to a zero-crossing of an ac input voltage of the power supply. The punctuated switching control circuit is coupled to the ZCD circuit to generate a switching signal to control a switch to regulate an output of the power supply. The punctuated switching control circuit generates the switching signal having an interval of switching and an interval of no switching in response to the ZCD signal, where the interval of switching has a beginning that is synchronized with the zero crossing of the ac input voltage and where the interval of no switching has a beginning that is synchronized with another zero crossing of the ac input voltage.