Patent ID: 8379420

Claim:
A controller for use in a power supply, the controller comprising: a zero crossing detection (ZCD) circuit coupled to generate a ZCD signal in response to a zero-crossing of an ac input voltage of the power supply; and a punctuated switching control circuit coupled to the ZCD circuit to generate a switching signal to control a switch to regulate an output of the power supply, wherein 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, wherein the interval of switching has a beginning that is synchronized with the zero crossing of the ac input voltage and wherein the interval of no switching has a beginning that is synchronized with another zero crossing of the ac input voltage, wherein the interval of switching reoccurs whenever an output voltage of the power supply drops below a threshold reference and wherein the punctuated switching control circuit delays the beginning of each interval of switching until a next zero crossing of the ac input voltage.