Patent ID: 8531133

Claim:
A controller for a switched mode power supply, the controller comprising: a comparator having an output, a first input coupled to receive a current sense signal representative of a current through a switch of the power supply, and a second input coupled to receive a reference signal representative of a zero-crossing current threshold; a drive logic coupled to generate a drive logic output signal in response to the current sense signal and in response to a feedback signal representative of an output of the power supply, wherein the drive logic output signal is representative of an on-time of the switch to regulate the output of the power supply; and an on-time extension block coupled to control the switch in response to the output of the comparator and in response to the drive logic output signal, wherein the on-time extension block increases the on-time of the switch until the output of the comparator indicates that the current sense signal reaches the zero-crossing current threshold or until the on-time of the switch reaches a zero-crossing time threshold.