Integrated on-time extension for non-dissipative bleeding in a power supply

摘要

An example controller for a switched mode power supply includes a zero crossing detector, drive logic, and a logic gate. The zero-crossing detector generates a zero-crossing signal indicating a zero-crossing condition in the power supply. The drive logic generates a drive logic output signal in response to the zero-crossing signal and in response to a feedback signal, where the drive logic output signal is representative of an on-time of a switch to regulate an output of the power supply. The logic gate is coupled to receive a first signal representative of a current through the switch and a second signal representative of a zero-crossing time threshold. The logic gate is further coupled to extend the on-time of the switch until current through the switch reaches a zero-crossing current threshold or until the on-time of the switch reaches the zero-crossing time threshold.