A power converter controller asserts a leading edge signal when a leading edge of a voltage signal is detected. The voltage sense signal is representative of an input voltage of the power converter. A trailing edge signal is asserted when a trailing edge of the voltage signal is detected. A first state of a threshold signal is generated when the voltage sense signal is at or above an upper threshold and generating a second state of the threshold signal when the voltage sense signal is at or below a lower threshold. A conduction signal is updated in response to the leading edge signal, the trailing edge signal, and the threshold signal. The conduction signal is for controlling a switch coupled to regulate an output of the power converter.