A method of detecting zero crossings in an AC input voltage at an input of a power converter includes measuring, at a first time, a first voltage. If the first voltage is positive: determining that the first time corresponds to a positive half-cycle of the AC input voltage. If the first voltage is equal to zero: a) determining that the first time corresponds to a negative half-cycle of the AC input voltage; b) turning on a high-side switch of the power converter for a first time period; and c) measuring, during the first time period, a second voltage. If the second voltage is less than a first threshold, turning off the high-side switch and repeating b) and c) after a time delay. If the second voltage is less than a second threshold, maintaining the high-side switch in an ON state for a second time period.