An integrated circuit controller for use in a light emitting diode (LED) driver includes a comparator, an input signal absence timer and a regulator circuit. The comparator receives a first voltage representative of an ac input signal and compares the first voltage with a reference voltage. The input signal absence timer determines whether the first voltage is less than the reference voltage for a threshold duration and in response thereto generates a detect signal indicating that a portion of an ac half cycle is absent from the ac input signal. The regulator circuit controls switching of a switch to regulate a transfer of energy from the ac input signal to an LED load. The regulator circuit is disabled from switching the switch in response to the detect signal indicating the absence of the portion of the ac half cycle from the ac input signal.