In an embodiment, method of controlling an illumination device by an output signal of a DC-DC converter is disclosed. The output signal is controlled by a PWM signal. The method includes receiving a feedback signal corresponding to variation in the output signal with respect to a pre-determined output signal, and determining a target duty cycle of the PWM signal based on the feedback signal. The PWM signal of the target duty cycle is capable of enabling the DC-DC converter to generate the pre-determined output signal. The method includes providing the PWM signal of an effective duty cycle equal to the target duty cycle over N switching pulses of the PWM signal to the DC-DC converter. The method provides the PWM signal by providing M switching pulses of a first PWM signal of a first duty cycle, and N−M switching pulses of a second PWM signal of a second duty cycle.