An illustrative example embodiment of a method is for controlling a switch. The switch is used to charge a capacitor that provides an output voltage. The switch has an inductor on an input side between a power source and the switch. The method includes: initiating a switching cycle including turning on the switch, sensing a voltage representing current through the inductor, using a reference voltage as a basis for turning off the switch during the switching cycle when the sensed voltage exceeds the reference voltage, and setting an initial value of the reference voltage at a beginning of the switching cycle based on at least one feature of an activation of the switch during at least one previous switching cycle.