A boost converter for converting between an input voltage and an output voltage is disclosed. The boost converter includes an inductor connected to the input voltage a switching arrangement for controlling the switching of the inductor current to an output load at the output voltage and a controller for controlling the switching arrangement to provide duty cycle control. The duty cycle control switching takes place when the inductor current reaches a peak current level which varies over time with a peak current level function. The peak current level function includes the combination of a target peak value derived from a target average inductor current and a slope compensation function which periodically varies with a period corresponding to the converter switching period.