Circuits and methods to detect a threshold for entering and leaving a discontinuous current mode of a buck converter have been disclosed. A buck converter is switched to continuous mode if the filtered battery current has reached a defined threshold current Ithccm. In order to expedite the transition from DCM mode to CCM mode the time delay between two or more pulses of a current through an inductor is monitored and the buck converter is switched to CCM mode if this time delay is smaller than a defined threshold.