Patent ID: 7872461

Claim:
A reverse current stopping circuit for stopping a reverse current of an inductor in a synchronous rectification type DC-DC converter, comprising: a switching device; a synchronous rectification device connected to the switching device and the inductor; a comparator for detecting the reverse current of an inductor current from a drain-source voltage of the synchronous rectification device, said synchronous rectification device being configured to be turned off as soon as the reverse current of the inductor current is detected by the comparator; a reverse current detector circuit for detecting a switching terminal voltage of the switching device immediately after the synchronous rectification device is turned off, thereby determining a value of the inductor current when the synchronous rectification device is turned off so as to decide whether the inductor current is flowing in a reverse direction from the inductor toward the synchronous rectification device or in a forward direction from the inductor to an output terminal; and a memory unit for receiving a predetermined output signal output from the reverse current detector circuit in accordance with a decision made by the reverse current detector circuit, and outputting a control signal for controlling an offset voltage in accordance with the predetermined output signal to the comparator, wherein the offset voltage of the comparator is changed in accordance with the control signal so as to adjust a value of the inductor current to zero when the synchronous rectification device is turned off.