A DC-DC converter includes an inductor, a switch module, and a pull-up circuit or a pull-down circuit. The inductor has a first node and a second node, and the second node is coupled to an output node of the DC-DC converter. The switch module is arranged for selectively connecting an input voltage or a ground voltage to the first node of the inductor according to a driving signal. The pull-up circuit is arranged for selectively providing a first current to the output node of the DC-DC converter. The pull-down circuit is arranged for selectively sinking a second current from the output node of the DC-DC converter. In addition, the first current or the second current is determined based on an inductor current flowing through the inductor.