A control device includes a first switch, a second switch, a switching circuit, a first circuit and a second circuit. The control device is selectively switched to a first mode or a second mode corresponding to an operating current and an operating state of a predetermined circuit. During the first mode, an output signal of the first circuit is transmitted to a control end of the first switch through the switching circuit, and the first circuit and the first switch form a low drop-out regulator. During the second mode, a plurality of driving signals of the second circuit are transmitted to the control end of the first switch and a control end of the second switch through the switching circuit, and the first switch, the second switch and an impedance circuit form a switching voltage converter.