An active diode that features improved control of transistor turn-off is provided. Such an active diode may include a comparator to compare voltages between opposite ends of a parasitic diode, and a gate driver to control a gate terminal of the transistor according to the comparison result of the comparator. Furthermore, the active diode may further include an off-timing controller to control the transistor to be turned off at a point in time when voltages of the opposite ends of the parasitic diode turn positive. Thus, the active diode may be turned off when required.