The present invention is applicable to the technical field of charging electrical storage devices, and provides a charging circuit including an energy input, an input power detecting module, an electric energy storage, a boost module, a battery, a charging switch device, a PWM power isolating driver module, and a control module. In the present utility model, when detecting a decrease in the input power through the input power detecting module, the control module of the charging circuit will control the boost module to increase the electric energy stored in the electric energy storage, thus the charging voltage for the battery is increased and the charging efficiency of the charging circuit is improved.