A digital flash charger controller includes a transformer, a power supply element, and an application-specific integrated circuit (ASIC). A secondary side of the transformer is electrically connected to an energy storage device, and the power supply element is used to supply an electric power to a primary side of the transformer. The ASIC outputs a pulse-width-modulation (PWM) signal to control whether the electric power is input to the primary side, and the ASIC converts a sensing signal generated at the secondary side of the transformer to a digital signal, and tracks a sensing negative edge of the sensing signal according to the digital signal to adjust a cutoff time of the PWM signal, such that the next pulse positive edge approaches the corresponding sensing negative edge.