A power-supply device and an electronic device including the relate to technology for a data storage device. The electronic device includes a power-supply device and a controller. The power-supply device generates a sudden power loss (SPL) detection signal in a sudden power off (SPO) state by detecting a level of an external power, generates a charging sense signal indicative of a charging capacity of an auxiliary power-supply circuit, divides the charging capacity into a plurality of charging levels, detects a level of the charging capacity, and generates a charging sense signal indicating a charging level of the auxiliary power-supply circuit in response to the detected charging level. The controller stores flushing information in at least one non-volatile memory device when the SPL detection signal is activated, and variably adjust an amount of storage in the non-volatile memory device in response to the charging sense signal.