An alternating current (AC) to direct current (DC) converter device includes an AC-to-DC converter circuit, a step-down DC converter circuit, a controller, a first standby power converter circuit and a second standby power converter circuit. The AC-to-DC converter circuit is adapted to receive and perform an AC-to-DC conversion on an AC power so as to output a DC bus voltage. The step-down DC converter performs a step-down conversion on the DC bus voltage so as to output a main power voltage. The first standby power converter circuit performs a step-down conversion on the main power voltage so as to output a first standby DC voltage. The second standby power converter circuit performs a step-down conversion on the DC bus voltage to output a second standby DC voltage.