A power supply device and an operation method thereof are provided. The power supply device includes a charge pump circuit and a power supply circuit. The power supply circuit supplies a first power voltage to the charge pump circuit. The charge pump circuit converts the first power voltage into a second power voltage so as to supply the second power voltage to an application circuit. The power supply circuit detects the second power voltage or an output current output by the charge pump circuit to obtain a detection result. The power supply circuit dynamically adjusts the first power voltage based on the detection result.