A power system includes a control circuit, a power conversion circuit, a current detection circuit and a overheat detection circuit. The control circuit is for generating one or more pulse signal. The power conversion circuit is electrically coupled to the control circuit, for generating an output current according to the pulse signal. The current detection circuit is electrically coupled to the power conversion circuit, for generating a sensing current according to the output current. The overheat detection circuit is electrically coupled to the current detection circuit and the control circuit, for generating the correction current according to a temperature of the power conversion circuit. The control circuit adjusts a duty ratio of the pulse signal according to a correction sensing current to adjust the output current, and the correction sensing current is a sum of the value of the sensing current and the correction current.