A power apparatus includes a power circuit configured to receive an input voltage and generate an output voltage, a memory, and a processor coupled to the memory and the processor configured to calculate an integral value of an error between the output voltage and a target voltage of the power circuit, calculate a duty ratio based on the integral value, the power circuit being controlled according to the calculated duty ratio so that the output voltage becomes the target voltage, calculate a slope of the integral value with respect to an output current of the power circuit, and generate a first warning signal when the calculated slope exceeds a first warning threshold in a case where the calculated slope is different from an initial value.