A power converter is preferably mounted in a vehicle. The converter has a power converting unit including an electrical switching element electrically switched on and off selectively in response to a duty ratio of PWM (pulse-width modulation) signal given to the switching element. The converter further has a controller including a drive unit that generates the PWM signal, in addition to a controlling unit and a limiting unit. The controlling unit controls the duty ratio of the PWM signal such that a voltage inputted to the power converter is converted to a voltage to be outputted depending on the duty ratio. The limiting unit limits at least one of a time change amount of the duty ratio of the PWM signal and a maximum duty ratio of the PWM signal.