An overvoltage protection circuit includes an output transistor connected between a first power supply and an output terminal, a load connected to the output terminal, a dynamic clamping circuit for controlling a voltage difference between the first power supply and the output terminal, and a clamp selection switch electrically connected between the dynamic clamping circuit and the output terminal, and a conductive condition of the clamp selection switch is determined according to a comparison between a reference voltage and a voltage of the output terminal.