A power detection circuit includes an input end for receiving an AC input signal, a rectifier for converting the AC input signal into a rectified signal, an output end for outputting the rectified signal, at least two voltage clamp circuits, each for providing an electrical path between the output end and a reference voltage end when the rectified signal is greater than a threshold voltage of the voltage clamp circuit. A threshold voltage of at least one of the voltage clamp circuit is different from a threshold voltage of another clamp circuit.
