A method and a circuit for detecting an electric arc in an electric circuit supplied with AC current during a supply period includes measuring at least one input signal (S) among a current (I) and an input voltage (U) of the electric circuit, supplying a warning signal (A1) to indicate that an electric arc occurs when the input signal (S) is constant over at least one portion of the supply period, digitally sampling the input signal (S) during the measurement thereof according to predetermined levels and, to identify that the input signal (S) is constant, determining the frequency at which each level is reached by the input signal (S) over a predetermined time window, comparing the frequency of each level with a predetermined warning threshold, and issuing the warning signal if the frequency of at least one of the levels is higher than the warning threshold.