Abstract: A breaker connected between a power source end of an electric device and a power source comprises a power retriever for setting a first reference voltage; the first reference voltage being corresponding to a limiting value; a comparator for comparing a first reference voltage and a second reference voltage value; the second reference voltage value being corresponding to a power used in the electric device; a timer; when the second reference voltage value being smaller than the first reference voltage; the timer determining whether a counting time period is over a breaking time; and a switch; if the time period is over the breaking time, the switch will turn off a connection between a power source end of the electric device and the power source.