Circuit and method for detecting breakage of neutral line and corresponding residual current circuit breaker

The invention provides a circuit for detecting breakage of a neutral line. The circuit comprises a direct-current power supply input end, a voltage detecting circuit and a control circuit, wherein the direct-current power supply input end is corresponding to phase line input, neutral line input and protected ground input respectively; the voltage detecting circuit is coupled to the input end, and used for detecting relative relation of first voltage of a first-direct power supply negative end corresponding to the neutral line input relative to reference voltage of a reference point, wherein the reference point is coupled to a second direct-current power supply negative end corresponding to the protected ground input; the voltage detecting circuit is designed, so that the relative relation of the first voltage and the reference voltage changes under the breakage condition of the neutral line; the control circuit is coupled to the voltage detecting circuit for driving a releasing unit to perform releasing operation so as to switch off the power supply connection of a power supply circuit when the relative relation of the first voltage and the reference voltage changes.