The invention provides a tripper for circuit breakers. The tripper comprises an EMC circuit coupled with an external power grid, a rectifying circuit coupled with the EMC circuit, a signal sampling circuit and a power circuit coupled with the rectifying circuit, a microprocessor coupled with the signal sampling circuit and the power circuit, a protection circuit coupled with the signal sampling circuit and the microprocessor, and a trip driving circuit coupled with the protection circuit. The tripper is provided with the protection circuit for protecting the trip driving circuit, so that the accuracy and the safety of trip of circuit breakers are guaranteed.