In this paper a simple passive nonlinear delay locked protection circuit is proposed.It posseses all the functions of counter delay locked protection circuit which consists of complex digital logical circuit.Besides
in some cases it’s better than the latter such as in circumstance using rc-lowpass circuit to replace the integrate-dump circuit.The performance of passive nonlinear delay locked protection circuit is analyzed. The mean and variance of locked hold time are given under the conditions of both ideal integration and rc-lowpass circuit correlation processing.