The principle of synchronous switching was introduced

and the key technologies of PMA based synchronous switching accurate zero-crossing detection of reference signal and reduction of switching time dispersion were analyzed. FIR filter was used to detect the zero-crossing of the reference signal. Simulation result shows high accuracy in detecting zero-crossing of disturbed signal with FIR filter. In actual sampling

the zero-crossing can be detected through linear interpolation. The analysis indicates that the switching time dispersion is affected by such factors as action time dispersion of actuator

control signal dispersion

and pre-breakdown. Adopting BP neural network and adaptive algorithm to compensate the actuating time in real-time environment （temperature and control voltage） can reduce the actuator’s dispersion; using highly accurate electronic elements will reduce the dispersion of control signal. The relation among the pre-breakdown voltage

the actuator’s dispersion

and the rate of decrease of dielectric strength（RDDS）is deduced to provide a theoretical basis for application of synchronous switching.