EMI Principle and Suppression Method in Vehicle Ignition System

Vehicle ignition system is considered to be the main electromagnetic interference source. The electromagnetic interference (EMI) principle of ignition system was firstly analyzed, and harness trouble-shooting related to EMI was also tested. Results indicate that the spark discharge between spark plug electrodes is the main interference source in ignition system. Then, the conducted paths and the reason of radiated emission were detailedly discussed. Finally, a power supply wire EMI mixed filter was designed and implemented on the basis of analysis results. Experiment results indicate the filter can reduce the noise of power-wire in the broadband range. Meanwhile, the radiation emission level from power wire is also reduced observably.