Automobile Ignition Noise Suppression Based on Coupling Theory 2007-24-0102

The use of high performance devices and systems in automotive environment has been increasing day by day. EMI/EMC requirements of those devices made the man-made automotive ignition noise become a very significant issue for car designers. In this paper, ignition noise which is made by the operational mutual relationship of coils inside the ignition coil and the disturbances of ignition current will be analyzed and suppressed focusing on the implementations of automotive ignition system in commercial cars. In this, we analyzed the Electronic Ignition (EI) system's structure and its operational procedures to figure out the relationship between system design and noise performance. As a result, system noise will be measured and analyzed from the perspective of coupling noise characteristics. Base on this analysis, feasible solutions for noise suppression such as: changing coil's structure to minimize the voltage ripple in the power line; change the current path's layout to reduce the coupling area; shielding to isolate the noise source from other noise sensitive signal lines, have been proposed, analyzed, and experimented. The experimental results under proposed settings show a 60% reduction of voltage ripple in the power line; 50% reduction of peak to peak ignition coupling noise voltage in the signal lines and a −30dB maximum attenuation at 22MHz in the frequency domain of the power line. In addition, some related issues such as proposing a new high performance design with integrated igniter inside the coil as well as the rules of thumb for system's wiring will be covered in this paper.