There are many ways of interference suppression measures, the common ones are shielding, filtering, grounding, and damping.
In the selection of electromagnetic interference suppression measures, first consider the interference source, and adopt different suppression methods according to the characteristics of different interference sources. Such as the interference of the ignition system, the interference of the power supply system, the interference caused by the inductive load or the switching load, etc. Secondly, consider the propagation path of interference, which is very important to take effective suppression measures. The way of interference can be: through the cable of the power supply system, through the antenna or various wires, through the coupling, and directly radiating electromagnetic waves through the space. In addition, interference suppression should consider the suppression cost. The general processing method is to limit the interference noise generated by the interference source to the specified reasonable range, and the interfered party should have a certain ability to resist interference, so as to achieve a state of mutual coexistence and mutual non-influence. Unrestricted increase in interference suppression will increase the suppression cost exponentially, which is not desirable in practical applications.
There are many ways to suppress the interference of automotive electronic and electrical components. Test products can be used for simulation testing: transient pulse interference simulator, automotive power supply voltage change simulator, automotive load dump simulator, automotive immunity test software and other products. Generally, several grade limits are stipulated, and a reasonable grade limit should be selected for different components according to their characteristics and usage methods to reduce the cost of suppression.
For the interference from the power supply system in the car, a simple and effective method is to use the battery as a very low impedance, large-capacity transient voltage suppressor to absorb the interference energy generated by various transient voltages. The best way is to ensure that the battery cables are well connected. If the negative pole is grounded, the grounding resistance should be ensured to be the smallest. It is necessary to ensure that the line impedance reaches the minimum value, or even zero.
For the interference caused by the coupling between cables, a cost-saving method is to fully consider the reasonable and effective layout of the cables when wiring in the car. The best way is to separate the ECU control line or signal line from the power line to reduce the interference caused by coupling. In addition, the use of shielded cables is also a good way to prevent external electromagnetic interference from invading the control lines and signal lines. For the interference caused by inductive load, the suppression method can use a capacitor of appropriate value in parallel to eliminate the reverse overvoltage.
