Source of interference in the car

There is a variety of load on the automobile, both small impedance, big electric current load, small current, high voltage pulse device, also high-frequency oscillation signal source, which are not only the potential external interference sources, also for onboard electronic products. In addition, due to the high mobility, motor vehicles may also be at all can imagine from the low frequency of the complex to high-frequency electromagnetic fields, the resulting electromagnetic interference coupled automotive electronics will also affect the normal operation of electrical systems. Automotive Systems, the voltage can be divided into the following categories: normal voltage, abnormal steady-state voltage, radio interference voltage, transient over-voltage and electrostatic discharge.

The electromagnetic compatibility design of automotive electrical device

Automotive electrical EMC equipment environment should be coexistence, no-disturbance environment, which requires a good system with EMI and EMS characteristics. Causing electrical failure or functional degradation of the occurrence of electromagnetic interference must also have three elements: the source of interference and interference coupled pathway and sensitive equipment. Inhibit source of interference, blocking coupled sensitive equipment and to improve the anti-disturbance threshold is to solve the fundamental problem of electromagnetic compatibility measures.

1.Transmission and means of transmission of electromagnetic interference

EMI interference bound to exist in the energy transmission and dissemination channels. Interfere with the transmission there are two basic ways: conduction and radiation. Radiation coupled broken down into: the antenna of the antenna coupling, field on the line coupled to the line and line coupling. Against the spread of interference and coupling means, in electrical engineering practice in the car to be taken following the systematic approach to improve the EMC characteristics: filtering, shielding, ground strap connection and cabling.

2.Source of interference and sensitive device design of electromagnetic compatibility

In the scheduled functional circuits, electromagnetic compatibility test whether the indicators meet the requirements at this time if does not meet requirements, parameters can be modified to achieve through indicators, such as adjusting the number of controllers working frequency, round the whole pulse rate of increase or re - Choice of components, and so on. This was followed by a protective design, including filtering, shielding, ground strap connection overlap with the design, even temporal and spatial segregation and improvement measures such as avoiding frequencies. Finally, do adjust the layout of the design, including the overall layout of the test, the gap shield inspection of components and PCB layout inspection. Circuits and subsystems of the electromagnetic compatibility of the design include the following steps: select components, circuit choice, filtering technology applications, ground strap connection design, shielding design, layout and circuit layout planning system.