| With the rapid development of electric vehicles at home and abroad,the electronic systems of electric vehicles are complicated and highly integrated,involving high-voltage and low-voltage electrical conversion,making the electromagnetic environment increasingly harsh.The wiring harness is used as a connection link to closely connect the various electronic control systems and on-board electronic equipment in the vehicle.While providing a channel for signal exchange and energy transmission,it also provides a carrier for electromagnetic interference.It is an interference source device and a sensitive device.An important transmission channel of electromagnetic interference.The electromagnetic interference signal generated during the working process of the equipment can directly enter the sensitive equipment through the complete circuit connection of the cable,such as resistive coupling.Or enter the control line and signal line through capacitive coupling and inductive coupling between cables,which will affect sensitive equipment.In addition,the electromagnetic radiation generated by the vehicle wiring harness can also affect sensitive equipment through radiation interference in space by means of field line coupling.With the increase of the operating frequency of electrical and electronic equipment,and the high d V/dt,di/dt voltage and current change rate,new engineering application environmental changes have exacerbated the deterioration of the electromagnetic environment of electric vehicles.Therefore,the analysis of reflection,crosstalk and electromagnetic radiation caused by signal transmission lines in the transmission process has important engineering value.In this paper,the electromagnetic interference research of automobile wiring harness is mainly divided into three aspects: transmission line reflection mechanism analysis,automobile wiring harness crosstalk modeling and electromagnetic radiation simulation.The details are as follows:For the first,for the signal reflection problem caused by the mismatch of the characteristic impedance of the cable connection port and the discontinuity of the transmission impedance,the connector circuit model and the physical model of the via are established.Since the size of the transmission line of the circuit cannot be much smaller than the wavelength,and even the size can be compared with the wavelength,the reflection problems such as ringing and delay on the transmission line at this time occupy an important position in the influence factors of automobile electromagnetic interference and cannot be ignored.Therefore,it focuses on the analysis of the reflection mechanism of the signal transmission line,and considers the discontinuous impedance of the transmission line connection device(ie connector)and the transmission line itself,such as via holes,transmission path changes,and different connection structure methods,etc.,which cause signal reflection.Second,based on transmission line theory,an equivalent circuit model of crosstalk between cables is established,and the main influencing factors of crosstalk coupling are discussed.Based on the experimental method,the characteristic impedance of the cable is fitted by the circuit element capacitance and inductance,and the crosstalk equivalent circuit model between the transmission lines is obtained,which avoids the complicated and tedious derivation and solution process of the multi-conductor transmission line equation,reduces the workload,and simplifies the application constraints.The working frequency,cable length,cable spacing,termination impedance and other related factors are discussed and analyzed.For the third,based on the S-parameter characterization of cable characteristics,the mechanism and suppression methods of radiated electromagnetic interference are analyzed.Based on the Buck circuit,this article first analyzes the main path and mechanism of electromagnetic radiation interference.Then,for the electromagnetic radiation caused by the common-mode loop,simulation analysis and verification of the effectiveness of the three methods of controlling the loop area and using the ground plane to introduce low ground impedance and the ground trace loop surrounding the signal are effective in suppressing radiation. |
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