The Design And Application Research Of Surge Suppression Circuit For The CAN Interface

As an international standard of fieldbus, CAN bus is widely used in the automobile industry, the railway industry and the industrial control industry such as these very important national economy areas, and people’s production and life are closely related. In order to avoid the equipment and systems with CAN bus technology having direct damage and indirect cumulative damage by surge invasion, resulting in the loss of people’s lives and property, it is necessary to study surge suppression technology used in the CAN interface, make conclusions and apply to the field.In this paper, it is studied that surge suppression circuit is used in the CAN interface as a practical application project. I use the electromagnetic compatible subject analysis and problem solving ideas, analyze from the three elements of EMC disturbance source, coupling path, sensitive equipment, through data checking, standards studying, theoretical analysis, circuit simulation, circuit design and actual test, finish the task of exploring the project step by step. It has mainly completed the following work:In the part of learning the background knowledge, it firstly analyzes the surge of main disturbance sources, and summarizes the surge waveform characteristics from the time domain and frequency domain. It secondly surveys and analyzes surge suppression device such as GDT, MOV, TVS, TSS commonly used in the actual project, summarizes their properties and advantage and disadvantage, makes the conclusion that GDT and MOV suitable for using in the first level protection circuit, and TVS suitable for using in the second protection circuit with accurate protection. It thirdly analyzes the working mode and the electrical performance requirement of CAN interfaces with two different speeds for providing the basis of simulation and design of the surge suppression circuit.In the part of circuit simulation, it simulates the protection effect of ideal TVS suffering surge and the influence of the TVS protection effect by the elements of non-ideal characteristics such as junction capacitance, lead resistance, lead inductance through the Multisim software.In the part of circuit design and test, according to the conclusion of background knowledge and the simulation result, it firstly designs several kinds of surge suppression circuit, and has the actual test to the design circuits based on the national standard GB/T17626.5"electromagnetic compatibility testing and measurement techniques (impact) surge immunity test". It secondly analyzes and compares the different test result, and focuses on the research of the effect of the inductance and resistance between the first level and the second level in surge suppression circuit and the effect of the series inductance to the transmission of different speed signal. It finally respectively designs the proper surge suppression circuit for the high and low speed CAN interface, and describes the details of how to select the parameters of the components.