Analysis Of Current Sensors' Electromagnetic Susceptibility And Improvement Method

Modern electronic industry of components is generally put forward the basic requirements of Electromagnetic compatibility,the requirements under the complex Electromagnetic environment can still work normally,which requires electronics Electromagnetic Susceptibility(EMS,Electromagnetic Susceptibility)should be as low as possible.As one of the important equipment in the electronic industry,the current sensor will produce a large zero output error when it is affected by the electromagnetic radiation in the surrounding environment,which will lead to exceeding the allowable error range and further affect the performance of the whole system.This paper is dedicated to the rapid and accurate analysis of the electromagnetic field on the current sensor,as well as the circuit susceptible to electromagnetic interference sensitive components,and the simulation and experimental testing of the sensitive circuit module in the electromagnetic interference under the working state,and finally put forward three kinds of improvement scheme to reduce the electromagnetic sensitivity.The work of this paper can be summarized as follows:1)Simulates the induced voltage generated by the electromagnetic field on the current sensor microstrip line.Three-dimensional model of current sensor is introduced by field analysis software,and the electrical parameters of the model agree with the real object.According to the electromagnetic compatibility standard field analysis software of radiation immunity,the corresponding parameters such as electromagnetic field intensity and incident direction are set,and passive resistance is used to replace active devices in the circuit,so that the numerical results are easy to converge and will not affect the numerical simulation results.By introducing the induced voltage of each circuit module into the circuit simulation,the working state of the circuit module under electromagnetic interference can be simulated.2)The influence of high frequency interference on op amplifier chip is analyzed by co-simulation of field and circuit.According to the previous joint analysis of field and circuit,it can be concluded that the operational amplifier is vulnerable to interference under electromagnetic radiation.The reason is that the operational amplifier is a small signal input,and the induced voltage generated by radiation on the microstrip line can easily affect the input signal of the operational amplifier.Although the op amp does not amplify high-frequency signals,the parasitic capacitance inside the op amp results in the asymmetric voltage at both ends of the MOS tube of the first difference circuit of the op amp.As a result,the dc offset voltage is output in the first difference circuit,which is amplified by the second and third circuits,resulting in a large output error.3)Simulation and experiment verify the effect of electromagnetic field on operational amplifier.The high frequency model of the first-stage differential circuit of the operational amplifier is established by the circuit software.The interference of the electromagnetic field is simulated by the voltage source,and the relationship between the dc offset and the frequency is simulated.The actual circuit of voltage follower is designed by operational amplifier,and the experiment verifies that when the rf signal is input,there is a dc offset at the output end,and the trend is consistent with the simulation results4)Research scheme to improve the anti-interference ability of current sensor.Metal full shielding is too dangerous to use because of high current monitoring.Therefore,the improvement of partial shielding,increasing parasitic capacitance,low-pass filtering and cross-coupling anti-interference ability are discussed respectively,and the feasibility of low-pass filtering scheme is verified by experiments.