Research On High Frequency Voltage Sensing Method Of SiC MOSFET Based On Electric Field Coupling Principle

In recent years,silicon carbide(SiC)MOSFET has entered the rapid development stage of industrialization and is gradually applied in the fields of new energy vehicles,5G communication,high-speed rail transit and so on.With the continuous development of SiC MOSFET,the research on its switching characteristics has attracted the attention of scholars at home and abroad.As an important parameter for analyzing switching characteristics,the accurate measurement of switching voltage is the premise of device characteristic analysis,loss calculation and junction temperature extraction.It is also the key to device operation state evaluation,life prediction and the establishment of reliability big data model.It can be seen that the research of high-performance voltage sensor is very important.With the improvement of the performance of SiC MOSFET in switching speed,withstand voltage and power density,the problem of difficult switching voltage measurement is becoming more and more prominent,which puts forward new requirements for the bandwidth,invasiveness,online measurement ability and cost of voltage sensor.Therefore,the research on how to accurately and efficiently obtain the switching voltage information of SiC MOSFET has certain practical significance and academic value.In this paper,a non-contact voltage sensor using the principle of electric field coupling to measure the switching voltage is proposed,which avoids the direct contact with the original circuit and solves the invasive and safety problems of the contact sensor to a great extent.Firstly,the switching characteristics and test methods of SiC MOSFET and the problems existing in the test process of voltage sensor are analyzed in detail.Secondly,the principle of non-contact electric field coupling method to measure the switching voltage of SiC MOSFET is introduced,and the voltage of the induced signal of the sensor is reconstructed by using the hybrid integrator composed of active integrating circuit and selfintegrating circuit,so as to realize the measurement of high-voltage and high-frequency signal.The bandwidth range of the sensor is 5Hz ～ 260 MHz,the measuring range is-1000V～ + 1000 V,and the input capacitance is about 0.73 pf.The sensor is made of PCB and measured by patch method,which greatly reduces the cost of the sensor.It has small volume and simple structure,and can be used for system integration,which is conducive to the realization of on-line condition monitoring of devices.In order to realize the integrated on-line measurement of switching voltage,the electric field coupled voltage sensor integrated in SiC MOSFET power circuit is studied in this paper.Firstly,the layout type of power circuit and the influence of different layout on the switching voltage measurement results are introduced,and the interference to the switching voltage measurement in power circuit is analyzed.Secondly,based on the optimal layout and using Q3 D and Maxwell simulation analysis to minimize the surrounding interference,the optimal integration position is selected to realize the integration of sensors.Finally,the performance of the patch and integrated electric field coupling voltage sensors is verified by experiments,and the measurement results are compared with Tek TPP0850 to verify the accuracy of the non-contact electric field coupling voltage sensor.