Research On Parallel Current Sharing Technology Of Passive Silicon Carbide MOSFETs

With the development of material technology,silicon carbide materials came into being.The excellent performance of silicon carbide semiconductor devices determines that they are suitable for high-frequency,high-efficiency and high-temperature environments,and have been widely used.After years of development,SiC devices have made great progress both in terms of device structure and process optimization.At present,due to the limited single cell capacity of existing power devices,it is necessary to connect the device cells in parallel in medium and high power applications.Due to the inconsistency of the threshold voltage and drive delay of the parallel devices,the switching process of the parallel devices cannot be completely Synchronously,SiC devices have faster switching speeds,and very short deviations in turn-on and turn-off time will cause great differences in current distribution.Therefore,it is very important to study the parallel current sharing of SiC devices.In this paper,several factors that lead to uneven parallel flow of power devices are discussed at first,and the influence process of each factor on the degree of uneven parallel flow is discussed,and other influences of uneven parallel flow on power devices are analyzed in the form of mathematical formula.Subsequently,a new passive current sharing circuit for paralleling wide bandgap device SiC MOSFETs was proposed.The new current sharing circuit uses a differential mode current transformer as the core and cooperates with the core demagnetization circuit to form a complete passive current sharing circuit.This paper analyzes the current sharing principle of the current sharing circuit,and the formula deduces the calculation method of each key device parameter in the new current sharing circuit.Through the calculation method,the device parameters that meet the experimental conditions are calculated,the calculated device parameters are brought into the simulation model built in the simulation software,and the effectiveness of the new current-sharing circuit and the correctness of the theoretical derivation are verified in the simulation software.In the simulation software,a comparative simulation is performed to compare the circuit efficiency of the synchronous buck with the addition of the current sharing circuit and without the current sharing circuit.At the end of this paper,a prototype of current sharing circuit based on synchronous BUCK circuit topology is designed,and the experimental parameters are calculated using the theoretical derivation results in the article to verify.The experimental results show that the new type of current sharing circuit designed in this paper can better achieve the parallel device current sharing,while verifying the effect of the newly added current sharing circuit on the efficiency of the original circuit.The new current sharing circuit with a simple structure adapts to various forms of parallel structure with comparatively higher stability,which provides a practical scientific basis for the parallel application of power devices.