SiC MOSFET并联动态电流不均衡的无源补偿策略

Passive Compensation Strategy of Imbalanced Dynamic Current in Paralleled SiC MOSFETs

SiC MOSFET分立器件的并联结构已在中大功率应用中广泛使用,为了充分利用并联的优势,需解决并联动态电流不均衡问题。在SiC MOSFET特性参数中,阈值电压是影响并联动态均流特性最主要的参数。通过建立SiC MOSFET双管并联的电路模型,探究了并联动态电流不均衡的补偿策略,推导了阈值电压对SiC MOSFET开关管动态均流程度影响的公式。建立了含寄生电感的双管并联电路模型,提出了两种双管并联动态电流不均衡的无源补偿策略,即基于共源极寄生电感的补偿策略以及基于开尔文源极电感和功率源极寄生电感并联的补偿策略。通过仿真比较了两种无源补偿策略下的开关总损耗。最后,优化了基于开尔文源极电感和功率源极寄生电感并联的补偿策略,并通过双脉冲实验验证了此并联补偿策略下的动态均流效果。

The parallel structure of SiC MOSFET discrete devices has been widely used in medium and high power applications.To make full use of the advantages of the parallel structure, the problem of imbalanced dynamic current in the parallel structure should be solved.Among the characteristic parameters of SiC MOSFETs, threshold voltage is the most important parameter affecting the dynamic current balancing characteristics of the parallel structure.By establishing the circuit model of double-transistor parallel SiC MOSFETs, the compensation strategy of parallel dynamic current imbalance was investigated, and a formula was derived which illustrated the influence of threshold voltage on the dyna-mic current balance degree of SiC MOSFET switches.A double-transistor parallel circuit model with parasitic inductance was established.Two passive compensation strategies for imbalanced dynamic current in double-transistor parallel structure were proposed, that is, the compensation strategy of common source parasitic inductance and the compensation strategy of Kelvin source inductance in together with power source parasitic inductance.The total switching losses of two passive compensation strategies were compared through simulation.Finally, the compensation strategy of Kelvin source inductance in together with power source parasitic inductance was optimized, and the dynamic current balancing effect of this parallel compensation strategy was verified by double pulse test.