功率器件的并联均流研究

Research on Current Sharing of Parallel Power Devices

在新能源汽车的电机控制器中,由于现有模块电流能力不够、成本过高、散热能力有限,常常使用多个功率器件并联,以提高电动汽车应用的功率逆变器载流能力。器件参数的公差、PCB布局不对称导致的寄生参数不一致以及散热器的冷却效果导致的热量堆积,都会导致电流不均衡现象。首先对电流不平衡的原因进行了概述,提出均流系数作为电流平衡的标准。给出了基于热阻的导通电阻模型,分析并联器件静态均流的影响因素。基于可变电阻区的电压电流曲线,分析了并联器件动态均流的影响因素。通过PSPICE建模分析了寄生电感对动态均流的影响,分析了参数差异对电流平衡的的影响,针对不同的参数差异,提出了不同的优化方法。最后分析了电磁兼容问题对均流特性的影响,给出驱动电路的设计建议,并对栅极电压波形的优化效果进行了仿真验证。

In the motor controller of new energy vehicles,due to insufficient current capacity,high cost,and limited heat dissipation capacity,parallel power devices are often used to extend current capability of power inverter for EV applications. Current imbalance can be caused by device parameter tolerances,parasitic parameter inconsistencies due to asymmetric PCB layout,and heat accumulation due to the cooling effect of the heat sink. Firstly,the causes of current imbalance were summarized,and the current sharing coefficient,that is the unbalance ratio,was put forward as the measuring standard of current balance. The conduction resistance model based on thermal resistance was presented,and the influencing factors of steady current balance of parallel devices were analyzed. Then,based on the voltage and current curves in the variable resistance region,the influencing factors of dynamic current balance of parallel devices were analyzed. The effect of parasitic inductance on dynamic current balance was analyzed by PSPICE simulation,and the influence of parameter difference on current balance was analyzed. Different optimization methods were proposed for different parameter differences. Finally,the influence of EMI on the current sharing characteristics was analyzed,and the design of the drive circuit was suggested,and the optimization effect of the gate voltage waveform was verified in the simulation.