开尔文连接对功率模块并联均流影响的对比评估
Evaluation on Current Sharing of Power Module Affected by Kelvin Connection
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摘要: 多芯片并联功率模块是新能源发电等大功率电能变换领域的核心部件。由于功率模块的封装布局不均,造成并联芯片的动静态电流分配不均衡,进而降低功率模块的容量、威胁变流器的可靠运行。改进多芯片并联功率模块的封装,是解决并联电流分配失衡的有效方式,也是实现电力变流器大功率运行的必要条件。该文针对一款常用的商业化IGBT功率模块,对比研究开尔文连接对多芯片并联均流的影响。考虑封装寄生参数,建立功率模块的等效电路模型和有限元分析模型,从路和场的角度,揭示开尔文连接对芯片间暂态电流不平衡的影响。基于定制化的功率模块和双脉冲测试平台,通过仿真和实验结果,对比研究功率模块有/无开尔文连接时,并联芯片间的电流不均衡效应。结果表明:开尔文连接能够实现功率回路和门极回路的解耦,提高器件的开关速度;但是,开尔文源极的引入改变了功率模块布局,对多芯片并联均流提出了挑战。后续还需要研究直接覆铜板的优化布局方法,消除并联芯片间的回路不对称。Abstract: High capacity power module with multiple chips in parallel is a key element for renewable energy integration and electrified transportation applications. Imbalance electro-thermal stress in a multi-chip power module challenges the high power capacity applications. Advanced packaging is considered as a promising solution toward next-generation power electronics. In this paper, based on a commercial power module packaging, to enhance the current sharing in the multi-chip power module, the capability of auxiliary Kelvin connection to limit the transient imbalance current among parallel chips was comparatively surveyed. Taking parasitics into account, electric circuit and finite element analysis were proposed to illustrate the influences of Kelvin connection. Based on customized power modules and a test rig, simulation and experimental results were presented to comprehensively demonstrate the current sharing of parallel chips affected by Kelvin connection. It reveals the capability to eliminate imbalance current by using Kelvin connection is limited. Optimized direct bonded copper(DBC) layout to eliminate the asymmetric loops is needed for multi-chip modules.