Hybrid Power Cell using Si IGBT & SiC MOSFET

Abstract:
Nowadays, Silicon Carbide (SiC) power modules are often thought to improve the efficiency and size of power converters. However, these components are new on the market and there is no feedback as to their ability to work during for a long time, especially in applications in which there are thermal cycling constraints. Moreover, their prices remain much higher than the standard Si power modules. Thus, for the applications requiring much thermal cycling, met in traction systems under a competitive market, SiC power modules cannot be considered yet. This paper describes a hybrid topology mixing a Si IGBT power module with a SiC MOSFET component called a Hybrid Power Cell (HPC). In the HPC concept, the IGBT is used to sustain thermal cycling whereas the SiC MOSFET is used only during the switching times. Thus, power losses in the SiC MOSFET component are low which drastically reduces its thermal cycling stress. This allows using any kind of SiC package. In addition, soft switching has been used on the one hand to reduce common mode current met in SiC applications using hard switching, and on the other hand, to multiply by 3 the limit of the switching frequency of the Si IGBTs working in hard switching. Thus, for medium power applications (~100kW) size and weight can be drastically reduced. In the HPC concept, the SiC MOSFET chip is much smaller than those used by the SiC power module, resulting in a suitable price to address the aggressive markets.