Experimental Characterization of Silicon and Gallium Nitride 200 V Power Semiconductors for Modular/Multi-Level Converters Using Advanced Measurement Techniques

The increasing demand for higher power densities and higher efficiencies in power electronics, driven by the aerospace, electric vehicle, and renewable energy industries, encourages the development of new converter concepts. In particular, modular and/or multi-level (M/ML) topologies are employed to break the performance barriers of the state-of-the-art power converters by simultaneously reducing the system losses and volume/weight. These improvements mainly originate from the replacement of high-voltage transistors, typical of two-level converters, with low-voltage, e.g., 200 V, devices, offering superior electric performance. Hence, two low on-state resistance silicon (Si) and gallium nitride (GaN) 200 V power semiconductors are comprehensively characterized in this article to support the multi-objective optimization and the design of M/ML power converters. First, the selected devices are analyzed experimentally determining their conduction, thermal, and switching characteristics; for this purpose, a novel ultra-fast transient calorimetric measurement method is introduced and explained in detail. In the course of this analysis, an unexpected switching loss mechanism is observed in the Si devices at hand; the physical reason of this behavior is clarified and it is proven to be solved in the next-generation research samples, which are also characterized by measurements. Finally, the influence of the measured power semiconductors' performance on the overall efficiency and power density of a typical converter is determined through a case study analyzing a hard switching half-bridge operated as a single-phase inverter, i.e., the fundamental building block of several M/ML topologies. It is concluded that, in this voltage and power class, GaN e-FETs are nowadays approximately a factor of three superior to Si power MOSFETs; however, the better heat dissipation achieved by the latter still makes them the preferred solution for higher power applications.