Design Considerations and Development of an Innovative Gate Driver for Medium-Voltage Power Devices With High $dv/dt$

Medium-voltage (MV) silicon carbide (SiC) devices have opened up new areas of applications which were previously dominated by silicon-based IGBTs. From the perspective of a power converter design, the development of MV SiC devices eliminates the need for series connected architectures, control of multilevel converter topologies which are necessary for MV applications, and the inherent reliability issues associated with it. However, when SiC devices are used in these applications, they are exposed to a high peak stress (5-10 kV) and a very high dv/dt (10-100 kV/μs). Using these devices calls for a gate driver with a dc-dc isolation stage that has ultralow coupling capacitance in addition to be able to withstand the high isolation voltage. This paper presents a new MV gate driver design to address these issues while maintaining a minimal footprint for the gate driver. An MV isolation transformer is designed with a low interwinding capacitance, while maintaining the clearance, creepage, as well as insulation standards. A dc isolation test has been performed to validate the integrity of the insulating material. The key features include low input common mode current, and a short-circuit protection scheme specifically designed for 10 kV SiC MOSFETs. The performance of the gate driver is evaluated using double pulse tests and continuous tests. Experimental results validate the advantages of the gate driver and its application for MV SiC devices exhibiting very high dv/dt. The proposed gate driver concept is aimed at providing an efficient and reliable method to drive MV SiC devices.

I. Introduction

With the advancement of wide bandgap semiconductors, power devices such as silicon carbide metal-oxide-field-effect transistors (SiC-mosfets) and silicon carbide insulated-gate-bipolar transistors (SiC-IGBTs) are now available with blocking voltages up to 15 kV [1]. A 4H-SiC n-IGBT with a blocking voltage up to 27.5 kV is demonstrated in [2]. Applications which require a blocking voltage of 1.2–10 kV are primarily dominated by SiC mosfets owing to its small on-state resistance [3]. While gate drivers are commercially available for SiC devices with a blocking voltage range of 650–1700 V, there are a very few commercial gate drivers for 10 kV SiC mosfets due to the challenges associated with them [4]. The MV SiC mosfets’ fast switching transients can result in a as high as 100 kV/s, which imposes a requirement for a very low isolation capacitance in the gate drive circuit [5], [6]. Also, the severe stresses reduces the lifetime of the insulation material over time [7].