Study of Voltage Balancing Techniques for Series-Connected Wide-Bandgap Semiconductors Devices

Higher cost, lack of availability, and higher on-resistance (RDSon) are just a few drawbacks of semiconductor devices at higher voltages. This applies to the wide-bandgap semiconductors like Silicon Carbide (SiC) MOSFETs as well, where individual devices are not commercially available at voltages above 3.3-kV at the time of preparing this paper. Series connection of individual semiconductor devices is an effective way to achieve higher-voltage switches. However, the inherent unequal static and dynamic voltage sharing problems between the devices in the stack need to be addressed. The majority of the existing voltage balancing schemes are developed for slow-switching Si-based semiconductors, and bring about a significant amount of additional losses in the control circuit or on the switches. Some other techniques are not practical on SiC MOSFETs, given the high switching speeds featured by these devices. This paper tries to survey and compare the voltage balancing techniques proposed by researchers for being used on the faster-switching wide-bandgap devices. The voltage balancing techniques proposed in literature are classified into 5 different categories of “passive solutions”, “self-powered and pulse-powered gate drivers”, “active gate control techniques”, “gate timing control methods” and “voltage clamping solutions”. Then, a comprehensive and unbiased comparison is conducted between different voltage balancing techniques from “cost”, “modularity”, “complexity”, “startup balancing”, “losses” and “voltage balancing” points of view. Finally, conclusions from the conducted comparison are discussed.