Analysis of cascaded silicon carbide MOSFETs using a single gate driver for medium voltage applications

摘要

Medium voltage power supplies for applications such as electrostatic precipitators are used in industrial plants to remove particles from fumes. Current solutions based on silicon devices rely on high-voltage transformers to reach the required output voltage levels. New wide band gap materials such as silicon carbide have higher electric breakdown voltage, and thus fewer devices are required in series to withstand the output voltage. Owing to the faster switching speed of silicon carbide devices further demands are put on the serialisation method. In this study, a cascaded series-connection method using only a single external gate signal is analysed in detail, guidelines to size the resistor-capacitor-diode-snubber are proposed and its applicability is experimentally demonstrated. The circuit is tested with four series-connected devices in a double pulse test at 2400 V and current levels of 250-800 mA to show the load dependence. The serialisation technique is tested in a boost converter operating in discontinuous conduction mode but is limited to 1200 V due to an oscillating state occurring after zero current crossing. Finally, the technique is tested at 2400 V and 10 kHz in a synchronous boost converter, which demonstrates the proposed design guidelines.