Active gate drivers and loss modeling for the investigation of the controlled shoot-through phenomenon

Abstract

Power electronics is becoming more important due to the need for e-mobility and the highly efficient and reliable systems required to beat climate change. The dual use of power electronics converters as heaters will be extremely helpful. In controlled shoot-through method, the controlled short-circuit is created to generate heat within the power electronics switches. This is helpful to heat-up complete power electronic converter, creating a controlled short circuit without damaging the device. This technique is useful for using a power electronic converter as a heater as well as a heating device in order to measure the on-state resistance of the MOSFET. The two-level (0, Vgs) active gate driver proposed for the controlled shoot-through technique, on the other hand, had limitations. The limitations in terms of variable gate voltage, need to manually make changes in the circuit to get different gate voltages etc. The limitations are overridden by developing three-level (0, Vgs ′ , Vgs); where Vgs ′ is dynamic gate voltage in between zero to Vgs. The gate driver has a variable third level gate voltage that can be as low as threshold voltage of the device, making it appropriate for testing SiC MOSFETs or GaN Devices. The controlled shoot-through was invented and tested on the SiC MOSFET. Therefore, while developing three-level converter the SiC MOSFET is considered. Traditionally, the series Zener diode is used for the generation of the shoot-through voltage. The transient impedance of the series Zener diode affects the gate sourcing current and results in a different gate voltage (Vgs) profile than without the series Zener diode condition. Therefore, a loss model considering lost area needs to be considered. In the case of a NO Zener diode in series, the shoot-through current is a square wave at low shoot-through current (self-heating does not start for low current). Therefore, the direct model can be used. If the self-heating of the MOSFET considered, the on-state resistance of the MOSFET changes due to the change in the junction temperature caused by drain current. The altered shape of the shoot-through current and respective loss models are discussed in-depth. The mathematical loss models considering self-heating are also developed. The thesis concludes with the future application of the developed gate driver for active discharge of DC-link capacitor through power modules, power electronic converter as a heater, extracting thermo-sensitive parameters by generating heat at the die level etc.