# Parasitic-Based Active Gate Driver Improving the Turn-On Process of 1.7 kV SiC Power MOSFET
## 1 Introduction
The AGD provided promising results in case of the turn-on and turn-off cycles. Unfortunately, the authors examined this solution only for low currents so it is not known if this approach could be used in high-power applications. The AGD can be also used as a short circuit protection of the device through the employment of a Rogowski coil to measure the current and use it as a feedback signal [12]. In this particular case, the AGD was designed for a 1.7 kV/325 A MV SiC MOSFET. Unfortunately, this solution generates additional expenses to the summary AGD cost as it needs an auxiliary circuit to be used in case of a feedback loop. In addition, the AGD can be used for voltage balancing in series connection of a 1.7 kV half-bridge SiC MOSFET module, which is the main topic in the paper [13]. As the closed-loop test results showed, the authors accomplished balancing of the drain-source voltage values in series connection in comparison to natural voltage sharing. In this case, the feedback signal of the AGD was acquired with a switch voltage sensor based on an RC branch connected to the drain of the SiC MOSFET. The main weakness of this solution was that the quantity of switching energy losses increased by less than 7.5%. Furthermore, the AGD can be used for SiC MOSFET oscillations damping [14] as well. In [14], the authors solved problems with overshoot and ringing in the body diode under inductive load. The subject of the experimental studies in this case was a 1.2 kV/36 A discrete SiC MOSFET which was tested with only a 400 V DC bus. The results indicated that the AGD had an impact on the oscillations and successfully suppressed them. However, in case of MV voltages, power modules are usually characterized by higher parasitic inductances and capacitances, and it is much more complicated to use closed-loop solutions due to disturbances in the feedback signals. Moreover, there are studies with an AGD for a 1.7 kV SiC MOSFET where the feedback loop is based on the parasitic inductances of the source and drain [15], and the multi-level gate voltage method is used for turn-on and turn-off cycle improvement. The application of the AGD reduced the turn-on energy by 30% for the 1.7 kV SiC MOSFET and showed a positive impact on EMI performance. To avoid high propagation delays, the main control unit of the AGD in this paper was based on a CPLD; alas, it made the whole device more complex. A multi-level gate voltage method for a 3.3 kV/450 A SiC MOSFET in open loop was described in [16]. This method was verified in a double-pulse test (DPT) and in a half-bridge inverter. The turn-on energy decreased by half through the manipulation of the gate driver supply. As a result, the PWM frequency of the inverter can be doubled. However, the gate driver works in open loop which limits the system capabilities for variable drain currents. According to the literature review, it can be seen that active gate drivers are discussed mostly for low-voltage and -current transistors, while those for 1.7 kV SiC MOSFET power modules are rare [12; 13; 15]. Moreover, a lot of the articles presented discrete 1.2 kV SiC MOSFETs [9; 10; 11; 14]. Some of the AGDs proposed in the papers are for MV; however, they have limited drain current capabilities, thus excluding them from most high-power applications. Therefore, the subject of this paper is to show simulation results and experimental validation of an AGD for MV and a high-current SiC MOSFET based on a power module. The closed-loop AGD for a 1.7 kV/325 A SiC MOSFET proposed in this paper uses voltage measurement across the parasitic source inductance to simplify the measuring circuit. Unlike most of the presented AGDs in the literature, this kind of feedback loop does not generate any additional energy losses to the system. Additionally, the AGD improves the turn-on cycle of the device by manipulation of the gate voltage to decrease the dissipated energy by increasing the \(dv_{DS}/dt\) ratio and suppressing the drain current oscillations.