The emergence of wide bandgap (WBG) semiconductor devices such as silicon carbide (SiC) and gallium nitride (GaN) devices promises to revolutionize next-generation power electronics converters. Featuring high breakdown electric field, low specific on-resistance, fast switching speed, and high junction temperature capability, these devices are beneficial for the efficiency, power density, reliability, and/or cost of power electronics converters. WBG devices have been employed in some commercial and industrial products with more applications expected in near future. However, extremely fast switching and other superior characteristics of WBG device, and high switching frequency/high voltage/high junction temperature operation, present new design challenges in gate drive and protection, packaging and layout, EMI suppression, and converter control, etc. Addressing these design and application issues is critical to the adoption, commercialization, and success of WBG based power electronics. This special issue intends to report the latest progress in these important areas. The Special Issue on Applications of Wide Bandgap Devices collected four papers on diverse topics, ranging from device performance degradation study, device gate drive and protection, to power module design, and eventually to sensing and control of converters in practical applications. The first paper is entitled “Performance Degradation of GaN HEMTs Under Accelerated Power Cycling Tests” written by Chi Xu and his colleagues at the University of Texas at Dallas, USA. This paper presents a comprehensive analysis of degradation performance in cascode and E-mode p-GaN gate devices under cyclic electrical and thermal stresses. The parametric variations show that the on-state resistance in both GaN device types gradually changes, which provides promising results as a degradation precursor. Furthermore, for the p-GaN gate device, the threshold voltage increases and transconductance decreases as the device ages, which offers an alternative degradation precursor. Failure analyses were also conducted on both devices. The cascode GaN devices show both short and open circuit failure modes, and a weak point in the drain-side bond wires is detected. For the p-GaN gate device, the electrical parameter shifts indicate a possible gate degradation after the device is aged. The second paper on the “Highly Compact Isolated Gate Driver With Ultrafast Overcurrent Protection for 10kV SiC MOSFETs” was contributed by Daniel Rothmund and his colleagues at the Swiss Federal Institute of Technology (ETH) Zurich, Switzerland. A highly compact isolated gate driver with a 20kV isolation voltage is implemented and tested in order to simplify the use of 10kV high-voltage SiC devices for a future intelligent medium voltage SiC module. The gate driver utilizes an encapsulated isolation transformer for its isolated power supply. This transformer with its primary winding and the secondary winding wound on separate ferrite core halves and separated by silicone insulation material, shows a volume of only 3.1cm³ and a coupling capacitance of only 2.6pF, and has been successfully tested at 20kV dc. Furthermore, an ultrafast overcurrent protection (OCP) circuit is implemented to protect the expensive SiC module from destruction due to overcurrent. The OCP circuit reacts within 22ns to a fault and measurements prove that it can successfully clear a hard switching fault (HSF) and even a flashover fault (FOF), where one of the two switches of a bridge-leg configuration is subject to a flashover, in less than 200ns for a dc-link voltage of 7kV. The third paper contributed by Lei Li and his colleagues from the Chinese Academy of Sciences, China is “A 1200V/200A Half-bridge Power Module Based on Si IGBT/SiC MOSFET Hybrid Switch”. In this paper, a compact hybrid switch (HyS) half-bridge power module, rated at 1200V/200A, was fabricated in house and fully tested for the first time. An electrothermal model of the HyS was set up to determine the optimal gate sequence for the HyS. To minimize the HyS power loss, the turn-on and turn-off timing sequences for the Si IGBTs and the SiC MOSFETs were discussed. And a novel index was proposed to select the optimal prior turn-off period. Compared with the pure Si IGBTs, the HyS module can operate at a higher switching frequency with a reduced power loss. A 5kW air-cooling voltage source inverter and a 30kW water-cooling voltage source inverter were developed and tested for verification. The last paper is “Impacts of High Frequency, High di/dt, dv/dt Environment on Sensing Quality of GaN Based Converters and Their Mitigation” from Bo Liu and his colleagues from the University of Tennessee, Knoxville, USA. This paper has reported a common phenomenon from a GaN based battery charger design, i.e., the high switching frequency, and high di/dt and dv/dt noise inside GaN converters may induce a dc drift or low frequency distortion on sensing signals. It provided a systematic study on different sensing distortions and their mechanisms. The identified mechanisms of different errors are strongly impacted by di/dt, dv/dt and switching frequency, all related to undesired high frequency behaviors of different amplifiers. Practical noise minimization techniques from noise source, propagation-path, and receptor are developed and experimentally verified. These techniques can improve the sensing quality and minimize the influences on feedback control. We would like to express our sincere thanks to the guest associate editors for their efforts spent selecting these high-quality papers for this Special Issue and the expert reviewers who have provided invaluable comments and inputs to assess and enrich the quality of the submitted manuscripts.