While silicon carbide power mosfet s have significantly superior figures-of-merit in comparison to conventional silicon devices, they have seen relatively limited adoption in high-power applications due to intrinsic reliability concerns. One of the most consistent precursors of early device failure is increased on-state resistance (R $_\mathrm{ds-\text{on}}$ ). This article presents the design of a nonintrusive health monitoring circuit (HMC) that can be embedded within the power converter to measure this resistance during operation. The HMC does not require load current information or any interaction with the gate driver. It is experimentally validated for a range of voltage and current levels including continuous operation in a buck converter and provides estimates of R $_\mathrm{ds-\text{on}}$ within $\pm$ 5% of the true value for all cases.

Gallium Nitride Enhancement-Mode High Electron Mobility Transistors (GaN HEMTs) help to achieve high power density converter circuits thanks to their superior efficiency, higher switching speed and small package size. However, increased switching speed results in a sharp increase in short circuit (SC) current under a shoot-through fault with respect to other type of devices. GaN HEMTs can withstand the SC current only for several hundred nanoseconds. Therefore, fast SC protection solutions are critical for protecting power circuits. In this paper, the voltage induced by high slew rate of SC current on the high frequency power loop inductance resulting from the printed circuit board (PCB) layout is sensed to implement an ultra-fast short-circuit protection technique. The proposed technique does not increase circuit parasitics and provides flexibility in layout design that makes it suitable for parallel connected GaN HEMTs, which require symmetric layout design for equal current sharing. A multi-pulse test is conducted under 1.56 MHz switching frequency, 400 VDC bus voltage and 40 A load current by using parallel connected GaN HEMTs in a half-bridge configuration to verify the robustness and reliability of the proposed protection technique. Experimental results show that the proposed protection technique is able to detect SC fault within 40 ns and fault is completely cleared with a soft turn-off in 250 ns.

Wide-band-gap technologies enable ultra-high efficiencies in high-frequency power conversion. However, inadequate accuracies in electrical measurements could lead to spurious efficiency measurements, even above 100%. Furthermore, bandwidth limitations, particularly for current probing, delay mismatches between current and voltage probes, loading effects and electromagnetic interferences make electrical techniques inappropriate for measuring extremely-low losses in switches with high dv/dt and di/dt values and magnetic components with high-frequency excitations. Calorimetric methods overcome this issue by a direct loss measurement through the generated heat. Nevertheless, limited ranges and accuracies of existing systems hinder their application in sensitive measurements. Moreover, time-consuming calibrations with extensive data processing impede rapid design assessments. In this work, we propose a closed-type double-chamber calorimeter based on a real-time calibration between two identical chambers, to eliminate extra compensation for ambient variations or changes within the system itself. By streaming the same coolant in both chambers, our system removes the need for flow measurements, enabling extremely low flow rates which improves sensitivity and reduces complexity and system cost. The system provides adjustable cooling and can measure losses down to 500 mW, enabling the evaluation of high-performance power converters and their components with no dependencies on the geometries of the evaluated devices or systems.