An Improved <i>di/dt</i>-RCD Detection for Short-Circuit Protection of SiC mosfet
Ju Xue, Zhen Xin, Huai Wang, Poh Chiang Loh, Frede Blaabjerg
Abstract
Silicon carbide metal-oxide-semiconductor field-effect transistor has a smaller short-circuit tolerance, and hence, requires faster and more accurate short-circuit protection. One prospective method is to combine fast di/dt detection with an integration circuit. The former is for detecting the extremely fast increase of short-circuit current, while the latter is for generating a scaled copy of the short-circuit current for comparison with a threshold. The integration is almost always performed with a resistive-capacitive (RC) low-pass filter due to its simplicity. However, it does not produce consistent results under different load and fault conditions, which can, in turn, cause the detection to fail. An alternative di/dt-RCD (RC + diode) protective circuit has therefore been proposed to offer more accurate and consistent results, irrespective of the fault types. Design equations for the circuit have been derived for implementing an experimental setup, from which results have proven the effectiveness of the proposed di/dt-RCD protection.