A novel fast on-state voltage monitoring circuit using series SiC diodes as high-voltage diodes for high-frequency MOSFETS

This paper presents a novel current-mirror-based on-state voltage monitoring circuit (OVMC) tailored for high-voltage, high-frequency Silicon Carbide (SiC) MOSFETs, effectively overcoming the limitations of conventional measurement approaches under fast-switching conditions. Unlike prior designs that rely on operational amplifiers and large auxiliary circuits, the proposed topology integrates a compact current mirror and a resistor–capacitor (RC) filter to achieve precise voltage sensing with minimal footprint. PSpice simulations and experimental validations on both signal generator and a PFC prototype confirm that the SiC-diode OVMC achieves a delay reduction of up to 70% compared to silicon(Si)-diode configurations, with effective suppression of voltage overshoot via optimized RC compensation. Contrary to the conventional assumption that junction capacitance dominates switching speed, the study demonstrates that minority-carrier storage and reverse charge removal in Si PN diodes are the primary delay sources. In contrast, SiC Schottky diodes—being majority-carrier, unipolar devices—exhibit nearly instantaneous charge balance and therefore faster transition between forward conduction and reverse blocking.