The reverse recovery charge (Qrr ) of the body diode in vertical power MOSFETs exhibits exponential time-dependent behavior that directly impacts converter efficiency, especially in hard-switching power topologies where careful dead-time optimization is required. The time-dependent behavior gets amplified with the increasing breakdown voltage rating (BVDSS) of Power MOSFETs (> 100 V). This article explores the evolution of Qrr as the forward conduction time transitions from nanosecond-scale pulses to hundreds of nanoseconds versus steady-state (DC) conduction. Using charge control theory, TCAD simulations, and double-pulse experimental measurements, we show that Qrr accumulates exponentially with forward conduction time, governed by the device’s minority carrier lifetime (TL), and saturates once the conduction period exceeds approximately three time constants.
These findings challenge the conventional approach to characterizing power MOSFET Qrr as a single datasheet parameter and highlight the limitation of current industry reporting for real-world switching applications. Consequently, we propose a new characterization methodology that illustrates the full time-dependent Qrr behavior in datasheets, offering designers more accurate tools for selecting and optimizing power MOSFETs in advanced converter designs.
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