Device and Method for Limiting Di/Dt Caused by a Switching FET of an Inductive Switching Circuit

摘要

A circuit for limiting di/dt caused by a main switching FET during its turn-off against an inductive switching circuit is proposed. The circuit for limiting di/dt includes:An auxiliary inductor in series with the main switching FET for inducing an auxiliary inductive voltage proportional to di/dt.An auxiliary FET in parallel with the main switching FET. The auxiliary FET gate is connected to produce a gate voltage equal to the auxiliary inductive voltage. When the di/dt tends to exceed a pre-determined maximum rate of decrease, the auxiliary FET produces an auxiliary current component counteracting further decrease of the di/dt.;The main switching FET and the auxiliary FET can be formed from a single die with shared source and drain. The auxiliary inductor can be implemented as a parasitic inductance of an inherently required bonding wire connecting the main switching FET to its device terminal to simplify packaging with reduced cost.