MOSFET gate charge control through observation of diode forward and reverse recovery behaviour

Abstract

The following paper presents an approach to gate charge control of a MOSFET used in low-side drive motor applications using pulse width modulation (PWM). Without gate charge control, ringing caused by di/dt effects on turn-on and dv/dt effects during the turn-off can result in narrowband radiated EMI that is very difficult to suppress. Suppressing narrowband EMI through the addition of suppression components can add cost and bulk to the controller. A simple, cost-effective solution based on discrete current control during MOSFET switching transitions is presented based on the observation of the forward and reverse recovery behavior of the freewheeling diode. The efficacy of this approach in mitigating narrowband radiated EMI emissions is presented through an analysis of circuit operation and simulation.