Study of the gate drive circuit on the electromagnetic radiation

Abstract

High speed switching pulse-width modulation (PWM) converters generally produces electromagnetic (EM) radiation. This final year project aims to study the gate drive circuit on EM radiation during the switching interval of buck converter. High speed MOSFET switching operation and characteristics were discussed and the waveforms of switching voltage and current were embedded. And furthermore, both turn-on and turn-off snubber circuits were designed for reducing the effect of three parasitic capacitors (CGD, CGS, CDS) of switching power MOSFET. By reducing the ringing of switching voltage and current can be reduced effectively, the EM radiation of switching MOSFET can be decreased and switching frequency of buck converter was increased to 700 kHz. Also, the turn-on and turn-off portion of the switching voltage and current of the MOSFET can be shaped. In addition, negative current (iD) was produced of the power MOSFET in buck converter during switching. Simulation results, hardware experimental results, EMC scanning results, and EMC frequency spectrum were embedded.