Modern power switches like Si-MOSFETs, SiC-MOSFETs, and Si-IGBTs are controlled by voltage applied to the gate. While Si-MOSFETs typically require 0 V to +10 V for switching, SiC-MOSFETs and Si-IGBTs perform best at +15 V and often need a negative bias of -3 V to -8 V to ensure reliable off-states.
Designers must account for total gate charge, which varies non-linearly with bus voltage. For example, a Wolfspeed C3M0032120K SiC-MOSFET with a 118 nC gate charge, when switched at 100 kHz with a 19 V swing, requires 0.224 W of drive power. Key design factors include switch placement, peak voltage and current, isolation requirements, and switching frequency.
Low-side switches are often driven directly by controller ICs, but specialized gate driver ICs offer features like Miller clamping and desaturation detection for overcurrent protection. High-side or floating switches require more complex solutions, such as pulse transformers, level-shifting driver ICs, or fully isolated gate driver ICs.
Pulse transformers are limited by duty cycle constraints, while level-shifting ICs like the Infineon IR2110 use bootstrap charge pumps but lack galvanic isolation. Isolated gate driver ICs, using optical, magnetic, or capacitive techniques, provide galvanic isolation and high common-mode transient immunity, often exceeding 100 V/ns, making them suitable for EV applications.
