Driving and sensing design of an enhancement-mode-GaN phaseleg as a building block

The approach of integrating a GaN phaseleg, current-boost drivers, and decoupling capacitors can significantly minimize the power loop inductance and the gate loop inductance. However, the driving scheme and sensing scheme are still critical and challenging in order to survive the highly noisy environment due to the GaN switching. A driving scheme of digital isolator plus isolated power supply is used for both switches of the phaseleg. To suppress the noise propagated to the PWM generating board, a common-mode choke and two Y-capacitors are used. A GaN boost converter proved the reduction of noise current through the PWM cables. For the sensing circuit design, filtering is necessary for all the sensors. Even with the filters, it turns out that only the DC current sensor can be placed with the phaseleg while the DC voltage sensor and AC current sensor have to stay away from the high dv/dt and di/dt nodes.