High-Frequency Pulsed Laser Driver Using Complementary GaN HEMTs

This article attempts to disclose a high-efficiency laser driver that controls laser sources for high-frequency light detection and ranging (LiDAR) applications. The specific LiDAR requisites encompass a 20-MHz laser repetition rate, a 10-ns pulse duration, and an instantaneous power of 50 W. The power efficiency of a LiDAR used in autonomous vehicles is critical, which shall yield a total input power within 15 W. To enhance power efficiency, a half-bridge pulse laser drive is proposed, featuring a depletion mode gallium nitride (D-mode GaN) transistor on the high-side and an enhancement mode (E-mode) GaN transistor on the low-side. A high-side gate drive is also introduced and analyzed for the D-mode GaN transistor, which can greatly minimize oscillation during laser-pulse capacitor charging due to no body diode effect. Key efficiency factors include the equivalent series resistance of multilayer ceramic capacitor, high-side transistor switching loss, and transistor resistive loss. A peak efficiency of 75% is found at the compromise of all losses, which is verified in both theoretical and experimental methods. The pulse laser drive operation is proven to be stable in the experiments over a wide range of laser repetition rates from 10 kHz to 20 MHz.