A high-voltage multi-purpose on-the-fly reconfigurable half-bridge gate driver for GaN HEMTs in 0.18-μm HV SOI CMOS technology

Abstract

Nowadays, the use of Gallium Nitride (GaN) power transistors in power electronics is common, due to higher switching speeds, lower on-resistance and smaller size compared to silicon counterparts. With superior figures of merit, power converters utilizing GaN devices can operate at high switching frequencies, which translates into smaller size, higher efficiency and lower system cost. Redundancy and reconfigurability are highly desirable for safety-critical applications such as automotive and aerospace systems that operate under harsh conditions and require a high degree of flexibility together with high reliability. This thesis presents a gate driver for such a reconfigurable power system. Intended to be the core design of a programmable and flexible high-voltage (HV) power system, the gate driver in this work is capable of driving a wide range of GaN devices with different sizes by having independently configurable turn-on and turn-off resistance paths. This feature eliminates the need for discrete gate resistors and allows for higher density designs, such as System-in Package integration (SiP) where the gate drivers, GaN devices and other control integrated circuits are placed on the same interposer. Reconfigurable driving strength also allows for electromagnetic interference (EMI) reduction, which is important in safetycritical applications. A uniform structure of half-bridge switching units is proposed, enabling reconfigurability in the operation of the system with a variety of possible topologies, out of a large array of switching cells. The gate driver requires a built-in 200-V level shifter, with common-mode noise cancellation technique, thoroughly investigated and migrated to HV SOI technology, which is immune against a 80-V/ns slew rate of fast switching GaN devices despite excessive parasitics in the process and the packaging technique employed. The gate driver has a configurable dead-time ranging from 5 ns to 60 ns that minimizes loss due to so-called “body diode” conduction of the GaN FETs during freewheeling for different load profiles. All the configurations are set via shift registers. The gate driver has been fabricated in a 200-V 0.18-μm silicon-on-insulator (SOI) process (XFAB XT018). Measurement results show that the chip can drive targeted GaN HEMTs from smallest to largest size at the desired turn-on and turn-off speeds, as fast as 1.46/1.18 ns of rise/fall-time. The measured dead-time is from 4.5 ns to 58 ns with an input voltage up to 86 V. The parameters can be reconfigured on-the-fly at a pulse width modulation switching frequency up to 20 MHz. This work contributes to the advancement of universal gate driver design, especially for GaN transistors, and toward reconfigurable power systems.

Date	22 Jun 2020
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Nicolas Constantin (Supervisor) & Glenn Cowan (Co-supervisor)