Gate Driver Concept for Parallel Operation of Low-Voltage High-Current GaN Power Transistors for Mild-Hybrid Applications

In this work experimental and simulative proof of a concept for paralleling low voltage and high current Gallium Nitride (GaN) transistors each with a distinct gate booster is presented. For both high-side (HS) and low-side (LS), two 100V 5mΩ normally-off GaN-HEMTs are operated with a driver, which offers separate paths for turn-on and turn-off. In combination with the Kelvin source a minimal gate-loop inductance and stable switching operation is achieved. The HS and LS signals are provided by an isolated half-bridge driver with ultra-low jitter and identical PCB path lengths to ensure equal propagation delay. The half-bridge with paralleled GaN-HEMTs, which is approved by full-wave S-parameter extraction in combination with a comprehensive thermal simulation and a transient simulation based on a physical GaN model, is operated in a 300kHz48V-to-24V buck converter operation up to 54A output current with an overall efficiency of above 95%. The output power of the converter is mainly limited by the thermal performance of the packaging and the PCB and the single gate-contact of the transistors, which is reducing the degrees of freedoms in the layout and introducing significant common source and parasitic inductances.