Modern High Voltage GaN FETs - Power Applications and Impact of Packaging Technology

Abstract:
To make use of the outstanding switching performance of modern GaN devices, manufacturers have decided to follow new approaches in packaging with a strong focus on low-inductance surface-mount devices (SMD). In this paper, the performance of a fast 33mW cascode gallium nitride (GaN) device in a modern copper-clip package (CCPAK) is evaluated and compared with a similar part, housed in standard TO-247 with three pins (TO-247-3). First, a theoretical analysis of the switching waveforms in a half-bridge circuit with inductive load is conducted and the impact of the package inductance on the waveforms is discussed. A special focus is put on the detrimental impact of the common source inductance and how some of it can be mitigated by using additional gate ferrite beads. Simulation and practical measurements in double pulse and continuous buck converter operation are presented to confirm the analysis. While it becomes clear that the modern low-inductance SMD package has an edge in performance at high power and high current as well as emitted interference, the evaluated hard-switching buck converter circuit shows that very good efficiency beyond 99% at 100 kHz and up to 4kW can still be achieved with devices packaged in traditional TO-247.