Design of Single-Turn Air-Core Integrated Planar Inductor for Improved Thermal Performance of GaN HEMT-Based Synchronous Buck Converter

Gallium nitride (GaN) high electron mobility transistor (HEMT) has a lateral device structure with wafer-level packaging, which is advantageous in minimizing parasitic parameters and overall device size. This type of packaging also has better thermal performance than conventional packaging due to low junction-to-bottom thermal resistances. It indicates copper layers in printed circuit boards can effectively serve as heat dissipation channels for the switching devices. When these copper traces and pours in the vicinity of the switching devices are carefully designed and shaped, they can also be utilized as an integrated output filter. In this article, a synchronous buck converter with a single-turn air-core integrated planar inductor is proposed to achieve both zero-voltage switching and high thermal performance of the GaN HEMTs. A new planar inductor design flowchart is introduced, and analytically estimated inductance and resistance are verified with simulation and experiment. Three different inductors are designed and fabricated to prove the improved thermal performance of the proposed converters.