Design of a GaN-based High Frequency Buck Converter

Abstract

Power management integrated circuit (PMIC) of automotive electrical/electronic components are currently reaching limitations with silicon-based switches. Since the Gallium nitride (GaN) device has a higher power density than the silicon-based TR, it is easy to reduce the size and weight, and is suitable as a power transistor of a switching converter with high frequency operation due to low switching loss and on-resistance loss. Therefore, it is attracting attention as a next-generation power semiconductor device as it can expect effects such as lightening, improving conversion efficiency, and removing dedicated cooling systems when applied to electric vehicles. However, it has structural features different from existing silicon devices, so additional circuit design is required to use it as a switch. This paper relates to a GaN-based buck converter operating at a switching frequency of 10MHz.

In order to secure the problem of large overvoltage at deadtime due to the absence of a body diode, a block that stabilizes the voltage of the bootstrap (BST) node was added, and the standby current was reduced by using a pulse-driven level shifter. In addition, it operated at a high frequency of 10MHz and used a small inductor of 0.47uH. It was manufactured using the 0.18um high voltage BCDMOS process, and the input voltage is 12V and the output voltage is 5V. The designed area is 2500μm × 2500μm, and the maximum load current is 1A.