Integrated Linear Regulator for GaN-based Gate Driver Applications

Abstract

GaN transistors with low input and output capacitance and zero reverse recovery characteristics enable efficient operation in half-bridge and bridge-based power drivers. Integrating GaN power transistors and their drivers in a single chip solves a number of challenges using GaN devices, which monolithically integrate all power stages to design low cost and high power density power converters. An internal regulator is generally required in such a power converter application. The regulator has a variety of functions, including a voltage source that provides a regulated voltage before the power driver starts up, and a power supply for external devices such as digital isolators for the high side driver signals. This paper presents a GaN-based linear regulator applied to power converter applications. All linear components use GaN devices as building blocks. The regulator consists of two common-source differential stages in a cascaded fashion to provide a high voltage conversion gain, as well as sufficient phase margins to reduce instability caused by rapid load transitions. The overall regulator was implemented in a GaN-on-Si process with maximum input and output voltages of 20 V and 6 V, respectively, at cost of 250 μA quiescent current. The regulator can source a maximum load current of 150 mA with the line regulation of 17 mV/V and the load regulation of 0.67 mV/mA. The maximum output voltage variation for a load current step change of 150 mA is within 400 mV. More than 65 dB PSRR above 1 MHz is achieved with the design.