A GaN-Based Digitally Controlled DC-DC Buck Converter with an ADC-Based Digital Controller and Soft-Start Function

This paper presents a gallium nitride (GaN)-based digitally controlled DC-DC buck converter featuring an analog-to-digital converter (ADC)-based digital controller and a digital soft-start function. The proposed digital soft-start function is designed to prevent overshoot and limit excessive inductor current during start-up, without degrading the settling time. The proposed ADC-based digital controller significantly reduces the size of off-chip passive components required for GaN-based DC-DC converters and enables a fast transient response to high load current changes. The proposed DC-DC buck converter comprises a Bipolar-CMOS-DMOS (BCD)-based gate driver IC and half-bridge GaN power switches. The proposed gate driver IC is implemented in a 0.18- μm BCD process. The proposed 10-MHz, 30V-to-12V DC-DC buck converter achieves a settling time of 15 μs and a maximum power efficiency of 91.7% at a load current of 2.6 A.