A Monolithic Depletion-Mode GaN-Based Buck Converter With Integrated RCD Dead Time Generator for Envelope Tracking Power Amplifier

Dead time is a critical technology for improving converter efficiency. This brief presents the first monolithic depletion-mode (d-mode) GaN-based dc-dc buck converter with an integrated dead time generator (DTG). The proposed generator leverages the unidirectional conductivity of diodes in a resistor-capacitor-diode (RCD) topology to generate different delay times for the rising and falling edges of the input PWM signals, thus creating a dead time. The converter is designed using a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.25~\mu $ </tex-math></inline-formula>m d-mode GaN-on-Si process. Measured results demonstrate that the integrated generator can provide a dead time of around 0.4 ns. With the integrated DTG, the peak power-stage efficiency of the converter improves by 4.3%, reaching 86.2%, and a peak output power of 3.5 W at a switching frequency of 100 MHz. Additionally, the GaN converter was tested as an envelope tracking supply modulator (ETSM), achieving an efficiency of 83.4% and an average output power of 3.76 W for an envelope signal with a 20 MHz bandwidth and a 6.5 dB peak-to-average ratio (PAPR).