A Monolithic D-Mode GaN-Based Buck Converter With Novel Resistor–Capacitor-Multiplexing Dead-Time Adjustment Structure for Envelope-Tracking Power Amplifier Application

This letter reports a monolithic high-efficiency buck converter using all depletion-mode (d-mode) gallium nitride (GaN) HEMTs which integrates a dead-time generating driving circuit and a power stage. A novel resistor-capacitor-multiplexing (RCM) structure is proposed, where the resistor functions for both pull-up and dead-time adjustment, and the capacitor is used for both level-shifting and dead-time adjustment. Therefore, dead-time can be adjusted without introducing additional paralleled capacitors, enabling the RCM structure to sharpen the rising and falling edge of the power stage’s gate signal, thereby improving both switching frequency and efficiency. This buck achieves a peak efficiency of 90.7%, delivering an output power reaching 11.6 W at a switching frequency of 112.5 MHz. A power amplifier (PA) is supplied by the proposed circuit serving as an envelope-tracking supply modulator (ETSM) for the verification of envelope-tracking power amplifier(ET-PA). The overall efficiency of the ET-PA was increased by 14.3% compared with the PA with fixed supply voltage. To the best of the authors’ knowledge, this is the first report of a monolithic all-d-mode-GaN-based buck with an integrated dead-time generator.