A Modular Cascaded Multilevel Buck Converter Based on GaN Devices Designed for High Power Envelope Elimination and Restoration Applications

Envelope tracking (ET) and envelope elimination and restoration (EER) are crucial techniques which can significantly improve the efficiency of radio frequency power amplification (RFPA) system in RF communication applications. The two techniques gain more and more attention and progress in recent years, benefitting from the excellent switching characteristic of wide band-gap power devices. Envelope amplifier (EA), a high bandwidth DC/DC converter, is entailed in both techniques to precisely amplify the envelope of communication RF signal. This paper proposes a modular cascaded multilevel Buck converter operating as EA for high power envelope elimination and restoration applications. PWM modulation and capacitor voltage balance control methods are investigated. In addition, a half-bridge circuit cell (HBCC) using GaN devices with thermal design is presented. A five-level prototype based on this HBCC is fabricated, which can provide 500W peak power and accurately track an envelope signal with bandwidth near to 400kHz.