Multi-Phase Three-Level Buck Converter with Current Self-Balancing for High Bandwidth Envelope Tracking Power Supply
Srikanth Yerra, Harish S. Krishnamoorthy
Abstract
Envelope Tracking (ET) is a power supply modulation technique for a radio frequency power amplifier (RFPA), primarily employed to improve its efficiency. This paper presents the design and performance analysis of a two-phase three-level buck converter, then compares it with its two-level counterpart for ET power supply application. Gallium Nitride (GaN) MOSFETs switching at 25 MHz are selected as power stage devices and Zero Voltage Switching (ZVS) technique is used for better efficiency. A fourth-order ZVS - low pass filter (LPF) is designed to track a 20 MHz large bandwidth envelope signal and also to maintain the current self-balancing in the multi-phase converter system. The efficiency of the proposed design peaks 97.5 % at 115 W and has an average efficiency of 94.5 % at 26 W. Simulation results evince precise tracking of 20 MHz, 4G LTE envelope signal with 10 dB Peak-to-Average Power Ratio (PAPR). Performance analysis indicates that the three-level option has improved average power efficiency for higher bandwidth ET applications.