Single-inductor multi-capacitor buck converter for high peak-to-average power envelope tracking

Abstract

A linear power amplifier (PA) is used for powering high-bandwidth modulated signals with high peak-to-average power ratio (PAPR). The efficiency of a PA significantly degrades using a fixed supply voltage, and an envelope-tracking (ET) power supply remains an essential alternative for improving the energy efficiency. This paper shows that a single-inductor multi-capacitor (SIMC) buck converter-based ET power supply can (a) achieve ultra-wide bandwidth for high PAPR envelopes and (b) simultaneously improve the overall dynamic energy efficiency of both the PA and the power supply. The proposed architecture employs a hybrid combination of inductive switching buck based ET power supply along with a bank of multiple output capacitors. This hybrid architecture is helpful to trade-off between the bandwidth and the output voltage ripple in order to preserve the linearity of PA. A hardware prototype is made. The experimental results are demonstrated to justify the effectiveness of tracking high-bandwidth PAPR envelopes while simultaneously minimizing the PA losses for low frequency envelopes. The SIMC buck converter achieves more than 85 % efficiency with the 7.5 W peak power level.