An Energy Recycling Envelope Tracking Supply Modulator Assisted by Small Cap Replica With 89.7% Efficiency and 37% Reduced Linear Amplifier Current for 150 MHz Bandwidth 5G New Radio RF Applications

Abstract

This article proposes an envelope tracking supply modulator (ETSM) that recycles the originally wasted energy in the linear amplifier (LA) to generate negative voltage <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {NEG}}$ </tex-math></inline-formula> and achieve fast down tracking. With the insertion of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {NEG}}$ </tex-math></inline-formula> , the negative slope of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{\mathrm {BUCK}}$ </tex-math></inline-formula> becomes 25% larger. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {NEG}}$ </tex-math></inline-formula> is also used to boost the input voltage of buck converter from 2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {BAT}}$ </tex-math></inline-formula> to 2.6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {BAT}}$ </tex-math></inline-formula> and raise the positive slope of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{\mathrm {BUCK}}$ </tex-math></inline-formula> by 93%, which improves the transient response of buck converter and decreases <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert I_{\mathrm {LA}}\vert $ </tex-math></inline-formula> by 37%. With energy recycling and high-bandwidth LA replica, ETSM supports 150-MHz 5G new radio (5G NR) application and achieves 89.7% efficiency when output power is 3.7 W. In addition, the proposed differential feedforward technique controls the operation of energy recycling precisely with the calibration logic.