Medium Frequency Output Impedance Limits of Switched-Capacitor Circuits

Abstract

As an intrinsic power loss of switched-capacitor circuits (SCCs), capacitor charge-sharing loss reduces the system efficiency. In this article, the approach based on q-u curves of capacitors is proposed to calculate capacitor charge-sharing loss precisely. By considering both capacitor charge-sharing loss and conduction loss, the output impedance of an SCC with a finite output capacitance can be modeled accurately in medium switching frequency. Compared with the previous modeling techniques, the proposed modeling method called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LSL</sub> not only counts the output capacitor effect but also applies to a wide range of well-posed switched capacitor circuits. Several high-order SCCs are taken as examples to validate the accuracy of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LSL</sub> via simulations and experiments and it could be corroborated that <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LSL</sub> can predict the output impedance precisely with the change of switching frequency, output capacitor, and duty cycle in the mid-band.