Fluctuation analysis and experimental evaluation of an inductor-less battery charge equalization circuit with a CMOS cross-coupled structure

Abstract

A lithium-ion battery for mobile devices obtains a desired voltage by connecting a plurality of battery cells in series. However, the variation in the voltage of each battery cell shortens the lifetime of the battery. For this reason, a battery charge equalization circuit called a battery equalizer (BE) is commonly used. Among others, an inductor-less switched-capacitor (SC) BE is one of the most promising circuits, because it enables low cost, easy control, low EMI, and IC integration. However, to the best of our knowledge, there has been no research on the effects of element variation in inductor-less SCBEs. In this paper, the effect of circuit element variation is investigated regarding the inductor-less SCBE. Specifically, we use Monte-Carlo simulations to clarify the effects of circuit element variation in an inductor-less SCBE with a CMOS cross-coupled structure. Furthermore, the feasibility of the inductor-less SCBE is confirmed by experiments on a laboratory prototype circuit.