Complex programmable logic device-based closed-loop implementation of switched-capacitor step-down DC–DC converter for multiple output choices

Abstract

A complex programmable logic device (CPLD)-based closed-loop switched-capacitor (SC) step-down DC–DC converter is implemented for multiple output choices (9/5 V, 3.3, 2 V). For a variety of output choices, various Verilog-code control rules are designed and embedded into the CPLD-based controller for the closed-loop regulation of SC converter. Such a code-based approach makes controller design more flexible, simple and reliable. In fact, SC circuit needs no inductive element, so integrated circuit (IC) fabrication is promising for low-power VLSI applications. Here, an interleaved current-mode control is employed from battery interleaved charging to cell capacitors by two controlled current sources, so the continuous input current comes into being for lower EMI. Such a current-mode control possesses not only output robustness against source variation but also regulation capability of loading variation. Besides, the relevant theoretical analysis and control design are discussed, including conversion efficiency, lower bound of source, conversion ratio, ripple percentage, capacitance selection, closed-loop control and stability. Finally, the hardware experimental results are illustrated to show the efficacy of the CPLD-based converter.