Design and analysis of power-CMOS-gate-based switched-capacitor DC-DC converter with step-down and step-up modes

A unified multi-stage power-CMOS-transmission-gate-based quasi-switched-capacitor (QSC) DC-DC converter is proposed to integrate both step-down and step-up modes all in one circuit configuration for low-power applications. In this paper, by using power CMOS transmission gate as a bi-directional switch, the various topologies for step-down and step-up modes can be integrated in the same circuit configuration, and the configuration does not require any inductive elements, so the I.C. fabrication is promising for realization. In addition, both large-signal state-space equation and small-signal transfer function are derived by state-space averaging technique, and expressed all in one unified formulation for both modes. Based on the unified model, it is all presented for control design and theoretical analysis, including steady-state output and power, power efficiency, maximum voltage conversion ratio, maximum power efficiency, maximum output power, output voltage ripple percentage, capacitance selection, closed-loop control and stability, …etc. Finally, a multi-stage QSC DC-DC converter with step-down and step-up modes is made in circuit layout by PSPICE, and some topics are discussed, including (1) basic voltage conversion and output ripple percentage, (2) output robustness against source noises, (3) regulation capability of converter with loading variation. The simulated results are illustrated to show the efficacy of the unified configuration proposed.