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A closed-loop multistage (n -stage) multiphase (p -phase) switched-capacitor boost dc-ac inverter (MPSCI) is proposed by combining a variable-phase control (VPC) and sinusoidal pulsewidth-modulation (SPWM) technique for low-power step-up inversion/regulation. Its power stage contains two parts: an MPSC booster (front) and an H-bridge (rear). An n-stage p-phase MPSC is for an inductor-less boost dc-dc conversion, where n voltage doublers are in series for boosting voltage gain up to 2n at most. For improving efficiency, VPC is suggested to realize a variable multiphase operation by changing phase number p and topological path for more suitable gain level. An H-bridge is employed for dc-ac conversion, where four switches are controlled by SPWM not only for full-wave operation, but also for enhancing output regulation as well as robustness to source/loading variation. The analysis and design include an MPSCI model, steady-state/dynamic analysis, conversion ratio, power efficiency, stability, capacitance selection, total harmonic distortion (THD), filter, and control design. Finally, the closed-loop MPSCI is simulated, and the hardware is implemented and tested. All results are illustrated to show the efficacy of the proposed scheme.