A VCF-Step-Reconfigurable Continuously Scalable-Conversion-Ratio Switched-Capacitor Converter

This article proposes a
$V_{\rm CF}$
-step-reconfigurable continuously scalable-conversion-reconfigurable CSC (RCSC). We first analyze the working principle of the conventional conversion-ratio SC (CSC) converter and why it has reduced efficiency over a wide voltage conversion ratio (VCR) range. Then, the proposed RCSC reconfigures and thus equalizes the step size of the flying capacitor
$C_{\rm F}$
voltage (
$V_{\rm CF}$
) according to the VCR. This maximizes efficiency over a wider range of VCRs, with limited circuitry complexity. Subsequently, we propose a gate control signal generation scheme that significantly reduces the cost overhead of the reconfiguration. The proposed RCSC can be used in either step-up or step-down mode and is compatible with maximum power point tracking (MPPT) in energy harvesting systems. Implemented with a 65-nm CMOS process, the proposed RCSC reaches a 90% peak efficiency using 34
$V_{\rm CF}$
steps and the widest normalized VCR range with
$>$
75% efficiency.