Comparison of Step-Down Charge Pump Converters and Supercapacitor-Assisted Low- Dropout (SCALDO) Regulators

Abstract

The supercapacitor-assisted low-dropout (SCALDO) regulator is an extra-low frequency technique for designing high efficiency, low noise, step-down DC-DC converters with a supercapacitor (SC) energy circulation front-end in series with an LDO regulator. Due to the nature of the SC switching network at the front-end, one can tend to consider the SCALDO technique as a variation of a charge pump topology. The scope of this paper is to compare the major topological differences of the SCALDO regulator and the step-down charge pumps and hybrid-charge pump converters. The operation principles of conventional step-down switched-capacitor DC-DC converters are described, their limitations are identified, and the advantages of hybrid charge pump converters are also highlighted. Then, the SCALDO concept is discussed in detail. The topological differences of the SCALDO and charge pumps are identified, and the performance characteristics are compared concerning the output current driving capability, operating frequency, switching ripple, efficiency, power density, and complexity.