Pole-zero analysis of supercapacitor-assisted low-dropout (SCALDO) regulator

Supercapacitor assisted low-dropout (SCALDO) regulator technique is gradually expanding as a novel approach to design high-efficiency, low-frequency DC-DC converters where the load sees a high-quality output of a linear regulator. Theoretical concepts, prototypes, and experimental validations of this patented technique have been well established and published in the past eight years. Further developing the SCALDO regulator's theoretical basis, the pole-zero analysis is presented in this paper. A basic background about the control loop, the open-loop transfer function, the poles and zeros of a PMOS LDO regulator are discussed here. The small-signal model of the overall SCALDO regulator is constructed using the supercapacitor circulation network and a discrete PMOS LDO regulator. With related to the small-signal model, the control loop, and the open-loop transfer function of the SCALDO regulator are derived. The results of the SCALDO regulator in terms of the DC gain, poles and zeros are compared with the PMOS LDO regulator. The theoretical analysis is validated using the simulated results obtained from the control system toolbox in MATLAB Simulink environment.