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A disturbance observer-based control (DOBC) approach is proposed in this paper for control design and qualitative robustness analysis of PWM-based DC-DC buck power converters. A disturbance compensation gain is constructed for the composite control algorithm to cancel the unmatched uncertainties in the output voltage channel. Rigorous criterion is provided to show the quantitative robustness between controller parameters and circuit uncertainties. The DOBC approach delivers not only a promising disturbance rejection performance but also a superior property of tracking performance recovery. The feasibility and efficiency of the proposed approach is validated by experimental results based on LabVIEW real-time control test setup. [ABSTRACT FROM AUTHOR]

A maximum-power-point-tracking DC-DC boost converter to harvest energy from sub-\muW power sources is presented. For available input-power levels below 1 \muW, voltage boosting is achieved by operating all circuits in the sub-threshold region, and by switching the DC-DC converter at tens of Hz, thereby reducing switching losses. The paper further explores the possibility of energizing the DC-DC inductor for an optimum duration, such that switching and resistive losses are minimized. The sub-\muW energy harvesting circuit uses an area of 0.2 mm^2 on a standard 180 nm CMOS process, and utilizes an auxiliary voltage source for start-up. The designed and fabricated system is more than 50% efficient when the available power is greater than 2 \muW. The circuit can harvest energy whenever the available power is more than 0.3 \muW. Efficiency at 0.3 \muW is 25%, at 0.5 \muW is 37% and at 1 \muW is 48%. The complete IC consumes 50 nA for internal operations and the input voltage can be as low as 70 mV. [ABSTRACT FROM PUBLISHER]