This study describes a digitally controlled power factor correction (PFC) system based on two interleaved boost converters operating with pulsewidth modulation (PWM). Both converters are independently controlled by an inner control loop based on a discrete-time sliding-mode (SM) approach that imposes loss-free resistor (LFR) behavior on each cell. The switching surface implements an average current-mode controller so that the power factor (PF) is high. The SM-based digital controller is designed to operate at a constant switching frequency so that the interleaving technique, which is recommended for ac-dc power conversion systems higher than 1 kW, can be readily applied. An outer loop regulates the output voltage by means of a discrete-time proportional-integral (PI) compensator directly obtained from a discrete-time small-signal model of the ideal sliding dynamics. The control law proposed has been validated using numerical simulations and experimental results in a 2-kW prototype.

Digital implementation of sliding-mode current control applied to dc-dc switching converters is analyzed and developed in this paper. It is based on an interpolation predictive strategy that avoids problems associated to continuous sampling process of the controlled variable and minimizes quasi-sliding effects. In addition to inherent advantages of digital implementation, as programmability, flexibility, complex calculation capability and noise immunity, the proposed strategy maintains robustness and has similar behavior than analog sliding-mode current control implementations. In order to obtain output voltage regulation, an outer proportional-integral digital output voltage control loop is added. Simulated and experimental results in a boost converter are in good agreement with the theoretical predictions.

This paper deepens in the study of the recently described coupled-inductor buck-boost converter. The output voltage of this dc-dc converter can be regulated above and/or below its input voltage with high efficiency and wide bandwidth. The control of the input and/or output nonpulsating converter currents is addressed in this paper. The small-signal control-to-input/output-current transfer functions in open-loop permits the design of the respective average current-mode controllers. The combination of the input- and output-current controllers with an additional output voltage limiter loop is proposed as a method to regulate one of the currents while limiting the maximum values of the other two variables. The theoretical analyses have been validated by means of simulations and also experimentally on a 48-V 800-W purpose built-prototype. In particular, the frequency response measurements that have been carried out for a representative set of the converter operating points are in good agreement with the simulations.

The cascade connection of two dc–dc switching converters for constant power supply is studied. The source converter is of boost type while the load converter is of buck type. The natural unstable behaviour of the cascade connection for both on and off states of the boost converter is counteracted by a sliding‐mode control strategy that combines unstable trajectories to generate a stable one for the regulated boost converter dynamics. Experimental results using an electronic load to emulate a buck converter‐based constant power load are in good agreement with the theoretical predictions. A similar agreement is later obtained when a buck converter with a dynamic behaviour close to an instantaneous constant power load is employed instead of the electronic load.

A two-loop control method for a boost converter, which combines fuzzy and sliding-mode methodologies, is presented. An inner loop controls the inductor current through a sliding surface whose reference signal is given by a slower outer loop. This outer loop employs a fuzzy logic mechanism to implement a PI controller that guarantees output voltage regulation and results in an excellent transient response during start-up. The controller implementation requires standard analogue devices for the inner loop and an inexpensive 8-bit microcontroller for the outer loop. Experimental results are in good agreement with the theoretical predictions and show a better dynamic performance than those obtained by means of classical analogue two-loop techniques.

The application of the H/sub /spl infin// theory to control nonminimum phase dc-to-dc switching converters is investigated in this paper. Using an averaged linear model of the converter, a robust controller is developed, guaranteeing stability and the desired closed-loop dynamic response. Boost and buck-boost converters with H/sub /spl infin// control exhibit excellent performances with good tracking and high rejection capability of disturbances introduced by changes of load and input voltage by computer simulation. Experimental results are also obtained in a boost converter and compared with those obtained using current peak control and sliding-mode control.