Lyapunov-based control strategy for power-factor preregulators

A new control strategy based on Lyapunov´s direct method is proposed for power-factor preregulators. It is shown that a globally stable control is possible at the expense of a time-varying reference function for the output voltage. Due to the practical difficulty and complexity in estimating the ripple component on the output voltage, a modified Lyapunov-based control method involving a constant reference for the output voltage is proposed. The method not only ensures stability independent of circuit parameters, but also exhibits excellent transient response to abrupt changes in the load. Moreover, it does not require any estimation technique to estimate the harmonic-ripple component of the output voltage. Computer and experimental results for continuous conduction mode operation are presented to show the applicability of the proposed control method.