Self-excited power minimizer/maximizer for switching power converters

Abstract

In any steady-state optimization problem, the output being optimized could be a nonmonotonic function of the controlled variable. Often the output is dependent on the temperature, the load impedance, and other unknown and variable quantities. Thus, it is very useful to have an automatic tuning scheme that will take the system to the desired operating point using only input and output information. The present invention is a generalized tuning scheme that uses the correlation between changes in the input and corresponding changes in the output to tune the operating point. In general terms, the present invention utilizes a correlation function between the controlled variable and a perturbed waveform. When the system reaches the desired operating point, the correlation goes to zero and the system converges. This corresponds to the point at which the derivative of the output with respect to the input is zero. This tuning scheme is appropriate for any tuning problem which has a single maximum or minimum. A variety of tuning problems in power electronics and other areas fall into this category. A tuning scheme based on correlation usually requires an excitation input. The switching action in the controlled circuit perturbs all the states and provides this excitation. Thus, this tuning scheme is appropriate for switching power applications. A preferred embodiment of the present application is used to control a power converter in a solar array application.