Intelligent control of a switching power supply

Keywords: switching power supplies, DC-DC converters, PID controller, fuzzy control

A switching power supply is a DC-DC converter, which can transform DC voltages into a desired level with high efficiency. Because the dynamics of the system consisting of the power supply and the load is very fast, the commercial controllers have been realized by using analog components. Because these are not very flexible, there is a need to replace the analog solutions with computerized ones. For switching power supplies the study of voltage control by discrete and intelligent controllers is going on worldwide at this moment. Commercial solutions are not yet available.

In the current project possibilities of replacing the analog controller by a discrete algorithm are studied. A model of the power supply has been constructed in Matlab/Simulink environment, because this makes it possible to test the operation of the power supply and the controller. The model has been tested with Saber, which is an extensive commercial program package for modeling and simulation of electrical and mechanical systems. The model is validated by comparing simulation results to measurements obtained from a real switching power supply. A testbench for testing different intelligent algorithms is constructed by connecting a real DC-DC converter to a DSP processor card.

The performance of a standard PID algorithm is tested first both on voltage mode and current mode control of the power supply. The results are compared to those obtained by using a fuzzy controller, which has been designed with the software package FuzzyTech. Intelligent control algorithms are needed, because the real system to be controlled contains inherent nonlinearities (start-up mode, overload protection, complexities caused by rectifiers connected in parallel, batteries etc.), which are difficult to take into account by linear controllers. The goal of the project is to get a clear view of the possibility to replace the present-day analog solutions by intelligent discrete control algorithms in the switching power supplies of the next generation