New digital control algorithms for high performance DC-to-DC converters

Due to the high power consuming characteristic of the next generation processors, the regulation requirement for power converter systems becomes more and more demanding in industry. Since it has the advantages of good programmability, flexibility and reliability, digital control system has the potential to achieve high performance control of DC-to-DC converters. The motivation of this research is to explore new digital control strategies for DC-to-DC converters to achieve high dynamic performance control. Four advanced digital control algorithms are explored in this thesis.; The first new digital control algorithm for DC-to-DC converter is current mode fuzzy logic controller (FLC). Using the inductor current feedback in FLC, the proposed algorithm combines the merits of current mode control and fuzzy control. Simulation and experimental results verify the effectiveness of the proposed method.; Secondly, extended state observer (ESO) is proposed to further improve the dynamic performance under load change. Based on nonlinear feedback, ESO can accurately estimate and compensate for the system external and internal disturbance, such as load change and parameter variation. Experimental results show that the proposed current mode FLC with ESO has improved the dynamic performance under load current change a lot and achieves the robustness to the system parameter variation.; To achieve the best possible transient performance of DC-to-DC converters under load current change, new digital optimal control algorithms are developed thirdly. The proposed optimal algorithms accurately predict the minimum number of switching cycles and their duty cycle values for the converter system to recover to the steady state when load current changes. Therefore, minimum overshoot/undershoot and shortest recovery time are achieved. Experimental results verify that the proposed optimal algorithms produce much better dynamic performance than the conventional current mode PID controller.; Finally, a new two-switching cycle compensation algorithm is proposed to generate the two-switching cycle duty cycle series to drive the converter to the steady state when input voltage changes. As a result, small overshoot/undershoot and short recovery time are achieved. Experimental results have proved that this algorithm has improved the dynamic performance under input voltage change a lot.