Voltage controllers for DC-DC boost converters in discontinuous current mode

In this paper the performance of a non-isolated DC/DC boost converter is investigated during load variation since unexpected transients frequently happen in power systems. This boost converter is simulated in MATLAB/Simulink and the results are presented under different transient conditions. The simulation shows that the output voltage maintains in its desired value as long as the converter operates in continuous current mode operation. However, the system encounters the output voltage instability due to mode change from continuous to discontinuous current operation modes. Therefore, two distinct control methods are designed in order to maintain the output voltage in a constant desired value under the mode changing condition. First method is a closed-loop control with a pure integrator in the feedback path. The second one is the mode-change control method. This controller uses a calculating unit to find the proper duty ratio based on the value of the output current. In fact, this unit follows two different amounts of duty ratio for continuous and discontinuous modes. The results illustrate that the application of both controllers could properly control the output voltage and prevent its instability in discontinuous current operation modes. In addition, advantages and disadvantages of each method are presented and their comparison is discussed.