Direct and Optimal Linear Active Methods for Stabilization of LC Input Filters and DC/DC Converters Under Voltage Mode Control

The switching mode power electronic converter with feedback loop control functions as a constant power load (CPL). CPLs have negative input impedance which may cause system instability. Both passive and active stabilization methods can solve this problem. However, active stabilization methods are more power efficient. Several active stabilization methods have been proposed for DC/AC inverter based CPLs. However, active stabilization methods for DC/DC converter based CPLs under voltage mode control have received little attention. In this paper, two linear active methods, the direct method and the optimal method, for the DC/DC buck converter under voltage mode control are proposed. In these two methods, feedforward loops are designed to modify the input impedance of the DC/DC converter to stabilize the system. Comparing with the direct method, the optimal method can achieve a shorter settling time and has smaller undesirable damped oscillation on the output voltage. Experimental results are reported to verify the effectiveness of these two methods.