Abstract: A double integral indirect sliding mode control strategy was proposed for phase-shifted full-bridge (PSFB) DC-DC converters to improve the output performance. The theoretical analysis of motion of sliding mode controlled system was done according to Lie derivative method. The order reduction in the process of indirect sliding mode controlling was analyzed. The existence region of sliding mode and sliding motion were described in three-dimensional phase space. The selection basis of the sliding surface coefficients was given. Experimental results show that the proposed control strategy can improve the robustness and dynamic quality of PSFB， and eliminate state errors in the output， based on the fortes of sliding mode control.

Key words: phase-shifted full-bridge, indirect sliding mode control, double integral sliding mode control, robustness, Lie derivative