In order to simplify the selection of sliding coefficient of conventional sliding mode control switch converter

the relations among the sliding region

the sliding coefficient and the circuit parameters of Buck converter are analyzed and discussed.when inductor current is zero

according to the relationship between the systems trajectory and sliding region

an optimal design method for the sliding coefficient was proposed to ensure that under load variation

the switch converter enter the sliding region without the output voltage oscillation phenomena.Based on load variation scope

the optimal sliding coefficient is calculated directly.The simulation and experimental results verify the validity and feasibility of the optimal design method proposed.